Tuesday, August 5, 2008

Tech Tip Tuesday

Today's tech tip is an "advanced technique. It's called hot coating. and is used to apply epoxy quickly.

With my new students, I try to keep things simple and do things in stages. Once the hull is prepared, we apply a sealer coat and let it cure. We then lightly sand the sealer coat and wipe down with denatured alcohol (or acetone if you prefer...) Once this is done, the hull is draped with fiberglass cloth of the appropriate weight for the canoe. We then apply epoxy to the hull with a squeegee and once the hull is wet out, we remove excess epoxy to wind up with a uniform textured finish. Two bias cut strips are then applied to the stems before the first coat cures. After this cures, the hull is wiped down again and more epoxy is applied. This is repeated until the weave is "filled" and you have a smooth coat of epoxy - the cloth should be buried in the epoxy to the point where sanding the epoxy will not result in sanding the fiberglass cloth which causes the fiberglass/epoxy coating to lose transparency.

That's the long way.

To hot coat, you need a "blush free" epoxy for best results. With the hull prepared, you drape cloth on the hull. You then apply epoxy with a squeegee and then apply the two bias cut strips to the stems. Be careful to make sure enough epoxy is applied so that the cloth isn't "starved" which is seen as whitish areas. Here is where the hot coat part happens. After about an hour or two (depending on temperature) the epoxy is tacky and doesn't lift when you touch the hull with a gloved finger. At this point, it's time to apply another coat of epoxy. Repeat until the weave is filled. It should be possible to apply as many as 4 coats of epoxy in a day. It really speeds up the process, but requires doing a good epoxy job.

This is an important skill to gain - if you have a tight schedule, it's the only way to apply epoxy.

Please note - the picture above is for illustrative purposes only - I do NOT recommend his choice (or lack thereof) of safety equipment. You should avoid skin exposure, wear gloves and eye protection and work in a well-lit and well-ventilated are when working with epoxy. Some people even prefer to go the extra step and use a respirator mask with organic vapor cartridges.

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