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 !

On Wed, 9 Jan 2008 20:32:49 -0500, "Garland Gray II"
wrote:

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 !


No personal experience. Here's an unqualified opinion:
epoxy bonds to PVC. PVC pipe is a little wavy.
Taken together, I think this means removing the glass from the plug
would be tough.
Saran wrap is one avenue to reliable release I hear - or maybe a
good release agent - or aluminum foil I have heard suggested.....

Brian Whatcott Altus OK

On Wed, 09 Jan 2008 20:15:15 -0600, Brian Whatcott
wrote:

Saran wrap is one avenue to reliable release I hear - or maybe a
good release agent - or aluminum foil I have heard suggested.....

Johnson's paste wax will work. Ask the gunsmiths about that. In
general, if there are the kind of pockets that would lock them
together, fill them in with oil base modeling clay. This is no help
with slight, just enough to cause trouble, waviness.

As for pipe for a mold, there is no taper, which is the usual practice
with molds in general. Sand castings are always tapered slightly.

Casady

Right, I was concerned about the lack of taper. I hadn't looked real
closely at the surface of pvc pipe; I would sand it smooth if it looked
irregular, and then wax.
How do gunsmiths use pastewax, to protect and lube parts ?

"Richard Casady" wrote in message
...
On Wed, 09 Jan 2008 20:15:15 -0600, Brian Whatcott
wrote:

Saran wrap is one avenue to reliable release I hear - or maybe a
good release agent - or aluminum foil I have heard suggested.....

Johnson's paste wax will work. Ask the gunsmiths about that. In
general, if there are the kind of pockets that would lock them
together, fill them in with oil base modeling clay. This is no help
with slight, just enough to cause trouble, waviness.

As for pipe for a mold, there is no taper, which is the usual practice
with molds in general. Sand castings are always tapered slightly.

Casady

On Wed, 9 Jan 2008 22:17:23 -0500, "Garland Gray II"
wrote:

How do gunsmiths use pastewax, to protect and lube parts ?

That and release agent.

They coat that part of the metal of a rifle that touches the wood with
wax. Then when epoxy and glass powder are used for a perfect fit, you
can get the action out of the stock after the epoxy sets up. This is
called glass bedding the action. The perfect fit is good for accuracy,
usually. It also seals the wood against changes in moisture content,
and the attendant warping.

This is, of course, in addition to ordinary, usual, use to protect
both wood and metal from, for example, rain. Guys do hunt in the rain,
nutty though that may sound

Casady

Richard Casady wrote:
On Wed, 9 Jan 2008 22:17:23 -0500, "Garland Gray II"
wrote:


How do gunsmiths use pastewax, to protect and lube parts ?


That and release agent.

They coat that part of the metal of a rifle that touches the wood with
wax. Then when epoxy and glass powder are used for a perfect fit, you
can get the action out of the stock after the epoxy sets up. This is
called glass bedding the action. The perfect fit is good for accuracy,
usually. It also seals the wood against changes in moisture content,
and the attendant warping.

This is, of course, in addition to ordinary, usual, use to protect
both wood and metal from, for example, rain. Guys do hunt in the rain,
nutty though that may sound

Casady

Without the typical 7 degrees of draft (taper) you'll never get it off...

I know because I've tried exactly that.

Richard

"Garland Gray II" wrote:

..
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 ?

NO.

Or would I
need to first wrap the pipe with sheet plastic or similar ?

Depends.

Easiest solution is to glass pvc tube and leave it in place.

It what I did to make a shaft tube.

Next approach was using an 8" PVC pipe for a mold to fabricate a bow
thruster tube..

First you slit the PVC pipe on one side using a table saw.

Then you plug the ends of the slit tube with wooden plugs.

Next, cover slit pipe completely with clear contact paper.

Support tube on each end.

Next, using light weight glass, say 17 OZ, double bias, wrap tube in a
continuous wrap until yo get req'd layers.

When cured, cut off plugs and break PVC pipe in pieces to remove.

Doubtful you can do this on a small pipe such as 2-1/2".

If you must remove PVC tube, the cover it with contact paper and wrap
2-3 layers of glass.

When cured, slit both glass and PVC tube with a saw, the spring
lamination open to remove PVC tube.

Repair cut in glass, then use a mold to finish layup.

I've done all of them.

Have fun.

Lew

"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 !

Interestingly I've done pretty much exactly this recently. I think the
plastic sheet is essential and you need few wraps. One suggestion on another
forum was to put several long thicker strips of plastic under the wrap
....protruding from the end so they could be pulled out and give a little
room for the wrapped plastic to slide and twist as you remove the glass
tube.

Peter HK

"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 !

It will release but only with great difficulty. The GRP part will shrink as
it cures and that will make the release VERY difficult even though the GRP
is not stuck to the mould. What we normally do is engineer some flanges
into the layup such that we have something to pull against because we will
be exerting great amounts of force with clamps, presses, wedges, compressed
air etc. The part needs to be able to witstand these forces and you need
some way and place to apply these forces. The flanges or metal chains laid
into the part can later be cut off. Likewise, you may need to engineer some
sort of bearing piece in your PVC pipe. Or maybe use a 6' long theaded rod
with nuts to apply force like a bearing puller. Still, the part needs to be
strong enough to not buckle.

Instead of wrapping with plastic sheet, we frequently use clear packing tape
in 2" widths as a mould release. You tape up the part with clear tape, then
wax then lay up. Do not use masking tape - sometimes the wax on the masking
tape inhibits full cure of the poly resin.

The easist way would be to buy polystyrene foam rods of the correct diameter
from a craft store. Tape up and lay up. Melt out the foam with acetone or
lacquer thinner when cured and pull out the clear tape. This is the most
stress free way. Only problem is that the foam rod may deform (bend) during
curing. Same as with PVC tubes. .... I just re-read that you will be using
epoxy. In that case, with foam rods, don't even bother with a release agent
or tape since epoxy resin will not dissolve your foam. And if you are using
a low shrink epoxy, you will not get much deformation if at all.

Or do what Peter hk said. That'll work.

Here's a tip - we've all been taught to "wax on, wax off". I do it
different - "wax on, wax on, wax on" let the wax harden up and do not wipe
off. Layup over that. The part comes up with alot of wax transfer and
swirls marks but those are easy to polish out. I do this even when making
production molds because I refuse to risk a stuck plug and mold.

Arnold sg

You've had many good suggestions for dealing with the shrinkage of the
glass-epoxy laminate. Here's one more.

With a tablesaw, cut one lengthwise slit in the pipe and cover the slit with
packing tape.
Wax the pipe thoroughly and do your layup. Bond a couple of blocks or other
attachment points to one end the part.
Twisting the pipe vs. the part should break the bond between the pipe and
the part.
Drill the other end of the pipe for some attachment and pull the part from
the pipe with a come-along.

"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 !