LAST MONTHS installment cov ered foam material types foam chemical characteristics compatible sol vents glues etc month will cover construction safe use cut ting bows power supply techni ques cutting various types wing cores Next months installment concerns covering skinning use compat ible adhesives finishing Cutting Foam can easily equip yourself mas ter techniques cutting own foam cores following equipment required Cutting Bow like modelers handy tools can easily construct own bow required mate rials approximate costs follows 1 1 pc clear wood X 3 X 36 $150 22 pc 3/16 sic wire 75 32 pc 022 X 40 music wire 2 eye hooks10 52 2 alligator clips25 616 pc 16-gauge appliance cord90 715 pcsash cord20 8Masking electrical tape05 Total$300 following simple steps listed low can easily make bow evening 1 Lay out wood drilling holes a Using square make line side 1 edge b Using square make another line 1 end opposite 1 edge c Connect lines end 3 face diagonal line connects lines opposite edges d Mark center line 1 edges 2 Drill holes parallel diagonal line end a Drill pilot hole edge bit approximately least 2 keeping parallel diagonal line shown Fig 1 tricky part operation Drill slowly use too much pressure bit will tend walk grain wood Back drill out often sure drilling parallel diagonal line also keeping hole centered walking out toward side b Unless have extra long bit must now turn wood over repeat other edge went well holes should meet can sight through hole c Repeat process other end 3 Notch two 3/16 pieces music wire Clamp 3/16 X 9 pieces music wire vise file notch approximately /s should deep enough keep cutting wire slipping off should also smooth avoid nicking cutting wire otherwise likely break under tension heated 4 Install two 3/16 pieces music wire a Insert unnotched end 3/16 music wire hole nearest end wood sure notch facing out b Drive music wire through hole until approximately i/i protrud ing other side 5 Install eye hooks a Mark line top 6 end b Drill 1/16 hole center line approximately deep c Screw eye hooks hole 6 Attach sash cord a Tie knot center 5 piece sash cord leaving about 2 loop b Insert ends through eye hooks tie equal distance center knot 7 Attach power cord a Split 16-gauge 2-wire con ducter back about 24 end b Strip ends back about tach 2 alligator clips d Hook alligator clips cutting wire Note have power source adjustable through de sired range attach alligator clips protruding tops posts e Tape wires wood f Attach piece twine power cord loop sash cord needed hold power cord iques second article series covers making safe use cutting bows power supply techniques cutting various types wing cores U Bill Evans Max Lester clear work cutting 8 Attach cutting wire a Wrap cutting wire two turns around top long end 3/16 music wire next wood wrap turn around cutting wire another turn around 3/16 rod three turns around cutting wire cut off excess b Stretch tight repeat other end c Slide cutting wire down notch should now have proper tension 9 Your bow now ready attach cord running through two pulleys counterweight just balances other end pulley should directly above cutting will done other no will run have move get tools parts etc Add subtract weights until cutter remains whatever height left Make sure no binding moves up down smoothly light pull push 32 Model Aviation ivielung e cm wiin TflS DOW oescrioea Text mnis case jigs being used guide cutting wire bow suspended pulleys counterbalanced easy handling 10 If working kitchen someplace better-half wont stand still hooking pulleys ceiling just dont like approach skip steps 5 6 9 Before decide reason system hot wire needs kept away thing might damaged cutting cores Also bow needs easy control mini mum muscular effort make smooth cuts other good bow designs simple works well easy build use no ad justments cutting wire eventually stretches breaks sim ple inexpensive replace Power Source next piece equip ment required power source right wattage Volts X amps equals watts both AC DC However AC complicated measure 1/100 second intervals can measured peak root mean square Also line voltage sometimes varies tween 105 125 volts residential service bow described above requires ap proximately 70 80 watts Some alternative power sources 1 Stepped transformers similar ones used toy trains will work can find puts out enough amps HO too small good heavy duty larger trains like Lionel may overheat operate 10 15 minutes time 2 A continuously variable step-down transformer fairly expensive give precise control regulating tem perature wire also have range provide power hot-wire cutter making cut outs retractable land ing gear control rods etc can dangerous unless output voltage can limited around 24V can used regulate battery charger 3 A rheostat proper output will also current regulating job recommended final output however rheostat controls amps rather volts would safe rheostat can used vary input battery charger fixed output trans former 4 An automobile battery charger 8-amps output will job need some means adjusting output desirable power source 5 An automobile battery has used successfully again ingenuity re quired get right heat Electronics stores mail order houses good sources power supplies also electronic surplus stores salesman have little electronics knowl edge need some combination variable power provides approxi mately 70 watts better keep output voltage around 24 volts less sake safety example Volts s 24 volts X 3 amps atts recommended therefore use direct 110 volts cutting bow Mike Gaishin modeler engineer Heathkit suggested simple inexpensive way regulate output battery battery charger Make resistor length piano wire can wound heavy coke bottle strung like another cutting bow etc Attach lead output terminal battery charger end piano wire Put alligator clips both ends lead attach end 3/16 rod end cutting bow other resistor various distances until right wire temperature reached cutting bow lead other out put terminal battery charger would course attached 3/16 rod other end cutting bow Template Construction Two templates needed root rib tip rib wings See sectioning addi tional templates required wing made sections practical template material /s 1/16 aircraft plywood easy work readily available relatively expensive Literally dozens cores can February 1978 33 Foam wings various stages construction Reading up bot tom foam slab foam blank slab cut plan viewl foam core balsa leading trailing edges glued place foam core sheeted balsa completed wing after being covered Solarfilm bit tricky drilling holes wood bow lines located described care taken holes drilled opposite edges will meet middle course long drill help cut plywood template little reason go 1/16 formica 20-gauge aluminum durability harder work first step decide thick ness material used sheet ing Trace ribs kit plans allowing difference thick ness sheeting material Locate chord line draw LE TE both sides template Cut little outside outline sand carefully line using very fine sand paper finishing 280 wet-or-dry used dry good vibrating sander block hand sander should used insure no dips bumps hot wire will faithfully reproduce irregularities dont hesitate throw away template isnt perfect template will held place nails pushed through holes templates foam Next cutting speed marks must laid out template Cutting two per son job person will set pace call ing out numbers marks other will maintain same relative po sition matching numbers end marks should about t equally spaced TE chord line LE top bottom Number marks consecutively starting #1 first mark nearest LE tapered wings marks tip template must proportional root template two fairly easy ways First best using pair dividers can di vide distance starting TE same number equal spaces root appropriate number spacing can divided half correspond root template can get close same results using right combination scales engineers architects scales spaces should numbered consecutively should identically marked numbered side Label top template both sides Hold templates together proper relative position cut right wing panel label outsides right Now hold together proper rel ative position left panel label outside left Next select finishing nails6 8 penny 2 2 longto hold templates foam Drill three holes nails fit snugly shown Fig 2 plan make several sets same wing make positioning jigs align templates attaching foam can made same plywood airfoil templates chord line root template should parallel base jig marks made jig align chord line Mark outline template jig blank cut opening slightly smaller template sand fit jig should position root template approx imately /8 e bottom foam chord line tip template should first drawn tip jig parallel base jig TE tip template should raised slightly about anel above chord line traced cutting jig pro vide washout Draw outline mark aligning marks chord line template jig blank complete root jig Note tapered wing will clearance top bottom both jigs should have chord 34 Model Aviation Fig 2 hot wire about enter toam Blank has Iabeied avoid mistakeslike making two right panels Airfoil template positioned help three nails 2 2-1/2 long call ing Out numbers bow moves helper can match speed end Fig 3 blank about cut length picture already has cut width thickness Jig should wide enough widest wing expect cut guides should absolutely perpendicular base Note hot wire resting against guides Fig 4 simple jig usea cut blank plan view outline last step before cutting core Smaller bow handy expect much cutting Guide rails interchangeable sizes Fig 5 Jig cutting foam blank top view outilne tuli-scaie paper template taped base jig align blank cutting lines same height Simple jigs should also made cut foam blocks blanks proper thickness length top view plan prior cutting core jig cutting length shown Fig 3 should wide enough widest wing expect cut cut ting guides should absolutely perpen dicular base jig cutting blank thickness shown Fig 4 should wide enough longest panel plan cut height cutting guide rails should approximately h deeper particular wing panel cross section cut foam blank set rails Holes just large enough provide very snug fit positioning dowels should drilled through base cutting guide rails dowels should removable order permit marking hole location additional guide rails other wing thicknesses later Guide rails should perfectly straight smooth assure smooth square blanks foam blank should cut top view plan top view outline wing before cut core Make full scale paper template top view plan wing order lay out cut foam blank jig cut plan form blank shown Fig 5 width should allow longest panel plan cut turned necessary angle case tapered wing end cutting guides should exactly perpendicular base full scale paper template wing plan can taped base jig align foam blank cutting guide strips tacked place position blocks foam should square intersecting surfaces block must cut square possible exception would ends block could angle fore aft [F TE ends should still vertical top bottom block Prior cutting core blanks should cut thickness length top view plan outline Cutting Core Once wing blank cut core can cut follows First label blank very soft pencil felt-tip marking pen LE Topfor leading edge top side wing RightFor right panel Label other blank LE Top Left sure correct edge labeled [F tapered wings match blanks position assembled wing make final check far too easy accidentally cut two left two right panels 2 Mark chord line block end did make alignment jigs Check sure same height end parallel bottom blank tapered wing use root template mark proper height chord line assure proper clearance top bottom 3 Align root template chord line chord line root blank align alignment jig sure TE template extends