part Make Custom-made props particular airplane/engine combination can make racer fly faster twopart article author discusses month considera tions determine parameters special prop Development blank carving propeller will covered July issue U Harold deBolt Pron s TODAYS hobby shops offer us simple necessities Usually ready use least kit form lacking something can make own propellers have very wide variety ready mades available restricted what offered Very often propeller re quirements can very particular sizes needed maximum efficiency desired propeller experimenta tion desired considerable design re search woodworking knowledge necessary answer problem has reworking production props time consuming procedure often re sults inferior product shdrtcomings reworking nu merous Most often enough material allow desired changes Changes amounts types pitch restricted original design fixed design also prevents us obtain ing different blade shape Reworking allows us nothing alter someone elses propeller design may far ultimate Reworking can improve performance Have wondered production propel lers anywhere near perfection no ticed have changed little over years Does mean propeller design reached perfection years ago no such thing perfection what seems perfect today always improved morrow year seems bring better engines Maximum power obtained much higher rpm ever before Since prop controls rpm could changes prop design take better advantage en gine improvements Airplane performance direct result power available Assuming prop pitch correct speed airplane power available combination horsepower engine thrust developed propeller So pro peller efficiency important very powerful engine turning very inefficent propeller excellent cooling fan An efficient prop type engine would less ultimate diff erent engine particular type en gine requires different style propeller 30 Model Aviation propeller prototype shown picture has 9-in diameter width 3/4 Pitch 6-1/2 static rpm 20000 attains 27000 rpm flight According author normal unloading comes attention design reduction propeller drag High -Performance perfect match between engine prop experimentation required commercial prop necessarily ul timate purpose look ing performance air plane build scratch may design it reasonable positive engine-propeller combina tion correct before attempting im prove airplane Most modelers throw up hands suggested make own propellers However chore relatively simple inexpensive does require great skill no limit experi mentation ultimate found - duplication problem Would believe can produce propeller scratch less two hours time will explain basic design parame ters can used also will provide information needed produce prop wish workshop Required tools inexpensive materials com mon Check high school indus trial arts teacher might happy fabricate prop blanks class pro ject Before commencing need know diameter blade width blade shape pitch can change parameters time note results proper testing will have facts base improvements critical aspect incorpo rate exact pitch pitch character istics desired Once prop roughed out difficult alter pitch Choos ing amount pitch extremely im portant before commencing propel ler experimental rather duplicate advantageous make oversize design parameters except ptich An oversize propeller can altered desired way allowing room experimentation After prop roughed out can run engine oversized can systematically trimmed altered ob tain maximum efficiency ob taining match engine over size prop will allow engine reach desired rpm Reducing size prop ineffective areas will bring rpm up keeping greatest size efficient areas propellers de scribed oversized reasons prop desired pitch can produced easily block method Once pitch blade angles known prop blank fabricated accu rately Carving blades automatically results proper pitch blades can have type airfoil affecting pitch secret blank must have square corners opposite sides parallel physical size cross sec tion blank station blade determines pitch station Thus pitch can varied along blade adjusting size prop blankin top view side view combination _ 0 0 0 4 z 0 C 01 U Lii 0 I 0 0 0 -J 0 -J Lii 2Z 1 0 z cr1 0z DC 4 z 0 C C wx 0 LU 04 z 10 0 0 HZ LJa Cod 0 0 z A0 0 Lii 0 0 U -J 0J 0 0Z OC -Jot 0 OH -iw uJI IH 0 Z 3 6 Z C 0 Lii 0 DC 4 C Zx 9 C Lii Uz wO I0 0 0-a0~ Q:U -J-J 4 00 LaiZ 1 U 6 z n-Lii~I H0-I C0 0 aIa HI0 C T I0 i~C aH C Li0 4 -I K 4-00 H Li-Lii HH Z 0 4 IC C 0 H 4Ij _________________________________ _ LLJ HI 0CD Lii Ua CD V H a-A-- --v --0 H 0 4 -J U H 4 -J Lii Haz a-C I -J UcD H 0 ILi Lii Lii U ii C 0o Lii Q.0C June1978 31 CENTER LINE OF PROP SHAFT DISTANCE THAT BLADE TRAVELS AT EACH STATION IN ONE REVOLUTION TrXD _ _ 2A 11A 3 60%TIPC / / BLADE ANGLE LINES ____________________________________________B PARALLELOGRAM TO DETERMINE PROPELLER BLADE ANGLES two Accuracy pitch obtained using diagonal reference line runs lower corner blank oppo site upper corner station diag onal true pitch angle particular blade station Any type airfoil can formed around diagonal accuracy propeller depends entirely upon prop blank used therefore accurate method laying out blank necessary diagram shown Grant parallelogram accurately deter mines proper blade angles given pitch throughout stations blade prop blank laid out using simple templates wood machined scribed outlines However before templates can made dimensions must obtained parallelogram pro vides dimensions description diagram No 1 standard prop references deviations pertain long dimension A-B represents distance tip will travel revolu tion circumference prop disc distance other stations travel por tion A-B short dimension B-C distance forward propeller will move did slip revolution theoretical pitch line drawn point station blade will create proper blade angle given pitch station blade angles greatest near hub become lower distance hub increased prop produced true parallelo gram called helical pitch com monly used propeller because pitch re mains constant throughout blade result prop describes true helix moves forward helical propel ler blade forces proportional throughout blade same method can used slight alteration determine correct blade angles prop does have helical pitch common variation use pro gressive pitch pitch higher center lower tip Progressive pitch increases pitch area prop travels least distance thus requires less power reduces pitch dis PROP ROTATION GREATER PRECESSIONANGLE NORMAL CESSION EFFECT tance traveled greatest power absorption heaviest increas ing efficiency propeller Tests confirm dotted lines par allelogram show method used deter proper blade angles progres sive pitch example shows progres sive pitch prop same average pitch used helical pitch prop similar method can used obtain blade angles pitch desired particular sta tion blade example some com mercial props have much lower pitch center about station No 3 rest blade angles also can determined parallelogram parallelogram can make templates needed lay out blank control factor top front view prop side-view template de veloped top-view template top view blade shape view controlled largely width blade location width blade Basic design tells us width should great possible widths 7 12% diameter within proved parameters Secondly maxi mum efficiency width should about 60% station would also like blade shape would create equal air loads station blade Just because some blade shape looks pretty does mean best action prop blade said loaded creating resultant force works resultant force accumulation forces created station blade force station created blade angle pitch blade width airfoil constant pitch fixed alteration amount force station needed must accomplished varying blade width Station widths control blade shape working very high propel ler speeds tip speeds approach Mach can often see effect compressibility practice see props said cavitate flutter vibrate high rpm Such result often material and/or workmanship ever should sure cause otherwise effort can wrong direction Cavitation also can caused pro peller blade properly loaded load should equal throughout blade prevent fluttering vibration design blade shape controls know areas least efficiency hub tip maximum 32 Model Aviation F blade width fixed 60% station Fortunately use practical dimensions hub tip connect smooth flowing lines maximum width arrive useable shape should discover cavitation during tests altering blade shape suspect stations may very well equalize blade load cure needed Diagram No 1 commonly used suc cessful blade shape basic shape width desired prop known 60% station No 3 move up line A-F parallelogram until right-angle dimension line A-F diagonal line A-3 exactly red blade width point drop per pendicular line down crossing line A-B When rectangle completed about point shown maxi mum size prop blank Theoretically can now determine correct station cross sections measuring diagonal angle line crosses cross-sec tion outline station No 3 practical since required strength would lacking hub tips would taper Therefore lay out topview shape would like sufficient width strength hub narrow tip Once shape deter mined width blank known station POSSIBLE AIRFOILS depth blank station can found two ways First ob tain depths same way done maximum width measuring line A-F proper angle line doubling dimension point line A-B perhaps accurately measuring angle station laying out cross section station top view determining depth angle line See diagram No Once have required depths blank station side-view tem plate can laid out center line drawn various station lines erec ed about depth dimensions station bisected about center line points station connected smoothly make outline sideview template Due width pencil lines .measuring errors best make template outlines double size paper transfer template ma terial Template material should dur able Metal thin plastic sheet fine Once outline material lining up template wood facilitated prop shaft hole drilled center top view template small view ing hole drilled center side view template important out line template undersized enough allow width pen line marking actual blank Using tem plates next step draw outlines wood simple way cut strips wood about maximum size templates drill prop shaft hole squarely center blank done top-view outline made wood machined out line side-view outline made using center line wood line up side-view template least affected changes prop design will dis cuss first wish try stan dard prop use described tem plate layout wish try variations pitch such progression diagram No 2 shows top view remains same helical pitch side view changes vary thickness blank thicker pitch called thinner pitch less helical pitch type differ ences dimensions taken origi nal paper layout determine exact thick ness Considering blade sppeds can ap proach sonic speeds sweepback might advantage diagram shows tem plates standard prop template sweepback added ob tain sweepback side view laid out station dimensions taken trailing edge block instead center line Sweepback could also applied front view although would conflict other design advantages can used propeller blade effected two ces mechanical other aerody namic engine creates power turns propeller doing creates force within wood hold yardstick end slapping against desk top sound would indi cate amount force applied rotating stick through arc create slap arm originated force power transmitted mechani cally through wood stick desk felt result would cen ter line force moved through stick its end propeller also has mechanical force center line originates force generated engine shaft will center material blade stationright throught middle blade Continued page 90 June 1978 33 propeller blank ready carving developed b procedures ouxiinea article Sheet plastic templates shown R Standard No 1 propeller see drawings side-view template top view No 6 prop precession progressive pitch added Lets face folks AMA free flight RC glider events can provide fero cious competition anyone wants SAM events chance relaxation good fellowship importantly fun Painless Servo Mounts continuously perplexing problem converting Old Timer models radio has mounting servos fuselage frame sides Invariably end up using heavy maple motor-mount stock epoxied place sides cross members hold down servo tray Hardly neat light-weight method have recently used Ser-kit Buckeye Balsa 3330 Youngstown-Kingsville Road Cortland Oh 44410 find ideal oldtimer use consists two groved hard wood blocks 16 o tight-fitting rails slid adjusted fore aft optimum servo loca tion glued slots retained scraps left over cutting rails simple solution com plex problem Buckeye Balsa also has inventory sheet balsa balsa spruce strip 54 60 66 72 lengths Wood long lengths often needed construction really huge old timers avoid splicing Dee B Mathews 506 South Walnut Greensburg KS 67054 RC Pylon/Lane continued page 29 come event Nationals C B Enterprises has some success 800 sq Cosmic Wind design Scale Squadron Orange Coun ty California beginning get some interest going scale AT-6 Texan class AT-6 800 sq class thereabouts hope guys have ap parently upset February March articles will understand now am trying downgrade QM Formula look around people have dropped out QM Formula primary reasons planes going too fast cost too much know thats what racing about think its too bad events end up pros reaping benefits seems should room anyone wants compete QM Formula coming dead last time Hopefully have made model ers irate article think have aware average modelers would like compete other one-class racing limited design aircraft Hey guys Chicago area Mr Justice 1816 N Mozart Chicago IL would like get pylon racing wife Debra wishes caller wants know about duties caller about contacting Justices give some pointers racing am sure would appreciate have copy MNPRA manual published several years ago Debra would like read winner Reno Air Races last year entry American Air Rac ing Teams Top Turkey Figure three view what looked like ship modified Shoestring design Next month will have 3-view