My brother (the host here) and I have made several kayaks from a mold he made, with epoxy, fiberglass and structural foam. It worked ok, but it was difficult, you might say it was a royal pain in the ....

We used commercial peel ply and blotter material (like a blanket) and I think it was nylon sheet for the outside, Nick may remember. I got a surplus vacuum pump form work. We sealed the coversheet to the mold with sticky putty and used cheap plastic tubing to attach the pump and the mold. we layed up the glass and epoxy first, then sealed the mold. I made a chamber to catch any epoxy that got sucked out. It was hard to get a good seal all around and to get the vacuum strong enough to do its job.

Ive used the same pump to use a vacuum to hold a veneer inlay onto the deck of my S&G baidarka with pretty good results. It was a much smaller volume to work with. The peel ply and blotter are still needed, i had less success with out it.

> Here’s one for you aerospace guys.

> Can someone explain to me the vacuum bagging process. I know that the home
> built airplane guys use it a lot to get maximum strength/weight ratios out
> of a given thickness of cloth.

> As I understand it you apply the glass and epoxy in a normal way cover it
> in a “peel/ply” and/or “breather” layer, put the whole thing in a vacuum
> bag and then by evacuating the air, you get uniform pressure over the
> surface. My assumption is that less epoxy can be used and still get
> complete wet out and bonding to the surface.

> My questions are:

> 1. how do you peel off the layers after the epoxy cures? I remember trying
> to get my hatch covers off after building the lip for flush hatches. Even
> after liberal doses of past wax the epoxy was holding on pretty good.

> 2. I have this vision of the vacuum pressure squeezing out the excess
> epoxy from your layup but where does it go. At best it would come to the
> surface to be sanded down but I don’t think that is right. If it squeezed
> into the peel/ply then I assume you would never be able to “peel” it off

> I have never heard of anyone on this board using it so I assume that it is
> either very expensive or provides only marginal strength / weight
> improvements.

> Jack