sledman

My Feedback: (2)

I recently acquired a used World Models Tai Ji .40 size pattern aerobatic plane, and it seems to fly well, but snaps out of loops at the top. Unfortunately, I don't have the suggested throws, or a manual, and the manufacturers website doesn't have the information, either. I've got 1/2" up, and 1/2" down travel on the elevator, all the control surfaces line up well, the model is balanced both ways, using an O.S. .46 FX engine, Futaba BB servos, and I really don't know what to try next. I did have to add 3-1/2 ounces of weight to the nose, as it was very tail heavy initially, and I double checked my Futaba 9C to make sure I didn't have something programmed screwy in there, but that wasn't it either. Any ideas? I think once I solve this problem, that it should fly better in every way, because whatever is causing this, is probably affecting other things in an adverse manner. HELP!!!!

FHHuber

What's happening is you are giving too much elevator for the airspeed.

You can make the loops a little smaller, so you won't have lost as much speed by the time you get to the top.

You can try changing to a longer, lower pitch prop; giving more vertical climb authority.

You can reduce the elevator throw... But this one may make it so you can't pull the square corners needed for some maneuvers.

If you can... find a way to reduce tha amunt of dead lead ballast you are using... 3 1/2 oz is a huge amount. Try a heavy hub, or the flywheel style weights that bolt on with the prop (replacing the front prop washer) The further forward the weight it, the less weight you need. .40 size pattern planes need to be kept light.

sledman

My Feedback: (2)

Thanks, I'll try a prop weight. I'm swinging an APC 11x6 prop on a .46 FX right now. Any recomendations as to where to go from there?

FHHuber

Try an APC 12.25 X 3.75 Its a prop normally used by Fun-Fly guys, because of how much pull you get at low airspeed and high engine rpm... top speed will be reduced, but your vertical performance will improve significantly. It will also help you to slow down on vertical down lines.

You can also try 11 X 5, which is what I use on most of my .46 powered planes.

sledman

My Feedback: (2)

Thanks, I've got two of the 12.25 x 3.75 already on order for the Modeltech Magic 300 that I am assembling. That's the recommended prop for that plane, which is a .46 size plane. I'll be running the new XLS .52 engine on it. 'Till then, maybe I can get a 11x5 to try. I really do like to fly slower, with more vertical authority. Once I master this plane, I will probably trade it off on something slower, but I want to beat it first!

sledman

My Feedback: (2)

UPDATE: It looks like the snap problem is due to too much left engine thrust. In straight up vertical climbs, it would go left. Rudder trim was required to make it climb straight, then loops after that were MUCH better. I've got the engine mounted with hard rubber faucet washers between the mount and the firewall, so I'm going to try turning the right screws in one turn, and the left screws out one turn, and see what that does. Otherwise, I'll just add a metal washer on the left side. Also, I was going the wrong way by adding weight. I'm down to 2 oz's now, and it is flying better. I bought this plane used, and don't know exactly what the recommended CG point is, so I guessed. I forgot that swept wing planes usually have a CG point a little farther back. Once I get the CG and the left thrust correct, I'm going to dial in the up/down thrust.
I'll keep ya posted!