Mu1ti Bladed Props several reasons switch prop two blades until now wasnt always easy figure out size would good replacement charts formulae included will get started ball park U George F Abbott TWO YEARS AGO wrote article propellers appeared October 1986 issue Model Aviation purpose article give modeler way approximate under static conditions power absorbed propeller given pitch diameter function rpm information could determine power output engine select appropriate propeller particular en gine article pertained con ventional two-bladed props used us Since article appeared have re ceived number inquiries informa tion propellers having either fewer two blades Increasing aware ness noise problem has brought wid ening interest multibladed props Other things being equal such props indeed somewhat quieter Thus may useful provide some simple formulae will per mit selection one- three- four bladed props equivalent traditional two-bladed ones assumed throughout discussion engine power rpm will remain same pitch multi bladed prop will stay same two-bladed prop begin will need know what two-bladed prop best suits engine airplane wish fly multi-bladed prop can deter mined through experience using formu lae provided October 1986 Model Avi ation article recommendations pro vided engine manufacturer aircraft designer Before getting conversion formula may worthwhile discuss advantages disadvantages different types props Advantages multibladed props 1 Increased ground clearance As number blades increases prop diam eter decreases 2 Reduced noise production cause tip velocity propeller di rectly proportional diameter noise produced strongly related tip velocity 3 Reduced vibration generated P ef fect precession 4 Smoother running due im proved flywheel effect resulting larger mass multibladed prop potential disadvantage multi bladed props decreased disc area because smaller diameter may cause some loss efficiency due fact prop influencing smaller column air sort like span loading wing model airplane flying however disadvantage appears minimal ex cept quite low airspeeds propeller rpm larger diameter single-bladed props have found effective application rubber-powered models time time Control Line Speed fliers have also used single-bladed props varying degrees success consistently better everyone would use isnt case Because single-bladed props have used FF Rubber Speed models its probably worthwhile discuss briefly concern maximizing efficiencythat converting energy power plant kinetic energy airplanethe single-bladed propeller may offer some advantage due both larger volume column air propeller influences decreased tip hub drag losses Energy conversion primary impor tance FF rubber-powered duration mod els well CL Speed models Rubber model energy stored rub ber motor converted least possible loss movement air plane same true Speed mo del though its power very dif ferent nature both situations effi ciency crucial Its little like difference efficiency between biplanes monoplanes did last see high-performance Sailplane two sets wings course some practical prob lems construction single-bladed props power models balance weight must provided should small enough fit inside spinner avoid gen erating lot turbulence power loss vicinity hub Also single-bladed props give rise ad ditional vibration because center thrust coaxial propie 44 Model Aviation 0S 90 together 121/2 x 7 Graupner 3-blader destined go authors Sig Astro Hog As three- four-blade props become available serious consideration should given switching no other reason reduction noise levels center prop itself center thrust share common axis thrust vector one-half two-thirds prop radius away center rotating prop speed general think its fair say single-bladed props neither practical nor desirable except very specialized ap plications P effect precession vibration due P effect explained below preces sion probably secondary importance compared produced singlecylinder engines its still worthwhile dis cuss two phenomena sake completeness Also P effect important factor behavior power airplanes no matter blades propel ler find widely misunder stood P effect occurs airplane flying along path parallel axis propeller causing differences gle attack right prop blade versus left prop blade Assume airplane climbing steeply high angle attack Also sume right-handed propeller ing usedone blades descend ing right side airplane cending left Under conditions descending blade will see higher angle attack ascending blade Thus will thrust produced right side propeller disc left Because airplane will tend turn left exactly what hap pens airplanes take off climb out also tail-draggers have tendency swing left during takeoff roll frequently referred erroneously torque effect phenomenon explains twinengine airplanes both full-size model hard handle critical engine left fails Its also contrarotat ing engines often used full-size twins contrarotating engines right-hand en gine has left-hand rotation bringing descending blades closer centerline airplane variability P effect pro duces vibration double- single bladed prop prop blades horizontal position P effect max imum vertical vanishes resultant vibration has frequency twice engine rpm two-bladed prop However single-bladed prop vi bration much greater occurs frequency engine speed multibladed prop P effect still present vibration case four-bladed prop its easy see descending cending blades both sides times reason absence vibration three-bladed props may apparent Without going math involved point blade horizontal other two opposite side angle 600 horizontal posi tion contributing less P effect horizontal position combined effect two equal blade horizontal position vibration effectively canceled Precession familiar gyroscopic ef fect occurs effort made move axis rotating object another source propeller vibration gyro scope will respond moving 900 applied force direction rotation gyroscope rotating propeller gyroscope mass concentrated blades airplane maneuvers direction propeller axis will course change result precession force will gener ated 900 direction caused ma neuver airplane executing loop example force precession will tend turn right conventional airplanes today effect very notice able rotary engines widely used World War signifi cant due great rotating mass such engines Sopwith Camel particu larly nasty reputation regard see Pro file Publications No 31 Because mass propeller blades precession effect maximum blades parallel direction August 1988 45 Table 1 N D 11189 2100 3908 4 84 5795 N ades D %of2Blade diameter single-bladded prop commercially available 35 40 years ago Its shown attached 1947 McCoy 60 Notice counterweight has shaped fit inside spinner reduce hub drag Clockwise top 9 x 6 Tornado Girsh Bros 12 x 7 Graupner 5 x 3 Cox Other manufacturers have begun producing multi-bladed props check lo cal hobby shop model mag advertisements get up-to-date idea whats available m Radio trouble? Hobby Radio NC offers professional RC repairs modifications make RIC equipment produced last 25 years Complete system service battery pack servos vibration testing new frequency change etc Also R/Cer likes do-it-yourself Mobby Radio Volume 1 142 page journal including diagrams charts detailed modifications written simple understandable text Send $1995 Hobby Radio NC 401 Lillian Rd Wihon NC 27893 Send legal-size SASE price list complete services YOUR R/C SPECIALIST 919 291a548 change airplanes attitude prop perpendicular direc tion change effect zerothat disappears Thus case ioop de scribed above precession forces will maximum blades vertical minimum horizontal Vibra tion created precession forces go maximum minimum twice en gine rpm As remarked beginning sec tion may question just important vibration effects model air planes given