Epoxy or Polyester, how do you know which?

I saw a suggestion on another thread that said, if you have screw holes or you a going to make any, in your deck, you should drill an oversized hole and fill it with the proper resin, epoxy or polyester. There was no information on how to know which to use. It just said that it had to match what was used on the deck GRP. My question is, how do you know what that is, or how can you find out? Does it really matter? I'm looking at cracks that need repair also. I've never worked with fiberglass before but, I'm up (down?) for learning. I'll try to include a picture.

Epoxy boats are extremely rare due to the high cost of epoxy.
New epoxy will bond to old polyester
New polyester will not bond to old epoxy.

Epoxy has a much better adhesive quality than polyester regardless of the original resin

If in doubt use epoxy.

For repairs I prefer epoxy. It is stronger and will grab onto the old fiberglass better. It is a bit more expensive but it is probably insignificant in the overall scheme of things boating.

Comodave & boatpoker, thanks. Epoxy it is. Takes the guesswork out and, in either case, as long as I use epoxy the end result will be superior to poly.

You can’t go wrong with epoxy if you can afford it.

The problem with epoxy for repairs is if you you want to gel coat over it.

Normally it is not recommended or claimed possible....but West Systems claim it is if you prep it right. Google and look for their online repair manual.

psneeld said:

The problem with epoxy for repairs is if you you want to gel coat over it.

Normally it is not recommended or claimed possible....but West Systems claim it is if you prep it right. Google and look for their online repair manual.

Click to expand...

Just did it Saturday. Bonded in a piece of Coosa board that had 1/4" of fiberglass (polyester) already on it, with West System and bonding filler. After it cured and off gasses (about 5 days), I sanded it and wiped it down with acetone. 2 layers of gelcoat, and the project in the anchor locker is done. No issues with adhesion.



This picture is from 5 years ago when Sean increased the divider height. No adhesion problems.


Ted

I have always avoided it due to the " advice"...wonder if it is just another boating urban myth from people not doing certain or adequate prep? Or it works better with epoxies that cure faster but less or no amine blush?

Curious minds want to know....

I think it comes down to surface prep. Throughly sand off the surface and wipe it down twice with acetone. It works for West System anyway. Can't say whether it works for other epoxies.

Ted

Amine is water soluble, so fresh water will remove.
If the epoxy is clean, sanded and primed with two part primer, gelcoat adhesion is not an issue. One part primer sorta maybe works a bit sometimes.

Thats the rub, West recommends a primer transition, others not.

On the question of filling holes; I use West System epoxy mixed with colloidal thickener (Cabosil) and a small amount of short milled fibers 1/8" mixed to a consistency which won't sag. For a cored area like foam or balsa core I prefer not to over-drill the hole but instead use a bent nail in a drill to ream out the core inside the skin, over-drilling just enough to get out the waste core. A vacuum on the opposite side of the hole from where you insert the nail helps to remove debris. Then load epoxy mix into a syringe and inject into the hole.

Regarding amine blush, soap and water cleanup after BEFORE any sanding or better yet, use a layer of peel ply which will allow you to strip the amine blush off without cleaning. Never had an issue with gelcoat over epoxy.

For filling holes, the West Six10 works really well. Caulking tube dispensed, long cure time, will not run out of a hole even overhead. It is pre-thickened. The only downsides of it are it is relatively expensive, and the shelf life it about a year (then is starts to go lumpy).

I use to build epoxy boats and had no problem with gelcoats. Also no blisters or delamination problems, even in major collisions. Epoxy bonds to anything better than poly.
For screws in wood, fiberglass, or fiberglass cored boats I use West 404 high density filler. Besides strength it also helps adhesion. Screws hold better to epoxy than to any other material.
For setting screws, I drill an oversized hole and fill with West epoxy and 404 mix. The hole is deeper than the screw length. Later I drill a pilot hole slightly larger than I would for wood or fiberglass because the threads don't penetrate the much harder epoxy as well. When I drive the screw, I put a small amount of epoxy down the hole as a lube. The screw is bonded to and encased in epoxy. Water will never weep down the threads. Items like stanchions, properly done, will never become loose again. To remove the screw later may require a small impact tool. The tool I use to drive screws has an impact function.
When setting in epoxy, you don't need a screw as long or as big as would be used without epoxy.

