TRUE VYIIAMIC SCBLII1I Part two series true dy art designing plane flies like discuss factors make can determine whether workwithout trying out Theres lots useful .thewayE Dominic J vative Fairchild Republic A-b posed some unique dynamic scaling problems model spans 69 powered two RK-20B fan units Photo Bill Lowenstein IN PART ONE series discussed meaning dynamic scaling examined basis laws dynamic scale showed laws derived terms static scale factor will now compare laws constraints imposed fact model must flyable Clearly what modeler considers flyable may veiy different another modelers standards relates amount exper ience expertise flier also relates flying conditions will encounter espe cially flying field flier access smooth paved runway will usually able get away ship having lower thrust-to-weight ratio higher wing loading flier uses grass strip Similarly pilot used flying models high wing loadings can tolerate faster landing approach speeds such models have whereas used flying trainer aircraft would foolish consider such modeL order relate laws dynamic scaling flyabiity therefore will talldng about range flyable model constraints rather specific values leave up reader determine fits based upon experience flying field will using Flyability constraints based primarily practical considerations Certain aspects airplanes performance envelope must eval uated considerations mind relevant stall speed takeoff distance maximum speed maneuver spec trum Lets take look Stall speed stall speed airplane minimum speed plane can maintain straight level flight term derives terminology used describe what happens wing angle attack increases beyond critical angle called stall angle Lift increases angle attack increases up stall angle after lift decreases lift coefficient stall angle called maximum lift coeffi cient CLmax Setting lift equal weight CL x defines stall speed V5 2WW V5 — CLmaxS 29 CLS sea leveL V5 ft/sec W pounds S sq ft maximum lift coefficient un flapped wings does vary much value 1 Reynolds numbers associated models Some airfoils exhibit CLmax high 16 low 7 rare Wing planform affects stall independent size aircraft CLmax 1 get S lowest flight speed generally experi enced landing approach typically about 80% CLmax means approach speed about 12% higher V5 Model approach speed imposes first flyability constraint An experienced RC pilot can approach landing strip 40 45 mph ground speed since must plan worst case ie no headwind well consider ground speed equals airspeed 80% CLmay gives us wing loading 328 417 lbs/sq ft 53 68 oz/sq ft 74 Model Aviation Most pilots comfortable approach speed around 25 30 mph leads required wing loading 128 185 lbs/sq ft 20 30 oz/sq ft Flaps allow increased CLmax allows us have higher wing loadings Increases up 300% CLmax typical flaps exact percentage increase depends type flap amount wing area takes up safe approximation percentage crease 200% get CLmax ans model can have twice wing loading specified above still achieve cited approach speeds information summarized Figure 5 graph landing approach speed vs wing loading flapped unflapped airplanes parameters model scaled true dynamic scale fall within flyable wing loading range possible build workable RC model some factor must adjusted Its interesting note larger models ones smaller scale factors prototypes have low wing loadings attractive candidates reason Takeoff distance Takeoff distance certainly important consideration since RC flying sites have limited runway length model dynamically scaled takeoff run will reduced scale factor Lets say limit models takeoff run 400 feet typical RC runway length 1/6-scale models would have select aircraft prototype takeoff run no 2400 feet Note larger Scale models maximum practical full-scale take off run limited smaller distances consideration would automatically eliminate certain aircraft/scale factor combinations factor stands way particular scale project can relax constraint bit example thrust/weight ratio model greater equal full-scale prototype smooth run way available its safe consider takeoff run will acceptable Thrust/weight will dictate size engine required once models weight has estimated good rule thumb use determining available thrust standard glow engine T T thrust pounds d displacement cubic inches example standard 40 glow engine pro duces 15 x 40 unds available static thrust sea level engine Schnuerle ported can expect 15% increase thrust standard 40 Schnuerle will produce 7 lbs thrust tuned pipe will increase thrust another 10% bringing us up 77 lbs options can considered determining thrust/weight ratios Scale project allow some latitude scaling Maximum speed maximum speed airplane can calculated equation P DSV3max P maximum power delivered prop corresponding maximum speed means ratio power required model power required prototype airplane P SV dont worry about altitude drag coefficient derive dynamic scale rela tionship between v V static scale formula S leads following relation ship p/P power requirement generally what eliminates high-performance aircraft candidates flyable dynamic scale RC relationship between p P plotted inmodeL cases speed required just Fig 6 variety scale factorsContinued page 136 September 1981 75 U Winning Ideas FOURMOST RETRACTABLE TOW HOOK RELEASE Price SB90 Simplest reliable device available After line released hook retracts body unit leaving SMOOTH surface bottom aircraft No special attachments required N eight THER FOURMOST PRODUCTS 0491051 AIRFLO ENGINE MOUNT REDUCES DRAG VIBRATION FREE PRICE 250 40 AIRFLO ENGINE MOUNT IDEAL FOR GUICKY 500 PRICE 525 CL Scale/Byron Continued page 63 hope cover several contests year including Nats detailand plan take large amounts photographs future enjoyment Please submit photos Dick Byroa 2506 So 16 1st Circle Omaha NE 68130 Three Racers/Penhallow Continued page 66 weight will go upbut wont hurt unless gets over S oz fact 7 S oz will improve ability io handle windand will im prove pit stops making easier get model back pit man Remember arent Stunt models meant racing higher wing loading tolerable Misty Rivets two colors sprayed trim done decals India ink made decal sheets required colors spraying epoxy paint decal paper cutting out numbers letters needed pilot pictures painted decal sheet covered clear epoxy paint applied modeL black lines ink applied drafting pen very sure area going put ink clean will ball up fingerprint will cause ink skip La Jollita tried paint ing racing wing registration numbers Union 76 logo cut Dodgers baseball schedule isnt exactly same 1949 logo Whether paint trim use decals choice decals easier mess up just cut another try again After trimming done give model coat clear epoxy paint keeps decals ink place makes look better used dope finish trim use dope clear final coat other words keep finish materials compatible Flying no peculiar traits models funny-looking old Rivets behaves admirably Strangely seen two Control Line models Rivets before built neither flew welL problem seemed excessive line rake causes model yaw out badly odd looking line guide Rivets does have purpose does have great