Why hotcoat a fin panel?

General Discussion
1

Looking through the archives, I notice that most people say you should hotcoat a fin panel before foiling.

After foiling 5 fins and skipping the pre-foiling hotcoat, I’m wondering what’s the reasoning? You’re just going to grind it off anyway.

2

I think it’s done so if you use poly lam resin it dries tacky on the surface. To make it easier to sand and not gum up your sandpaper, you hotcoat it. Other than that, really no point. And with epoxy, completely unnecessary. Or you can do what I do, lay a piece of wax paper on top of the glass to seal out the air.

3

did you know that before surfacing agent , they used to shred up parafin wax and mix it into the lam resin as a surfacing agent

Ive tried it and it works

4
Quote:
I think it's done so if you use poly lam resin it dries tacky on the surface. To make it easier to sand and not gum up your sandpaper, you hotcoat it. Other than that, really no point. And with epoxy, completely unnecessary. Or you can do what I do, lay a piece of wax paper on top of the glass to seal out the air.

Still not getting the logic… once you begin foiling the fin, that hotcoat comes off and you’re left with the same thing as before: cloth and lam resin.

5
Quote:
did you know that before surfacing agent ,, they used to shred up parafin wax and mix it into the lam resin as a surfacing agent

Ive tried it and it works

and it works the same? can you tell me a little more?

6

I never saw the point, and never did it.

The fins turn out fine.

7

Lam resin is only tacky when exposed to air. So the resin under any of the other layers is tack-free. It’s only the top layer that is tacky.

8

Im sorry I cant elaborate much on the parafin thing

As I see it maybe about a teaspoon of very small flakes of wax blended with 12 oz or so of poly resin

the wax slowly melts into the resin then catalize and coat

the wax will rise to the surface an smother the resin so it cures sandable

I think surfacing agent is styrene and parafin wax blended

You can use lam resin and after it sets and is tacky rub wax on it and the next day it will be sandable

not the correct way but if you f up the surfacing agent quantity it can be saved by rubbing the board with waxI have also coated a bad sand coat with resin dust and it helped to sand

9

thanks ken, gonna have to try that.

10

Allways do a test pannel

Im also in so cal so its usualy about 72 to 80 degres out

that may help

11

I thought surfacing agent was paraffin wax. With styrene that is.

12

it is, perhaps the styrene just keeps it in liquid form?

13

Howzit SAsolitude, I use a simple process. I lay down wax paper on the surface of what ever you use for the lay up process and then when I do the last layer I lay down wax paper on the top of the lammed glass. Now you have a sandable surface with out using a sanding coat, works for me, but to each his own.Aloha,Kokua