Project Sea Dart

In Part 1 development ultimate demise Convair Sea Dart traced along some construction notes pertaining magnificent model Part 2 month concludes further description construction techniques discussion models first test flights evaluations modifications reevalua tions EJames Gilgenbach PART ONE Project Sea Dart June 1989 Model Aviation discussed develop ment ultimate demise Convair Sea Dart along some basic construc tion materials-handling techniques used designing building A-scale mod el Wing main spar detachable wing extends pocket fuselage Above completed Sea Dart afloat ready go scale wings wing loading 332 ozIsq ft aircraft has able take off water relatively high loading will however take off grass requires about 300 ft lift off Left Sea Dart shown after being covered 5-oz/sq-yd fiberglass woven cloth Safe-T-Poxy fiberglass Safe-T-Poxy together weighed 68 oz Right cutouts bottom fuselage housing retracted skis skis shown however retractable 56 Model Aviation Left Ready finishing model suspended ceiling two wires order allow full access painting primer added 11 oz weight fuselage 147 oz overall weight airplane far anticipated Right Dynamax fan unit OS 77 engine installed fuse lage system secured its cradle two steel straps insulated fuselage silicone rubber under straps Left The protrusion seen close-up wing tip simulates elevon control horn linkage housing full-scale Sea Dart Right Kevlar exhaust duct installed ultralight formers positioned around formers will support % balsa outer skin Left The servo compartment seen located directly under scale cockpit Access gained flipping up scale cockpit hatch Car bon fiber pushrods 1As Aerospace Composite Products Irvine CA used control elevons rudder Right Details front rear ski struts rear strut outer tube constructed 17- ozIsq-yd Kevlar mat inner strut -in-OD alu minum tubing front strut outer tube made Dave Brown fiberglass pushrod inner strut cut /4-in aluminum rod carries lifting load made laminating 014-thick unidirec tional carbon fiber laminate between two pieces 1A6 plywood capping edges assembly 014-thick %-in-wide carbon fiber laminate Zap-AGap Sb Zap works best gluing carbon fiber carbon fiber should sanded smooth side ensure good bond Balsa caps placed between ribs top main spar sanded match wing contour wing skin sheeting made laminating 25-ozIsq-yd Kevlar mat A2 contest balsa sheeting Heres best method Ive found Using straightedge trim edges A2 balsa tape balsa sheets gether Scotch Magic Transparent type tape full length joint Cover work surface waxed paper freezer wrap place balsa sheet ing tape side down top Lay Kevlar mat over balsa spread Safe T-Poxy thinned 50% denatured alco hol over Kevlar printers roller squeegee Safe T-Poxy evenly over Kevlar balsa careful roll up Kevlar onto roller Place waxed paper over Kevlar Put large sheet glass over waxed pa per weight down 24 hours Remove scotch tape flat sand seams now have strong wing skin weighs mere 0035 oz/sq waterproofed inside Safe-T Poxy Kevlar rear spar made laminating 014 x -in unidirectional carbon fiber laminate strip Y32 x A-in balsa stick Make up two strips top bot tom glue A-in-sq balsa stick carbon fiber between 9A2-dia aluminum tube also glued tween two strips accepts A-in dia carbon fiber wing rod attachment fuselage aluminum tube boxed sides 014 carbon fiber balsa Make trailing edge gluing 007 x /2-in unidirectional carbon fiber laminate onto /32 x -in balsa strip makes light strong trailing edge can sanded sharp contour Landing gear strut Very light sturdy outer strut tubes can made wrapping August 1989 57 1 7-oz/sq-yd woven Keviar thoroughly wetted Safe-T-Poxv around inner strut leg has wrapped waxed paper dozen revolutions Keviar around inner tube sufficient Wrapping waxed paper around outside assembly ensures roundness min imizes final sanding landing gear areas wing rod tubes fuselage reinforced cut ting appropriate size piece 1 7-oz Kevlar soaking Safe-T-Poxy working place Pushrods Aerospace Composite Products Irvine CA supplies A6-dia carbon fiber rod works great pushrods run through inside yellow ner Gold-N-Rod straight shot servo control horn necessary rod cant bent very much Gold-N-Rod must glued formers avoid flexing pushrod assembly attach Kwik Link rough up end A6-dia car bon fiber rod clean Kwik Link de natured alcohol apply