For Model Helicopters Exotic Rotors both RC full-size helicopter design rotor head holds key improving flight performance Researchers continually searching ultimate design Part two EJames M Wang AS ANY helicopter flight engineer will tell main rotor sys tem important element both full-size model hel icopter design Thats because rotor system comprises rotor head blades has multiple control functions sub stantial impact flight dynamics professional work conduct research full-size helicop ter rotor systems Imagine trying design aircraft know ing fly themor least knowing fly RC coun terparts Its tantamount calling worlds best meat loaf cook vegetarian Experimenting RC Heli copter design spare time sharpens intuition analogous different problems encountered full-size chop pers Working out problems RC Heli copters great way predict new helicopter design will behave before crunch through complex theories computer first half two-part article de scribes several uncommon rotor heads Ive designed installation RC Heli copters Part two will discuss current re search project wind tunnel testing 1A.scale state-of-the-art bearingless rotor system future full-size applications Bearingless main rotors hottest topic todays helicopter community As re cently 1988 worlds first bearingless rotor-equipped helicopter introduced Germany MBB US researchers simple line drawing demonstrates four transmitter func tions can control six degrees freedom Helicopter 1 collective 2 pitch cyclic 3 roll cyclic 4 tail rotor thrust making effort stay competitive Four fundamental directional controls employed helicopter flight collec tive fore/aft cyclic roll cyclic head ing control determine helicopters degree freedom vertical pitch roll yaw functions respectively Since three out four essential controls origi nate main rotor careful rotor design paramount tailoring helicopter handling characteristics thrust generated main rotor keeps helicopter aloft deter mines directional control except heading governed tail ro tor pilot controls vertical up-and down motion varying amount main rotor thrust creates forward thrust tilting spinning rotor disc forward elicits right left movement tilt ing spinning disc desired direction tail rotor needed counteract torque generated main rotor vary ing tail rotor thrust pilot can control heading provides lift control well offering some damping restoring force craft rotating main rotor also makes helicopter inherently unsta ble Left unassisted helicopter will drift hover becoming slightly stable forward flight because aero dynamic damping produced horizon tal vertical fins Hence challenge helicopter designer overcome inherent instability caused main rotor Helicopter designers constantly strive improve aerodynamic stability control April 1990 85 Above The authors talthful GMP Cobra equipped testing rigid rotor assembly Right Close-up authors prototype rigid rotor head hub bolted solidly main rotor shaft prevent teetering object arrangement obtain almost instantaneous control power pilot feeds cyclic con trol tilt main rotor disc fuselage responds immediately Hingeless Bearingless TWIN C-SECTION FLEXBEAM BLAOE TORQUE TUBE PITCHLINK PIT Three major categories rotor head design redefining such design ele ments rotor stiffness blade inertia rpm shaft height blade chordwise center-ofgravity location blade airfoil blade diame LAG HINGEArticulated LAG OAMPER PUSHROOPITCH HORN FEATHER HINGE\fl/ E ATTACHMENT FLAP HINGE ROTOR/~ SHAFT Douglas Sikorsky either directly indirectly involved rotor head blade design testing Helicopter main rotor heads fall three major design categories articulated hingeless bearingless popular ro tor head design RC Helicopters two bladed teetering rotor head comprises other category entirely articulated rotor contains three sets ball bearings support rotor blades up/down flapping fore/aft leadlagging feathering pitch change mo tions Though theyre usually complicated heavy articulated rotors used exclu sively US -manufactured helicopters three- four-bladed heads Schluter Champion example artic ulated RC model rotor heads ter fuselage inertia others fullsize helicopter industry over third engineers employed such manufacturers Bell Boeing Kaman McDonnell86 Model Aviation Above The GMP Cobra flight authors prototype rigid rotor head installed Right authors friend Joe Medrano hold ing field frequency control board Joe expert sheet metal ist machined number rotor heads discussed article Left A later generation much precise rigid rojor neaa ae signed author flies much better earlier pro totype Above authors Cobra hovering new rigid rotor head Its very steady has superfast pitch roll response leaps out like guided missile Hot dog pilots will really enjoy hingeless rotor introduced 1970s equipped single set ball bearings used feathering up/down flapping fore/aft lead-lagging motions blade achieved either flexing nonrigid rotor hub flexing pliable root end rotor blade Advan tages hingeless rotor its minimal parts count fact aerodynam ically clean good control response Among full-size choppers type rotor Germanys MBB BO-105 Englands Westland Lynx Frances Aerospecial Ecureuil Hingeless rotors RC model Helicopters include 3OMX Kalt Baron K4-SB K3-SB ro tor heads Kalt Cyclone Baron 60 As mentioned already bearingless ro tor has sparked quite lot excitement world helicopter rotor design First developed 1980s rotor uses sup ple composite material called Flexbeam stead bearings Flapping lead-lagging feathering accomplished flex ing twisting Flexbeam Peka W Germany makes two- three- four- five-bladed bearingless main ro tor heads RC Helicopters Unfortu nately however no longer avail able US Both RC full-size bear ingless main rotor systems very difficult design properly Incorrect flexibility Left Close-up big teetering head design installed GMP Hind24 military drone nicknamed MF-1 monster chopper uses dumbbell weights instead Hiller paddles Since Bell control system lacks stabilizer damper Helicopter very stable has slow response isnt aerobatic Above Hinds designer John Gorham preparing lift off helicopter weighs 150 lb has 10-ft-dia rotors powered 350cc gasoline engine Above example Schiuter fixed-pitch S-head introduced Dieter Schluter back 1978 Its articulated ro tor flap hinge offset Right S-head installed authors Schluter Helibaby Hughes 500 body design pro vides much precise control response freely teetering two-bladed main rotor such used full-size Jet Ranger stiffness may result flutter problems ground air resonance reader wishes detailed comparison effects three types rotor heads RC Helicopter per formance referred article RC Ro tor Head Theory June 1989 issue Model Builder magazine article will improve understanding theory behind model Helicopter rotor system two-bladed teetering head design has distinct advantage RC Helicopter appli cations Most Helicopters equipped system because its very simple build set up teetering rotor head hub de signed pivot pin creating teeter ing motion blades inspired its name design will work two bladed system addition RC Helicopter Left Hirobos DDF Dual Dampened Flapping rotor head GMP Stork DDF combines features teetering rotor head articulated flap hinge offset entire hub can teeter about center pin rotor can flap up down individually installation flybar removed experiment didnt work out Right photo shows authors four-bladed hingeless rotor made stacking two Kalt Baron 30 rotor heads setup flies quite well Use two Kalt K4-SB heads 40- 60-size Helicopters April 1990 87 models full-size Bell Jet Ranger UH-l Huey Cobra Gunship feature two bladed teetering rotor designs variation teetering rotor head rigid rotor design hub bolted solidly main rotor shaft pre vent teetering very few full-size helicopters equipped rigid rotor head Lockheed 286 aircraft never reached production stage rigid rotor has advantage su perb almost instantaneous control power pilot feeds cyclic control tilt main rotor disc fuselage re sponds immediately contrast teeter ing rotor gives sluggish cyclic control Since its main rotor disc can tilt re spect main rotor shaft no direct pitch roll moment transferred main rotor fuselage Model Helicopters have overcome problem employing rubber damper 0-ring inside teetering hub As hub teeters rubber functions like spring transmit rotor tilt moment pitch roll fuselage permits RC Helicop ters fancy aerobatics full-size helicopters cannot rubber damper made sufficiently stiff teetering head will behave like rigid rotor head As pilot com presses damper Helicopter re sponds quickly However vibration increases well since its transferred di rectly through hub shaft fuse lage can have adverse effect receiver servos Two originaldesign rigid rotor heads shown some illustra tions Tested GMP Cobra provided su perfast control uncanny imita tion its veno mous namesake Cobra hovers sol idly until re ceives control command leaps out like guided missile Pilots enjoy hot-dogging will probably have fun rigid rotor Just sure youre ballthis machine has raw power F-16 prototype rigid rotor design made cutting GMP Custom head two halves coupling ma chined aluminum hub hub fits tightly over 10mm main rotor shaft However feathering axis two blades must exact alignment found difficult achieve proto type rigid rotor slightest imperfec tion such misalignment being out track imbalance will cause serious vi bration second rigid rotor hub pre cisely machined lathe avoid misalign ment Installed Cobra rotor head eliminated vibration entirely Heli copter flew superbly Although Cobra hovers very well rigid rotor system tends nose up quite severely forward flight Note both rotor heads flybarless creasing blade size 135 grams 160 grams would probably mitigate nose-up tendency Note also GMP flybarless Legend doesnt share nose-up tendency Its stiff-teetering head prevents gust-induced rotor flapback being transmitted fuselage frankly much prefer flying Legend rigid-rotor Cobra Perhaps Im cut out F-16 type flying However mounting set flexible blades Co bra would probably improve its flight per formance considerably blades functioning like stiff hingeless rotor / BO-105 hingeless hub fiberglass blades produced WIK Modelle Germany Intro duced 1970s hingeless rotor equipped single set ball bearings used feathering Major advan tages design minimal parts count its aerodynamically clean profile Cobra should fly better Helicop ters full-size MBB BO-lOS illustrates concept Though has rigid titanium hub four flexible fiberglass blades provide flapping flexibility works better teetering rotor head because theres no teetering slop dead-band teetering pin/roller bearing location Wik Modelle Products West Germany makes Scale BO-lOS rigid hub very flexible fiberglass blades RC Helicop ters understand currently im ported US firm plan try unit publish results GMP Hind-24 drone Helicopter seen two pictures equipped big teetering rotor head Nicknamed MF- 1 chopper uses dumbbell weights instead Continued page 183 88 Model Aviation four-bladed rigid tail rotor hub plate provides excellent tail thrust control unit marketed Victor Dziabczenko David Grabski around $100 Call either detailed technical price information 1-818/341-2159 1 -805/296-0860 Above authors original-design bearingless main rotor head Torlon flex beam incorporated design provides bend ing torsion functions Torlon petroleum-based synthetic prod uct has properties steel costs about 100 times Right aluminum post shown along Torlon flex beams can attached top head support flybar ahilizer achieve smooth level power slight indication turn l turned large left circles power glide mode Gradually increase run time use mall pieces clay weight nose tail r either wing tip achieve perfect light path possible youre com letely satisfied install 5- 6-in-dia lastic prop increase charge time little power needed try 7-inha Peck-Polymers plastic prop trimmed powered properly Falcon will climb very slow re distic rate wide circles 1 /2 ninutes cruise its maximum alti ude short before descending low wide circles gentle landings aIm day near-maximum charges ThE WIlQMATEKTM rhe extra large handle bends 1/8-1/4 coils Si 32-3I1& music wire Wire creep eliminated ur ANTI-KREEP WIRE LOCKIN free catalog also has hardware accessories JOM COMPANY 114 WashIngton Terr Dept Waukegan IL 60085 1st US RIC Flight School Stop Crashing Start Learning CLASSES FILLING FAST Info pack $200 1st US R/C FLIGHT SCHOOL 521 S Sawyer. Shawano WI 54166 t7151 524-2985 Hiller paddles Since Bell control sys tem lacks stabilizer damper Helicop ter stable aerobatic flight 150 lb powered 350cc gasoline en gine very large Helicopter dont want get anywhere near 10-ftdia main rotor MF-l uses 60-size Competitor main rotor blades tail blades Notice pictures Schluter fixedpitch S-head S-head Schluter Helibaby Hughes 500 body system introduced Mr Schluter back 1978 Its two-bladed ar ticulated rotor flap hinge offset confused teetering head rotor Flap hinge offset provides better control re sponse freely teetering two-bladed main rotor such used full-size Jet Ranger Kyoshos new Concept 30 ex ample collective-pitch Helicopter two-bladed flap hinge offset articulated main rotor Another picture shows Hirobos DDF Dual Dampened Flapping head GMP Stork DDF combines features teetering rotor head artic ulated flap hinge offset entire hub can teeter about center pin ro tor blade can flap up down individually result softnesss makes very stable flight characteristics original Hirobo Shuttle introduced 1985 also individual blade flapping design However flapping head overly soft excellent ginners also caused blades strike tail boom hard landings Hirobo rec ognized problem has equipped its Shuttles since 1987 floating axle design similar found Schluter Champion Miniature Aircraft X Cell new head Shuttle both stable aerobatic experiment removed stabi lizer bar assembly see Stork would perform flybarless Helicopter April 1990 183 model will turn breathtaking flights over two minutes glide may resem ble Wakefield Free Flighter can sniff out thermals tempted After Falcon Heli Rotors/Wang Continued page 88 VENO MOUNTS TNE VIBRATION lOLLER Fad end fuel pOaf flee axes ieoiefan fa 25 Ia f 20 an0nea ea-txau F S al S Uslia f ieaalf engfle nouffe Typaai aibfefran reduCtIOn 70% Ma 80% Oft kit COnSIStS OfOuntt isolate Ina pointS seoond 1~~ weetra, iubna jnSfuOtlOnS Sena Sf200 CheCk O Inane OldOt Fe kif OAA PRODUCTS P0 SOS aReas SARASOTA FL 342S3 Sf33774252 FL residents add 72 Caret tax IRFORMATION eand SASS Bob Fiorenzej Hobby Center Inc Dealer Yellow AircraftJLE UPS Orders Shipped Daily Now Available Faatcove coasting Mate,al Visit Showroom 35 win D sney Watidi NEW custow Building Sern Ce 420 WesO SR 434407 327-6383 Winter Springs FL 32708Fax 407 327-7148 3 New ARFs ZMP MONARCH AMA Sport Pattern span 66 area 750 sq motor 4 stroke 90 60 cu Preassembled balsa fuselage vdneered wing shaped balsa pail Lesan canopy epoxy cowl illustrated assembly manual c ZIMPRO MARKETING Pu suuJoltouKxIoGtTS3PSJO PiJOSE 51 axstex found didnt fly well rea son Extra damping quick control re sponse needed tame RC Helicopters much difficult fly full-size counterparts