range adjustment Misty La Jollita run line directly bellcrank use lead-outs sure can pull back through line guide put through other holes want need change line rake first few flights put line through front lead-out guide hole other line through rearmost hole have feel model want less pull move lines Move front line back pull move rear line forward less pulL Making flights calm air will make easier feel changes Because models intended fit Scale Racing event have flown 008 diameter 42 ft solid steel lines flying just fun available 012 diameter 35 ft stranded lines should work welL lines should work well Keep nitro down propeller pitch 3 speed wont too fast handle after think want try racing four things can 1 Get out latest AMA rule book carefully read appropriate sections 2 Find local racer ask help 3 Start experimenting fuel props 4 Join CL-RPM organization Control Line Racing address Box 316 Yardley PA 19067 $8 calendar year worth SAFE FLYING IS NO ACCIDENT Scaling/Palumbo Continued page 75 too much unless model quite small designer faced problem finding engine will deliver required power still fit small modeL consider 120 mph flat-out speed about can expect RC pilot able handle can begin eliminate certain possible Scale subjects same way considering takeoff length can save lot trouble building unflyable airplane can course calculate power re quirement right off bat various scale factors refer Fig 6 determine can get power need range engines have available us example fullscale airplane has 150-hp engine would require 117-hp engine Quarter Scale model achieve scale speed quite possible engines available Quarter Scale ships however prototype powered 300-hp engine Quarter Scale model now requires 234 hp pushing state art bit word caution Usually manufacturers listings horsepower engines dont take account de-rating effect propellers good safe value use 70% manufac turers listed horsepower rating can estimate horsepower available standard glow engine equation p 16d p horsepower d cubic inches displacement Schnuerle-ported engines add 10% toned pipe used product review product review product review Ah Gee Bees hasnt anything like em before since Model Z first racer try out Granville Brothers theory teardrop best shape racing airplane Five wins Cleveland Air Races lent some weight idea Gee Bee R-1 Jimmy Doolittle made famous 1932 followed kit latest line 1/32 scale Golden Age plastic kits Williams Bros kit features two differ ent cowlings two types wheels de tailed cockpit interior nylon monofila ment rigging Other ships series include Gee Bee R-1 Wedell Williams Caudron C460 suggested experienced model builders can appreciate degree accuracy quality Williams kit product review product review product review 136 Model Aviation Fuel Fitting Sets Fuel Shut Off Fuel Manifold Gapless Hinges Gapless Hinge Slotter Strut Fairings Codcpit Coaming FUR~ST Send SASE Complete Information 4040 24th Ave Forest Grove OR 97116 RODUCTS Phone 503 357-2732 uee Uee Z Plastic Model Kit $7 Williams Brothers 181 Pawnee St Marcos CA 92069 add another 10% Keep mind thrust power outputs glow engines parallel typical reciprocating fullscale aircraft engines because glow engines develop power high rpm whereas larger gas engines generate horsepower through lower rpm higher torque Thrust propor tional torque reason use speed reducers larger gas engines some Giant Scale modelseven though normal power output some large glow engines would sufficient important thing remember thrust relates maneuverability whereas power relates max imum flying speed Maneuverability final consideration does relate absolute flyability well model will duplicate prototypes ma neuver spectrum Two important character istics determine thrust/weight ratio power/weight ratio Most models can built much lighter weight required true dynamic scale still made fly like prototype Precision Scale Sport Scale enthusiasts have doing years As matter fact model lighter dynamic scale weight will land slower require less thrust equivalent thrust/weight course can now duplicate authentic landing speed bringing model little hotter have Similarly models thrust/weight greater prototype will capable shorter takeoff rollhut scale flight throttle back bit Indeed few maneuvers cannot duplicated true dynamic scale fashion airplane lighter has thrust dynamic scale values maneuvers pilot has very little inter mediate control over like spins vertical dives snap rolls Generally can conclude lightest possible model should built As long model weight less dynamic scale weight thrust/weight least large prototype model can made fly scale manner over major portion its maneuver spectrum true great number airplanes always possible generally has strike compromise between scale factor weight thrust power modeL Doing involves selecting value N scale factor estimating weight model based its size selecting engine produces thrust power required allows come up good idea what model will like given scale factor Figure range scale factors over range what practical select optimum Part III series will illustrate Space Shuttle/Hux Con finued page 73 shaping carved portions Shuttle paint markings use photos Time magazine Columbia has few changes marking over other drawings earlier Shuttles black top wing leading edge black top rudder Most display models show green-grey leading edge actual photos appear greytake pick plastic kits can provide detail would practical use flying model airfoil compromise between what would appear scale still give good performance Now have covered modifications lets build Shuttle Begin fuselage center section Cut out bulkheads cut out centers until cross-grain doublers have attached bulkhead too fragile centers removed Mark door edge cut lines both sides bulkhead cut door lines halfway through bulkhead thick ness final cut through made after center sheeted Glue bulkheads floor piece partial cuts facing inside Note angle bulkheads floor Glue pine longeron sets trying glue adjacent longerons other gap between sets hinge line doors Light pine longerons recommended stead balsa topreventwarpingofthe doors Wet side sheeting hot water glue dry side frame starting top door seam dry cut sheeting gaps between longerons complete cuts started bulkheads remove doors Tape doors back place Attach 1/16 cross grain doubler forward bulkhead careful apply glue door area Trim edges mini-saw cutout center bulkhead Assemble blocks soft balsa cut nose section Mark top side profile blocks cut band jigsaw keep blocks square table second cut September 1981 137 k/eueIF NEED6o BALSA.3t BALSA SHEETSBALSA BLOCKS 48 long24 long 4/ie4912 62 5213 86 6214 126 4Yie7422 86 4 9023 126 410833 240 6 /16BALSA STICKS 6/32 78 6 6 3/joSold packs 5 6162/16 70 70 /8~ 75 PLYWOOD 3M 95 6"48/ 110 /32 y1253M lie y136 square 70 /32 y175/16 square 75 5-ply185 square 85 /I6 y240M square 140 5-ply280 square 190 Write complete product listing Manufacturers dealers inquiries invited Special szes available Add $350 postage handling No minimum requirements NIIG NODELS INC PO BOX 396 Y MARYLAND 301 326-2554
Edition: Model Aviation - 1981/09