proper distance beyond TE foam Check sure side template right left corresponds label top blank top template up 4 Carefully push nails through holes template foam per pendicular side template 5 Align tip template chord line chord line scribed blank LE about above chord line blank TE. align tip template jig 6 Carefully push nails through holes template blank Re move positioning jigs used Cutting two-person job person caller will control speed cut call out numbers wire passes follower will keep end wire speed needed pass same numbers tip same instant called caller 7 The caller should know approx imate speed foam will melt cutting experience gained cutting blanks block cut too fast wire will lag cen ter wing will rough true copy template airfoil cut too slow foam will melted too much again surface will rough true copy good idea practice some scrap first correct temperature residue cutting will slowly burn off wire thin grey smoke 8 Position blank flat surface under suspended bow cutter Seats should provided either end two cutters preferably foam should about eye level ease control Weights should placed foam hold steady during cutting Three lb weights should 9 The caller will turn bow test temperature piece scrap after warms up caller will call template person will grasp end rod cutting bow little above hot wire bring wire top protruding TE template 10 The caller will call ready cut follower will respond ready steady comfortable I caller will call enter now wire contacts foam side follower will start cut tip end word now 12 caller calls numbers wire reaches mark follower matches speed passing same numbers same time 13 As caller approaches leading edge calls slow slows down enough let center wire catch up comes out foam straight wire caller says out comes out leading edge follower should come out almost same instant Once cut begun stop may slow down speed up Stopping will produce grooves Best results will come continuous cut Note authors recommend flat surface TE TE spar LE LE spar makes wing much stronger easier sheet will described detail next issue 14 Finally bring wire back re peat process cut bottom side core starting underneath TE template first core isnt per fect dont discouraged little practice Continued page 94 February 1978 35 Fig 6 dihedral angle cutting template can attached jig shown pflOtOgrapn see local hobby dealer WI~E almost Stahl design40 years ago t~p tTA OGA 4 lOBts famous 24 1/2 WWdGSPAN 0% FOR PACKING AND POSTAGE VA NESIDENTS ADD 4% TAX RUBBER & CO2 WINNER AT THE 50th NATS Blot 221/2 WINGSPMI $695 Kioud King Ambivalent Dennyplane Miss Arpiem Brigadeer articles skeleton photo 85% Power house photo accompanying months column Depending model size four spruce spars ranging located approximately 30% 70% chord perpendicular other Fulldepth plywood dihedral joiners placed slotting ribs hacksaw stacks appropriate thickness epoxied flush spars Shear webs 1/16 balsa added grain running vertical alternating front rear spars picture illustrates front spars should always webbed rear set may also webbed model stunted weight factor Additional strength can gained D tube sheeting leading edge ever seems add spanwise strength torsional rigidity has stated times bears repeating wing will no stronger rigid after covered heat-shrink material uncovered wing seems flexible uncovered absolutely should covered shiny stuff full set shear webs still doesnt cure flexibility get out silk pre pared pick up pieces Consider four-spar shear-web tech nique next old-timer Dr D B Mathews 506 South Walnut Greens burg KS 67054 Foam/Evans/Lester continued page 35 will take care problem mean time core isnt too bad ways salvage will discussed next issue Sectioning hot-wire method cut ting has limitation cuts must straight line Wings taper angle either LE TE must cut sections glued together Follow same procedure *108 Spo&te 28 WING8PAN S6 INE MODELS 2820 DORR AVE FAIRFAX VA 22030 Send free brochure section described cutting wing panel tip template inboard section also root template outboard section additional section requires additional template tip section also necessary cut very long wings sections due limitations tension necessary keep wire straight power uniform heating wire Dihedral Angle Cutting sim plest ways cutting dihedral angle two-piece wing raise tip prescribed height height can calcu lated angle given make vertical cut root panel can best done after cutting core core still blank can done before sheeting end-cutting jig after sheeting saw and/or sanding block endcutting jig can also done dihedral-angle cutting template angle-cutting tem plate can attached foam blank nails pressed foam can attached cutting jig see Fig 6 template angle half com plement total desired angle both sections must cut match cross sections joint example tendegree angle required template gle will 900 100/2 850 Regardless method should done systematically avoid cutting angle wrong end wrong direction two-panel wings right left sure top up cut root panel except gull wings cut angle outboard section polyhedral wing sure top up cut outer end tip inboard section root outboard section except gull wings same principles apply core cut complete right left panel sectioned polyhedral angle continued Prop Mod/Aycock continued page 31 exact eyeball part just make sure line both blades same OK now have big black line front prop will become high point wood work begins Select rather rough flat wood rasp starting high point work towards leading edge rasp being careful cut away leading edge just take down rather sharp leading edge satisfied same thing again high point towards trailing edge worrying about curved rounded surface just make flat per drawing B Repeat other blade Round off high point shown drawing tips will get quite thin will no way subtract props efficiency should have pile wood dust front now will make some Using 80-grit again hand sand blades rather smooth finish See said hard maple props work best have done respectable job put prop balancing tool should ball park After little practice will able get right money fact time will balanced closer came out box Finish sand blades 280 wet dry dry course done Notice did take anything off back prop blades Thus did alter basic pitch just added airfoil front finished prop should have quite sharp leading trailing edges Leave raw wood finish nothing please Try procedure prop size now using check engine performance airplane flying have found often can go high er pitch prop engine would lug before will turn now author ity Experiment various sizes pitches until get satisfies air remember prop rework can prove itself air ground tach have questions regard ing prop rework please feel free drop line care magazine will happy answer questions Helicopter/B itner continued page 37 altitude 20-60 meters stay within fly course start finish procedures must checked directing official Timing flight can done several ways will tell what method used four timers located south end four north end 94 Model Aviation
Edition: Model Aviation - 1978/02
Page Numbers: 32, 33, 34, 35, 94
LAST MONTHS installment cov ered foam material types foam chemical characteristics compatible sol vents glues etc month will cover construction safe use cut ting bows power supply techni ques cutting various types wing cores Next months installment concerns covering skinning use compat ible adhesives finishing Cutting Foam can easily equip yourself mas ter techniques cutting own foam cores following equipment required Cutting Bow like modelers handy tools can easily construct own bow required mate rials approximate costs follows 1 1 pc clear wood X 3 X 36 $150 22 pc 3/16 sic wire 75 32 pc 022 X 40 music wire 2 eye hooks10 52 2 alligator clips25 616 pc 16-gauge appliance cord90 715 pcsash cord20 8Masking electrical tape05 Total$300 following simple steps listed low can easily make bow evening 1 Lay out wood drilling holes a Using square make line side 1 edge b Using square make another line 1 end opposite 1 edge c Connect lines end 3 face diagonal line connects lines opposite edges d Mark center line 1 edges 2 Drill holes parallel diagonal line end a Drill pilot hole edge bit approximately least 2 keeping parallel diagonal line shown Fig 1 tricky part operation Drill slowly use too much pressure bit will tend walk grain wood Back drill out often sure drilling parallel diagonal line also keeping hole centered walking out toward side b Unless have extra long bit must now turn wood over repeat other edge went well holes should meet can sight through hole c Repeat process other end 3 Notch two 3/16 pieces music wire Clamp 3/16 X 9 pieces music wire vise file notch approximately /s should deep enough keep cutting wire slipping off should also smooth avoid nicking cutting wire otherwise likely break under tension heated 4 Install two 3/16 pieces music wire a Insert unnotched end 3/16 music wire hole nearest end wood sure notch facing out b Drive music wire through hole until approximately i/i protrud ing other side 5 Install eye hooks a Mark line top 6 end b Drill 1/16 hole center line approximately deep c Screw eye hooks hole 6 Attach sash cord a Tie knot center 5 piece sash cord leaving about 2 loop b Insert ends through eye hooks tie equal distance center knot 7 Attach power cord a Split 16-gauge 2-wire con ducter back about 24 end b Strip ends back about tach 2 alligator clips d Hook alligator clips cutting wire Note have power source adjustable through de sired range attach alligator clips protruding tops posts e Tape wires wood f Attach piece twine power cord loop sash cord needed hold power cord iques second article series covers making safe use cutting bows power supply techniques cutting various types wing cores U Bill Evans Max Lester clear work cutting 8 Attach cutting wire a Wrap cutting wire two turns around top long end 3/16 music wire next wood wrap turn around cutting wire another turn around 3/16 rod three turns around cutting wire cut off excess b Stretch tight repeat other end c Slide cutting wire down notch should now have proper tension 9 Your bow now ready attach cord running through two pulleys counterweight just balances other end pulley should directly above cutting will done other no will run have move get tools parts etc Add subtract weights until cutter remains whatever height left Make sure no binding moves up down smoothly light pull push 32 Model Aviation ivielung e cm wiin TflS DOW oescrioea Text mnis case jigs being used guide cutting wire bow suspended pulleys counterbalanced easy handling 10 If working kitchen someplace better-half wont stand still hooking pulleys ceiling just dont like approach skip steps 5 6 9 Before decide reason system hot wire needs kept away thing might damaged cutting cores Also bow needs easy control mini mum muscular effort make smooth cuts other good bow designs simple works well easy build use no ad justments cutting wire eventually stretches breaks sim ple inexpensive replace Power Source next piece equip ment required power source right wattage Volts X amps equals watts both AC DC However AC complicated measure 1/100 second intervals can measured peak root mean square Also line voltage sometimes varies tween 105 125 volts residential service bow described above requires ap proximately 70 80 watts Some alternative power sources 1 Stepped transformers similar ones used toy trains will work can find puts out enough amps HO too small good heavy duty larger trains like Lionel may overheat operate 10 15 minutes time 2 A continuously variable step-down transformer fairly expensive give precise control regulating tem perature wire also have range provide power hot-wire cutter making cut outs retractable land ing gear control rods etc can dangerous unless output