Better Props for Formula 1

better b0ttOTPr correct props has THIS ARTICLE dedicated aver age Form-I racing pilot hopefully offering assistance will help improve performance So Bob Violetts Terry Prathers keener competitive racing may offing As far speed concerned past year has paradox great Formula pilots powerful engines cannot improved much greater ex tent fairly equal equipment-wise question now arises come two pilots parallel equipment ability wind up miles apart performance Most year too pondered finally asking leading competitors very question After review equipment clued fact speed stems propeller effi ciency difference between average speed top speed depends entirely upon particular prop used merely tailor ing recommended stock prop bit aver age speed will sustained quite easily obtain top speed has find right prop work adjust experiment Never before has much speed gained critical match pro peller rest ones equipment Todays average racing speed still about same several years ago contrast top speed has increased dras tically New engines have changed dramatically matching right props now whole new ball game Previ ously much propeller used respect presently used speed easy come Today speed difficult realize because forced use smaller props match change engines Therefore speed crease relies propeller efficiency just size alone analyze situation answer 12 Model Aviation New engines have changed dramatically ti Test stand used measure thrust connection propeller experiments Above Required geod rpm meter capable measuring increments less 100 rpmone shown light-sensi tive type merely pointed spinning prop Below engine runs spring-loaded platform slides forward according scale side test measuring about 144 os thrust p ormUZG become whole new ball gameand na game twofold engine propeller design New much can accomplished propellers engines develop horsepower less help us gain speed Engines airplanes torque old-style engines Thus much have advanced extensively recent years smaller prop needed maintain propeller development has unfolded required rpm provide horsepower gradually Today prop manufacturers propeller should designed fit air- give us better workmanship materials plane -amount power turn size choice fail delve real propeller chosen approach research improve designs backwards Rules fix size airplane Years ago Tony Grish came forth amount power before fits Tornado prop dramatic improvement propeller An ideal size Form-I air- over previous offerings others plane propeller would times larger design resulted considerable research props forced use Therefore Tony developed Tornado through anything can done get use wind tunnel static-thrust malarger prop airplane would show chine another machine checked thrust dramatic increase speed performance speed plus extensive flight testing Grish though prop size increase may will long remembered dedication very large example older engines sports progress Regretfully less hp torque allowing use no Tony Grish today help solve present larger props resulting speeds similar prop problems continue attained higher rpm horse- prop improvement must act ourpower engines selves Frankly handcuffed engines Presently propeller design mystery designs require use horsepower us simply because very little rather torque can noth- information readily available com ing about engines conceivable mon belief props difficult make prop efficiency scratch experience can produce complete prop little time takes rework commercial prop article intended provide infor mation about propellers layman experiment perhaps discover what really does make special prop great safe assume special props far being ultimate Certainly some realistic experimental work along way will uncover something better will attempt explain what propeller actually what constitutes better propeller what design parameter should speed propeller plus results personal ex perimentation basic commercial props available understand what propeller actually forget normal thinking about moment jet engine pushes air plane through air perhaps peo ple believe propeller does just opposite pulling airplane Realisti cally propeller lifts airplane forward Visualize revolving propeller circular wing disc creates lift propeller K\ \ K- -T SORROW 0- -__ L 7, / 11 I I/ 4 PECTROSPROPPELLERI 4 OIGOER RPM2 PROPELLER [ r BLA 000 EINRECREARO 000004 TOIS AREAL ~TSLAMSR\ - LRSSRRAGMORER PU. K SCREASER THRAST ___ RECREASE ORAG IS TRIG AREA TREORETICAL OR LABALER PITA 0 I/ IPROPPELLORII May1977 13 COIUPARA FIC CR05 ESOELOPX0h1 POLL P000 CflIS&4PRSSRESIAE I_ design will easier understand amount lift thrust developed disc directly proportional density plus area determined propellers diameter Density controlled speed pro peller turns times blades revolve time segment plus width blades Speed time element blade revolutions given time element denser disc time blade develops X amount lift itself point discs circumference blade revolves 20000 times min ute lift developed 20000 X X greater course Density also controlled blade width wider blade larger segment disc covers Efficiency propel ler controlled its liftdrag ratio L/D unfortunately gets out propor