Zap-A-Gap onto rod end slide Kwik Link over dry wrap carbon fiber ribbon around rod Kwik Link Zap place threaded end can attached same way However want make de tachable first file notch tube por tion threaded end slide rod Put wheel collar over end using socket head cap screw collar rather setscrew comes clamp rod through notch cap screw smooth end wont cut through carbon fibers Intake exhaust ducts After making intake exhaust ducts balsa plywood Styrofoam cut out pieces 1 7-oz Kevlar match Cover struc ture inside out Keviar just would using fiberglass Brush Hob bypoxy 2 mixed 50/50 microballoons thoroughly soaking through Kevlar Kevlar doesnt sand well sure keep ends edges flat possible covered epoxy mix Sand smooth possible dry apply other coat mix Repeat procedure until have completely smooth surface Formers load-bearing formers support landing gear engine cradle made laminating 1 7-oz woven Kevlar outside A-in Lite Ply laminating / plywood both sides assembly using Safe-T-Poxy After lamina tion entire assembly weighted down 24 hours remaining formers non-load bearing made laminating / ply wood both sides %2-in balsa using Sb Zap stiffen up thin cross sections Zap flowed edges Lightening holes cut wherever possible Finishing Prepare model filling dings sanding wings fuse lage 220-grit paper Cut piece 05oz/sq-yd woven fiberglass cloth some what larger area covered Mix up appropriate amount Safe-T Poxy diluted 25% denatured alcohol Drape cloth over area covered pour Safe-T-Poxy mix thin line along its length Using old playing card work mixture through cloth onto wood cloth well saturated keep working mixture until ex cess epoxy has removed returned container continuous process wetting working mixture efficiently removes excess epoxy very easy learn can accomplished about 10 min utes per wing careful though let excess epoxy drip run onto under side surfaces secret remove surplus before dries After epoxy has set up remove excess material sharp blade scrape high spots edge single-edged razor blade fol lowing day Usually sanding epoxy needs just good measure Left scale skis planked cut out luilt right fuselage framework seen photo Note carbon fiber rein forcement strips ski Right photo shows entire ski still place inside fuselage frame razor saw used remove ski Most %z x king strips cut %2 x 3 x 36 contest balsa sheets because unavailability contest grade balsa strip 58 Model Aviation cockpit hatch frame built seen pianked %2 contest grade balsa ensure minimum weight hatch itself cut out after planking complete rear exhaust tube Construction combination plywood Styrofoam sanded shape covered 1 7-ozIsq-yd Keviar mat Hobbypoxy Ii mixed 50/50 ratio microbailoons Len steel squaring blocks used hold down wing structure building board trailing edge made gluing 007 x 1A-in unidirectional laminate onto %2 x V balsa strip Right support wings near trailing edge %2-in-OD aluminum tubing glassed former -in.dia carbon fiber wing rods inserted Aluminum tubing %2-in OD also glued Inside rear spar lightly dust entire structure 220grit paper next step fill weave used K&B primer regretted added weight After sanding down primer point just filling weave add other coat sand down until can just begin see through Youre now ready spray finish coat K&B ep oxy paint used mixed scale effect follows 33% color 20% satin catalyst 13% gloss catalyst 34% thinner combination will produce semigloss finish Weight control goal build aircraft light possible sacrific ing structural integrity some what rough flying techniques demand before construction began 383 lb hardware couldnt anything about follows Engine fan unit assembly 440 oz Radio four servos 113 oz Fuel tanks two 6 oz 12 oz 60 oz Total 613 oz 383 lb fuselage weight including hatches Before fiberglass covering 56 oz After fiberglass covering 61 oz After priming 72 oz After finish painting 76 oz scale wings weighed Before fiberglass covering 152 oz After fiberglass covering 170 oz After priming 200 oz After painting 214 oz oversize wings weighed Before fiberglass covering 300 oz After fiberglass covering 333 oz After priming 440 oz After painting 470 oz skis ski hardware weighed Before priming 175 oz After priming 182 oz After painting 185 oz Analyzing total weight aircraft scale wings different stages construction indicated biggest weight gain due covering