very high vibration levels generated single-cylinder engines point however mitigation pre cession HTItI P effect contributes smoother running obtained multibladed props Equivalent sizes proper size two-bladed propeller known Table 1 will provide equivalent diameters three four blades Regardless number blades use same pitch used two-bladed prop appropriate two-bladed propeller size taken reference D given percentage two-blade diameter Thus example 10 x 6 prop 10-in diameter 6-in pitch indicated its equivalent would either three-bladed prop 93-in diameter 6-in pitch four-bladed prop 84 diam eter pitch 6 believe would reasonable round off near est ler sizes up 10 nearest /2 larger sizes course prop selection always matter experimentation get just right combi nation engine plane prop pilot pref erence Table 2 lists some common prop sizes used today RC equivalent threeand four-blade sizes have rounded nearest ry behind quite straightfor ward assumed blade contri butes equally power absorbed propeller well thrust produ ces recall propeller article October 1986 Model Aviation gave mula power absorption assuming two bladed props hp rpm3/l4x107 P h D eter both inches Now assume power pitch rpm unchanged also assume blade contributes equally power absorbed prop Thus blade quantity D4 would one-half two blades three blades quantity would one-and-one-half two blades etc Now write fol lowing expression relates diame Continued page 140 46 Model Aviation HOBBY RADIO NC I622 CD Wildcat Classic Glass Grumman KIT FEATURES Polyester fiberglass fusalage cowling retractable landing 92 wingspan gear Foam cores wing stab Available major production variations F4F-3 -3A -4 FM-i FM-2 Semi-Kit Fusalage cowling foam cores wing stab canopy retractable landing gear plans 7500 Complete Kit Everything listed semi-kit plus wood parts hardware necessary complete kit including 1/64 plywood sheeting wings$45000 Deluxe Kit Complete kit fusalage preassembled$85000 wings stab presheeted control surfaces prebuilt add $15 00 shipping Information Package Si 00 VISA/MasterCard acceptedIdaho ras add 5% sales tax Mike Zamber Classic Glass PO Box 503 Blackfoot Idaho 83221-0503 85-2309 FULL BODY PILOT KIT Contains pilot head handa boota helmet cap goggles full templates easy instruc tions Easy assemble finish Some simple sewing required Fully positionable too Prke #2061/6 scale 895 #205-Vs scale 995 #204-/6 scale1095 #2031/3 scale1695 DARNED GOOD AIRMEN Lightest pilots available Lifelike vinyl latex rubber Build Sportsman Barnstormer Full Body Bust - BUST PILOT KIT Contains pilot head helmet sport cap goggles jacket Easy assemble finish Ptoe #108-A scale NEW 595 #106-V6 scale695 #l05-Vs scale #104- scale. 895Some #103-V3 scale 1495 S mp e sew ng equ ed can estimate long should take pump up pack Just divide nominal capac ity hy charging rate multiply result 60 minutes/hour Simplifying math 3% cell capacity mAh equals charge time minutes 03 x mAh ge time minutes times interest Ni-Cds mAh 250 500 900 1200 minutes7515 2736 Lead-acid cells gel-cells Ah612 hours3 6 So use watch monitor long charging has going charger has shut off early push Start button again worried about overcharging feel pack cool safe push Start ton fact time pack cool VR light isnt glowing push Start button Ace R/C Overnighter set Ni-Cd charging instructions says same thing Charge 24 hours using charger provided before using device charge overnight 14 hours least monthly necessary advice because Ni-Cd cells have form abil ity hold charge happens slowly can successful fast charger af ter cells have formed So does leave TRC times want Set forget ie slow charge overnight dont want sit stopwatch mon ttor charging process times am bringing along palm-sized Ace R/C Over nighter plugs vans 12-VDC cigar lighter side two transmitters two receiver packs other Charging pro ceeds 14-hour rate whether van engine running stopped can useful cause TRC Fast Charger instructions specifi cally prohibit use engine running Overnighter voltage-regulated constant-current charger can internally programmed charge battery packs mAh ratings 250 500 900 1200 takes almost no room contained rugged metal case tt gets job done What can ask Ace R/C Overnighter kit 34K50 $2495 assem bled unit 34K50C $3395 Ace R/C Inc Box 51 IE Higginsville MO 64037 816 5847121 know what thinking now handle special charging plugs Very simple cut off put back JET PILOT KIT Pilot has molded jet helmet Contains face mask oxygen hose Estreme ly Realistic Weighs less oz P616 #308/ scale 595 #307-/ scale 695 ORDERING INSTRUCTIONS See dealer first order direct Add $100 shipping NYS residents add 7O/ tax Send check money order CODS OK Send $100 catalog Deans connectors available Ace R/C above have take along special connectornot whole 110VAC charger monitor whats going have Accu tach 2A described column April 1988 issue universal adapter Ugly Octopus described column March 1982 issue electronic repairs Ill carry Portasol soldering iron see February 1988 co lumn Well thats month know what plan about charging batteries Dont expect quick answers letters next few months because wont receiving mail sold house son Im off see world See Dealer add Dollar direct Ofder handling Throwing blade can real disaster due danger thrown blade also damage air plane would caused enormous vibration would result Substantial tor sional stresses encountered propel ler largely hub due great torque variations single-cylinder engines worse four-cycle engines poorly designed prop bomb wait ing go off advice keep eye open local hobby shop watch magazine ads manufacturers jump bandwagon offer quieter now sought-after multi bladed props Multi-Blade Props/AbbottRC Electrics/Kopski Continued page 46Continued page 49 lers various numbers blades di ameter two blades 25 Dn/D2 n er blades D2diameter two-bladed prop Dn eter prop n blades Plugging numbers expression provides values given table Whats available great majority commercially available props two bladed variety four major prop manufacturers known offer three bladed props Grish Tornado Cox Graupner make plastic/nylon props Zen gali makes black fiber-filled variety smaller sizes wooden props larger sizes Cox offers small three-bladers 51 range Grish offers three-bladers sizes up 10 Graupner offers larger props starting 9 going up 16 Zengali currently offering fiberfilled three-bladed props sizes 8 9 10 x 6 lOx 75 10 x 8 wooden threeor four-bladed props range diameter 13 28 Check local hobby shop find out whats currently available Its out question make own three- four-bladed props better really know what doing heck second thought just drink stuff glassware insteadits gotta fun Some Electric trivia brought mind looked back August 85 issue above reference column contained photo Astro Flights Bob Bouchers then-new Challengera very competent Electric Sailplane happens just finished flew new Challenger two days ago brought back viv id memories Bobs Bob brought 1984 KRC Electric Fly Yup way California gave opportunity fly fair Bob course because night before called desperation after just arriving East Coast seems Challenger found full-scale skies less friendly wing wound up some tears Mono Kote late Friday night evening before meet Bob very much needed some red transparent film patch things up Luckily brand new roll able accommodate Bob wing Jim ZarembskiRCM former Electric columnist too shop Now happens that roll MonoKote few square inches missingsaw no further use til last week Thats cover ing new Challenger Yup West Coast Bob East Coast Bob now have Challenger wings covering exactly same roll Mono Kote Hows some Electric trivia Anyway has explosion sorts Challenger population locality dur ing past six months effect went four during period 140 Model Aviation
Edition: Model Aviation - 1988/08