Team Tur keys new ship called Wild Turkey Dave Lane 447 W 136th St Haw thorne CA 90250 Make Props/de Bolt continued page 33 speak force applied pro peller As propeller works creates thrust force transmitted aircraft through blade material via engine shaft thrust would also have center line force Thrust result combi nation lift developed airfoil upper curve fan effect off bottom blade would line resultant between So resultant line thrust could parallel mechanical line thrust tip hub Ideally two lines thrust would same loca tion chord-wise torsional rotational force set up would tend rotate blade about mechanical line force can make variations stan dard design top view blade can approach ideal position lines force diagram No 3 show thrust line force can product review product review product review Pactra Aero-Poxy Pactra offers new line specially formulated 2-component system finishes Aero-Poxy tough fuel-proof marresistant one-coat armour finish designed endure rough handling fuel spillage unique formulation utilizes non-irritating non-sensitizing curing agent elimi nates dermatitic respiratory problems Aero-Poxy free lead hazards nontoxic dry Available colors gloss clear primer 8 oz onlyl choice Super Hi-Gloss Catalyst Flat Catalyst versatility finish color-mixing capabili ties Suitable brush spray Available 4- 8-oz cans plus thinners brushing spray 16- 32-oz cans Pactra Indus tries 7060 Hollywood Blvd Los Angeles CA 90028 product review product review product review 90 Model Aviation Kraftsmanship kit processed AAMCO GOLD BALSAThis Trainer will blow apart hits ground GREATEST B/C BASIC TRAINEB Design & Kit ALL TIME Ask over 25000 satisfied builders H-BAY dealers sold themSHALL WE SAY MORE Andrews Aircraft Model Co Inc US Rte 1& North Sc Topsfield Mass 01983 887-8541 Price $3995 kit pee dollar- bar em lined up mechanical line force remove tendency blade change pitch working would advantageous especially thin blades used Another design consideration preces sion no confused preces sion force created through gyroscopic action prop rotation Precession simply moving ahead point thrust would normally applied blade propeller arc normal blade shapes center line thrust coin cides line passes through center engine shaft looking front shaft top view pro peller blade center line rota tion blade angles created center As blade moves through arc rotation con sidered line along thrust generated Pitch also measured line center line thrust can moved ahead center line rotation effective angle blade arc rotation will increased changing physical angle advantage precession crease pitch adding drag Drag created physical angle blades precession change physical angle effective change pitch can used advantage air craft requires 7 pitch terminal ve locity precession prop pitch can 6 example will still have effective pitch 7 lower drag 6/4 physical pitch plus factor combined lower drag will allow engine rpm power drawback precession moves center line thrust away line mechanical force torsional rotation force created possible rigid blades torsional rotation force could disregarded taking advan tage precession instead stan dard prop shape precession added shown diagram No 4 Diagrams No 5 6 show design factors can incorporated blade shape Before finalizing ideas may wish try custom made props type blade airfoil should considered considerations blade airfoil same wing wish greatest lift possible least amount dragthe old L/D ratio again Secondly air speed should con sidered Formula propeller stance average blade air speed about 350 mph tip speed ap proaching sonic range An airfoil de veloped speed ranges would efficient modern airfoils have excellent lift-drag ratio far less drag older styles amount drag reduced serious loss lift result same adding horse power part II will show can transform thse ideas actual props own workshop Additionally will explain test tailor particular needs Nurnberg/Moulton continued page 38 Just gliders mostly scale eyccatching power kits after seeing Katos 20 & 40 versions Prettners Curare host electrics ranging Aeronauts BD-5 Udet Flamingo Graupners Elektra-fly Elektro-Max Queen show scribe undoubtedly 8-ft Svenson Storch 60s Its big rugged functional intended fly STOL lots power big prop fine pitch Fixed slats power ful flaps tail feathers plus longstroke landing gear rest won der no German firm did firstSven son Belgian Cessnas abound Cox RTF Carreras plastic Wichita replicas cater constant demand Graupner has gone Jodel Robin DR400 big way brochures say itll take new OS 90 especially used tow sailplanes Other big scale kits Wolfgang Rodel has MBB 233 Flamingo June1978 91
Edition: Model Aviation - 1978/06
Page Numbers: 30, 31, 32, 33, 90, 91
part Make Custom-made props particular airplane/engine combination can make racer fly faster twopart article author discusses month considera tions determine parameters special prop Development blank carving propeller will covered July issue U Harold deBolt Pron s TODAYS hobby shops offer us simple necessities Usually ready use least kit form lacking something can make own propellers have very wide variety ready mades available restricted what offered Very often propeller re quirements can very particular sizes needed maximum efficiency desired propeller experimenta tion desired considerable design re search woodworking knowledge necessary answer problem has reworking production props time consuming procedure often re sults inferior product shdrtcomings reworking nu merous Most often enough material allow desired changes Changes amounts types pitch restricted original design fixed design also prevents us obtain ing different blade shape Reworking allows us nothing alter someone elses propeller design may far ultimate Reworking can improve performance Have wondered production propel lers anywhere near perfection no ticed have changed little over years Does mean propeller design reached perfection years ago no such thing perfection what seems perfect today always improved morrow year seems bring better engines Maximum power obtained much higher rpm ever before Since prop controls rpm could changes prop design take better advantage en gine improvements Airplane performance direct result power available Assuming prop pitch correct speed airplane power available combination horsepower engine thrust developed propeller So pro peller efficiency important very powerful engine turning very inefficent propeller excellent cooling fan An efficient prop type engine would less ultimate diff erent engine particular type en gine requires different style propeller 30 Model Aviation propeller prototype shown picture has 9-in diameter width 3/4 Pitch 6-1/2 static rpm 20000 attains 27000 rpm flight According author normal unloading comes attention design reduction propeller drag High -Performance perfect match between engine prop experimentation required commercial prop necessarily ul timate purpose look ing performance air plane build scratch may design it reasonable positive engine-propeller combina tion correct before attempting im prove airplane Most modelers throw up hands suggested make own propellers However chore relatively simple inexpensive does require great skill no limit experi mentation ultimate found - duplication problem Would believe can produce propeller scratch less two hours time will explain basic design parame ters can used also will provide information needed produce prop wish workshop Required tools inexpensive materials com mon Check high school indus trial arts teacher might happy fabricate prop blanks class pro ject Before commencing need know diameter blade width blade shape pitch can change parameters time note results proper testing will have facts base improvements critical aspect incorpo rate exact pitch pitch character istics desired Once prop roughed out difficult alter pitch Choos ing amount pitch extremely im portant before commencing propel ler experimental rather duplicate advantageous make oversize design parameters except ptich An oversize propeller can altered desired way allowing room experimentation After prop roughed out can run engine oversized can systematically trimmed altered ob tain maximum efficiency ob taining match engine over size prop will allow engine reach desired rpm Reducing size prop ineffective areas will bring rpm up keeping greatest size efficient areas propellers de scribed oversized reasons prop desired pitch can produced easily block method Once pitch blade angles known prop blank fabricated accu rately Carving blades automatically results proper pitch blades can have type airfoil affecting pitch secret blank must have square corners opposite sides parallel physical size cross sec tion blank station blade determines pitch station Thus pitch can varied along blade adjusting size prop blankin top view side view combination _ 0 0 0 4 z 0 C 01 U Lii 0 I 0 0 0 -J 0 -J Lii 2Z 1 0 z cr1 0z DC 4 z 0 C C wx 0 LU 04 z 10 0 0 HZ LJa Cod 0 0 z A0 0 Lii 0 0 U -J 0J 0 0Z OC -Jot 0 OH -iw uJI IH 0 Z 3 6 Z C 0 Lii 0 DC 4 C Zx 9 C Lii Uz wO I0 0 0-a0~ Q:U -J-J 4 00 LaiZ 1 U 6 z n-Lii~I H0-I C0 0 aIa HI0 C T I0 i~C aH C Li0 4 -I K 4-00 H Li-Lii HH Z 0 4 IC C 0 H 4Ij _________________________________ _ LLJ HI 0CD Lii Ua CD V H a-A-- --v --0 H 0 4 -J U H 4 -J Lii Haz a-C I -J UcD H 0 ILi Lii Lii U ii C 0o Lii Q.0C June1978 31 CENTER LINE OF PROP SHAFT DISTANCE THAT BLADE TRAVELS AT EACH STATION IN ONE REVOLUTION TrXD _ _ 2A 11A 3 60%TIPC / / BLADE ANGLE LINES ____________________________________________B PARALLELOGRAM TO DETERMINE PROPELLER BLADE ANGLES two Accuracy pitch obtained using diagonal reference line runs lower corner blank oppo site upper corner station diag onal true pitch angle particular blade station Any type airfoil can formed around diagonal accuracy propeller depends entirely upon prop blank used therefore accurate method laying out blank necessary diagram shown Grant parallelogram accurately deter mines proper blade angles given pitch throughout stations blade prop blank laid out using simple templates wood machined scribed outlines However before templates can made dimensions must obtained parallelogram pro vides dimensions description diagram No 1 standard prop references deviations pertain long dimension A-B represents distance tip will travel revolu tion circumference prop disc distance other stations travel por tion A-B short dimension B-C distance forward propeller will move did slip revolution theoretical pitch line drawn point station blade will create proper blade angle given pitch station blade angles greatest near hub become lower distance hub increased prop produced true parallelo gram called helical pitch com monly used propeller because pitch re mains constant throughout blade result prop describes true helix moves forward helical propel ler blade forces proportional throughout blade same method can used slight alteration determine correct blade angles prop does have helical pitch common variation use pro gressive pitch pitch higher center lower tip Progressive pitch increases pitch area prop travels least distance thus requires less power reduces pitch dis PROP ROTATION GREATER PRECESSIONANGLE NORMAL CESSION EFFECT tance traveled greatest power absorption heaviest increas ing efficiency propeller Tests confirm dotted lines par allelogram show method used deter proper blade angles progres sive pitch example shows progres sive pitch prop same average pitch used helical pitch prop similar method can used obtain blade angles pitch desired particular sta tion blade example some com mercial props have much lower pitch center about station No 3 rest blade angles also can determined parallelogram parallelogram can make templates needed lay out blank control factor top front view prop side-view template de veloped top-view template top view blade shape view controlled largely width blade location width blade Basic design tells us width should great possible widths 7 12% diameter within proved parameters Secondly maxi mum efficiency width should about 60% station would also like blade shape would create equal air loads station blade Just because some blade shape looks pretty does mean best action prop blade said loaded creating resultant force works resultant force accumulation forces created station blade force station created blade angle pitch blade width airfoil constant pitch fixed alteration amount force station needed must accomplished varying blade width Station widths control blade shape working very high propel ler speeds tip speeds approach Mach can often see effect compressibility practice see props said cavitate flutter vibrate high rpm Such result often material and/or workmanship ever should sure cause otherwise effort can wrong direction Cavitation also can caused pro peller blade properly loaded load should equal throughout blade prevent fluttering vibration design blade shape controls know areas least efficiency hub tip maximum 32 Model Aviation F blade width fixed 60% station Fortunately use practical dimensions hub tip connect smooth flowing lines maximum width arrive useable shape should discover cavitation during tests altering blade shape suspect stations may very well equalize blade load cure needed Diagram No 1 commonly used suc cessful blade shape basic shape width desired prop known 60% station No 3 move up line A-F parallelogram until right-angle dimension line A-F diagonal line A-3 exactly red blade width point drop per pendicular line down crossing line A-B When rectangle completed about point shown maxi mum size prop blank Theoretically can now determine correct station cross sections measuring diagonal angle line crosses cross-sec tion outline station No 3 practical since required strength would lacking hub tips would taper Therefore lay out topview shape would like sufficient width strength hub narrow tip Once shape deter mined width blank known station POSSIBLE AIRFOILS depth blank station can found two ways First ob tain depths same way done maximum width measuring line A-F proper angle line doubling dimension point line A-B perhaps accurately measuring