Lepke said:

I use to build epoxy boats and had no problem with gelcoats. Also no blisters or delamination problems, even in major collisions. Epoxy bonds to anything better than poly.
For screws in wood, fiberglass, or fiberglass cored boats I use West 404 high density filler. Besides strength it also helps adhesion. Screws hold better to epoxy than to any other material.
For setting screws, I drill an oversized hole and fill with West epoxy and 404 mix. The hole is deeper than the screw length. Later I drill a pilot hole slightly larger than I would for wood or fiberglass because the threads don't penetrate the much harder epoxy as well. When I drive the screw, I put a small amount of epoxy down the hole as a lube. The screw is bonded to and encased in epoxy. Water will never weep down the threads. Items like stanchions, properly done, will never become loose again. To remove the screw later may require a small impact tool. The tool I use to drive screws has an impact function.
When setting in epoxy, you don't need a screw as long or as big as would be used without epoxy.

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Lepke,


Do you mix the 404 in the epoxy? I use West GFlex for about 95% of my epoxy projects, fill, screwholes, deep dings in the gel coat. However, by it self, it's hard to sand and smooth for a coat of gel coat. It has a brownish tint to it and takes several layers of gel coat to cover. To make it easier I use a product called Evercoat Formula 27, a toothpaste consistency light filler that is solid white and really easy to sand, and then gel coat over that.


Was thinking, perhaps the 404 (which is white) mixed in the epoxy might work better? Comments?


BTW, I've also tried adding a white pigment to the epoxy but doesn't work real well. Still hard to sand, but requires fewer gel coats.

Polyester has some cohesiveness and very poor adhesion but is cheaper than epoxy.
Epoxy has great cohesiveness and very good adhesion but costs more.
I use Epoxy in almost every instance.
To me polyester is a good filler.

Timely. Thanks for the input from those with the nuance.

I’m about scope a winter project of building a new transom door. Will probably do epoxy with gel as soon as I figure out how to replicate all the compound curves. But that will come later.

Lepke said:

I use to build epoxy boats and had no problem with gelcoats. Also no blisters or delamination problems, even in major collisions. Epoxy bonds to anything better than poly.
For screws in wood, fiberglass, or fiberglass cored boats I use West 404 high density filler. Besides strength it also helps adhesion. Screws hold better to epoxy than to any other material.
For setting screws, I drill an oversized hole and fill with West epoxy and 404 mix. The hole is deeper than the screw length. Later I drill a pilot hole slightly larger than I would for wood or fiberglass because the threads don't penetrate the much harder epoxy as well. When I drive the screw, I put a small amount of epoxy down the hole as a lube. The screw is bonded to and encased in epoxy. Water will never weep down the threads. Items like stanchions, properly done, will never become loose again. To remove the screw later may require a small impact tool. The tool I use to drive screws has an impact function.
When setting in epoxy, you don't need a screw as long or as big as would be used without epoxy.

Click to expand...

Thanks Lepke great explanation - just to take this a bit further -is it possible/practical to drill and tap a plug such as you describe and use a course thread machine screw?

Seevee said:

Lepke,


Do you mix the 404 in the epoxy? I use West GFlex for about 95% of my epoxy projects, fill, screwholes, deep dings in the gel coat. However, by it self, it's hard to sand and smooth for a coat of gel coat. It has a brownish tint to it and takes several layers of gel coat to cover. To make it easier I use a product called Evercoat Formula 27, a toothpaste consistency light filler that is solid white and really easy to sand, and then gel coat over that.


Was thinking, perhaps the 404 (which is white) mixed in the epoxy might work better? Comments?


BTW, I've also tried adding a white pigment to the epoxy but doesn't work real well. Still hard to sand, but requires fewer gel coats.

Click to expand...

404 in epoxy is a very light tan. You can mix 404 anywhere from a little to putty-like. For small batches I use a drill and a small paint mixer. I found for mixing color in epoxy, you need more color than in poly. West epoxy with 404 seems to be immune to UV in cases where I left the epoxy exposed to sunlight for a couple years. I have vacuum sanding tools and don't find sanding epoxy noticeably different. And I probably use much coarser grit than most people. I usually start with 40.