flybarless RC Helicopters depend stiff main rotor head improve vehicles pitch roll damping control power four-bladed hingeless head shown pictures made stacking two Baron 3OMX two-bladed hingeless heads result similar full-size Westland Lynx rotor head steel flexbeam hub gives comparable flap flexibil ity other type hingeless head BO-105 made MBB acquires its flap flexibility through fiberglass blades Wik Modelle also produces BO-105 hingeless hub blades As heads better depends whether youre talk ing Germans British original-design bearingless rotor head uses flexbeam provide bending torsion Its machined special petroleum-based synthetic called Torlon Manufactured Amoco Petroleum Prod ucts Torlon has properties steel costs about 100 times 2-ft-sq piece sells around $700 aluminum post can added top head support flybar shown pic tures friend Joe Medrano expert sheet metalist machined number rotor Sachs Doimar Engines New Torque Customized TG Only 100% SACHS Engine 27All Engines Complete $360 NNothing Buy 31See us 100 TOLEDO Show *40000 37 *43000 42 $46000 add $50 throttlecoupled spark advance Along 27 8 32 lightweight spring start flywheel-type Sachs Dolmar Engine TG MFG 201427-3845 857 HIgh Mtn Rd N Haledon NJ 07508 heads shown photos stamped own Cobra side frames welded rear exhaust muffler Thank Joe Next months sequel will present -scale four-bladed bearingless model ro tor tested Glenn L Martin wind tun nel University Maryland Along million-dollar tunnel youll see some exotic blades swashplates miniature hydraulic servo actuators control sys tems Consortium/Hunt Continued page 104 slight down elevator pick up hold some speed chasing next thermal Ron Farkas built model Ep pIer 201 airfoil its higher weight 3 oz heavier thinner wing version flies just well higher speed Oth ers made Clark Y RAF 32 Ep pIer 193 airfoils scheduled flown soon after article submitted As builder get bored very easily same old construction techniques same old low-wing sport high-wing trainer airplanes Im hobby learn well have fun certainly did both designing Consortium hope reading about project has acquaint ed some new techniques build ing designing model airplanes youve got urge try something differentand little time spend workshopthis classy-looking good-per forming Sailplane will give lot fun small flying field RC Soaring/Blakeslee Continued page 43 museum its displays programs will knock out Make effort joinor visit join t guarantee youll regret either address National Soaring Museum RD#3 Har ris Hill Elmira NY 14903 Thanks Cal Weiss taking time tell us about NSM Im sure model Glider fliers appreciate learning about will plan stop area tn cover letter Cal mentioned tht photos prt vided Shirley Sliwa Director NSM C also passed along personal information am retired NASA Lewis Researe Center Cleveland last 22 3 years directed work Educ tional Services Office Several notable moc elers Chet Lanzo Warren Plohr Reich brothers see Warren occasion club fieldI am member America Airlines Model Club Chet course just rc cently passed away Way back membe Board NAR along John Worth kind establishes Ive fiel bit time fact know few real pros should add fly almost week Jo Elgin designer Playboy makes no bet ter flier models t have active witl RC Gliders five years am having ball managed 1 hr. 15 mm flight oh Windrifter summer Lord t t did kept pulling up kept trying keep sight reasonable alti tude tm interested areas aviation top soaring tt has always fascinated mt just because beauty carries over intc modeling Scale look beauty RC Sailplane much like real thing anything dont like its beautiful Seal model Cub flies what appears super sonic speeds wife also loves sailplanes ant together have attended several Nationals ant regional contests spectators fact las visit museum dedication thi same time Region 3 contest Harris Hill 1 guess natural believi other Sailplane modelers also interested thi full-size ones museum Its reasot put article together Perhaps some mod elers within reach museum will make ths effort visit live too far away perhaps article will interest may wish become members event atr turned want pass information tc others International Postal Challenge Old-time readers column will remember previous re ports Kale Harden Palm Harbor FL IPC idea behind postal contest club several countries fly same contest same day compare results mail sure its interesting fun-fly con cept way meet Sailplaners other countries Kale Pelicans Club St Pete sent reContinued page J& 184 Model Aviation Special Introductory Offer SUKHOI Su-26M15 ScaleIMPALA Masters Pattern span 68 area 890 sq motor 4 stroke 120 equivspan 68 area 800 sq motor 4 stroke 120 60 rear Preassembled lightweight epoxy fuselage sheeted plug-in wingsPreassembled balsa fusefage veneered plug-in wings & stabs sheeted stab fin & rudder 8 dia epoxy cowl Lexan canopy &Epoxy cowl pipe cover removable canopy Illustrated illustrated assembly manualassembly manual see hobby dealer order direct
Edition: Model Aviation - 1990/04
Page Numbers: 85, 86, 87, 88, 183, 184
For Model Helicopters Exotic Rotors both RC full-size helicopter design rotor head holds key improving flight performance Researchers continually searching ultimate design Part two EJames M Wang AS ANY helicopter flight engineer will tell main rotor sys tem important element both full-size model hel icopter design Thats because rotor system comprises rotor head blades has multiple control functions sub stantial impact flight dynamics professional work conduct research full-size helicop ter rotor systems Imagine trying design aircraft know ing fly themor least knowing fly RC coun terparts Its tantamount calling worlds best meat loaf cook vegetarian Experimenting RC Heli copter design spare time sharpens intuition analogous different problems encountered full-size chop pers Working out problems RC Heli copters great way predict new helicopter design will behave before crunch through complex theories computer first half two-part article de scribes several uncommon rotor heads Ive designed installation RC Heli copters Part two will discuss current re search project wind tunnel testing 1A.scale state-of-the-art bearingless rotor system future full-size applications Bearingless main rotors hottest topic todays helicopter community As re cently 1988 worlds first bearingless rotor-equipped helicopter introduced Germany MBB US researchers simple line drawing demonstrates four transmitter func tions can control six degrees freedom Helicopter 1 collective 2 pitch cyclic 3 roll cyclic 4 tail rotor thrust making effort stay competitive Four fundamental directional controls employed helicopter flight collec tive fore/aft cyclic roll cyclic head ing control determine helicopters degree freedom vertical pitch roll yaw functions respectively Since three out four essential controls origi nate main rotor careful rotor design paramount tailoring helicopter handling characteristics thrust generated main rotor keeps helicopter aloft deter mines directional control except heading governed tail ro tor pilot controls vertical up-and down motion varying amount main rotor thrust creates forward thrust tilting spinning rotor disc forward elicits right left movement tilt ing spinning disc desired direction tail rotor needed counteract torque generated main rotor vary ing tail rotor thrust pilot can control heading provides lift control well offering some damping restoring force craft rotating main rotor also makes helicopter inherently unsta ble Left unassisted helicopter will drift hover becoming slightly stable forward flight because aero dynamic damping produced horizon tal vertical fins Hence challenge helicopter designer overcome inherent instability caused main rotor Helicopter designers constantly strive improve aerodynamic stability control April 1990 85 Above The authors talthful GMP Cobra equipped testing rigid rotor assembly Right Close-up authors prototype rigid rotor head hub bolted solidly main rotor shaft prevent teetering object arrangement obtain almost instantaneous control power pilot feeds cyclic con trol tilt main rotor disc fuselage responds immediately Hingeless Bearingless TWIN C-SECTION FLEXBEAM BLAOE TORQUE TUBE PITCHLINK PIT Three major categories rotor head design redefining such design ele ments rotor stiffness blade inertia rpm shaft height blade chordwise center-ofgravity location blade airfoil blade diame LAG HINGEArticulated LAG OAMPER PUSHROOPITCH HORN FEATHER HINGE\fl/ E ATTACHMENT FLAP HINGE ROTOR/~ SHAFT Douglas Sikorsky either directly indirectly involved rotor head blade design testing Helicopter main rotor heads fall three major design categories articulated hingeless bearingless popular ro tor head design RC Helicopters two bladed teetering rotor head comprises other category entirely articulated rotor contains three sets ball bearings support rotor blades up/down flapping fore/aft leadlagging feathering pitch change mo tions Though theyre usually complicated heavy articulated rotors used exclu sively US -manufactured helicopters three- four-bladed heads Schluter Champion example artic ulated RC model rotor heads ter fuselage inertia others fullsize helicopter industry over third engineers employed such manufacturers Bell Boeing Kaman McDonnell86 Model Aviation Above The GMP Cobra flight authors prototype rigid rotor head installed Right authors friend Joe Medrano hold ing field frequency control board Joe expert sheet metal ist machined number rotor heads discussed article Left A later generation much precise rigid rojor neaa ae signed author flies much better earlier pro totype Above authors Cobra hovering new rigid rotor head Its very steady has superfast pitch roll response leaps out like guided missile Hot dog pilots will really enjoy hingeless rotor introduced 1970s equipped single set ball bearings used feathering up/down flapping fore/aft lead-lagging motions blade achieved either flexing nonrigid rotor hub flexing pliable root end rotor blade Advan tages hingeless rotor its minimal parts count fact aerodynam ically clean good control response Among full-size choppers type rotor Germanys MBB BO-105 Englands Westland Lynx Frances Aerospecial Ecureuil Hingeless rotors RC model Helicopters include 3OMX Kalt Baron K4-SB K3-SB ro tor heads Kalt Cyclone Baron 60 As mentioned already bearingless ro tor has sparked quite lot excitement world helicopter rotor design First developed 1980s rotor uses sup ple composite material called Flexbeam stead bearings Flapping lead-lagging feathering accomplished flex ing twisting Flexbeam Peka W Germany makes two- three- four- five-bladed bearingless main ro tor heads RC Helicopters Unfortu nately however no longer avail able US Both RC full-size bear ingless main rotor systems very difficult design properly Incorrect flexibility Left Close-up big teetering head design installed GMP Hind24 military drone nicknamed MF-1 monster chopper uses dumbbell weights instead Hiller paddles Since Bell control system lacks stabilizer damper Helicopter very stable has slow response isnt aerobatic Above Hinds designer John Gorham preparing lift off helicopter weighs 150 lb has 10-ft-dia rotors powered 350cc gasoline engine Above example Schiuter fixed-pitch S-head introduced Dieter Schluter back 1978 Its articulated ro tor flap hinge offset Right S-head installed authors Schluter Helibaby Hughes 500 body design pro vides much precise control response freely teetering two-bladed main rotor such used full-size Jet Ranger stiffness may result flutter problems ground air resonance reader wishes detailed comparison effects three types rotor heads RC Helicopter per formance referred article RC Ro tor Head Theory June 1989 issue Model Builder magazine article will improve understanding theory behind model Helicopter rotor system two-bladed teetering head design has distinct advantage RC Helicopter appli cations Most Helicopters equipped system because its very simple build set up teetering rotor head hub de signed pivot pin creating teeter ing motion blades inspired its name design will work two bladed system addition RC Helicopter Left Hirobos DDF Dual Dampened Flapping rotor head GMP Stork DDF combines features teetering rotor head articulated flap hinge offset entire hub can teeter about center pin rotor can flap up down individually installation flybar removed experiment didnt work out Right photo shows authors four-bladed hingeless rotor made stacking two Kalt Baron 30 rotor heads setup flies quite well Use two Kalt K4-SB heads 40- 60-size Helicopters April 1990 87 models full-size Bell Jet Ranger UH-l Huey Cobra Gunship feature two bladed teetering rotor designs variation teetering rotor head rigid rotor design hub bolted solidly main rotor shaft pre vent teetering very few full-size helicopters equipped rigid rotor head Lockheed 286 aircraft never reached production stage rigid rotor has advantage su perb almost instantaneous control power pilot feeds cyclic control tilt main rotor disc fuselage re sponds immediately contrast teeter ing rotor gives sluggish cyclic control Since its main rotor disc can tilt re spect main rotor shaft no direct pitch roll moment transferred main rotor fuselage Model Helicopters have overcome problem employing rubber damper 0-ring inside teetering hub As hub teeters rubber functions like spring transmit rotor tilt moment pitch roll fuselage permits RC Helicop ters fancy aerobatics full-size helicopters cannot rubber damper made sufficiently stiff teetering head will behave like rigid rotor head As pilot com presses damper Helicopter re sponds quickly However vibration increases well since its transferred di rectly through hub shaft fuse lage can have adverse effect receiver servos Two originaldesign rigid rotor heads shown some illustra tions Tested GMP Cobra provided su perfast control uncanny imita tion its veno mous namesake Cobra hovers sol idly until re ceives control command leaps out like guided missile Pilots enjoy hot-dogging will probably have fun rigid rotor Just sure youre ballthis machine has raw power F-16 prototype rigid rotor design made cutting GMP Custom head two halves coupling ma chined aluminum hub hub fits tightly over 10mm main rotor shaft However feathering axis two blades must exact alignment found difficult achieve proto type rigid rotor slightest imperfec tion such misalignment being out track imbalance will cause serious vi bration second rigid rotor hub pre cisely machined lathe avoid misalign ment Installed Cobra rotor head eliminated vibration entirely Heli copter flew superbly Although Cobra hovers very well rigid rotor system tends nose up quite severely forward flight Note both rotor heads flybarless creasing blade size 135 grams 160 grams would probably mitigate nose-up tendency Note also GMP flybarless Legend doesnt share nose-up tendency Its stiff-teetering head prevents gust-induced rotor flapback being transmitted fuselage frankly much prefer flying Legend rigid-rotor Cobra Perhaps Im cut out F-16 type flying However mounting set flexible blades Co bra would probably improve its flight per formance considerably