I have been reading DYI articles, blogs, & forums, watching You Tube tutorials and talking to anyone that I think knows anything about fiberglass and it’s marine applications for the last 6 months. I think I have finally formed a reasonably versed opinion on the various materials and their applications.

There are 2 major types of fiberglass resins and 2 major types of fiberglass core materials.

Of the 2 resins, Polyester resin is the cheaper and is used for primary adhesion. Epoxy resin is much more expensive and is used for secondary adhesion. I will get to Cloth & Matt in a moment.

By primary adhesion I mean an application like the making of a boat hull.

Polyester works well for this application, especially when used wet on wet. Wet on wet is when a layer of cloth is laid down and subsequent layers are laid down while the previous layer is still wet with resin (or uncured). This is purported to make a very strong bond if the various layers can cure together.

By secondary adhesion I refer to fixing something to the cured primary adhesion like an addition to an existing hull.

Cloth is a woven material just as it’s description suggests and is primarily used for the construction of structure but can be used for just about any application. Matt is a pressing of fibers and can be used for filler or bulking up a construction project.

I am in the process of rebuilding the floor in my 16’ sailboat and after having removed the rotted plywood, I want to build a floor entirely out of fiberglass with no wood in the structure.

under the plywood was expanded foam and it is still in pretty good condition. It does have a few dings and depressions in it so I have decided to use the canned foam from a hardware store that is used for filling cracks in houses. This foam is "Closed Cell" foam and should be fine. It purports to be sand able and paintable so I believe that after filling, trimming with an electric kitchen carving knife (I am hoping to buy one used for $10 today) and sanding, the foam should be ready to accept a fiberglass floor with no other support. The floor is approximately 2’3” x 10’.

So I am intending to lay down 4 layers (Cloth/Matt/Cloth/Matt) in succession using polyester resin. When cured, I intend to lay one more layer of Cloth with Epoxy resin, sealing up the sides to the seat bulkheads. This should give me the cheapest and the strongest structure.

I bought the Cloth, Matt, and Resins this last weekend. Cloth & Matt was about $6 average per yard (48” wide). The Polyester Resin was $36 a gallon including hardener and the Epoxy Resin (West Marine System) was $150 per gallon including hardener. So you can see that the correct resin for the correct application is important both from a strength and cost perspective.

That is the plan I am going forward with and here are cross sections of my plan.