Noklin Posted April 21, 2009 Report Share Posted April 21, 2009 I have seen post from several other people that indicated they have run into the same problem because of incorrect ratio or poor mixing, but I am not sure how they corrected the problem. The up side is that this happened on a honey-do-job and not on the CS20. I figured this group would be the best place to find out what I needed to do. I have a small area of glassed material that is dry to the touch but every time I attempt to sand it clogs the sandpaper in large lumps. The area around it is fully cured. The coating below the glass was fine. I have scrapped the fill coats off down to the glass, but am not sure how to proceed. It has been a month now with temperatures in the 80s so I believe that if it was going to cure it would have by now. Do I need to scrap the area down to bare wood and totally redo it? Since the coating below the glass was cured, do I only need to remove the glass and rework it from there or would the bad coat have damaged the cured coat? Can I cover this area with a proper mixture and expect it to cure properly? I believe that the wet out coat was the problem and that the other two fill coats were correct, but did not cure properly because of the fill coat. So I do not think this is a real option. Can I ignore the problem and paint over it or will the uncured epoxy cause problems with the paint. Quote Link to comment Share on other sites More sharing options...
sscoville Posted April 21, 2009 Report Share Posted April 21, 2009 All I can tell you is what I've experienced. I applied epoxy at the wrong ratio when glassing the hull of my first boat. I thought it had cured, even though I realized I had mixed wrong. I put a second coat over it. Then, when popping some small air bubbles later, the glass started coming up in big strips - almost no adhesion to the wood. So I pulled all the glass up. I tried to sand the bad goo off, but all it seemed to do was move it around. I thought I had removed it all and so re glassed and filled. A week later, when I was about to prime, I found a large air bubble and when I tried to cut it out, the glass came up in strips again. I had not gotten all the bad stuff off. I called the tech people as MAS - which was the stuff I was using - and they told me 1. I could use lacquer thinner to remove it. I tried that but it wasn't doing much. Finally, I found the solution - 7 in 36 grit grinding disc on sander/polisher - this was the only thing I found that worked to completely remove the goo back to the bare wood. The goo clogged the 7 in discs like the finer ones I had tried before, but not nearly so easily. I did grind too far into the wood in some spots, but I was painting over it anyway and so did not care. Uncured epoxy is a real nightmare. I have since learned to use the same grinder and 36 grit disc to cut my scarf joints. Very efficient here too. Quote Link to comment Share on other sites More sharing options...
Ken_Potts Posted April 21, 2009 Report Share Posted April 21, 2009 If you do end up finding gooey stuff under the fill coat, vinegar seems to clean it up pretty well. Quote Link to comment Share on other sites More sharing options...
Tom Lathrop Posted April 21, 2009 Report Share Posted April 21, 2009 A coat of uncured epoxy simply has to be removed however you do it. One best way (if you don't mind chemicals) is with paint remover which, in the strong ones, is methlene chloride. I use Stripeeze. Brush on a heavy coat of the thick variety and cover the area with a sheet of plastic to keep the air out and let it work longer. Let sit for a couple hours or more. After getting all that will come off by scraping, treat it like any other paint removal job. At some time all of us have to learn how to do this. Quote Link to comment Share on other sites More sharing options...
sscoville Posted April 22, 2009 Report Share Posted April 22, 2009 I hope I never have to again, but if I do, I'll have to remember your technique, Tom. I tried laquer thinner and another much more volatile chemical, the name of which I can't remember, and vinegar. None of them seemed to help much. I may not have left them on long enough to work. Quote Link to comment Share on other sites More sharing options...
Ken_Potts Posted April 22, 2009 Report Share Posted April 22, 2009 I've only tried vinegar on the gooey stuff - Not the stuff that's hard but still gums up the sandpaper. I'm not surprised it didn't work in your case, I just mentioned it in case you found gooey stuff under the top layers. Quote Link to comment Share on other sites More sharing options...
Tim Posted April 22, 2009 Report Share Posted April 22, 2009 Yeah I tried the vinegar without any luck. I had a fairly large area so I scrapped as much goo off as possible with a paint scrapper. It was impossible for me to get it all up. So then went back with another coat of epoxy with a little extra part B in it since I figured that was what was short on the gooey batch. Hard as a rock now. Quote Link to comment Share on other sites More sharing options...
