Ok, Garland,

BTDT.....

If you are going to do this, do not wrap anything around the pipe,
without some other plan. The wrapping will ball up when you try to pull
the two apart. I have not tried the PeterHK plan, but I'm not sure how
well the 6' strips will pull out. I even tried a teflon family sheeting
in one try and it was still tough. That one had a stainless mandrel
because the mandrel would later be the rudder shank.

Cut the mandrel pipe too long so you can hold it. Make the layup too
long and fabricate some feature at the end to allow good purchase.

Shrinkage is epoxy specific, talk you the manufacturer about both that
and the best mold release.

This is not going to be easy. If you can create a mandrel that can be
unloaded, that will be a great advantage. I have never figured out how
to do this without a surface artifact that leaves an internal
longitudinal ridge in the layup.

Good Luck Guy

Matt Colie


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 !

On Thu, 10 Jan 2008 01:35:20 -0600, cavelamb himself
wrote:

Richard Casady wrote:

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,
....
Casady

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

I know because I've tried exactly that.

Richard

You perhaps tried a complete collar of glass.
The usual forehand bedding is for the lower half of the barrel.
This can be pulled free, as far as I know.

Brian W

On Thu, 10 Jan 2008 10:59:46 -0500, "Conlin"
wrote:

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
... tape.

Make that a long straight diagonal (shallow taper) cut, and success is
pretty certain, I'd think....

Brian Whatcott Altus OK

I can't see what benefit there would be to the slit being diagonal or
tapered and it'd be a tricky cut to make. The important thing is that the
pipe be able to contract a bit after the laminate has cured.

A couple of other possibilities:
Coat the pipe with a thin (maybe .020") coating of paraffin wax and melt the
paraffin out after the laminate's cured.
If using a core of styrofoam (with packing tape finish), the core can be
mechanically destroyed after the cure.

"Brian Whatcott" wrote in message
...
On Thu, 10 Jan 2008 10:59:46 -0500, "Conlin"
wrote:

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
... tape.

Make that a long straight diagonal (shallow taper) cut, and success is
pretty certain, I'd think....

Brian Whatcott Altus OK

I want to thank everyone who has given me all this good advice. I suspected
it might be a problem, so I thought I'd ask.

You have saved me a lot of frustration. Thanks again.

On Jan 10, 7:50 pm, "Garland Gray II" wrote:
I want to thank everyone who has given me all this good advice. I suspected
it might be a problem, so I thought I'd ask.

You have saved me a lot of frustration. Thanks again.

OK, I HAVE done this. I took some newspaper and wrapped it round a 2"
piece of pipe roughly 2' long. Next wrap that with wax paper which is
your release layer, apply the epoxied glass. It came off with no
problem, in fact, I did it twice.
I used this method to make the mast step insert for my MiniCup
sailboats.

On Thu, 10 Jan 2008 17:31:47 -0800 (PST),
wrote:

On Jan 10, 7:50 pm, "Garland Gray II" wrote:
I want to thank everyone who has given me all this good advice. I suspected
it might be a problem, so I thought I'd ask.

You have saved me a lot of frustration. Thanks again.

OK, I HAVE done this. I took some newspaper and wrapped it round a 2"
piece of pipe roughly 2' long. Next wrap that with wax paper which is
your release layer, apply the epoxied glass. It came off with no
problem, in fact, I did it twice.
I used this method to make the mast step insert for my MiniCup
sailboats.


There's something rather appealing about this approach - the paper
layers slipping over each other, so the pull gets a little easier as
it pulls off.
Perhaps instead of newspaper, cheap greaseproof paper under the wax
paper top coat. Perhaps even sprinkle a little graphite powder over
the inner layers to help the slip fit on a long pull?

Brian W

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 !


I don;t believe that you could get the glass off the PVC. I have made
fiberglass tubing by molding two halves inside PVC pipe split
lengthwise and using several coats of mold release it still took
significant prying to get the halves out of the molds.


Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

On Jan 11, 3:24 am, Bruce in Bangkok wrote:
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 !

I don;t believe that you could get the glass off the PVC. I have made
fiberglass tubing by molding two halves inside PVC pipe split
lengthwise and using several coats of mold release it still took
significant prying to get the halves out of the molds.

Bruce-in-Bangkok
(Note:remove underscores
from address for reply)

Wrap several layers of waxed paper instead of the newspaper. It never
occurred to me that it might NOT work. Shrug.

On Jan 9, 9:32 pm, "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 !

After the goo sets up, running a source of heat inside the pvc could
soften it enough to pull out, or even to melt it out. Epoxy wouldn't
be bothered by the heat required, I suspect.

Alternatively, perhaps a plug of wax wrapped in a seperator would more
easily be melted out. It's called the "lost wax" process.

Or, a spiral coiled cardboard tube could be pulled out after set up.

When I relined my rudder tube, I used epoxy with graphite shaped with
a pvc pipe pulled out before setup and sanded inside after set up
using a balloon and sand paper. I was worried that I might need to
cut a tooth in the rudder post and use it as a tool to bore out the
hole, or to use a hole saw and guide setup.

I am told the "proper" way was to install top and bottom rudder
bearings, but that would have cost quite a bit.

Seems to have worked out, no more jamming or juddering under moderate
loads.

Terry K