Page Numbers: 44, 45, 46, 140
Mu1ti Bladed Props several reasons switch prop two blades until now wasnt always easy figure out size would good replacement charts formulae included will get started ball park U George F Abbott TWO YEARS AGO wrote article propellers appeared October 1986 issue Model Aviation purpose article give modeler way approximate under static conditions power absorbed propeller given pitch diameter function rpm information could determine power output engine select appropriate propeller particular en gine article pertained con ventional two-bladed props used us Since article appeared have re ceived number inquiries informa tion propellers having either fewer two blades Increasing aware ness noise problem has brought wid ening interest multibladed props Other things being equal such props indeed somewhat quieter Thus may useful provide some simple formulae will per mit selection one- three- four bladed props equivalent traditional two-bladed ones assumed throughout discussion engine power rpm will remain same pitch multi bladed prop will stay same two-bladed prop begin will need know what two-bladed prop best suits engine airplane wish fly multi-bladed prop can deter mined through experience using formu lae provided October 1986 Model Avi ation article recommendations pro vided engine manufacturer aircraft designer Before getting conversion formula may worthwhile discuss advantages disadvantages different types props Advantages multibladed props 1 Increased ground clearance As number blades increases prop diam eter decreases 2 Reduced noise production cause tip velocity propeller di rectly proportional diameter noise produced strongly related tip velocity 3 Reduced vibration generated P ef fect precession 4 Smoother running due im proved flywheel effect resulting larger mass multibladed prop potential disadvantage multi bladed props decreased disc area because smaller diameter may cause some loss efficiency due fact prop influencing smaller column air sort like span loading wing model airplane flying however disadvantage appears minimal ex cept quite low airspeeds propeller rpm larger diameter single-bladed props have found effective application rubber-powered models time time Control Line Speed fliers have also used single-bladed props varying degrees success consistently better everyone would use isnt case Because single-bladed props have used FF Rubber Speed models its probably worthwhile discuss briefly concern maximizing efficiencythat converting energy power plant kinetic energy airplanethe single-bladed propeller may offer some advantage due both larger volume column air propeller influences decreased tip hub drag losses Energy conversion primary impor tance FF rubber-powered duration mod els well CL Speed models Rubber model energy stored rub ber motor converted least possible loss movement air plane same true Speed mo del though its power very dif ferent nature both situations effi ciency crucial Its little like difference efficiency between biplanes monoplanes did last see high-performance Sailplane two sets wings course some practical prob lems construction single-bladed props power models balance weight must provided should small enough fit inside spinner avoid gen erating lot turbulence power loss vicinity hub Also single-bladed props give rise ad ditional vibration because center thrust coaxial propie 44 Model Aviation 0S 90 together 121/2 x 7 Graupner 3-blader destined go authors Sig Astro Hog As three- four-blade props become available serious consideration should given switching no other reason reduction noise levels center prop itself center thrust share common axis thrust vector one-half two-thirds prop radius away center rotating prop speed general think its fair say single-bladed props neither practical nor desirable except very specialized ap plications P effect precession vibration due P effect explained below preces sion probably secondary importance compared produced singlecylinder engines its still worthwhile dis cuss two phenomena sake completeness Also P effect important factor behavior power airplanes no matter blades propel ler find widely misunder stood P effect occurs airplane flying along path parallel axis propeller causing differences gle attack right prop blade versus left prop blade Assume airplane climbing steeply high angle attack Also sume right-handed propeller ing usedone blades descend ing right side airplane cending left Under conditions descending blade will see higher angle attack ascending blade Thus will thrust produced right side propeller disc left Because airplane will tend turn left exactly what hap pens airplanes take off climb out also tail-draggers have tendency swing left during takeoff roll frequently referred erroneously torque effect phenomenon explains twinengine airplanes both full-size model hard handle critical engine left fails Its also contrarotat ing engines often used full-size twins contrarotating engines right-hand en gine has left-hand rotation bringing descending blades closer centerline airplane variability P effect pro duces vibration double- single bladed prop prop blades horizontal position P effect max imum vertical vanishes resultant vibration has frequency twice engine rpm two-bladed prop However single-bladed prop vi bration much greater occurs frequency engine speed multibladed prop P effect still present vibration case four-bladed prop its easy see descending cending blades both sides times reason absence vibration three-bladed props may apparent Without going math involved point blade horizontal other two opposite side angle 600 horizontal posi tion contributing less P effect horizontal position combined effect two equal blade horizontal position vibration effectively canceled Precession familiar gyroscopic ef fect occurs effort made move axis rotating object another source propeller vibration gyro scope will respond moving 900 applied force direction rotation gyroscope rotating propeller gyroscope mass concentrated blades airplane maneuvers direction propeller axis will course change result precession force will gener ated 900 direction caused ma neuver airplane executing loop example force precession will tend turn right conventional airplanes today effect very notice able rotary engines widely used World War signifi cant due great rotating mass such engines Sopwith Camel particu larly nasty reputation regard see Pro file Publications No 31 Because mass propeller blades precession effect maximum blades parallel direction August 1988 45 Table 1 N D 11189 2100 3908 4 84 5795 N ades D %of2Blade diameter single-bladded prop commercially available 35 40 years ago Its shown attached 1947 McCoy 60 Notice counterweight has shaped fit inside spinner reduce hub drag Clockwise top 9 x 6 Tornado Girsh Bros 12 x 7 Graupner 5 x 3 Cox Other manufacturers have begun producing multi-bladed props check lo cal hobby shop model mag advertisements get up-to-date idea whats available m Radio trouble? Hobby Radio NC offers professional RC repairs modifications make RIC equipment produced last 25 years Complete system service battery pack servos vibration testing new frequency change etc Also R/Cer likes do-it-yourself Mobby Radio Volume 1 142 page journal including diagrams charts detailed modifications written simple understandable text Send $1995 Hobby Radio NC 401 Lillian Rd Wihon NC 27893 Send legal-size SASE price list complete services YOUR R/C SPECIALIST 919 291a548 change airplanes attitude prop perpendicular direc tion change effect zerothat disappears Thus case ioop de scribed above precession forces will maximum blades vertical minimum horizontal Vibra tion created precession forces go maximum minimum twice en gine rpm As remarked beginning sec tion may question just important vibration effects model air