: This is one of those queries regarding techniques/processes for
: lightweight building.
: I'm currently building a racing craft and a mate of mine is
: building a hollow timber surfboard. His plans don't call for any
: use of epoxy to seal internally and he intends to seal the
: inside surfaces by either painting or using a couple of coats of
: penetrating oil such as penetrol.
: If an internal surface needs to be sealed against water ingress but
: structural strength is not an issue, would a penetrating oil be
: a lightweight (and cheaper) alternative to a coat of expoxy?
: Thougts anybody??
: cheers

As far as the surfboard is concerned, I don't see the point of sealing the inside surface. Since it is a closed body, the point is to keep water from entering by sealing the outside. If it gets inside due to a failure of the outside surface seal, then sealing the inside will trap moisture within the wood, leading to rot. I think what is needed on the inside is a good anti-rot treatment as a backup, and a small hatch for drying the inside.