tion blade width greater 12% diameter As explained further article commercial speed props use blade width 7% could improved upon obvious answer increase speed simply increase rpm however limited times propeller re volves given time forward motion the air disturbed Pro peller efficiency will suffer rpm comes too great particularly rpm does match forward speed aircraft example prop rpm too high slowflying model Tip speed another problem created too high rpm airfoil approaches approximately d sound shock waves begin generate creating greatly disturbed air plus considerable drag Shock waves can also cause propel ler blade flutter become useless Tip speed must considered choosing operating rpm propeller example tip speed 9-in diameter pro peller 22000 rpm 589 mph sonic range maximum rpm restricted answer have obtain aircraft speed increase propeller disc size fill disc better through use wider prop blade and/or increase pro peller pitch What pitch Simply stated pitch distance propeller moves forward revolution used solid substance pitch propeller has further ward will move greater aircraft speed rpm constant However pitch can also compared wings angle attack prop blade also wing Just wing does propeller blade will stall angle attack becomes too great pitch too high however un like wing propeller has advantage revolving moving forward Conse quently angle attack stall angle reduced explains able use higher angles props wings clear lower pitch propeller will provide quicker takeoff less speed terminal velocity reached amount speed gained increas ing pitch limited power avail able use also stalling point blade interesting higher inherent aircraft speed pitch can used because higher poten Pal forward speed Therefore cleaner designed aircraft compounds itself allowing use propeller pitch propeller considered similar 14 Model Aviation CHART NO 1 Data concerning what can expected usable propeller pitchs engine output Formula aircraft 6 propeller pitch @ 22000 RPM mph 7 propeller pitoh @ 22000 RPM mph 8 propeller pitoh 0 RPM mph 6 propeller pitch @ 24000 RPM mph 7 propeller pitch @ 24000 RPM mph 8 propeller pitch 24000 RPM mph 9 propeller pitch @ 20000 RPM mph 1 added pitch @ 22000 RPM mph @ 24000 RPM ph 2000 added RPM 6 pitch h 7 pitch mph 8 pitch ph Selected 1977 Hall Fame Harold deBolthere shown typically neat Formula test stand used articlewas pioneer field radio control 4 CHART NO 2 PropBlade BladeStatic No Brand Condition Diam Pitch Width Area Airroil RP Thrust 1 Stock 9711/16355 CY175k120oz 2 Stock 8 3/4711/16347 CY18k118oz 3 Stock 8 1/2711/1634 CY185k112oz 4 Rework 96 1/23/4342 C y18k120oz 5 JRework 8 1/46 1/23/4322 CY19k110oz 6 1 Stock 8 3/475/831 CY18k88oz 7 Rework 975/8322 Sym18k82oz 8 Rework 975/8327 Sym182k85oz 9 Rework 8 3/485/8312 Sym175k78oz CY Clark Yin Sym SymmetricalDiam pitch & width ininches Blade Areain 1/8 sq RPM-Kiooc 5/8 narrowblade 10 JRework 8 1/2613/16385 CY20k140oz BLADE SHAPES OF THE TEST PROPELLERS -CHART 3 1456789 10 wing much lift does prop have Form-I wing flight can generate several times aircrafts weight generates its greatest lift its maximum angle attack balanced model flown level flight wing incidence maximum angle attack will rise vertically Would 50 mph sound logical know Form-I nose pointed vertically out level flight will go straight up great loss speed Propeller lift far greater lift wing capable well good stand still realize what constitutes better propeller Obviously larger diameter thus disc size greater amount lift Diameter increase will help other parameters remain con stant -in larger diameter will increase disc area 12% excellent goal strive Disc fill controlled rpm blade width therefore props should designed maximum rpm within sub sonic tip-speed range Keep blade width great possible sustaining effi cient L/D ratio course blade airfoil should generate greatest amount lift possible problem being high-lift airfoils gen erally create considerable drag Drag criterion propeller design should overlook primarily because amount engine power fixed Thus drag major reason propellers maximum rpm limited Drag created propeller size di ameter amount blade area shape blade airfoil used amount pitch surface finish other words everything used creates drag does nothing detract good performance study current commercial props indicates drag reduction greatest possible improve ment manufacturers can make design Let us review potential channels pursue reduce drag Maintaining maximum diameter possible reducing blade width low minimum greatest factor contributes lift also fitting impor tant needs model Amount pitch fixed factor sus taining performance except possi bility cheating pitch bit reduce drag Propeller efficiency goes 0% props hub 100% 2/3 station blade 100% down zero again very tip Progression con stant hub out variable 2/3 station out because tip nearly reached before lift falls off rapidly Blade speed greatest tip because tip has travel much further hub does complete revolution Pro peller designers have proven advantages using progressive pitch Using pitch needed 2/3 station lesser hub 2/3 station lesser tip 2/3 station average will true amount pitch desired procedure