Page Numbers: 74, 75, 136, 137
TRUE VYIIAMIC SCBLII1I Part two series true dy art designing plane flies like discuss factors make can determine whether workwithout trying out Theres lots useful .thewayE Dominic J vative Fairchild Republic A-b posed some unique dynamic scaling problems model spans 69 powered two RK-20B fan units Photo Bill Lowenstein IN PART ONE series discussed meaning dynamic scaling examined basis laws dynamic scale showed laws derived terms static scale factor will now compare laws constraints imposed fact model must flyable Clearly what modeler considers flyable may veiy different another modelers standards relates amount exper ience expertise flier also relates flying conditions will encounter espe cially flying field flier access smooth paved runway will usually able get away ship having lower thrust-to-weight ratio higher wing loading flier uses grass strip Similarly pilot used flying models high wing loadings can tolerate faster landing approach speeds such models have whereas used flying trainer aircraft would foolish consider such modeL order relate laws dynamic scaling flyabiity therefore will talldng about range flyable model constraints rather specific values leave up reader determine fits based upon experience flying field will using Flyability constraints based primarily practical considerations Certain aspects airplanes performance envelope must eval uated considerations mind relevant stall speed takeoff distance maximum speed maneuver spec trum Lets take look Stall speed stall speed airplane minimum speed plane can maintain straight level flight term derives terminology used describe what happens wing angle attack increases beyond critical angle called stall angle Lift increases angle attack increases up stall angle after lift decreases lift coefficient stall angle called maximum lift coeffi cient CLmax Setting lift equal weight CL x defines stall speed V5 2WW V5 — CLmaxS 29 CLS sea leveL V5 ft/sec W pounds S sq ft maximum lift coefficient un flapped wings does vary much value 1 Reynolds numbers associated models Some airfoils exhibit CLmax high 16 low 7 rare Wing planform affects stall independent size aircraft CLmax 1 get S lowest flight speed generally experi enced landing approach typically about 80% CLmax means approach speed about 12% higher V5 Model approach speed imposes first flyability constraint An experienced RC pilot can approach landing strip 40 45 mph ground speed since must plan worst case ie no headwind well consider ground speed equals airspeed 80% CLmay gives us wing loading 328 417 lbs/sq ft 53 68 oz/sq ft 74 Model Aviation Most pilots comfortable approach speed around 25 30 mph leads required wing loading 128 185 lbs/sq ft 20 30 oz/sq ft Flaps allow increased CLmax allows us have higher wing loadings Increases up 300% CLmax typical flaps exact percentage increase depends type flap amount wing area takes up safe approximation percentage crease 200% get CLmax ans model can have twice wing loading specified above still achieve cited approach speeds information summarized Figure 5 graph landing approach speed vs wing loading flapped unflapped airplanes parameters model scaled true dynamic scale fall within flyable wing loading range possible build workable RC model some factor must adjusted Its interesting note larger models ones smaller scale factors prototypes have low wing loadings attractive candidates reason Takeoff distance Takeoff distance certainly important consideration since RC flying sites have limited runway length model dynamically scaled takeoff run will reduced scale factor Lets say limit models takeoff run 400 feet typical RC runway length 1/6-scale models would have select aircraft prototype takeoff run no 2400 feet Note larger Scale models maximum practical full-scale take off run limited smaller distances consideration would automatically eliminate certain aircraft/scale factor combinations factor stands way particular scale project can relax constraint bit example thrust/weight ratio model greater equal full-scale prototype smooth run way available its safe consider takeoff run will acceptable Thrust/weight will dictate size engine required once models weight has estimated good rule thumb use determining available thrust standard glow engine T T thrust pounds d displacement cubic inches example standard 40 glow engine pro duces 15 x 40 unds available static thrust sea level engine Schnuerle ported can expect 15% increase thrust standard 40 Schnuerle will produce 7 lbs thrust tuned pipe will increase thrust another 10% bringing us up 77 lbs options can considered determining thrust/weight ratios Scale project allow some latitude scaling Maximum speed maximum speed airplane can calculated equation P DSV3max P maximum power delivered prop corresponding maximum speed means ratio power required model power required prototype airplane P SV dont worry about altitude drag coefficient derive dynamic scale rela tionship between v V static scale formula S leads following relation ship p/P power requirement generally what eliminates high-performance aircraft candidates flyable dynamic scale RC relationship between p P plotted inmodeL cases speed required just Fig 6 variety scale factorsContinued page 136 September 1981 75 U Winning Ideas FOURMOST RETRACTABLE TOW HOOK RELEASE Price SB90 Simplest reliable device available After line released hook retracts body unit leaving SMOOTH surface bottom aircraft No special attachments required N eight THER FOURMOST PRODUCTS 0491051 AIRFLO ENGINE MOUNT REDUCES DRAG VIBRATION FREE PRICE 250 40 AIRFLO ENGINE MOUNT IDEAL FOR GUICKY 500 PRICE 525 CL Scale/Byron Continued page 63 hope cover several contests year including Nats detailand plan take large amounts photographs future enjoyment Please submit photos Dick Byroa 2506 So 16 1st Circle Omaha NE 68130 Three Racers/Penhallow Continued page 66 weight will go upbut wont hurt unless gets over S oz fact 7 S oz will improve ability io handle windand will im prove pit stops making easier get model back pit man Remember arent Stunt models meant racing higher wing loading tolerable Misty Rivets two colors sprayed trim done decals India ink made decal sheets required colors spraying epoxy paint decal paper cutting out numbers letters needed pilot pictures painted decal sheet covered clear epoxy paint applied modeL black lines ink applied drafting pen very sure area going put ink clean will ball up fingerprint will cause ink skip La Jollita tried paint ing racing wing registration numbers Union 76 logo cut Dodgers baseball schedule isnt exactly same 1949 logo Whether paint trim use decals choice decals easier mess up just cut another try again After trimming done give model coat clear epoxy paint keeps decals ink place makes look better used dope finish trim use dope clear final coat other words keep finish materials compatible Flying no peculiar traits models funny-looking old Rivets behaves admirably Strangely seen two Control Line models Rivets before built neither flew welL problem seemed excessive line rake causes model yaw out badly odd looking line guide Rivets does have purpose