Hello Everyone, I'm new to the hobby after many years of saying someday I want to learn how to fly radio control airplanes. I have just finished an Aero Star 40 and starting to build an Eagle 2 for my second airplane. While building the Eagle 2, I noticed that the instructions are very specific in saying that the flight control gap should only be about 1/32 of an inch max. to prevent flutter. The gap on the Aerostar 40 elevator is about 1/8 inch. The Aerostar 40 instrutions just said to push in the hinges until the pin area contacts the surface. I also noticed that the ARF's hanging in the hobby shop also have very small gaps in the flight controls. I probably could have shoved the hinges in a little farther, but was trying to prevent any epoxy from getting on the hinge pin area. The hinges I used are Du-Bro large pinned hinges.

Is 1/8 inch gap anything to worry about before I have the Aerostar 40 test flown? Or is it really that critical?

Thanks

Keeping the hinge gap small isn't so much to prevent flutter but to make the controls as effective as possible. Consider the elevator...when you give up elevator you're making the whole tailplane into a cambered airfoil. There's a low pressure set up underneath compared to what's on the top surface. In effect this is what pulls the tail down which points the nose up and the model climbs. But with a large hinge gap (or any hinge gap in fact) air will bleed through the gap into the low pressure area and reduce it's effectiveness.

All you need to do is get some hinge sealing tape and put it on either the top or bottom surface to cover the gap. Your plane will fly OK as is but you'll need much larger movements of the controls than you would with the gap sealed.

I'm no expert, but an eighth inch seems a little large. 1/16th sounds better.

I would just seal the hinge line with clear shipping tape or the covering that you used to cover the plane, that way the gap size doesn't matter (on a .40 sized trainer).

I've had both of those planes, the Eagle II and the Aerostar 40 and learned to fly on them.

The elevator servo failed a few months ago on the Aerostar after 9 years and over 1,000 flights! What a tough bird! Building another for my grandson to learn on.

Good luck and happy flying!

All good advice for sealing the hinge lines. Get in the habit now and do it on all your planes. It just makes sense!

Space between control surfices surves a purpose. Keep controls from binding and loading servos. Seal gap with covering materal
or tap as stated. check for free movement when finished.

FLY SAFE LIVE LONG

When using tape to seal the control surface gap, I pop the clevis loose. Then deflect the surface all the way up and put tape across the bottom of the surfaces. This guarantees for me that the gap is sealed and the control surface will still move freely.

Plus, since it is on the bottom, it isn't so obvious.

When using hinges of the type you used, I normally make a small V notch on both control surfaces. This lets the hinge pin portion to fit into this. Also, I dab a tiny bit of Vaseline along both sides of the barrel on the hinge that the hinge pin goes through. This keeps it epoxy free.

You also might want to consider the "CA" hinges that look like flat, slightly fuzzy plates. You make slits on both control surfaces, slide these in and put a couple of drops of thin CA on both sides in both surfaces. These work really nicely, can give you a real small gap and are really strong - I have used them in planes up to .90 sized.

Finally, there are iron on hinges. These run the entire length of the control surface hinge line. You iron them on to both sides of both control surfaces. Never had a failure with one of these in planes up to 50 cc gas engine types.

Hope that this helps out.

go fly your plane,it will fly fine,sealing the gap will help the plane better,and it's a habit you should do with all planes,I would rather have a gap to seal than have a gap line so tight that it causes a restraint on the movement.

Thanks a milllion for the info. This forum is great and one thing I have found out very quickly, the people you run into in this hobby are among the best. I'm looking forward to many years of enjoyment.

See ya at the field!