reduces drag Actual pitch needed determined terminal velocity model design point drag design equals amount propeller thrust Terminal velocity varies according model design clean design will have higher terminal velocity less streamlined model thus greater pro peller efficiency realized No data available exact speed models some assumptions born out mathe matics can made racing fly approximately 130mph around pylons faster straights slower turns slower due deceleration turns Propeller pitches use realm reality speed therefore striving about 7 pitch good start ing point experimentation Blade width helps increase propeller disc lift reason use wide blade possible test data proves further along article blade width does detract too much rpm does add greatly static thrust another racing fac tor considered static thrust greater aircraft acceleration will Acceleration affects racing speeds take off coming out turns No big drag increase realized using wider blade Propeller designs have maximum width 2/3 point progress abso lute minimum tip hub however reduction much area sections typical narrow blade designs Increasing blade width 10 20% will cause dramatic thrust increase therefore width experiments safe up 12% diameter beyond efficiency begins deteriorate Shape blade imperative tie three necessary points together hub 2/3 point tip Naturally blade shape affects drag keep smooth possible least disturbance Referring back pitch progression again same idea may used area reduce drag simply decrease area least efficient portions blade increase area 2/3 station Continued page 90 May1977 15 NEW FORD TRI MOTOR 1195 Unique because such amazing scale det kits relatively e i somethifl suel 0ur ~edgifl ~flIFledgli yOU thour ne~0 channel till yOU see tIler Wait sprifl b0015 nOCl youVa clearly shown Will . -iignly detailed Plastic Parts t uung touch realism-in-miniature NEW BEGINNERS ZERO ERSCHMni 495 Nifty control line models Theyre easiest ones world assembleall wood no tissue coveringonly 6 9 parts depending model ex cept Biplanes have few Genuine Nylon motor mount THEYRE AT YOUR DEALER GET OVER AND SEE THEM NOW . Better Props/deBolt continued page 15 realize enough average area Propeller blade airfoil place large drag reduction can achieved given engine fast fighter-type full-scale aircraft may have semi-symmetrical air foil its larger diameter propeller load carrying aircraft has flat-bottom undercambered airfoil lesson learned semi-symmetrical air foil has much less drag lower life fac tor Obviously use some blade lift lost lower drag allows larger di ameter given amount power propeller disc area increased really important blade lift loss flying load carrying aircraft speed important ability lift maximum amount weight weight loads propeller down use high-lift blade important flying fighter plane drag aircraft itself loads prop weight does higher flying speed possible achieve just much efficien cy streamlined airfoil blade efficiency being close same propel ler disc area much larger produces plus factor 360 mph average operating speed models propeller range reached streamlined airfoil ready bolt placeComplete control system less handle lines decals landing gear wheels etc makes building cinch assembly literally minutes can use 049 en2ine much efficient Clark Y type because speed above 100 mph drastically increases drag flat-bottom sections Finish propeller affects drag just finish does rest airplane cause its small size high speed comparison wing roughness has proportionally greater effect pro peller other part airplane above characteristics affect propeller performance Assuming pro peller designers producers have already considered good performance con sequence talents perhaps something average model-builder /flier can own increase propel ler performance Propeller engineers aware two ways pitch can built propeller having labeled helical progressive pitch amount helical pitch constant throughout length blade progressive pitch higher desired pitch angle used efficient station blade lower desired pitch angle used least efficient stations average desired pitch Progressive pitch results higher pro peller rpm due reduction drag stations prop efficiency lowest comparison thrust developed heli cal progressive pitch propellers shows use some progression can advantage Progression may also ap plied blade shape using less area less efficient stations effi cient stations time another Form-I pilots have washed out tips prop because progressive pitch found help Just check stock prop performance before after progression added note improvement Moder ate progression will yield additional 500 rpm plus cutting few seconds racing time logical assume some really interest ing prop improvements lie ahead ideas applied have experimented props consid erably over years extensively would have liked have done neverthe less results positive equip ment consisted standard Formula-I air craft K&B engines good tachometer respectable thrust stand elbow grease Consequently efforts never created national records greatly improved aircraft performance Commercial props limit work expansion because lack sufficient mate rial must either start scratch