voltage can limited around 24V can used regulate battery charger 3 A rheostat proper output will also current regulating job recommended final output however rheostat controls amps rather volts would safe rheostat can used vary input battery charger fixed output trans former 4 An automobile battery charger 8-amps output will job need some means adjusting output desirable power source 5 An automobile battery has used successfully again ingenuity re quired get right heat Electronics stores mail order houses good sources power supplies also electronic surplus stores salesman have little electronics knowl edge need some combination variable power provides approxi mately 70 watts better keep output voltage around 24 volts less sake safety example Volts s 24 volts X 3 amps atts recommended therefore use direct 110 volts cutting bow Mike Gaishin modeler engineer Heathkit suggested simple inexpensive way regulate output battery battery charger Make resistor length piano wire can wound heavy coke bottle strung like another cutting bow etc Attach lead output terminal battery charger end piano wire Put alligator clips both ends lead attach end 3/16 rod end cutting bow other resistor various distances until right wire temperature reached cutting bow lead other out put terminal battery charger would course attached 3/16 rod other end cutting bow Template Construction Two templates needed root rib tip rib wings See sectioning addi tional templates required wing made sections practical template material /s 1/16 aircraft plywood easy work readily available relatively expensive Literally dozens cores can February 1978 33 Foam wings various stages construction Reading up bot tom foam slab foam blank slab cut plan viewl foam core balsa leading trailing edges glued place foam core sheeted balsa completed wing after being covered Solarfilm bit tricky drilling holes wood bow lines located described care taken holes drilled opposite edges will meet middle course long drill help cut plywood template little reason go 1/16 formica 20-gauge aluminum durability harder work first step decide thick ness material used sheet ing Trace ribs kit plans allowing difference thick ness sheeting material Locate chord line draw LE TE both sides template Cut little outside outline sand carefully line using very fine sand paper finishing 280 wet-or-dry used dry good vibrating sander block hand sander should used insure no dips bumps hot wire will faithfully reproduce irregularities dont hesitate throw away template isnt perfect template will held place nails pushed through holes templates foam Next cutting speed marks must laid out template Cutting two per son job person will set pace call ing out numbers marks other will maintain same relative po sition matching numbers end marks should about t equally spaced TE chord line LE top bottom Number marks consecutively starting #1 first mark nearest LE tapered wings marks tip template must proportional root template two fairly easy ways First best using pair dividers can di vide distance starting TE same number equal spaces root appropriate number spacing can divided half correspond root template can get close same results using right combination scales engineers architects scales spaces should numbered consecutively should identically marked numbered side Label top template both sides Hold templates together proper relative position cut right wing panel label outsides right Now hold together proper rel ative position left panel label outside left Next select finishing nails6 8 penny 2 2 longto hold templates foam Drill three holes nails fit snugly shown Fig 2 plan make several sets same wing make positioning jigs align templates attaching foam can made same plywood airfoil templates chord line root template should parallel base jig marks made jig align chord line Mark outline template jig blank cut opening slightly smaller template sand fit jig should position root template approx imately /8 e bottom foam chord line tip template should first drawn tip jig parallel base jig TE tip template should raised slightly about anel above chord line traced cutting jig pro vide washout Draw outline mark aligning marks chord line template jig blank complete root jig Note tapered wing will clearance top bottom both jigs should have chord 34 Model Aviation Fig 2 hot wire about enter toam Blank has Iabeied avoid mistakeslike making two right panels Airfoil template positioned help three nails 2 2-1/2 long call ing Out numbers bow moves helper can match speed end Fig 3 blank about cut length picture already has cut width thickness Jig should wide enough widest wing expect cut guides should absolutely perpendicular base Note hot wire resting against guides Fig 4 simple jig usea cut blank plan view outline last step before cutting core Smaller bow handy expect much cutting Guide rails interchangeable sizes Fig 5 Jig cutting foam blank top view outilne tuli-scaie paper template taped base jig align blank cutting lines same height Simple jigs should also made cut foam blocks blanks proper thickness length top view plan prior cutting core jig cutting length shown Fig 3 should wide enough widest wing expect cut cut ting guides should absolutely perpen dicular base jig cutting blank thickness shown Fig 4 should wide enough longest panel plan cut height cutting guide rails should approximately h deeper particular wing panel cross section cut foam blank set rails Holes just large enough provide very snug fit positioning dowels should drilled through base cutting guide rails dowels should removable order permit marking hole location additional guide rails other wing thicknesses later Guide rails should perfectly straight smooth assure smooth square blanks foam blank should cut top view plan top view outline wing before cut core Make full scale paper template top view plan wing order lay out cut foam blank jig cut plan form blank shown Fig 5 width should allow longest panel plan cut turned necessary angle case tapered wing end cutting guides should exactly perpendicular base full scale paper template wing plan can taped base jig align foam blank cutting guide strips tacked place position blocks foam should square intersecting surfaces block must cut square possible exception would ends block could angle fore aft [F TE ends should still vertical top bottom block Prior cutting core blanks should cut thickness length top view plan outline Cutting Core Once wing blank cut core can cut follows First label blank very soft pencil felt-tip marking pen LE Topfor leading edge top side wing RightFor right panel Label other blank LE Top Left sure correct edge labeled [F tapered wings match blanks position assembled wing make final check far too easy accidentally cut two left two right panels 2 Mark chord line block end did make alignment jigs Check sure same height end parallel bottom blank tapered wing use root template mark proper height chord line assure proper clearance top bottom 3 Align root template chord line chord line root blank align alignment jig sure TE template extends proper distance beyond TE foam Check sure side template right left corresponds label top blank top template up 4 Carefully push nails through holes template foam per pendicular side template 5 Align tip template chord line chord line scribed blank LE about above chord line blank TE. align tip template jig 6 Carefully push nails through holes template blank Re move positioning jigs used Cutting two-person job person caller will control speed cut call out numbers wire passes follower will keep end wire speed needed pass same numbers tip same instant called caller 7 The caller should know approx imate speed foam will melt cutting experience gained cutting blanks block cut too fast wire will lag cen ter wing will rough true copy template airfoil cut too slow foam will melted too much again surface will rough true copy good idea practice some scrap first correct temperature residue cutting will slowly burn off wire thin grey smoke 8 Position blank flat surface under suspended bow cutter Seats should provided either end two cutters preferably foam should about eye level ease control Weights should placed foam hold steady during cutting Three lb weights should 9 The caller will turn bow test temperature piece scrap after warms up caller will call template person will grasp end rod cutting bow little above hot wire bring wire top protruding TE template 10 The caller will call ready cut follower will respond ready steady comfortable I caller will call enter now wire contacts foam side follower will start cut tip end word now 12 caller calls numbers wire reaches mark follower matches speed passing same numbers same time 13 As caller approaches leading edge calls slow slows down enough let center wire catch up comes out foam straight wire caller says out comes out leading edge follower should come out almost same instant Once cut begun stop may slow down speed up Stopping will produce grooves Best results will come continuous cut Note authors recommend flat surface TE TE spar LE LE spar makes wing much stronger easier sheet will described detail next issue 14 Finally bring wire back re peat process cut bottom side core starting underneath TE template first core isnt per fect dont discouraged little practice Continued page 94 February 1978 35 Fig 6 dihedral angle cutting template can attached jig shown pflOtOgrapn see local hobby dealer WI~E almost Stahl design40 years ago t~p tTA OGA 4 lOBts famous 24 1/2 WWdGSPAN 0% FOR PACKING AND POSTAGE VA NESIDENTS ADD 4% TAX RUBBER & CO2 WINNER AT THE 50th NATS Blot 221/2 WINGSPMI $695 Kioud King Ambivalent Dennyplane Miss Arpiem Brigadeer articles skeleton photo 85% Power house photo accompanying months column Depending model size four spruce spars ranging located approximately 30% 70% chord perpendicular other Fulldepth plywood dihedral joiners placed slotting ribs hacksaw stacks appropriate thickness epoxied flush spars Shear webs 1/16 balsa added grain running vertical alternating front rear spars picture illustrates front spars should always webbed rear set may also webbed model stunted weight factor Additional strength can gained D tube sheeting leading edge ever seems add spanwise strength torsional rigidity has stated times bears repeating wing will no stronger rigid after covered heat-shrink material uncovered wing seems flexible uncovered absolutely should covered shiny stuff full set shear webs still doesnt cure flexibility get out silk pre pared pick up pieces Consider four-spar shear-web tech nique next old-timer Dr D B Mathews 506 South Walnut Greens burg KS 67054 Foam/Evans/Lester continued page 35 will take care problem mean time core isnt too bad ways salvage will discussed next issue Sectioning hot-wire method cut ting has limitation cuts must straight line Wings taper angle either LE TE must cut sections glued together Follow same procedure *108 Spo&te 28 WING8PAN S6 INE MODELS 2820 DORR AVE FAIRFAX VA 22030 Send free brochure section described cutting wing panel tip template inboard section also root template outboard section additional section requires additional template tip section also necessary cut very long wings sections due limitations tension necessary keep wire straight power uniform heating wire Dihedral Angle Cutting sim plest ways cutting dihedral angle two-piece wing raise tip prescribed height height can calcu lated angle given make vertical cut root panel can best done after cutting core core still blank can done before sheeting end-cutting jig after sheeting saw and/or sanding block endcutting jig can also done dihedral-angle cutting template angle-cutting tem plate can attached foam blank nails pressed foam can attached cutting jig see Fig 6 template