gel refuses to go off

[Nessa]

I don't normally have problems with gel coat, but this one, isn't just ordinary gel, it's l***r gel, and therefore came with no instructions, mix ratios, in fact nothing at all helpful. I emailed them to ask, but nada. I asked on Y&Y (not wanting to mention the L word in these hallowed halls) and follwed their advice. The result is that I have a boat that dare not mention its name sitting in the garden with some very half hearted half tacky gel on its various wounds. What's a girl to do? Scrape it off and start again?

Obviously I have learend my lesson with my poor taste in boat and gel buying, but too late....

[Rupert]

How old is the gel coat and/or hardener? I had this problem recently with RS gelcoat, and in the end decided it must be age, as I couldn't see it could be anything else. I don't think gelcoat knows what sort of boat it is being put onto...

[Nessa]

It is all new - fresh (?) from laser performance so I could get the colour match. The catalyst comes from Blue Gee (thought bought from laser, at the same time as the gel.) The gel is in a non descript laser bottle.

[Ed]

Well.....whatever caused it....we have all been there, so don't worry too much.

Polyester resin does seem a bit sensitive at times.....to both age, temperature, ratio etc. Epoxy seems to be happier to go off.....but I suspect with a quick fall-off in strength if it ain't quite right.

First, the ratios are temp dependent and they always seem to presume that you are working inside.....or on a hot summer's day. So, if you are working outside in September, it is likely that you need a bit more Catalyst than they suggest.....

I don't use polyester much.....but it is normally 1-2% for laminating resin (can't remember exactly for gel-coat, but would expect it to be the same), but I would stick to a heavy 2%. If they give no advice at all.....the old adage of a 'pea' to a 'golfball' seems to work about right. Then I normally try to do a test first, just to make sure it goes off and within a reasonable time. You can then adjust dependent on your tests.

Anyway....what do you do?

First, put it out in the sun for a day, or put a black bin liner over it......or VERY gently warm it up a bit with hot air. Hopefully this will make the reaction kick in.....but if not....

then, if it is still low, below the final level.....you 'can' try putting some new gel-coat over the top (with a little more Cat in it) I have known some people say that the new layer reacting will start the other stuff going. Personally, I don't like this approach and if it does get the other stuff to 'go' it is likely to be simply due to the heat produced by the 2nd batch.

Or....you have to do it properly and pull out all the stuff that hasn't set.....clean it and re-abrade and start again. Quite a horrible job if done well!

At least it will give you plenty of time to reflect on that old advice: "Always try on a small area first"

Good luck and tell us how it goes.

Personally, I have always found working with polyester gel-coat to be very hard to do well. in my humble opinion it is much easier to fill the damage with epoxy/filler guck and sand to shape and then find a matching spray paint and polish out.

cheers

eib

[Nigel]

If all is lost anyway, try applying a hot air gun (fairly gently). It has worked for me in the past for bridging filler that was stubbonly refusing to go off

[ICLYM]

Try another mix, apply and stick sellotape or similar film over the gel. It should go off then. Me thinks L.... been saving money again and forgotten to add wax in styrene to the gel!

[Rupert]

It should go off without MW solution (wax) though, but the surface will feel sticky still, where it has been in contact with the air. Worth checking this isn't what has happened? This is where covering with tape comes in, to keep the air off.

[Nessa]

Interestingly, the only bit that did go off was the bit I'd put under mylar tape. I have now painstakingly cleaned it, and fear I may smell of nasty chemicals for the rest of my life. I'm now very tempted to go to the local boatyard, buy some slow hardener and go for Ed's suggestion. It might not be pretty, but I want the thing out of the garden and on the water...

[Nessa]

Right, I did it again and thanks to improved atmospheric conditions it has pretty much gone off, bar a slight tackiness, some of which I think is glue from the the tape. I can't sand it like this - well, I could but it would be nasty - so should I try giving it some heat to finish off? Or try finely scraping off the top layer?

[Ed]

What you are describing.....does sound more and more like the resin didn't have any MW solution (Parafin Wax) in it. Gel Coat does normally have it.....but not always, if it was made to go in a 'mould' rather than for 'fixing' then it wouldn't have it as the mould keeps the oxygen off anyway.

Without it, the surface of the resin remains sticky due to being exposed to the air.

Best way around this is to always either add a little extra....or wrap some plastic or mylar sheet around the damage and this will peel off to leave no stickyness. Some use brown tape upside down....then wrap it tight with more tape the right way up.

If this is the problem.....not sure what will take the tackyness away.....maybe a thin coat of a paint, but this rather defeats the purpose of the gel coat in the first place.

tell us what works best.

eib