locate usable prop increase per formance Both approaches will net worth results Several charts presented arti cle help understand workings propeller own test results shown Chart #1 indicates theoretical speeds ob tained using various common propeller pitches results have adjusted 80% propeller efficiency Chart rpm true engine rpm air Expect pick-up least 10% air rpm over ground rpm known unloading course evaluating propeller remember called good prop always ap pears unload less efficient Simple mathematics will render several interesting things Note speed increase pitch added keeping rpm constant Re ducing drag given size prop will cause rpm rise Adding pitch will crease mph maintaining original rpm rpm range adding 1 pitch will increase mph up 17 miles gain amount speed increasing rpm keeping same pitch must add 3700 rpm aware dif ficulty gain 500 rpm range logical experiment props engines chart also indicates expected per formance called torque-type en gines versus engines dependent upon pure horsepower figures presented stem new horsepower type engines Previ ously torque-type engines allowed better propeller efficiency giving equivalent air speeds lower rpm engines could turn 9 diameter X 9 pitch prop 20000 rpm equivalent 136 mph too bad engine power cannot increased torque rather rpm would applicable propeller Charts #2 #3 denote test results several proven good Formula-I propel lers labeled stock exactly However sizes chosen such 90 Model Aviation KIT 12 SPAN 34j~ SCALE 4 1 Ft TIGER MOTH 1295 ALL 72MHz 27MHz SYSTEMS NOW Ready delivery Featuring interference resistant transmitter receiver combination available trade Radiates highest signal level yes unit market today Proven helicopter capability Demonstratably faster powerful servos outstand ing resolution centering Stick assemblies smooth silk through out temperature range 10 1200F Transmitter control stick unit designed maximum comfort has feel instills confidence re duces fatigue Reliability has design goal Full 6 months warranty immediate factory servicing Study spec sheet free asking compare anything now being offered Youll see believe know VARIANT way go Visit us Toledo Show WESTPORT INTERNATIONAL INC 347 Boston Post Road Milford Conn 06460 will yield peak flight performance stock props Reworked props have tailored according ideas presented article Primarily diameter and/or pitch increase over acceptable stock props strived keeping rpm maximum engine horsepower range exten sive original prop work completed props checked excellent mula-I aircraft K&B 40 S III en gine flown proven competitive Chart information presented ob tained running session accu rate comparisons Results achieved inferior engine running under far ideal climatic conditions rpm shown about 2000 rpm below normal engine expectancy under better conditions Test equipment used K&B S III engine expanded meter photo cell tach ometer specially built thrust stand Engine tach purchased items nothing special thrust stand precision built fulfilling lifelong desire Although thrust stand readings needed comparative accurate Highest speed prop thrust reading 144 oz 9 lbs great deal thrust 40 cubic inch engine indicating outstanding work en gine manufacturers have extended us last few years interesting know stunt-type propeller yields considerably static thrust best speed props Chart #3 presented evaluation differences tested blade shapes No tempt has ever made experiment blade shape specific size propeller however chart comparisons dicate work area could beneficial According chart #2s test results expected determine super prop frankly super prop yet developed tests really show consequences alternating various de sign parameters example first three tests made same prop simply clipping tips time reduce diameter marked rpm crease indicates added horsepower small static thrust loss increased aircraft speed Remember test conducted starting too much prop same improvement can expected using right size prop beginning Note large static thrust increase gained wider blade width Such has proven beneficial actual racing symmetrical airfoil experiments drag reduction interesting changing lower drag airfoil diameter pitch increased horsepower loss Symmetrical airfoil props have used actual race performances yet flight tests indicate show great promise profitable future development conclusion purpose article hopefully incite intelligent speed propeller experimentation field Past racing performances too us have proven considerably propeller efficiency improvement sorely needed nation-wide break sound barrier someday must work ourselves fellow racers lets get up go Radio Technique/Myers continued page 11 glow-plug energizer have both switches 15 VDC side can light glow plug cant charge pack both switches 48 VDC side can charge pack cant light glow plug switch set direction pack Off cant anything except possibly draw current cell number 1 theres some way connect between 8 terminal Since already know least cells bad install piece wire place cell #1 theres no way draw current switches opposing positions can get fancy put whole thing plastic case 0-to-S Amp meter iron-vane types preferred durability low cost May1977 91