planes given very high vibration levels generated single-cylinder engines point however mitigation pre cession HTItI P effect contributes smoother running obtained multibladed props Equivalent sizes proper size two-bladed propeller known Table 1 will provide equivalent diameters three four blades Regardless number blades use same pitch used two-bladed prop appropriate two-bladed propeller size taken reference D given percentage two-blade diameter Thus example 10 x 6 prop 10-in diameter 6-in pitch indicated its equivalent would either three-bladed prop 93-in diameter 6-in pitch four-bladed prop 84 diam eter pitch 6 believe would reasonable round off near est ler sizes up 10 nearest /2 larger sizes course prop selection always matter experimentation get just right combi nation engine plane prop pilot pref erence Table 2 lists some common prop sizes used today RC equivalent threeand four-blade sizes have rounded nearest ry behind quite straightfor ward assumed blade contri butes equally power absorbed propeller well thrust produ ces recall propeller article October 1986 Model Aviation gave mula power absorption assuming two bladed props hp rpm3/l4x107 P h D eter both inches Now assume power pitch rpm unchanged also assume blade contributes equally power absorbed prop Thus blade quantity D4 would one-half two blades three blades quantity would one-and-one-half two blades etc Now write fol lowing expression relates diame Continued page 140 46 Model Aviation HOBBY RADIO NC I622 CD Wildcat Classic Glass Grumman KIT FEATURES Polyester fiberglass fusalage cowling retractable landing 92 wingspan gear Foam cores wing stab Available major production variations F4F-3 -3A -4 FM-i FM-2 Semi-Kit Fusalage cowling foam cores wing stab canopy retractable landing gear plans 7500 Complete Kit Everything listed semi-kit plus wood parts hardware necessary complete kit including 1/64 plywood sheeting wings$45000 Deluxe Kit Complete kit fusalage preassembled$85000 wings stab presheeted control surfaces prebuilt add $15 00 shipping Information Package Si 00 VISA/MasterCard acceptedIdaho ras add 5% sales tax Mike Zamber Classic Glass PO Box 503 Blackfoot Idaho 83221-0503 85-2309 FULL BODY PILOT KIT Contains pilot head handa boota helmet cap goggles full templates easy instruc tions Easy assemble finish Some simple sewing required Fully positionable too Prke #2061/6 scale 895 #205-Vs scale 995 #204-/6 scale1095 #2031/3 scale1695 DARNED GOOD AIRMEN Lightest pilots available Lifelike vinyl latex rubber Build Sportsman Barnstormer Full Body Bust - BUST PILOT KIT Contains pilot head helmet sport cap goggles jacket Easy assemble finish Ptoe #108-A scale NEW 595 #106-V6 scale695 #l05-Vs scale #104- scale. 895Some #103-V3 scale 1495 S mp e sew ng equ ed can estimate long should take pump up pack Just divide nominal capac ity hy charging rate multiply result 60 minutes/hour Simplifying math 3% cell capacity mAh equals charge time minutes 03 x mAh ge time minutes times interest Ni-Cds mAh 250 500 900 1200 minutes7515 2736 Lead-acid cells gel-cells Ah612 hours3 6 So use watch monitor long charging has going charger has shut off early push Start button again worried about overcharging feel pack cool safe push Start ton fact time pack cool VR light isnt glowing push Start button Ace R/C Overnighter set Ni-Cd charging instructions says same thing Charge 24 hours using charger provided before using device charge overnight 14 hours least monthly necessary advice because Ni-Cd cells have form abil ity hold charge happens slowly can successful fast charger af ter cells have formed So does leave TRC times want Set forget ie slow charge overnight dont want sit stopwatch mon ttor charging process times am bringing along palm-sized Ace R/C Over nighter plugs vans 12-VDC cigar lighter side two transmitters two receiver packs other Charging pro ceeds 14-hour rate whether van engine running stopped can useful cause TRC Fast Charger instructions specifi cally prohibit use engine running Overnighter voltage-regulated constant-current charger can internally programmed charge battery packs mAh ratings 250 500 900 1200 takes almost no room contained rugged metal case tt gets job done What can ask Ace R/C Overnighter kit 34K50 $2495 assem bled unit 34K50C $3395 Ace R/C Inc Box 51 IE Higginsville MO 64037 816 5847121 know what thinking now handle special charging plugs Very simple cut off put back JET PILOT KIT Pilot has molded jet helmet Contains face mask oxygen hose Estreme ly Realistic Weighs less oz P616 #308/ scale 595 #307-/ scale 695 ORDERING INSTRUCTIONS See dealer first order direct Add $100 shipping NYS residents add 7O/ tax Send check money order CODS OK Send $100 catalog Deans connectors available Ace R/C above have take along special connectornot whole 110VAC charger monitor whats going have Accu tach 2A described column April 1988 issue universal adapter Ugly Octopus described column March 1982 issue electronic repairs Ill carry Portasol soldering iron see February 1988 co lumn Well thats month know what plan about charging batteries Dont expect quick answers letters next few months because wont receiving mail sold house son Im off see world See Dealer add Dollar direct Ofder handling Throwing blade can real disaster due danger thrown blade also damage air plane would caused enormous vibration would result Substantial tor sional stresses encountered propel ler largely hub due great torque variations single-cylinder engines worse four-cycle engines poorly designed prop bomb wait ing go off advice keep eye open local hobby shop watch magazine ads manufacturers jump bandwagon offer quieter now sought-after multi bladed props Multi-Blade Props/AbbottRC Electrics/Kopski Continued page 46Continued page 49 lers various numbers blades di ameter two blades 25 Dn/D2 n er blades D2diameter two-bladed prop Dn eter prop n blades Plugging numbers expression provides values given table Whats available great majority commercially available props two bladed variety four major prop manufacturers known offer three bladed props Grish Tornado Cox Graupner make plastic/nylon props Zen gali makes black fiber-filled variety smaller sizes wooden props larger sizes Cox offers small three-bladers 51 range Grish offers three-bladers sizes up 10 Graupner offers larger props starting 9 going up 16 Zengali currently offering fiberfilled three-bladed props sizes 8 9 10 x 6 lOx 75 10 x 8 wooden threeor four-bladed props range diameter 13 28 Check local hobby shop find out whats currently available Its out question make own three- four-bladed props better really know what doing heck second thought just drink stuff glassware insteadits gotta fun Some Electric trivia brought mind looked back August 85 issue above reference column contained photo Astro Flights Bob Bouchers then-new Challengera very competent Electric Sailplane happens just finished flew new Challenger two days ago brought back viv id memories Bobs Bob brought 1984 KRC Electric Fly Yup way California gave opportunity fly fair Bob course because night before called desperation after just arriving East Coast seems Challenger found full-scale skies less friendly wing wound up some tears Mono Kote late Friday night evening before meet Bob very much needed some red transparent film patch things up Luckily brand new roll able accommodate Bob wing Jim ZarembskiRCM former Electric columnist too shop Now happens that roll MonoKote few square inches missingsaw no further use til last week Thats cover ing new Challenger Yup West Coast Bob East Coast Bob now have Challenger wings covering exactly same roll Mono Kote Hows some Electric trivia Anyway has explosion sorts Challenger population locality dur ing past six months effect went four during period 140 Model Aviation
Edition: Model Aviation - 1988/08