angle half com plement total desired angle both sections must cut match cross sections joint example tendegree angle required template gle will 900 100/2 850 Regardless method should done systematically avoid cutting angle wrong end wrong direction two-panel wings right left sure top up cut root panel except gull wings cut angle outboard section polyhedral wing sure top up cut outer end tip inboard section root outboard section except gull wings same principles apply core cut complete right left panel sectioned polyhedral angle continued Prop Mod/Aycock continued page 31 exact eyeball part just make sure line both blades same OK now have big black line front prop will become high point wood work begins Select rather rough flat wood rasp starting high point work towards leading edge rasp being careful cut away leading edge just take down rather sharp leading edge satisfied same thing again high point towards trailing edge worrying about curved rounded surface just make flat per drawing B Repeat other blade Round off high point shown drawing tips will get quite thin will no way subtract props efficiency should have pile wood dust front now will make some Using 80-grit again hand sand blades rather smooth finish See said hard maple props work best have done respectable job put prop balancing tool should ball park After little practice will able get right money fact time will balanced closer came out box Finish sand blades 280 wet dry dry course done Notice did take anything off back prop blades Thus did alter basic pitch just added airfoil front finished prop should have quite sharp leading trailing edges Leave raw wood finish nothing please Try procedure prop size now using check engine performance airplane flying have found often can go high er pitch prop engine would lug before will turn now author ity Experiment various sizes pitches until get satisfies air remember prop rework can prove itself air ground tach have questions regard ing prop rework please feel free drop line care magazine will happy answer questions Helicopter/B itner continued page 37 altitude 20-60 meters stay within fly course start finish procedures must checked directing official Timing flight can done several ways will tell what method used four timers located south end four north end 94 Model Aviation
Edition: Model Aviation - 1978/02
Page Numbers: 32, 33, 34, 35, 94
LAST MONTHS installment cov ered foam material types foam chemical characteristics compatible sol vents glues etc month will cover construction safe use cut ting bows power supply techni ques cutting various types wing cores Next months installment concerns covering skinning use compat ible adhesives finishing Cutting Foam can easily equip yourself mas ter techniques cutting own foam cores following equipment required Cutting Bow like modelers handy tools can easily construct own bow required mate rials approximate costs follows 1 1 pc clear wood X 3 X 36 $150 22 pc 3/16 sic wire 75 32 pc 022 X 40 music wire 2 eye hooks10 52 2 alligator clips25 616 pc 16-gauge appliance cord90 715 pcsash cord20 8Masking electrical tape05 Total$300 following simple steps listed low can easily make bow evening 1 Lay out wood drilling holes a Using square make line side 1 edge b Using square make another line 1 end opposite 1 edge c Connect lines end 3 face diagonal line connects lines opposite edges d Mark center line 1 edges 2 Drill holes parallel diagonal line end a Drill pilot hole edge bit approximately least 2 keeping parallel diagonal line shown Fig 1 tricky part operation Drill slowly use too much pressure bit will tend walk grain wood Back drill out often sure drilling parallel diagonal line also keeping hole centered walking out toward side b Unless have extra long bit must now turn wood over repeat other edge went well holes should meet can sight through hole c Repeat process other end 3 Notch two 3/16 pieces music wire Clamp 3/16 X 9 pieces music wire vise file notch approximately /s should deep enough keep cutting wire slipping off should also smooth avoid nicking cutting wire otherwise likely break under tension heated 4 Install two 3/16 pieces music wire a Insert unnotched end 3/16 music wire hole nearest end wood sure notch facing out b Drive music wire through hole until approximately i/i protrud ing other side 5 Install eye hooks a Mark line top 6 end b Drill 1/16 hole center line approximately deep c Screw eye hooks hole 6 Attach sash cord a Tie knot center 5 piece sash cord leaving about 2 loop b Insert ends through eye hooks tie equal distance center knot 7 Attach power cord a Split 16-gauge 2-wire con ducter back about 24 end b Strip ends back about tach 2 alligator clips d Hook alligator clips cutting wire Note have power source adjustable through de sired range attach alligator clips protruding tops posts e Tape wires wood f Attach piece twine power cord loop sash cord needed hold power cord iques second article series covers making safe use cutting bows power supply techniques cutting various types wing cores U Bill Evans Max Lester clear work cutting 8 Attach cutting wire a Wrap cutting wire two turns around top long end 3/16 music wire next wood wrap turn around cutting wire another turn around 3/16 rod three turns around cutting wire cut off excess b Stretch tight repeat other end c Slide cutting wire down notch should now have proper tension 9 Your bow now ready attach cord running through two pulleys counterweight just balances other end pulley should directly above cutting will done other no will run have move get tools parts etc Add subtract weights until cutter remains whatever height left Make sure no binding moves up down smoothly light pull push 32 Model Aviation ivielung e cm wiin TflS DOW oescrioea Text mnis case jigs being used guide cutting wire bow suspended pulleys counterbalanced easy handling 10 If working kitchen someplace better-half wont stand still hooking pulleys ceiling just dont like approach skip steps 5 6 9 Before decide reason system hot wire needs kept away thing might damaged cutting cores Also bow needs easy control mini mum muscular effort make smooth cuts other good bow designs simple works well easy build use no ad justments cutting wire eventually stretches breaks sim ple inexpensive replace Power Source next piece equip ment required power source right wattage Volts X amps equals watts both AC DC However AC complicated measure 1/100 second intervals can measured peak root mean square Also line voltage sometimes varies tween 105 125 volts residential service bow described above requires ap proximately 70 80 watts Some alternative power sources 1 Stepped transformers similar ones used toy trains will work can find puts out enough amps HO too small good heavy duty larger trains like Lionel may overheat operate 10 15 minutes time 2 A continuously variable step-down transformer fairly expensive give precise control regulating tem perature wire also have range provide power hot-wire cutter making cut outs retractable land ing gear control rods etc can dangerous unless output voltage can limited around 24V can used regulate battery charger 3 A rheostat proper output will also current regulating job recommended final output however rheostat controls amps rather volts would safe rheostat can used vary input battery charger fixed output trans former 4 An automobile battery charger 8-amps output will job need some means adjusting output desirable power source 5 An automobile battery has used successfully again ingenuity re quired get right heat Electronics stores mail order houses good sources power supplies also electronic surplus stores salesman have little electronics knowl edge need some combination variable power provides approxi mately 70 watts better keep output voltage around 24 volts less sake safety example Volts s 24 volts X 3 amps atts recommended therefore use direct 110 volts cutting bow Mike Gaishin modeler engineer Heathkit suggested simple inexpensive way regulate output battery battery charger Make resistor length piano wire can wound heavy coke bottle strung like another cutting bow etc Attach lead output terminal battery charger end piano wire Put alligator clips both ends lead attach end 3/16 rod end cutting bow other resistor various distances until right wire temperature reached cutting bow lead other out put terminal battery charger would course attached 3/16 rod other end cutting bow Template Construction Two templates needed root rib tip rib wings See sectioning addi tional templates required wing made sections practical template material /s 1/16 aircraft plywood easy work readily available relatively expensive Literally dozens cores can February 1978 33 Foam wings various stages construction Reading up bot tom foam slab foam blank slab cut plan viewl foam core balsa leading trailing edges glued place foam core sheeted balsa completed wing after being covered Solarfilm bit tricky drilling holes wood bow lines located described care taken holes drilled opposite edges will meet middle course long drill help cut plywood template little reason go 1/16 formica 20-gauge aluminum durability harder work first step decide thick ness material used sheet ing Trace ribs kit plans allowing difference thick ness sheeting material Locate chord line draw LE TE both sides template Cut little outside outline sand carefully line using very fine sand paper finishing 280 wet-or-dry used dry good vibrating sander block hand sander should used insure no dips bumps hot wire will faithfully reproduce irregularities dont hesitate throw away template isnt perfect template will held place nails pushed through holes templates foam Next cutting speed marks must laid out template Cutting two per son job person will set pace call ing out numbers marks other will maintain same relative po sition matching numbers end marks should about t equally spaced TE chord line LE top bottom Number marks consecutively starting #1 first mark nearest LE tapered wings marks tip template must proportional root template two fairly easy ways First best using pair dividers can di vide distance starting TE same number equal spaces root appropriate number spacing can divided half correspond root template can get close same results using right combination scales engineers architects scales spaces should numbered consecutively should identically marked numbered side Label top template both sides Hold templates together proper relative position cut right wing panel label outsides right Now hold together proper rel ative position left panel label outside left Next select finishing nails6 8 penny 2 2 longto hold templates foam Drill three holes nails fit snugly shown Fig 2 plan make several sets same wing make positioning jigs align templates attaching foam can made same plywood airfoil templates chord line root template should parallel base jig marks made jig align chord line Mark outline template jig blank cut opening slightly smaller template sand fit jig should position root template approx imately /8 e bottom foam chord line tip template should first drawn tip jig parallel base jig TE tip template should raised slightly about anel above chord line traced cutting jig pro vide washout Draw outline mark aligning marks chord line template jig blank complete root jig Note tapered wing will clearance top bottom both jigs should have chord 34 Model Aviation Fig 2 hot wire about enter toam Blank has Iabeied avoid mistakeslike making two right panels Airfoil template positioned help three nails 2 2-1/2 long call ing Out numbers bow moves helper can match speed end Fig 3 blank about cut length picture already has cut width thickness Jig should wide enough widest wing expect cut guides should absolutely perpendicular base Note