Re: Epoxy vs Fiberglass
 

Poly. Repair like with like. I would, however, use epoxy for the aforementioned cloth to wood layup, with a good split coat.i

Re: Epoxy vs Fiberglass
 

minaret yes I agree but still I would use poly for the bulkhead myself.

jedi I do not agree with cloth for the first layer, mat is used as it lays down and fills voids for a better surface fill and gives more surface area for the following layers to attach to if all done wet. Cloth and fabric tend to bridge small gaps and do not lay against the base material as well this can lead to bond failure. No matter the type of resin a layer of csm followed by what ever weave you are using will always work better. That is the purpose of csm in most laminates to fill voids in the weaves that is why it is used between layers of heavier knits as well. You remember the old mat woving mat woving... now in most knits it is part of the material to save time.

Re: Epoxy vs Fiberglass
 

Agreed. This is basic laminating 101.

Re: Epoxy vs Fiberglass
 

You can get cloth to follow voids, ridges etc. but it does not fill them: with epoxy, you have to fill them before applying fabrics, which is what I normally do.

You can use matt but with epoxy it needs to be the stitched matt because the cellulose will fall apart the moment it touches epoxy.
The combinations of matt with woven roving are stitched I believe so they would work with epoxy.

I recently used some matt with epoxy because I couldn't get anything else and it was pretty difficult; you end up with just a ball of fibers with epoxy in your hands. I only needed to stuff it into a void, which was doable, but I could not have put it down as a layer.
There is stitched matt; it is made for use with epoxy and solve the issue. I first do faring and fillets, then start with cloth, roving, cloth. Never had to make anything thicker/stronger than that :thumb:

I used matt, roving, matt with polyester once. I did the layup of the piece on a table with all three layers, wet it out and then put the whole thing in place followed by a plastic foil and piece of plywood screwed in place at each side. That worked pretty well. This was to close the cutout of an escape hatch on a cat, so vertical. It would have been impossible with epoxy and the same fiber layup.

Re: Epoxy vs Fiberglass
 

So if poly is preferred for the reasons cited -- most notably in the case of gelcoat deck repairs where epoxy may make it difficult for new gelcoat to adhere -- can anyone recommend a high-quality poly brand/system that is practical for both small jobs & stowage onboard?

I believe poly & vinylester fairing materials have been recommended by Minaret & others in other threads, but I'm not sure I caught any suggestions for resin & catalyst. Obviously, the quantities pros like Minaret use would not be realistic unless smaller containers are available.

Re: Epoxy vs Fiberglass
 

Here you go: $24 for a quart incl. hardener: TotalBoat Polyester Laminating Resin

:thumb:

Re: Epoxy vs Fiberglass
 

:banghead: Reader be aware!

Re: Epoxy vs Fiberglass
 

You can use matt with epoxy but you have to work around it. Wet down the surface to be covered with epoxy resin. Slap on the matt then put cloth over it and wet the whole thing down. I've also done it laying cloth on a wet out board, putting the matt on top and quickly wetting it out by daubing the epoxy on then picking it up putting in place. Not as easy to work with as Polyester but it can be done. Stitched matt to cloth is by far the easiest to work with, however.

For repairs to the hull, epoxy is the only way. It just sticks to any substrate so much better.

Re: Epoxy vs Fiberglass
 

Poly resin is generally either orthotropic or isotropic. You want the latter, Iso resin. There are many major suppliers and vast differences between products both with poly resin and catalyst, of which there are also many types.

I can currently only speak to west coast suppliers. I am currently using 55 gallon drums of ortho from Revchem for production volume work, and my favorite poly resin, Orca Composites P-17 Iso resin with 480 MEKP or Hi-Point 90, both in drums and by the fiver. Current supplier for most laminating process materials is Fiberlay. They are awesome, Dave even teaches classes for high end industrial processes. P-17 costs me about $200 a fiver, compared to $500 a fiver for WEST. It's great resin. I also get VE Infusion resin from them, and all sorts of other hard to source materials. Good website too, if you know what you're doing.

Re: Epoxy vs Fiberglass
 

If you do repairs to the hull in epoxy, you are forced to finish in paint instead of doing a Gelcoat repair. Why turn a $200 repair into a $20k full paint job? Unless the boat is already painted instead of gelcoated, it makes no sense. Even then I'd only do it for very small repairs, as unless the boat is built in epoxy the dissimilar flex rates will cancel out the superior bonding when considering delam. A big epoxy repair will be much stiffer than the poly hull around it, creating stress risers right at the bond edge of the repair where you don't want it.

Re: Epoxy vs Fiberglass
 

Thanks for that, Jedi.

Re: Epoxy vs Fiberglass
 

OK, thanks.

Re: Epoxy vs Fiberglass
 

I would be very careful buying resin in batches this small. Once promoted, shelf life for poly products is no more than one year. Most products marketed for the amateur user in small containers sit on the shelf for much longer than this, with no "use by" labeling requirements at all. I've said it here many times before, I believe this is where most of the myths concerning difficulty of use of poly resin and especially gelcoat come from. Get your resin from a local industrial fiberglass supplier who sells lots of product. Develop a relationship and they will promote orders for you fresh when you come in the door, even in five or one gallon batches. You will also pay less for a better product. Fresh product makes a huge difference. Buying resin from online or from places like west marine is a recipe for trouble. The lack of packaging dates on poly materials at some sources has angered me for years. If they can't tell you when it was promoted, they don't know what they're talking about and you shouldn't buy it.

Re: Epoxy vs Fiberglass
 

Good reminder. Is this also an issue with epoxy products, such as West Systems?

Re: Epoxy vs Fiberglass
 

No, epoxy shelf lives are much longer.