Fiberglassing plywood for new hatches?

[JustPhish]

Morning folks. My hatches were all sagging pretty badly so I took them out and cut new ones out of cabinet grade, 7 ply, 3/4" plywood. Tomorrow I intend on trying my hand at fiberglassing for the first time and I had a question about the plywood.

Can I just run the cloth to within a quarter inch of the edge of the plywood? I will then just seal the edges of the wood with the resin. I will only do one layer of fiberglass as it was really just to weatherproof the plywood, not add any extra strength. My concern is that I am not routing the hard corners of the wood around the perimeter and it's kinda too late to make arrangements for it now as I want to get this done and in the water for memorial day and I'm worried that the cloth will not make these outside corners very well.

Any tips that can be offered would be appreciated too.

Thanks,
JP

 

[ezmobee]

Re: Fiberglassing plywood for new hatches?

If it's poly resin you're using....it's pretty well worthless without glass for sealing. Epoxy however, would be fine.

 

[Woodonglass]

Re: Fiberglassing plywood for new hatches?

You could use .75 oz CSM mat and Poly resin. It will wrap the edges pretty easily and hold the resin too! Couple layers and you could sand em pretty smooth and paint. Or you could use the cloth up to the edges and seal the edges of the wood with some 10 minute epoxy. Or you could just seal the edges with 10 minute epoxy, give 3 coats of marine Varnish sand and paint. Lots of options!!!

 

[JustPhish]

Re: Fiberglassing plywood for new hatches?

Hmmm, it's 3M fiberglass resin I got from Home Depot. 20124 is the item number from 3M. Going to guess it's poly then?

 

[Greg Mrozinski]

Re: Fiberglassing plywood for new hatches?

That poly resin probably has wax in it. If you do more than one lay-up/coat of resin you will need to sand and wipe with acetone before you apply the next layer or coat of resin.

 

[BWT]

Re: Fiberglassing plywood for new hatches?

more than likely it's poly. Follow WOG suggestions on using the CSM and you'll be good to go.. I am partial to using epoxy, but poly is what you have and using that with some glass will be just as good (just a little more work).

 

[JustPhish]

Re: Fiberglassing plywood for new hatches?

Thanks for the tips. It says as long as applied while still tack another coat and just be put on but sanding is necessary if allowed to dry inbetween. I suppose I'll just try and round the corners down with some coarse paper and then wrap the cloth (also 3M as depot only had cloth or mat and I thought I read cloth was best) around to the bottom and do the same from the bottom around up to the top.

 

[BWT]

Re: Fiberglassing plywood for new hatches?

as long as it's still tacky you can laminate additional layers without any problems with adhesion. All the wax does it seal the surface so the poly can fully cure and sand without gumming up the paper. I would do 2-3 layers of CSM; this will allow you to sand to a smooth surface without any print through of the glass when you paint.

 

[Woodonglass]

Re: Fiberglassing plywood for new hatches?

With resin it is best to use MAT first as a base. It gives the cloth something to Bind to. Also the cloth is a bit harder to make it conform to corners and edges and such without getting air pockets. Have a Razor Knife handy or old scissors and some acetone for cleanup. Wear rubber gloves so you can use your hands to smooth and form the cloth. A plastic putty knife is a good tool to have as well for working out air bubbles.