fiberglass layup ;

[hardcrab]

I understand that the purpose of wax in resin is to seal off air to allow it to fully cure. It is the reason sanding between coats is nessecary to allow adhesion .

When using layup resin (unwaxed), would a final cure be acheived using urethane on the final coat (thus sealing off air) ?

anyone ..... ?
Carter .......?
Carter .......?

[gcarter]

If you're doing a small area repair, where you're laying up 5-8 small pieces, adding wax on the last coat would be ok, but usually you have enough resin to do it all at once. Some here spray wax on the exposed surface after finishing (but I can't remember what it's called).
If you're laying up a large piece (like in the bilge, or hull side) add wax to the resin, and clean the surface of wax after it cures if you're going to add a second course. You may not need to sand if the surface is fairly rough and it's been a short time. If you lay in a large piece and you're going to wait to add a second course, remove the surfaced wax and sand lightly before laying in the next course..
Buy the wax in pint bottles, add it to the resin as you're activating it. This is quite a bit cheaper than having wax added to the resin. Nothing magic about this stuff.
It's darn messy and stinks.

[hardcrab]

thank you George, that is a well explained reply.

in my case, I am picking up an old project ; I reglassed a 13' Whaler (entire surface) 3 years ago. Structurally it is complete.
I used unwaxed (layup) resin, I've wiped it down with acetone and it didn't come up sticky.
I would like to continue with applying urethane on the surface that I have (after cosmetic sanding) rather than go to the expence and effort (and weight) of more resin.
I am guessing the urethane will also act as the finish coat of resin ........... is my assumption valid?

[gcarter]

So, you laid up glass on the "outside", "finished" side of the hull and deck?
Or, just resin on the outside?

[hardcrab]

I used biaxel (?) cloth inside and out, plus taped all the chines, rub rails (had to make, were missing) and wear areas.
The interior was last coated with general purpose (waxed) resin, so that isn't my concern.
The sides and bottom were last coated with layup (unwaxed) resin

76215
76216

[gcarter]

So, what you have to do is "fair" the exterior surface. That can be done w/thickened polyester resin. You can add fillers like micro balloons, and others that are easily sanded.
You can buy long rubber blocks (up to 36", I think) and adhesive paper on rolls to do the fairing with. This is a lot of work.........just so you know.

[hardcrab]

76225

Yeah, I know about the fairing process, I'm actually going to keep the cammo look and not real concerned with a flawless surface.
Supermarine paints have a commercial clear urethane suitable for extended underwater submersion , resistant to gas, solvents, battery acid for 7 days with no effect, UV's ect.

http://www.supermarinepaint.com/default.asp
http://www.supermarinepaint.com/clears-Urethane-sm-2000C.asp

my intention is to sand and clearcoat whats there - assuming the urethane will perform the function of a final coat of waxed resin / which would still need to be sanded and coated with the clear

[gcarter]

You might be prepared for two or three coats of color as raw glass will suck up a bunch of paint. That's one of the important reasons for some finish. I'd at least use some Duratec primer. It'll fill up all the microscopic holes.

[hardcrab]

the basic question I'm wanting to get at is;
is it ok to put the urethane over the resin surface that didn't have wax ? Is the resin fully cured that didn't have wax in it ? Will the urethane act as a final coat to the resin with no wax ?



I'd at least use some Duratec primer. It'll fill up all the microscopic holes.

That's what I wanted to hear !