A somewhat recent experience, I'm in my 70s now, I hired a house deck fiberglasser (son of a friend). I have an old, large wood boat with plywood over the original planked deck. (Not a good idea to hire a house anything to work on a boat) But I let him do part of reglassing the deck. When I do fiberglass over decks, mostly on commercial boats, I do an overlap so no hull flexing causes cracks where they joined. I didn't supervise and came back to find butt joints.

I use to be a fisherman and I go out in big waves in the PNW and my hull flexes. In big waves, if you have your eye near the deck on the stern and look towards the bow, you can see the main deck flex about a foot. All the butt joints near midships cracked. As a temporary fix I ground out the cracks, mixed West epoxy and 404, and filled. Meaning to come back and install an overlap patch. But I didn't get to it for a couple years and in the meantime managed to be in some waves larger than the ones the made the original cracks. But all my fixed joints held and didn't crack. If I hadn't been sold on 404, I would be now.

The boat came with poly fiberglass and cloth decks and cabin tops. To remove the old glass, I picked up a corner near the stem and ripped the whole deck off, the foc'sle, the sides and stern in one continuous piece. Just cutting the waste to a manageable size as I went down the deck. About a 30 minute job, plus clean up, no power tools, on an 83' boat, by an old man. So much for poly holding quality. And I did the same many times, the same way, when I had a yard, redoing decks done by some poly yard. Poly doesn't stick good to anything, including itself.

So much to learn...

A lot of great information here. I'll start with the West videos/tutorials and find something disposable to practice on before tackling the cracks. I'm going to put a couple of "C" clamps (with 2x4 buffers) on the areas to see if they will need to be repaired under pressure or just filled.

That crack looks like it has a lot of movement. Are you sure it is sound underneath?

ghost said:

That crack looks like it has a lot of movement. Are you sure it is sound underneath?

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It seems to be, and the surveyor said it was and that it was probably caused by an event with the Bullfrog dink w/20 HP Yamaha sitting up there. Just to keep an eye on it and repair if necessary. I would like to do it right away just to keep any moisture from getting in there. If you enlarge the indicated area you will see the cracks.

BTW, it's in Anacortes and I have to run up from Kirkland.

Looking at your post #1. The cracks on the corners look pretty bad. I think that I would grind them and lay in at least 1 layer of 1708 glass to reinforce the area so the crack won’t just come back. I use Roloc sanding disks on a right angle drill to do the grinding and it goes pretty quickly. I think the Roloc disks are either 40 or 50 grit. It may be a bit difficult to get the sharp corner if you put on a layer of 1708 but you could build the sharp corner out of thickened epoxy after the glass. I also use a lot of 404 filler for something like that.

Comodave said:

You can’t go wrong with epoxy if you can afford it.

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If you can afford a discretionary item like a boat you can afford the few dollars extra for epoxy.

It doesn't have to be west system, I stopped using west half way through my first build in favour of brands that do the same job for a lot less.

Think Apple and Android, both make phones, both make phone calls but one costs $40 and the other a hell of a lot more.

Comodave said:

Looking at your post #1. The cracks on the corners look pretty bad. I think that I would grind them and lay in at least 1 layer of 1708 glass to reinforce the area so the crack won’t just come back. I use Roloc sanding disks on a right angle drill to do the grinding and it goes pretty quickly. I think the Roloc disks are either 40 or 50 grit. It may be a bit difficult to get the sharp corner if you put on a layer of 1708 but you could build the sharp corner out of thickened epoxy after the glass. I also use a lot of 404 filler for something like that.

Click to expand...

In Anacortes, is this an acceptable time of year to do that kind of work? I can keep that flybridge hatch closed to protect it. Or will it be too cool and damp to do the work? Shows what I know about resin set-up and all that fiberglassing stuff. I'm also doing the main engine exhaust hoses (original) replacement and generator exhaust system (including wet stack muffler). So my life is going to be pretty busy. I'm excited to jump in though. I couldn't find any threads about replacing the exhaust hoses in a Defever 44 in this forum or the Defever Cruisers forum. I may have to contract that.

