Plane hunts

[rich gorrill]

Hi all, I recently acquired a used Smoothie A.R.F. Crashed a few times but nothing major. Problem is it hunts in level and inverted flight. Balances right on the front spar which I think is right. There is a little slop in the controls, when you hold the elevator rigid there is play in the flaps and vice versa. Could this be my problem.

T.I.A.

Rich

[john e. holliday]

Very likely.  Matbe ass a little nose weight and try it.  Some times it don't take much.   But, I've had planes with solid controls that would hunt until I got a couple of flights in.  Also another thing and I'm guilty of this, are you holding hand still while flying level.

[Randy Cuberly]

A little slop in the elevator typically will not cause an airplane to hunt.  Slop between the flaps and bellcrank definitely will.

Your post said when you hold the elevator rigid then you feel slop in the flaps...however if in fact you are holding the elevator rigid the slop you are feeling could still be in the elevator to flap linkage.

To test the flaps linkage you must hold the bellcrank rigid and then try to move the flaps.  If the flaps can then be wiggled you indeed have slop in the flaps and that will cause hunting and must be fixed.

Another thing that will cause hunting is sticky controls.  The controls at the leadouts should be very free to the extent that they will move under their own weight!

The CG on this airplane should be around 15-20 % of the mean average chord.

Randy Cuberly

[Dave_Trible]

Hunting is usually the result of the flaps and elevator not being aligned straight with each other.  A bit of slop in the controls can help solve this to a degree,  allowing the control surfaces to self- align with each other in the air if they weren't off much.  Misalignment  of the wing centerline with the stab and thrust line can also cause this.  You mentioned it's been crashed and repaired.  I'd suggest something went south in alignment on one of the repair jobs. (If it was even correct to begin with). Check it over carefully and measure what you can.

Dave

[rich gorrill]

Thanks for the help, I,ll try a smaller handle spacing and remove some tail weight, also re-check all alignments.

Rich

[Dan Berry]

Thanks for the help, I,ll try a smaller handle spacing and remove some tail weight, also re-check all alignments.

Rich

One change at a time.
Remove tail weight first.

[Will Hinton]

There is one other possibility for the hunting.  I had my first Crosswind doing that, tried all the things listed here but while at the nats, Crist Rigotti told me to put a tad of down thrust in the engine.
I cut a couple of tabs off a .010 sheet I had, put them under the forward mounting screws and presto -no more hunt.  He said Bubba had told him about it, so if comes from him, I gotta listen.

[Steve Helmick]

Since it's an ARF...some have found theirs came with the leadouts crossed inside the wing. This would likely result in them rubbing where they cross. That can't be good!  Steve

[Dennis Nunes]

I had a similar problem with my Flite Streak. I used a 3/32" piano wire pushrod (old school) and it was flexing when up elevator was applied. So I installed a pushrod guide and that stopped the flexing. However the hole for the pushrod guide was to "tight" and friction created a hunting problem. I had to enlarge the hole just a little bit and the majority of the hunting problem went away.

But I still had a small tendency to hunt. I had used piano wire leadouts with 3/32" brass tubing in the adjustable leadout guide. Somewhere on this forum I read that this could cause a hunting problem and apply some oil down the solid piano wire leadouts. Sure enough it took care of the hunting issue.

I hope this helps.

[Bob Hudak]

Rich,
 I had a Smoothie ARF. It did the same thing,lots of hunting. I found the flap horn and elevator horn both wallowed out. I fixed it by bushing the holes with a piece of brass tube JB welded in place. You'll have to make some holes in the fuse to see this.
       Bob