angle station laying out cross section station top view determining depth angle line See diagram No Once have required depths blank station side-view tem plate can laid out center line drawn various station lines erec ed about depth dimensions station bisected about center line points station connected smoothly make outline sideview template Due width pencil lines .measuring errors best make template outlines double size paper transfer template ma terial Template material should dur able Metal thin plastic sheet fine Once outline material lining up template wood facilitated prop shaft hole drilled center top view template small view ing hole drilled center side view template important out line template undersized enough allow width pen line marking actual blank Using tem plates next step draw outlines wood simple way cut strips wood about maximum size templates drill prop shaft hole squarely center blank done top-view outline made wood machined out line side-view outline made using center line wood line up side-view template least affected changes prop design will dis cuss first wish try stan dard prop use described tem plate layout wish try variations pitch such progression diagram No 2 shows top view remains same helical pitch side view changes vary thickness blank thicker pitch called thinner pitch less helical pitch type differ ences dimensions taken origi nal paper layout determine exact thick ness Considering blade sppeds can ap proach sonic speeds sweepback might advantage diagram shows tem plates standard prop template sweepback added ob tain sweepback side view laid out station dimensions taken trailing edge block instead center line Sweepback could also applied front view although would conflict other design advantages can used propeller blade effected two ces mechanical other aerody namic engine creates power turns propeller doing creates force within wood hold yardstick end slapping against desk top sound would indi cate amount force applied rotating stick through arc create slap arm originated force power transmitted mechani cally through wood stick desk felt result would cen ter line force moved through stick its end propeller also has mechanical force center line originates force generated engine shaft will center material blade stationright throught middle blade Continued page 90 June 1978 33 propeller blank ready carving developed b procedures ouxiinea article Sheet plastic templates shown R Standard No 1 propeller see drawings side-view template top view No 6 prop precession progressive pitch added Lets face folks AMA free flight RC glider events can provide fero cious competition anyone wants SAM events chance relaxation good fellowship importantly fun Painless Servo Mounts continuously perplexing problem converting Old Timer models radio has mounting servos fuselage frame sides Invariably end up using heavy maple motor-mount stock epoxied place sides cross members hold down servo tray Hardly neat light-weight method have recently used Ser-kit Buckeye Balsa 3330 Youngstown-Kingsville Road Cortland Oh 44410 find ideal oldtimer use consists two groved hard wood blocks 16 o tight-fitting rails slid adjusted fore aft optimum servo loca tion glued slots retained scraps left over cutting rails simple solution com plex problem Buckeye Balsa also has inventory sheet balsa balsa spruce strip 54 60 66 72 lengths Wood long lengths often needed construction really huge old timers avoid splicing Dee B Mathews 506 South Walnut Greensburg KS 67054 RC Pylon/Lane continued page 29 come event Nationals C B Enterprises has some success 800 sq Cosmic Wind design Scale Squadron Orange Coun ty California beginning get some interest going scale AT-6 Texan class AT-6 800 sq class thereabouts hope guys have ap parently upset February March articles will understand now am trying downgrade QM Formula look around people have dropped out QM Formula primary reasons planes going too fast cost too much know thats what racing about think its too bad events end up pros reaping benefits seems should room anyone wants compete QM Formula coming dead last time Hopefully have made model ers irate article think have aware average modelers would like compete other one-class racing limited design aircraft Hey guys Chicago area Mr Justice 1816 N Mozart Chicago IL would like get pylon racing wife Debra wishes caller wants know about duties caller about contacting Justices give some pointers racing am sure would appreciate have copy MNPRA manual published several years ago Debra would like read winner Reno Air Races last year entry American Air Rac ing Teams Top Turkey Figure three view what looked like ship modified Shoestring design Next month will have 3-view Team Tur keys new ship called Wild Turkey Dave Lane 447 W 136th St Haw thorne CA 90250 Make Props/de Bolt continued page 33 speak force applied pro peller As propeller works creates thrust force transmitted aircraft through blade material via engine shaft thrust would also have center line force Thrust result combi nation lift developed airfoil upper curve fan effect off bottom blade would line resultant between So resultant line thrust could parallel mechanical line thrust tip hub Ideally two lines thrust would same loca tion chord-wise torsional rotational force set up would tend rotate blade about mechanical line force can make variations stan dard design top view blade can approach ideal position lines force diagram No 3 show thrust line force can product review product review product review Pactra Aero-Poxy Pactra offers new line specially formulated 2-component system finishes Aero-Poxy tough fuel-proof marresistant one-coat armour finish designed endure rough handling fuel spillage unique formulation utilizes non-irritating non-sensitizing curing agent elimi nates dermatitic respiratory problems Aero-Poxy free lead hazards nontoxic dry Available colors gloss clear primer 8 oz onlyl choice Super Hi-Gloss Catalyst Flat Catalyst versatility finish color-mixing capabili ties Suitable brush spray Available 4- 8-oz cans plus thinners brushing spray 16- 32-oz cans Pactra Indus tries 7060 Hollywood Blvd Los Angeles CA 90028 product review product review product review 90 Model Aviation Kraftsmanship kit processed AAMCO GOLD BALSAThis Trainer will blow apart hits ground GREATEST B/C BASIC TRAINEB Design & Kit ALL TIME Ask over 25000 satisfied builders H-BAY dealers sold themSHALL WE SAY MORE Andrews Aircraft Model Co Inc US Rte 1& North Sc Topsfield Mass 01983 887-8541 Price $3995 kit pee dollar- bar em lined up mechanical line force remove tendency blade change pitch working would advantageous especially thin blades used Another design consideration preces sion no confused preces sion force created through gyroscopic action prop rotation Precession simply moving ahead point thrust would normally applied blade propeller arc normal blade shapes center line thrust coin cides line passes through center engine shaft looking front shaft top view pro peller blade center line rota tion blade angles created center As blade moves through arc rotation con sidered line along thrust generated Pitch also measured line center line thrust can moved ahead center line rotation effective angle blade arc rotation will increased changing physical angle advantage precession crease pitch adding drag Drag created physical angle blades precession change physical angle effective change pitch can used advantage air craft requires 7 pitch terminal ve locity precession prop pitch can 6 example will still have effective pitch 7 lower drag 6/4 physical pitch plus factor combined lower drag will allow engine rpm power drawback precession moves center line thrust away line mechanical force torsional rotation force created possible rigid blades torsional rotation force could disregarded taking advan tage precession instead stan dard prop shape precession added shown diagram No 4 Diagrams No 5 6 show design factors can incorporated blade shape Before finalizing ideas may wish try custom made props type blade airfoil should considered considerations blade airfoil same wing wish greatest lift possible least amount dragthe old L/D ratio again Secondly air speed should con sidered Formula propeller stance average blade air speed about 350 mph tip speed ap proaching sonic range An airfoil de veloped speed ranges would efficient modern airfoils have excellent lift-drag ratio far less drag older styles amount drag reduced serious loss lift result same adding horse power part II will show can transform thse ideas actual props own workshop Additionally will explain test tailor particular needs Nurnberg/Moulton continued page 38 Just gliders mostly scale eyccatching power kits after seeing Katos 20 & 40 versions Prettners Curare host electrics ranging Aeronauts BD-5 Udet Flamingo Graupners Elektra-fly Elektro-Max Queen show scribe undoubtedly 8-ft Svenson Storch 60s Its big rugged functional intended fly STOL lots power big prop fine pitch Fixed slats power ful flaps tail feathers plus longstroke landing gear rest won der no German firm did firstSven son Belgian Cessnas abound Cox RTF Carreras plastic Wichita replicas cater constant demand Graupner has gone Jodel Robin DR400 big way brochures say itll take new OS 90 especially used tow sailplanes Other big scale kits Wolfgang Rodel has MBB 233 Flamingo June1978 91
Edition: Model Aviation - 1978/06
Page Numbers: 30, 31, 32, 33, 90, 91
part Make Custom-made props particular airplane/engine combination can make racer fly faster twopart article author discusses month considera tions determine parameters special prop Development blank carving propeller will covered July issue U Harold deBolt Pron s TODAYS hobby shops offer us simple necessities Usually ready use least kit form lacking something can make own propellers have very wide variety ready mades available restricted what offered Very often propeller re quirements can very particular sizes needed maximum efficiency desired propeller experimenta tion desired considerable design re search woodworking knowledge necessary answer problem has reworking production props time consuming procedure often re sults inferior product shdrtcomings reworking nu merous Most often enough material allow desired changes Changes amounts types pitch restricted original design fixed design also prevents us obtain ing different blade shape Reworking allows us nothing alter someone elses propeller design may far ultimate Reworking can improve performance Have wondered production propel lers anywhere near perfection no ticed have changed little over years Does mean propeller design reached perfection years ago no such thing perfection what seems perfect today always improved morrow year seems bring better engines Maximum power obtained much higher rpm ever before Since prop controls rpm could changes prop design take better advantage en gine improvements Airplane performance direct result power available Assuming prop pitch correct speed airplane power available combination horsepower engine thrust developed propeller So pro peller efficiency important very powerful engine turning very inefficent propeller excellent cooling fan An efficient prop type engine would less ultimate diff erent engine particular type en gine requires different style propeller 30 Model Aviation propeller prototype shown picture has 9-in diameter width 3/4 Pitch 6-1/2 static rpm 20000 attains 27000 rpm flight According author normal unloading comes attention design reduction propeller drag High -Performance perfect match between engine prop experimentation required commercial prop necessarily ul timate purpose look ing performance air plane build scratch may design it reasonable positive engine-propeller combina tion correct before attempting im prove airplane Most modelers throw up hands suggested make own propellers However chore relatively simple inexpensive does require great skill no limit experi mentation ultimate found - duplication problem Would believe can produce propeller scratch less two hours time will explain basic design parame ters can used also will provide information needed produce prop wish workshop Required tools inexpensive materials com mon Check high school indus trial arts teacher might happy fabricate prop blanks class pro ject Before commencing need know diameter blade width blade shape pitch can change parameters time note results proper testing will have facts base improvements critical aspect incorpo rate exact pitch pitch character istics desired Once prop roughed out difficult alter pitch Choos ing amount pitch extremely im portant before commencing propel ler experimental rather duplicate advantageous make oversize design parameters except ptich An oversize propeller can altered desired way allowing room experimentation After prop roughed out can run engine oversized can systematically trimmed altered ob tain maximum efficiency ob taining match engine over size prop will allow engine reach desired rpm Reducing size prop ineffective areas will bring rpm up keeping greatest size efficient areas propellers de scribed oversized reasons prop desired pitch can produced easily block method Once pitch blade angles known prop blank fabricated accu rately Carving blades automatically results proper pitch blades can have type airfoil affecting pitch secret blank must have square corners opposite sides parallel physical size cross sec tion blank station blade determines pitch station Thus pitch can varied along blade adjusting size prop blankin top view side view combination _ 0 0 0 4 z 0 C 01 U Lii 0 I 0 0 0 -J 0 -J Lii 2Z 1 0 z cr1 0z DC 4 z 0 C C wx 0 LU 04 z 10 0 0 HZ LJa Cod 0 0 z A0 0 Lii 0 0 U -J 0J 0 0Z OC -Jot 0 OH -iw uJI IH 0 Z 3 6 Z C 0 Lii 0 DC 4 C Zx 9 C Lii Uz wO I0 0 0-a0~ Q:U -J-J 4 00 LaiZ 1 U 6 z n-Lii~I H0-I C0 0 aIa HI0 C T I0 i~C aH C Li0 4 -I K 4-00 H Li-Lii HH Z 0 4 IC C 0 H 4Ij _________________________________ _ LLJ HI 0CD Lii Ua CD V H a-A-- --v --0 H 0 4 -J U H 4 -J Lii Haz a-C I -J UcD H 0 ILi Lii Lii U ii C 0o Lii Q.0C June1978 31 CENTER LINE OF PROP SHAFT DISTANCE THAT BLADE TRAVELS