does have great range adjustment Misty La Jollita run line directly bellcrank use lead-outs sure can pull back through line guide put through other holes want need change line rake first few flights put line through front lead-out guide hole other line through rearmost hole have feel model want less pull move lines Move front line back pull move rear line forward less pulL Making flights calm air will make easier feel changes Because models intended fit Scale Racing event have flown 008 diameter 42 ft solid steel lines flying just fun available 012 diameter 35 ft stranded lines should work welL lines should work well Keep nitro down propeller pitch 3 speed wont too fast handle after think want try racing four things can 1 Get out latest AMA rule book carefully read appropriate sections 2 Find local racer ask help 3 Start experimenting fuel props 4 Join CL-RPM organization Control Line Racing address Box 316 Yardley PA 19067 $8 calendar year worth SAFE FLYING IS NO ACCIDENT Scaling/Palumbo Continued page 75 too much unless model quite small designer faced problem finding engine will deliver required power still fit small modeL consider 120 mph flat-out speed about can expect RC pilot able handle can begin eliminate certain possible Scale subjects same way considering takeoff length can save lot trouble building unflyable airplane can course calculate power re quirement right off bat various scale factors refer Fig 6 determine can get power need range engines have available us example fullscale airplane has 150-hp engine would require 117-hp engine Quarter Scale model achieve scale speed quite possible engines available Quarter Scale ships however prototype powered 300-hp engine Quarter Scale model now requires 234 hp pushing state art bit word caution Usually manufacturers listings horsepower engines dont take account de-rating effect propellers good safe value use 70% manufac turers listed horsepower rating can estimate horsepower available standard glow engine equation p 16d p horsepower d cubic inches displacement Schnuerle-ported engines add 10% toned pipe used product review product review product review Ah Gee Bees hasnt anything like em before since Model Z first racer try out Granville Brothers theory teardrop best shape racing airplane Five wins Cleveland Air Races lent some weight idea Gee Bee R-1 Jimmy Doolittle made famous 1932 followed kit latest line 1/32 scale Golden Age plastic kits Williams Bros kit features two differ ent cowlings two types wheels de tailed cockpit interior nylon monofila ment rigging Other ships series include Gee Bee R-1 Wedell Williams Caudron C460 suggested experienced model builders can appreciate degree accuracy quality Williams kit product review product review product review 136 Model Aviation Fuel Fitting Sets Fuel Shut Off Fuel Manifold Gapless Hinges Gapless Hinge Slotter Strut Fairings Codcpit Coaming FUR~ST Send SASE Complete Information 4040 24th Ave Forest Grove OR 97116 RODUCTS Phone 503 357-2732 uee Uee Z Plastic Model Kit $7 Williams Brothers 181 Pawnee St Marcos CA 92069 add another 10% Keep mind thrust power outputs glow engines parallel typical reciprocating fullscale aircraft engines because glow engines develop power high rpm whereas larger gas engines generate horsepower through lower rpm higher torque Thrust propor tional torque reason use speed reducers larger gas engines some Giant Scale modelseven though normal power output some large glow engines would sufficient important thing remember thrust relates maneuverability whereas power relates max imum flying speed Maneuverability final consideration does relate absolute flyability well model will duplicate prototypes ma neuver spectrum Two important character istics determine thrust/weight ratio power/weight ratio Most models can built much lighter weight required true dynamic scale still made fly like prototype Precision Scale Sport Scale enthusiasts have doing years As matter fact model lighter dynamic scale weight will land slower require less thrust equivalent thrust/weight course can now duplicate authentic landing speed bringing model little hotter have Similarly models thrust/weight greater prototype will capable shorter takeoff rollhut scale flight throttle back bit Indeed few maneuvers cannot duplicated true dynamic scale fashion airplane lighter has thrust dynamic scale values maneuvers pilot has very little inter mediate control over like spins vertical dives snap rolls Generally can conclude lightest possible model should built As long model weight less dynamic scale weight thrust/weight least large prototype model can made fly scale manner over major portion its maneuver spectrum true great number airplanes always possible generally has strike compromise between scale factor weight thrust power modeL Doing involves selecting value N scale factor estimating weight model based its size selecting engine produces thrust power required allows come up good idea what model will like given scale factor Figure range scale factors over range what practical select optimum Part III series will illustrate Space Shuttle/Hux Con finued page 73 shaping carved portions Shuttle paint markings use photos Time magazine Columbia has few changes marking over other drawings earlier Shuttles black top wing leading edge black top rudder Most display models show green-grey leading edge actual photos appear greytake pick plastic kits can provide detail would practical use flying model airfoil compromise between what would appear scale still give good performance Now have covered modifications lets build Shuttle Begin fuselage center section Cut out bulkheads cut out centers until cross-grain doublers have attached bulkhead too fragile centers removed Mark door edge cut lines both sides bulkhead cut door lines halfway through bulkhead thick ness final cut through made after center sheeted Glue bulkheads floor piece partial cuts facing inside Note angle bulkheads floor Glue pine longeron sets trying glue adjacent longerons other gap between sets hinge line doors Light pine longerons recommended stead balsa topreventwarpingofthe doors Wet side sheeting hot water glue dry side frame starting top door seam dry cut sheeting gaps between longerons complete cuts started bulkheads remove doors Tape doors back place Attach 1/16 cross grain doubler forward bulkhead careful apply glue door area Trim edges mini-saw cutout center bulkhead Assemble blocks soft balsa cut nose section Mark top side profile blocks cut band jigsaw keep blocks square table second cut September 1981 137 k/eueIF NEED6o BALSA.3t BALSA SHEETSBALSA BLOCKS 48 long24 long 4/ie4912 62 5213 86 6214 126 4Yie7422 86 4 9023 126 410833 240 6 /16BALSA STICKS 6/32 78 6 6 3/joSold packs 5 6162/16 70 70 /8~ 75 PLYWOOD 3M 95 6"48/ 110 /32 y1253M lie y136 square 70 /32 y175/16 square 75 5-ply185 square 85 /I6 y240M square 140 5-ply280 square 190 Write complete product listing Manufacturers dealers inquiries invited Special szes available Add $350 postage handling No minimum requirements NIIG NODELS INC PO BOX 396 Y MARYLAND 301 326-2554
Edition: Model Aviation - 1981/09
