FF Power Model Trim Part II

Powerr Part March 1997 issue dealt preparing new model flight Part II takes through trimming process field first thing assemble model some hand-gliding modelers believe hand gliding doesnt really show much however feel another step overall process increases confidence model will fly intended hard tell much shoulderheight hand glide because launch angle speed can mask true characteristics model usually try find knoll other natural rise ground glide model has time stabilize glide standing bumper car might helpful What want hand glide reasonably buoyant glide beginning right turn previous setup should provide no additional adjustments dont get reasonable glide go back verify previous setup items Check timer functions verify proper operation includes running engine assuring timer will shut down engine engine vibration does include timer run erratically maximum safety timer should include quick-DT derhermalizer capability quick-DT timer has second function can adjusted release DT three four seconds after engine cutoff means cannot use fuel pinch-off timer during testing because timer stops fuel line pinched VIT Variable Incidence Tailplane airplanes quick-DT capability built-in because timer provides adjusting time interval between functions fixed-surface Nostalgia models have made up special timer uses flood-off principle shut down engine However instead shooting fuel engine intake just vent pressurized fuel overboard see drawing course assumes using pressurized fuel system strongly encourage using pressure system consistent engine performance no sag launch easiest approach popular pacifier type rubber fuel bulb case fuel forced bulb syringe fuel line pinched off fuel line opened natural elastic characteristic rubber bulb forces fuel engine under pressure Now sure timer will shut down engine deploy DT 3 seconds later ready first flight AMA Nostalgia models use full power three-second engine run quick DT first flight Old-Timer models use r seven- eightsecond runs quick DT ignition shutoff requirement makes very difficult implement quick DT bit risky setup proper particularly right-wing washin no major problems should occur Since article primarily addressing modem models AMA Nostalgia classes rest discussion aimed specifically towards principles apply Old-Timer models well however First Flight Use propeller expect use competition changing propellers will affect trim timer set three seconds quick-DT hooked up start engine Tune engine maximum rpm use digital tachometer available model must launched right wind steep 7O8Oo attitude right wing little low model attitude simultaneously start timer release model throw model Throwing will undoubtedly alter launch attitude result inconsistent power patterns Heres set up field box starter Im facing directly wind start engine turn slightly right raise nose steep angle lean model slightly away start timer release model practice will get same time Since things happen fast probably bit nervous just try verify model did anything violent subsequent flights observations will better What expect model climb out launch fairly straight start right turn start left roll case increase engine run four seconds try again four seconds spiral climb should clearly evident Again well increase engine run five seconds try again everything still looks good youve got made can get rid quick DT What have just described proverbial flew right off board never happens lets talk about some things likely see what 52 Model Aviation b Johannes about Remember use decalage adjustments primary control power pattern basic principle adjustment up-elevator tightens natural right turn downelevator opens turn call last effect Magic Down because great power-pattern trim problems can solved putting little down-elevator Now lets get back first flight What likely see two things 1 model will steepen its climb start over its back begin loop 2 model will start out straight ahead will drop right wing start steep right level descending turn conditions could result crash short engine run quick DT Both pitch-axis problems can improved adding down elevator beginning loop pure pitch-axis problem steep turn result natural coupling between pitch yaw axes pylon models add down must shim up leading edge stabilizer lower screw supporting trailing edge use shims sure use plywood no thicker A2 Its better adjust small increments avoid missing best trim point nylon support-screw method suggest 1/2 turn adjustment Repeat three-second engine run add down until power pattern looks like ideal described above increase engine run four seconds try again Before going fine-tuning adjustments lets go back describe initial flight may look up-elevator needed case model will climb straight away no right turn tendency perhaps beginning left roll severe situation model starts roll left nose over go over top say symptoms observed add some increments up-elevator until model exhibits desired power pattern down-elevator has eliminated tendency steep right turn indicates need what consider some secondary adjustments point might try adding some left rudder tab likely little left thrust will needed usually use 1 1/22o left thrust although some models may require much three degrees specific need left thrust will become evident go longer engine runs model starts power pattern correctly lays over level steep right turn about rolls left continues climb properly left thrust required add left thrust use full-width plywood wedge-shaped disc inserted behind engine mount assures solid engine mounting use washers under individual 1 2 3 Use existing timer mechanism Tatone Kmart KSB Make new brass face plate Solder pivot tubes face plateuse Sta-Brite solder 4 Bend 032 steel wiresfinal bend made after wires installed tubes 5 Assemble timer let run 3 4 sec past floodoff Mark location DT wire slot disc stop 6 Proper positioning DT slot should allow 7 sec engine run DT slot interfering flood-off wire