The Vacationer plans call for fiberglass mat for the hull bottom up to the lower rub rail. I've worked with fiberglass cloth a lot on other boats but never mat. So I do a little research that says poly resins are preferred for mat and not to use epoxy, huh? I want to epoxy encapsulate and use epoxy as much as I can in the construction. So whats the deal with mat? Can I lay the mat with poly and then cover it with cloth using epoxy? I need some guidance here as I want to use the best and most durable materials.
If I epoxy saturate the hull wood and let it cure, can I come over it with mat using poly resin????
Pick a resin system, you have three to choose from. Polyester is called for in the plans, but honestly, it's not the best stuff you can use and it's difficult to work with compared to epoxy. Vinylester is another better option, but it rivals epoxy in price, is more difficult to work with and doesn't have the performance of epoxy. This leaves epoxy. Hands down, without exception among industry professionals, epoxy is the choice on wood. It's easier to work with, doesn't have noxious fumes, is a lot stronger, is much more water proof, the list goes on and on.
If you want to encapsulate with epoxy, then this is the resin system you'll use and you will not have need for polyester or vinylester resins. Since you'll be using epoxy, you also don't need mat. Mat is a bulking agent used with the weaker resin systems, to help create a physically interlocked resin matrix. Epoxy does this naturally, so you don't need the mechanical help of mat products, so skip the mat.
So, to sheath your hull, you'll encapsulate the wood first, then cover the hull with 'glass cloth (or other proprietary fabric like Dynel or Xynole), which is of course set in epoxy resin. The most durable hull coating is Xynole set in epoxy, though be warned, it drinks up epoxy resin like a sailor on liberty.
Cloth, set in epoxy will offer considerable abrasion resistance to the hull shell. In the fabric weights typically used, you'll gain no additional strength. Dynel fabric is specifically intended to improve abrasion resistance on surfaces. It costs a little more then 'glass cloth of similar weight (about 20%), but is 3 times better at abrasion resistance. Unfortunately, it uses about 3 times more resin to apply too. Xynole is another fabric designed for abrasion resistance and is about 6 times better then similar weight 'glass cloth. This fabric also drinks up about 3 times the resin compared to regular cloth and costs around $9.50 to $10 a yard. If you have some 'glassing experience Xynole or Dynel are the products to consider. They are slightly more difficult to apply, but conform to odd surfaces better and are a lot more durable then regular cloth.
 Thank You Paul! Glad to hear mat is not needed!
I used two layers of 10 oz fibreglass cloth, pinned on the hull. I spread the epoxy on with a plastic auto body style spreader. Removing the pins as the cloth stays in place on the hull. Best to have a helper mix batches as you apply them. I had a 5 gal epoxy kit, it was enough for the hull, had to get 2-3 more gal for the rest of the boat, (cockpit, and topside)Â DON"T use mat, it will cause plenty of grief, with epoxy. The Vacationer is a big job, budget most of the day to glass the hull. My helper and I took 7 straight hours.
Greg
Two layers of 10 ounce cloth is a lot more then typical or necessary, so Greg's boat is on the bullet proof side. You can use mat, it will not hurt anything, it just will suck up lots of resin and not offer as much abrasion resistance. The "sizing" used to bond the fibers in the mat is styrene soluble, which works well with polyester and vinylester resins. It will remain "in suspension" if using a epoxy resin, so it's harmless.
For most people 6 or 8 ounce cloth is fine for abrasion resistance and these weights require less resin to wetout too. A lot can be said about protecting the chines, which receive a lot of abuse. Many have used exotic fabrics in these (and other) locations. I don't recommend these measures, but a second layer of cloth tape on the chines does offer additional abrasion resistance. I personally, would use sacrificial wooden strips, like oak runners or rub strips. They get beat up and every few years you knock them off and install new ones, knowing they'll adsorb most of the abuse the boat will see.
(03-23-2010, 06:57 PM)Paul Riccelli PE,NA link Wrote: [ -> ]but a second layer of cloth tape on the chines does offer additional abrasion resistance.
Seems Ive done that on other boats I built. I wonder is it best to apply the tape over the chines first and then do the whole glassing over the tape or to do the tape last?
Yeah, the mat may go in the re-do of the Vacationer plans. That was a long time ago, and there have been understandable improvements in stuff over the years (decades, actually!)
Mike
I put the tape on first, which is then faired smooth, so the cloth sheathing doesn't have any bumps to contend with (it's a lot easier to fair before the sheathing then after). The tape seals/protects the seams at the chines and the sheath the rest of the hull.