Page Numbers: 44, 45, 46, 140
Mu1ti Bladed Props several reasons switch prop two blades until now wasnt always easy figure out size would good replacement charts formulae included will get started ball park U George F Abbott TWO YEARS AGO wrote article propellers appeared October 1986 issue Model Aviation purpose article give modeler way approximate under static conditions power absorbed propeller given pitch diameter function rpm information could determine power output engine select appropriate propeller particular en gine article pertained con ventional two-bladed props used us Since article appeared have re ceived number inquiries informa tion propellers having either fewer two blades Increasing aware ness noise problem has brought wid ening interest multibladed props Other things being equal such props indeed somewhat quieter Thus may useful provide some simple formulae will per mit selection one- three- four bladed props equivalent traditional two-bladed ones assumed throughout discussion engine power rpm will remain same pitch multi bladed prop will stay same two-bladed prop begin will need know what two-bladed prop best suits engine airplane wish fly multi-bladed prop can deter mined through experience using formu lae provided October 1986 Model Avi ation article recommendations pro vided engine manufacturer aircraft designer Before getting conversion formula may worthwhile discuss advantages disadvantages different types props Advantages multibladed props 1 Increased ground clearance As number blades increases prop diam eter decreases 2 Reduced noise production cause tip velocity propeller di rectly proportional diameter noise produced strongly related tip velocity 3 Reduced vibration generated P ef fect precession 4 Smoother running due im proved flywheel effect resulting larger mass multibladed prop potential disadvantage multi bladed props decreased disc area because smaller diameter may cause some loss efficiency due fact prop influencing smaller column air sort like span loading wing model airplane flying however disadvantage appears minimal ex cept quite low airspeeds propeller rpm larger diameter single-bladed props have found effective application rubber-powered models time time Control Line Speed fliers have also used single-bladed props varying degrees success consistently better everyone would use isnt case Because single-bladed props have used FF Rubber Speed models its probably worthwhile discuss briefly concern maximizing efficiencythat converting energy power plant kinetic energy airplanethe single-bladed propeller may offer some advantage due both larger volume column air propeller influences decreased tip hub drag losses Energy conversion primary impor tance FF rubber-powered duration mod els well CL Speed models Rubber model energy stored rub ber motor converted least possible loss movement air plane same true Speed mo del though its power very dif ferent nature both situations effi ciency crucial Its little like difference efficiency between biplanes monoplanes did last see high-performance Sailplane two sets wings course some practical prob lems construction single-bladed props power models balance weight must provided should small enough fit inside spinner avoid gen erating lot turbulence power loss vicinity hub Also single-bladed props give rise ad ditional vibration because center thrust coaxial propie 44 Model Aviation 0S 90 together 121/2 x 7 Graupner 3-blader destined go authors Sig Astro Hog As three- four-blade props become available serious consideration should given switching no other reason reduction noise levels center prop itself center thrust share common axis thrust vector one-half two-thirds prop radius away center rotating prop speed general think its fair say single-bladed props neither practical nor desirable except very specialized ap plications P effect precession vibration due P effect explained below preces sion probably secondary importance compared produced singlecylinder engines its still worthwhile dis cuss two phenomena sake completeness Also P effect important factor behavior power airplanes no matter blades propel ler find widely misunder stood P effect occurs airplane flying along path parallel axis propeller causing differences gle attack right prop blade versus left prop blade Assume airplane climbing steeply high angle attack Also sume right-handed propeller ing usedone blades descend ing right side airplane cending left Under conditions descending blade will see higher angle attack ascending blade Thus will thrust produced right side propeller disc left Because airplane will tend turn left exactly what hap pens airplanes take off climb out also tail-draggers have tendency swing left during takeoff roll frequently referred erroneously torque effect phenomenon explains twinengine airplanes both full-size model hard handle critical engine left fails Its also contrarotat ing engines often used full-size twins contrarotating engines right-hand en gine has left-hand rotation bringing descending blades closer centerline airplane variability P effect pro duces vibration double- single bladed prop prop blades horizontal position P effect max imum vertical vanishes resultant vibration has frequency twice engine rpm two-bladed prop However single-bladed prop vi bration much greater occurs frequency engine speed multibladed prop P effect still present vibration case four-bladed prop its easy see descending cending blades both sides times reason absence vibration three-bladed props may apparent Without going math involved point blade horizontal other two opposite side angle 600 horizontal posi tion contributing less P effect horizontal position combined effect two equal blade horizontal position vibration effectively canceled Precession familiar gyroscopic ef fect occurs effort made move axis rotating object another source propeller vibration gyro scope will respond moving 900 applied force direction rotation gyroscope rotating propeller gyroscope mass concentrated blades airplane maneuvers direction propeller axis will course change result precession force will gener ated 900 direction caused ma neuver airplane executing loop example force precession will tend turn right conventional airplanes today effect very notice able rotary engines widely used World War signifi cant due great rotating mass such engines Sopwith Camel particu larly nasty reputation regard see Pro file Publications No 31 Because mass propeller blades precession effect maximum blades parallel direction August 1988 45 Table 1 N D 11189 2100 3908 4 84 5795 N ades D %of2Blade diameter single-bladded prop commercially available 35 40 years ago Its shown attached 1947 McCoy 60 Notice counterweight has shaped fit inside spinner reduce hub drag Clockwise top 9 x 6 Tornado Girsh Bros 12 x 7 Graupner 5 x 3 Cox Other manufacturers have begun producing multi-bladed props check lo cal hobby shop model mag advertisements get up-to-date idea whats available m Radio trouble? Hobby Radio NC offers professional RC repairs modifications make RIC equipment produced last 25 years Complete system service battery pack servos vibration testing new frequency change etc Also R/Cer likes do-it-yourself Mobby Radio Volume 1 142 page journal including diagrams charts detailed modifications written simple understandable text Send $1995 Hobby Radio NC 401 Lillian Rd Wihon NC 27893 Send legal-size SASE price list complete services YOUR R/C SPECIALIST 919 291a548 change airplanes attitude prop perpendicular direc tion change effect zerothat disappears Thus case ioop de scribed above precession forces will maximum blades vertical minimum horizontal Vibra tion created precession forces go maximum minimum twice en gine rpm As remarked beginning sec tion may question just important vibration