blades functioning like stiff hingeless rotor / BO-105 hingeless hub fiberglass blades produced WIK Modelle Germany Intro duced 1970s hingeless rotor equipped single set ball bearings used feathering Major advan tages design minimal parts count its aerodynamically clean profile Cobra should fly better Helicop ters full-size MBB BO-lOS illustrates concept Though has rigid titanium hub four flexible fiberglass blades provide flapping flexibility works better teetering rotor head because theres no teetering slop dead-band teetering pin/roller bearing location Wik Modelle Products West Germany makes Scale BO-lOS rigid hub very flexible fiberglass blades RC Helicop ters understand currently im ported US firm plan try unit publish results GMP Hind-24 drone Helicopter seen two pictures equipped big teetering rotor head Nicknamed MF- 1 chopper uses dumbbell weights instead Continued page 183 88 Model Aviation four-bladed rigid tail rotor hub plate provides excellent tail thrust control unit marketed Victor Dziabczenko David Grabski around $100 Call either detailed technical price information 1-818/341-2159 1 -805/296-0860 Above authors original-design bearingless main rotor head Torlon flex beam incorporated design provides bend ing torsion functions Torlon petroleum-based synthetic prod uct has properties steel costs about 100 times Right aluminum post shown along Torlon flex beams can attached top head support flybar ahilizer achieve smooth level power slight indication turn l turned large left circles power glide mode Gradually increase run time use mall pieces clay weight nose tail r either wing tip achieve perfect light path possible youre com letely satisfied install 5- 6-in-dia lastic prop increase charge time little power needed try 7-inha Peck-Polymers plastic prop trimmed powered properly Falcon will climb very slow re distic rate wide circles 1 /2 ninutes cruise its maximum alti ude short before descending low wide circles gentle landings aIm day near-maximum charges ThE WIlQMATEKTM rhe extra large handle bends 1/8-1/4 coils Si 32-3I1& music wire Wire creep eliminated ur ANTI-KREEP WIRE LOCKIN free catalog also has hardware accessories JOM COMPANY 114 WashIngton Terr Dept Waukegan IL 60085 1st US RIC Flight School Stop Crashing Start Learning CLASSES FILLING FAST Info pack $200 1st US R/C FLIGHT SCHOOL 521 S Sawyer. Shawano WI 54166 t7151 524-2985 Hiller paddles Since Bell control sys tem lacks stabilizer damper Helicop ter stable aerobatic flight 150 lb powered 350cc gasoline en gine very large Helicopter dont want get anywhere near 10-ftdia main rotor MF-l uses 60-size Competitor main rotor blades tail blades Notice pictures Schluter fixedpitch S-head S-head Schluter Helibaby Hughes 500 body system introduced Mr Schluter back 1978 Its two-bladed ar ticulated rotor flap hinge offset confused teetering head rotor Flap hinge offset provides better control re sponse freely teetering two-bladed main rotor such used full-size Jet Ranger Kyoshos new Concept 30 ex ample collective-pitch Helicopter two-bladed flap hinge offset articulated main rotor Another picture shows Hirobos DDF Dual Dampened Flapping head GMP Stork DDF combines features teetering rotor head artic ulated flap hinge offset entire hub can teeter about center pin ro tor blade can flap up down individually result softnesss makes very stable flight characteristics original Hirobo Shuttle introduced 1985 also individual blade flapping design However flapping head overly soft excellent ginners also caused blades strike tail boom hard landings Hirobo rec ognized problem has equipped its Shuttles since 1987 floating axle design similar found Schluter Champion Miniature Aircraft X Cell new head Shuttle both stable aerobatic experiment removed stabi lizer bar assembly see Stork would perform flybarless Helicopter April 1990 183 model will turn breathtaking flights over two minutes glide may resem ble Wakefield Free Flighter can sniff out thermals tempted After Falcon Heli Rotors/Wang Continued page 88 VENO MOUNTS TNE VIBRATION lOLLER Fad end fuel pOaf flee axes ieoiefan fa 25 Ia f 20 an0nea ea-txau F S al S Uslia f ieaalf engfle nouffe Typaai aibfefran reduCtIOn 70% Ma 80% Oft kit COnSIStS OfOuntt isolate Ina pointS seoond 1~~ weetra, iubna jnSfuOtlOnS Sena Sf200 CheCk O Inane OldOt Fe kif OAA PRODUCTS P0 SOS aReas SARASOTA FL 342S3 Sf33774252 FL residents add 72 Caret tax IRFORMATION eand SASS Bob Fiorenzej Hobby Center Inc Dealer Yellow AircraftJLE UPS Orders Shipped Daily Now Available Faatcove coasting Mate,al Visit Showroom 35 win D sney Watidi NEW custow Building Sern Ce 420 WesO SR 434407 327-6383 Winter Springs FL 32708Fax 407 327-7148 3 New ARFs ZMP MONARCH AMA Sport Pattern span 66 area 750 sq motor 4 stroke 90 60 cu Preassembled balsa fuselage vdneered wing shaped balsa pail Lesan canopy epoxy cowl illustrated assembly manual c ZIMPRO MARKETING Pu suuJoltouKxIoGtTS3PSJO PiJOSE 51 axstex found didnt fly well rea son Extra damping quick control re sponse needed tame RC Helicopters much difficult fly full-size counterparts flybarless RC Helicopters depend stiff main rotor head improve vehicles pitch roll damping control power four-bladed hingeless head shown pictures made stacking two Baron 3OMX two-bladed hingeless heads result similar full-size Westland Lynx rotor head steel flexbeam hub gives comparable flap flexibil ity other type hingeless head BO-105 made MBB acquires its flap flexibility through fiberglass blades Wik Modelle also produces BO-105 hingeless hub blades As heads better depends whether youre talk ing Germans British original-design bearingless rotor head uses flexbeam provide bending torsion Its machined special petroleum-based synthetic called Torlon Manufactured Amoco Petroleum Prod ucts Torlon has properties steel costs about 100 times 2-ft-sq piece sells around $700 aluminum post can added top head support flybar shown pic tures friend Joe Medrano expert sheet metalist machined number rotor Sachs Doimar Engines New Torque Customized TG Only 100% SACHS Engine 27All Engines Complete $360 NNothing Buy 31See us 100 TOLEDO Show *40000 37 *43000 42 $46000 add $50 throttlecoupled spark advance Along 27 8 32 lightweight spring start flywheel-type Sachs Dolmar Engine TG MFG 201427-3845 857 HIgh Mtn Rd N Haledon NJ 07508 heads shown photos stamped own Cobra side frames welded rear exhaust muffler Thank Joe Next months sequel will present -scale four-bladed bearingless model ro tor tested Glenn L Martin wind tun nel University Maryland Along million-dollar tunnel youll see some exotic blades swashplates miniature hydraulic servo actuators control sys tems Consortium/Hunt Continued page 104 slight down elevator pick up hold some speed chasing next thermal Ron Farkas built model Ep pIer 201 airfoil its higher weight 3 oz heavier thinner wing version flies just well higher speed Oth ers made Clark Y RAF 32 Ep pIer 193 airfoils scheduled flown soon after article submitted As builder get bored very easily same old construction techniques same old low-wing sport high-wing trainer airplanes Im hobby learn well have fun certainly did both designing Consortium hope reading about project has acquaint ed some new techniques build ing designing model airplanes youve got urge try something differentand little time spend workshopthis classy-looking good-per forming Sailplane will give lot fun small flying field RC Soaring/Blakeslee Continued page 43 museum its displays programs will knock out Make effort joinor visit join t guarantee youll regret either address National Soaring Museum RD#3 Har ris Hill Elmira NY 14903 Thanks Cal Weiss taking time tell us about NSM Im sure model Glider fliers appreciate learning about will plan stop area tn cover letter Cal mentioned tht photos prt vided Shirley Sliwa Director NSM C also passed along personal information am retired NASA Lewis Researe Center Cleveland last 22 3 years directed work Educ tional Services Office Several notable moc elers Chet Lanzo Warren Plohr Reich brothers see Warren occasion club fieldI am member America Airlines Model Club Chet course just rc cently passed away Way back membe Board NAR along John Worth kind establishes Ive fiel bit time fact know few real pros should add fly almost week Jo Elgin designer Playboy makes no bet ter flier models t have active witl RC Gliders five years am having ball managed 1 hr. 15 mm flight oh Windrifter summer Lord t t did kept pulling up kept trying keep sight reasonable alti tude tm interested areas aviation top soaring tt has always fascinated mt just because beauty carries over intc modeling Scale look beauty RC Sailplane much like real thing anything dont like its beautiful Seal model Cub flies what appears super sonic speeds wife also loves sailplanes ant together have attended several Nationals ant regional contests spectators fact las visit museum dedication thi same time Region 3 contest Harris Hill 1 guess natural believi other Sailplane modelers also interested thi full-size ones museum Its reasot put article together Perhaps some mod elers within reach museum will make ths effort visit live too far away perhaps article will interest may wish become members event atr turned want pass information tc others International Postal Challenge Old-time readers column will remember previous re ports Kale Harden Palm Harbor FL IPC idea behind postal contest club several countries fly same contest same day compare results mail sure its interesting fun-fly con cept way meet Sailplaners other countries Kale Pelicans Club St Pete sent reContinued page J& 184 Model Aviation Special Introductory Offer SUKHOI Su-26M15 ScaleIMPALA Masters Pattern span 68 area 890 sq motor 4 stroke 120 equivspan 68 area 800 sq motor 4 stroke 120 60 rear Preassembled lightweight epoxy fuselage sheeted plug-in wingsPreassembled balsa fusefage veneered plug-in wings & stabs sheeted stab fin & rudder 8 dia epoxy cowl Lexan canopy &Epoxy cowl pipe cover removable canopy Illustrated illustrated assembly manualassembly manual see hobby dealer order direct
Edition: Model Aviation - 1990/04
Page Numbers: 85, 86, 87, 88, 183, 184
For Model Helicopters Exotic Rotors both RC full-size helicopter design rotor head holds key improving flight performance Researchers continually searching ultimate design Part two EJames M Wang AS ANY helicopter flight engineer will tell main rotor sys tem important element both full-size model hel icopter design Thats because rotor system comprises rotor head blades has multiple control functions sub stantial impact flight dynamics professional work conduct research full-size helicop ter rotor systems Imagine trying design aircraft know ing fly themor least knowing fly RC coun terparts Its tantamount calling worlds best meat loaf cook vegetarian Experimenting RC Heli copter design spare time sharpens intuition analogous different problems encountered full-size chop pers Working out problems RC Heli copters great way predict new helicopter design will behave before crunch through complex theories computer first half two-part article de scribes several uncommon rotor heads Ive designed installation RC Heli copters Part two will discuss current re search project wind tunnel testing 1A.scale state-of-the-art bearingless rotor system future full-size applications Bearingless main rotors hottest topic todays helicopter community As re cently 1988 worlds first bearingless rotor-equipped helicopter introduced Germany MBB US researchers simple line drawing demonstrates four transmitter func tions can control six degrees freedom Helicopter 1 collective 2 pitch cyclic 3 roll cyclic 4 tail rotor thrust making effort stay competitive Four fundamental directional controls employed helicopter flight collec tive fore/aft cyclic roll cyclic head ing control determine helicopters degree freedom vertical pitch roll yaw functions respectively Since three out four essential controls origi nate main rotor careful rotor design paramount tailoring helicopter handling characteristics thrust generated main rotor keeps helicopter aloft deter mines directional control except heading governed tail ro tor pilot controls vertical up-and down motion varying amount main rotor thrust creates forward thrust tilting spinning rotor disc forward elicits right left movement tilt ing spinning disc desired direction tail rotor needed counteract torque generated main rotor vary ing tail rotor thrust pilot can control heading provides lift control well offering some damping restoring force craft rotating main rotor also makes helicopter inherently unsta ble Left unassisted helicopter will drift hover becoming slightly stable forward flight because aero dynamic damping produced horizon tal vertical fins Hence challenge helicopter designer overcome inherent instability caused main rotor Helicopter designers constantly strive improve aerodynamic stability control April 1990 85 Above The authors talthful GMP Cobra equipped testing rigid rotor assembly Right Close-up authors prototype rigid rotor head hub bolted solidly main rotor shaft prevent teetering object arrangement obtain almost instantaneous control power pilot feeds cyclic con trol tilt main rotor disc fuselage responds immediately Hingeless Bearingless TWIN C-SECTION FLEXBEAM BLAOE TORQUE TUBE PITCHLINK PIT Three major categories rotor head design redefining such design ele ments rotor stiffness blade inertia rpm shaft height blade chordwise center-ofgravity location blade airfoil blade diame LAG HINGEArticulated LAG OAMPER PUSHROOPITCH HORN FEATHER HINGE\fl/ E ATTACHMENT FLAP HINGE ROTOR/~ SHAFT Douglas Sikorsky either directly indirectly involved rotor head blade design testing Helicopter main rotor heads fall three major design categories articulated hingeless bearingless popular ro tor head design RC Helicopters two bladed teetering rotor head comprises other category entirely articulated rotor contains three sets ball bearings support rotor blades up/down flapping fore/aft leadlagging feathering pitch change mo tions Though theyre usually complicated heavy articulated rotors used exclu sively US -manufactured helicopters three- four-bladed heads Schluter Champion example artic ulated RC model rotor heads ter fuselage inertia others fullsize helicopter industry over third engineers employed such manufacturers Bell Boeing Kaman McDonnell86 Model Aviation Above The GMP Cobra flight authors prototype rigid rotor head installed Right authors friend Joe Medrano hold ing field frequency control board Joe expert sheet metal ist machined number rotor heads discussed article Left A later generation much precise rigid rojor neaa ae signed author flies much better earlier pro totype Above authors Cobra hovering new rigid rotor head Its very steady has superfast pitch roll response leaps out like guided missile Hot dog pilots will really enjoy hingeless rotor introduced 1970s equipped single set ball bearings used feathering up/down flapping fore/aft lead-lagging motions blade achieved either flexing nonrigid rotor hub flexing pliable root end rotor blade Advan tages hingeless rotor its minimal parts count fact aerodynam ically clean