Page Numbers: 74, 75, 136, 137
TRUE VYIIAMIC SCBLII1I Part two series true dy art designing plane flies like discuss factors make can determine whether workwithout trying out Theres lots useful .thewayE Dominic J vative Fairchild Republic A-b posed some unique dynamic scaling problems model spans 69 powered two RK-20B fan units Photo Bill Lowenstein IN PART ONE series discussed meaning dynamic scaling examined basis laws dynamic scale showed laws derived terms static scale factor will now compare laws constraints imposed fact model must flyable Clearly what modeler considers flyable may veiy different another modelers standards relates amount exper ience expertise flier also relates flying conditions will encounter espe cially flying field flier access smooth paved runway will usually able get away ship having lower thrust-to-weight ratio higher wing loading flier uses grass strip Similarly pilot used flying models high wing loadings can tolerate faster landing approach speeds such models have whereas used flying trainer aircraft would foolish consider such modeL order relate laws dynamic scaling flyabiity therefore will talldng about range flyable model constraints rather specific values leave up reader determine fits based upon experience flying field will using Flyability constraints based primarily practical considerations Certain aspects airplanes performance envelope must eval uated considerations mind relevant stall speed takeoff distance maximum speed maneuver spec trum Lets take look Stall speed stall speed airplane minimum speed plane can maintain straight level flight term derives terminology used describe what happens wing angle attack increases beyond critical angle called stall angle Lift increases angle attack increases up stall angle after lift decreases lift coefficient stall angle called maximum lift coeffi cient CLmax Setting lift equal weight CL x defines stall speed V5 2WW V5 — CLmaxS 29 CLS sea leveL V5 ft/sec W pounds S sq ft maximum lift coefficient un flapped wings does vary much value 1 Reynolds numbers associated models Some airfoils exhibit CLmax high 16 low 7 rare Wing planform affects stall independent size aircraft CLmax 1 get S lowest flight speed generally experi enced landing approach typically about 80% CLmax means approach speed about 12% higher V5 Model approach speed imposes first flyability constraint An experienced RC pilot can approach landing strip 40 45 mph ground speed since must plan worst case ie no headwind well consider ground speed equals airspeed 80% CLmay gives us wing loading 328 417 lbs/sq ft 53 68 oz/sq ft 74 Model Aviation Most pilots comfortable approach speed around 25 30 mph leads required wing loading 128 185 lbs/sq ft 20 30 oz/sq ft Flaps allow increased CLmax allows us have higher wing loadings Increases up 300% CLmax typical flaps exact percentage increase depends type flap amount wing area takes up safe approximation percentage crease 200% get CLmax ans model can have twice wing loading specified above still achieve cited approach speeds information summarized Figure 5 graph landing approach speed vs wing loading flapped unflapped airplanes parameters model scaled true dynamic scale fall within flyable wing loading range possible build workable RC model some factor must adjusted Its interesting note larger models ones smaller scale factors prototypes have low wing loadings attractive candidates reason Takeoff distance Takeoff distance certainly important consideration since RC flying sites have limited runway length model dynamically scaled takeoff run will reduced scale factor Lets say limit models takeoff run 400 feet typical RC runway length 1/6-scale models would have select aircraft prototype takeoff run no 2400 feet Note larger Scale models maximum practical full-scale take off run limited smaller distances consideration would automatically eliminate certain aircraft/scale factor combinations factor stands way particular scale project can relax constraint bit example thrust/weight ratio model greater equal full-scale prototype smooth run way available its safe consider takeoff run will acceptable Thrust/weight will dictate size engine required once models weight has estimated good rule thumb use determining available thrust standard glow engine T T thrust pounds d displacement cubic inches example standard 40 glow engine pro duces 15 x 40 unds available static thrust sea level engine Schnuerle ported can expect 15% increase thrust standard 40 Schnuerle will produce 7 lbs thrust tuned pipe will increase thrust another 10% bringing us up 77 lbs options can considered determining thrust/weight ratios Scale project allow some latitude scaling Maximum speed maximum speed airplane can calculated equation P DSV3max P maximum power delivered prop corresponding maximum speed means ratio power required model power required prototype airplane P SV dont worry about altitude drag coefficient derive dynamic scale rela tionship between v V static scale formula S leads following relation ship p/P power requirement generally what eliminates high-performance aircraft candidates flyable dynamic scale RC relationship between p P plotted inmodeL cases speed required just Fig 6 variety scale factorsContinued page 136 September 1981 75 U Winning Ideas FOURMOST RETRACTABLE TOW HOOK RELEASE Price SB90 Simplest reliable device available After line released hook retracts body unit leaving SMOOTH surface bottom aircraft No special attachments required N eight THER FOURMOST PRODUCTS 0491051 AIRFLO ENGINE MOUNT REDUCES DRAG VIBRATION FREE PRICE 250 40 AIRFLO ENGINE MOUNT IDEAL FOR GUICKY 500 PRICE 525 CL Scale/Byron Continued page 63 hope cover several contests year including Nats detailand plan take large amounts photographs future enjoyment Please submit photos Dick Byroa 2506 So 16 1st Circle Omaha NE 68130 Three Racers/Penhallow Continued page 66 weight will go upbut wont hurt unless gets over S oz fact 7 S oz will improve ability io handle windand will im prove pit stops making easier get model back pit man Remember arent Stunt models meant racing higher wing loading tolerable Misty Rivets two colors sprayed trim done decals India ink made decal sheets required colors spraying epoxy paint decal paper cutting out numbers letters needed pilot pictures painted decal sheet covered clear epoxy paint applied modeL black lines ink applied drafting pen very sure area going put ink clean will ball up fingerprint will cause ink skip La Jollita tried paint ing racing wing registration numbers Union 76 logo cut Dodgers baseball schedule isnt exactly same 1949 logo Whether paint trim use decals choice decals easier mess up just cut another try again After trimming done give model coat clear epoxy paint keeps decals ink place makes look better used dope finish trim use dope clear final coat other words keep finish materials compatible Flying no peculiar traits models funny-looking old Rivets behaves admirably Strangely seen two Control Line models Rivets before built neither flew welL problem seemed excessive line rake causes model yaw out badly odd looking line guide Rivets