finish painting primer percentage increases Initial total weight before covering 150 oz Total weight after covering 157 oz 47% Total weight after priming 172 oz 96% Total weight after painting 178 oz 35% absolute terms weight addition covering 7 oz primer added 15 oz paint added 6 oz overall gain 28 oz after finishing com pleted original calculations never envisioned increase magnitude guess problems striving contest-winning finish probably could have decreased weight 8 oz hadnt fussy Also aircraft other seaplane would have used Super MonoKote decreasing weight least 16 oz wing loading taken 75% wing area final weight wing load ing scale wings 111 lb 332 oz/sq ft respectively over size wings 127 lb 243 oz/sq ft re spectively Though hadnt attained goal 10 lb scale wings surely beautiful finish could Left engine fan unit seen installed temporarily fitting formers shown clamped place will become joint two access hatches meet entire model built inside out Right Once intake hatch fitted entire assembly can planked thin coat Safe-T-Poxy first applied Styrofoam aliowed cure Planking could Zapped Styrofoam August 1989 59 THE LEADER IN COMPETITION PROPELLERS 4 CYCLE SERIES 100 THP DESIGN TAILORED HELICAL PITCH DEVELOPED TO GIVE MAXIMUM THRUST AT 4 CYCLE ENGINE RPM ALL THE LATEST TECHNIQUES USED ON OUR PRO SERIES 3 SEE BELOW DIA PITCH THP PRICE 1266A77A8 136778 14677/8 1567 16678 PRO SERIES 3 NEW HIGH TECH AIRFOIL SECTION lOTO 200/0 INCREASE IN THRUST MFG OF SELECT HARD MAPLE WOOD WILL NOT FATIGUE LIKE SYNTHETICS FUEL PROOF HIGH LUSTER FINISH DIAPITCH PRICE 5S/34 634 72833/456 8334568 84566/7 94566A77A 104566A7 108W8W 10BEW 114677/778 11SW 11BEW 1187 124W 125W 1256 1356 1456 1556 164N 16678 test fly aircraft see what would hap pen Testing Engine fan first test deter well engine fan unit would perform aircraft two con cerns worried engine might properly draw fuel lower two tanks located below fan unit did want use pump also thought fan mounting method might cause excessive vibration quickly discovered engine much compression especially lit tle oil cylinder standard elec tric starter wouldnt turn over loos ened up glow plug slightly release compression cranked engine over electric starter Just feared engine didnt draw enough fuel start priming through fuel inlet line started almost immediately Once oil burned out en gine warmed up slightly stopped tightened plug Though engine would now turn over starter still wouldnt draw enough fuel restart primed again just before started immediately Obviously Id have design better way prime engine After engine reasonably warmed up gave full throttle adjusted highspeed needle valve peak rpm rich ened out about two clicks 05 77 OS No 8 plug turning Dynamax fan 21000 rpm vibra tion level within tolerance Holding plane different attitudes no effect engine run idle flawless Unlike first portion testing unequivocal success Water test first water taxiing tests re vealed two unexpected problems First scale wings model sat much higher water full-size air craft causing tip side im merse wing tip resulted poor taxiing characteristics Second water somehow getting fuselage Further analysis showed entering through hatch seams solve first problem built scale rockets mounted onto wing tips act pontoons stop leaks sealed hatch seams silicone sealer using Liquid Masking release agent hatches second water taxiing test very successful combination water rud der exhaust deflector connected air rudder model turned water command High-speed water taxiing test mo ment truth quickly approaching couldnt resist giving model full throt tle see what would happen amaze ment Sea Dart lifted gracefully out water onto its skis went on-plane still picking up speed As airplane reached what considered reasonable takeoff speed introduced about 50% up eleva tor Nothing happened tried full up eleva tor still nothing happened model oblivious commands continued skim ming across water like hydroplane sudden swerve drastically changed course flipped unceremoni ously onto shore Investigation showed two front ski struts broken right wing smashed end Apparently hit stump sticking slightly out water week later after implementing repairs moving radio battery pack nose tail ready resume test ing Feeling very close suc cess several friends 35mm video cameras hand record mo mentous occasion taxied model out