Level Flight Trim

[cgruby]

After flying my aircraft for a few hours, I find that it requires a lot of forward stick just to maintain level flight. The top of the stick winds up about in line with the bottom of the instrument panel. This requires almost maximum extension of my arm, which is really uncomfortable. I've added a fixed elevator trim tab to relax the forward pressure, making it a little more bearable. With stick in this position, the elevator is 14 degrees down relative to the stabilizer. I would like to raise the leading edge of the stabilizer, to allow the elevator to fly more in trim.

Is there any credible method of raising the stabilizer leading edge once the airplane is covered and assembled?

The airplane flies like it's tail heavy, but the CG data does not bear that out.
I've include the CG data:
10.13 (10.6) fwd
11.37 (16.0) aft
(The parenthetical numbers are the limits.)

If anything, the airplane is nose heavy according to the CG numbers.


Thanks in advance,

[n85ae]

Seems like a good time to check all your elevator rigging. That's the
thought that jumps out at me.

Jeff


After flying my aircraft for a few hours, I find that it requires a lot of forward stick just to maintain level flight. The top of the stick winds up about in line with the bottom of the instrument panel. This requires almost maximum extension of my arm, which is really uncomfortable. I've added a fixed elevator trim tab to relax the forward pressure, making it a little more bearable. With stick in this position, the elevator is 14 degrees down relative to the stabilizer. I would like to raise the leading edge of the stabilizer, to allow the elevator to fly more in trim.

Is there any credible method of raising the stabilizer leading edge once the airplane is covered and assembled?

The airplane flies like it's tail heavy, but the CG data does not bear that out.
I've include the CG data:
10.13 (10.6) fwd
11.37 (16.0) aft
(The parenthetical numbers are the limits.)

If anything, the airplane is nose heavy according to the CG numbers.


Thanks in advance,

[n85ae]

Flaperon rigging, check that also

[Av8r3400]

Flaperon rigging, check that also



X2 on the flapperon rigging.

[cgruby]

Flapperon rigging!!! I never thought of that. It's been checked several times after the rebuild job. But, I've never exercised the flapprons at all since I've had the plane. I guess I never saw a need for them, but I'll give it a try next flight.

Thanks to everyone for you inputs.

[Av8r3400]

If your flaps are reflexed up, this will give a nose up trim that will require pushing the stick forward.

Try pulling on (back on the lever) some flap action and I'd bet this will solve your issue. Many of the early kitfoxes use the infinite flap adjustment as a pitch trim.

[cap01]

the forward stab mount bolt should have provisions for adjusting the leading edge of the stab up or down. at least the model IV does

[cgruby]

the forward stab mount bolt should have provisions for adjusting the leading edge of the stab up or down. at least the model IV does

Thanks a-heap, I'm going to try the flap trim first and see what the result of that is. I didn't see any additional holes in the stab mount, but they could be covered up with fabric.

[cap01]

If there is fabric on the stab attach bracket , you should check a little closer as there should be more holes . My IV is one of the really early ones and I'm pretty sure it has a III airframe .

[cgruby]

If there is fabric on the stab attach bracket , you should check a little closer as there should be more holes . My IV is one of the really early ones and I'm pretty sure it has a III airframe .

Thanks, at first look, I didn't see additional holes, but I'll check.

[Dusty]

Sounds like something is way off!
If your cg is correct and assuming your wing rigging is also right,the tailplane or flapperons would be next to check.
Is your stabiliser flat or is there a twist?
This can be adjusted by the two rod ends(leading edge up to bring the nose down)
The forward mount may be adjustable , if it is safe to do so you could re drill the bracket?
After checking for twist ,test fly
I have found the best position for the flapperons in level flight is to sight against the horizon.
Anything more than few degree off creates a lot of drag.
The non symmetrical flapperons are very efficient at bringing the nose down but not so good the other way and would be very noticable
If your pitch changes significantly with power check your engine thrust line

[cgruby]

Thanks Dusty. Definitely some good areas to look at. As soon as I get the brakes back together, I'll be back on the trim thing again. Checking in the builder's manual, I don't find too much on stabilizer alignment.

Thanks again,

[dholly]

Chuck - the pic shows the forward HS mount on my old KF3. I assume yours would be the same. Also, the following info from an old KF Newsletter explaining how to set 'zero' and 'max' flap might be useful to you.

Flap Limit Stop

In the June, 1989 issue of the Newsletter, we showed you how to build a Flap Limit Stop; to find the proper degree of flap for your "stop", first find the neutral flap position as shown on page CF-18 Fig. CF-12, of your Construction Manual and mark that position for the "zero flap" setting. Next, move the control stick all the way to the left (or right) until it stops. While holding the stick in this position, slowly pull the flap handle up until it starts moving the control stick toward the center. When the top of the stick has moved toward the center 1-1/2 inch, that is Max Flap. This step can be completed after you have finished the rigging process on pages CF-17 through CF-19 of the Builders Construction Manual.

[cap01]

That's exactly what mine is like . When I made the tail mods , tabs were welded on the bottom tube of the vert stab for a upper fairing . Mine is faired now so it's not visible or I would have taken a pic