hot wire resting against guides Fig 4 simple jig usea cut blank plan view outline last step before cutting core Smaller bow handy expect much cutting Guide rails interchangeable sizes Fig 5 Jig cutting foam blank top view outilne tuli-scaie paper template taped base jig align blank cutting lines same height Simple jigs should also made cut foam blocks blanks proper thickness length top view plan prior cutting core jig cutting length shown Fig 3 should wide enough widest wing expect cut cut ting guides should absolutely perpen dicular base jig cutting blank thickness shown Fig 4 should wide enough longest panel plan cut height cutting guide rails should approximately h deeper particular wing panel cross section cut foam blank set rails Holes just large enough provide very snug fit positioning dowels should drilled through base cutting guide rails dowels should removable order permit marking hole location additional guide rails other wing thicknesses later Guide rails should perfectly straight smooth assure smooth square blanks foam blank should cut top view plan top view outline wing before cut core Make full scale paper template top view plan wing order lay out cut foam blank jig cut plan form blank shown Fig 5 width should allow longest panel plan cut turned necessary angle case tapered wing end cutting guides should exactly perpendicular base full scale paper template wing plan can taped base jig align foam blank cutting guide strips tacked place position blocks foam should square intersecting surfaces block must cut square possible exception would ends block could angle fore aft [F TE ends should still vertical top bottom block Prior cutting core blanks should cut thickness length top view plan outline Cutting Core Once wing blank cut core can cut follows First label blank very soft pencil felt-tip marking pen LE Topfor leading edge top side wing RightFor right panel Label other blank LE Top Left sure correct edge labeled [F tapered wings match blanks position assembled wing make final check far too easy accidentally cut two left two right panels 2 Mark chord line block end did make alignment jigs Check sure same height end parallel bottom blank tapered wing use root template mark proper height chord line assure proper clearance top bottom 3 Align root template chord line chord line root blank align alignment jig sure TE template extends proper distance beyond TE foam Check sure side template right left corresponds label top blank top template up 4 Carefully push nails through holes template foam per pendicular side template 5 Align tip template chord line chord line scribed blank LE about above chord line blank TE. align tip template jig 6 Carefully push nails through holes template blank Re move positioning jigs used Cutting two-person job person caller will control speed cut call out numbers wire passes follower will keep end wire speed needed pass same numbers tip same instant called caller 7 The caller should know approx imate speed foam will melt cutting experience gained cutting blanks block cut too fast wire will lag cen ter wing will rough true copy template airfoil cut too slow foam will melted too much again surface will rough true copy good idea practice some scrap first correct temperature residue cutting will slowly burn off wire thin grey smoke 8 Position blank flat surface under suspended bow cutter Seats should provided either end two cutters preferably foam should about eye level ease control Weights should placed foam hold steady during cutting Three lb weights should 9 The caller will turn bow test temperature piece scrap after warms up caller will call template person will grasp end rod cutting bow little above hot wire bring wire top protruding TE template 10 The caller will call ready cut follower will respond ready steady comfortable I caller will call enter now wire contacts foam side follower will start cut tip end word now 12 caller calls numbers wire reaches mark follower matches speed passing same numbers same time 13 As caller approaches leading edge calls slow slows down enough let center wire catch up comes out foam straight wire caller says out comes out leading edge follower should come out almost same instant Once cut begun stop may slow down speed up Stopping will produce grooves Best results will come continuous cut Note authors recommend flat surface TE TE spar LE LE spar makes wing much stronger easier sheet will described detail next issue 14 Finally bring wire back re peat process cut bottom side core starting underneath TE template first core isnt per fect dont discouraged little practice Continued page 94 February 1978 35 Fig 6 dihedral angle cutting template can attached jig shown pflOtOgrapn see local hobby dealer WI~E almost Stahl design40 years ago t~p tTA OGA 4 lOBts famous 24 1/2 WWdGSPAN 0% FOR PACKING AND POSTAGE VA NESIDENTS ADD 4% TAX RUBBER & CO2 WINNER AT THE 50th NATS Blot 221/2 WINGSPMI $695 Kioud King Ambivalent Dennyplane Miss Arpiem Brigadeer articles skeleton photo 85% Power house photo accompanying months column Depending model size four spruce spars ranging located approximately 30% 70% chord perpendicular other Fulldepth plywood dihedral joiners placed slotting ribs hacksaw stacks appropriate thickness epoxied flush spars Shear webs 1/16 balsa added grain running vertical alternating front rear spars picture illustrates front spars should always webbed rear set may also webbed model stunted weight factor Additional strength can gained D tube sheeting leading edge ever seems add spanwise strength torsional rigidity has stated times bears repeating wing will no stronger rigid after covered heat-shrink material uncovered wing seems flexible uncovered absolutely should covered shiny stuff full set shear webs still doesnt cure flexibility get out silk pre pared pick up pieces Consider four-spar shear-web tech nique next old-timer Dr D B Mathews 506 South Walnut Greens burg KS 67054 Foam/Evans/Lester continued page 35 will take care problem mean time core isnt too bad ways salvage will discussed next issue Sectioning hot-wire method cut ting has limitation cuts must straight line Wings taper angle either LE TE must cut sections glued together Follow same procedure *108 Spo&te 28 WING8PAN S6 INE MODELS 2820 DORR AVE FAIRFAX VA 22030 Send free brochure section described cutting wing panel tip template inboard section also root template outboard section additional section requires additional template tip section also necessary cut very long wings sections due limitations tension necessary keep wire straight power uniform heating wire Dihedral Angle Cutting sim plest ways cutting dihedral angle two-piece wing raise tip prescribed height height can calcu lated angle given make vertical cut root panel can best done after cutting core core still blank can done before sheeting end-cutting jig after sheeting saw and/or sanding block endcutting jig can also done dihedral-angle cutting template angle-cutting tem plate can attached foam blank nails pressed foam can attached cutting jig see Fig 6 template angle half com plement total desired angle both sections must cut match cross sections joint example tendegree angle required template gle will 900 100/2 850 Regardless method should done systematically avoid cutting angle wrong end wrong direction two-panel wings right left sure top up cut root panel except gull wings cut angle outboard section polyhedral wing sure top up cut outer end tip inboard section root outboard section except gull wings same principles apply core cut complete right left panel sectioned polyhedral angle continued Prop Mod/Aycock continued page 31 exact eyeball part just make sure line both blades same OK now have big black line front prop will become high point wood work begins Select rather rough flat wood rasp starting high point work towards leading edge rasp being careful cut away leading edge just take down rather sharp leading edge satisfied same thing again high point towards trailing edge worrying about curved rounded surface just make flat per drawing B Repeat other blade Round off high point shown drawing tips will get quite thin will no way subtract props efficiency should have pile wood dust front now will make some Using 80-grit again hand sand blades rather smooth finish See said hard maple props work best have done respectable job put prop balancing tool should ball park After little practice will able get right money fact time will balanced closer came out box Finish sand blades 280 wet dry dry course done Notice did take anything off back prop blades Thus did alter basic pitch just added airfoil front finished prop should have quite sharp leading trailing edges Leave raw wood finish nothing please Try procedure prop size now using check engine performance airplane flying have found often can go high er pitch prop engine would lug before will turn now author ity Experiment various sizes pitches until get satisfies air remember prop rework can prove itself air ground tach have questions regard ing prop rework please feel free drop line care magazine will happy answer questions Helicopter/B itner continued page 37 altitude 20-60 meters stay within fly course start finish procedures must checked directing official Timing flight can done several ways will tell what method used four timers located south end four north end 94 Model Aviation
Edition: Model Aviation - 1978/02
Page Numbers: 32, 33, 34, 35, 94
LAST MONTHS installment cov ered foam material types foam chemical characteristics compatible sol vents glues etc month will cover construction safe use cut ting bows power supply techni ques cutting various types wing cores Next months installment concerns covering skinning use compat ible adhesives finishing Cutting Foam can easily equip yourself mas ter techniques cutting own foam cores following equipment required Cutting Bow like modelers handy tools can easily construct own bow required mate rials approximate costs follows 1 1 pc clear wood X 3 X 36 $150 22 pc 3/16 sic wire 75 32 pc 022 X 40 music wire 2 eye hooks10 52 2 alligator clips25 616 pc 16-gauge appliance cord90 715 pcsash cord20 8Masking electrical tape05 Total$300 following simple steps listed low can easily make bow evening 1 Lay out wood drilling holes a Using square make line side 1 edge b Using square make another line 1 end opposite 1 edge c Connect lines end 3 face diagonal line connects lines opposite edges d Mark center line 1 edges 2 Drill holes parallel diagonal line end a Drill pilot hole edge bit approximately least 2 keeping parallel diagonal line shown Fig 1 tricky part operation Drill slowly use too much pressure bit will tend walk grain wood Back drill out often sure drilling parallel diagonal line also keeping hole centered walking out toward side b Unless have extra long bit must now turn wood over repeat other edge went well holes should meet can sight through hole c Repeat process other end 3 Notch two 3/16 pieces music wire Clamp 3/16 X 9 pieces music wire vise file notch approximately /s should deep enough keep cutting wire slipping off should also smooth avoid nicking cutting wire otherwise likely break under tension heated 4 Install two 3/16 pieces music wire a Insert unnotched end 3/16 music wire hole nearest end wood sure notch facing out b Drive music wire through hole until approximately i/i protrud ing other side 5 Install eye hooks a Mark line top 6 end b Drill 1/16 hole center line approximately deep c Screw eye hooks hole 6 Attach sash cord a Tie knot center 5 piece sash cord leaving about 2 loop b Insert ends through eye hooks tie equal distance center knot 7 Attach power cord a Split 16-gauge 2-wire con ducter back about 24 end b Strip ends back about tach 2 alligator clips