effects model air planes given very high vibration levels generated single-cylinder engines point however mitigation pre cession HTItI P effect contributes smoother running obtained multibladed props Equivalent sizes proper size two-bladed propeller known Table 1 will provide equivalent diameters three four blades Regardless number blades use same pitch used two-bladed prop appropriate two-bladed propeller size taken reference D given percentage two-blade diameter Thus example 10 x 6 prop 10-in diameter 6-in pitch indicated its equivalent would either three-bladed prop 93-in diameter 6-in pitch four-bladed prop 84 diam eter pitch 6 believe would reasonable round off near est ler sizes up 10 nearest /2 larger sizes course prop selection always matter experimentation get just right combi nation engine plane prop pilot pref erence Table 2 lists some common prop sizes used today RC equivalent threeand four-blade sizes have rounded nearest ry behind quite straightfor ward assumed blade contri butes equally power absorbed propeller well thrust produ ces recall propeller article October 1986 Model Aviation gave mula power absorption assuming two bladed props hp rpm3/l4x107 P h D eter both inches Now assume power pitch rpm unchanged also assume blade contributes equally power absorbed prop Thus blade quantity D4 would one-half two blades three blades quantity would one-and-one-half two blades etc Now write fol lowing expression relates diame Continued page 140 46 Model Aviation HOBBY RADIO NC I622 CD Wildcat Classic Glass Grumman KIT FEATURES Polyester fiberglass fusalage cowling retractable landing 92 wingspan gear Foam cores wing stab Available major production variations F4F-3 -3A -4 FM-i FM-2 Semi-Kit Fusalage cowling foam cores wing stab canopy retractable landing gear plans 7500 Complete Kit Everything listed semi-kit plus wood parts hardware necessary complete kit including 1/64 plywood sheeting wings$45000 Deluxe Kit Complete kit fusalage preassembled$85000 wings stab presheeted control surfaces prebuilt add $15 00 shipping Information Package Si 00 VISA/MasterCard acceptedIdaho ras add 5% sales tax Mike Zamber Classic Glass PO Box 503 Blackfoot Idaho 83221-0503 85-2309 FULL BODY PILOT KIT Contains pilot head handa boota helmet cap goggles full templates easy instruc tions Easy assemble finish Some simple sewing required Fully positionable too Prke #2061/6 scale 895 #205-Vs scale 995 #204-/6 scale1095 #2031/3 scale1695 DARNED GOOD AIRMEN Lightest pilots available Lifelike vinyl latex rubber Build Sportsman Barnstormer Full Body Bust - BUST PILOT KIT Contains pilot head helmet sport cap goggles jacket Easy assemble finish Ptoe #108-A scale NEW 595 #106-V6 scale695 #l05-Vs scale #104- scale. 895Some #103-V3 scale 1495 S mp e sew ng equ ed can estimate long should take pump up pack Just divide nominal capac ity hy charging rate multiply result 60 minutes/hour Simplifying math 3% cell capacity mAh equals charge time minutes 03 x mAh ge time minutes times interest Ni-Cds mAh 250 500 900 1200 minutes7515 2736 Lead-acid cells gel-cells Ah612 hours3 6 So use watch monitor long charging has going charger has shut off early push Start button again worried about overcharging feel pack cool safe push Start ton fact time pack cool VR light isnt glowing push Start button Ace R/C Overnighter set Ni-Cd charging instructions says same thing Charge 24 hours using charger provided before using device charge overnight 14 hours least monthly necessary advice because Ni-Cd cells have form abil ity hold charge happens slowly can successful fast charger af ter cells have formed So does leave TRC times want Set forget ie slow charge overnight dont want sit stopwatch mon ttor charging process times am bringing along palm-sized Ace R/C Over nighter plugs vans 12-VDC cigar lighter side two transmitters two receiver packs other Charging pro ceeds 14-hour rate whether van engine running stopped can useful cause TRC Fast Charger instructions specifi cally prohibit use engine running Overnighter voltage-regulated constant-current charger can internally programmed charge battery packs mAh ratings 250 500 900 1200 takes almost no room contained rugged metal case tt gets job done What can ask Ace R/C Overnighter kit 34K50 $2495 assem bled unit 34K50C $3395 Ace R/C Inc Box 51 IE Higginsville MO 64037 816 5847121 know what thinking now handle special charging plugs Very simple cut off put back JET PILOT KIT Pilot has molded jet helmet Contains face mask oxygen hose Estreme ly Realistic Weighs less oz P616 #308/ scale 595 #307-/ scale 695 ORDERING INSTRUCTIONS See dealer first order direct Add $100 shipping NYS residents add 7O/ tax Send check money order CODS OK Send $100 catalog Deans connectors available Ace R/C above have take along special connectornot whole 110VAC charger monitor whats going have Accu tach 2A described column April 1988 issue universal adapter Ugly Octopus described column March 1982 issue electronic repairs Ill carry Portasol soldering iron see February 1988 co lumn Well thats month know what plan about charging batteries Dont expect quick answers letters next few months because wont receiving mail sold house son Im off see world See Dealer add Dollar direct Ofder handling Throwing blade can real disaster due danger thrown blade also damage air plane would caused enormous vibration would result Substantial tor sional stresses encountered propel ler largely hub due great torque variations single-cylinder engines worse four-cycle engines poorly designed prop bomb wait ing go off advice keep eye open local hobby shop watch magazine ads manufacturers jump bandwagon offer quieter now sought-after multi bladed props Multi-Blade Props/AbbottRC Electrics/Kopski Continued page 46Continued page 49 lers various numbers blades di ameter two blades 25 Dn/D2 n er blades D2diameter two-bladed prop Dn eter prop n blades Plugging numbers expression provides values given table Whats available great majority commercially available props two bladed variety four major prop manufacturers known offer three bladed props Grish Tornado Cox Graupner make plastic/nylon props Zen gali makes black fiber-filled variety smaller sizes wooden props larger sizes Cox offers small three-bladers 51 range Grish offers three-bladers sizes up 10 Graupner offers larger props starting 9 going up 16 Zengali currently offering fiberfilled three-bladed props sizes 8 9 10 x 6 lOx 75 10 x 8 wooden threeor four-bladed props range diameter 13 28 Check local hobby shop find out whats currently available Its out question make own three- four-bladed props better really know what doing heck second thought just drink stuff glassware insteadits gotta fun Some Electric trivia brought mind looked back August 85 issue above reference column contained photo Astro Flights Bob Bouchers then-new Challengera very competent Electric Sailplane happens just finished flew new Challenger two days ago brought back viv id memories Bobs Bob brought 1984 KRC Electric Fly Yup way California gave opportunity fly fair Bob course because night before called desperation after just arriving East Coast seems Challenger found full-scale skies less friendly wing wound up some tears Mono Kote late Friday night evening before meet Bob very much needed some red transparent film patch things up Luckily brand new roll able accommodate Bob wing Jim ZarembskiRCM former Electric columnist too shop Now happens that roll MonoKote few square inches missingsaw no further use til last week Thats cover ing new Challenger Yup West Coast Bob East Coast Bob now have Challenger wings covering exactly same roll Mono Kote Hows some Electric trivia Anyway has explosion sorts Challenger population locality dur ing past six months effect went four during period 140 Model Aviation