Joel B Posted April 22, 2009 Report Share Posted April 22, 2009 I once mixed the wrong hardner and had to rework a very expensive carbon fiber mold. We used acetone or mek but i don't think either would be readily available for non industrial types. I like Tom's idea best Joel Quote Link to comment Share on other sites More sharing options...
Hirilonde Posted April 22, 2009 Report Share Posted April 22, 2009 Acetone can be found at any hardware store. It is relatively inert and safe. I wouldn't use MEK even if you could find it. It is totally unnecessary and more hazardous to ones health. Definitely do not use MEKP. Quote Link to comment Share on other sites More sharing options...
sscoville Posted April 22, 2009 Report Share Posted April 22, 2009 Acetone was the other chemical I used. Unless I needed to leave it on longer, it didn't work for me. Quote Link to comment Share on other sites More sharing options...
Tom Lathrop Posted April 22, 2009 Report Share Posted April 22, 2009 [quote author=Hirilond Quote Link to comment Share on other sites More sharing options...
Hirilonde Posted April 22, 2009 Report Share Posted April 22, 2009 MEKP? Been messing with polyester have ye? Not me, but I work in boatyards, so it is used around me a lot. It is also used as a solvent, but you won't catch me using it as such. I'll just throw what ever needs it away instead. Quote Link to comment Share on other sites More sharing options...
Noklin Posted April 23, 2009 Author Report Share Posted April 23, 2009 Since it sounds like I will have to rework the bad area anyway, I think I will try some experiments. I plan on trying a light coat of Part B over part of the bad area. Another part of the bad area will have a good batch of epoxy applied to see if it will cure properly. The bad area appears hard and dry, it only showed up when I tried to sand it down. Might as well learn as much as possible from the problem in addition to what I have to do to fix it. I had let my 12 year old grandson mix the epoxy that had been applied. He had helped me when we glassed the CS20. We are not sure what went wrong with this batch. Thanks for all of the suggestions. Quote Link to comment Share on other sites More sharing options...
Ken_Potts Posted April 23, 2009 Report Share Posted April 23, 2009 I'm working from my years-old memory of the West System website so I may have things wrong, but: If you mix the epoxy with too much hardener (part the epoxy wil not cure. Too much hardener prevents the molecules of resin from linking or something like that. If you mix too much of the resin (part A) you will get brittle epoxy (I don't remember why). The proper cure of epoxy is very dependant on the ratio of hardener to resin and the skim coat of hardener will make that ratio almost impossible to achieve - It'll be a crap-shoot. My guess (not from my memory of West Systems website) is that if you start with epoxy that didn't cure properly and try to fix it you aren't going to do anything but end up with what you've already got plus a coat of uncured hardener. If you're dead set on doing the experiment of applying the light coat of hardener I hope I'm proven wrong. Keep us posted - I'm always happy to hear a new way to fix my (numerous) mistakes. Otherwise, try to get all of the bad stuff cleared off your boat before proceeding. I know it's a pain, but I think the experiment may well make things worse. At least take a look at the West Systems (or raka or whoever) faq on curing problems before you proceed. Quote Link to comment Share on other sites More sharing options...
Hirilonde Posted April 23, 2009 Report Share Posted April 23, 2009 Even if you succeed in making the surface seem hard and cured will you know what you have underneath? Will your experiment be properly bonded to the wood? I have a funny feeling you will discover the answers to these questions months later while sailing, or upon returning from sailing. I suggest you bite the bullet and do what ever it takes to remove the mess now. Save your experiments for scraps of wood. Quote Link to comment Share on other sites More sharing options...
Noklin Posted April 23, 2009 Author Report Share Posted April 23, 2009 As I indicated in my original post, the only good thing about this situation is that the problem in not on the CS20, but a conversion unit to make my boat trailer into a utility trailer. I am using Fir ply and covering it with glass to prevent checking and to improve its resistance to stone chips and other road damage. Not sure that it is worth the trouble, but having the material laying around, I find the bare plan tends to take on a life of its own. So if it causes trouble later down the road it will still be no big deal. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.