better b0ttOTPr correct props has THIS ARTICLE dedicated aver age Form-I racing pilot hopefully offering assistance will help improve performance So Bob Violetts Terry Prathers keener competitive racing may offing As far speed concerned past year has paradox great Formula pilots powerful engines cannot improved much greater ex tent fairly equal equipment-wise question now arises come two pilots parallel equipment ability wind up miles apart performance Most year too pondered finally asking leading competitors very question After review equipment clued fact speed stems propeller effi ciency difference between average speed top speed depends entirely upon particular prop used merely tailor ing recommended stock prop bit aver age speed will sustained quite easily obtain top speed has find right prop work adjust experiment Never before has much speed gained critical match pro peller rest ones equipment Todays average racing speed still about same several years ago contrast top speed has increased dras tically New engines have changed dramatically matching right props now whole new ball game Previ ously much propeller used respect presently used speed easy come Today speed difficult realize because forced use smaller props match change engines Therefore speed crease relies propeller efficiency just size alone analyze situation answer 12 Model Aviation New engines have changed dramatically ti Test stand used measure thrust connection propeller experiments Above Required geod rpm meter capable measuring increments less 100 rpmone shown light-sensi tive type merely pointed spinning prop Below engine runs spring-loaded platform slides forward according scale side test measuring about 144 os thrust p ormUZG become whole new ball gameand na game twofold engine propeller design New much can accomplished propellers engines develop horsepower less help us gain speed Engines airplanes torque old-style engines Thus much have advanced extensively recent years smaller prop needed maintain propeller development has unfolded required rpm provide horsepower gradually Today prop manufacturers propeller should designed fit air- give us better workmanship materials plane -amount power turn size choice fail delve real propeller chosen approach research improve designs backwards Rules fix size airplane Years ago Tony Grish came forth amount power before fits Tornado prop dramatic improvement propeller An ideal size Form-I air- over previous offerings others plane propeller would times larger design resulted considerable research props forced use Therefore Tony developed Tornado through anything can done get use wind tunnel static-thrust malarger prop airplane would show chine another machine checked thrust dramatic increase speed performance speed plus extensive flight testing Grish though prop size increase may will long remembered dedication very large example older engines sports progress Regretfully less hp torque allowing use no Tony Grish today help solve present larger props resulting speeds similar prop problems continue attained higher rpm horse- prop improvement must act ourpower engines selves Frankly handcuffed engines Presently propeller design mystery designs require use horsepower us simply because very little rather torque can noth- information readily available com ing about engines conceivable mon belief props difficult make prop efficiency scratch experience can produce complete prop little time takes rework commercial prop article intended provide infor mation about propellers layman experiment perhaps discover what really does make special prop great safe assume special props far being ultimate Certainly some realistic experimental work along way will uncover something better will attempt explain what propeller actually what constitutes better propeller what design parameter should speed propeller plus results personal ex perimentation basic commercial props available understand what propeller actually forget normal thinking about moment jet engine pushes air plane through air perhaps peo ple believe propeller does just opposite pulling airplane Realisti cally propeller lifts airplane forward Visualize revolving propeller circular wing disc creates lift propeller K\ \ K- -T SORROW 0- -__ L 7, / 11 I I/ 4 PECTROSPROPPELLERI 4 OIGOER RPM2 PROPELLER [ r BLA 000 EINRECREARO 000004 TOIS AREAL ~TSLAMSR\ - LRSSRRAGMORER PU. K SCREASER THRAST ___ RECREASE ORAG IS TRIG AREA TREORETICAL OR LABALER PITA 0 I/ IPROPPELLORII May1977 13 COIUPARA FIC CR05 ESOELOPX0h1 POLL P000 CflIS&4PRSSRESIAE I_ design will easier understand amount lift thrust developed disc directly proportional density plus area determined propellers diameter Density controlled speed pro peller turns times blades revolve time segment plus width blades Speed time element blade revolutions given time element denser disc time blade develops X amount lift itself point discs circumference blade revolves 20000 times min ute lift developed 20000 X X greater course Density also controlled blade width wider blade larger segment disc covers Efficiency propel ler controlled its liftdrag ratio L/D unfortunately gets out propor tion blade