Edition: Model Aviation - 1988/08
Page Numbers: 44, 45, 46, 140
Mu1ti Bladed Props several reasons switch prop two blades until now wasnt always easy figure out size would good replacement charts formulae included will get started ball park U George F Abbott TWO YEARS AGO wrote article propellers appeared October 1986 issue Model Aviation purpose article give modeler way approximate under static conditions power absorbed propeller given pitch diameter function rpm information could determine power output engine select appropriate propeller particular en gine article pertained con ventional two-bladed props used us Since article appeared have re ceived number inquiries informa tion propellers having either fewer two blades Increasing aware ness noise problem has brought wid ening interest multibladed props Other things being equal such props indeed somewhat quieter Thus may useful provide some simple formulae will per mit selection one- three- four bladed props equivalent traditional two-bladed ones assumed throughout discussion engine power rpm will remain same pitch multi bladed prop will stay same two-bladed prop begin will need know what two-bladed prop best suits engine airplane wish fly multi-bladed prop can deter mined through experience using formu lae provided October 1986 Model Avi ation article recommendations pro vided engine manufacturer aircraft designer Before getting conversion formula may worthwhile discuss advantages disadvantages different types props Advantages multibladed props 1 Increased ground clearance As number blades increases prop diam eter decreases 2 Reduced noise production cause tip velocity propeller di rectly proportional diameter noise produced strongly related tip velocity 3 Reduced vibration generated P ef fect precession 4 Smoother running due im proved flywheel effect resulting larger mass multibladed prop potential disadvantage multi bladed props decreased disc area because smaller diameter may cause some loss efficiency due fact prop influencing smaller column air sort like span loading wing model airplane flying however disadvantage appears minimal ex cept quite low airspeeds propeller rpm larger diameter single-bladed props have found effective application rubber-powered models time time Control Line Speed fliers have also used single-bladed props varying degrees success consistently better everyone would use isnt case Because single-bladed props have used FF Rubber Speed models its probably worthwhile discuss briefly concern maximizing efficiencythat converting energy power plant kinetic energy airplanethe single-bladed propeller may offer some advantage due both larger volume column air propeller influences decreased tip hub drag losses Energy conversion primary impor tance FF rubber-powered duration mod els well CL Speed models Rubber model energy stored rub ber motor converted least possible loss movement air plane same true Speed mo del though its power very dif ferent nature both situations effi ciency crucial Its little like difference efficiency between biplanes monoplanes did last see high-performance Sailplane two sets wings course some practical prob lems construction single-bladed props power models balance weight must provided should small enough fit inside spinner avoid gen erating lot turbulence power loss vicinity hub Also single-bladed props give rise ad ditional vibration because center thrust coaxial propie 44 Model Aviation 0S 90 together 121/2 x 7 Graupner 3-blader destined go authors Sig Astro Hog As three- four-blade props become available serious consideration should given switching no other reason reduction noise levels center prop itself center thrust share common axis thrust vector one-half two-thirds prop radius away center rotating prop speed general think its fair say single-bladed props neither practical nor desirable except very specialized ap plications P effect precession vibration due P effect explained below preces sion probably secondary importance compared produced singlecylinder engines its still worthwhile dis cuss two phenomena sake completeness Also P effect important factor behavior power airplanes no matter blades propel ler find widely misunder stood P effect occurs airplane flying along path parallel axis propeller causing differences gle attack right prop blade versus left prop blade Assume airplane climbing steeply high angle attack Also sume right-handed propeller ing usedone blades descend ing right side airplane cending left Under conditions descending blade will see higher angle attack ascending blade Thus will thrust produced right side propeller disc left Because airplane will tend turn left exactly what hap pens airplanes take off climb out also tail-draggers have tendency swing left during takeoff roll frequently referred erroneously torque effect phenomenon explains twinengine airplanes both full-size model hard handle critical engine left fails Its also contrarotat ing engines often used full-size twins contrarotating engines right-hand en gine has left-hand rotation bringing descending blades closer centerline airplane variability P effect pro duces vibration double- single bladed prop prop blades horizontal position P effect max imum vertical vanishes resultant vibration has frequency twice engine rpm two-bladed prop However single-bladed prop vi bration much greater occurs frequency engine speed multibladed prop P effect still present vibration case four-bladed prop its easy see descending cending blades both sides times reason absence vibration three-bladed props may apparent Without going math involved point blade horizontal other two opposite side angle 600 horizontal posi tion contributing less P effect horizontal position combined effect two equal blade horizontal position vibration effectively canceled Precession familiar gyroscopic ef fect occurs effort made move axis rotating object another source propeller vibration gyro scope will respond moving 900 applied force direction rotation gyroscope rotating propeller gyroscope mass concentrated blades airplane maneuvers direction propeller axis will course change result precession force will gener ated 900 direction caused ma neuver airplane executing loop example force precession will tend turn right conventional airplanes today effect very notice able rotary engines widely used World War signifi cant due great rotating mass such engines Sopwith Camel particu larly nasty reputation regard see Pro file Publications No 31 Because mass propeller blades precession effect maximum blades parallel direction August 1988 45 Table 1 N D 11189 2100 3908 4 84 5795 N ades D %of2Blade diameter single-bladded prop commercially available 35 40 years ago Its shown attached 1947 McCoy 60 Notice counterweight has shaped fit inside spinner reduce hub drag Clockwise top 9 x 6 Tornado Girsh Bros 12 x 7 Graupner 5 x 3 Cox Other manufacturers have begun producing multi-bladed props check lo cal hobby shop model mag advertisements get up-to-date idea whats available m Radio trouble? Hobby Radio NC offers professional RC repairs modifications make RIC equipment produced last 25 years Complete system service battery pack servos vibration testing new frequency change etc Also R/Cer likes do-it-yourself Mobby Radio Volume 1 142 page journal including diagrams charts detailed modifications written simple understandable text Send $1995 Hobby Radio NC 401 Lillian Rd Wihon NC 27893 Send legal-size SASE price list complete services YOUR R/C SPECIALIST 919 291a548 change airplanes attitude prop perpendicular direc tion change effect zerothat disappears Thus case ioop de scribed above precession forces will maximum blades vertical minimum horizontal Vibra tion created precession forces go maximum minimum twice en gine rpm As remarked beginning sec tion may question just