steprman

I've flown the GWS Beaver many, many times right up until I hit a small tree and cracked the wing OFF !! I put a new wing together, just as the first, now the plane barely even flies. I would describe it as "porpoising" in that it goes nose up, then nose down, nose up etc etc and I do not have control.

What does this mean? Is the CG off some how? It's the exact same wing as the old one, so you would think all things being equal, it would be the same.

Thanks for your help and advice.

Andy

Flypaper 2

Andy:
Sounds tail heavy or the incidence angle has changed. Is it the same batt. and mounted in the same place? Was the wing saddle, where the wing sits on the fuse damaged,? or if the wing is moved ahead or back on the saddle will change the CG. If possible, move the wing more rearward on the saddle, which would move the CG more forward, which is what you want. Hope this helps.

steprman

Gord,

I do appreciate your reply....thank you for that. As for the wing, it all seems to be the same as before. The area in which the wing touches the main fuselage is only wide enought to accept the wing, therefore I can't move it in either direction. The wing saddle was not damaged, only the wing tip snapped off.

Do you have one of these planes by any chance. I meausre the balance point as being about 2 3/8" behind the leading edge and this strikes me as far back, but I did not measure this when it was brand new. This would seem to support your tail heavy concept as well.

Incidence Angle: I have read about this before, but can't recall what measure this is.

Any Help you or anyone else may have would be appreciated highly.


Andy

Flypaper 2

Andy:
The CG should be no more than 1/3 of the wing chord. That CG would would be good for a wing chord of 7 1/8 ins. I have the GWS Zero, which I modified to fly better after putting a brushless motor in it. Had to take some incidence out of the wing, and put engine down thrust in it to keep it from going over backwards on launch! . Incidence is measured from the thrust line down the centre of the fuse, from front to back in degrees.

steprman

Cord,

Thanks again!

My wing cord measures 6.5", so that puts the CG somewhere along a line 0.4" closer to leading edge. Sounds like I need to add some nose weight, but I sure hate to do that in such a light, low powered plane. As for incidence: Is this the angle of the wing compared to the thrust line or the angle of the entire plane compared to the thrust line.? I am somewhat concerned about the incidence, as the engine mount did become loose at one time. I reglued the mount, but with this plane it is real tough to know, just how precisely I have it back in the right spot. It sure looks centered and squared, but if we're talking only a few degrees of displacement, I couldn't see that by eye.

I greatly appreciate your advice and I really want to get this plane back in the air.


Andy

Flypaper 2

Andy:
Your right, CG should be a little less than 2 in. from the LE. Thrust line is usually from the middle of the engine to the tail. usually at the attitude of level flight at cruise speed. so if you look at it from the side, the wing will look like it's tilted up a bit at the leading edge. The engine down thrust could be part of the problem. There again, If you look at the fuse from the side, set the prop so it sits vertical, It should be noticably tilted down about from the imaginary thrust line. If not enough downthrust, it will try to climb drastically, stall, nose will drop, speed will build up, go back into a climb and repeat the cycle. What I did on the Zero was, take the motor off the square shaft, shaved the top front of the wood shaft till the motor sat on about four degrees downthrust, glued a piece of balsa on the bottom front and carved it so the motor would slide back on with a snug fit. If this not clear, just holler back. Sometimes I'm not to good at explaining things.