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TM 400 -- thrust trim--need advice please

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TM 400 -- thrust trim--need advice please

Old 02-14-2005, 02:05 PM
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Default TM 400 -- thrust trim--need advice please

I just completed the assembly of a Tiger Moth 400 that my grandkids bought me for Christmas. Rather than using the stock 400 motor, I used a lighter, and more powerful Razor 2500. I’ve got the COG at the recommended point by adding 1 ounce of lead to the nose. I mounted the Razor using the kit stick and glued the stick into the fuselage cut-out without any modification.

On the first flight, I found that the thrust angle was way off and I re-mounted the motor with about 3 degrees more down thrust. This is still not enough. When trimmed for level flight at ½ throttle, the Moth will drop nose down with throttle off and with WOT will pitch up to actually do an inside loop.

I’m going to need much more down thrust than the stock motor mount. How much modification to the stock thrust lines should I expect to need with the more powerful Razor 2500? Based on the flight with 3 degrees, it may take 6 + degrees. Have I got something wrong or is that reasonable?
Old 02-14-2005, 09:13 PM
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Default RE: TM 400 -- thrust trim--need advice please

I have the TM400 with a himax 4200-25 in it.
I had to move the lipo 2100mah battery as far forward as possible and add 1.3 oz of weight to the nose.
It is a little sensative to the balance point.
I have the engine thrust angle stock.
It flys great once balance set right.

Tony
Old 02-15-2005, 06:31 AM
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Default RE: TM 400 -- thrust trim--need advice please

Thanks.

I re-checked COG and it was at 15mm leading edge of lower wing, measured with the plane upright. I've added an additional 1/2 ounce of lead and it's now at 10mm. I'll try it as soon as weather permits with the downthrust and COG at 10mm. Maybe my problem was all COG. Where exactly is your COG and how are you measuring it? The manual is not very clear on COG set-up; it describes the COG distance on lower wing, but shows the balance point on the upper wing.
Old 02-15-2005, 07:35 AM
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Default RE: TM 400 -- thrust trim--need advice please

COG is from 0-10mm back from leading edge of lower wing.
J
Old 02-21-2005, 01:34 PM
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Default RE: TM 400 -- thrust trim--need advice please

I have the TM400 also. What is the best procedure for balancing? I've seen guys here use pencils, dowl rods, fingers, etc to balance the wing on. Should the a/c actually balance on your finger, or just jugde as to which way it falls most?

Thanks.
Old 02-21-2005, 04:35 PM
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Default RE: TM 400 -- thrust trim--need advice please

I balanced mine using my fingers...flipped the plane upside down and balanced from the lower wing. 0-10mm from the leading edge just like the manual says...she flys perfect, didn't have to add any weight. The motor and batt alone were enough.
Old 02-27-2005, 04:31 PM
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Default RE: TM 400 -- thrust trim--need advice please

I added no weight, and I am using a light brushless motor. This aircraft fly's very well a tad bit tail heavy and its very forgiving in this regard. I did relocate my radio and esc as far forward as possible, and hollowed out the batt compartment as much as possible to have the Lipo's as far forward as possible. I normally like a nose heavy or dead COG craft, this one flys as an exception.

I am confused on why the thrust angle is not correct. My setup has enough power to do a 2 foot ROG with a 45 degree climb-out.
Old 02-27-2005, 09:28 PM
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Default RE: TM 400 -- thrust trim--need advice please

I can't understand why everyone is having so much trouble balancing this plane. Mine balanced spot-on with TP 2100 3s lipo and stock motor. I have a brushless I could put in it but it flies so well on the 400 I'm just going to wait 'til I burn it up.
Old 02-27-2005, 09:52 PM
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Default RE: TM 400 -- thrust trim--need advice please

I can't understand why everyone is having so much trouble balancing this plane. Mine balanced spot-on with TP 2100 3s lipo and stock motor. I have a brushless I could put in it but it flies so well on the 400 I'm just going to wait 'til I burn it up.
Amen

Same set up here, even with a 2cell 2100 CG was non issue

Belgy

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