does have purpose does have great range adjustment Misty La Jollita run line directly bellcrank use lead-outs sure can pull back through line guide put through other holes want need change line rake first few flights put line through front lead-out guide hole other line through rearmost hole have feel model want less pull move lines Move front line back pull move rear line forward less pulL Making flights calm air will make easier feel changes Because models intended fit Scale Racing event have flown 008 diameter 42 ft solid steel lines flying just fun available 012 diameter 35 ft stranded lines should work welL lines should work well Keep nitro down propeller pitch 3 speed wont too fast handle after think want try racing four things can 1 Get out latest AMA rule book carefully read appropriate sections 2 Find local racer ask help 3 Start experimenting fuel props 4 Join CL-RPM organization Control Line Racing address Box 316 Yardley PA 19067 $8 calendar year worth SAFE FLYING IS NO ACCIDENT Scaling/Palumbo Continued page 75 too much unless model quite small designer faced problem finding engine will deliver required power still fit small modeL consider 120 mph flat-out speed about can expect RC pilot able handle can begin eliminate certain possible Scale subjects same way considering takeoff length can save lot trouble building unflyable airplane can course calculate power re quirement right off bat various scale factors refer Fig 6 determine can get power need range engines have available us example fullscale airplane has 150-hp engine would require 117-hp engine Quarter Scale model achieve scale speed quite possible engines available Quarter Scale ships however prototype powered 300-hp engine Quarter Scale model now requires 234 hp pushing state art bit word caution Usually manufacturers listings horsepower engines dont take account de-rating effect propellers good safe value use 70% manufac turers listed horsepower rating can estimate horsepower available standard glow engine equation p 16d p horsepower d cubic inches displacement Schnuerle-ported engines add 10% toned pipe used product review product review product review Ah Gee Bees hasnt anything like em before since Model Z first racer try out Granville Brothers theory teardrop best shape racing airplane Five wins Cleveland Air Races lent some weight idea Gee Bee R-1 Jimmy Doolittle made famous 1932 followed kit latest line 1/32 scale Golden Age plastic kits Williams Bros kit features two differ ent cowlings two types wheels de tailed cockpit interior nylon monofila ment rigging Other ships series include Gee Bee R-1 Wedell Williams Caudron C460 suggested experienced model builders can appreciate degree accuracy quality Williams kit product review product review product review 136 Model Aviation Fuel Fitting Sets Fuel Shut Off Fuel Manifold Gapless Hinges Gapless Hinge Slotter Strut Fairings Codcpit Coaming FUR~ST Send SASE Complete Information 4040 24th Ave Forest Grove OR 97116 RODUCTS Phone 503 357-2732 uee Uee Z Plastic Model Kit $7 Williams Brothers 181 Pawnee St Marcos CA 92069 add another 10% Keep mind thrust power outputs glow engines parallel typical reciprocating fullscale aircraft engines because glow engines develop power high rpm whereas larger gas engines generate horsepower through lower rpm higher torque Thrust propor tional torque reason use speed reducers larger gas engines some Giant Scale modelseven though normal power output some large glow engines would sufficient important thing remember thrust relates maneuverability whereas power relates max imum flying speed Maneuverability final consideration does relate absolute flyability well model will duplicate prototypes ma neuver spectrum Two important character istics determine thrust/weight ratio power/weight ratio Most models can built much lighter weight required true dynamic scale still made fly like prototype Precision Scale Sport Scale enthusiasts have doing years As matter fact model lighter dynamic scale weight will land slower require less thrust equivalent thrust/weight course can now duplicate authentic landing speed bringing model little hotter have Similarly models thrust/weight greater prototype will capable shorter takeoff rollhut scale flight throttle back bit Indeed few maneuvers cannot duplicated true dynamic scale fashion airplane lighter has thrust dynamic scale values maneuvers pilot has very little inter mediate control over like spins vertical dives snap rolls Generally can conclude lightest possible model should built As long model weight less dynamic scale weight thrust/weight least large prototype model can made fly scale manner over major portion its maneuver spectrum true great number airplanes always possible generally has strike compromise between scale factor weight thrust power modeL Doing involves selecting value N scale factor estimating weight model based its size selecting engine produces thrust power required allows come up good idea what model will like given scale factor Figure range scale factors over range what practical select optimum Part III series will illustrate Space Shuttle/Hux Con finued page 73 shaping carved portions Shuttle paint markings use photos Time magazine Columbia has few changes marking over other drawings earlier Shuttles black top wing leading edge black top rudder Most display models show green-grey leading edge actual photos appear greytake pick plastic kits can provide detail would practical use flying model airfoil compromise between what would appear scale still give good performance Now have covered modifications lets build Shuttle Begin fuselage center section Cut out bulkheads cut out centers until cross-grain doublers have attached bulkhead too fragile centers removed Mark door edge cut lines both sides bulkhead cut door lines halfway through bulkhead thick ness final cut through made after center sheeted Glue bulkheads floor piece partial cuts facing inside Note angle bulkheads floor Glue pine longeron sets trying glue adjacent longerons other gap between sets hinge line doors Light pine longerons recommended stead balsa topreventwarpingofthe doors Wet side sheeting hot water glue dry side frame starting top door seam dry cut sheeting gaps between longerons complete cuts started bulkheads remove doors Tape doors back place Attach 1/16 cross grain doubler forward bulkhead careful apply glue door area Trim edges mini-saw cutout center bulkhead Assemble blocks soft balsa cut nose section Mark top side profile blocks cut band jigsaw keep blocks square table second cut September 1981 137 k/eueIF NEED6o BALSA.3t BALSA SHEETSBALSA BLOCKS 48 long24 long 4/ie4912 62 5213 86 6214 126 4Yie7422 86 4 9023 126 410833 240 6 /16BALSA STICKS 6/32 78 6 6 3/joSold packs 5 6162/16 70 70 /8~ 75 PLYWOOD 3M 95 6"48/ 110 /32 y1253M lie y136 square 70 /32 y175/16 square 75 5-ply185 square 85 /I6 y240M square 140 5-ply280 square 190 Write complete product listing Manufacturers dealers inquiries invited Special szes available Add $350 postage handling No minimum requirements NIIG NODELS INC PO BOX 396 Y MARYLAND 301 326-2554