well away th stumps aimed wind gave itfidl throttle rose up skis very quickly tail still dragged waterand didnt respond full down elevator lifting After dozen valiant attempts get on-plane air finally conceded defeat called day Flying test weather turning colder could no longer persuade daughter place retrieve Sea Dart water resorted putting land ing gear under skis attempting take off land cold windy Thursday evening Fond du Lac Miniature Aircraft Associa tion FMAA members gathered local flying field monthly fly-in meet ing plenty helpers fired up taxied Sea Dart position Heading model directly wind gave full throtfie quickly jumped air hold full up elevator just stay aloftan unexpected predicament threw verge panic Should abort will land Will continue fly Ultimately consistent scream ing sound OS 77 positive feel Futaba PCM gave confidence continue model now gaining altitude full up elevator Nursing upwind far could see slowly started gentle lefthand turnand airplane maintained alti tude assistant Gus Rebens burg able give full up trim held full up elevator model began gaining altitude command leveled off approximately 200 ft altitude ana lyzed airplanes flight characteristics idiosyncrasies Knowing deadstick landing would probably disastrous given amount up elevator required maintain level flight decided attempt first landing Gus assistance set up landing backed off throttle ap proximately one-third watched Dart settle almost picture-perfect return Earth Having concluded first flight model still nose-heavy recal culated center-of-gravity added 6 oz weight tail accom 60 Model Aviation NEW NEW RO PYLON RACING SERIES 500 DIAPITCHPRICE 7SN 5/N SERIES 400C 86677/7 9777 W WIDE BLADE EW EXTRA WIDE IU IUARRAW pushed felt secure enough reliabil ity OS 77 engine Dynamax fan Futaba PCM radio next test flight Brillion Fun-Fly light breeze Brillions relatively small field Im sure quite few bets placed whether Id get Dart airborneor end up swamp grass asked Bob Johnson friend vice president FMAA videotape flight first takeoff attempt Sea Dart heading toward pits aborted After realigning takeoff direction again applied full throttle Dart trav eled about 300 ft edge field before lifting off As lofted over marsh wings rocked ominously seemed close faltering moment could picture Sea Dart mock ingly rechristened Swamp Dart sink ing notoriety among other models-thatdidnt-quite-make-it forever after butt ridicule However again full up elevator Dart straightened began slowly gaining altitude Once shed attained full speed slight amount up trim neces sary airplane still sluggish lacked good vertical performance open ski wells skis extra landing gear wheels seemed acting giant air brakes least consolation knowing modifications full-size Dart too must have made flights unretracted skis re tarded speed landing uneventful pull back one-third throttle flare As test results make clear Ill need introduce several modifications con duct additional tests order optimize Sea Darts performance plan imple menting testing changes fol lows Modification Install larger wings Tests Attempt takeoff snow b Attempt takeoff water Modification Remove skis cover ski wells add wheels Tests Attempt takeoff grass scale large wings b Analyze highspeed performance scale large wings test results positive model gains hoped-for agility intend add retractable skis Perhaps fitting Scale edition Convair Sea Dart still transition full-size sea plane itself halted experimental stage Navy ran short funding rate especially retractable hydroskis Sea Dart model promises meld authenticity best performance attainable Thats going keep busy some time DWBRO TRIP SPIN KEEPS YOU IN Quick easy assemble Universal Designed balance items listed above special accessories Strong stable durable balancing wheels recessed prevent damage accidently dropped Du-Bros Tm- Spin prop balancer adjustable vertically horizontally conform balancing need Truly precision instrument built modelers expect very best Available now local hobby shop DU-BRO PRODUCTS INC BALANCES AIRPLANE PROPSALL SIZES JET FANS BOAT PROPS HELICOPTER ROTOR HEADS SPINNERS CAR WHEELS AND MOTOR GEARS 480 Bonner Road onda IL 60084 August 1989 61 BALANCE Specially designed locking cone securely centers locks props onto balancing shaft utmost accuracy -a responding advertisers mention read about Model Aviation