AT EACH STATION IN ONE REVOLUTION TrXD _ _ 2A 11A 3 60%TIPC / / BLADE ANGLE LINES ____________________________________________B PARALLELOGRAM TO DETERMINE PROPELLER BLADE ANGLES two Accuracy pitch obtained using diagonal reference line runs lower corner blank oppo site upper corner station diag onal true pitch angle particular blade station Any type airfoil can formed around diagonal accuracy propeller depends entirely upon prop blank used therefore accurate method laying out blank necessary diagram shown Grant parallelogram accurately deter mines proper blade angles given pitch throughout stations blade prop blank laid out using simple templates wood machined scribed outlines However before templates can made dimensions must obtained parallelogram pro vides dimensions description diagram No 1 standard prop references deviations pertain long dimension A-B represents distance tip will travel revolu tion circumference prop disc distance other stations travel por tion A-B short dimension B-C distance forward propeller will move did slip revolution theoretical pitch line drawn point station blade will create proper blade angle given pitch station blade angles greatest near hub become lower distance hub increased prop produced true parallelo gram called helical pitch com monly used propeller because pitch re mains constant throughout blade result prop describes true helix moves forward helical propel ler blade forces proportional throughout blade same method can used slight alteration determine correct blade angles prop does have helical pitch common variation use pro gressive pitch pitch higher center lower tip Progressive pitch increases pitch area prop travels least distance thus requires less power reduces pitch dis PROP ROTATION GREATER PRECESSIONANGLE NORMAL CESSION EFFECT tance traveled greatest power absorption heaviest increas ing efficiency propeller Tests confirm dotted lines par allelogram show method used deter proper blade angles progres sive pitch example shows progres sive pitch prop same average pitch used helical pitch prop similar method can used obtain blade angles pitch desired particular sta tion blade example some com mercial props have much lower pitch center about station No 3 rest blade angles also can determined parallelogram parallelogram can make templates needed lay out blank control factor top front view prop side-view template de veloped top-view template top view blade shape view controlled largely width blade location width blade Basic design tells us width should great possible widths 7 12% diameter within proved parameters Secondly maxi mum efficiency width should about 60% station would also like blade shape would create equal air loads station blade Just because some blade shape looks pretty does mean best action prop blade said loaded creating resultant force works resultant force accumulation forces created station blade force station created blade angle pitch blade width airfoil constant pitch fixed alteration amount force station needed must accomplished varying blade width Station widths control blade shape working very high propel ler speeds tip speeds approach Mach can often see effect compressibility practice see props said cavitate flutter vibrate high rpm Such result often material and/or workmanship ever should sure cause otherwise effort can wrong direction Cavitation also can caused pro peller blade properly loaded load should equal throughout blade prevent fluttering vibration design blade shape controls know areas least efficiency hub tip maximum 32 Model Aviation F blade width fixed 60% station Fortunately use practical dimensions hub tip connect smooth flowing lines maximum width arrive useable shape should discover cavitation during tests altering blade shape suspect stations may very well equalize blade load cure needed Diagram No 1 commonly used suc cessful blade shape basic shape width desired prop known 60% station No 3 move up line A-F parallelogram until right-angle dimension line A-F diagonal line A-3 exactly red blade width point drop per pendicular line down crossing line A-B When rectangle completed about point shown maxi mum size prop blank Theoretically can now determine correct station cross sections measuring diagonal angle line crosses cross-sec tion outline station No 3 practical since required strength would lacking hub tips would taper Therefore lay out topview shape would like sufficient width strength hub narrow tip Once shape deter mined width blank known station POSSIBLE AIRFOILS depth blank station can found two ways First ob tain depths same way done maximum width measuring line A-F proper angle line doubling dimension point line A-B perhaps accurately measuring angle station laying out cross section station top view determining depth angle line See diagram No Once have required depths blank station side-view tem plate can laid out center line drawn various station lines erec ed about depth dimensions station bisected about center line points station connected smoothly make outline sideview template Due width pencil lines .measuring errors best make template outlines double size paper transfer template ma terial Template material should dur able Metal thin plastic sheet fine Once outline material lining up template wood facilitated prop shaft hole drilled center top view template small view ing hole drilled center side view template important out line template undersized enough allow width pen line marking actual blank Using tem plates next step draw outlines wood simple way cut strips wood about maximum size templates drill prop shaft hole squarely center blank done top-view outline made wood machined out line side-view outline made using center line wood line up side-view template least affected changes prop design will dis cuss first wish try stan dard prop use described tem plate layout wish try variations pitch such progression diagram No 2 shows top view remains same helical pitch side view changes vary thickness blank thicker pitch called thinner pitch less helical pitch type differ ences dimensions taken origi nal paper layout determine exact thick ness Considering blade sppeds can ap proach sonic speeds sweepback might advantage diagram shows tem plates standard prop template sweepback added ob tain sweepback side view laid out station dimensions taken trailing edge block instead center line Sweepback could also applied front view although would conflict other design advantages can used propeller blade effected two ces mechanical other aerody namic engine creates power turns propeller doing creates force within wood hold yardstick end slapping against desk top sound would indi cate amount force applied rotating stick through arc create slap arm originated force power transmitted mechani cally through wood stick desk felt result would cen ter line force moved through stick its end propeller also has mechanical force center line originates force generated engine shaft will center material blade stationright throught middle blade Continued page 90 June 1978 33 propeller blank ready carving developed b procedures ouxiinea article Sheet plastic templates shown R Standard No 1 propeller see drawings side-view template top view No 6 prop precession progressive pitch added Lets face folks AMA free flight RC glider events can provide fero cious competition anyone wants SAM events chance relaxation good fellowship importantly fun Painless Servo Mounts continuously perplexing problem converting Old Timer models radio has mounting servos fuselage frame sides Invariably end up using heavy maple motor-mount stock epoxied place sides cross members hold down servo tray Hardly neat light-weight method have recently used Ser-kit Buckeye Balsa 3330 Youngstown-Kingsville Road Cortland Oh 44410 find ideal oldtimer use consists two groved hard wood blocks 16 o tight-fitting rails slid adjusted fore aft optimum servo loca tion glued slots retained scraps left over cutting rails simple solution com plex problem Buckeye Balsa also has inventory sheet balsa balsa spruce strip 54 60 66 72 lengths Wood long lengths often needed construction really huge old timers avoid splicing Dee B Mathews 506 South Walnut Greensburg KS 67054 RC Pylon/Lane continued page 29 come event Nationals C B Enterprises has some success 800 sq Cosmic Wind design Scale Squadron Orange Coun ty California beginning get some interest going scale AT-6 Texan class AT-6 800 sq class thereabouts hope guys have ap parently upset February March articles will understand now am trying downgrade QM Formula look around people have dropped out QM Formula primary reasons planes going too fast cost too much know thats what racing about think its too bad events end up pros reaping benefits seems should room anyone wants compete QM Formula coming dead last time Hopefully have made model ers irate article think have aware average modelers would like compete other one-class racing limited design aircraft Hey guys Chicago area Mr Justice 1816 N Mozart Chicago IL would like get pylon racing wife Debra wishes caller wants know about duties caller about contacting Justices give some pointers racing am sure would appreciate have copy MNPRA manual published several years ago Debra would like read winner Reno Air Races last year entry American Air Rac ing Teams Top Turkey Figure three view what looked like ship modified Shoestring design Next month will have 3-view Team Tur keys new ship called Wild Turkey Dave Lane 447 W 136th St Haw thorne CA 90250 Make Props/de Bolt continued page 33 speak force applied pro peller As propeller works creates thrust force transmitted aircraft through blade material via engine shaft thrust would also have center line force Thrust result combi nation lift developed airfoil upper curve fan effect off bottom blade would line resultant between So resultant line thrust could parallel mechanical line thrust tip hub Ideally two lines thrust would same loca tion chord-wise torsional rotational force set up would tend rotate blade about mechanical line force can make variations stan dard design top view blade can approach ideal position lines force diagram No 3 show thrust line force can product review product review product review Pactra Aero-Poxy Pactra offers new line specially formulated 2-component system finishes Aero-Poxy tough fuel-proof marresistant one-coat armour finish designed endure rough handling fuel spillage unique formulation utilizes non-irritating non-sensitizing curing agent elimi nates dermatitic respiratory problems Aero-Poxy free lead hazards nontoxic dry Available colors gloss clear primer 8 oz onlyl choice Super Hi-Gloss Catalyst Flat Catalyst versatility finish color-mixing capabili ties Suitable brush spray Available 4- 8-oz cans plus thinners brushing spray 16- 32-oz cans Pactra Indus tries 7060 Hollywood Blvd Los Angeles CA 90028 product review product review product review 90 Model Aviation Kraftsmanship kit processed AAMCO GOLD BALSAThis Trainer will blow apart hits ground GREATEST B/C BASIC TRAINEB Design & Kit ALL TIME Ask over 25000 satisfied builders H-BAY dealers sold themSHALL WE SAY MORE Andrews Aircraft Model Co Inc US Rte 1& North Sc Topsfield Mass 01983 887-8541 Price $3995 kit pee dollar- bar em lined up mechanical line force remove tendency blade change pitch working would advantageous especially thin blades used Another design consideration preces sion no confused preces sion force created through gyroscopic action prop rotation Precession simply moving ahead point thrust would normally applied blade propeller arc normal blade shapes center line thrust coin cides line passes through center engine shaft looking front shaft top view pro peller blade center line rota tion blade angles created center As blade moves through arc rotation con sidered line along thrust generated Pitch also measured line center line thrust can moved ahead center line rotation effective angle blade arc rotation will increased changing physical angle advantage precession crease pitch adding drag Drag created physical angle blades precession change physical angle effective change pitch can used advantage air craft requires 7 pitch terminal ve locity precession prop pitch can 6 example will still have effective pitch 7 lower drag 6/4 physical pitch plus factor combined lower drag will allow engine rpm power drawback precession moves center line thrust away line mechanical force torsional rotation force created possible rigid blades torsional rotation force could disregarded taking advan tage precession instead stan dard prop shape precession added shown diagram No 4 Diagrams No 5 6 show design factors can incorporated blade shape Before finalizing ideas may wish try custom made props type blade airfoil should considered considerations blade airfoil same wing wish greatest lift possible least amount dragthe old L/D ratio again Secondly air speed should con sidered Formula propeller stance average blade air speed about 350 mph tip speed ap proaching sonic range An airfoil de veloped speed ranges would efficient modern airfoils have excellent lift-drag ratio far less drag older styles amount drag reduced serious loss lift result same adding horse power part II will show can transform thse ideas actual props own workshop Additionally will explain test tailor particular needs Nurnberg/Moulton continued page 38 Just gliders mostly scale eyccatching power kits after seeing Katos 20 & 40 versions Prettners Curare host electrics ranging Aeronauts BD-5 Udet Flamingo Graupners Elektra-fly Elektro-Max Queen show scribe undoubtedly 8-ft Svenson Storch 60s Its big rugged functional intended fly STOL lots power big prop fine pitch Fixed slats power ful flaps tail feathers plus longstroke landing gear rest won der no German firm did firstSven son Belgian Cessnas abound Cox RTF Carreras plastic Wichita replicas cater constant demand Graupner has gone Jodel Robin DR400 big way brochures say itll take new OS 90 especially used tow sailplanes Other big scale kits Wolfgang Rodel has MBB 233 Flamingo June1978 91
Edition: Model Aviation - 1978/06