bend OT wire and/or move slot necessary 7 Use small disc thin plastic keep DT line hanging up DT wire \ EXISTING SLOT IN DISC FACE PLATE 010 BRASSOVICK OT WIRE IFUEL FLOODOFF 7 WIRE 7 DISC FROM OLD TATONE FLOODOFF TIMER OR CUT FROM 015 BRASS s SMALL PLASTIC DISC CRIMP TUBE WITH DIAGONAL CUTTERS FOR FRICTION AFTER WIRE IS INSTALLED L TIMER ON/OFF TRIGGER WIRE NEW SLOT FOR DT WIRE LOCATED TO PROVIDE DESIRED DT DELAY Illustration Al Ostergaard May1997 53 Clockwork timer has quick DT function added use test flyingallows low-risk trim power pattern Diagram below shows modification procedure TNR TECHNICAL INC THE BATTERY STORE VIER LARGEST IISTRIBUTU FOR SANYO BAiTER IFS RECEIVER PACKS Part # Type V mAh Price 5 4N-11OAAlI3AA48110$1000 IN-3OAi2/3M48$I0O 4N-600AAPA48600 $900 *Kfk-MEAA180C$14 4KR-1100AAUPA481100$1600 R-I10Q~4A8Po$j&o 4KR-13005CSub C481300$1300 *KF~bo~tbC4%7O$2 4KR-1400AEA481400$1800 TRANSMITTER PACKS Part # Type V mAh Price AA9~0C 8OI 8KR-800PAE PA 96 800 $2500 $R4lQOAU0 NICKEL METAL-HYDRIDE Part# Type V mAh Price AA451250S19 4HR-4/5AUS4/5AA4 81850$22 95 H-AAUAA9615PS&0O FOR FREE CATALOG TNR TECHNICAL INC 301 Central Park Drive Sanford FL 32771 800-346-0601 FAX 407321-3208 MADE IN USA 433 54 Model Aviation ting bolts can distort engine crankcase soften mounting Distorted crankcases lower engine perfonnance softer mount may cause timer-vibration problems engine run duration keep making small adjustments until model does what want Make adjustment time dont adjust elevator thrust same time need able see specific effect adjustment complete five-second engine run flight good power pattern can stop using quick DT let model glide 20-30 seconds before DT five-second engine run model will high enough badly out glide trim should DT before hits ground Now can start working glide trim get adjusted before going back fine-tuning power pattern transition power glide following comments apply fixedsurface models have added down-elevator during power-pattern adjustment glide will likely fast steep Two adjustments can improve 1 Less stab tilt increase diameter glide turn 2 Move center gravity CG aft usually set stab tilt diameter turn want move CG fine-tune glide Dont afraid add weight tail needed sage old modeler once said properly trimmed model will always fly better out trim maybe -ounce lighter So true model stalls scallops glide can tighten turn stab tilt adding weight nose Since nose much shorter tail may require addition significant amount weight nose case may want consider modifying model After glide trimmed satisfaction adding weight check model find out balances relative leading edge wing distance between trimmed CG original CG much wing must moved back eliminate need nose weight move wing back simply cut off wing platform add desired dimension rear pylon cut off front pylon install new wing platform must sure original wing incidence maintained know may seem extreme some will save ounce two weight its worth effort adjusting glide alter rudder tab wing tail incidence will have start over power trimming VIT models glide adjustment independent power trim requires nothing adjusting rudder stop elevator glide screw situation can occur requires CG shift glide adjustment requires stab trailing-edge down power adjustment case CG must moved forward until adjustment situation reversed Again can done adding weight nose moving wing back either type model usually finetune glide slowing model down until slight stall appears reversing adjustment slightly until stall disappears Transition Power Glide want pitch attitude yaw rate turn engine cutoff such momentum carries model smoothly glide can usually fine-tune power pattern somewhat rudder tab Left rudder will tend open up turn under power However model tends stop steep attitude engine cuts off does large dip two right rudder tab may help Go slowly using small rudder adjustments until can clearly see effect Another technique Ive using good results add up-elevator Keep adding up until model starts steepen right turn near end engine run add left rudder until turn straightens BEST GLOW PLUG CONNECTOR Stainless Steel HEAD LOCK BEST DESIGN Welded No Solder Acid Flux Flexing Wires BEST NiCad BEST QUALITY & GUARANTEE MODEL PRODUCTS CORPORATION BEST PRICESt #045-WIO NiCad Charger$ 995 availabie write directSt #040-With NiCad$ 1595 add $100 $200 outside USSt #041-With NiCad & Charger$ 2595 MODEL PRODUCTS CORPPH 908 850-1508 PO BOX 100 ALLAMUCHY NJ 07820FAX 908 850-8860 PAT NO 4221452 GET THE BEST ut slightly left rudder tends hold nose up allowing sideslip-type transition described earlier point should getting good transition power glide Youll notice up-elevator technique speed-dependent engine runs longer less up elevator required can optimize trim four- five- seven-second engine runs used AMA Category III competition screw adjustment elevator really useful usually trim models five-second engine run add down-elevator sevensecond engine run four-second run add up five-second elevator position little less variation may required particular model technique best suited VIT models because glide trim independent power trim used fixed-surface models glide will affected incidence change effect may significant its compromises have keep mind Take notes progress through trimming process notes sketches should include timer settings engine runs DT times trim adjustments youve made effect final trim configuration information importantonce model trimmed may go several weeks months between flights cant expected remember details several models over interval Trimming starts well before ever get flying field cant put enough emphasis importance proper setup start approach trimming have outlined has successful several types engine-powered models should work well trim philosophy combined lots practice should help winners circle Fly much can become consistent launch become confident model Good luck Ill see downwind Johannes 5117 Silverlake St Charles MO 63303