Edition: Model Aviation - 1981/09
Page Numbers: 74, 75, 136, 137
TRUE VYIIAMIC SCBLII1I Part two series true dy art designing plane flies like discuss factors make can determine whether workwithout trying out Theres lots useful .thewayE Dominic J vative Fairchild Republic A-b posed some unique dynamic scaling problems model spans 69 powered two RK-20B fan units Photo Bill Lowenstein IN PART ONE series discussed meaning dynamic scaling examined basis laws dynamic scale showed laws derived terms static scale factor will now compare laws constraints imposed fact model must flyable Clearly what modeler considers flyable may veiy different another modelers standards relates amount exper ience expertise flier also relates flying conditions will encounter espe cially flying field flier access smooth paved runway will usually able get away ship having lower thrust-to-weight ratio higher wing loading flier uses grass strip Similarly pilot used flying models high wing loadings can tolerate faster landing approach speeds such models have whereas used flying trainer aircraft would foolish consider such modeL order relate laws dynamic scaling flyabiity therefore will talldng about range flyable model constraints rather specific values leave up reader determine fits based upon experience flying field will using Flyability constraints based primarily practical considerations Certain aspects airplanes performance envelope must eval uated considerations mind relevant stall speed takeoff distance maximum speed maneuver spec trum Lets take look Stall speed stall speed airplane minimum speed plane can maintain straight level flight term derives terminology used describe what happens wing angle attack increases beyond critical angle called stall angle Lift increases angle attack increases up stall angle after lift decreases lift coefficient stall angle called maximum lift coeffi cient CLmax Setting lift equal weight CL x defines stall speed V5 2WW V5 — CLmaxS 29 CLS sea leveL V5 ft/sec W pounds S sq ft maximum lift coefficient un flapped wings does vary much value 1 Reynolds numbers associated models Some airfoils exhibit CLmax high 16 low 7 rare Wing planform affects stall independent size aircraft CLmax 1 get S lowest flight speed generally experi enced landing approach typically about 80% CLmax means approach speed about 12% higher V5 Model approach speed imposes first flyability constraint An experienced RC pilot can approach landing strip 40 45 mph ground speed since must plan worst case ie no headwind well consider ground speed equals airspeed 80% CLmay gives us wing loading 328 417 lbs/sq ft 53 68 oz/sq ft 74 Model Aviation Most pilots comfortable approach speed around 25 30 mph leads required wing loading 128 185 lbs/sq ft 20 30 oz/sq ft Flaps allow increased CLmax allows us have higher wing loadings Increases up 300% CLmax typical flaps exact percentage increase depends type flap amount wing area takes up safe approximation percentage crease 200% get CLmax ans model can have twice wing loading specified above still achieve cited approach speeds information summarized Figure 5 graph landing approach speed vs wing loading flapped unflapped airplanes parameters model scaled true dynamic scale fall within flyable wing loading range possible build workable RC model some factor must adjusted Its interesting note larger models ones smaller scale factors prototypes have low wing loadings attractive candidates reason Takeoff distance Takeoff distance certainly important consideration since RC flying sites have limited runway length model dynamically scaled takeoff run will reduced scale factor Lets say limit models takeoff run 400 feet typical RC runway length 1/6-scale models would have select aircraft prototype takeoff run no 2400 feet Note larger Scale models maximum practical full-scale take off run limited smaller distances consideration would automatically eliminate certain aircraft/scale factor combinations factor stands way particular scale project can relax constraint bit example thrust/weight ratio model greater equal full-scale prototype smooth run way available its safe consider takeoff run will acceptable Thrust/weight will dictate size engine required once models weight has estimated good rule thumb use determining available thrust standard glow engine T T thrust pounds d displacement cubic inches example standard 40 glow engine pro duces 15 x 40 unds available static thrust sea level engine Schnuerle ported can expect 15% increase thrust standard 40 Schnuerle will produce 7 lbs thrust tuned pipe will increase thrust another 10% bringing us up 77 lbs options can considered determining thrust/weight ratios Scale project allow some latitude scaling Maximum speed maximum speed airplane can calculated equation P DSV3max P maximum power delivered prop corresponding maximum speed means ratio power required model power required prototype airplane P SV dont worry about altitude drag coefficient derive dynamic scale rela tionship between v V static scale formula S leads following relation ship p/P power requirement generally what eliminates high-performance aircraft candidates flyable dynamic scale RC relationship between p P plotted inmodeL cases speed required just Fig 6 variety scale factorsContinued page 136 September 1981 75 U Winning Ideas FOURMOST RETRACTABLE TOW HOOK RELEASE Price SB90 Simplest reliable device available After line released hook retracts body unit leaving SMOOTH surface bottom aircraft No special attachments required N eight THER FOURMOST PRODUCTS 0491051 AIRFLO ENGINE MOUNT REDUCES DRAG VIBRATION FREE PRICE 250 40 AIRFLO ENGINE MOUNT IDEAL FOR GUICKY 500 PRICE 525 CL Scale/Byron Continued page 63 hope cover several contests year including Nats detailand plan take large amounts photographs future enjoyment Please submit photos Dick Byroa 2506 So 16 1st Circle Omaha NE 68130 Three Racers/Penhallow Continued page 66 weight will go upbut wont hurt unless gets over S oz fact 7 S oz will improve ability io handle windand will im prove pit stops making easier get model back pit man Remember arent Stunt models meant racing higher wing loading tolerable Misty Rivets two colors sprayed trim done decals India ink made decal sheets required colors spraying epoxy paint decal paper cutting out numbers letters needed pilot pictures painted decal sheet covered clear epoxy paint applied modeL black lines ink applied drafting pen very sure area going put ink clean will ball up fingerprint will cause ink skip La Jollita tried paint ing racing wing registration numbers Union 76 logo cut Dodgers baseball schedule isnt exactly same 1949 logo Whether paint trim use decals choice decals easier mess up just cut another try again After trimming done give model coat clear epoxy paint keeps decals ink place makes look better used dope finish trim use dope clear final coat other words keep finish materials compatible Flying no peculiar traits models funny-looking old Rivets behaves admirably Strangely seen two Control Line models Rivets before built neither flew welL problem seemed excessive line rake causes model yaw out badly odd looking line