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Re: Strip: Joining Deck to Hull

Being June in South Carolina achieving 80+ in the shop (a.k.a. garage) won't be a problem. :) I'll try wetting out a piece of the 9 oz just to see how effective it is.

I've only been working with fiberglass/polyester/epoxy resins for about 45 years.

Take a piece of fiberglass cloth. Pull out a thread. Unravel the thread and look at one fiber. The fiber is white because light is reflecting off the surfaces on this fine fiber of glass. Put it in a glass of water and it will disappear because all the surface is coated and light passes right through.

This is what we have to do to have a transparent fiberglass cloth lay-up.

To do this we must have a thin epoxy resin mix that stays thin for as long as possible. Epoxy resin and hardeners are exothermic, the chemical reaction in the change from liquid to a cross linked solid generates heat. The more heat the faster the reaction.

Epoxy resins are thicker when cooler and thinner when warmer, so if we wish to have a transparent lay-up we must start by using warm resin and only with an equally warm shop and materials, will the resin remain thin.

When using warm resin we must then use a slow hardener to counteract the warmer resin's influence to speed the resin's cure.

Resin begins to thicken the moment hardener is mixed in. So even though we use slow hardener with warm resin the resin is getting thicker every second it has been mixed. Will the resin stay thin enough to wet every surface of every fiber and still be thin enough to allow excess resin to be squeegeed off for the lightest weight lay-up?

Resin in mass such as a cup will increase heat generated by the exothermic reaction of resin and hardener increasing thickening, so as soon as mixing is complete the resin should be poured into a flat tray to spread the resin out reducing it's heat generation.

Small batches, 6 oz. of resin and hardener will stay thinner for longer periods of time with all the above considerations and small batches force more new and thinner batches to be used optimizing a transparent wet-out.

Just as important as is the resin's ability to wet-out the fiberglass, is the resin's ability to dissipate bubbles and foam. This is the true measure of combining all the points I've talked about and how multiple layers of fiberglass can be overlaid transparently.

All these considerations must be taken into account for success. Clearly there is a lot going on here if you really want to ensure a transparent lay-up of fiberglass/epoxy.

Every piece of fiberglass applied to seams, stems, onlays, must be treated the same way to get the same results.

If you don't care you can take your chances with dumb luck.

The devil is in the details.

I hear and I forget. I see and I remember. I do and I understand.
Confucius