d Hook alligator clips cutting wire Note have power source adjustable through de sired range attach alligator clips protruding tops posts e Tape wires wood f Attach piece twine power cord loop sash cord needed hold power cord iques second article series covers making safe use cutting bows power supply techniques cutting various types wing cores U Bill Evans Max Lester clear work cutting 8 Attach cutting wire a Wrap cutting wire two turns around top long end 3/16 music wire next wood wrap turn around cutting wire another turn around 3/16 rod three turns around cutting wire cut off excess b Stretch tight repeat other end c Slide cutting wire down notch should now have proper tension 9 Your bow now ready attach cord running through two pulleys counterweight just balances other end pulley should directly above cutting will done other no will run have move get tools parts etc Add subtract weights until cutter remains whatever height left Make sure no binding moves up down smoothly light pull push 32 Model Aviation ivielung e cm wiin TflS DOW oescrioea Text mnis case jigs being used guide cutting wire bow suspended pulleys counterbalanced easy handling 10 If working kitchen someplace better-half wont stand still hooking pulleys ceiling just dont like approach skip steps 5 6 9 Before decide reason system hot wire needs kept away thing might damaged cutting cores Also bow needs easy control mini mum muscular effort make smooth cuts other good bow designs simple works well easy build use no ad justments cutting wire eventually stretches breaks sim ple inexpensive replace Power Source next piece equip ment required power source right wattage Volts X amps equals watts both AC DC However AC complicated measure 1/100 second intervals can measured peak root mean square Also line voltage sometimes varies tween 105 125 volts residential service bow described above requires ap proximately 70 80 watts Some alternative power sources 1 Stepped transformers similar ones used toy trains will work can find puts out enough amps HO too small good heavy duty larger trains like Lionel may overheat operate 10 15 minutes time 2 A continuously variable step-down transformer fairly expensive give precise control regulating tem perature wire also have range provide power hot-wire cutter making cut outs retractable land ing gear control rods etc can dangerous unless output voltage can limited around 24V can used regulate battery charger 3 A rheostat proper output will also current regulating job recommended final output however rheostat controls amps rather volts would safe rheostat can used vary input battery charger fixed output trans former 4 An automobile battery charger 8-amps output will job need some means adjusting output desirable power source 5 An automobile battery has used successfully again ingenuity re quired get right heat Electronics stores mail order houses good sources power supplies also electronic surplus stores salesman have little electronics knowl edge need some combination variable power provides approxi mately 70 watts better keep output voltage around 24 volts less sake safety example Volts s 24 volts X 3 amps atts recommended therefore use direct 110 volts cutting bow Mike Gaishin modeler engineer Heathkit suggested simple inexpensive way regulate output battery battery charger Make resistor length piano wire can wound heavy coke bottle strung like another cutting bow etc Attach lead output terminal battery charger end piano wire Put alligator clips both ends lead attach end 3/16 rod end cutting bow other resistor various distances until right wire temperature reached cutting bow lead other out put terminal battery charger would course attached 3/16 rod other end cutting bow Template Construction Two templates needed root rib tip rib wings See sectioning addi tional templates required wing made sections practical template material /s 1/16 aircraft plywood easy work readily available relatively expensive Literally dozens cores can February 1978 33 Foam wings various stages construction Reading up bot tom foam slab foam blank slab cut plan viewl foam core balsa leading trailing edges glued place foam core sheeted balsa completed wing after being covered Solarfilm bit tricky drilling holes wood bow lines located described care taken holes drilled opposite edges will meet middle course long drill help cut plywood template little reason go 1/16 formica 20-gauge aluminum durability harder work first step decide thick ness material used sheet ing Trace ribs kit plans allowing difference thick ness sheeting material Locate chord line draw LE TE both sides template Cut little outside outline sand carefully line using very fine sand paper finishing 280 wet-or-dry used dry good vibrating sander block hand sander should used insure no dips bumps hot wire will faithfully reproduce irregularities dont hesitate throw away template isnt perfect template will held place nails pushed through holes templates foam Next cutting speed marks must laid out template Cutting two per son job person will set pace call ing out numbers marks other will maintain same relative po sition matching numbers end marks should about t equally spaced TE chord line LE top bottom Number marks consecutively starting #1 first mark nearest LE tapered wings marks tip template must proportional root template two fairly easy ways First best using pair dividers can di vide distance starting TE same number equal spaces root appropriate number spacing can divided half correspond root template can get close same results using right combination scales engineers architects scales spaces should numbered consecutively should identically marked numbered side Label top template both sides Hold templates together proper relative position cut right wing panel label outsides right Now hold together proper rel ative position left panel label outside left Next select finishing nails6 8 penny 2 2 longto hold templates foam Drill three holes nails fit snugly shown Fig 2 plan make several sets same wing make positioning jigs align templates attaching foam can made same plywood airfoil templates chord line root template should parallel base jig marks made jig align chord line Mark outline template jig blank cut opening slightly smaller template sand fit jig should position root template approx imately /8 e bottom foam chord line tip template should first drawn tip jig parallel base jig TE tip template should raised slightly about anel above chord line traced cutting jig pro vide washout Draw outline mark aligning marks chord line template jig blank complete root jig Note tapered wing will clearance top bottom both jigs should have chord 34 Model Aviation Fig 2 hot wire about enter toam Blank has Iabeied avoid mistakeslike making two right panels Airfoil template positioned help three nails 2 2-1/2 long call ing Out numbers bow moves helper can match speed end Fig 3 blank about cut length picture already has cut width thickness Jig should wide enough widest wing expect cut guides should absolutely perpendicular base Note hot wire resting against guides Fig 4 simple jig usea cut blank plan view outline last step before cutting core Smaller bow handy expect much cutting Guide rails interchangeable sizes Fig 5 Jig cutting foam blank top view outilne tuli-scaie paper template taped base jig align blank cutting lines same height Simple jigs should also made cut foam blocks blanks proper thickness length top view plan prior cutting core jig cutting length shown Fig 3 should wide enough widest wing expect cut cut ting guides should absolutely perpen dicular base jig cutting blank thickness shown Fig 4 should wide enough longest panel plan cut height cutting guide rails should approximately h deeper particular wing panel cross section cut foam blank set rails Holes just large enough provide very snug fit positioning dowels should drilled through base cutting guide rails dowels should removable order permit marking hole location additional guide rails other wing thicknesses later Guide rails should perfectly straight smooth assure smooth square blanks foam blank should cut top view plan top view outline wing before cut core Make full scale paper template top view plan wing order lay out cut foam blank jig cut plan form blank shown Fig 5 width should allow longest panel plan cut turned necessary angle case tapered wing end cutting guides should exactly perpendicular base full scale paper template wing plan can taped base jig align foam blank cutting guide strips tacked place position blocks foam should square intersecting surfaces block must cut square possible exception would ends block could angle fore aft [F TE ends should still vertical top bottom block Prior cutting core blanks should cut thickness length top view plan outline Cutting Core Once wing blank cut core can cut follows First label blank very soft pencil felt-tip marking pen LE Topfor leading edge top side wing RightFor right panel Label other blank LE Top Left sure correct edge labeled [F tapered wings match blanks position assembled wing make final check far too easy accidentally cut two left two right panels 2 Mark chord line block end did make alignment jigs Check sure same height end parallel bottom blank tapered wing use root template mark proper height chord line assure proper clearance top bottom 3 Align root template chord line chord line root blank align alignment jig sure TE template extends proper distance beyond TE foam Check sure side template right left corresponds label top blank top template up 4 Carefully push nails through holes template foam per pendicular side template 5 Align tip template chord line chord line scribed blank LE about above chord line blank TE. align tip template jig 6 Carefully push nails through holes template blank Re move positioning jigs used Cutting two-person job person caller will control speed cut call out numbers wire passes follower will keep end wire speed needed pass same numbers tip same instant called caller 7 The caller should know approx imate speed foam will melt cutting experience gained cutting blanks block cut too fast wire will lag cen ter wing will rough true copy template airfoil cut too slow foam will melted too much again surface will rough true copy good idea practice some scrap first correct temperature residue cutting will slowly burn off wire thin grey smoke 8 Position blank flat surface under suspended bow cutter Seats should provided either end two cutters preferably foam should about eye level ease control Weights should placed foam hold steady during cutting Three lb weights should 9 The caller will turn bow test temperature piece scrap after warms up caller will call template person will grasp end rod cutting bow little above hot wire bring wire top protruding TE template 10 The caller will call ready cut follower will respond ready steady comfortable I caller will call enter now wire contacts foam side follower will start cut tip end word now 12 caller calls numbers wire reaches mark follower matches speed passing same numbers same time 13 As caller approaches leading edge calls slow slows down enough let center wire catch up comes out foam straight wire caller says out comes out leading edge follower should come out almost same instant Once cut begun stop may slow down speed up Stopping will produce grooves Best results will come continuous cut Note authors recommend flat surface TE TE spar LE LE spar makes wing much stronger easier sheet will described detail next issue 14 Finally bring wire back re peat process cut bottom side core starting underneath TE template first core isnt per fect dont discouraged little practice Continued page 94 February 1978 35 Fig 6 dihedral angle cutting template can attached