General fiberglass questions

[Emerger]

I'm glassing over a new floor this weekend. The floor is 3/4" plywood. I thinned polyester resin with acetone and coated both sides of the wood thoroughly. The bottom sides got an additional coat of un-thinned polyester resin. The wood looks and feels like plastic.

I have a lot of 2 ounce chopped strand mat and 18 ounce woven roving. Will either of these make a good covering for the floor, and if so, how many layers would be good? Thanks

 

[strizzy]

Re: General fiberglass questions

Either one will work; I would and use 2oz mat myself. I do just one layer (overlapping on to the hull), but first I tape all the seams and the edges to the hull with some 8" wide fiberglass cloth tape (8.7oz). If you were to skip this step, you might want to cut some strips up and add additional layers around the edges and seams first.

 

[andy6374]

Re: General fiberglass questions

I'd put a layer of mat on the underside as well. If though it has been coated with resin it can still sweat.

For the topside I'd use 1-2 layes of roven with a finish layer of mat to avoid print thru of the roven woven pattern.

 

[i386]

Re: General fiberglass questions

I haven't personally used roving yet but I have read it's best to put in down on mat or cloth instead of directly on the plywood.

 

[Chris1956]

Re: General fiberglass questions

Emerger, If you plan to have carpet in the boat, the roving is overkill for a floor. Even if you are not planning carpet, the roving is overkill. The manufacturers usually use a chop gun to spray a layer of mat. I recommend two layers of that mat you have(under carpet). It should do the trick. If in doubt, or your not using carpet, you can add a third layer. All you are trying to do is protect the resin from being scratched and exposing the wood.

 

[LuckyPenny]

Re: General fiberglass questions

How big is this boat? If I understand correctly, you are starting off with 3/4" Plywood, then adding approx 3/8' of glass and matting. That is going to be one heavy deck. How much weight are you adding?
You may want to consider using 5/8 (19/32)" plywood and with a properly supported frame the extra glass and matting will still give you almost a 1" thick deck. By using 5/8 over 3/4 you will reduce the total weight by almost 25%

 

[sport15]

Re: General fiberglass questions

Good point about the weight.. Unless you are building a deck for a dispalcement hull dragger/work boat, lighter is better. If the deck gets a layer over the glass (like carpet) one layer is fine, Chris1956 is right about the overkill. Weight gains like that on a small planing is a killer.
Before you put the tape on the edge joint you could put in a 3/8-1/2 inch fillet of cabosil and resin to smooth out the corner transition on the deck/hull joint. This will help prevent that joint from cracking and allowing water in..

 

[Frankenrude]

Re: General fiberglass questions

Neither. Get some 2 Oz. or lightweight fiberglass cloth. This is the stuff that looks like fabric. Some vendors call it Bi-Axial cloth. It helps protect the wood from abrasians and punctures in the membrane. Get a fiberglass serrated roller to help flatten it out. Use as little resin as possible - but leave no dry areas. BTW Roving is for structural build up and reinforcement, Chop strand mat is really for bonding panels of wood or glass together.