good control response Among full-size choppers type rotor Germanys MBB BO-105 Englands Westland Lynx Frances Aerospecial Ecureuil Hingeless rotors RC model Helicopters include 3OMX Kalt Baron K4-SB K3-SB ro tor heads Kalt Cyclone Baron 60 As mentioned already bearingless ro tor has sparked quite lot excitement world helicopter rotor design First developed 1980s rotor uses sup ple composite material called Flexbeam stead bearings Flapping lead-lagging feathering accomplished flex ing twisting Flexbeam Peka W Germany makes two- three- four- five-bladed bearingless main ro tor heads RC Helicopters Unfortu nately however no longer avail able US Both RC full-size bear ingless main rotor systems very difficult design properly Incorrect flexibility Left Close-up big teetering head design installed GMP Hind24 military drone nicknamed MF-1 monster chopper uses dumbbell weights instead Hiller paddles Since Bell control system lacks stabilizer damper Helicopter very stable has slow response isnt aerobatic Above Hinds designer John Gorham preparing lift off helicopter weighs 150 lb has 10-ft-dia rotors powered 350cc gasoline engine Above example Schiuter fixed-pitch S-head introduced Dieter Schluter back 1978 Its articulated ro tor flap hinge offset Right S-head installed authors Schluter Helibaby Hughes 500 body design pro vides much precise control response freely teetering two-bladed main rotor such used full-size Jet Ranger stiffness may result flutter problems ground air resonance reader wishes detailed comparison effects three types rotor heads RC Helicopter per formance referred article RC Ro tor Head Theory June 1989 issue Model Builder magazine article will improve understanding theory behind model Helicopter rotor system two-bladed teetering head design has distinct advantage RC Helicopter appli cations Most Helicopters equipped system because its very simple build set up teetering rotor head hub de signed pivot pin creating teeter ing motion blades inspired its name design will work two bladed system addition RC Helicopter Left Hirobos DDF Dual Dampened Flapping rotor head GMP Stork DDF combines features teetering rotor head articulated flap hinge offset entire hub can teeter about center pin rotor can flap up down individually installation flybar removed experiment didnt work out Right photo shows authors four-bladed hingeless rotor made stacking two Kalt Baron 30 rotor heads setup flies quite well Use two Kalt K4-SB heads 40- 60-size Helicopters April 1990 87 models full-size Bell Jet Ranger UH-l Huey Cobra Gunship feature two bladed teetering rotor designs variation teetering rotor head rigid rotor design hub bolted solidly main rotor shaft pre vent teetering very few full-size helicopters equipped rigid rotor head Lockheed 286 aircraft never reached production stage rigid rotor has advantage su perb almost instantaneous control power pilot feeds cyclic control tilt main rotor disc fuselage re sponds immediately contrast teeter ing rotor gives sluggish cyclic control Since its main rotor disc can tilt re spect main rotor shaft no direct pitch roll moment transferred main rotor fuselage Model Helicopters have overcome problem employing rubber damper 0-ring inside teetering hub As hub teeters rubber functions like spring transmit rotor tilt moment pitch roll fuselage permits RC Helicop ters fancy aerobatics full-size helicopters cannot rubber damper made sufficiently stiff teetering head will behave like rigid rotor head As pilot com presses damper Helicopter re sponds quickly However vibration increases well since its transferred di rectly through hub shaft fuse lage can have adverse effect receiver servos Two originaldesign rigid rotor heads shown some illustra tions Tested GMP Cobra provided su perfast control uncanny imita tion its veno mous namesake Cobra hovers sol idly until re ceives control command leaps out like guided missile Pilots enjoy hot-dogging will probably have fun rigid rotor Just sure youre ballthis machine has raw power F-16 prototype rigid rotor design made cutting GMP Custom head two halves coupling ma chined aluminum hub hub fits tightly over 10mm main rotor shaft However feathering axis two blades must exact alignment found difficult achieve proto type rigid rotor slightest imperfec tion such misalignment being out track imbalance will cause serious vi bration second rigid rotor hub pre cisely machined lathe avoid misalign ment Installed Cobra rotor head eliminated vibration entirely Heli copter flew superbly Although Cobra hovers very well rigid rotor system tends nose up quite severely forward flight Note both rotor heads flybarless creasing blade size 135 grams 160 grams would probably mitigate nose-up tendency Note also GMP flybarless Legend doesnt share nose-up tendency Its stiff-teetering head prevents gust-induced rotor flapback being transmitted fuselage frankly much prefer flying Legend rigid-rotor Cobra Perhaps Im cut out F-16 type flying However mounting set flexible blades Co bra would probably improve its flight per formance considerably blades functioning like stiff hingeless rotor / BO-105 hingeless hub fiberglass blades produced WIK Modelle Germany Intro duced 1970s hingeless rotor equipped single set ball bearings used feathering Major advan tages design minimal parts count its aerodynamically clean profile Cobra should fly better Helicop ters full-size MBB BO-lOS illustrates concept Though has rigid titanium hub four flexible fiberglass blades provide flapping flexibility works better teetering rotor head because theres no teetering slop dead-band teetering pin/roller bearing location Wik Modelle Products West Germany makes Scale BO-lOS rigid hub very flexible fiberglass blades RC Helicop ters understand currently im ported US firm plan try unit publish results GMP Hind-24 drone Helicopter seen two pictures equipped big teetering rotor head Nicknamed MF- 1 chopper uses dumbbell weights instead Continued page 183 88 Model Aviation four-bladed rigid tail rotor hub plate provides excellent tail thrust control unit marketed Victor Dziabczenko David Grabski around $100 Call either detailed technical price information 1-818/341-2159 1 -805/296-0860 Above authors original-design bearingless main rotor head Torlon flex beam incorporated design provides bend ing torsion functions Torlon petroleum-based synthetic prod uct has properties steel costs about 100 times Right aluminum post shown along Torlon flex beams can attached top head support flybar ahilizer achieve smooth level power slight indication turn l turned large left circles power glide mode Gradually increase run time use mall pieces clay weight nose tail r either wing tip achieve perfect light path possible youre com letely satisfied install 5- 6-in-dia lastic prop increase charge time little power needed try 7-inha Peck-Polymers plastic prop trimmed powered properly Falcon will climb very slow re distic rate wide circles 1 /2 ninutes cruise its maximum alti ude short before descending low wide circles gentle landings aIm day near-maximum charges ThE WIlQMATEKTM rhe extra large handle bends 1/8-1/4 coils Si 32-3I1& music wire Wire creep eliminated ur ANTI-KREEP WIRE LOCKIN free catalog also has hardware accessories JOM COMPANY 114 WashIngton Terr Dept Waukegan IL 60085 1st US RIC Flight School Stop Crashing Start Learning CLASSES FILLING FAST Info pack $200 1st US R/C FLIGHT SCHOOL 521 S Sawyer. Shawano WI 54166 t7151 524-2985 Hiller paddles Since Bell control sys tem lacks stabilizer damper Helicop ter stable aerobatic flight 150 lb powered 350cc gasoline en gine very large Helicopter dont want get anywhere near 10-ftdia main rotor MF-l uses 60-size Competitor main rotor blades tail blades Notice pictures Schluter fixedpitch S-head S-head Schluter Helibaby Hughes 500 body system introduced Mr Schluter back 1978 Its two-bladed ar ticulated rotor flap hinge offset confused teetering head rotor Flap hinge offset provides better control re sponse freely teetering two-bladed main rotor such used full-size Jet Ranger Kyoshos new Concept 30 ex ample collective-pitch Helicopter two-bladed flap hinge offset articulated main rotor Another picture shows Hirobos DDF Dual Dampened Flapping head GMP Stork DDF combines features teetering rotor head artic ulated flap hinge offset entire hub can teeter about center pin ro tor blade can flap up down individually result softnesss makes very stable flight characteristics original Hirobo Shuttle introduced 1985 also individual blade flapping design However flapping head overly soft excellent ginners also caused blades strike tail boom hard landings Hirobo rec ognized problem has equipped its Shuttles since 1987 floating axle design similar found Schluter Champion Miniature Aircraft X Cell new head Shuttle both stable aerobatic experiment removed stabi lizer bar assembly see Stork would perform flybarless Helicopter April 1990 183 model will turn breathtaking flights over two minutes glide may resem ble Wakefield Free Flighter can sniff out thermals tempted After Falcon Heli Rotors/Wang Continued page 88 VENO MOUNTS TNE VIBRATION lOLLER Fad end fuel pOaf flee axes ieoiefan fa 25 Ia f 20 an0nea ea-txau F S al S Uslia f ieaalf engfle nouffe Typaai aibfefran reduCtIOn 70% Ma 80% Oft kit COnSIStS OfOuntt isolate Ina pointS seoond 1~~ weetra, iubna jnSfuOtlOnS Sena Sf200 CheCk O Inane OldOt Fe kif OAA PRODUCTS P0 SOS aReas SARASOTA FL 342S3 Sf33774252 FL residents add 72 Caret tax IRFORMATION eand SASS Bob Fiorenzej Hobby Center Inc Dealer Yellow AircraftJLE UPS Orders Shipped Daily Now Available Faatcove coasting Mate,al Visit Showroom 35 win D sney Watidi NEW custow Building Sern Ce 420 WesO SR 434407 327-6383 Winter Springs FL 32708Fax 407 327-7148 3 New ARFs ZMP MONARCH AMA Sport Pattern span 66 area 750 sq motor 4 stroke 90 60 cu Preassembled balsa fuselage vdneered wing shaped balsa pail Lesan canopy epoxy cowl illustrated assembly manual c ZIMPRO MARKETING Pu suuJoltouKxIoGtTS3PSJO PiJOSE 51 axstex found didnt fly well rea son Extra damping quick control re sponse needed tame RC Helicopters much difficult fly full-size counterparts flybarless RC Helicopters depend stiff main rotor head improve vehicles pitch roll damping control power four-bladed hingeless head shown pictures made stacking two Baron 3OMX two-bladed hingeless heads result similar full-size Westland Lynx rotor head steel flexbeam hub gives comparable flap flexibil ity other type hingeless head BO-105 made MBB acquires its flap flexibility through fiberglass blades Wik Modelle also produces BO-105 hingeless hub blades As heads better depends whether youre talk ing Germans British original-design bearingless rotor head uses flexbeam provide bending torsion Its machined special petroleum-based synthetic called Torlon Manufactured Amoco Petroleum Prod ucts Torlon has properties steel costs about 100 times 2-ft-sq piece sells around $700 aluminum post can added top head support flybar shown pic tures friend Joe Medrano expert sheet metalist machined number rotor Sachs Doimar Engines New Torque Customized TG Only 100% SACHS Engine 27All Engines Complete $360 NNothing Buy 31See us 100 TOLEDO Show *40000 37 *43000 42 $46000 add $50 throttlecoupled spark advance Along 27 8 32 lightweight spring start flywheel-type Sachs Dolmar Engine TG MFG 201427-3845 857 HIgh Mtn Rd N Haledon NJ 07508 heads shown photos stamped own Cobra side frames welded rear exhaust muffler Thank Joe Next months sequel will present -scale four-bladed bearingless model ro tor tested Glenn L Martin wind tun nel University Maryland Along million-dollar tunnel youll see some exotic blades swashplates miniature hydraulic servo actuators control sys tems Consortium/Hunt Continued page 104 slight down elevator pick up hold some speed chasing next thermal Ron Farkas built model Ep pIer 201 airfoil its higher weight 3 oz heavier thinner wing version flies just well higher speed Oth ers made Clark Y RAF 32 Ep pIer 193 airfoils scheduled flown soon after article submitted As builder get bored very easily same old construction techniques same old low-wing sport high-wing trainer airplanes Im hobby learn well have fun certainly did both designing Consortium hope reading about project has acquaint ed some new techniques build ing designing model airplanes youve got urge try something differentand little time spend workshopthis classy-looking good-per forming Sailplane will give lot fun small flying field RC Soaring/Blakeslee Continued page 43 museum its displays programs will knock out Make effort joinor visit join t guarantee youll regret either address National Soaring Museum RD#3 Har ris Hill Elmira NY 14903 Thanks Cal Weiss taking time tell us about NSM Im sure model Glider fliers appreciate learning about will plan stop area tn cover letter Cal mentioned tht photos prt vided Shirley Sliwa Director NSM C also passed along personal information am retired NASA Lewis Researe Center Cleveland last 22 3 years directed work Educ tional Services Office Several notable moc elers Chet Lanzo Warren Plohr Reich brothers see Warren occasion club fieldI am member America Airlines Model Club Chet course just rc cently passed away Way back membe Board NAR along John Worth kind establishes Ive fiel bit time fact know few real pros should add fly almost week Jo Elgin designer Playboy makes no bet ter flier models t have active witl RC Gliders five years am having ball managed 1 hr. 15 mm flight oh Windrifter summer Lord t t did kept pulling up kept trying keep sight reasonable alti tude tm interested areas aviation top soaring tt has always fascinated mt just because beauty carries over intc modeling Scale look beauty RC Sailplane much like real thing anything dont like its beautiful Seal model Cub flies what appears super sonic speeds wife also loves sailplanes ant together have attended several Nationals ant regional contests spectators fact las visit museum dedication thi same time Region 3 contest Harris Hill 1 guess natural believi other Sailplane modelers also interested thi full-size ones museum Its reasot put article together Perhaps some mod elers within reach museum will make ths effort visit live too far away perhaps article will interest may wish become members event atr turned want pass information tc others International Postal Challenge Old-time readers column will remember previous re ports Kale Harden Palm Harbor FL IPC idea behind postal contest club several countries fly same contest same day compare results mail sure its interesting fun-fly con cept way meet Sailplaners other countries Kale Pelicans Club St Pete sent reContinued page J& 184 Model Aviation Special Introductory Offer SUKHOI Su-26M15 ScaleIMPALA Masters Pattern span 68 area 890 sq motor 4 stroke 120 equivspan 68 area 800 sq motor 4 stroke 120 60 rear Preassembled lightweight epoxy fuselage sheeted plug-in wingsPreassembled balsa fusefage veneered plug-in wings & stabs sheeted stab fin & rudder 8 dia epoxy cowl Lexan canopy &Epoxy cowl pipe cover removable canopy Illustrated illustrated assembly manualassembly manual see hobby dealer order direct
Edition: Model Aviation - 1990/04
