How long before new epoxy goes sailing?

Petrel

Member
I am making West System epoxy repairs to an ABS covered foam boat - mostly to bond the cracked ABS at the stern gunwale (and a bit down to the transom) back onto the polystyrene core. (The manufacturer says that 2-part epoxy is okay with the for this purpose and won't dissolve the polystyrene foam.) I also plan to bond a few 2 ft long areas at the gunwale on either side of the hull as well as seal over a few 1/16th inch cracks in the ABS at the bottom. I'll mend a few indented areas with the same epoxy with a bit of filler added.

The solid cure time (for thin coat) says 6-8 hrs at room temp (70 deg F). On the stern area mentioned above, I'll use a bit more epoxy (not as thin, so should dry faster) and the temperature is between 80 to 85 deg F outside.

Perhaps if I use a hair dryer to speed it up a little if necessary since I don't care about any outgasing bubbles in this instance.

My question is this: How long after the epoxy hardens (so that a fingernail cannot dent it) can I actually put the boat in water?

Thanks.
 
If the epoxy you're using is fresh stock, I'd say just as soon as it's set.

Some curing may continue, but the epoxy is about 98% cured when it's supposed to be. I've never had an issue. A hair dryer will cause it to set faster. Sometimes, you can see white "smoke" arise from it, and it will be hot to the touch).

Probably not good to breathe the "smoke". :eek:
 
Thanks for the feedback, Porpoise.

I'm very new to this and perhaps a bit too ambitious (for some of the SF and other boat repair projects I've lined up. Due to some extenuating circumstances, I'm way behind.

I figured that it was probably okay to use after it hardened, and yes, I will be working outdoors in the breeze and will be careful to not breath any of the vapors or dust.

It feels great to reconnect with the forum. I'd posted a query about my punky sunfish months ago, but couldn't respond because of some server glitch and later extended family situations that needed my attention.

I hate to see the summer winding down (though a New Englander, I don't think of summer as over until frost arrives ;-) ).

BTW, are you "Porpoise" because you own a Porpoise sailboat? Neat name in any case.
 
I hate to say it but forget Marine Tex. It does not work well with ABS plastics. In fact there is not much that will.
While epoxy resins and hardener will not attack stryefoam like polyester resins will, they still do not work well in the long term for ABS repairs.
Most ABS repairs are done with solvent welding using acetone or MEK and if filler is needed ground ABS is added to the solvent to make a paste.
 
For the epoxy repairs if you sand it and it makes fluffy dust go sailing. Mikeabove is right on with the
" ABS repairs are done with solvent welding using acetone or MEK and if filler is needed ground ABS is added to the solvent to make a paste"
But fishes are made with poly resin why fix with more $ epoxy?
A small hole can be glassed, gelcoated and buffed in less then 40 minuntes with poly. (heat gun and every thing lined up)
epoxy is slow, $$$ and not stinky. West system loves you.
 
Wish you would have made the comment about Poly Vs. Epoxy earlier. I have heard that polyester does not bond well to itself, if it has curred for more than 24 hours. One person said the patch will only last 4 years or so. Also that these patches should only be done above the waterline. So, I plan on doing a large polyester patch on my Scorpions tub, but epoxy on the hull.

Does anyone have some long term experience with a Poly patch to argue the four year life statement?
________
Kawasaki ZR750K
 
Thanks, all.
I had fun playing with the stuff, but was glad I had the full array of accessory tools and solutions next to me.

To respond to a few issues brought up in your feedback.

I didn't use polyester resin because, apparently, it and other petroleum-based products dissolve polystyrene or Styrofoam. The "vessel" is an old Super Snark that actually is a lot of fun to sail and will move along with the slightest zephyr. The ABS was cracking and pulling away from the polystyrene foam. The foam and ABS at the transom was falling apart. The current manufacturer's site says that for repairs, use 2-part epoxy such as West System. I also have other boats to fix up, so I bought a good amount of the stuff. I also bought a couple of the Gugeon Brothers booklets or repairing FG boats, blisters, and I downloaded the USER GUIDE and other material -- and read it.

