foam problem

Sorry if this is a duplicate. I just went to check my last post, and it said
it was no longer available on the server. ?


Hey guys, I've been lurking around here for quite a while to get an
education. I'm building a project that could use a little expert guidance.

I am making a paintball tank. Not the type that you put air in, but the type
that you put people in. This is my 2nd tank. I used plywood for the skin
of my first one. It was very heavy, and it didn't look very good. So, I've
decided to do a fiberglass over foam body on this one.

I'm not worried about weight as much as I am strength and cost. Hopefully
this thing doesn't fly when I'm done. I went to the lumber yard and
bought some 1/2" polyisocyanurate foam insulation. I removed the paper from
both sides, and put 1 layer of 10 ounce woven glass on each side using
polyester resin that I got from Wal-Mart. I just made a small piece (about 1
foot square) for testing.

I was very pleased with the weight of the product, and the look that it
would give my tank, so I took it out back, and shot it with my paintball
gun. The first shot went great. The stuff is much stronger than it looks.
But, if you pelt it a number of times in the same spot, the foam crushed and
caused delaminating.

Now, on to the questions. If I ad more layers, will it be able to withstand
the beating I want to give it? How many layers do you think I'll need? I
ordered some Vinyl Ester resin from aircraft spruce. Will this hold up
better? I've got somebody to donate some fiberglass mat. Would it be OK to
use this under the cloth for more strength? Obviously I'm trying to keep the
cost down. Any recommendations would be greatly appreciated.

Dave

Dave Lyon wrote:
Sorry if this is a duplicate. I just went to check my last post, and it said
it was no longer available on the server. ?


Hey guys, I've been lurking around here for quite a while to get an
education. I'm building a project that could use a little expert guidance.

I am making a paintball tank. Not the type that you put air in, but the type
that you put people in. This is my 2nd tank. I used plywood for the skin
of my first one. It was very heavy, and it didn't look very good. So, I've
decided to do a fiberglass over foam body on this one.

I'm not worried about weight as much as I am strength and cost. Hopefully
this thing doesn't fly when I'm done. I went to the lumber yard and
bought some 1/2" polyisocyanurate foam insulation. I removed the paper from
both sides, and put 1 layer of 10 ounce woven glass on each side using
polyester resin that I got from Wal-Mart. I just made a small piece (about 1
foot square) for testing.
Well, if you're concerned about cost, this won't exactly be cheap.

I was very pleased with the weight of the product, and the look that it
would give my tank, so I took it out back, and shot it with my paintball
gun. The first shot went great. The stuff is much stronger than it looks.
But, if you pelt it a number of times in the same spot, the foam crushed and
caused delaminating.
Well, for aircraft purposes, we use much stronger foam than the
insulating variety. the "blue" foam, which is called Divinycell & is
made from open cell PVC is usually used by us for wings in the 1/4"
thickness. In order to use it, you need to coat it with a thin coating
of micro (microbolunes mixed with epoxy resin). This application is
quite rigid and light, tho it will delam with repeated hits by anything
solid.

For a sturdier foam/fiberglass combo, try the polyurethane foam called
"Last - A - Foam". This foam, sometimes used where weight is less of a
concern, but dimensional stability is, can be used as discussed above.

In both cases, the use of two layers of glass is typically enough to
prevent most physical trauma from causing delaminations. More than two
would probably only add weight with quickly diminishing returns on strength.

Now, on to the questions. If I ad more layers, will it be able to withstand
the beating I want to give it? How many layers do you think I'll need? I
ordered some Vinyl Ester resin from aircraft spruce. Will this hold up
better? I've got somebody to donate some fiberglass mat. Would it be OK to
use this under the cloth for more strength? Obviously I'm trying to keep the
cost down. Any recommendations would be greatly appreciated.

Dave

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!

"John T" wrote in message
...
You'll want to avoid using polyester resins on your foam, unless you
want your tank to melt!

I tried various foams before I found this one. It didn't melt, but I wonder
if I got the best adhesion possible.


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.

Yea, I think that's what happended. The first couple of shots looked good,
but after a few dozen, things started to get messy.



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


I'd have to wear ear plugs to drive it! Have you ever been in a metal
building during a hail storm?

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.

"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?

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.