important vibration effects model air planes given very high vibration levels generated single-cylinder engines point however mitigation pre cession HTItI P effect contributes smoother running obtained multibladed props Equivalent sizes proper size two-bladed propeller known Table 1 will provide equivalent diameters three four blades Regardless number blades use same pitch used two-bladed prop appropriate two-bladed propeller size taken reference D given percentage two-blade diameter Thus example 10 x 6 prop 10-in diameter 6-in pitch indicated its equivalent would either three-bladed prop 93-in diameter 6-in pitch four-bladed prop 84 diam eter pitch 6 believe would reasonable round off near est ler sizes up 10 nearest /2 larger sizes course prop selection always matter experimentation get just right combi nation engine plane prop pilot pref erence Table 2 lists some common prop sizes used today RC equivalent threeand four-blade sizes have rounded nearest ry behind quite straightfor ward assumed blade contri butes equally power absorbed propeller well thrust produ ces recall propeller article October 1986 Model Aviation gave mula power absorption assuming two bladed props hp rpm3/l4x107 P h D eter both inches Now assume power pitch rpm unchanged also assume blade contributes equally power absorbed prop Thus blade quantity D4 would one-half two blades three blades quantity would one-and-one-half two blades etc Now write fol lowing expression relates diame Continued page 140 46 Model Aviation HOBBY RADIO NC I622 CD Wildcat Classic Glass Grumman KIT FEATURES Polyester fiberglass fusalage cowling retractable landing 92 wingspan gear Foam cores wing stab Available major production variations F4F-3 -3A -4 FM-i FM-2 Semi-Kit Fusalage cowling foam cores wing stab canopy retractable landing gear plans 7500 Complete Kit Everything listed semi-kit plus wood parts hardware necessary complete kit including 1/64 plywood sheeting wings$45000 Deluxe Kit Complete kit fusalage preassembled$85000 wings stab presheeted control surfaces prebuilt add $15 00 shipping Information Package Si 00 VISA/MasterCard acceptedIdaho ras add 5% sales tax Mike Zamber Classic Glass PO Box 503 Blackfoot Idaho 83221-0503 85-2309 FULL BODY PILOT KIT Contains pilot head handa boota helmet cap goggles full templates easy instruc tions Easy assemble finish Some simple sewing required Fully positionable too Prke #2061/6 scale 895 #205-Vs scale 995 #204-/6 scale1095 #2031/3 scale1695 DARNED GOOD AIRMEN Lightest pilots available Lifelike vinyl latex rubber Build Sportsman Barnstormer Full Body Bust - BUST PILOT KIT Contains pilot head helmet sport cap goggles jacket Easy assemble finish Ptoe #108-A scale NEW 595 #106-V6 scale695 #l05-Vs scale #104- scale. 895Some #103-V3 scale 1495 S mp e sew ng equ ed can estimate long should take pump up pack Just divide nominal capac ity hy charging rate multiply result 60 minutes/hour Simplifying math 3% cell capacity mAh equals charge time minutes 03 x mAh ge time minutes times interest Ni-Cds mAh 250 500 900 1200 minutes7515 2736 Lead-acid cells gel-cells Ah612 hours3 6 So use watch monitor long charging has going charger has shut off early push Start button again worried about overcharging feel pack cool safe push Start ton fact time pack cool VR light isnt glowing push Start button Ace R/C Overnighter set Ni-Cd charging instructions says same thing Charge 24 hours using charger provided before using device charge overnight 14 hours least monthly necessary advice because Ni-Cd cells have form abil ity hold charge happens slowly can successful fast charger af ter cells have formed So does leave TRC times want Set forget ie slow charge overnight dont want sit stopwatch mon ttor charging process times am bringing along palm-sized Ace R/C Over nighter plugs vans 12-VDC cigar lighter side two transmitters two receiver packs other Charging pro ceeds 14-hour rate whether van engine running stopped can useful cause TRC Fast Charger instructions specifi cally prohibit use engine running Overnighter voltage-regulated constant-current charger can internally programmed charge battery packs mAh ratings 250 500 900 1200 takes almost no room contained rugged metal case tt gets job done What can ask Ace R/C Overnighter kit 34K50 $2495 assem bled unit 34K50C $3395 Ace R/C Inc Box 51 IE Higginsville MO 64037 816 5847121 know what thinking now handle special charging plugs Very simple cut off put back JET PILOT KIT Pilot has molded jet helmet Contains face mask oxygen hose Estreme ly Realistic Weighs less oz P616 #308/ scale 595 #307-/ scale 695 ORDERING INSTRUCTIONS See dealer first order direct Add $100 shipping NYS residents add 7O/ tax Send check money order CODS OK Send $100 catalog Deans connectors available Ace R/C above have take along special connectornot whole 110VAC charger monitor whats going have Accu tach 2A described column April 1988 issue universal adapter Ugly Octopus described column March 1982 issue electronic repairs Ill carry Portasol soldering iron see February 1988 co lumn Well thats month know what plan about charging batteries Dont expect quick answers letters next few months because wont receiving mail sold house son Im off see world See Dealer add Dollar direct Ofder handling Throwing blade can real disaster due danger thrown blade also damage air plane would caused enormous vibration would result Substantial tor sional stresses encountered propel ler largely hub due great torque variations single-cylinder engines worse four-cycle engines poorly designed prop bomb wait ing go off advice keep eye open local hobby shop watch magazine ads manufacturers jump bandwagon offer quieter now sought-after multi bladed props Multi-Blade Props/AbbottRC Electrics/Kopski Continued page 46Continued page 49 lers various numbers blades di ameter two blades 25 Dn/D2 n er blades D2diameter two-bladed prop Dn eter prop n blades Plugging numbers expression provides values given table Whats available great majority commercially available props two bladed variety four major prop manufacturers known offer three bladed props Grish Tornado Cox Graupner make plastic/nylon props Zen gali makes black fiber-filled variety smaller sizes wooden props larger sizes Cox offers small three-bladers 51 range Grish offers three-bladers sizes up 10 Graupner offers larger props starting 9 going up 16 Zengali currently offering fiberfilled three-bladed props sizes 8 9 10 x 6 lOx 75 10 x 8 wooden threeor four-bladed props range diameter 13 28 Check local hobby shop find out whats currently available Its out question make own three- four-bladed props better really know what doing heck second thought just drink stuff glassware insteadits gotta fun Some Electric trivia brought mind looked back August 85 issue above reference column contained photo Astro Flights Bob Bouchers then-new Challengera very competent Electric Sailplane happens just finished flew new Challenger two days ago brought back viv id memories Bobs Bob brought 1984 KRC Electric Fly Yup way California gave opportunity fly fair Bob course because night before called desperation after just arriving East Coast seems Challenger found full-scale skies less friendly wing wound up some tears Mono Kote late Friday night evening before meet Bob very much needed some red transparent film patch things up Luckily brand new roll able accommodate Bob wing Jim ZarembskiRCM former Electric columnist too shop Now happens that roll MonoKote few square inches missingsaw no further use til last week Thats cover ing new Challenger Yup West Coast Bob East Coast Bob now have Challenger wings covering exactly same roll Mono Kote Hows some Electric trivia Anyway has explosion sorts Challenger population locality dur ing past six months effect went four during period 140 Model Aviation