When using the epoxy on fiberglass (FG), they say to clean area with an appropriate cleaner or acetone. The Super (-tired) Snark wasn't FG, but ABS over Styrofoam/polystyrene foam. I've played with nail polish remover and plastic before :eek: and so I was a bit wary about using the acetone on the ABS and also getting it onto any of the exposed Styrofoam. But what the heck. If it dissolved a bit of the ABS plastic, I'd go for the FG tape the next time. I wiped the gunwale, loose, broken and bashed in areas with the acetone. Some blue plastic came off on the cloth, but I kept going because it was making the boat look like new. It was dissolving and re-plasticizing the surface of the ABS. Neat. I did wonder if wiping down the ABS with acetone (all over the bottom of the hull too) might backfire, causing me to witness a crackling and sudden exfoliating of the ABS skin. But I also thought that doing so might make the epoxy adhere better to the ABS. I was slightly gooing up the ABS with acetone, but acetone can also be used to thin epoxy, so I thought I'd get a little "marriage" taking place.

I put epoxy all along the gunwale/rub rail area and let it form a thick film. I mixed a bit of 407 filler into the epoxy to use for filling in some of the bashed and cracked areas. I might touch it up after this sailing season with more of a gyp formulation. I was going to paint the patched hull with LATEX porch paint, but after re-plasticising with the acetone, the hull doesn't look so bad and seems down right new. The epoxy-filler patches look awful, so I'll probably paint those and maybe do the entire hull just to help protect from UV and air pollution.

Next project is PUNKY, the $100 sunfish hull.

Oh, and as for the polyester vs. epoxy for repairing fiberglass hulls like a SF...I too read and have been told that polyester resin doesn't make very good secondary bonds, but that epoxy will bond very well to cured polyester (fiberglass resin). However, if polyester (they say) doesn't bond well to epoxy ("you can put epoxy on top of cured polyester, but not the other way around"), how do folks GEL COAT after using epoxy? Gelcoat is polyester.

I hope I can get the SF hull fixed up enough to play before cold weather (ice) keeps me off the water. Thanks all!
 
From watching folks use "bondo" (automotive polyester body filler) as a repair compound I found the experts were correct. Polyester repair resins are not "waterproof" and in the long run are hydroscopic.
Gel coat is used for two main reasons. It forms a smooth surface (and remember most gelcoat is the first layer in a mold) and even though it is polyester based it serves to waterproof the underlying polyester construction resins. Ask any boat person about "blistering" which is moisture getting between the gelcoat and resin layers and forming delaminated areas that resemble blisters.
The fix is to grind them out and replace with epoxy that will both bond and form a waterproof repair.
As for ABS repairs there is a company that is now producing a specific repair package for ABS using an epoxy resin, but like it was noted; Acetone is added as both a solvent for the ABS and the Epoxy so the two dissimilar materials will actually form a "welded" bond. It's not cheap and not really designed or cost effective for large area repairs.
 
From watching folks use "bondo" (automotive polyester body filler) as a repair compound I found the experts were correct. Polyester repair resins are not "waterproof" and in the long run are hydroscopic.
Gel coat is used for two main reasons. It forms a smooth surface (and remember most gelcoat is the first layer in a mold) and even though it is polyester based it serves to waterproof the underlying polyester construction resins. Ask any boat person about "blistering" which is moisture getting between the gelcoat and resin layers and forming delaminated areas that resemble blisters.
The fix is to grind them out and replace with epoxy that will both bond and form a waterproof repair.
As for ABS repairs there is a company that is now producing a specific repair package for ABS using an epoxy resin, but like it was noted; Acetone is added as both a solvent for the ABS and the Epoxy so the two dissimilar materials will actually form a "welded" bond. It's not cheap and not really designed or cost effective for large area repairs.

Thanks, Mike. You and others have been a big help.
What I meant in my last post was.... Since gelcoat is polyester, how do folks (following the "polyester doesn't bond well to epoxy" logic, get gelcoat to adhere to the epoxy repair?

I've read and heard so much this and that about gelcoat, resin and water. Some sources say that gelcoat is or can per permeable to water, others argue that it is "waterproof." Some say it depends on the thickness and whether or not it's been scratched or sanded. I'm curious, but far from a purist. Although I'd love to own and sail the fairest craft, there's a Yankee pragmatism to my perspective. In my situation, it's also informed by the fact that the old, cheapy hull has more patches than whole sections to it -- albeit a lovely shade of sky blue. The only way my particular $100 hull will have a smooth bottom is if I dip it in hot butter.

Good going on that acetone info and our mind-synch. I hadn't yet read your reply when I went for the acetone welding theory. My mind kept thinking "annealed" (which is close, but not the right term).

Again, thanks a lot, everyone.
Petrel (president elect of the "you can't have enough boats" club.
 

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