Page Numbers: 30, 31, 32, 33, 90, 91
part Make Custom-made props particular airplane/engine combination can make racer fly faster twopart article author discusses month considera tions determine parameters special prop Development blank carving propeller will covered July issue U Harold deBolt Pron s TODAYS hobby shops offer us simple necessities Usually ready use least kit form lacking something can make own propellers have very wide variety ready mades available restricted what offered Very often propeller re quirements can very particular sizes needed maximum efficiency desired propeller experimenta tion desired considerable design re search woodworking knowledge necessary answer problem has reworking production props time consuming procedure often re sults inferior product shdrtcomings reworking nu merous Most often enough material allow desired changes Changes amounts types pitch restricted original design fixed design also prevents us obtain ing different blade shape Reworking allows us nothing alter someone elses propeller design may far ultimate Reworking can improve performance Have wondered production propel lers anywhere near perfection no ticed have changed little over years Does mean propeller design reached perfection years ago no such thing perfection what seems perfect today always improved morrow year seems bring better engines Maximum power obtained much higher rpm ever before Since prop controls rpm could changes prop design take better advantage en gine improvements Airplane performance direct result power available Assuming prop pitch correct speed airplane power available combination horsepower engine thrust developed propeller So pro peller efficiency important very powerful engine turning very inefficent propeller excellent cooling fan An efficient prop type engine would less ultimate diff erent engine particular type en gine requires different style propeller 30 Model Aviation propeller prototype shown picture has 9-in diameter width 3/4 Pitch 6-1/2 static rpm 20000 attains 27000 rpm flight According author normal unloading comes attention design reduction propeller drag High -Performance perfect match between engine prop experimentation required commercial prop necessarily ul timate purpose look ing performance air plane build scratch may design it reasonable positive engine-propeller combina tion correct before attempting im prove airplane Most modelers throw up hands suggested make own propellers However chore relatively simple inexpensive does require great skill no limit experi mentation ultimate found - duplication problem Would believe can produce propeller scratch less two hours time will explain basic design parame ters can used also will provide information needed produce prop wish workshop Required tools inexpensive materials com mon Check high school indus trial arts teacher might happy fabricate prop blanks class pro ject Before commencing need know diameter blade width blade shape pitch can change parameters time note results proper testing will have facts base improvements critical aspect incorpo rate exact pitch pitch character istics desired Once prop roughed out difficult alter pitch Choos ing amount pitch extremely im portant before commencing propel ler experimental rather duplicate advantageous make oversize design parameters except ptich An oversize propeller can altered desired way allowing room experimentation After prop roughed out can run engine oversized can systematically trimmed altered ob tain maximum efficiency ob taining match engine over size prop will allow engine reach desired rpm Reducing size prop ineffective areas will bring rpm up keeping greatest size efficient areas propellers de scribed oversized reasons prop desired pitch can produced easily block method Once pitch blade angles known prop blank fabricated accu rately Carving blades automatically results proper pitch blades can have type airfoil affecting pitch secret blank must have square corners opposite sides parallel physical size cross sec tion blank station blade determines pitch station Thus pitch can varied along blade adjusting size prop blankin top view side view combination _ 0 0 0 4 z 0 C 01 U Lii 0 I 0 0 0 -J 0 -J Lii 2Z 1 0 z cr1 0z DC 4 z 0 C C wx 0 LU 04 z 10 0 0 HZ LJa Cod 0 0 z A0 0 Lii 0 0 U -J 0J 0 0Z OC -Jot 0 OH -iw uJI IH 0 Z 3 6 Z C 0 Lii 0 DC 4 C Zx 9 C Lii Uz wO I0 0 0-a0~ Q:U -J-J 4 00 LaiZ 1 U 6 z n-Lii~I H0-I C0 0 aIa HI0 C T I0 i~C aH C Li0 4 -I K 4-00 H Li-Lii HH Z 0 4 IC C 0 H 4Ij _________________________________ _ LLJ HI 0CD Lii Ua CD V H a-A-- --v --0 H 0 4 -J U H 4 -J Lii Haz a-C I -J UcD H 0 ILi Lii Lii U ii C 0o Lii Q.0C June1978 31 CENTER LINE OF PROP SHAFT DISTANCE THAT BLADE TRAVELS AT EACH STATION IN ONE REVOLUTION TrXD _ _ 2A 11A 3 60%TIPC / / BLADE ANGLE LINES ____________________________________________B PARALLELOGRAM TO DETERMINE PROPELLER BLADE ANGLES two Accuracy pitch obtained using diagonal reference line runs lower corner blank oppo site upper corner station diag onal true pitch angle particular blade station Any type airfoil can formed around diagonal accuracy propeller depends entirely upon prop blank used therefore accurate method laying out blank necessary diagram shown Grant parallelogram accurately deter mines proper blade angles given pitch throughout stations blade prop blank laid out using simple templates wood machined scribed outlines However before templates can made dimensions must obtained parallelogram pro vides dimensions description diagram No 1 standard prop references deviations pertain long dimension A-B represents distance tip will travel revolu tion circumference prop disc distance other stations travel por tion A-B short dimension B-C distance forward propeller will move did slip revolution theoretical pitch line drawn point station blade will create proper blade angle given pitch station blade angles greatest near hub become lower distance hub increased prop produced true parallelo gram called helical pitch com monly used propeller because pitch re mains constant throughout blade result prop describes true helix moves forward helical propel ler blade forces proportional throughout blade same method can used slight alteration determine correct blade angles prop does have helical pitch common variation use pro gressive pitch pitch higher center lower tip Progressive pitch increases pitch area prop travels least distance thus requires less power reduces pitch dis PROP ROTATION GREATER PRECESSIONANGLE NORMAL CESSION EFFECT tance traveled greatest power absorption heaviest increas ing efficiency propeller Tests confirm dotted lines par allelogram show method used deter proper blade angles progres sive pitch example shows progres sive pitch prop same average pitch used helical pitch prop similar method can used obtain blade angles pitch desired particular sta tion blade example some com mercial props have much lower pitch center about station No 3 rest blade angles also can determined parallelogram parallelogram can make templates needed lay out blank control factor top front view prop side-view template de veloped top-view template top view blade shape view controlled largely width blade location width blade Basic design tells us width should great possible widths 7 12% diameter within proved parameters Secondly maxi mum efficiency width should about 60% station would also like blade shape would create equal air loads station blade Just because some blade shape looks pretty does mean best action prop blade said loaded creating resultant force works resultant force accumulation forces created station blade force station created blade angle pitch blade width airfoil constant pitch fixed alteration amount force station needed must accomplished varying blade width Station widths control blade shape working very high propel ler speeds tip speeds approach Mach can often see effect compressibility practice see props said cavitate flutter vibrate high rpm Such result often material and/or workmanship ever should sure cause otherwise effort can wrong direction Cavitation also can caused pro peller blade properly loaded load should equal throughout blade prevent fluttering vibration design blade shape controls know areas least efficiency hub tip maximum 32 Model Aviation F blade width fixed 60% station Fortunately use practical dimensions hub tip connect smooth flowing lines maximum width arrive useable shape should discover cavitation during tests altering blade shape suspect stations may very well equalize blade load cure needed Diagram No 1 commonly used suc cessful blade shape basic shape width desired prop known 60% station No 3 move up line A-F parallelogram until right-angle dimension line A-F diagonal line A-3 exactly red blade width point drop per pendicular line down crossing line A-B When rectangle completed about point shown maxi mum size prop blank Theoretically can now determine correct station cross sections measuring diagonal angle line crosses cross-sec tion outline station No 3 practical since required strength would lacking hub tips would taper Therefore lay out topview shape would like sufficient width strength hub narrow tip Once shape deter mined width blank known station POSSIBLE AIRFOILS depth blank station can found two ways First ob tain depths same way done maximum width measuring line A-F proper angle line doubling dimension point line A-B perhaps accurately measuring angle station laying out cross section station top view determining depth angle line See diagram No Once have required depths blank station side-view tem plate can laid out center line drawn various station lines erec ed about depth dimensions station bisected about center line points station connected smoothly make outline sideview template Due width pencil lines .measuring errors best make template outlines double size paper transfer template ma terial Template material should dur able Metal thin plastic sheet fine Once outline material lining up template wood facilitated prop shaft hole drilled center top view template small view ing hole drilled center side view template important out line template undersized enough allow width pen line marking actual blank Using tem plates next step draw outlines wood simple way cut strips wood about maximum size templates drill prop shaft hole squarely center blank done top-view outline made wood machined out line side-view outline made using center line wood line up side-view template least affected changes prop design will dis cuss first wish try stan dard prop use described tem plate layout wish try variations pitch such progression diagram No 2 shows top view remains same helical pitch side view changes vary thickness blank thicker pitch called thinner pitch less helical pitch type differ ences dimensions taken origi nal paper layout determine exact thick ness Considering blade sppeds can ap proach sonic speeds sweepback might advantage diagram shows tem plates standard prop template sweepback added ob tain sweepback side view laid out station dimensions taken trailing edge block instead center line Sweepback could also applied front view although would conflict other design advantages can used propeller blade effected two ces mechanical other aerody namic engine creates power turns propeller doing creates force within wood hold yardstick end slapping against desk top sound would indi cate amount force applied rotating stick through arc create slap arm originated force power transmitted mechani cally through wood stick desk felt result would cen ter line force moved through stick its end propeller also has mechanical force center line originates force generated engine shaft will center material blade stationright throught middle blade Continued page 90 June 1978 33 propeller blank ready carving developed b procedures ouxiinea article Sheet plastic templates shown R Standard No 1 propeller see drawings side-view template top view No 6 prop precession progressive pitch added Lets face folks AMA free flight RC glider events can provide fero cious competition anyone wants SAM events chance relaxation good fellowship importantly fun Painless Servo Mounts continuously perplexing problem converting Old Timer models radio has mounting servos fuselage frame sides Invariably end up using heavy maple motor-mount stock epoxied place sides cross members hold down servo tray Hardly neat light-weight method have recently used Ser-kit Buckeye Balsa 3330 Youngstown-Kingsville Road Cortland Oh 44410 find ideal oldtimer use consists two groved hard wood blocks 16 o tight-fitting rails slid adjusted fore aft optimum servo loca tion glued slots retained scraps left over cutting rails simple solution com plex problem Buckeye Balsa also has inventory sheet balsa balsa spruce strip 54 60 66 72 lengths Wood long lengths often needed construction really huge old timers avoid splicing Dee B Mathews 506 South Walnut Greensburg KS 67054 RC Pylon/Lane continued page 29 come event Nationals C B Enterprises has some success 800 sq Cosmic Wind design Scale Squadron Orange Coun ty California beginning get some interest going scale AT-6 Texan class AT-6 800 sq class thereabouts hope guys have ap parently upset February March articles will understand now am trying downgrade QM Formula look around people have dropped out QM Formula primary reasons planes going too fast cost too much know thats what racing about think its too bad events end up pros reaping benefits seems should room anyone wants compete QM Formula coming dead last time Hopefully have made model ers irate article think have aware average modelers would like compete other one-class racing limited design aircraft Hey guys Chicago area Mr Justice 1816 N Mozart Chicago IL would like get pylon racing wife Debra wishes caller wants know about duties caller about contacting Justices give some pointers racing am sure would appreciate have copy MNPRA manual published several years ago Debra would like read winner Reno Air Races last year entry American Air Rac ing Teams Top Turkey Figure three view what looked like ship modified Shoestring