In Part 1 development ultimate demise Convair Sea Dart traced along some construction notes pertaining magnificent model Part 2 month concludes further description construction techniques discussion models first test flights evaluations modifications reevalua tions EJames Gilgenbach PART ONE Project Sea Dart June 1989 Model Aviation discussed develop ment ultimate demise Convair Sea Dart along some basic construc tion materials-handling techniques used designing building A-scale mod el Wing main spar detachable wing extends pocket fuselage Above completed Sea Dart afloat ready go scale wings wing loading 332 ozIsq ft aircraft has able take off water relatively high loading will however take off grass requires about 300 ft lift off Left Sea Dart shown after being covered 5-oz/sq-yd fiberglass woven cloth Safe-T-Poxy fiberglass Safe-T-Poxy together weighed 68 oz Right cutouts bottom fuselage housing retracted skis skis shown however retractable 56 Model Aviation Left Ready finishing model suspended ceiling two wires order allow full access painting primer added 11 oz weight fuselage 147 oz overall weight airplane far anticipated Right Dynamax fan unit OS 77 engine installed fuse lage system secured its cradle two steel straps insulated fuselage silicone rubber under straps Left The protrusion seen close-up wing tip simulates elevon control horn linkage housing full-scale Sea Dart Right Kevlar exhaust duct installed ultralight formers positioned around formers will support % balsa outer skin Left The servo compartment seen located directly under scale cockpit Access gained flipping up scale cockpit hatch Car bon fiber pushrods 1As Aerospace Composite Products Irvine CA used control elevons rudder Right Details front rear ski struts rear strut outer tube constructed 17- ozIsq-yd Kevlar mat inner strut -in-OD alu minum tubing front strut outer tube made Dave Brown fiberglass pushrod inner strut cut /4-in aluminum rod carries lifting load made laminating 014-thick unidirec tional carbon fiber laminate between two pieces 1A6 plywood capping edges assembly 014-thick %-in-wide carbon fiber laminate Zap-AGap Sb Zap works best gluing carbon fiber carbon fiber should sanded smooth side ensure good bond Balsa caps placed between ribs top main spar sanded match wing contour wing skin sheeting made laminating 25-ozIsq-yd Kevlar mat A2 contest balsa sheeting Heres best method Ive found Using straightedge trim edges A2 balsa tape balsa sheets gether Scotch Magic Transparent type tape full length joint Cover work surface waxed paper freezer wrap place balsa sheet ing tape side down top Lay Kevlar mat over balsa spread Safe T-Poxy thinned 50% denatured alco hol over Kevlar printers roller squeegee Safe T-Poxy evenly over Kevlar balsa careful roll up Kevlar onto roller Place waxed paper over Kevlar Put large sheet glass over waxed pa per weight down 24 hours Remove scotch tape flat sand seams now have strong wing skin weighs mere 0035 oz/sq waterproofed inside Safe-T Poxy Kevlar rear spar made laminating 014 x -in unidirectional carbon fiber laminate strip Y32 x A-in balsa stick Make up two strips top bot tom glue A-in-sq balsa stick carbon fiber between 9A2-dia aluminum tube also glued tween two strips accepts A-in dia carbon fiber wing rod attachment fuselage aluminum tube boxed sides 014 carbon fiber balsa Make trailing edge gluing 007 x /2-in unidirectional carbon fiber laminate onto /32 x -in balsa strip makes light strong trailing edge can sanded sharp contour Landing gear strut Very light sturdy outer strut tubes can made wrapping August 1989 57 1 7-oz/sq-yd woven Keviar thoroughly wetted Safe-T-Poxv around inner strut leg has wrapped waxed paper dozen revolutions Keviar around inner tube sufficient Wrapping waxed paper around outside assembly ensures roundness min imizes final sanding landing gear areas wing rod tubes fuselage reinforced cut ting appropriate size piece 1 7-oz Kevlar soaking Safe-T-Poxy working place Pushrods Aerospace Composite Products Irvine CA supplies A6-dia carbon fiber rod works great pushrods run through inside yellow ner Gold-N-Rod straight shot servo control horn necessary rod cant bent very much Gold-N-Rod must glued formers avoid flexing pushrod assembly attach Kwik Link rough up end A6-dia car bon fiber rod clean Kwik Link de natured alcohol apply Zap-A-Gap