One solution that I have tried on a smaller scale. Slit the PVC pipe down
one side on a table saw. The pipe should close up a little so the kerf will
be a little less than 1/8". Cut a strip of 3/16 or maybe 1/4" polyethylene
sheet maybe 1/2" wide and fit it in the kerf so that the edge is flush with
the pipe's outer diameter. That will expand the pipe over it's normal
diameter. Wax everything and spray on a couple of coats of PVA mold release.
Mist coat first then a fill coat.

Wrap your glass. If it is uni-directional, diagonally in both directions
then straight once or twice then a top ply of woven on the bias. If you are
vacuum bagging you have to pull all the diagonal and bias plies TIGHT and
tape them well or the fiber will bunch up as the bag pulls it down.

Once it is set up, knock out the poly strip out of the kerf and whack the
outside of the tube lightly to break the release agent and let some air in.
The pipe will spring back to its original diameter and drop out. If it
still sticks soak it in water to dissolve the PVA.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Garland Gray II" wrote in message
...
If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6
feet long, and then lay up several layers of fiberglass and epoxy, would
the resulting tube slide off the pvc easily enough after curing ? Or would
I need to first wrap the pipe with sheet plastic or similar ?
Thanks !

One other hint for wrapping a tube with uni-directional on an angle.
Multiply the OD of the tube by 3.14 to get the circumference and then by the
sign of the angle you want. For example for your 2.5" tube, the
circumference is 7.85". The sign of 45 degrees is .707 so cut strips of uni
about 5.5" wide. If you keep the edge of each turn next to the previous one
you will have a 45 degree angle.

Again, pull it very tight if you are vacuum bagging.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Glenn Ashmore" wrote in message
...
One solution that I have tried on a smaller scale. Slit the PVC pipe down
one side on a table saw. The pipe should close up a little so the kerf
will be a little less than 1/8". Cut a strip of 3/16 or maybe 1/4"
polyethylene
sheet maybe 1/2" wide and fit it in the kerf so that the edge is flush
with the pipe's outer diameter. That will expand the pipe over it's
normal diameter. Wax everything and spray on a couple of coats of PVA mold
release. Mist coat first then a fill coat.

Wrap your glass. If it is uni-directional, diagonally in both directions
then straight once or twice then a top ply of woven on the bias. If you
are vacuum bagging you have to pull all the diagonal and bias plies TIGHT
and tape them well or the fiber will bunch up as the bag pulls it down.

Once it is set up, knock out the poly strip out of the kerf and whack the
outside of the tube lightly to break the release agent and let some air
in. The pipe will spring back to its original diameter and drop out. If
it still sticks soak it in water to dissolve the PVA.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Garland Gray II" wrote in message
...
If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about 6
feet long, and then lay up several layers of fiberglass and epoxy, would
the resulting tube slide off the pvc easily enough after curing ? Or
would I need to first wrap the pipe with sheet plastic or similar ?
Thanks !

"Terry K" wrote in message
...

SNIP
and sanded inside after set up
using a balloon and sand paper.

Terry K

That's a great idea! They are gonna laugh me out of the shop!

Arnold

Alex wrote:



What about making the core out of Styrofoam plastic, wrapped in release or
heavily waxed, and after the expoxy sets up dissolving the Styrofoam with
gasoline, acetone, MEK or some other solvent that attacks the foam but won't
hurt the epoxy?

A possible advantage of this approach is that it allows the production of
shaped epoxy parts that are more complex than a simple tube, should that be
needed.

Epoxy is fairly resistant to gasoline and many other common solvents, but it
certainly would make sense to "insulate" it from the solvent with the
release sheeting, heavy wax, etc., and then to thoroughly clean it after the
core is removed.


I've done this one several times.
It works quirw well.

Downside - the inside surface is goinf to be pretty rough - resin
seeping into the crevices in the foam.

If that is not a problem (and in this case it's probably not) this
is probably a reasonable approach.

But if I had to make this part?

I'd use a paper tube for the core mold.
Just make sure it's not waxed paper...

Richard

There was an article in Good Old Boat where the guy built a water lift
muffler. To do what you are asking, the guy wrapped one layer of glass
and epoxy around a well-waxed pipe. After it cured, he slit the glass
and removed it from the pipe. A little epoxy and he glued it back
together again and continued with the lay-up.
Article 3367 May/June 2007. Pages 33 - 36.