guide Rivets does have purpose does have great range adjustment Misty La Jollita run line directly bellcrank use lead-outs sure can pull back through line guide put through other holes want need change line rake first few flights put line through front lead-out guide hole other line through rearmost hole have feel model want less pull move lines Move front line back pull move rear line forward less pulL Making flights calm air will make easier feel changes Because models intended fit Scale Racing event have flown 008 diameter 42 ft solid steel lines flying just fun available 012 diameter 35 ft stranded lines should work welL lines should work well Keep nitro down propeller pitch 3 speed wont too fast handle after think want try racing four things can 1 Get out latest AMA rule book carefully read appropriate sections 2 Find local racer ask help 3 Start experimenting fuel props 4 Join CL-RPM organization Control Line Racing address Box 316 Yardley PA 19067 $8 calendar year worth SAFE FLYING IS NO ACCIDENT Scaling/Palumbo Continued page 75 too much unless model quite small designer faced problem finding engine will deliver required power still fit small modeL consider 120 mph flat-out speed about can expect RC pilot able handle can begin eliminate certain possible Scale subjects same way considering takeoff length can save lot trouble building unflyable airplane can course calculate power re quirement right off bat various scale factors refer Fig 6 determine can get power need range engines have available us example fullscale airplane has 150-hp engine would require 117-hp engine Quarter Scale model achieve scale speed quite possible engines available Quarter Scale ships however prototype powered 300-hp engine Quarter Scale model now requires 234 hp pushing state art bit word caution Usually manufacturers listings horsepower engines dont take account de-rating effect propellers good safe value use 70% manufac turers listed horsepower rating can estimate horsepower available standard glow engine equation p 16d p horsepower d cubic inches displacement Schnuerle-ported engines add 10% toned pipe used product review product review product review Ah Gee Bees hasnt anything like em before since Model Z first racer try out Granville Brothers theory teardrop best shape racing airplane Five wins Cleveland Air Races lent some weight idea Gee Bee R-1 Jimmy Doolittle made famous 1932 followed kit latest line 1/32 scale Golden Age plastic kits Williams Bros kit features two differ ent cowlings two types wheels de tailed cockpit interior nylon monofila ment rigging Other ships series include Gee Bee R-1 Wedell Williams Caudron C460 suggested experienced model builders can appreciate degree accuracy quality Williams kit product review product review product review 136 Model Aviation Fuel Fitting Sets Fuel Shut Off Fuel Manifold Gapless Hinges Gapless Hinge Slotter Strut Fairings Codcpit Coaming FUR~ST Send SASE Complete Information 4040 24th Ave Forest Grove OR 97116 RODUCTS Phone 503 357-2732 uee Uee Z Plastic Model Kit $7 Williams Brothers 181 Pawnee St Marcos CA 92069 add another 10% Keep mind thrust power outputs glow engines parallel typical reciprocating fullscale aircraft engines because glow engines develop power high rpm whereas larger gas engines generate horsepower through lower rpm higher torque Thrust propor tional torque reason use speed reducers larger gas engines some Giant Scale modelseven though normal power output some large glow engines would sufficient important thing remember thrust relates maneuverability whereas power relates max imum flying speed Maneuverability final consideration does relate absolute flyability well model will duplicate prototypes ma neuver spectrum Two important character istics determine thrust/weight ratio power/weight ratio Most models can built much lighter weight required true dynamic scale still made fly like prototype Precision Scale Sport Scale enthusiasts have doing years As matter fact model lighter dynamic scale weight will land slower require less thrust equivalent thrust/weight course can now duplicate authentic landing speed bringing model little hotter have Similarly models thrust/weight greater prototype will capable shorter takeoff rollhut scale flight throttle back bit Indeed few maneuvers cannot duplicated true dynamic scale fashion airplane lighter has thrust dynamic scale values maneuvers pilot has very little inter mediate control over like spins vertical dives snap rolls Generally can conclude lightest possible model should built As long model weight less dynamic scale weight thrust/weight least large prototype model can made fly scale manner over major portion its maneuver spectrum true great number airplanes always possible generally has strike compromise between scale factor weight thrust power modeL Doing involves selecting value N scale factor estimating weight model based its size selecting engine produces thrust power required allows come up good idea what model will like given scale factor Figure range scale factors over range what practical select optimum Part III series will illustrate Space Shuttle/Hux Con finued page 73 shaping carved portions Shuttle paint markings use photos Time magazine Columbia has few changes marking over other drawings earlier Shuttles black top wing leading edge black top rudder Most display models show green-grey leading edge actual photos appear greytake pick plastic kits can provide detail would practical use flying model airfoil compromise between what would appear scale still give good performance Now have covered modifications lets build Shuttle Begin fuselage center section Cut out bulkheads cut out centers until cross-grain doublers have attached bulkhead too fragile centers removed Mark door edge cut lines both sides bulkhead cut door lines halfway through bulkhead thick ness final cut through made after center sheeted Glue bulkheads floor piece partial cuts facing inside Note angle bulkheads floor Glue pine longeron sets trying glue adjacent longerons other gap between sets hinge line doors Light pine longerons recommended stead balsa topreventwarpingofthe doors Wet side sheeting hot water glue dry side frame starting top door seam dry cut sheeting gaps between longerons complete cuts started bulkheads remove doors Tape doors back place Attach 1/16 cross grain doubler forward bulkhead careful apply glue door area Trim edges mini-saw cutout center bulkhead Assemble blocks soft balsa cut nose section Mark top side profile blocks cut band jigsaw keep blocks square table second cut September 1981 137 k/eueIF NEED6o BALSA.3t BALSA SHEETSBALSA BLOCKS 48 long24 long 4/ie4912 62 5213 86 6214 126 4Yie7422 86 4 9023 126 410833 240 6 /16BALSA STICKS 6/32 78 6 6 3/joSold packs 5 6162/16 70 70 /8~ 75 PLYWOOD 3M 95 6"48/ 110 /32 y1253M lie y136 square 70 /32 y175/16 square 75 5-ply185 square 85 /I6 y240M square 140 5-ply280 square 190 Write complete product listing Manufacturers dealers inquiries invited Special szes available Add $350 postage handling No minimum requirements NIIG NODELS INC PO BOX 396 Y MARYLAND 301 326-2554