onto rod end slide Kwik Link over dry wrap carbon fiber ribbon around rod Kwik Link Zap place threaded end can attached same way However want make de tachable first file notch tube por tion threaded end slide rod Put wheel collar over end using socket head cap screw collar rather setscrew comes clamp rod through notch cap screw smooth end wont cut through carbon fibers Intake exhaust ducts After making intake exhaust ducts balsa plywood Styrofoam cut out pieces 1 7-oz Kevlar match Cover struc ture inside out Keviar just would using fiberglass Brush Hob bypoxy 2 mixed 50/50 microballoons thoroughly soaking through Kevlar Kevlar doesnt sand well sure keep ends edges flat possible covered epoxy mix Sand smooth possible dry apply other coat mix Repeat procedure until have completely smooth surface Formers load-bearing formers support landing gear engine cradle made laminating 1 7-oz woven Kevlar outside A-in Lite Ply laminating / plywood both sides assembly using Safe-T-Poxy After lamina tion entire assembly weighted down 24 hours remaining formers non-load bearing made laminating / ply wood both sides %2-in balsa using Sb Zap stiffen up thin cross sections Zap flowed edges Lightening holes cut wherever possible Finishing Prepare model filling dings sanding wings fuse lage 220-grit paper Cut piece 05oz/sq-yd woven fiberglass cloth some what larger area covered Mix up appropriate amount Safe-T Poxy diluted 25% denatured alcohol Drape cloth over area covered pour Safe-T-Poxy mix thin line along its length Using old playing card work mixture through cloth onto wood cloth well saturated keep working mixture until ex cess epoxy has removed returned container continuous process wetting working mixture efficiently removes excess epoxy very easy learn can accomplished about 10 min utes per wing careful though let excess epoxy drip run onto under side surfaces secret remove surplus before dries After epoxy has set up remove excess material sharp blade scrape high spots edge single-edged razor blade fol lowing day Usually sanding epoxy needs just good measure Left scale skis planked cut out luilt right fuselage framework seen photo Note carbon fiber rein forcement strips ski Right photo shows entire ski still place inside fuselage frame razor saw used remove ski Most %z x king strips cut %2 x 3 x 36 contest balsa sheets because unavailability contest grade balsa strip 58 Model Aviation cockpit hatch frame built seen pianked %2 contest grade balsa ensure minimum weight hatch itself cut out after planking complete rear exhaust tube Construction combination plywood Styrofoam sanded shape covered 1 7-ozIsq-yd Keviar mat Hobbypoxy Ii mixed 50/50 ratio microbailoons Len steel squaring blocks used hold down wing structure building board trailing edge made gluing 007 x 1A-in unidirectional laminate onto %2 x V balsa strip Right support wings near trailing edge %2-in-OD aluminum tubing glassed former -in.dia carbon fiber wing rods inserted Aluminum tubing %2-in OD also glued Inside rear spar lightly dust entire structure 220grit paper next step fill weave used K&B primer regretted added weight After sanding down primer point just filling weave add other coat sand down until can just begin see through Youre now ready spray finish coat K&B ep oxy paint used mixed scale effect follows 33% color 20% satin catalyst 13% gloss catalyst 34% thinner combination will produce semigloss finish Weight control goal build aircraft light possible sacrific ing structural integrity some what rough flying techniques demand before construction began 383 lb hardware couldnt anything about follows Engine fan unit assembly 440 oz Radio four servos 113 oz Fuel tanks two 6 oz 12 oz 60 oz Total 613 oz 383 lb fuselage weight including hatches Before fiberglass covering 56 oz After fiberglass covering 61 oz After priming 72 oz After finish painting 76 oz scale wings weighed Before fiberglass covering 152 oz After fiberglass covering 170 oz After priming 200 oz After painting 214 oz oversize wings weighed Before fiberglass covering 300 oz After fiberglass covering 333 oz After priming 440 oz After painting 470 oz skis ski hardware weighed Before priming 175 oz After priming 182 oz After painting 185 oz Analyzing total weight aircraft scale wings different stages construction indicated biggest weight gain due covering finish