design Next month will have 3-view Team Tur keys new ship called Wild Turkey Dave Lane 447 W 136th St Haw thorne CA 90250 Make Props/de Bolt continued page 33 speak force applied pro peller As propeller works creates thrust force transmitted aircraft through blade material via engine shaft thrust would also have center line force Thrust result combi nation lift developed airfoil upper curve fan effect off bottom blade would line resultant between So resultant line thrust could parallel mechanical line thrust tip hub Ideally two lines thrust would same loca tion chord-wise torsional rotational force set up would tend rotate blade about mechanical line force can make variations stan dard design top view blade can approach ideal position lines force diagram No 3 show thrust line force can product review product review product review Pactra Aero-Poxy Pactra offers new line specially formulated 2-component system finishes Aero-Poxy tough fuel-proof marresistant one-coat armour finish designed endure rough handling fuel spillage unique formulation utilizes non-irritating non-sensitizing curing agent elimi nates dermatitic respiratory problems Aero-Poxy free lead hazards nontoxic dry Available colors gloss clear primer 8 oz onlyl choice Super Hi-Gloss Catalyst Flat Catalyst versatility finish color-mixing capabili ties Suitable brush spray Available 4- 8-oz cans plus thinners brushing spray 16- 32-oz cans Pactra Indus tries 7060 Hollywood Blvd Los Angeles CA 90028 product review product review product review 90 Model Aviation Kraftsmanship kit processed AAMCO GOLD BALSAThis Trainer will blow apart hits ground GREATEST B/C BASIC TRAINEB Design & Kit ALL TIME Ask over 25000 satisfied builders H-BAY dealers sold themSHALL WE SAY MORE Andrews Aircraft Model Co Inc US Rte 1& North Sc Topsfield Mass 01983 887-8541 Price $3995 kit pee dollar- bar em lined up mechanical line force remove tendency blade change pitch working would advantageous especially thin blades used Another design consideration preces sion no confused preces sion force created through gyroscopic action prop rotation Precession simply moving ahead point thrust would normally applied blade propeller arc normal blade shapes center line thrust coin cides line passes through center engine shaft looking front shaft top view pro peller blade center line rota tion blade angles created center As blade moves through arc rotation con sidered line along thrust generated Pitch also measured line center line thrust can moved ahead center line rotation effective angle blade arc rotation will increased changing physical angle advantage precession crease pitch adding drag Drag created physical angle blades precession change physical angle effective change pitch can used advantage air craft requires 7 pitch terminal ve locity precession prop pitch can 6 example will still have effective pitch 7 lower drag 6/4 physical pitch plus factor combined lower drag will allow engine rpm power drawback precession moves center line thrust away line mechanical force torsional rotation force created possible rigid blades torsional rotation force could disregarded taking advan tage precession instead stan dard prop shape precession added shown diagram No 4 Diagrams No 5 6 show design factors can incorporated blade shape Before finalizing ideas may wish try custom made props type blade airfoil should considered considerations blade airfoil same wing wish greatest lift possible least amount dragthe old L/D ratio again Secondly air speed should con sidered Formula propeller stance average blade air speed about 350 mph tip speed ap proaching sonic range An airfoil de veloped speed ranges would efficient modern airfoils have excellent lift-drag ratio far less drag older styles amount drag reduced serious loss lift result same adding horse power part II will show can transform thse ideas actual props own workshop Additionally will explain test tailor particular needs Nurnberg/Moulton continued page 38 Just gliders mostly scale eyccatching power kits after seeing Katos 20 & 40 versions Prettners Curare host electrics ranging Aeronauts BD-5 Udet Flamingo Graupners Elektra-fly Elektro-Max Queen show scribe undoubtedly 8-ft Svenson Storch 60s Its big rugged functional intended fly STOL lots power big prop fine pitch Fixed slats power ful flaps tail feathers plus longstroke landing gear rest won der no German firm did firstSven son Belgian Cessnas abound Cox RTF Carreras plastic Wichita replicas cater constant demand Graupner has gone Jodel Robin DR400 big way brochures say itll take new OS 90 especially used tow sailplanes Other big scale kits Wolfgang Rodel has MBB 233 Flamingo June1978 91
Edition: Model Aviation - 1978/06
Page Numbers: 30, 31, 32, 33, 90, 91
part Make Custom-made props particular airplane/engine combination can make racer fly faster twopart article author discusses month considera tions determine parameters special prop Development blank carving propeller will covered July issue U Harold deBolt Pron s TODAYS hobby shops offer us simple necessities Usually ready use least kit form lacking something can make own propellers have very wide variety ready mades available restricted what offered Very often propeller re quirements can very particular sizes needed maximum efficiency desired propeller experimenta tion desired considerable design re search woodworking knowledge necessary answer problem has reworking production props time consuming procedure often re sults inferior product shdrtcomings reworking nu merous Most often enough material allow desired changes Changes amounts types pitch restricted original design fixed design also prevents us obtain ing different blade shape Reworking allows us nothing alter someone elses propeller design may far ultimate Reworking can improve performance Have wondered production propel lers anywhere near perfection no ticed have changed little over years Does mean propeller design reached perfection years ago no such thing perfection what seems perfect today always improved morrow year seems bring better engines Maximum power obtained much higher rpm ever before Since prop controls rpm could changes prop design take better advantage en gine improvements Airplane performance direct result power available Assuming prop pitch correct speed airplane power available combination horsepower engine thrust developed propeller So pro peller efficiency important very powerful engine turning very inefficent propeller excellent cooling fan An efficient prop type engine would less ultimate diff erent engine particular type en gine requires different style propeller 30 Model Aviation propeller prototype shown picture has 9-in diameter width 3/4 Pitch 6-1/2 static rpm 20000 attains 27000 rpm flight According author normal unloading comes attention design reduction propeller drag High -Performance perfect match between engine prop experimentation required commercial prop necessarily ul timate purpose look ing performance air plane build scratch may design it reasonable positive engine-propeller combina tion correct before attempting im prove airplane Most modelers throw up hands suggested make own propellers However chore relatively simple inexpensive does require great skill no limit experi mentation ultimate found - duplication problem Would believe can produce propeller scratch less two hours time will explain basic design parame ters can used also will provide information needed produce prop wish workshop Required tools inexpensive materials com mon Check high school indus trial arts teacher might happy fabricate prop blanks class pro ject Before commencing need know diameter blade width blade shape pitch can change parameters time note results proper testing will have facts base improvements critical aspect incorpo rate exact pitch pitch character istics desired Once prop roughed out difficult alter pitch Choos ing amount pitch extremely im portant before commencing propel ler experimental rather duplicate advantageous make oversize design parameters except ptich An oversize propeller can altered desired way allowing room experimentation After prop roughed out can run engine oversized can systematically trimmed altered ob tain maximum efficiency ob taining match engine over size prop will allow engine reach desired rpm Reducing size prop ineffective areas will bring rpm up keeping greatest size efficient areas propellers de scribed oversized reasons prop desired pitch can produced easily block method Once pitch blade angles known prop blank fabricated accu rately Carving blades automatically results proper pitch blades can have type airfoil affecting pitch secret blank must have square corners opposite sides parallel physical size cross sec tion blank station blade determines pitch station Thus pitch can varied along blade adjusting size prop blankin top view side view combination _ 0 0 0 4 z 0 C 01 U Lii 0 I 0 0 0 -J 0 -J Lii 2Z 1 0 z cr1 0z DC 4 z 0 C C wx 0 LU 04 z 10 0 0 HZ LJa Cod 0 0 z A0 0 Lii 0 0 U -J 0J 0 0Z OC -Jot 0 OH -iw uJI IH 0 Z 3 6 Z C 0 Lii 0 DC 4 C Zx 9 C Lii Uz wO I0 0 0-a0~ Q:U -J-J 4 00 LaiZ 1 U 6 z n-Lii~I H0-I C0 0 aIa HI0 C T I0 i~C aH C Li0 4 -I K 4-00 H Li-Lii HH Z 0 4 IC C 0 H 4Ij _________________________________ _ LLJ HI 0CD Lii Ua CD V H a-A-- --v --0 H 0 4 -J U H 4 -J Lii Haz a-C I -J UcD H 0 ILi Lii Lii U ii C 0o Lii Q.0C June1978 31 CENTER LINE OF PROP SHAFT DISTANCE THAT BLADE TRAVELS AT EACH STATION IN ONE REVOLUTION TrXD _ _ 2A 11A 3 60%TIPC / / BLADE ANGLE LINES ____________________________________________B PARALLELOGRAM TO DETERMINE PROPELLER BLADE ANGLES two Accuracy pitch obtained using diagonal reference line runs lower corner blank oppo site upper corner station diag onal true pitch angle particular blade station Any type airfoil can formed around diagonal accuracy propeller depends entirely upon prop blank used therefore accurate method laying out blank necessary diagram shown Grant parallelogram accurately deter mines proper blade angles given pitch throughout stations blade prop blank laid out using simple templates wood machined scribed outlines However before templates can made dimensions must obtained parallelogram pro vides dimensions description diagram No 1 standard prop references deviations pertain long dimension A-B represents distance tip will travel revolu tion circumference prop disc distance other stations travel por tion A-B short dimension B-C distance forward propeller will move did slip revolution theoretical pitch line drawn point station blade will create proper blade angle given pitch station blade angles greatest near hub become lower distance hub increased prop produced true parallelo gram called helical pitch com monly used propeller because pitch re mains constant throughout blade result prop describes true helix moves forward helical propel ler blade forces proportional throughout blade same method can used slight alteration determine correct blade angles prop does have helical pitch common variation use pro gressive pitch pitch higher center lower tip Progressive pitch increases pitch area prop travels least distance thus requires less power reduces pitch dis PROP ROTATION GREATER PRECESSIONANGLE NORMAL CESSION EFFECT tance traveled greatest power absorption heaviest increas ing efficiency propeller Tests confirm dotted lines par allelogram show method used deter proper blade angles progres sive pitch example shows progres sive pitch prop same average pitch used helical pitch prop similar method can used obtain blade angles pitch desired particular sta tion blade example some com mercial props have much lower pitch center about station No 3 rest blade angles also can determined parallelogram parallelogram can make templates needed lay out blank control factor top front view prop side-view template de veloped top-view template top view blade shape view controlled largely width blade location width blade Basic design tells us width should great possible widths 7 12% diameter within proved parameters Secondly maxi mum efficiency width should about 60% station would also like blade shape would create equal air loads station blade Just because some blade shape looks pretty does mean best action prop blade said loaded creating resultant force works resultant force accumulation forces created station blade force station created blade angle pitch blade width airfoil constant pitch fixed alteration amount force station needed must accomplished varying blade width Station widths control blade shape working very high propel ler speeds tip speeds approach Mach can often see effect compressibility practice see props said cavitate flutter vibrate high rpm Such result often material and/or workmanship ever should sure cause otherwise effort can wrong direction Cavitation also can caused pro peller blade properly loaded load should equal throughout blade prevent fluttering vibration design blade shape controls know areas least efficiency hub tip maximum 32 Model Aviation F blade width fixed 60% station Fortunately use practical dimensions hub tip connect smooth flowing lines maximum width arrive useable shape should discover cavitation during tests altering blade shape suspect stations may very well equalize blade load cure needed Diagram No 1 commonly used suc cessful blade shape basic shape width desired prop known 60% station No 3 move up line A-F parallelogram until right-angle dimension line A-F diagonal line A-3 exactly red blade width point drop per pendicular line down crossing line A-B When rectangle completed about point shown maxi mum size prop blank Theoretically can now determine correct station cross sections measuring diagonal angle line crosses cross-sec tion outline station No 3 practical since required strength would lacking hub tips would taper Therefore lay out topview shape would like sufficient width strength hub narrow tip Once shape deter mined width blank known station POSSIBLE AIRFOILS depth blank station can found two ways First ob tain depths same way done maximum width measuring line A-F proper angle line doubling dimension point