jig shown pflOtOgrapn see local hobby dealer WI~E almost Stahl design40 years ago t~p tTA OGA 4 lOBts famous 24 1/2 WWdGSPAN 0% FOR PACKING AND POSTAGE VA NESIDENTS ADD 4% TAX RUBBER & CO2 WINNER AT THE 50th NATS Blot 221/2 WINGSPMI $695 Kioud King Ambivalent Dennyplane Miss Arpiem Brigadeer articles skeleton photo 85% Power house photo accompanying months column Depending model size four spruce spars ranging located approximately 30% 70% chord perpendicular other Fulldepth plywood dihedral joiners placed slotting ribs hacksaw stacks appropriate thickness epoxied flush spars Shear webs 1/16 balsa added grain running vertical alternating front rear spars picture illustrates front spars should always webbed rear set may also webbed model stunted weight factor Additional strength can gained D tube sheeting leading edge ever seems add spanwise strength torsional rigidity has stated times bears repeating wing will no stronger rigid after covered heat-shrink material uncovered wing seems flexible uncovered absolutely should covered shiny stuff full set shear webs still doesnt cure flexibility get out silk pre pared pick up pieces Consider four-spar shear-web tech nique next old-timer Dr D B Mathews 506 South Walnut Greens burg KS 67054 Foam/Evans/Lester continued page 35 will take care problem mean time core isnt too bad ways salvage will discussed next issue Sectioning hot-wire method cut ting has limitation cuts must straight line Wings taper angle either LE TE must cut sections glued together Follow same procedure *108 Spo&te 28 WING8PAN S6 INE MODELS 2820 DORR AVE FAIRFAX VA 22030 Send free brochure section described cutting wing panel tip template inboard section also root template outboard section additional section requires additional template tip section also necessary cut very long wings sections due limitations tension necessary keep wire straight power uniform heating wire Dihedral Angle Cutting sim plest ways cutting dihedral angle two-piece wing raise tip prescribed height height can calcu lated angle given make vertical cut root panel can best done after cutting core core still blank can done before sheeting end-cutting jig after sheeting saw and/or sanding block endcutting jig can also done dihedral-angle cutting template angle-cutting tem plate can attached foam blank nails pressed foam can attached cutting jig see Fig 6 template angle half com plement total desired angle both sections must cut match cross sections joint example tendegree angle required template gle will 900 100/2 850 Regardless method should done systematically avoid cutting angle wrong end wrong direction two-panel wings right left sure top up cut root panel except gull wings cut angle outboard section polyhedral wing sure top up cut outer end tip inboard section root outboard section except gull wings same principles apply core cut complete right left panel sectioned polyhedral angle continued Prop Mod/Aycock continued page 31 exact eyeball part just make sure line both blades same OK now have big black line front prop will become high point wood work begins Select rather rough flat wood rasp starting high point work towards leading edge rasp being careful cut away leading edge just take down rather sharp leading edge satisfied same thing again high point towards trailing edge worrying about curved rounded surface just make flat per drawing B Repeat other blade Round off high point shown drawing tips will get quite thin will no way subtract props efficiency should have pile wood dust front now will make some Using 80-grit again hand sand blades rather smooth finish See said hard maple props work best have done respectable job put prop balancing tool should ball park After little practice will able get right money fact time will balanced closer came out box Finish sand blades 280 wet dry dry course done Notice did take anything off back prop blades Thus did alter basic pitch just added airfoil front finished prop should have quite sharp leading trailing edges Leave raw wood finish nothing please Try procedure prop size now using check engine performance airplane flying have found often can go high er pitch prop engine would lug before will turn now author ity Experiment various sizes pitches until get satisfies air remember prop rework can prove itself air ground tach have questions regard ing prop rework please feel free drop line care magazine will happy answer questions Helicopter/B itner continued page 37 altitude 20-60 meters stay within fly course start finish procedures must checked directing official Timing flight can done several ways will tell what method used four timers located south end four north end 94 Model Aviation
Edition: Model Aviation - 1978/02
Page Numbers: 32, 33, 34, 35, 94
LAST MONTHS installment cov ered foam material types foam chemical characteristics compatible sol vents glues etc month will cover construction safe use cut ting bows power supply techni ques cutting various types wing cores Next months installment concerns covering skinning use compat ible adhesives finishing Cutting Foam can easily equip yourself mas ter techniques cutting own foam cores following equipment required Cutting Bow like modelers handy tools can easily construct own bow required mate rials approximate costs follows 1 1 pc clear wood X 3 X 36 $150 22 pc 3/16 sic wire 75 32 pc 022 X 40 music wire 2 eye hooks10 52 2 alligator clips25 616 pc 16-gauge appliance cord90 715 pcsash cord20 8Masking electrical tape05 Total$300 following simple steps listed low can easily make bow evening 1 Lay out wood drilling holes a Using square make line side 1 edge b Using square make another line 1 end opposite 1 edge c Connect lines end 3 face diagonal line connects lines opposite edges d Mark center line 1 edges 2 Drill holes parallel diagonal line end a Drill pilot hole edge bit approximately least 2 keeping parallel diagonal line shown Fig 1 tricky part operation Drill slowly use too much pressure bit will tend walk grain wood Back drill out often sure drilling parallel diagonal line also keeping hole centered walking out toward side b Unless have extra long bit must now turn wood over repeat other edge went well holes should meet can sight through hole c Repeat process other end 3 Notch two 3/16 pieces music wire Clamp 3/16 X 9 pieces music wire vise file notch approximately /s should deep enough keep cutting wire slipping off should also smooth avoid nicking cutting wire otherwise likely break under tension heated 4 Install two 3/16 pieces music wire a Insert unnotched end 3/16 music wire hole nearest end wood sure notch facing out b Drive music wire through hole until approximately i/i protrud ing other side 5 Install eye hooks a Mark line top 6 end b Drill 1/16 hole center line approximately deep c Screw eye hooks hole 6 Attach sash cord a Tie knot center 5 piece sash cord leaving about 2 loop b Insert ends through eye hooks tie equal distance center knot 7 Attach power cord a Split 16-gauge 2-wire con ducter back about 24 end b Strip ends back about tach 2 alligator clips d Hook alligator clips cutting wire Note have power source adjustable through de sired range attach alligator clips protruding tops posts e Tape wires wood f Attach piece twine power cord loop sash cord needed hold power cord iques second article series covers making safe use cutting bows power supply techniques cutting various types wing cores U Bill Evans Max Lester clear work cutting 8 Attach cutting wire a Wrap cutting wire two turns around top long end 3/16 music wire next wood wrap turn around cutting wire another turn around 3/16 rod three turns around cutting wire cut off excess b Stretch tight repeat other end c Slide cutting wire down notch should now have proper tension 9 Your bow now ready attach cord running through two pulleys counterweight just balances other end pulley should directly above cutting will done other no will run have move get tools parts etc Add subtract weights until cutter remains whatever height left Make sure no binding moves up down smoothly light pull push 32 Model Aviation ivielung e cm wiin TflS DOW oescrioea Text mnis case jigs being used guide cutting wire bow suspended pulleys counterbalanced easy handling 10 If working kitchen someplace better-half wont stand still hooking pulleys ceiling just dont like approach skip steps 5 6 9 Before decide reason system hot wire needs kept away thing might damaged cutting cores Also bow needs easy control mini mum muscular effort make smooth cuts other good bow designs simple works well easy build use no ad justments cutting wire eventually stretches breaks sim ple inexpensive replace Power Source next piece equip ment required power source right wattage Volts X amps equals watts both AC DC However AC complicated measure 1/100 second intervals can measured peak root mean square Also line voltage sometimes varies tween 105 125 volts residential service bow described above requires ap proximately 70 80 watts Some alternative power sources 1 Stepped transformers similar ones used toy trains will work can find puts out enough amps HO too small good heavy duty larger trains like Lionel may overheat operate 10 15 minutes time 2 A continuously variable step-down transformer fairly expensive give precise control regulating tem perature wire also have range provide power hot-wire cutter making cut outs retractable land ing gear control rods etc can dangerous unless output voltage can limited around 24V can used regulate battery charger 3 A rheostat proper output will also current regulating job recommended final output however rheostat controls amps rather volts would safe rheostat can used vary input battery charger fixed output trans former 4 An automobile battery charger 8-amps output will job need some means adjusting output desirable power source 5 An automobile battery has used successfully again ingenuity re quired get right heat Electronics stores mail order houses good sources power supplies also electronic surplus stores salesman have little electronics knowl edge need some combination variable power provides approxi mately 70 watts better keep output voltage around 24 volts less sake safety example Volts s 24 volts X 3 amps atts recommended therefore use direct 110 volts cutting bow Mike Gaishin modeler engineer Heathkit suggested simple inexpensive way regulate output battery battery charger Make resistor length piano wire can wound heavy coke bottle strung like another cutting bow etc Attach lead output terminal battery charger end piano wire Put alligator clips both ends lead attach end 3/16 rod end cutting bow other resistor various distances until right wire temperature reached cutting bow lead other out put terminal battery charger would course attached 3/16 rod other end cutting bow Template Construction Two templates needed root rib tip rib wings See sectioning addi tional templates required wing made sections practical template material /s 1/16 aircraft plywood easy work readily available relatively expensive Literally dozens cores can February 1978 33 Foam wings various stages construction Reading up bot tom foam slab foam blank slab cut plan viewl foam core balsa leading trailing edges glued place foam core sheeted balsa completed wing after being covered Solarfilm bit tricky drilling holes wood bow lines located described care taken holes drilled opposite edges will meet middle course long drill help cut plywood template little reason go 1/16 formica 20-gauge aluminum durability harder work first step decide thick ness material used sheet ing Trace ribs kit plans allowing difference thick ness sheeting material Locate chord line draw LE TE both sides template Cut little outside outline sand carefully line using very fine