width greater 12% diameter As explained further article commercial speed props use blade width 7% could improved upon obvious answer increase speed simply increase rpm however limited times propeller re volves given time forward motion the air disturbed Pro peller efficiency will suffer rpm comes too great particularly rpm does match forward speed aircraft example prop rpm too high slowflying model Tip speed another problem created too high rpm airfoil approaches approximately d sound shock waves begin generate creating greatly disturbed air plus considerable drag Shock waves can also cause propel ler blade flutter become useless Tip speed must considered choosing operating rpm propeller example tip speed 9-in diameter pro peller 22000 rpm 589 mph sonic range maximum rpm restricted answer have obtain aircraft speed increase propeller disc size fill disc better through use wider prop blade and/or increase pro peller pitch What pitch Simply stated pitch distance propeller moves forward revolution used solid substance pitch propeller has further ward will move greater aircraft speed rpm constant However pitch can also compared wings angle attack prop blade also wing Just wing does propeller blade will stall angle attack becomes too great pitch too high however un like wing propeller has advantage revolving moving forward Conse quently angle attack stall angle reduced explains able use higher angles props wings clear lower pitch propeller will provide quicker takeoff less speed terminal velocity reached amount speed gained increas ing pitch limited power avail able use also stalling point blade interesting higher inherent aircraft speed pitch can used because higher poten Pal forward speed Therefore cleaner designed aircraft compounds itself allowing use propeller pitch propeller considered similar 14 Model Aviation CHART NO 1 Data concerning what can expected usable propeller pitchs engine output Formula aircraft 6 propeller pitch @ 22000 RPM mph 7 propeller pitoh @ 22000 RPM mph 8 propeller pitoh 0 RPM mph 6 propeller pitch @ 24000 RPM mph 7 propeller pitch @ 24000 RPM mph 8 propeller pitch 24000 RPM mph 9 propeller pitch @ 20000 RPM mph 1 added pitch @ 22000 RPM mph @ 24000 RPM ph 2000 added RPM 6 pitch h 7 pitch mph 8 pitch ph Selected 1977 Hall Fame Harold deBolthere shown typically neat Formula test stand used articlewas pioneer field radio control 4 CHART NO 2 PropBlade BladeStatic No Brand Condition Diam Pitch Width Area Airroil RP Thrust 1 Stock 9711/16355 CY175k120oz 2 Stock 8 3/4711/16347 CY18k118oz 3 Stock 8 1/2711/1634 CY185k112oz 4 Rework 96 1/23/4342 C y18k120oz 5 JRework 8 1/46 1/23/4322 CY19k110oz 6 1 Stock 8 3/475/831 CY18k88oz 7 Rework 975/8322 Sym18k82oz 8 Rework 975/8327 Sym182k85oz 9 Rework 8 3/485/8312 Sym175k78oz CY Clark Yin Sym SymmetricalDiam pitch & width ininches Blade Areain 1/8 sq RPM-Kiooc 5/8 narrowblade 10 JRework 8 1/2613/16385 CY20k140oz BLADE SHAPES OF THE TEST PROPELLERS -CHART 3 1456789 10 wing much lift does prop have Form-I wing flight can generate several times aircrafts weight generates its greatest lift its maximum angle attack balanced model flown level flight wing incidence maximum angle attack will rise vertically Would 50 mph sound logical know Form-I nose pointed vertically out level flight will go straight up great loss speed Propeller lift far greater lift wing capable well good stand still realize what constitutes better propeller Obviously larger diameter thus disc size greater amount lift Diameter increase will help other parameters remain con stant -in larger diameter will increase disc area 12% excellent goal strive Disc fill controlled rpm blade width therefore props should designed maximum rpm within sub sonic tip-speed range Keep blade width great possible sustaining effi cient L/D ratio course blade airfoil should generate greatest amount lift possible problem being high-lift airfoils gen erally create considerable drag Drag criterion propeller design should overlook primarily because amount engine power fixed Thus drag major reason propellers maximum rpm limited Drag created propeller size di ameter amount blade area shape blade airfoil used amount pitch surface finish other words everything used creates drag does nothing detract good performance study current commercial props indicates drag reduction greatest possible improve ment manufacturers can make design Let us review potential channels pursue reduce drag Maintaining maximum diameter possible reducing blade width low minimum greatest factor contributes lift also fitting impor tant needs model Amount pitch fixed factor sus taining performance except possi bility cheating pitch bit reduce drag Propeller efficiency goes 0% props hub 100% 2/3 station blade 100% down zero again very tip Progression con stant hub out variable 2/3 station out because tip nearly reached before lift falls off rapidly Blade speed greatest tip because tip has travel much further hub does complete revolution Pro peller designers have proven advantages using progressive pitch Using pitch needed 2/3 station lesser hub 2/3 station lesser tip 2/3 station average will true amount pitch desired procedure reduces drag