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Alpha P-51 trim problem

Old 12-27-2005, 01:26 AM
  #1  
jblloyd
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Default Alpha P-51 trim problem

I have about 10 flights on my Alpha P-51 and I cannot seem to get it trimmed for level flight. When flying at 1/2 to 3/4 throttle, it wants to climb. I have moved the CG forward about a half inch in order to make it a little nose heavy but I still have to add about 6 to 8 clicks of down trim to get the nose down. I am running a MJ 28/7-35D motor, which is the one Hobby Lobby recommends so I don't think it is overpowered. I am assuming the incidence is correct since it is molded. Otherwise, this is a great flying little model.

Has anyone had this sort of problem with Alpha planes?

Thanks

Last edited by jblloyd; 12-27-2005 at 04:22 AM.
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Old 12-27-2005, 03:54 AM
  #2  
Twmaster
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Perhaps shimming the motor for a hair of down thrust?
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Old 12-27-2005, 08:36 PM
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Have you flown it with no power? How did it fly ? Balance it out for no power glides. THEN
Do the power shimming adjusting.
All models are going to have to glide down sometime. Have it balanced out by all controls at neutral and hand toss it in 2' to 3' tall field, till weight movement makes it a pleasure.
Then do the power shimming of the engine.
-
- Glide first then the motor shims.
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Old 12-27-2005, 11:53 PM
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jblloyd
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Thanks for the advice. I have not tried a "no power" glide, although it seems to glide at an acceptable rate when I have landed with no power. I will check out the balance by hand gliding it, as you suggest before changing the motor alignment.
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Old 12-28-2005, 01:48 AM
  #5  
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JB. The purpose of the test glides IN DEEP 2 to 3' grass is to get a nice smooth straight glide to the ground WITH ALL CONTROLS LOCKED in NEUTRAL.
This is a risky thing.
Balance it at or in between the 2 specified CG point-s in the shop.
Then the neutral tosses.
USE DUCT TAPE to hold the battery in place.
Make VERY sure the surfaces are at level, if the surfaces have flat bottoms.
I put a stick across them as a good check.
Again the hand tossing is risky, till you find a speed that gives the right amount of power for gliding.
Cheeses! DO NOT DO THIS ON A SLIGHTly breezy day. Almost dead calm is best.-----ONLY toss into the wind.
You will have to probably reset all the clevises when ok.
I start my tosses at about 2' above the grass. Then as confidence builds go higher.
You will get it so perfect, that you think of flying a glider later.
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Old 01-01-2006, 03:39 PM
  #6  
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All of these Alpha Models have built in positive incidence in the wing. Naturally the faster they go, the more they will climb. As per Alpha's instructions, I have found that putting about 2mm of up trim on each aileron aids in dumping some of the positive lift generated by additional speed. With this done, the airplane does not have as much of a tendency to climb as you increase speed. I'm currently flying the Alpha Corsair and the Alpha Nakajima with the above set up and neither airplane is difficult to fly straight and level. If it starts to climb at the speed you're flying, do like full scale pilots do and roll in a little down trim.
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Old 05-05-2006, 07:04 PM
  #7  
arck
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Default How is the power

How is with the recommended Hobby lobby motor or witch motor you suggest for this plane P 51 Alfa Model
thanks
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Old 05-06-2006, 01:31 AM
  #8  
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I have the blue jet outrunner motor and the airplane's performance is great.
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Old 05-06-2006, 01:40 AM
  #9  
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I balanced all three of my Alfa models at the recommended balance point and went out and flew the airplanes. Get somebody else to toss it on the maiden flight and trim out the airplane. Once trimmed, you can toss it yourself to get it airborne. As I said above, all of these little models have positive incidence built into the wing, so the faster you go, the more she'll want to climb. Trimming it for level fight with a hand toss without power into high weeds will not make it stop wanting to climb as you increase the speed with powered flight. It is basically a waste of time and effort. Build it, balance it, go fly it, and trim it as needed. These little airplanes fly great and track very well but there tendency to climb with added speed is a function of the wing incidence built into the fuselage, which you can do nothing about. Doing as the instructions say (you did read those didn't you?) in having each aileron trimmed up about 2 mm will help deminish the aircrafts tendency to climb at higher speeds.
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Old 05-15-2006, 09:39 PM
  #10  
arck
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Default blue or red

Some of our field pilots recommends the red one,,, which is the best for this warbird,,,has anybody prove the red AC 28/7-30D Outrunner Brushless rather than the AC 28/7-35D Outrunner Brushless Motor? ,,,,
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Old 05-19-2006, 07:06 PM
  #11  
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Default Motor for Alfa Warbirds

