Robust Rounded Fin Technique

[GregGleason]

One of the things that can happen to fins is the ding on the leading and trailing edge.

In my quest to make my fins more ding resistant on the leading and trailing edges, is the addition of solid carbon rods from RC Foam.

For example on my latest build, it is 1/8" (0.125") thick balsa sheet, purchased at Hobby Lobby. So nothing special there.

I printed out the fin pattern, and tack it to the balsa using 3M Super 77 adhesive spray. After cutting it out, I did the match shaping with sandpaper. I did use some laminating epoxy (I used Aeropoxy PR2032/PH3665), to put 2 layers of ~6 oz. FG on each side of the balsa core, and put it between two glass panes (glued to MDF) with the parchment paper between the glass and layup. Then I put a weight on top and let it cure. The fins come out nice and planer, with a fairly good surface, too.

I leave about a 1/16" fiberglass edge on the leading/trailing edge of the fins, that serve as a "trough" of sorts for the carbon fiber rod to rest in. Then I use a good adhesive epoxy (I used Aeropoxy ES6209) to attach the rods to the fins. I then wipe away the excess epoxy, then tape down the rod to the fin with blue tape. I then set it aside to cure for 24/48 hours.

Here are the fins after the cure and blending.



Greg

 

[GregGleason]

Here are the fins after the application of the Trim MonoKote.



Greg

 

[les]

very nice

 

[powderburner]

You can also use bamboo----

Not as exotic as carbon fiber rod, but a lot cheaper, and still very tough and very light. You can usually find a supply of bamboo skewers in various diameters at your local grocery stores and "dollar" stores.

 

[GregGleason]

Good ideas!

Greg

 

[powderburner]

I might point out that this sort of reinforcement can work well on the trailing edges of balsa fins, to toughen them against landing damage.