flaparon end caps

[Dave S]

Don't actually know what I am in favor of; however, my kit came with the foam blocks and instructions to use the hysol to coat the foam after it is formed to shape. So I used what I had.

Pretty much the same deal Lowell is talking about; and, epoxy primer/aerothane over the whole works resulted in a very nice termination & finishing of the flaperon.

BTW - the aluminum skin of the flaperon is more easily dented than the end foam/hysol finished cap.

The end result is pretty much a matter of how well a person does their bodywork on the end cap before it is painted.

Sincerely,

Dave S
KF7 Trigear
912ULS Warp Drive

[szicree]

On my empennage tips I used foam, fixed any divots with microballoons and then put a layer of very fine glass cloth and epoxy over the works. If you plan on using microballoons be sure to wear a mask when mixing and sanding. The stuff is particularly bad for your lungs.

[inzersv]

I used the foam with the hysol covering and so far am very happy with it. It seems quite strong. And HighWing thanks for some of your heads up in your post. I will be watching for those things. Hope to install my fuel tanks this week or early next. Finishing up my butt ribs and installing my jury struts this week. A note for those who haven't gotten this far; when you back drill the butt ribs to the brackets, don't just start drilling and clecoing from one end. Do one end with one hole and cleco. Go to the opposite end and drill and cleco making sure you are still aligned with the #1 rib. Then finish the rest of the holes.I didn't do this and when I finished I realized that I was almost 1/4 inch out of alignment on the aft end. So, I did as HighWing suggested and filled the holes with hysol, squeegeed with a single edge razor blade, let dry for 48 hours, sanded and then redrilled the way I suggested and everything is aligned.

[jtpitkin06]

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