Actual pitch needed determined terminal velocity model design point drag design equals amount propeller thrust Terminal velocity varies according model design clean design will have higher terminal velocity less streamlined model thus greater pro peller efficiency realized No data available exact speed models some assumptions born out mathe matics can made racing fly approximately 130mph around pylons faster straights slower turns slower due deceleration turns Propeller pitches use realm reality speed therefore striving about 7 pitch good start ing point experimentation Blade width helps increase propeller disc lift reason use wide blade possible test data proves further along article blade width does detract too much rpm does add greatly static thrust another racing fac tor considered static thrust greater aircraft acceleration will Acceleration affects racing speeds take off coming out turns No big drag increase realized using wider blade Propeller designs have maximum width 2/3 point progress abso lute minimum tip hub however reduction much area sections typical narrow blade designs Increasing blade width 10 20% will cause dramatic thrust increase therefore width experiments safe up 12% diameter beyond efficiency begins deteriorate Shape blade imperative tie three necessary points together hub 2/3 point tip Naturally blade shape affects drag keep smooth possible least disturbance Referring back pitch progression again same idea may used area reduce drag simply decrease area least efficient portions blade increase area 2/3 station Continued page 90 May1977 15 NEW FORD TRI MOTOR 1195 Unique because such amazing scale det kits relatively e i somethifl suel 0ur ~edgifl ~flIFledgli yOU thour ne~0 channel till yOU see tIler Wait sprifl b0015 nOCl youVa clearly shown Will . -iignly detailed Plastic Parts t uung touch realism-in-miniature NEW BEGINNERS ZERO ERSCHMni 495 Nifty control line models Theyre easiest ones world assembleall wood no tissue coveringonly 6 9 parts depending model ex cept Biplanes have few Genuine Nylon motor mount THEYRE AT YOUR DEALER GET OVER AND SEE THEM NOW . Better Props/deBolt continued page 15 realize enough average area Propeller blade airfoil place large drag reduction can achieved given engine fast fighter-type full-scale aircraft may have semi-symmetrical air foil its larger diameter propeller load carrying aircraft has flat-bottom undercambered airfoil lesson learned semi-symmetrical air foil has much less drag lower life fac tor Obviously use some blade lift lost lower drag allows larger di ameter given amount power propeller disc area increased really important blade lift loss flying load carrying aircraft speed important ability lift maximum amount weight weight loads propeller down use high-lift blade important flying fighter plane drag aircraft itself loads prop weight does higher flying speed possible achieve just much efficien cy streamlined airfoil blade efficiency being close same propel ler disc area much larger produces plus factor 360 mph average operating speed models propeller range reached streamlined airfoil ready bolt placeComplete control system less handle lines decals landing gear wheels etc makes building cinch assembly literally minutes can use 049 en2ine much efficient Clark Y type because speed above 100 mph drastically increases drag flat-bottom sections Finish propeller affects drag just finish does rest airplane cause its small size high speed comparison wing roughness has proportionally greater effect pro peller other part airplane above characteristics affect propeller performance Assuming pro peller designers producers have already considered good performance con sequence talents perhaps something average model-builder /flier can own increase propel ler performance Propeller engineers aware two ways pitch can built propeller having labeled helical progressive pitch amount helical pitch constant throughout length blade progressive pitch higher desired pitch angle used efficient station blade lower desired pitch angle used least efficient stations average desired pitch Progressive pitch results higher pro peller rpm due reduction drag stations prop efficiency lowest comparison thrust developed heli cal progressive pitch propellers shows use some progression can advantage Progression may also ap plied blade shape using less area less efficient stations effi cient stations time another Form-I pilots have washed out tips prop because progressive pitch found help Just check stock prop performance before after progression added note improvement Moder ate progression will yield additional 500 rpm plus cutting few seconds racing time logical assume some really interest ing prop improvements lie ahead ideas applied have experimented props consid erably over years extensively would have liked have done neverthe less results positive equip ment consisted standard Formula-I air craft K&B engines good tachometer respectable thrust stand elbow grease Consequently efforts never created national records greatly improved aircraft performance Commercial props limit work expansion because lack sufficient mate rial must either start scratch locate usable