painting primer percentage increases Initial total weight before covering 150 oz Total weight after covering 157 oz 47% Total weight after priming 172 oz 96% Total weight after painting 178 oz 35% absolute terms weight addition covering 7 oz primer added 15 oz paint added 6 oz overall gain 28 oz after finishing com pleted original calculations never envisioned increase magnitude guess problems striving contest-winning finish probably could have decreased weight 8 oz hadnt fussy Also aircraft other seaplane would have used Super MonoKote decreasing weight least 16 oz wing loading taken 75% wing area final weight wing load ing scale wings 111 lb 332 oz/sq ft respectively over size wings 127 lb 243 oz/sq ft re spectively Though hadnt attained goal 10 lb scale wings surely beautiful finish could Left engine fan unit seen installed temporarily fitting formers shown clamped place will become joint two access hatches meet entire model built inside out Right Once intake hatch fitted entire assembly can planked thin coat Safe-T-Poxy first applied Styrofoam aliowed cure Planking could Zapped Styrofoam August 1989 59 THE LEADER IN COMPETITION PROPELLERS 4 CYCLE SERIES 100 THP DESIGN TAILORED HELICAL PITCH DEVELOPED TO GIVE MAXIMUM THRUST AT 4 CYCLE ENGINE RPM ALL THE LATEST TECHNIQUES USED ON OUR PRO SERIES 3 SEE BELOW DIA PITCH THP PRICE 1266A77A8 136778 14677/8 1567 16678 PRO SERIES 3 NEW HIGH TECH AIRFOIL SECTION lOTO 200/0 INCREASE IN THRUST MFG OF SELECT HARD MAPLE WOOD WILL NOT FATIGUE LIKE SYNTHETICS FUEL PROOF HIGH LUSTER FINISH DIAPITCH PRICE 5S/34 634 72833/456 8334568 84566/7 94566A77A 104566A7 108W8W 10BEW 114677/778 11SW 11BEW 1187 124W 125W 1256 1356 1456 1556 164N 16678 test fly aircraft see what would hap pen Testing Engine fan first test deter well engine fan unit would perform aircraft two con cerns worried engine might properly draw fuel lower two tanks located below fan unit did want use pump also thought fan mounting method might cause excessive vibration quickly discovered engine much compression especially lit tle oil cylinder standard elec tric starter wouldnt turn over loos ened up glow plug slightly release compression cranked engine over electric starter Just feared engine didnt draw enough fuel start priming through fuel inlet line started almost immediately Once oil burned out en gine warmed up slightly stopped tightened plug Though engine would now turn over starter still wouldnt draw enough fuel restart primed again just before started immediately Obviously Id have design better way prime engine After engine reasonably warmed up gave full throttle adjusted highspeed needle valve peak rpm rich ened out about two clicks 05 77 OS No 8 plug turning Dynamax fan 21000 rpm vibra tion level within tolerance Holding plane different attitudes no effect engine run idle flawless Unlike first portion testing unequivocal success Water test first water taxiing tests re vealed two unexpected problems First scale wings model sat much higher water full-size air craft causing tip side im merse wing tip resulted poor taxiing characteristics Second water somehow getting fuselage Further analysis showed entering through hatch seams solve first problem built scale rockets mounted onto wing tips act pontoons stop leaks sealed hatch seams silicone sealer using Liquid Masking release agent hatches second water taxiing test very successful combination water rud der exhaust deflector connected air rudder model turned water command High-speed water taxiing test mo ment truth quickly approaching couldnt resist giving model full throt tle see what would happen amaze ment Sea Dart lifted gracefully out water onto its skis went on-plane still picking up speed As airplane reached what considered reasonable takeoff speed introduced about 50% up eleva tor Nothing happened tried full up eleva tor still nothing happened model oblivious commands continued skim ming across water like hydroplane sudden swerve drastically changed course flipped unceremoni ously onto shore Investigation showed two front ski struts broken right wing smashed end Apparently hit stump sticking slightly out water week later after implementing repairs moving radio battery pack nose tail ready resume test ing Feeling very close suc cess several friends 35mm video cameras hand record mo mentous occasion taxied model out well away