line A-B perhaps accurately measuring angle station laying out cross section station top view determining depth angle line See diagram No Once have required depths blank station side-view tem plate can laid out center line drawn various station lines erec ed about depth dimensions station bisected about center line points station connected smoothly make outline sideview template Due width pencil lines .measuring errors best make template outlines double size paper transfer template ma terial Template material should dur able Metal thin plastic sheet fine Once outline material lining up template wood facilitated prop shaft hole drilled center top view template small view ing hole drilled center side view template important out line template undersized enough allow width pen line marking actual blank Using tem plates next step draw outlines wood simple way cut strips wood about maximum size templates drill prop shaft hole squarely center blank done top-view outline made wood machined out line side-view outline made using center line wood line up side-view template least affected changes prop design will dis cuss first wish try stan dard prop use described tem plate layout wish try variations pitch such progression diagram No 2 shows top view remains same helical pitch side view changes vary thickness blank thicker pitch called thinner pitch less helical pitch type differ ences dimensions taken origi nal paper layout determine exact thick ness Considering blade sppeds can ap proach sonic speeds sweepback might advantage diagram shows tem plates standard prop template sweepback added ob tain sweepback side view laid out station dimensions taken trailing edge block instead center line Sweepback could also applied front view although would conflict other design advantages can used propeller blade effected two ces mechanical other aerody namic engine creates power turns propeller doing creates force within wood hold yardstick end slapping against desk top sound would indi cate amount force applied rotating stick through arc create slap arm originated force power transmitted mechani cally through wood stick desk felt result would cen ter line force moved through stick its end propeller also has mechanical force center line originates force generated engine shaft will center material blade stationright throught middle blade Continued page 90 June 1978 33 propeller blank ready carving developed b procedures ouxiinea article Sheet plastic templates shown R Standard No 1 propeller see drawings side-view template top view No 6 prop precession progressive pitch added Lets face folks AMA free flight RC glider events can provide fero cious competition anyone wants SAM events chance relaxation good fellowship importantly fun Painless Servo Mounts continuously perplexing problem converting Old Timer models radio has mounting servos fuselage frame sides Invariably end up using heavy maple motor-mount stock epoxied place sides cross members hold down servo tray Hardly neat light-weight method have recently used Ser-kit Buckeye Balsa 3330 Youngstown-Kingsville Road Cortland Oh 44410 find ideal oldtimer use consists two groved hard wood blocks 16 o tight-fitting rails slid adjusted fore aft optimum servo loca tion glued slots retained scraps left over cutting rails simple solution com plex problem Buckeye Balsa also has inventory sheet balsa balsa spruce strip 54 60 66 72 lengths Wood long lengths often needed construction really huge old timers avoid splicing Dee B Mathews 506 South Walnut Greensburg KS 67054 RC Pylon/Lane continued page 29 come event Nationals C B Enterprises has some success 800 sq Cosmic Wind design Scale Squadron Orange Coun ty California beginning get some interest going scale AT-6 Texan class AT-6 800 sq class thereabouts hope guys have ap parently upset February March articles will understand now am trying downgrade QM Formula look around people have dropped out QM Formula primary reasons planes going too fast cost too much know thats what racing about think its too bad events end up pros reaping benefits seems should room anyone wants compete QM Formula coming dead last time Hopefully have made model ers irate article think have aware average modelers would like compete other one-class racing limited design aircraft Hey guys Chicago area Mr Justice 1816 N Mozart Chicago IL would like get pylon racing wife Debra wishes caller wants know about duties caller about contacting Justices give some pointers racing am sure would appreciate have copy MNPRA manual published several years ago Debra would like read winner Reno Air Races last year entry American Air Rac ing Teams Top Turkey Figure three view what looked like ship modified Shoestring design Next month will have 3-view Team Tur keys new ship called Wild Turkey Dave Lane 447 W 136th St Haw thorne CA 90250 Make Props/de Bolt continued page 33 speak force applied pro peller As propeller works creates thrust force transmitted aircraft through blade material via engine shaft thrust would also have center line force Thrust result combi nation lift developed airfoil upper curve fan effect off bottom blade would line resultant between So resultant line thrust could parallel mechanical line thrust tip hub Ideally two lines thrust would same loca tion chord-wise torsional rotational force set up would tend rotate blade about mechanical line force can make variations stan dard design top view blade can approach ideal position lines force diagram No 3 show thrust line force can product review product review product review Pactra Aero-Poxy Pactra offers new line specially formulated 2-component system finishes Aero-Poxy tough fuel-proof marresistant one-coat armour finish designed endure rough handling fuel spillage unique formulation utilizes non-irritating non-sensitizing curing agent elimi nates dermatitic respiratory problems Aero-Poxy free lead hazards nontoxic dry Available colors gloss clear primer 8 oz onlyl choice Super Hi-Gloss Catalyst Flat Catalyst versatility finish color-mixing capabili ties Suitable brush spray Available 4- 8-oz cans plus thinners brushing spray 16- 32-oz cans Pactra Indus tries 7060 Hollywood Blvd Los Angeles CA 90028 product review product review product review 90 Model Aviation Kraftsmanship kit processed AAMCO GOLD BALSAThis Trainer will blow apart hits ground GREATEST B/C BASIC TRAINEB Design & Kit ALL TIME Ask over 25000 satisfied builders H-BAY dealers sold themSHALL WE SAY MORE Andrews Aircraft Model Co Inc US Rte 1& North Sc Topsfield Mass 01983 887-8541 Price $3995 kit pee dollar- bar em lined up mechanical line force remove tendency blade change pitch working would advantageous especially thin blades used Another design consideration preces sion no confused preces sion force created through gyroscopic action prop rotation Precession simply moving ahead point thrust would normally applied blade propeller arc normal blade shapes center line thrust coin cides line passes through center engine shaft looking front shaft top view pro peller blade center line rota tion blade angles created center As blade moves through arc rotation con sidered line along thrust generated Pitch also measured line center line thrust can moved ahead center line rotation effective angle blade arc rotation will increased changing physical angle advantage precession crease pitch adding drag Drag created physical angle blades precession change physical angle effective change pitch can used advantage air craft requires 7 pitch terminal ve locity precession prop pitch can 6 example will still have effective pitch 7 lower drag 6/4 physical pitch plus factor combined lower drag will allow engine rpm power drawback precession moves center line thrust away line mechanical force torsional rotation force created possible rigid blades torsional rotation force could disregarded taking advan tage precession instead stan dard prop shape precession added shown diagram No 4 Diagrams No 5 6 show design factors can incorporated blade shape Before finalizing ideas may wish try custom made props type blade airfoil should considered considerations blade airfoil same wing wish greatest lift possible least amount dragthe old L/D ratio again Secondly air speed should con sidered Formula propeller stance average blade air speed about 350 mph tip speed ap proaching sonic range An airfoil de veloped speed ranges would efficient modern airfoils have excellent lift-drag ratio far less drag older styles amount drag reduced serious loss lift result same adding horse power part II will show can transform thse ideas actual props own workshop Additionally will explain test tailor particular needs Nurnberg/Moulton continued page 38 Just gliders mostly scale eyccatching power kits after seeing Katos 20 & 40 versions Prettners Curare host electrics ranging Aeronauts BD-5 Udet Flamingo Graupners Elektra-fly Elektro-Max Queen show scribe undoubtedly 8-ft Svenson Storch 60s Its big rugged functional intended fly STOL lots power big prop fine pitch Fixed slats power ful flaps tail feathers plus longstroke landing gear rest won der no German firm did firstSven son Belgian Cessnas abound Cox RTF Carreras plastic Wichita replicas cater constant demand Graupner has gone Jodel Robin DR400 big way brochures say itll take new OS 90 especially used tow sailplanes Other big scale kits Wolfgang Rodel has MBB 233 Flamingo June1978 91
Edition: Model Aviation - 1978/06
Page Numbers: 30, 31, 32, 33, 90, 91
part Make Custom-made props particular airplane/engine combination can make racer fly faster twopart article author discusses month considera tions determine parameters special prop Development blank carving propeller will covered July issue U Harold deBolt Pron s TODAYS hobby shops offer us simple necessities Usually ready use least kit form lacking something can make own propellers have very wide variety ready mades available restricted what offered Very often propeller re quirements can very particular sizes needed maximum efficiency desired propeller experimenta tion desired considerable design re search woodworking knowledge necessary answer problem has reworking production props time consuming procedure often re sults inferior product shdrtcomings reworking nu merous Most often enough material allow desired changes Changes amounts types pitch restricted original design fixed design also prevents us obtain ing different blade shape Reworking allows us nothing alter someone elses propeller design may far ultimate Reworking can improve performance Have wondered production propel lers anywhere near perfection no ticed have changed little over years Does mean propeller design reached perfection years ago no such thing perfection what seems perfect today always improved morrow year seems bring better engines Maximum power obtained much higher rpm ever before Since prop controls rpm could changes prop design take better advantage en gine improvements Airplane performance direct result power available Assuming prop pitch correct speed airplane power available combination horsepower engine thrust developed propeller So pro peller efficiency important very powerful engine turning very inefficent propeller excellent cooling fan An efficient prop type engine would less ultimate diff erent engine particular type en gine requires different style propeller 30 Model Aviation propeller prototype shown picture has 9-in diameter width 3/4 Pitch 6-1/2 static rpm 20000 attains 27000 rpm flight According author normal unloading comes attention design reduction propeller drag High -Performance perfect match between engine prop experimentation required commercial prop necessarily ul timate purpose look ing performance air plane build scratch may design it reasonable positive engine-propeller combina tion correct before attempting im prove airplane Most modelers throw up hands suggested make own propellers However chore relatively simple inexpensive does require great skill no limit experi mentation ultimate found - duplication problem Would believe can produce propeller scratch less two hours time will explain basic design parame ters can used also will provide information needed produce prop wish workshop Required tools inexpensive materials com mon Check high school indus trial arts teacher might happy fabricate prop blanks class pro ject Before commencing need know diameter blade width blade shape pitch can change parameters time note results proper testing will have facts base improvements critical aspect incorpo rate exact pitch pitch character istics desired Once prop roughed out difficult alter pitch Choos ing amount pitch extremely im portant before commencing propel ler experimental rather duplicate advantageous make oversize design parameters except ptich An oversize propeller can altered desired way allowing room experimentation After prop roughed out can run engine oversized can systematically trimmed altered ob tain maximum efficiency ob taining match engine over size prop will allow engine reach desired rpm Reducing size prop ineffective areas will bring rpm up keeping greatest size efficient areas propellers de scribed oversized reasons prop desired pitch can produced easily block method Once pitch blade angles known prop blank fabricated accu rately Carving blades automatically results proper pitch blades can have type airfoil affecting pitch secret blank must have square corners opposite sides parallel physical size cross sec tion blank station blade determines pitch station Thus pitch can varied along blade adjusting size prop blankin top view side view combination _ 0 0 0 4 z 0 C 01 U Lii 0 I 0 0 0 -J 0 -J Lii 2Z 1 0 z cr1 0z DC 4 z 0 C C wx 0 LU 04 z 10 0 0 HZ LJa Cod 0 0 z A0 0 Lii 0 0 U -J 0J 0 0Z OC -Jot 0 OH -iw uJI IH 0 Z 3 6 Z C 0 Lii 0 DC 4 C Zx 9 C Lii Uz wO I0 0 0-a0~ Q:U -J-J 4 00 LaiZ 1 U 6 z n-Lii~I H0-I C0 0 aIa HI0 C T I0 i~C aH C Li0 4 -I K 4-00 H Li-Lii HH Z 0 4 IC C 0 H 4Ij _________________________________ _ LLJ HI 0CD Lii Ua CD V H a-A-- --v --0 H 0 4 -J U H 4 -J Lii Haz a-C I -J UcD H 0 ILi Lii Lii U ii C 0o Lii Q.0C June1978 31 CENTER LINE OF