Page Numbers: 85, 86, 87, 88, 183, 184
For Model Helicopters Exotic Rotors both RC full-size helicopter design rotor head holds key improving flight performance Researchers continually searching ultimate design Part two EJames M Wang AS ANY helicopter flight engineer will tell main rotor sys tem important element both full-size model hel icopter design Thats because rotor system comprises rotor head blades has multiple control functions sub stantial impact flight dynamics professional work conduct research full-size helicop ter rotor systems Imagine trying design aircraft know ing fly themor least knowing fly RC coun terparts Its tantamount calling worlds best meat loaf cook vegetarian Experimenting RC Heli copter design spare time sharpens intuition analogous different problems encountered full-size chop pers Working out problems RC Heli copters great way predict new helicopter design will behave before crunch through complex theories computer first half two-part article de scribes several uncommon rotor heads Ive designed installation RC Heli copters Part two will discuss current re search project wind tunnel testing 1A.scale state-of-the-art bearingless rotor system future full-size applications Bearingless main rotors hottest topic todays helicopter community As re cently 1988 worlds first bearingless rotor-equipped helicopter introduced Germany MBB US researchers simple line drawing demonstrates four transmitter func tions can control six degrees freedom Helicopter 1 collective 2 pitch cyclic 3 roll cyclic 4 tail rotor thrust making effort stay competitive Four fundamental directional controls employed helicopter flight collec tive fore/aft cyclic roll cyclic head ing control determine helicopters degree freedom vertical pitch roll yaw functions respectively Since three out four essential controls origi nate main rotor careful rotor design paramount tailoring helicopter handling characteristics thrust generated main rotor keeps helicopter aloft deter mines directional control except heading governed tail ro tor pilot controls vertical up-and down motion varying amount main rotor thrust creates forward thrust tilting spinning rotor disc forward elicits right left movement tilt ing spinning disc desired direction tail rotor needed counteract torque generated main rotor vary ing tail rotor thrust pilot can control heading provides lift control well offering some damping restoring force craft rotating main rotor also makes helicopter inherently unsta ble Left unassisted helicopter will drift hover becoming slightly stable forward flight because aero dynamic damping produced horizon tal vertical fins Hence challenge helicopter designer overcome inherent instability caused main rotor Helicopter designers constantly strive improve aerodynamic stability control April 1990 85 Above The authors talthful GMP Cobra equipped testing rigid rotor assembly Right Close-up authors prototype rigid rotor head hub bolted solidly main rotor shaft prevent teetering object arrangement obtain almost instantaneous control power pilot feeds cyclic con trol tilt main rotor disc fuselage responds immediately Hingeless Bearingless TWIN C-SECTION FLEXBEAM BLAOE TORQUE TUBE PITCHLINK PIT Three major categories rotor head design redefining such design ele ments rotor stiffness blade inertia rpm shaft height blade chordwise center-ofgravity location blade airfoil blade diame LAG HINGEArticulated LAG OAMPER PUSHROOPITCH HORN FEATHER HINGE\fl/ E ATTACHMENT FLAP HINGE ROTOR/~ SHAFT Douglas Sikorsky either directly indirectly involved rotor head blade design testing Helicopter main rotor heads fall three major design categories articulated hingeless bearingless popular ro tor head design RC Helicopters two bladed teetering rotor head comprises other category entirely articulated rotor contains three sets ball bearings support rotor blades up/down flapping fore/aft leadlagging feathering pitch change mo tions Though theyre usually complicated heavy articulated rotors used exclu sively US -manufactured helicopters three- four-bladed heads Schluter Champion example artic ulated RC model rotor heads ter fuselage inertia others fullsize helicopter industry over third engineers employed such manufacturers Bell Boeing Kaman McDonnell86 Model Aviation Above The GMP Cobra flight authors prototype rigid rotor head installed Right authors friend Joe Medrano hold ing field frequency control board Joe expert sheet metal ist machined number rotor heads discussed article Left A later generation much precise rigid rojor neaa ae signed author flies much better earlier pro totype Above authors Cobra hovering new rigid rotor head Its very steady has superfast pitch roll response leaps out like guided missile Hot dog pilots will really enjoy hingeless rotor introduced 1970s equipped single set ball bearings used feathering up/down flapping fore/aft lead-lagging motions blade achieved either flexing nonrigid rotor hub flexing pliable root end rotor blade Advan tages hingeless rotor its minimal parts count fact aerodynam ically clean good control response Among full-size choppers type rotor Germanys MBB BO-105 Englands Westland Lynx Frances Aerospecial Ecureuil Hingeless rotors RC model Helicopters include 3OMX Kalt Baron K4-SB K3-SB ro tor heads Kalt Cyclone Baron 60 As mentioned already bearingless ro tor has sparked quite lot excitement world helicopter rotor design First developed 1980s rotor uses sup ple composite material called Flexbeam stead bearings Flapping lead-lagging feathering accomplished flex ing twisting Flexbeam Peka W Germany makes two- three- four- five-bladed bearingless main ro tor heads RC Helicopters Unfortu nately however no longer avail able US Both RC full-size bear ingless main rotor systems very difficult design properly Incorrect flexibility Left Close-up big teetering head design installed GMP Hind24 military drone nicknamed MF-1 monster chopper uses dumbbell weights instead Hiller paddles Since Bell control system lacks stabilizer damper Helicopter very stable has slow response isnt aerobatic Above Hinds designer John Gorham preparing lift off helicopter weighs 150 lb has 10-ft-dia rotors powered 350cc gasoline engine Above example Schiuter fixed-pitch S-head introduced Dieter Schluter back 1978 Its articulated ro tor flap hinge offset Right S-head installed authors Schluter Helibaby Hughes 500 body design pro vides much precise control response freely teetering two-bladed main rotor such used full-size Jet Ranger stiffness may result flutter problems ground air resonance reader wishes detailed comparison effects three types rotor heads RC Helicopter per formance referred article RC Ro tor Head Theory June 1989 issue Model Builder magazine article will improve understanding theory behind model Helicopter rotor system two-bladed teetering head design has distinct advantage RC Helicopter appli cations Most Helicopters equipped system because its very simple build set up teetering rotor head hub de signed pivot pin creating teeter ing motion blades inspired its name design will work two bladed system addition RC Helicopter Left Hirobos DDF Dual Dampened Flapping rotor head GMP Stork DDF combines features teetering rotor head articulated flap hinge offset entire hub can teeter about center pin rotor can flap up down individually installation flybar removed experiment didnt work out Right photo shows authors four-bladed hingeless rotor made stacking two Kalt Baron 30 rotor heads setup flies quite well Use two Kalt K4-SB heads 40- 60-size Helicopters April 1990 87 models full-size Bell Jet Ranger UH-l Huey Cobra Gunship feature two bladed teetering rotor designs variation teetering rotor head rigid rotor design hub bolted solidly main rotor shaft pre vent teetering very few full-size helicopters equipped rigid rotor head Lockheed 286 aircraft never reached production stage rigid rotor has advantage su perb almost instantaneous control power pilot feeds cyclic control tilt main rotor disc fuselage re sponds immediately contrast teeter ing rotor gives sluggish cyclic control Since its main rotor disc can tilt re spect main rotor shaft no direct pitch roll moment transferred main rotor fuselage Model Helicopters have overcome problem employing rubber damper 0-ring inside teetering hub As hub teeters rubber functions like spring transmit rotor tilt moment pitch roll fuselage permits RC Helicop ters fancy aerobatics full-size helicopters cannot rubber damper made sufficiently stiff teetering head will behave like rigid rotor head As pilot com presses damper Helicopter re sponds quickly However vibration increases well since its transferred di rectly through hub shaft fuse lage can have adverse effect receiver servos Two originaldesign rigid rotor heads shown some illustra tions Tested GMP Cobra provided su perfast control uncanny imita tion its veno mous namesake Cobra hovers sol idly until re ceives control command leaps out like guided missile Pilots enjoy hot-dogging will probably have fun rigid rotor Just sure youre ballthis machine has raw power F-16 prototype rigid rotor design made cutting GMP Custom head two halves coupling ma chined aluminum hub hub fits tightly over 10mm main rotor shaft However feathering axis two blades must exact alignment found difficult achieve proto type rigid rotor slightest imperfec tion such misalignment being out track imbalance will cause serious vi bration second rigid rotor hub pre cisely machined lathe avoid misalign ment Installed Cobra rotor head eliminated vibration entirely Heli copter flew superbly Although Cobra hovers very well rigid rotor system tends nose up quite severely forward flight Note both rotor heads flybarless creasing blade size 135 grams 160 grams would probably mitigate nose-up tendency Note also GMP flybarless Legend doesnt share nose-up tendency Its stiff-teetering head prevents gust-induced rotor flapback being transmitted fuselage frankly much prefer flying Legend rigid-rotor Cobra Perhaps Im cut out F-16 type flying However mounting set flexible blades Co bra would probably improve its flight per formance considerably blades functioning like stiff hingeless rotor / BO-105 hingeless hub fiberglass blades produced WIK Modelle Germany Intro duced 1970s hingeless rotor equipped single set ball bearings used feathering Major advan tages design minimal parts count its aerodynamically clean profile Cobra should fly better Helicop ters full-size MBB BO-lOS illustrates concept Though has rigid titanium hub four flexible fiberglass blades provide flapping flexibility works better teetering rotor head because theres no teetering slop dead-band teetering pin/roller bearing location Wik Modelle Products West Germany makes Scale BO-lOS rigid hub very flexible fiberglass blades RC Helicop ters understand currently im ported US firm plan try unit publish results GMP Hind-24 drone Helicopter seen two pictures equipped big teetering rotor head Nicknamed MF- 1 chopper uses dumbbell weights instead Continued page 183 88 Model Aviation four-bladed rigid tail rotor hub plate provides excellent tail thrust control unit marketed Victor Dziabczenko David Grabski around $100 Call either detailed technical price information 1-818/341-2159 1 -805/296-0860 Above authors original-design bearingless main rotor head Torlon flex beam incorporated design provides bend ing torsion functions Torlon petroleum-based synthetic prod uct has properties steel costs about 100 times Right aluminum post shown along Torlon flex beams can attached top head support flybar ahilizer achieve smooth level power slight indication turn l turned large left circles power glide mode Gradually increase run time use mall pieces clay weight nose tail r either wing tip achieve perfect light path possible youre com letely satisfied install 5- 6-in-dia lastic prop increase charge time little power needed try 7-inha Peck-Polymers plastic prop trimmed powered properly Falcon will climb very slow re distic rate wide circles 1 /2 ninutes cruise its maximum alti ude short before descending low wide circles gentle landings aIm day near-maximum charges ThE WIlQMATEKTM rhe extra large handle bends 1/8-1/4 coils Si 32-3I1& music wire Wire creep eliminated ur ANTI-KREEP WIRE LOCKIN free catalog also has hardware accessories JOM COMPANY 114 WashIngton Terr Dept Waukegan IL 60085 1st US RIC Flight School Stop Crashing Start Learning CLASSES FILLING FAST Info pack $200 1st US R/C FLIGHT SCHOOL 521 S Sawyer. Shawano WI 54166 t7151 524-2985 Hiller paddles Since Bell control sys tem lacks stabilizer damper Helicop ter stable aerobatic flight 150 lb powered 350cc gasoline en gine very large Helicopter dont want get anywhere near 10-ftdia main rotor MF-l uses 60-size Competitor main rotor blades tail blades Notice pictures Schluter fixedpitch S-head S-head Schluter Helibaby Hughes 500 body system introduced Mr Schluter back 1978 Its two-bladed ar ticulated rotor flap hinge offset confused teetering head rotor Flap hinge offset provides better control re sponse freely teetering two-bladed main rotor such used full-size Jet Ranger Kyoshos new Concept 30 ex ample collective-pitch Helicopter two-bladed flap hinge offset articulated main rotor Another picture shows Hirobos DDF Dual Dampened Flapping head GMP Stork DDF combines features teetering rotor head artic ulated flap hinge offset entire hub can teeter about center pin ro tor blade can flap up down individually result softnesss makes very stable flight characteristics original Hirobo Shuttle introduced 1985 also individual blade flapping design However flapping head overly soft excellent ginners also caused blades strike tail boom hard landings Hirobo rec ognized problem has equipped its Shuttles since 1987 floating axle design similar found Schluter Champion Miniature Aircraft X Cell new head Shuttle both stable aerobatic experiment removed stabi lizer bar assembly see Stork would perform flybarless Helicopter April 1990 183 model will turn breathtaking flights over two minutes glide may resem ble Wakefield Free Flighter can sniff out thermals tempted After Falcon Heli Rotors/Wang Continued page 88 VENO MOUNTS TNE VIBRATION lOLLER Fad end fuel pOaf flee axes ieoiefan fa 25 Ia f 20 an0nea ea-txau F S al S Uslia f ieaalf engfle nouffe Typaai aibfefran reduCtIOn 70% Ma 80% Oft kit COnSIStS OfOuntt isolate Ina pointS seoond 1~~ weetra, iubna jnSfuOtlOnS Sena Sf200 CheCk O Inane OldOt Fe kif OAA PRODUCTS P0 SOS aReas SARASOTA FL 342S3 Sf33774252 FL residents add 72 Caret tax IRFORMATION eand SASS Bob Fiorenzej Hobby Center Inc Dealer Yellow AircraftJLE UPS Orders Shipped Daily Now Available Faatcove coasting Mate,al Visit Showroom 35 win D sney Watidi NEW custow Building Sern Ce 420 WesO SR 434407 327-6383 Winter Springs FL 32708Fax 407 327-7148 3 New ARFs ZMP MONARCH AMA Sport Pattern span 66 area 750 sq motor 4 stroke 90 60 cu Preassembled balsa fuselage vdneered wing shaped balsa pail Lesan canopy epoxy cowl illustrated assembly manual c ZIMPRO MARKETING Pu suuJoltouKxIoGtTS3PSJO PiJOSE 51 axstex found didnt fly well rea son Extra damping quick control re sponse needed tame RC Helicopters