epoxy lam over koa fins?

General Discussion
1

Just finished making some solid Koa fins and and am ready to laminate them. I’ve glassed wood fins with polyester before and it came out pretty clear but I don’t keep that stuff on hand these days. If I used RR epoxy would they come out more cloudy? I’ve never used epoxy directly over wood.

2

Don’t use Additive F and they should come out fine. Maybe mix some xylene in to help disapate the bubbles.

3

Greg,

Can you give further detail to the use of additiveF? I was under the impression that it was intended to make RR finish clearer.

Is this just in the case of hot coating in humid weather or cold climates? Is it best used in laminating?

I’m in San Diego and I add it to all applications and it seems to finish clear. I’ve never seen cloudy RR.

Thanks,

Josh

4

Sometimes over dark color there can be some cloudiness with Additive F. In dry climates you don’t get very much carbomate blush development … much more in humidity. When you have a lot, you can have delamination between layers and Addtive F tends to reduce or eliminate this. I use Add F all the time unless I’m working with dark colors. Then I tend to not use it and sand between layers or use peel ply on the surface of a laminate and then peel off the peel ply to reveal a nice clean surface to hot coat. For hot coating Add F is indespensible. Sanding before the F days was a nightmare.

5

Thanks Greg. I’ll give that a try.

6

I have found this to help with making the cloth over the fins clearer. I’m sure there are better ways. Glass on dropping temp, or you could cheater coat the koa. I’ve never used that wood before.

  1. cut and layout the cloth on a wet-out table, or epoxy friendly carrier.

  2. use slow with no add-F and saturate the cloth. Just let the resin flow in the cloth. Don’t use a roller on the glass if you don’t have to.

  3. if you have to roll the resin into the cloth, put a film over the glass and use a smooth roller so as not to let much air in. Put cloth on fins when saturated.

    (This is similar to Greg talking about the peel ply)

  4. sand, if necessary, then hotcoat.

I bag my fins now, and that works pretty good. I attached a pic of my first set of balsa/zebrawood fins. You can see a little bit of the milkyness due to me rolling the resin into the cloth as I used fast and add-F.

7

There’s also just a bit of milkiness at the base. Xylene in the resin helps with this. Also you only use 1/2 the amount of fin rope (roving) with epoxy as you do with polyester. The stuff is stronger so you need less. Nice looking fins.