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Flaperon help needed

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Posted

Looking for some advice on how to seal the flaperons.   The manual states that the foam within the aluminum skin needs to be sealed.   There are 3 areas that need to be sealed by the looks of things.  The butt and tip ends of the flaperon and the upper and lower holes where each hinge attach bracket is located.  How do you go about sealing this??

I'm open to suggestions!

Thanks

Mark

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Posted

I used a mixture of Epoxy, flox and micro balloons which makes a body putt like filler.

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Posted

Balsa w/ epoxy varnish or foam w/ Hysol or epoxy. Here's a cut n' paste:

Yes, the foam supplied in the kit may be coated with polyester resin. You may also use Hysol and micro balloons or just about any other resin or epoxy. Even Bondo will not attack the foam.

There are many ways to shape and strengthen the end caps on the flight controls. Here is but one method.

Tape the last four to six inches of the flaperons to protect the ends from scratches and to keep resins and fillers from getting on the outer aluminum surface.

Press a block of foam on the end of the flaperon and make a line for cutting out the block on a band saw. Then insert the semi-shaped block into the end of the flaperon. Inserting the block about 1/2 inch is plenty. I used five minute epoxy to bond the block in place. Using a sanding block shape the tip to match the airfoil and contour the tip as desired. I made the foam airfoil about 1/16 inch undersize to compensate for the resin to be added.

Next I mixed up a batch of resin and micro balloons as a filler. I prefer epoxy or polyester resins over the Hysol when mixing up fillers due to Hysol’s slow cure time. I like to get in and get it done. 

You can get micro balloons at most marine stores. I mix it pretty thick like Bondo so it doesn’t sag. After the filler is slathered on I removed the tape and cleaned up any smeared resin slop. It’s much easier to remove the slop before it cures. After the resin cured I added fresh masking tape for sanding protection. Then I sanded the surface to match the airfoil and make it smooth. The first coat had a few pits and holes that were easy to fill and sand on the final resin coat.

The resin penetrates the surface of the foam quite deeply giving the finished product a lot of strength. True, raw foam dents easily, but resin coated foam is very strong and lightweight.

When you mix up a batch to coat the foam, put some extra resin on a scrap piece of foam. When you are done, you can do a little “destructive testing” on the scrap. You’ll be surprised how strong the coated foam becomes and how much the resin penetrates.

John Pitkin
Greenville, TX

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