foam problem

Dave Lyon wrote:
"Evan Carew" wrote in message
...

John T wrote:

You'll want to avoid using polyester resins on your foam, unless you
want your tank to melt!

I can see how this would be a problem. The foam would crush on impact
with a paintball, the fiberglass would eventually fail from the
dissortion of the foam underneath it.

maybe you could bond some aluminium skin to the foam. It'll dent like
crazy, but it might last longer!


Actually, the s-glass embedded in epoxy will perform better than the
aluminum. Thus the name "composite". You are combining a product, glass,
with a high tensile strength with something that has poor tensile
strength, epoxy. Then you bond that to something that has a high degree
of stiffness (foam). The idea is that when yo
u try to deform the foam/fiberglass composite, the high tensile strength
covering tries to distribute its load out over the foam. The higher the
tensile strength coating, the larger the area of load distribution.


So, you're saying that another layer of 10 oz glass will help my problem.

Can I put both layers on at one time and expect them to get wetted out
properly, or should I do them one at a time with a sanding step in-between?


Typically, you would put them on at the same time. What you do when you
are doing wet layup on raw foam is to squeegee a film of micro onto the
foam first. This will act as the binder between your fiberglass & your
foam. Then, get a long cardboard tube, just longer than the width of
your glass cloth bolt. Then, cut two lengths of glass to size and roll
then up (stacked evenly ontop of each other) onto the tube. Now, unroll
the dry glass onto the foam where you squeegeed the wet micro. Finally,
use a paint brush with stiff bristles to "stipple" the epoxy into the
two layers of glass. When you are happy there are no subsurface voids,
take your squeegy and squeeze out any extra epoxy (adds weight but no
strength). That's the way the book says to do it. I just use the squeegy
tho and work the epoxy back and forth until all the cloth is wet. This
technique works well up to 4 layers thick.

In the event that you need local reinforcement for a physical attachment
(bolt your panels to a frame), you will need to embed hard-points. THis
is done by getting a square of spare plywood the same thickness of your
foam, then cutting out the same sized square in the foam prior to
glassing. Its ok to use a hot glue gun to fix the plywood in place for
easy handling. As for the rest, well, you get the idea.