I'm going to watch some fiberglass repair videos tomorrow. That should give me a good idea of how to prioritize my time. The small stuff, like replacing twist on connectors with butt crimped adhesive shrink-wrapped connectors, defective horn button, a gauge reading about 10 degrees low, and a few other small things like that (I know, they add up) should be within my current skill set. Oh yeah, my wife demands a Splendide washer/dryer (vented) installation. Just heavy lifting, no sweat :lol:.

Simi 60 said:

If you can afford a discretionary item like a boat you can afford the few dollars extra for epoxy.

It doesn't have to be west system, I stopped using west half way through my first build in favour of brands that do the same job for a lot less.

Think Apple and Android, both make phones, both make phone calls but one costs $40 and the other a hell of a lot more.

Click to expand...

It's not really a discretionary item. It will be our home, so, yeah definitely epoxy. I'm not just going to throw a blue tarp over the boat and call it good to go. I'm really open to using quality stuff and not wedded to West. If there are any you care to recommend that are available in the U.S.A., please do.

jbloyd said:

In Anacortes, is this an acceptable time of year to do that kind of work? I can keep that flybridge hatch closed to protect it. Or will it be too cool and damp to do the work? Shows what I know about resin set-up and all that fiberglassing stuff. I'm also doing the main engine exhaust hoses (original) replacement and generator exhaust system (including wet stack muffler). So my life is going to be pretty busy. I'm excited to jump in though. I couldn't find any threads about replacing the exhaust hoses in a Defever 44 in this forum or the Defever Cruisers forum. I may have to contract that.

I'm going to watch some fiberglass repair videos tomorrow. That should give me a good idea of how to prioritize my time. The small stuff, like replacing twist on connectors with butt crimped adhesive shrink-wrapped connectors, defective horn button, a gauge reading about 10 degrees low, and a few other small things like that (I know, they add up) should be within my current skill set. Oh yeah, my wife demands a Splendide washer/dryer (vented) installation. Just heavy lifting, no sweat :lol:.

Click to expand...

I use the fast hardener with West epoxy. It is supposed to work down to 40 degrees. Although I have used it during the winter here down into the 20s without any problems. West says no problem as the epoxy will just wait until it gets warmer and then go off. But mine has gone off when it has been in the low 30s. Look at Boat Works Today web site. He has lots of fiberglass videos. Although he mostly uses polyester resin instead of epoxy since he is trying to save money as a professional. But the same methods work with epoxy. Some epoxies develop an amine blush when they go off so you have to wash it with water after it goes off and before sanding. I use a scrub brush and water. So you can probably do the work in the PNW in the winter if the temps are in the 30s or above. Good luck.

As to the exhaust hose replacement, there was an extensive thread recently about that. Another newbie was asking about it. What part needs replacing? If it is just the rubber hose then it is pretty easy technically just grunt work getting the large hose in and hooked up. If the boat is in the water depending on whether the exhaust is in the water or not makes a big difference. If the exhaust is in the water then you need to plug the through hull exhaust or get the boat to list to the other side. Someone said they used an inflatable ball and put it in the exhaust fitting in the transom and inflated it so the water could not get in. Then did the hose. Search for the thread, maybe last month or so.

Comodave said:

As to the exhaust hose replacement, there was an extensive thread recently about that. Another newbie was asking about it. What part needs replacing? If it is just the rubber hose then it is pretty easy technically just grunt work getting the large hose in and hooked up. If the boat is in the water depending on whether the exhaust is in the water or not makes a big difference. If the exhaust is in the water then you need to plug the through hull exhaust or get the boat to list to the other side. Someone said they used an inflatable ball and put it in the exhaust fitting in the transom and inflated it so the water could not get in. Then did the hose. Search for the thread, maybe last month or so.

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Found the thread. Yep, just the hoses. On the hard. Groan,... I'm 75 yrs old and small. Think I'll hire some help.

I understand your feelings. I really wanted to buy a different and much bigger boat, but I am not as able to do all the work I would want to do on it. So I guess we will stick with the current boat. Good luck with the work.