Hello everyone. I would like to thank everyone for all the usefull info. I built a sig 4*40 kit about 4 months ago and am very happy . Now I'm trying to learn a few trticks but I can't get it to hold a knifedge. I't dives to the belly hard,if I pull up it starts to roll back out and falls pretty quick to ground.Just wondering if anyone has any hints that might help. Thanks.

I am just getting the hang of knife edge flight. It's a bit tricky, at least for me. My first suggestion would be to ensure you have sufficient throw on your rudder. As in all it can be! I find that I have to use the up and down elevator to maintain my heading, and the ailerons to keep it on edge. I think what you describe sounds about right, just practice the control movements to hold your attitude.

Mine "dives to the belly" as you say, too. I have mixed a little "up" elevator into my transmitter when rudder is applied and it now tracks straight on knife edge. It was all trial and error to get the right combination of up with rudder. Before the mixing, I would just anticipate the belly dive and hold a little up elevator. That worked OK, but wasn't as rock steady as the mix is now.

Quick and easy testing.

Recently I used plastic washers on wing bolts to act as captive fasteners. The washers were cut from a lid pilfered from the kitchen. She will never miss the lid.

Much to my surprise the washers improved knife-edge flight. Apparently the miniscule thickness of the washers changed the wing incidence enough to correct knife-edge without using elevator. Anyway the test would be quick and easy and reversible if it makes matters worse. It’s easy to cut a handful of washers and go testing.

Bill

You will find if you do a search on here that the problem you are describing is a well known "feature" of the 4* design. You can help your knife edge by increasing the rudder throw and adding some area to it as well. When you increase the area, increase it more at the bottom than at the top. Like 1/2" at the top and 1 1/2" at the bottom. The other suggested way to "fix" the problem is to cut the fuselage actually lower the horizontal stab some. However, that is a bit drastic.

Thanks. I don't have a good radio only a skysport. I read about increasing the incedence and about lowering stab but cutting the back off was a little to much and changing wing seams real easy so i'll try that first.i'll let you know how it does. Oh,I already increased rudder when I built it. Thanks again!

It's all in the ability of the pilot. It took me a while, but I can fly a Telemaster trainer in perfect Knife edge.

Where is your CG?

Did you mean to reply to me? If so, mine on my Telemaster is on the spar.

I dont know about the Telemaster but on the 4* I find the best CG just behind the spar. That is where mine is set. At that point it takes just a push inverted to hold level and it will fly KE as long as I want. That is with a 40 LA peice o junk.
My boy did his first spin with it last weekend. Had to laugh. Thought he was going to fall over because of the scare and excitement factor all at once.

Thanks slyder. my cg is on the spar. I'll try to move something around to get it back a little. Going to try to go tonight. How far off the spar should I go?

Woops here, I would move it back 1/4 of an inch at a time till it works.

I went last night to try a few things without much luck . Moved CG back 1/4 inch and shimed TE of wing. I thought it floated on landing before! Flies pretty good at idle now. I'm going to have to remove some of the shims from the wing . I guess it helped a little alltogether . Just wondering has anyone tried lowering the horizontal stab and if so how much? I dont think its something I want to have to try more than once.

oh oh