PROP SHAFT DISTANCE THAT BLADE TRAVELS AT EACH STATION IN ONE REVOLUTION TrXD _ _ 2A 11A 3 60%TIPC / / BLADE ANGLE LINES ____________________________________________B PARALLELOGRAM TO DETERMINE PROPELLER BLADE ANGLES two Accuracy pitch obtained using diagonal reference line runs lower corner blank oppo site upper corner station diag onal true pitch angle particular blade station Any type airfoil can formed around diagonal accuracy propeller depends entirely upon prop blank used therefore accurate method laying out blank necessary diagram shown Grant parallelogram accurately deter mines proper blade angles given pitch throughout stations blade prop blank laid out using simple templates wood machined scribed outlines However before templates can made dimensions must obtained parallelogram pro vides dimensions description diagram No 1 standard prop references deviations pertain long dimension A-B represents distance tip will travel revolu tion circumference prop disc distance other stations travel por tion A-B short dimension B-C distance forward propeller will move did slip revolution theoretical pitch line drawn point station blade will create proper blade angle given pitch station blade angles greatest near hub become lower distance hub increased prop produced true parallelo gram called helical pitch com monly used propeller because pitch re mains constant throughout blade result prop describes true helix moves forward helical propel ler blade forces proportional throughout blade same method can used slight alteration determine correct blade angles prop does have helical pitch common variation use pro gressive pitch pitch higher center lower tip Progressive pitch increases pitch area prop travels least distance thus requires less power reduces pitch dis PROP ROTATION GREATER PRECESSIONANGLE NORMAL CESSION EFFECT tance traveled greatest power absorption heaviest increas ing efficiency propeller Tests confirm dotted lines par allelogram show method used deter proper blade angles progres sive pitch example shows progres sive pitch prop same average pitch used helical pitch prop similar method can used obtain blade angles pitch desired particular sta tion blade example some com mercial props have much lower pitch center about station No 3 rest blade angles also can determined parallelogram parallelogram can make templates needed lay out blank control factor top front view prop side-view template de veloped top-view template top view blade shape view controlled largely width blade location width blade Basic design tells us width should great possible widths 7 12% diameter within proved parameters Secondly maxi mum efficiency width should about 60% station would also like blade shape would create equal air loads station blade Just because some blade shape looks pretty does mean best action prop blade said loaded creating resultant force works resultant force accumulation forces created station blade force station created blade angle pitch blade width airfoil constant pitch fixed alteration amount force station needed must accomplished varying blade width Station widths control blade shape working very high propel ler speeds tip speeds approach Mach can often see effect compressibility practice see props said cavitate flutter vibrate high rpm Such result often material and/or workmanship ever should sure cause otherwise effort can wrong direction Cavitation also can caused pro peller blade properly loaded load should equal throughout blade prevent fluttering vibration design blade shape controls know areas least efficiency hub tip maximum 32 Model Aviation F blade width fixed 60% station Fortunately use practical dimensions hub tip connect smooth flowing lines maximum width arrive useable shape should discover cavitation during tests altering blade shape suspect stations may very well equalize blade load cure needed Diagram No 1 commonly used suc cessful blade shape basic shape width desired prop known 60% station No 3 move up line A-F parallelogram until right-angle dimension line A-F diagonal line A-3 exactly red blade width point drop per pendicular line down crossing line A-B When rectangle completed about point shown maxi mum size prop blank Theoretically can now determine correct station cross sections measuring diagonal angle line crosses cross-sec tion outline station No 3 practical since required strength would lacking hub tips would taper Therefore lay out topview shape would like sufficient width strength hub narrow tip Once shape deter mined width blank known station POSSIBLE AIRFOILS depth blank station can found two ways First ob tain depths same way done maximum width measuring line A-F proper angle line doubling dimension point line A-B perhaps accurately measuring angle station laying out cross section station top view determining depth angle line See diagram No Once have required depths blank station side-view tem plate can laid out center line drawn various station lines erec ed about depth dimensions station bisected about center line points station connected smoothly make outline sideview template Due width pencil lines .measuring errors best make template outlines double size paper transfer template ma terial Template material should dur able Metal thin plastic sheet fine Once outline material lining up template wood facilitated prop shaft hole drilled center top view template small view ing hole drilled center side view template important out line template undersized enough allow width pen line marking actual blank Using tem plates next step draw outlines wood simple way cut strips wood about maximum size templates drill prop shaft hole squarely center blank done top-view outline made wood machined out line side-view outline made using center line wood line up side-view template least affected changes prop design will dis cuss first wish try stan dard prop use described tem plate layout wish try variations pitch such progression diagram No 2 shows top view remains same helical pitch side view changes vary thickness blank thicker pitch called thinner pitch less helical pitch type differ ences dimensions taken origi nal paper layout determine exact thick ness Considering blade sppeds can ap proach sonic speeds sweepback might advantage diagram shows tem plates standard prop template sweepback added ob tain sweepback side view laid out station dimensions taken trailing edge block instead center line Sweepback could also applied front view although would conflict other design advantages can used propeller blade effected two ces mechanical other aerody namic engine creates power turns propeller doing creates force within wood hold yardstick end slapping against desk top sound would indi cate amount force applied rotating stick through arc create slap arm originated force power transmitted mechani cally through wood stick desk felt result would cen ter line force moved through stick its end propeller also has mechanical force center line originates force generated engine shaft will center material blade stationright throught middle blade Continued page 90 June 1978 33 propeller blank ready carving developed b procedures ouxiinea article Sheet plastic templates shown R Standard No 1 propeller see drawings side-view template top view No 6 prop precession progressive pitch added Lets face folks AMA free flight RC glider events can provide fero cious competition anyone wants SAM events chance relaxation good fellowship importantly fun Painless Servo Mounts continuously perplexing problem converting Old Timer models radio has mounting servos fuselage frame sides Invariably end up using heavy maple motor-mount stock epoxied place sides cross members hold down servo tray Hardly neat light-weight method have recently used Ser-kit Buckeye Balsa 3330 Youngstown-Kingsville Road Cortland Oh 44410 find ideal oldtimer use consists two groved hard wood blocks 16 o tight-fitting rails slid adjusted fore aft optimum servo loca tion glued slots retained scraps left over cutting rails simple solution com plex problem Buckeye Balsa also has inventory sheet balsa balsa spruce strip 54 60 66 72 lengths Wood long lengths often needed construction really huge old timers avoid splicing Dee B Mathews 506 South Walnut Greensburg KS 67054 RC Pylon/Lane continued page 29 come event Nationals C B Enterprises has some success 800 sq Cosmic Wind design Scale Squadron Orange Coun ty California beginning get some interest going scale AT-6 Texan class AT-6 800 sq class thereabouts hope guys have ap parently upset February March articles will understand now am trying downgrade QM Formula look around people have dropped out QM Formula primary reasons planes going too fast cost too much know thats what racing about think its too bad events end up pros reaping benefits seems should room anyone wants compete QM Formula coming dead last time Hopefully have made model ers irate article think have aware average modelers would like compete other one-class racing limited design aircraft Hey guys Chicago area Mr Justice 1816 N Mozart Chicago IL would like get pylon racing wife Debra wishes caller wants know about duties caller about contacting Justices give some pointers racing am sure would appreciate have copy MNPRA manual published several years ago Debra would like read winner Reno Air Races last year entry American Air Rac ing Teams Top Turkey Figure three view what looked like ship modified Shoestring design Next month will have 3-view Team Tur keys new ship called Wild Turkey Dave Lane 447 W 136th St Haw thorne CA 90250 Make Props/de Bolt continued page 33 speak force applied pro peller As propeller works creates thrust force transmitted aircraft through blade material via engine shaft thrust would also have center line force Thrust result combi nation lift developed airfoil upper curve fan effect off bottom blade would line resultant between So resultant line thrust could parallel mechanical line thrust tip hub Ideally two lines thrust would same loca tion chord-wise torsional rotational force set up would tend rotate blade about mechanical line force can make variations stan dard design top view blade can approach ideal position lines force diagram No 3 show thrust line force can product review product review product review Pactra Aero-Poxy Pactra offers new line specially formulated 2-component system finishes Aero-Poxy tough fuel-proof marresistant one-coat armour finish designed endure rough handling fuel spillage unique formulation utilizes non-irritating non-sensitizing curing agent elimi nates dermatitic respiratory problems Aero-Poxy free lead hazards nontoxic dry Available colors gloss clear primer 8 oz onlyl choice Super Hi-Gloss Catalyst Flat Catalyst versatility finish color-mixing capabili ties Suitable brush spray Available 4- 8-oz cans plus thinners brushing spray 16- 32-oz cans Pactra Indus tries 7060 Hollywood Blvd Los Angeles CA 90028 product review product review product review 90 Model Aviation Kraftsmanship kit processed AAMCO GOLD BALSAThis Trainer will blow apart hits ground GREATEST B/C BASIC TRAINEB Design & Kit ALL TIME Ask over 25000 satisfied builders H-BAY dealers sold themSHALL WE SAY MORE Andrews Aircraft Model Co Inc US Rte 1& North Sc Topsfield Mass 01983 887-8541 Price $3995 kit pee dollar- bar em lined up mechanical line force remove tendency blade change pitch working would advantageous especially thin blades used Another design consideration preces sion no confused preces sion force created through gyroscopic action prop rotation Precession simply moving ahead point thrust would normally applied blade propeller arc normal blade shapes center line thrust coin cides line passes through center engine shaft looking front shaft top view pro peller blade center line rota tion blade angles created center As blade moves through arc rotation con sidered line along thrust generated Pitch also measured line center line thrust can moved ahead center line rotation effective angle blade arc rotation will increased changing physical angle advantage precession crease pitch adding drag Drag created physical angle blades precession change physical angle effective change pitch can used advantage air craft requires 7 pitch terminal ve locity precession prop pitch can 6 example will still have effective pitch 7 lower drag 6/4 physical pitch plus factor combined lower drag will allow engine rpm power drawback precession moves center line thrust away line mechanical force torsional rotation force created possible rigid blades torsional rotation force could disregarded taking advan tage precession instead stan dard prop shape precession added shown diagram No 4 Diagrams No 5 6 show design factors can incorporated blade shape Before finalizing ideas may wish try custom made props type blade airfoil should considered considerations blade airfoil same wing wish greatest lift possible least amount dragthe old L/D ratio again Secondly air speed should con sidered Formula propeller stance average blade air speed about 350 mph tip speed ap proaching sonic range An airfoil de veloped speed ranges would efficient modern airfoils have excellent lift-drag ratio far less drag older styles amount drag reduced serious loss lift result same adding horse power part II will show can transform thse ideas actual props own workshop Additionally will explain test tailor particular needs Nurnberg/Moulton continued page 38 Just gliders mostly scale eyccatching power kits after seeing Katos 20 & 40 versions Prettners Curare host electrics ranging Aeronauts BD-5 Udet Flamingo Graupners Elektra-fly Elektro-Max Queen show scribe undoubtedly 8-ft Svenson Storch 60s Its big rugged functional intended fly STOL lots power big prop fine pitch Fixed slats power ful flaps tail feathers plus longstroke landing gear rest won der no German firm did firstSven son Belgian Cessnas abound Cox RTF Carreras plastic Wichita replicas cater constant demand Graupner has gone Jodel Robin DR400 big way brochures say itll take new OS 90 especially used tow sailplanes Other big scale kits Wolfgang Rodel has MBB 233 Flamingo June1978 91