Help, plane wants to roll when looping
 

I did 3 test flights of my new Zen 50 today. I could not get over how well built that kit is. Everything goes together perfectly, and the construction/covering is better than I could do. On the first flight, I needed a little right trim on the aileron, and maybe a click or two of elevator. Otherwise she flew great and landed even better. The problem came when I started looping. Inside loops rolled a little to the left, but manageable. Outside loops rolled hard right, and it took a couple attempts to figure out how much left aileron I had to hold to keep the plane on track. According to my radio manual, if a plane rolls in different directions for the inside and outside loop, than one side of the elevator is moving more than the other. However, on the table, even with resistance from me, the two halves move exactly the same and are rock solid. My brother thinks he remembers reading that the rudder trim could be off (balanced out by the aileron), and that it shows up in the loops if it is. The wing is very stiff to stress and appears perfectly built. Any ideas?

Thanks,
Rick

Help, plane wants to roll when looping
 

Have you checked the lateral balance?

balance
 

When the wing is off, it balances perfectly L and R. I have not tried balancing the entire plane, or carefully observing other manuvers yet to see if one tip needs a little weight, but I find that hard to believe....

Rick

Help, plane wants to roll when looping
 

Rick,

If you are using the split-Y elevator control rod, it may be that one of the Y is flexing more than the other under load. If this is the case than you may want to use the MK bellcrank to drive two elevator halves more accurately.

Also, you want to do the lateral balance with the wing on as the engine muffler position or equipment location in the fuse may cause one side to be heavier than the other.

Azhar

Help, plane wants to roll when looping
 

Have not had a plane yet that did not need a touch of weight in one of the wing tips to correct for lateral balance. Would never put one in the air without checking it.

Help, plane wants to roll when looping
 

Check the horizontal stabilizer to wing alignment; ie they are parallel, a visual should confirm that. If one wing tip is higher, then inserting some wing seating tape on that side of the wing seat will help.

When attaching the horizontal stabilizer to the fuselage in any plane where the stabilizer cutout is precut from the manufacturer, it is important that the stabilizer is attached with the wing fully seated and bolted down on the fuselage to check for elevator alignment. Even a few degrees out can have an exagerrated effect on perfomance. I found this the case with most similarly constructed arfs.

more info
 

Thanks for the great suggestions. I will check the balance with the plane put together. Incidentally, the muffler is on the left side, the side that acts heavy during loops, so maybe that is the problem. The wing alignment with the stabilizer looks good. If it is off at all, it can't be more than 1 degree. Again, the worse rolling happens with outside loops, when the elevator rods are pulling, making it less likely in my mind that differential elevator movement is the problem, but I will keep it in mind.

Thanks,
Rick

Help, plane wants to roll when looping
 

Help, plane wants to roll when looping

If you already checked the elevator halves it almost certainly is the planes lateral balance. You said you checked the wing balance with it off the plane but you really need to check the lateral balance of the plane with the wing on. Ihave a kyosho cap that off the plane the wing balances perfect but for some reason had to add a ton of weight to the left wing tip for the plane to balance laterally. I found that quite odd but it does fly straight!
Happy flying
Tim

what to use for weight
 

If I find I have to add weight to a tip, what do you guys use? Drill a hole and place a heavy bolt?

Thanks again,
Rick

Re: what to use for weight
 

[QUOTE]Originally posted by rdalcanto
[B]If I find I have to add weight to a tip, what do you guys use? Drill a hole and place a heavy bolt?

That depends on how your wing is constructed . If the tips are solid balsa drill some holes and epoxy some fishing sinkers or what ever you can think of that has some weight into the holes. If you have a thin ply/balsa wing tip then some surgery is usually in order. In this case I usually slice a rectangle the width of a lead stick on weight , cover in epoxy insert into wing tip like a coin and using a "L" allen wrech finaggle the piece of lead up against the inside of the rib. Recover the hole.I have found using anything other than epoxy to secure your weight results in your weight flopping around inside the wing bay over time .

Tim

Help, plane wants to roll when looping
 

Start with some stick-ons first. Clean area real well, and apply accordingly. Do this before you cut. Test fly with the stickys, and after that install them. The Zen has fiberglass tips too, so a small cut in the underside just inside of the tip would be undetectable. Then you can glue the weight to the outermost rib. Good luck. :)

Balance way off
 

Wow, that muffler way out to the side sure has an effect! I finally was able to check my lateral balance, and it was off by quite a bit. I'm sure it is the muffler since everything else is symmetrical. It also explains why I needed right aileron trim on the first flight..., COOL! I can't wait to test fly it again Sunday (hope the weather will be good :D )

I'll let everyone know how it does next week.
I really appreciate all the help!
Rick

how was the outcome???
 

Did the extra weight in the wing tip help???
I have a Zen 30 and the same thing has happened to me.
When I try to do a loop, the plane will snap out of the loop.
Mine will do it to the right. My muffler is also on the right.
Thanks

Snaping out of the loop
 

I have an Extra 330l 33%, I had the same problem and what was causing it was too much elevator throw. If the lateral balance does not fix it try reducing you elevator throw by 1/2 of what you have now. I had to reduce mine by 75%. I set up a 3d switch (dual rates) so I could get the throw back for hovering. Just a thought!