: Well the deck turned out a lot better than the hull (building a Guillemot
: double) - too much glue showing in too many seams. I have two coats of
: epoxy on the glass. When up close and personal with the boat you can see a
: slight design/pattern of the glass. Does that mean I am too fussy or that
: another coat would clean that up and make that go away? Or,will the
: varnish help with this issue?
: Thanks for your input.
: Joe

It will be very hard to tell at this point how your glass will look after it's sanded smooth
and varnished. The rough surface you now have breaks up the light too badly to see the
glass. I would want at least three coats or resin over the wet-out.

I've worked with epoxy/glass lay-up for many years and this is how I produce a consistanlty
transparent lay-up.

Using Epoxy Resin and Fiberglass Cloth to make a Transparent Lay-up

Though epoxy resins have been used in boat building for a long time, they were not specifically designed to produce the transparent fiberglass lay-ups desired in stripper construction.

To produce a transparent fiberglass lay-up the epoxy resin must be able to displace air and thoroughly wet-out the twisted fiberglass fibers in the cloth. The tighter the glass weave is, the more difficult it is for the resin to penetrate, wet-out and make transparent.

A resin with a thin watery consistency works best to wet-out the fiberglass cloth making it transparent. Visible cloth or silver fleck indicates that the cloth was not totally wet out. A thin watery resin also allows air bubbles and foam to dissipate.

Epoxy manufacturers now make specialty laminating resins specifically designed to wet-out fiberglass cloth for a transparent lay-up. These resins are very thin/watery and will wet-out cloth quickly at room temperatures (70·) and lower. These resins are usually more expensive than regular resins and are not good for other applications like coating or gluing because they are so thin in consistency. Using a specialty resin also means you will have to buy additional regular resin for the rest of your boat building. Epoxy is sold in set units, so you may end up buying more or less than you will need.

Regular epoxy resin is a syrup consistency at room temperatures. This makes wetting -out fiberglass cloth more difficult UNLESS special measures are taken.

If the regular resin is warmed to 85 -90· it will become much thinner making it’s wet-out properties better. If the resin is warm and the glass/wood is cold, the resin will thicken on contact.

So if your whole shop is heated instead of just heating the resin, the resin, wood and glass will all be at the same temperature and the wet-out will work well.

The disadvantage to this is that heat will accelerate the set-up of the resin. This will reduce your working time and the ability of the resin to wet-out the cloth as the resin thickens.

Most resin hardeners are available in fast and slow options. So using a slow hardener will give more work time and a better wet-out.
Information given with the epoxies will talk about a “pot life” for each resin/hardener combination. This pot life refers to the length of time it will take for the mix to set up in the mixing pot. The mixing of the the hardener with the resin starts a catalytic reaction generating it’s own heat. When the resin is left in the “pot” or mixing cup, it is in a mass which concentrates the heat production further accelerating the set-up of the resin.

Furthermore, Epoxy resin will begin to thicken as soon as the hardener is mixed in. This is almost imperceptible, but over a working time of ten minutes the resin will thicken enough to reduce it’s wet-out properties and it will be difficult to remove excess resin from the cloth with a squeegee.
This problem can be overcome by mixing small batches of resin instead of large ones.

Never mix more than 6 oz. of resin and hardener.

This will produce less heat in the mixing cup. And by using smaller batches you will continually use the resin at it’s thinnest stage, improving wet-out. Using many small batches will also extend your working time as the many small batches will set-up more slowly than several large ones would. Using small batches will allow you to better estimate how much resin you need to finish the job, resulting in less waste.

The set-up time for the same mix of resin will be greatly extended IF the resin is poured into a large flat container, like a paint roller tray, where the resin is spread thinly. It will be cooled by the large surface area and cannot produce the heat it would in a mass.

If you use a roller to apply the resin it will produce a thin consistent coating that will wet-out the glass well and allow foam or bubbles to dissipate.

So you can consistently produce a transparent glass lay-up using
regular resin if you:

Heat the shop or work on a hot day with temperatures at 85 -90·

Use slow hardener.

Mix small batches

Pour resin into a flat tray.

Roll on a thin coat.

Any glass you want to be transparent has to be treated this way. That means if you want your exterior hull/deck seams and stem reinforcement strips to be transparent you must wet-out the cloth this way.

Fiberglass cloth is the other important consideration when trying to create a transparent lay-up.

This why the best weave to use for a stripper, if you want as transparent a lay-up as possible, is plain weave fiberglass cloth. In plain weave cloth the strands run visibly perpendicular and there are small spaces around the strand intersections.

Some of the fine weave or satin weave fiberglass cloths are so tightly woven they appear as a dense opaque sheet of cloth that is very difficult to wet-out and make a transparent lay-up with. The alure of these clothes is that they promise higher strength and lower weight because of the higher fiber count and low profile which needs less resin. Again, I emphasize these types of cloth are much more problematic in producing a transparent lay-up and should be avoided.

All the best,
Rob Macks
Laughing Loon CC&K
www.laughingloon.com