th stumps aimed wind gave itfidl throttle rose up skis very quickly tail still dragged waterand didnt respond full down elevator lifting After dozen valiant attempts get on-plane air finally conceded defeat called day Flying test weather turning colder could no longer persuade daughter place retrieve Sea Dart water resorted putting land ing gear under skis attempting take off land cold windy Thursday evening Fond du Lac Miniature Aircraft Associa tion FMAA members gathered local flying field monthly fly-in meet ing plenty helpers fired up taxied Sea Dart position Heading model directly wind gave full throtfie quickly jumped air hold full up elevator just stay aloftan unexpected predicament threw verge panic Should abort will land Will continue fly Ultimately consistent scream ing sound OS 77 positive feel Futaba PCM gave confidence continue model now gaining altitude full up elevator Nursing upwind far could see slowly started gentle lefthand turnand airplane maintained alti tude assistant Gus Rebens burg able give full up trim held full up elevator model began gaining altitude command leveled off approximately 200 ft altitude ana lyzed airplanes flight characteristics idiosyncrasies Knowing deadstick landing would probably disastrous given amount up elevator required maintain level flight decided attempt first landing Gus assistance set up landing backed off throttle ap proximately one-third watched Dart settle almost picture-perfect return Earth Having concluded first flight model still nose-heavy recal culated center-of-gravity added 6 oz weight tail accom 60 Model Aviation NEW NEW RO PYLON RACING SERIES 500 DIAPITCHPRICE 7SN 5/N SERIES 400C 86677/7 9777 W WIDE BLADE EW EXTRA WIDE IU IUARRAW pushed felt secure enough reliabil ity OS 77 engine Dynamax fan Futaba PCM radio next test flight Brillion Fun-Fly light breeze Brillions relatively small field Im sure quite few bets placed whether Id get Dart airborneor end up swamp grass asked Bob Johnson friend vice president FMAA videotape flight first takeoff attempt Sea Dart heading toward pits aborted After realigning takeoff direction again applied full throttle Dart trav eled about 300 ft edge field before lifting off As lofted over marsh wings rocked ominously seemed close faltering moment could picture Sea Dart mock ingly rechristened Swamp Dart sink ing notoriety among other models-thatdidnt-quite-make-it forever after butt ridicule However again full up elevator Dart straightened began slowly gaining altitude Once shed attained full speed slight amount up trim neces sary airplane still sluggish lacked good vertical performance open ski wells skis extra landing gear wheels seemed acting giant air brakes least consolation knowing modifications full-size Dart too must have made flights unretracted skis re tarded speed landing uneventful pull back one-third throttle flare As test results make clear Ill need introduce several modifications con duct additional tests order optimize Sea Darts performance plan imple menting testing changes fol lows Modification Install larger wings Tests Attempt takeoff snow b Attempt takeoff water Modification Remove skis cover ski wells add wheels Tests Attempt takeoff grass scale large wings b Analyze highspeed performance scale large wings test results positive model gains hoped-for agility intend add retractable skis Perhaps fitting Scale edition Convair Sea Dart still transition full-size sea plane itself halted experimental stage Navy ran short funding rate especially retractable hydroskis Sea Dart model promises meld authenticity best performance attainable Thats going keep busy some time DWBRO TRIP SPIN KEEPS YOU IN Quick easy assemble Universal Designed balance items listed above special accessories Strong stable durable balancing wheels recessed prevent damage accidently dropped Du-Bros Tm- Spin prop balancer adjustable vertically horizontally conform balancing need Truly precision instrument built modelers expect very best Available now local hobby shop DU-BRO PRODUCTS INC BALANCES AIRPLANE PROPSALL SIZES JET FANS BOAT PROPS HELICOPTER ROTOR HEADS SPINNERS CAR WHEELS AND MOTOR GEARS 480 Bonner Road onda IL 60084 August 1989 61 BALANCE Specially designed locking cone securely centers locks props onto balancing shaft utmost accuracy -a responding advertisers mention read about Model Aviation