sand paper finishing 280 wet-or-dry used dry good vibrating sander block hand sander should used insure no dips bumps hot wire will faithfully reproduce irregularities dont hesitate throw away template isnt perfect template will held place nails pushed through holes templates foam Next cutting speed marks must laid out template Cutting two per son job person will set pace call ing out numbers marks other will maintain same relative po sition matching numbers end marks should about t equally spaced TE chord line LE top bottom Number marks consecutively starting #1 first mark nearest LE tapered wings marks tip template must proportional root template two fairly easy ways First best using pair dividers can di vide distance starting TE same number equal spaces root appropriate number spacing can divided half correspond root template can get close same results using right combination scales engineers architects scales spaces should numbered consecutively should identically marked numbered side Label top template both sides Hold templates together proper relative position cut right wing panel label outsides right Now hold together proper rel ative position left panel label outside left Next select finishing nails6 8 penny 2 2 longto hold templates foam Drill three holes nails fit snugly shown Fig 2 plan make several sets same wing make positioning jigs align templates attaching foam can made same plywood airfoil templates chord line root template should parallel base jig marks made jig align chord line Mark outline template jig blank cut opening slightly smaller template sand fit jig should position root template approx imately /8 e bottom foam chord line tip template should first drawn tip jig parallel base jig TE tip template should raised slightly about anel above chord line traced cutting jig pro vide washout Draw outline mark aligning marks chord line template jig blank complete root jig Note tapered wing will clearance top bottom both jigs should have chord 34 Model Aviation Fig 2 hot wire about enter toam Blank has Iabeied avoid mistakeslike making two right panels Airfoil template positioned help three nails 2 2-1/2 long call ing Out numbers bow moves helper can match speed end Fig 3 blank about cut length picture already has cut width thickness Jig should wide enough widest wing expect cut guides should absolutely perpendicular base Note hot wire resting against guides Fig 4 simple jig usea cut blank plan view outline last step before cutting core Smaller bow handy expect much cutting Guide rails interchangeable sizes Fig 5 Jig cutting foam blank top view outilne tuli-scaie paper template taped base jig align blank cutting lines same height Simple jigs should also made cut foam blocks blanks proper thickness length top view plan prior cutting core jig cutting length shown Fig 3 should wide enough widest wing expect cut cut ting guides should absolutely perpen dicular base jig cutting blank thickness shown Fig 4 should wide enough longest panel plan cut height cutting guide rails should approximately h deeper particular wing panel cross section cut foam blank set rails Holes just large enough provide very snug fit positioning dowels should drilled through base cutting guide rails dowels should removable order permit marking hole location additional guide rails other wing thicknesses later Guide rails should perfectly straight smooth assure smooth square blanks foam blank should cut top view plan top view outline wing before cut core Make full scale paper template top view plan wing order lay out cut foam blank jig cut plan form blank shown Fig 5 width should allow longest panel plan cut turned necessary angle case tapered wing end cutting guides should exactly perpendicular base full scale paper template wing plan can taped base jig align foam blank cutting guide strips tacked place position blocks foam should square intersecting surfaces block must cut square possible exception would ends block could angle fore aft [F TE ends should still vertical top bottom block Prior cutting core blanks should cut thickness length top view plan outline Cutting Core Once wing blank cut core can cut follows First label blank very soft pencil felt-tip marking pen LE Topfor leading edge top side wing RightFor right panel Label other blank LE Top Left sure correct edge labeled [F tapered wings match blanks position assembled wing make final check far too easy accidentally cut two left two right panels 2 Mark chord line block end did make alignment jigs Check sure same height end parallel bottom blank tapered wing use root template mark proper height chord line assure proper clearance top bottom 3 Align root template chord line chord line root blank align alignment jig sure TE template extends proper distance beyond TE foam Check sure side template right left corresponds label top blank top template up 4 Carefully push nails through holes template foam per pendicular side template 5 Align tip template chord line chord line scribed blank LE about above chord line blank TE. align tip template jig 6 Carefully push nails through holes template blank Re move positioning jigs used Cutting two-person job person caller will control speed cut call out numbers wire passes follower will keep end wire speed needed pass same numbers tip same instant called caller 7 The caller should know approx imate speed foam will melt cutting experience gained cutting blanks block cut too fast wire will lag cen ter wing will rough true copy template airfoil cut too slow foam will melted too much again surface will rough true copy good idea practice some scrap first correct temperature residue cutting will slowly burn off wire thin grey smoke 8 Position blank flat surface under suspended bow cutter Seats should provided either end two cutters preferably foam should about eye level ease control Weights should placed foam hold steady during cutting Three lb weights should 9 The caller will turn bow test temperature piece scrap after warms up caller will call template person will grasp end rod cutting bow little above hot wire bring wire top protruding TE template 10 The caller will call ready cut follower will respond ready steady comfortable I caller will call enter now wire contacts foam side follower will start cut tip end word now 12 caller calls numbers wire reaches mark follower matches speed passing same numbers same time 13 As caller approaches leading edge calls slow slows down enough let center wire catch up comes out foam straight wire caller says out comes out leading edge follower should come out almost same instant Once cut begun stop may slow down speed up Stopping will produce grooves Best results will come continuous cut Note authors recommend flat surface TE TE spar LE LE spar makes wing much stronger easier sheet will described detail next issue 14 Finally bring wire back re peat process cut bottom side core starting underneath TE template first core isnt per fect dont discouraged little practice Continued page 94 February 1978 35 Fig 6 dihedral angle cutting template can attached jig shown pflOtOgrapn see local hobby dealer WI~E almost Stahl design40 years ago t~p tTA OGA 4 lOBts famous 24 1/2 WWdGSPAN 0% FOR PACKING AND POSTAGE VA NESIDENTS ADD 4% TAX RUBBER & CO2 WINNER AT THE 50th NATS Blot 221/2 WINGSPMI $695 Kioud King Ambivalent Dennyplane Miss Arpiem Brigadeer articles skeleton photo 85% Power house photo accompanying months column Depending model size four spruce spars ranging located approximately 30% 70% chord perpendicular other Fulldepth plywood dihedral joiners placed slotting ribs hacksaw stacks appropriate thickness epoxied flush spars Shear webs 1/16 balsa added grain running vertical alternating front rear spars picture illustrates front spars should always webbed rear set may also webbed model stunted weight factor Additional strength can gained D tube sheeting leading edge ever seems add spanwise strength torsional rigidity has stated times bears repeating wing will no stronger rigid after covered heat-shrink material uncovered wing seems flexible uncovered absolutely should covered shiny stuff full set shear webs still doesnt cure flexibility get out silk pre pared pick up pieces Consider four-spar shear-web tech nique next old-timer Dr D B Mathews 506 South Walnut Greens burg KS 67054 Foam/Evans/Lester continued page 35 will take care problem mean time core isnt too bad ways salvage will discussed next issue Sectioning hot-wire method cut ting has limitation cuts must straight line Wings taper angle either LE TE must cut sections glued together Follow same procedure *108 Spo&te 28 WING8PAN S6 INE MODELS 2820 DORR AVE FAIRFAX VA 22030 Send free brochure section described cutting wing panel tip template inboard section also root template outboard section additional section requires additional template tip section also necessary cut very long wings sections due limitations tension necessary keep wire straight power uniform heating wire Dihedral Angle Cutting sim plest ways cutting dihedral angle two-piece wing raise tip prescribed height height can calcu lated angle given make vertical cut root panel can best done after cutting core core still blank can done before sheeting end-cutting jig after sheeting saw and/or sanding block endcutting jig can also done dihedral-angle cutting template angle-cutting tem plate can attached foam blank nails pressed foam can attached cutting jig see Fig 6 template angle half com plement total desired angle both sections must cut match cross sections joint example tendegree angle required template gle will 900 100/2 850 Regardless method should done systematically avoid cutting angle wrong end wrong direction two-panel wings right left sure top up cut root panel except gull wings cut angle outboard section polyhedral wing sure top up cut outer end tip inboard section root outboard section except gull wings same principles apply core cut complete right left panel sectioned polyhedral angle continued Prop Mod/Aycock continued page 31 exact eyeball part just make sure line both blades same OK now have big black line front prop will become high point wood work begins Select rather rough flat wood rasp starting high point work towards leading edge rasp being careful cut away leading edge just take down rather sharp leading edge satisfied same thing again high point towards trailing edge worrying about curved rounded surface just make flat per drawing B Repeat other blade Round off high point shown drawing tips will get quite thin will no way subtract props efficiency should have pile wood dust front now will make some Using 80-grit again hand sand blades rather smooth finish See said hard maple props work best have done respectable job put prop balancing tool should ball park After little practice will able get right money fact time will balanced closer came out box Finish sand blades 280 wet dry dry course done Notice did take anything off back prop blades Thus did alter basic pitch just added airfoil front finished prop should have quite sharp leading trailing edges Leave raw wood finish nothing please Try procedure prop size now using check engine performance airplane flying have found often can go high er pitch prop engine would lug before will turn now author ity Experiment various sizes pitches until get satisfies air remember prop rework can prove itself air ground tach have questions regard ing prop rework please feel free drop line care magazine will happy answer questions Helicopter/B itner continued page 37 altitude 20-60 meters stay within fly course start finish procedures must checked directing official Timing flight can done several ways will tell what method used four timers located south end four north end 94 Model Aviation