much difficult fly full-size counterparts flybarless RC Helicopters depend stiff main rotor head improve vehicles pitch roll damping control power four-bladed hingeless head shown pictures made stacking two Baron 3OMX two-bladed hingeless heads result similar full-size Westland Lynx rotor head steel flexbeam hub gives comparable flap flexibil ity other type hingeless head BO-105 made MBB acquires its flap flexibility through fiberglass blades Wik Modelle also produces BO-105 hingeless hub blades As heads better depends whether youre talk ing Germans British original-design bearingless rotor head uses flexbeam provide bending torsion Its machined special petroleum-based synthetic called Torlon Manufactured Amoco Petroleum Prod ucts Torlon has properties steel costs about 100 times 2-ft-sq piece sells around $700 aluminum post can added top head support flybar shown pic tures friend Joe Medrano expert sheet metalist machined number rotor Sachs Doimar Engines New Torque Customized TG Only 100% SACHS Engine 27All Engines Complete $360 NNothing Buy 31See us 100 TOLEDO Show *40000 37 *43000 42 $46000 add $50 throttlecoupled spark advance Along 27 8 32 lightweight spring start flywheel-type Sachs Dolmar Engine TG MFG 201427-3845 857 HIgh Mtn Rd N Haledon NJ 07508 heads shown photos stamped own Cobra side frames welded rear exhaust muffler Thank Joe Next months sequel will present -scale four-bladed bearingless model ro tor tested Glenn L Martin wind tun nel University Maryland Along million-dollar tunnel youll see some exotic blades swashplates miniature hydraulic servo actuators control sys tems Consortium/Hunt Continued page 104 slight down elevator pick up hold some speed chasing next thermal Ron Farkas built model Ep pIer 201 airfoil its higher weight 3 oz heavier thinner wing version flies just well higher speed Oth ers made Clark Y RAF 32 Ep pIer 193 airfoils scheduled flown soon after article submitted As builder get bored very easily same old construction techniques same old low-wing sport high-wing trainer airplanes Im hobby learn well have fun certainly did both designing Consortium hope reading about project has acquaint ed some new techniques build ing designing model airplanes youve got urge try something differentand little time spend workshopthis classy-looking good-per forming Sailplane will give lot fun small flying field RC Soaring/Blakeslee Continued page 43 museum its displays programs will knock out Make effort joinor visit join t guarantee youll regret either address National Soaring Museum RD#3 Har ris Hill Elmira NY 14903 Thanks Cal Weiss taking time tell us about NSM Im sure model Glider fliers appreciate learning about will plan stop area tn cover letter Cal mentioned tht photos prt vided Shirley Sliwa Director NSM C also passed along personal information am retired NASA Lewis Researe Center Cleveland last 22 3 years directed work Educ tional Services Office Several notable moc elers Chet Lanzo Warren Plohr Reich brothers see Warren occasion club fieldI am member America Airlines Model Club Chet course just rc cently passed away Way back membe Board NAR along John Worth kind establishes Ive fiel bit time fact know few real pros should add fly almost week Jo Elgin designer Playboy makes no bet ter flier models t have active witl RC Gliders five years am having ball managed 1 hr. 15 mm flight oh Windrifter summer Lord t t did kept pulling up kept trying keep sight reasonable alti tude tm interested areas aviation top soaring tt has always fascinated mt just because beauty carries over intc modeling Scale look beauty RC Sailplane much like real thing anything dont like its beautiful Seal model Cub flies what appears super sonic speeds wife also loves sailplanes ant together have attended several Nationals ant regional contests spectators fact las visit museum dedication thi same time Region 3 contest Harris Hill 1 guess natural believi other Sailplane modelers also interested thi full-size ones museum Its reasot put article together Perhaps some mod elers within reach museum will make ths effort visit live too far away perhaps article will interest may wish become members event atr turned want pass information tc others International Postal Challenge Old-time readers column will remember previous re ports Kale Harden Palm Harbor FL IPC idea behind postal contest club several countries fly same contest same day compare results mail sure its interesting fun-fly con cept way meet Sailplaners other countries Kale Pelicans Club St Pete sent reContinued page J& 184 Model Aviation Special Introductory Offer SUKHOI Su-26M15 ScaleIMPALA Masters Pattern span 68 area 890 sq motor 4 stroke 120 equivspan 68 area 800 sq motor 4 stroke 120 60 rear Preassembled lightweight epoxy fuselage sheeted plug-in wingsPreassembled balsa fusefage veneered plug-in wings & stabs sheeted stab fin & rudder 8 dia epoxy cowl Lexan canopy &Epoxy cowl pipe cover removable canopy Illustrated illustrated assembly manualassembly manual see hobby dealer order direct
Edition: Model Aviation - 1990/04
Page Numbers: 85, 86, 87, 88, 183, 184
For Model Helicopters Exotic Rotors both RC full-size helicopter design rotor head holds key improving flight performance Researchers continually searching ultimate design Part two EJames M Wang AS ANY helicopter flight engineer will tell main rotor sys tem important element both full-size model hel icopter design Thats because rotor system comprises rotor head blades has multiple control functions sub stantial impact flight dynamics professional work conduct research full-size helicop ter rotor systems Imagine trying design aircraft know ing fly themor least knowing fly RC coun terparts Its tantamount calling worlds best meat loaf cook vegetarian Experimenting RC Heli copter design spare time sharpens intuition analogous different problems encountered full-size chop pers Working out problems RC Heli copters great way predict new helicopter design will behave before crunch through complex theories computer first half two-part article de scribes several uncommon rotor heads Ive designed installation RC Heli copters Part two will discuss current re search project wind tunnel testing 1A.scale state-of-the-art bearingless rotor system future full-size applications Bearingless main rotors hottest topic todays helicopter community As re cently 1988 worlds first bearingless rotor-equipped helicopter introduced Germany MBB US researchers simple line drawing demonstrates four transmitter func tions can control six degrees freedom Helicopter 1 collective 2 pitch cyclic 3 roll cyclic 4 tail rotor thrust making effort stay competitive Four fundamental directional controls employed helicopter flight collec tive fore/aft cyclic roll cyclic head ing control determine helicopters degree freedom vertical pitch roll yaw functions respectively Since three out four essential controls origi nate main rotor careful rotor design paramount tailoring helicopter handling characteristics thrust generated main rotor keeps helicopter aloft deter mines directional control except heading governed tail ro tor pilot controls vertical up-and down motion varying amount main rotor thrust creates forward thrust tilting spinning rotor disc forward elicits right left movement tilt ing spinning disc desired direction tail rotor needed counteract torque generated main rotor vary ing tail rotor thrust pilot can control heading provides lift control well offering some damping restoring force craft rotating main rotor also makes helicopter inherently unsta ble Left unassisted helicopter will drift hover becoming slightly stable forward flight because aero dynamic damping produced horizon tal vertical fins Hence challenge helicopter designer overcome inherent instability caused main rotor Helicopter designers constantly strive improve aerodynamic stability control April 1990 85 Above The authors talthful GMP Cobra equipped testing rigid rotor assembly Right Close-up authors prototype rigid rotor head hub bolted solidly main rotor shaft prevent teetering object arrangement obtain almost instantaneous control power pilot feeds cyclic con trol tilt main rotor disc fuselage responds immediately Hingeless Bearingless TWIN C-SECTION FLEXBEAM BLAOE TORQUE TUBE PITCHLINK PIT Three major categories rotor head design redefining such design ele ments rotor stiffness blade inertia rpm shaft height blade chordwise center-ofgravity location blade airfoil blade diame LAG HINGEArticulated LAG OAMPER PUSHROOPITCH HORN FEATHER HINGE\fl/ E ATTACHMENT FLAP HINGE ROTOR/~ SHAFT Douglas Sikorsky either directly indirectly involved rotor head blade design testing Helicopter main rotor heads fall three major design categories articulated hingeless bearingless popular ro tor head design RC Helicopters two bladed teetering rotor head comprises other category entirely articulated rotor contains three sets ball bearings support rotor blades up/down flapping fore/aft leadlagging feathering pitch change mo tions Though theyre usually complicated heavy articulated rotors used exclu sively US -manufactured helicopters three- four-bladed heads Schluter Champion example artic ulated RC model rotor heads ter fuselage inertia others fullsize helicopter industry over third engineers employed such manufacturers Bell Boeing Kaman McDonnell86 Model Aviation Above The GMP Cobra flight authors prototype rigid rotor head installed Right authors friend Joe Medrano hold ing field frequency control board Joe expert sheet metal ist machined number rotor heads discussed article Left A later generation much precise rigid rojor neaa ae signed author flies much better earlier pro totype Above authors Cobra hovering new rigid rotor head Its very steady has superfast pitch roll response leaps out like guided missile Hot dog pilots will really enjoy hingeless rotor introduced 1970s equipped single set ball bearings used feathering up/down flapping fore/aft lead-lagging motions blade achieved either flexing nonrigid rotor hub flexing pliable root end rotor blade Advan tages hingeless rotor its minimal parts count fact aerodynam ically clean good control response Among full-size choppers type rotor Germanys MBB BO-105 Englands Westland Lynx Frances Aerospecial Ecureuil Hingeless rotors RC model Helicopters include 3OMX Kalt Baron K4-SB K3-SB ro tor heads Kalt Cyclone Baron 60 As mentioned already bearingless ro tor has sparked quite lot excitement world helicopter rotor design First developed 1980s rotor uses sup ple composite material called Flexbeam stead bearings Flapping lead-lagging feathering accomplished flex ing twisting Flexbeam Peka W Germany makes two- three- four- five-bladed bearingless main ro tor heads RC Helicopters Unfortu nately however no longer avail able US Both RC full-size bear ingless main rotor systems very difficult design properly Incorrect flexibility Left Close-up big teetering head design installed GMP Hind24 military drone nicknamed MF-1 monster chopper uses dumbbell weights instead Hiller paddles Since Bell control system lacks stabilizer damper Helicopter very stable has slow response isnt aerobatic Above Hinds designer John Gorham preparing lift off helicopter weighs 150 lb has 10-ft-dia rotors powered 350cc gasoline engine Above example Schiuter fixed-pitch S-head introduced Dieter Schluter back 1978 Its articulated ro tor flap hinge offset Right S-head installed authors Schluter Helibaby Hughes 500 body design pro vides much precise control response freely teetering two-bladed main rotor such used full-size Jet Ranger stiffness may result flutter problems ground air resonance reader wishes detailed comparison effects three types rotor heads RC Helicopter per formance referred article RC Ro tor Head Theory June 1989 issue Model Builder magazine article will improve understanding theory behind model Helicopter rotor system two-bladed teetering head design has distinct advantage RC Helicopter appli cations Most Helicopters equipped system because its very simple build set up teetering rotor head hub de signed pivot pin creating teeter ing motion blades inspired its name design will work two bladed system addition RC Helicopter Left Hirobos DDF Dual Dampened Flapping rotor head GMP Stork DDF combines features teetering rotor head articulated flap hinge offset entire hub can teeter about center pin rotor can flap up down individually installation flybar removed experiment didnt work out Right photo shows authors four-bladed hingeless rotor made stacking two Kalt Baron 30 rotor heads setup flies quite well Use two Kalt K4-SB heads 40- 60-size Helicopters April 1990 87 models full-size Bell Jet Ranger UH-l Huey Cobra Gunship feature two bladed teetering rotor designs variation teetering rotor head rigid rotor design hub bolted solidly main rotor shaft pre vent teetering very few full-size helicopters equipped rigid rotor head Lockheed 286 aircraft never reached production stage rigid rotor has advantage su perb almost instantaneous control power pilot feeds cyclic control tilt main rotor disc fuselage re sponds immediately contrast teeter ing rotor gives sluggish cyclic control Since its main rotor disc can tilt re spect main rotor shaft no direct pitch roll moment transferred main rotor fuselage Model Helicopters have overcome problem employing rubber damper 0-ring inside teetering hub As hub teeters rubber functions like spring transmit rotor tilt moment pitch roll fuselage permits RC Helicop ters fancy aerobatics full-size helicopters cannot rubber damper made sufficiently stiff teetering head will behave like rigid rotor head As pilot com presses damper Helicopter re sponds quickly However vibration increases well since its transferred di rectly through hub shaft fuse lage can have adverse effect receiver servos Two originaldesign rigid rotor heads shown some illustra tions Tested GMP Cobra provided su perfast control uncanny imita tion its veno mous namesake Cobra hovers sol idly until re ceives control command leaps out like guided missile Pilots enjoy hot-dogging will probably have fun rigid rotor Just sure youre ballthis machine has raw power F-16 prototype rigid rotor design made cutting GMP Custom head two halves coupling ma chined aluminum hub hub fits tightly over 10mm main rotor shaft However feathering axis two blades must exact alignment found difficult achieve proto type rigid rotor slightest imperfec tion such misalignment being out track imbalance will cause serious vi bration second rigid rotor hub pre cisely machined lathe avoid misalign ment Installed Cobra rotor head eliminated vibration entirely Heli copter flew superbly Although Cobra hovers very well rigid rotor system tends nose up quite severely forward flight Note both rotor heads flybarless creasing blade size 135 grams 160 grams would probably mitigate nose-up tendency Note also GMP flybarless Legend doesnt share nose-up tendency Its stiff-teetering head prevents gust-induced rotor flapback being transmitted fuselage frankly much prefer flying Legend rigid-rotor Cobra Perhaps Im cut out F-16 type flying However mounting set flexible blades Co bra would probably improve its