I have the Blue Jet Outrunner motor and run a 9x6 SF prop on the airplane. Performance is outstanding, drawing less amps than the Red Outrunner motor. I can get 18 min. of flying on a 1320 3 cell lipo if I don't run wide open the entire flight. Half throttle is more than fast enough to do any manuever you want. At full throttle it will got straight verticle. The guys at Hobby Lobby recommend the Blue motor.
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Old 05-19-2006, 10:01 PM
  #12  
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wrt the corsair, i fly with the blue outrunner now...but flew the stock setup at first and it flew very well also.
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Old 05-19-2006, 10:52 PM
  #13  
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Another option is to mix some elevator with the throttle. Tom
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Old 05-20-2006, 12:21 AM
  #14  
jblloyd
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Thanks for all the great advice but I'm sorry to say my little P-51 has gone to the great airport in the sky. Remember, check the model on your transmitter before launching aircraft.
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Old 05-20-2006, 01:50 AM
  #15  
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JBLLOYD- That SUCKS. I wish I could say that I've never made the same mistake, but I would be lieing. At least you can replace it, I forgot to reverse a servo once (elevator) and wrote off my now impossible to find Scoripo Albatros. I'm sure everone here can feel your pain to one degree or another. Kinda solves the climb under power problem though huh?
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Old 05-21-2006, 02:13 PM
  #16  
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The climb under power can be cured with enough downthrust. Just keep adding downthrust till it will keep a straight heading with any power setting. Have a GWS Zero that had the same problem. To much incidence and not enough downthrust. All of them did this and downthrust and raising the wing trailing edge were the fixes.
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Old 05-21-2006, 09:17 PM
  #17  
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If you put too much down thrust, when you chop the power, the airplane will immediately climb before losing airspeed.
Lost my Nakajima because I forgot to change model memory. Won't do that again....at least not for a while.
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Old 06-01-2006, 12:14 AM
  #18  
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Finally got mine, the Marie one, one red mpjet, one fenix 25 amp esc , two hs55 servos, one 3 cell lipo 1350mah 20 C and one berg4L receiver, what's next??,,,building?,,,hope we do all well,,,,
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Old 06-12-2006, 03:21 PM
  #19  
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Default First attempt, crash

My first experience with the alfa p51 was horrible, I told a friend to hold the plane 25 grades up, then full power, full up elevator, the plane made a loop near the ground, the result was the nose totally break , the mpjet its OK, I trying to fix the nose with epoxi at home but its difficult because the weak foam, WHAT could happened, any suggestions to repair the nose?, why the plane immediately made an incontrolable loop?,,, any opinion?
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Old 06-12-2006, 10:31 PM
  #20  
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Here is the result of a bad first attempt....
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Old 06-13-2006, 03:17 AM
  #21  
flypaper 2
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Neutral elevator on launch would have been fine. it's the full up that did her in. Hot glue gun works well on foam, although epoxy works well too.
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Old 06-13-2006, 04:26 PM
  #22  
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Thanks flypaper2, yes it seems the full up elevator was the problem, I will try this Saturday with neutral elevator as you advise, could you give me your setup trim in aileron and elevator please?,,,,
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Old 06-14-2006, 02:32 AM
  #23  
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Goes for preflight for any plane of conventional configuration. Eyeball the plane from tail to nose. Ailerons should be level with the bottom of the wing or a bit of up on both if anything. Looking at it from the side, the elevator should be parallel with the stabilizer. Launch the plane with the wings perfectly level with the nose about 10 degrees above the horizon. Keep it at that 10 degrees with the elevator till you get it about 75 to a 100 ft up, throttle back to level flight before you start playing with the trim levers. Lots of luck:p
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Old 06-14-2006, 02:51 PM
  #24  
arck
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Thanks, so the elevator should be trim level with the stabilizer, nothing up, the two aileron's should 2mm up, 75 % throttle I think, the toss with 10 degree's up,,,,,, allright, wish me luck,,,,

Last edited by arck; 06-14-2006 at 03:57 PM.
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Old 06-17-2006, 05:00 PM
  #25  
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I got my 5th flight on this plane this morning. I finally got it trimmed to a point where I could let it fly without stalling all the time. I am using a fair amount of down trim. I trimmed the elevator to what looks like neutral at the linkage. But I have to add a relatively large amout of clicks of down at the radio.

The plane is probably about as fast as my e-flite P47. The mustang uses a 9x4.7 SF prop, so I am not as fast as some people are flying it. But that is fine with me.

This plane is more nimble (or less stable) than the e-flite. That's not necessarily bad though. I felt like this pane is just higher performance. I had a hard time doing clean loops because the plane was difficult to keep in line while I was pitching up and over. I may need some practice!

I got 10 minutes on my TP 1320 and came in at 11.32 volts, mostly at about 2/3 throttle. The landing was very smooth and uneventful. Set-up on final and trottle back to anything below about half, and the plane glides in. I chop the throttle just before I flare so the prop isn't under power when it hits the grass.

I think this Alfa is now officialy in my flightline!! I have two more 1350mah batteries coiming this week, so I can finally get more than one flight a session with this plane.

Good luck Arck.
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