I thought newer members of the group might benefit from reading some of
Gary Hunter's wisdom.
Graham
> I think (hope?) I am being too picky as to the weather conditions
>during
> which I will do a layup.
> Has anyone established a 'rule of thumb' for determining when one
>can and
> cannot work with epoxy given a forecast for rain?
> Thanks.
>
>If you are working outside with no roof, I can understand your frustration.
>One must avoid having a lay-up rained on. However, if you are under-roof,
>or better yet inside a garage or a building with closed sides you shouldn't
>be so picky.
>
>If you are working in a building with the doors open for ventilation, the
>relative humidity in the building will certainly come close to what it is
>outside. Although, high humidity conditions are not the best for working
>with epoxies, some resin systems will tolerate it fine. Some resin systems
>are susceptible to "blushing" and you will notice a milky appearance to the
>resin as you work with it. Most of the time, as the resin cures, this milky
>appearance goes away leaving an oily like film on the surface of the cured
>laminate. It looks and feels terrible, but not to worry, this film will
>wipe off with warm water and wash cloth.
>
>The biggest concern I have, is problems relating to the applicator and how
>he or she responds to high humidity conditions. If you are a sweat hog like
>myself, dripping beads of sweat into your work can be a real big problem.
>A few drops of sweat on a laminate that has already been completed but not
>fully cured is not so bad - just don't rub or squeegee it into the laminate
>- simply blot it and let it dry. Sweating on the dry fiberglass, or a layer
>of the laminate that is in the process of being wetted out is a big NO NO.
>
>This is one reason I advocate you find a way to "temper" the air in your
>shop. Your project will go a lot faster, and you will enjoy it more - both
>in the winter and the summer.
>
>Hope that helps.
>
>Gary Hunter
>EAA Technical Counselor
|