I bought this ARF on Saturday morning. Spent the weekend putting it together and today I maidened it. The maiden flight went well. I'm a total newbie at 3-D flying. I play with it a lot on my G3 sim but never done it in real life. On the suggested low rates with about 25 - 30% expo it handled like a baby. I flipped the switches for high rates and played around a bit but got kind of nervous because I haven't got around to putting stripes on the bottom of the wing yet and orientation with this plane is very difficult when you are 2 or 3 mistakes high. Anyway, on about the 4th or 5th flight I had just tumbled the plane end over end and had pulled out of the dive when at least one of my elevators started fluttering VIOLENTLY. The plane didn't have excessive speed or anything. I chopped the throttle and the flutter stopped and I landed. Upon examination I discovered that the flutter had caused the fuselage to crack and split right in front of the horizontal stabilizer. All of my hinges are still attached properly and I'm sure that is not where the problem lies. What would cause this to happen? The plane was handling so well up until that point and don't know what happened. Any suggestions? I will try to get around to posting some pics of the damage tomorrow and maybe you guys can give me tips on repairing it. It sucks to have to repair a brand new airplane.

Thanks!
DaveCFI

There are a few things that can cause this
Are you certain that you CA'd the hinges well? There are a few ways of ensuring this - Drilling a hole in the hinge slot to allow the CA to wick in properly - I also drill a hole half way through the surface to the hinge area and put CA in there as well.

Is there any slop at all in the control linkages or servos used?

How fast is not very fast? Always use really fine props on such models (Eg 4" pitch or less on a 2 stroke).

Any slop at all in the controls will allow flutter to happen (Linkages, Hinges, Servos).

Any flex in the substandard push-rods used in arf's can cause flutter. I believe 4-40 should be used on any 3d plane .40 or bigger. Also, it is too tempting to use the inside holes on control horns to achieve max control throw. For example on a 45 oz. servo, the control rod is on the furthest hole out, and on the contol surface, it is on the middle holes, you have just dropped your leverage at the control surface to 22 oz. What could have been perfectly fine in a non-3d environment is now completely inadequate. Aussiesteve suggested reducing the force on the control surfaces by reducing the prop pitch. That is really good advice for any 3d plane.

There's some basics like everyone mentioned above which is vital on a 3D model. Of course there are lots of other things to do also but their a little more cumbersome like for instance sanding the trailing edges of the control surfaces completely blunt to induce drag on the TE, and then of course counter balancing all the control surfaces.

Key factor even with all the counter measures on a 3D model is simply this. THROTTLE MANAGEMENT!. I can't stress how important that is, when the plane reaches straight and level you should already be at half or cruising throttle (Sometimes even 1/4...btw you have too much power when this is the case! NICE), as soon as the nose pitches down towards mother earth the engine should be at idle already. As you gain more experience you'll discover where you can push the limits a little with the throttle but most 3D models are so overpowered you can really only go to full throttle when the nose is pointing all the way up or if you are doing manuvers where all the control surfaces are loaded up (Flat spins and things).

Like mentioned above, get a very small pitch prop to help prevent the plane from picking up speed. Manage the throttle still!!!. Always use decent control hardware, nothing less than a Futaba/JR super horn on the servo side and use the furthest hole out on the surface's control horn barring you can get the surface throw you need as is. Dual rates and things at max when doing this! Use a decent linkage system which is absolutely slop/play free, ball links come to mind here but honestly a decent clevis and pushrod will work in this scenario. And then lastly be sure to seal the hinge gaps between the control surface and the surface itself with either covering or some self adhesive tape (Packaging tape works btw).

Cheers
Spacey

hi Dave

you say that you chopped the throttle after the dive.
with a very light weight model like this you should chop the throttle BEFORE the dive.

best of luck

piroflip

All good advice. I know that 3D planes are a different animal. To the best of my recollection I did not have any throttle in the dive but I applied throttle when it leveled out. I am using the hardware that came with the ARF and I think the pushrods are way too flimsy. They can flex quite easily. Also I did have them connected to the horn on the closest hole to the control surface. (I caved in to that temptation I guess.) I was using an 11 X 4 prop. Hopefully I can repair this ok.
I will post some pictures later today.

DaveCFI

Dave you just figured it out:....

(a) Need 4/40 rods
(b) Move to outed outer control horn
(c) TAPE the hinge gap .... (my sugustion)
Use clear tape or covering..

Walt...