flight per formance considerably blades functioning like stiff hingeless rotor / BO-105 hingeless hub fiberglass blades produced WIK Modelle Germany Intro duced 1970s hingeless rotor equipped single set ball bearings used feathering Major advan tages design minimal parts count its aerodynamically clean profile Cobra should fly better Helicop ters full-size MBB BO-lOS illustrates concept Though has rigid titanium hub four flexible fiberglass blades provide flapping flexibility works better teetering rotor head because theres no teetering slop dead-band teetering pin/roller bearing location Wik Modelle Products West Germany makes Scale BO-lOS rigid hub very flexible fiberglass blades RC Helicop ters understand currently im ported US firm plan try unit publish results GMP Hind-24 drone Helicopter seen two pictures equipped big teetering rotor head Nicknamed MF- 1 chopper uses dumbbell weights instead Continued page 183 88 Model Aviation four-bladed rigid tail rotor hub plate provides excellent tail thrust control unit marketed Victor Dziabczenko David Grabski around $100 Call either detailed technical price information 1-818/341-2159 1 -805/296-0860 Above authors original-design bearingless main rotor head Torlon flex beam incorporated design provides bend ing torsion functions Torlon petroleum-based synthetic prod uct has properties steel costs about 100 times Right aluminum post shown along Torlon flex beams can attached top head support flybar ahilizer achieve smooth level power slight indication turn l turned large left circles power glide mode Gradually increase run time use mall pieces clay weight nose tail r either wing tip achieve perfect light path possible youre com letely satisfied install 5- 6-in-dia lastic prop increase charge time little power needed try 7-inha Peck-Polymers plastic prop trimmed powered properly Falcon will climb very slow re distic rate wide circles 1 /2 ninutes cruise its maximum alti ude short before descending low wide circles gentle landings aIm day near-maximum charges ThE WIlQMATEKTM rhe extra large handle bends 1/8-1/4 coils Si 32-3I1& music wire Wire creep eliminated ur ANTI-KREEP WIRE LOCKIN free catalog also has hardware accessories JOM COMPANY 114 WashIngton Terr Dept Waukegan IL 60085 1st US RIC Flight School Stop Crashing Start Learning CLASSES FILLING FAST Info pack $200 1st US R/C FLIGHT SCHOOL 521 S Sawyer. Shawano WI 54166 t7151 524-2985 Hiller paddles Since Bell control sys tem lacks stabilizer damper Helicop ter stable aerobatic flight 150 lb powered 350cc gasoline en gine very large Helicopter dont want get anywhere near 10-ftdia main rotor MF-l uses 60-size Competitor main rotor blades tail blades Notice pictures Schluter fixedpitch S-head S-head Schluter Helibaby Hughes 500 body system introduced Mr Schluter back 1978 Its two-bladed ar ticulated rotor flap hinge offset confused teetering head rotor Flap hinge offset provides better control re sponse freely teetering two-bladed main rotor such used full-size Jet Ranger Kyoshos new Concept 30 ex ample collective-pitch Helicopter two-bladed flap hinge offset articulated main rotor Another picture shows Hirobos DDF Dual Dampened Flapping head GMP Stork DDF combines features teetering rotor head artic ulated flap hinge offset entire hub can teeter about center pin ro tor blade can flap up down individually result softnesss makes very stable flight characteristics original Hirobo Shuttle introduced 1985 also individual blade flapping design However flapping head overly soft excellent ginners also caused blades strike tail boom hard landings Hirobo rec ognized problem has equipped its Shuttles since 1987 floating axle design similar found Schluter Champion Miniature Aircraft X Cell new head Shuttle both stable aerobatic experiment removed stabi lizer bar assembly see Stork would perform flybarless Helicopter April 1990 183 model will turn breathtaking flights over two minutes glide may resem ble Wakefield Free Flighter can sniff out thermals tempted After Falcon Heli Rotors/Wang Continued page 88 VENO MOUNTS TNE VIBRATION lOLLER Fad end fuel pOaf flee axes ieoiefan fa 25 Ia f 20 an0nea ea-txau F S al S Uslia f ieaalf engfle nouffe Typaai aibfefran reduCtIOn 70% Ma 80% Oft kit COnSIStS OfOuntt isolate Ina pointS seoond 1~~ weetra, iubna jnSfuOtlOnS Sena Sf200 CheCk O Inane OldOt Fe kif OAA PRODUCTS P0 SOS aReas SARASOTA FL 342S3 Sf33774252 FL residents add 72 Caret tax IRFORMATION eand SASS Bob Fiorenzej Hobby Center Inc Dealer Yellow AircraftJLE UPS Orders Shipped Daily Now Available Faatcove coasting Mate,al Visit Showroom 35 win D sney Watidi NEW custow Building Sern Ce 420 WesO SR 434407 327-6383 Winter Springs FL 32708Fax 407 327-7148 3 New ARFs ZMP MONARCH AMA Sport Pattern span 66 area 750 sq motor 4 stroke 90 60 cu Preassembled balsa fuselage vdneered wing shaped balsa pail Lesan canopy epoxy cowl illustrated assembly manual c ZIMPRO MARKETING Pu suuJoltouKxIoGtTS3PSJO PiJOSE 51 axstex found didnt fly well rea son Extra damping quick control re sponse needed tame RC Helicopters much difficult fly full-size counterparts flybarless RC Helicopters depend stiff main rotor head improve vehicles pitch roll damping control power four-bladed hingeless head shown pictures made stacking two Baron 3OMX two-bladed hingeless heads result similar full-size Westland Lynx rotor head steel flexbeam hub gives comparable flap flexibil ity other type hingeless head BO-105 made MBB acquires its flap flexibility through fiberglass blades Wik Modelle also produces BO-105 hingeless hub blades As heads better depends whether youre talk ing Germans British original-design bearingless rotor head uses flexbeam provide bending torsion Its machined special petroleum-based synthetic called Torlon Manufactured Amoco Petroleum Prod ucts Torlon has properties steel costs about 100 times 2-ft-sq piece sells around $700 aluminum post can added top head support flybar shown pic tures friend Joe Medrano expert sheet metalist machined number rotor Sachs Doimar Engines New Torque Customized TG Only 100% SACHS Engine 27All Engines Complete $360 NNothing Buy 31See us 100 TOLEDO Show *40000 37 *43000 42 $46000 add $50 throttlecoupled spark advance Along 27 8 32 lightweight spring start flywheel-type Sachs Dolmar Engine TG MFG 201427-3845 857 HIgh Mtn Rd N Haledon NJ 07508 heads shown photos stamped own Cobra side frames welded rear exhaust muffler Thank Joe Next months sequel will present -scale four-bladed bearingless model ro tor tested Glenn L Martin wind tun nel University Maryland Along million-dollar tunnel youll see some exotic blades swashplates miniature hydraulic servo actuators control sys tems Consortium/Hunt Continued page 104 slight down elevator pick up hold some speed chasing next thermal Ron Farkas built model Ep pIer 201 airfoil its higher weight 3 oz heavier thinner wing version flies just well higher speed Oth ers made Clark Y RAF 32 Ep pIer 193 airfoils scheduled flown soon after article submitted As builder get bored very easily same old construction techniques same old low-wing sport high-wing trainer airplanes Im hobby learn well have fun certainly did both designing Consortium hope reading about project has acquaint ed some new techniques build ing designing model airplanes youve got urge try something differentand little time spend workshopthis classy-looking good-per forming Sailplane will give lot fun small flying field RC Soaring/Blakeslee Continued page 43 museum its displays programs will knock out Make effort joinor visit join t guarantee youll regret either address National Soaring Museum RD#3 Har ris Hill Elmira NY 14903 Thanks Cal Weiss taking time tell us about NSM Im sure model Glider fliers appreciate learning about will plan stop area tn cover letter Cal mentioned tht photos prt vided Shirley Sliwa Director NSM C also passed along personal information am retired NASA Lewis Researe Center Cleveland last 22 3 years directed work Educ tional Services Office Several notable moc elers Chet Lanzo Warren Plohr Reich brothers see Warren occasion club fieldI am member America Airlines Model Club Chet course just rc cently passed away Way back membe Board NAR along John Worth kind establishes Ive fiel bit time fact know few real pros should add fly almost week Jo Elgin designer Playboy makes no bet ter flier models t have active witl RC Gliders five years am having ball managed 1 hr. 15 mm flight oh Windrifter summer Lord t t did kept pulling up kept trying keep sight reasonable alti tude tm interested areas aviation top soaring tt has always fascinated mt just because beauty carries over intc modeling Scale look beauty RC Sailplane much like real thing anything dont like its beautiful Seal model Cub flies what appears super sonic speeds wife also loves sailplanes ant together have attended several Nationals ant regional contests spectators fact las visit museum dedication thi same time Region 3 contest Harris Hill 1 guess natural believi other Sailplane modelers also interested thi full-size ones museum Its reasot put article together Perhaps some mod elers within reach museum will make ths effort visit live too far away perhaps article will interest may wish become members event atr turned want pass information tc others International Postal Challenge Old-time readers column will remember previous re ports Kale Harden Palm Harbor FL IPC idea behind postal contest club several countries fly same contest same day compare results mail sure its interesting fun-fly con cept way meet Sailplaners other countries Kale Pelicans Club St Pete sent reContinued page J& 184 Model Aviation Special Introductory Offer SUKHOI Su-26M15 ScaleIMPALA Masters Pattern span 68 area 890 sq motor 4 stroke 120 equivspan 68 area 800 sq motor 4 stroke 120 60 rear Preassembled lightweight epoxy fuselage sheeted plug-in wingsPreassembled balsa fusefage veneered plug-in wings & stabs sheeted stab fin & rudder 8 dia epoxy cowl Lexan canopy &Epoxy cowl pipe cover removable canopy Illustrated illustrated assembly manualassembly manual see hobby dealer order direct
Edition: Model Aviation - 1990/04
Page Numbers: 85, 86, 87, 88, 183, 184
For Model Helicopters Exotic Rotors both RC full-size helicopter design rotor head holds key improving flight performance Researchers continually searching ultimate design Part two EJames M Wang AS ANY helicopter flight engineer will tell main rotor sys tem important element both full-size model hel icopter design Thats because rotor system comprises rotor head blades has multiple control functions sub stantial impact flight dynamics professional work conduct research full-size helicop ter rotor systems Imagine trying design aircraft know ing fly themor least knowing fly RC coun terparts Its tantamount calling worlds best meat loaf cook vegetarian Experimenting RC Heli copter design spare time sharpens intuition analogous different problems encountered full-size chop pers Working out problems RC Heli copters great way predict new helicopter design will behave before crunch through complex theories computer first half two-part article de scribes several uncommon rotor heads Ive designed installation RC Heli copters Part two will discuss current re search project wind tunnel testing 1A.scale state-of-the-art bearingless rotor system future full-size applications Bearingless main rotors hottest topic todays helicopter community As re cently 1988 worlds first bearingless rotor-equipped helicopter introduced Germany MBB US researchers simple line drawing demonstrates four transmitter func tions can control six degrees freedom Helicopter 1 collective 2 pitch cyclic 3 roll cyclic 4 tail rotor thrust making effort stay competitive Four fundamental directional controls employed helicopter flight collec tive fore/aft cyclic roll cyclic head ing control determine helicopters degree freedom vertical pitch roll yaw functions respectively Since three out four essential controls origi nate main rotor careful rotor design paramount tailoring helicopter handling characteristics thrust generated main rotor keeps helicopter aloft deter mines directional control except heading governed tail ro tor pilot controls vertical up-and down motion varying amount main rotor thrust creates forward thrust tilting spinning rotor disc forward elicits right left movement tilt ing spinning disc desired direction tail rotor needed counteract torque generated main rotor vary ing tail rotor thrust pilot can control heading provides lift control well offering some damping restoring force craft rotating main rotor also makes helicopter inherently unsta ble Left unassisted helicopter will drift hover becoming slightly stable forward flight because aero dynamic damping produced horizon tal vertical fins Hence challenge helicopter designer overcome inherent instability caused main rotor Helicopter designers constantly strive improve aerodynamic stability control April 1990 85 Above The authors talthful GMP Cobra equipped testing rigid rotor assembly Right Close-up authors prototype rigid rotor head hub bolted solidly main rotor shaft prevent teetering object arrangement obtain almost instantaneous control power pilot feeds cyclic con trol tilt main rotor disc fuselage responds immediately Hingeless Bearingless TWIN C-SECTION FLEXBEAM BLAOE TORQUE TUBE PITCHLINK PIT Three major categories rotor head design redefining such design ele ments rotor stiffness blade inertia rpm shaft height blade chordwise center-ofgravity location blade airfoil blade diame LAG HINGEArticulated LAG OAMPER PUSHROOPITCH HORN FEATHER HINGE\fl/ E ATTACHMENT FLAP HINGE ROTOR/~ SHAFT Douglas Sikorsky either directly indirectly involved rotor head blade design testing Helicopter main rotor heads fall three major design categories articulated hingeless bearingless popular ro tor head design RC Helicopters two bladed teetering rotor head comprises other category entirely articulated rotor contains three sets ball bearings support rotor blades up/down flapping fore/aft leadlagging feathering pitch change mo tions Though theyre usually complicated heavy articulated rotors used exclu sively US -manufactured helicopters three- four-bladed heads Schluter Champion example artic ulated RC model rotor heads ter fuselage inertia others fullsize helicopter industry over third engineers employed such manufacturers Bell Boeing Kaman McDonnell86 Model Aviation Above The GMP Cobra flight authors prototype rigid rotor head installed Right authors friend Joe Medrano hold ing field frequency control board Joe expert sheet metal ist machined number rotor heads discussed article Left A later generation much precise rigid rojor neaa ae signed author flies much better earlier pro totype Above authors Cobra hovering new rigid rotor head Its very steady has superfast pitch roll response leaps out like guided missile Hot dog pilots will really enjoy hingeless rotor introduced 1970s equipped single set ball bearings used feathering up/down flapping fore/aft lead-lagging motions blade achieved either flexing nonrigid rotor hub flexing pliable root end rotor blade Advan tages hingeless rotor its minimal parts