prop increase per formance Both approaches will net worth results Several charts presented arti cle help understand workings propeller own test results shown Chart #1 indicates theoretical speeds ob tained using various common propeller pitches results have adjusted 80% propeller efficiency Chart rpm true engine rpm air Expect pick-up least 10% air rpm over ground rpm known unloading course evaluating propeller remember called good prop always ap pears unload less efficient Simple mathematics will render several interesting things Note speed increase pitch added keeping rpm constant Re ducing drag given size prop will cause rpm rise Adding pitch will crease mph maintaining original rpm rpm range adding 1 pitch will increase mph up 17 miles gain amount speed increasing rpm keeping same pitch must add 3700 rpm aware dif ficulty gain 500 rpm range logical experiment props engines chart also indicates expected per formance called torque-type en gines versus engines dependent upon pure horsepower figures presented stem new horsepower type engines Previ ously torque-type engines allowed better propeller efficiency giving equivalent air speeds lower rpm engines could turn 9 diameter X 9 pitch prop 20000 rpm equivalent 136 mph too bad engine power cannot increased torque rather rpm would applicable propeller Charts #2 #3 denote test results several proven good Formula-I propel lers labeled stock exactly However sizes chosen such 90 Model Aviation KIT 12 SPAN 34j~ SCALE 4 1 Ft TIGER MOTH 1295 ALL 72MHz 27MHz SYSTEMS NOW Ready delivery Featuring interference resistant transmitter receiver combination available trade Radiates highest signal level yes unit market today Proven helicopter capability Demonstratably faster powerful servos outstand ing resolution centering Stick assemblies smooth silk through out temperature range 10 1200F Transmitter control stick unit designed maximum comfort has feel instills confidence re duces fatigue Reliability has design goal Full 6 months warranty immediate factory servicing Study spec sheet free asking compare anything now being offered Youll see believe know VARIANT way go Visit us Toledo Show WESTPORT INTERNATIONAL INC 347 Boston Post Road Milford Conn 06460 will yield peak flight performance stock props Reworked props have tailored according ideas presented article Primarily diameter and/or pitch increase over acceptable stock props strived keeping rpm maximum engine horsepower range exten sive original prop work completed props checked excellent mula-I aircraft K&B 40 S III en gine flown proven competitive Chart information presented ob tained running session accu rate comparisons Results achieved inferior engine running under far ideal climatic conditions rpm shown about 2000 rpm below normal engine expectancy under better conditions Test equipment used K&B S III engine expanded meter photo cell tach ometer specially built thrust stand Engine tach purchased items nothing special thrust stand precision built fulfilling lifelong desire Although thrust stand readings needed comparative accurate Highest speed prop thrust reading 144 oz 9 lbs great deal thrust 40 cubic inch engine indicating outstanding work en gine manufacturers have extended us last few years interesting know stunt-type propeller yields considerably static thrust best speed props Chart #3 presented evaluation differences tested blade shapes No tempt has ever made experiment blade shape specific size propeller however chart comparisons dicate work area could beneficial According chart #2s test results expected determine super prop frankly super prop yet developed tests really show consequences alternating various de sign parameters example first three tests made same prop simply clipping tips time reduce diameter marked rpm crease indicates added horsepower small static thrust loss increased aircraft speed Remember test conducted starting too much prop same improvement can expected using right size prop beginning Note large static thrust increase gained wider blade width Such has proven beneficial actual racing symmetrical airfoil experiments drag reduction interesting changing lower drag airfoil diameter pitch increased horsepower loss Symmetrical airfoil props have used actual race performances yet flight tests indicate show great promise profitable future development conclusion purpose article hopefully incite intelligent speed propeller experimentation field Past racing performances too us have proven considerably propeller efficiency improvement sorely needed nation-wide break sound barrier someday must work ourselves fellow racers lets get up go Radio Technique/Myers continued page 11 glow-plug energizer have both switches 15 VDC side can light glow plug cant charge pack both switches 48 VDC side can charge pack cant light glow plug switch set direction pack Off cant anything except possibly draw current cell number 1 theres some way connect between 8 terminal Since already know least cells bad install piece wire place cell #1 theres no way draw current switches opposing positions can get fancy put whole thing plastic case 0-to-S Amp meter iron-vane types preferred durability low cost May1977 91