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Fiberglass 101

The most common reinforcement in our boards, fiberglass is relatively easily applied well. Due to the way it is manufactured, though, it is quite vulnerable to sloppy handling and storage: left unprotected in a moist environment, it will absorb water, which will interfere with resin absorption. Likewise, greasy hands will prevent resin absorption. Chunks of debris (sand, wood fibers etc) will cause bubbles.

Once it has been thoroughly wet, the sizing is rinsed out of fiberglass. No drying will restore this sizing, so that the material will be useless. Store your fiberglass in Tupperware containers, or Ziplock bags or such!

Fiberglass cannot bridge gaps gracefully. All deep gouges, pits and other surface imperfections need to be filled, and the whole sanded with 60grit paper or similar.

To help the structure it is intended to reinforce, fiberglass needs to remain firmly attached to it. It won't be, if applied over glossy paint, flaking resin, crumbly sheet foam, wax, or a film of water. The substrate needs to be firm, smooth, clean and dry.

Here goes: a little rail scrape came in. All the damaged fiberglass is removed, the site sanded with 60 grit, and all the sanding debris blown off. Two layers of 4oz fiberglass cloth were involved, so two layers is what I will put back

It is past 4pm, and the temperature has been dropping for the last 1/2hr.


Gather the tools (acid brush, scissors, squeegee), cut the fiberglass, with the second piece a bit bigger all around then the first, measure out the Epoxy, and mix exceedingly well ("100 strokes!" my teacher used to say)
brush on Epoxy resin

don't pile it on, rather, just apply a "full wet" coat

o, I forgot to tell you: put on gloves, or your hands end up looking like mine!

lay the first piece of glass into this coat of Epoxy. With a moist brush (damp, not loaded), dab at the fiberglass until it is clear. Brush on a bit more Epoxy. Again, don't pile it on. Simply brush on enough to make the surface shiny.
Lay the second piece of glass over the first, centered nicely. Without dipping the brush again, dab at the fiberglass. Think of this step as compacting the fiberglass, not of brushing on resin.
When the glass has turned clear, signaling proper resin penetration, swipe at it with a squeegee.

Squish hard enough to push the glass down and wipe off resin, but just not so hard as to dislocate the fiberglass.

This will remove air trapped beneath the fiberglass. When air is present, it will make a distinct "sffft" sound (honest). When all air has been removed, the lamination is quiet.


It is also perfectly transparent. It is not flooded with resin. Rather, a good lamination has the texture of the fiberglass standing proud.

A good lamination - one with good resin-to-fiberglass ratio - also does not care about orientation - right-side-up, upside down - it does not matter. As a matter of fact, in my boatbuilding days, we routinely used to laminate up to 34oz of fiberglass overhead in one pass (but I am sure glad I don't have to do that anymore!)

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