count fact aerodynam ically clean good control response Among full-size choppers type rotor Germanys MBB BO-105 Englands Westland Lynx Frances Aerospecial Ecureuil Hingeless rotors RC model Helicopters include 3OMX Kalt Baron K4-SB K3-SB ro tor heads Kalt Cyclone Baron 60 As mentioned already bearingless ro tor has sparked quite lot excitement world helicopter rotor design First developed 1980s rotor uses sup ple composite material called Flexbeam stead bearings Flapping lead-lagging feathering accomplished flex ing twisting Flexbeam Peka W Germany makes two- three- four- five-bladed bearingless main ro tor heads RC Helicopters Unfortu nately however no longer avail able US Both RC full-size bear ingless main rotor systems very difficult design properly Incorrect flexibility Left Close-up big teetering head design installed GMP Hind24 military drone nicknamed MF-1 monster chopper uses dumbbell weights instead Hiller paddles Since Bell control system lacks stabilizer damper Helicopter very stable has slow response isnt aerobatic Above Hinds designer John Gorham preparing lift off helicopter weighs 150 lb has 10-ft-dia rotors powered 350cc gasoline engine Above example Schiuter fixed-pitch S-head introduced Dieter Schluter back 1978 Its articulated ro tor flap hinge offset Right S-head installed authors Schluter Helibaby Hughes 500 body design pro vides much precise control response freely teetering two-bladed main rotor such used full-size Jet Ranger stiffness may result flutter problems ground air resonance reader wishes detailed comparison effects three types rotor heads RC Helicopter per formance referred article RC Ro tor Head Theory June 1989 issue Model Builder magazine article will improve understanding theory behind model Helicopter rotor system two-bladed teetering head design has distinct advantage RC Helicopter appli cations Most Helicopters equipped system because its very simple build set up teetering rotor head hub de signed pivot pin creating teeter ing motion blades inspired its name design will work two bladed system addition RC Helicopter Left Hirobos DDF Dual Dampened Flapping rotor head GMP Stork DDF combines features teetering rotor head articulated flap hinge offset entire hub can teeter about center pin rotor can flap up down individually installation flybar removed experiment didnt work out Right photo shows authors four-bladed hingeless rotor made stacking two Kalt Baron 30 rotor heads setup flies quite well Use two Kalt K4-SB heads 40- 60-size Helicopters April 1990 87 models full-size Bell Jet Ranger UH-l Huey Cobra Gunship feature two bladed teetering rotor designs variation teetering rotor head rigid rotor design hub bolted solidly main rotor shaft pre vent teetering very few full-size helicopters equipped rigid rotor head Lockheed 286 aircraft never reached production stage rigid rotor has advantage su perb almost instantaneous control power pilot feeds cyclic control tilt main rotor disc fuselage re sponds immediately contrast teeter ing rotor gives sluggish cyclic control Since its main rotor disc can tilt re spect main rotor shaft no direct pitch roll moment transferred main rotor fuselage Model Helicopters have overcome problem employing rubber damper 0-ring inside teetering hub As hub teeters rubber functions like spring transmit rotor tilt moment pitch roll fuselage permits RC Helicop ters fancy aerobatics full-size helicopters cannot rubber damper made sufficiently stiff teetering head will behave like rigid rotor head As pilot com presses damper Helicopter re sponds quickly However vibration increases well since its transferred di rectly through hub shaft fuse lage can have adverse effect receiver servos Two originaldesign rigid rotor heads shown some illustra tions Tested GMP Cobra provided su perfast control uncanny imita tion its veno mous namesake Cobra hovers sol idly until re ceives control command leaps out like guided missile Pilots enjoy hot-dogging will probably have fun rigid rotor Just sure youre ballthis machine has raw power F-16 prototype rigid rotor design made cutting GMP Custom head two halves coupling ma chined aluminum hub hub fits tightly over 10mm main rotor shaft However feathering axis two blades must exact alignment found difficult achieve proto type rigid rotor slightest imperfec tion such misalignment being out track imbalance will cause serious vi bration second rigid rotor hub pre cisely machined lathe avoid misalign ment Installed Cobra rotor head eliminated vibration entirely Heli copter flew superbly Although Cobra hovers very well rigid rotor system tends nose up quite severely forward flight Note both rotor heads flybarless creasing blade size 135 grams 160 grams would probably mitigate nose-up tendency Note also GMP flybarless Legend doesnt share nose-up tendency Its stiff-teetering head prevents gust-induced rotor flapback being transmitted fuselage frankly much prefer flying Legend rigid-rotor Cobra Perhaps Im cut out F-16 type flying However mounting set flexible blades Co bra would probably improve its flight per formance considerably blades functioning like stiff hingeless rotor / BO-105 hingeless hub fiberglass blades produced WIK Modelle Germany Intro duced 1970s hingeless rotor equipped single set ball bearings used feathering Major advan tages design minimal parts count its aerodynamically clean profile Cobra should fly better Helicop ters full-size MBB BO-lOS illustrates concept Though has rigid titanium hub four flexible fiberglass blades provide flapping flexibility works better teetering rotor head because theres no teetering slop dead-band teetering pin/roller bearing location Wik Modelle Products West Germany makes Scale BO-lOS rigid hub very flexible fiberglass blades RC Helicop ters understand currently im ported US firm plan try unit publish results GMP Hind-24 drone Helicopter seen two pictures equipped big teetering rotor head Nicknamed MF- 1 chopper uses dumbbell weights instead Continued page 183 88 Model Aviation four-bladed rigid tail rotor hub plate provides excellent tail thrust control unit marketed Victor Dziabczenko David Grabski around $100 Call either detailed technical price information 1-818/341-2159 1 -805/296-0860 Above authors original-design bearingless main rotor head Torlon flex beam incorporated design provides bend ing torsion functions Torlon petroleum-based synthetic prod uct has properties steel costs about 100 times Right aluminum post shown along Torlon flex beams can attached top head support flybar ahilizer achieve smooth level power slight indication turn l turned large left circles power glide mode Gradually increase run time use mall pieces clay weight nose tail r either wing tip achieve perfect light path possible youre com letely satisfied install 5- 6-in-dia lastic prop increase charge time little power needed try 7-inha Peck-Polymers plastic prop trimmed powered properly Falcon will climb very slow re distic rate wide circles 1 /2 ninutes cruise its maximum alti ude short before descending low wide circles gentle landings aIm day near-maximum charges ThE WIlQMATEKTM rhe extra large handle bends 1/8-1/4 coils Si 32-3I1& music wire Wire creep eliminated ur ANTI-KREEP WIRE LOCKIN free catalog also has hardware accessories JOM COMPANY 114 WashIngton Terr Dept Waukegan IL 60085 1st US RIC Flight School Stop Crashing Start Learning CLASSES FILLING FAST Info pack $200 1st US R/C FLIGHT SCHOOL 521 S Sawyer. Shawano WI 54166 t7151 524-2985 Hiller paddles Since Bell control sys tem lacks stabilizer damper Helicop ter stable aerobatic flight 150 lb powered 350cc gasoline en gine very large Helicopter dont want get anywhere near 10-ftdia main rotor MF-l uses 60-size Competitor main rotor blades tail blades Notice pictures Schluter fixedpitch S-head S-head Schluter Helibaby Hughes 500 body system introduced Mr Schluter back 1978 Its two-bladed ar ticulated rotor flap hinge offset confused teetering head rotor Flap hinge offset provides better control re sponse freely teetering two-bladed main rotor such used full-size Jet Ranger Kyoshos new Concept 30 ex ample collective-pitch Helicopter two-bladed flap hinge offset articulated main rotor Another picture shows Hirobos DDF Dual Dampened Flapping head GMP Stork DDF combines features teetering rotor head artic ulated flap hinge offset entire hub can teeter about center pin ro tor blade can flap up down individually result softnesss makes very stable flight characteristics original Hirobo Shuttle introduced 1985 also individual blade flapping design However flapping head overly soft excellent ginners also caused blades strike tail boom hard landings Hirobo rec ognized problem has equipped its Shuttles since 1987 floating axle design similar found Schluter Champion Miniature Aircraft X Cell new head Shuttle both stable aerobatic experiment removed stabi lizer bar assembly see Stork would perform flybarless Helicopter April 1990 183 model will turn breathtaking flights over two minutes glide may resem ble Wakefield Free Flighter can sniff out thermals tempted After Falcon Heli Rotors/Wang Continued page 88 VENO MOUNTS TNE VIBRATION lOLLER Fad end fuel pOaf flee axes ieoiefan fa 25 Ia f 20 an0nea ea-txau F S al S Uslia f ieaalf engfle nouffe Typaai aibfefran reduCtIOn 70% Ma 80% Oft kit COnSIStS OfOuntt isolate Ina pointS seoond 1~~ weetra, iubna jnSfuOtlOnS Sena Sf200 CheCk O Inane OldOt Fe kif OAA PRODUCTS P0 SOS aReas SARASOTA FL 342S3 Sf33774252 FL residents add 72 Caret tax IRFORMATION eand SASS Bob Fiorenzej Hobby Center Inc Dealer Yellow AircraftJLE UPS Orders Shipped Daily Now Available Faatcove coasting Mate,al Visit Showroom 35 win D sney Watidi NEW custow Building Sern Ce 420 WesO SR 434407 327-6383 Winter Springs FL 32708Fax 407 327-7148 3 New ARFs ZMP MONARCH AMA Sport Pattern span 66 area 750 sq motor 4 stroke 90 60 cu Preassembled balsa fuselage vdneered wing shaped balsa pail Lesan canopy epoxy cowl illustrated assembly manual c ZIMPRO MARKETING Pu suuJoltouKxIoGtTS3PSJO PiJOSE 51 axstex found didnt fly well rea son Extra damping quick control re sponse needed tame RC Helicopters much difficult fly full-size counterparts flybarless RC Helicopters depend stiff main rotor head improve vehicles pitch roll damping control power four-bladed hingeless head shown pictures made stacking two Baron 3OMX two-bladed hingeless heads result similar full-size Westland Lynx rotor head steel flexbeam hub gives comparable flap flexibil ity other type hingeless head BO-105 made MBB acquires its flap flexibility through fiberglass blades Wik Modelle also produces BO-105 hingeless hub blades As heads better depends whether youre talk ing Germans British original-design bearingless rotor head uses flexbeam provide bending torsion Its machined special petroleum-based synthetic called Torlon Manufactured Amoco Petroleum Prod ucts Torlon has properties steel costs about 100 times 2-ft-sq piece sells around $700 aluminum post can added top head support flybar shown pic tures friend Joe Medrano expert sheet metalist machined number rotor Sachs Doimar Engines New Torque Customized TG Only 100% SACHS Engine 27All Engines Complete $360 NNothing Buy 31See us 100 TOLEDO Show *40000 37 *43000 42 $46000 add $50 throttlecoupled spark advance Along 27 8 32 lightweight spring start flywheel-type Sachs Dolmar Engine TG MFG 201427-3845 857 HIgh Mtn Rd N Haledon NJ 07508 heads shown photos stamped own Cobra side frames welded rear exhaust muffler Thank Joe Next months sequel will present -scale four-bladed bearingless model ro tor tested Glenn L Martin wind tun nel University Maryland Along million-dollar tunnel youll see some exotic blades swashplates miniature hydraulic servo actuators control sys tems Consortium/Hunt Continued page 104 slight down elevator pick up hold some speed chasing next thermal Ron Farkas built model Ep pIer 201 airfoil its higher weight 3 oz heavier thinner wing version flies just well higher speed Oth ers made Clark Y RAF 32 Ep pIer 193 airfoils scheduled flown soon after article submitted As builder get bored very easily same old construction techniques same old low-wing sport high-wing trainer airplanes Im hobby learn well have fun certainly did both designing Consortium hope reading about project has acquaint ed some new techniques build ing designing model airplanes youve got urge try something differentand little time spend workshopthis classy-looking good-per forming Sailplane will give lot fun small flying field RC Soaring/Blakeslee Continued page 43 museum its displays programs will knock out Make effort joinor visit join t guarantee youll regret either address National Soaring Museum RD#3 Har ris Hill Elmira NY 14903 Thanks Cal Weiss taking time tell us about NSM Im sure model Glider fliers appreciate learning about will plan stop area tn cover letter Cal mentioned tht photos prt vided Shirley Sliwa Director NSM C also passed along personal information am retired NASA Lewis Researe Center Cleveland last 22 3 years directed work Educ tional Services Office Several notable moc elers Chet Lanzo Warren Plohr Reich brothers see Warren occasion club fieldI am member America Airlines Model Club Chet course just rc cently passed away Way back membe Board NAR along John Worth kind establishes Ive fiel bit time fact know few real pros should add fly almost week Jo Elgin designer Playboy makes no bet ter flier models t have active witl RC Gliders five years am having ball managed 1 hr. 15 mm flight oh Windrifter summer Lord t t did kept pulling up kept trying keep sight reasonable alti tude tm interested areas aviation top soaring tt has always fascinated mt just because beauty carries over intc modeling Scale look beauty RC Sailplane much like real thing anything dont like its beautiful Seal model Cub flies what appears super sonic speeds wife also loves sailplanes ant together have attended several Nationals ant regional contests spectators fact las visit museum dedication thi same time Region 3 contest Harris Hill 1 guess natural believi other Sailplane modelers also interested thi full-size ones museum Its reasot put article together Perhaps some mod elers within reach museum will make ths effort visit live too far away perhaps article will interest may wish become members event atr turned want pass information tc others International Postal Challenge Old-time readers column will remember previous re ports Kale Harden Palm Harbor FL IPC idea behind postal contest club several countries fly same contest same day compare results mail sure its interesting fun-fly con cept way meet Sailplaners other countries Kale Pelicans Club St Pete sent reContinued page J& 184 Model Aviation Special Introductory Offer SUKHOI Su-26M15 ScaleIMPALA Masters Pattern span 68 area 890 sq motor 4 stroke 120 equivspan 68 area 800 sq motor 4 stroke 120 60 rear Preassembled lightweight epoxy fuselage sheeted plug-in wingsPreassembled balsa fusefage veneered plug-in wings & stabs sheeted stab fin & rudder 8 dia epoxy cowl Lexan canopy &Epoxy cowl pipe cover removable canopy Illustrated illustrated assembly manualassembly manual see hobby dealer order direct