tom jelly wrote:

Funny thing about forming tubes- I saw what nasa did- they used SILICONE
RUBBER of all things inside a 2 piece mold- 2 half round aluminum parts

and

a silicone male cylinder core.  unlimited pressure available as we all

know

now....pushing on the ends of the silicone pushed it out, compressing

the

matrix in the mold.

Tom>

That is good to know. The florescent light bulb trick is only good for one

or two

sizes but that trick will work for all sizes. Furthermore you get a good

finish

on the outside of the tube.

I made a few straight carbon and glass tubes wrapped on just about any
constant diameter tube that was laying around. I used PVC pipes and  paper
packing tubes. Both of them worked well to me.

 To get the fiberglass tube released one has to wrap the pattern tube, say
with two or more layers of plastic foil non sticking to epoxy. Both mold
release plastic from Wicks and  paint drop protection foil worked well.

Make sure that the pattern tube is not contaminated with epoxy. DO NOT use
any sticky tape to attach the plastic foil to the tube, just wrap it
semitight around by rolling it on a table and tighten a little by turning it
in hands, and make sure that the plastic extends well outside the
glass/epoxy area. Make sure that no epoxy gets between the layers and the
pattern tube.  Put the glass or carbon on top of the plastic, wrap it in
peel ply to suck excess epoxy  and wait until it hardens. Now twist the
inner pattern tube to loose/expand  the inner plastic. You have to turn it
in the same direction as you used for wrapping of the foil. Very little
twist is necessary and suddenly the inner tube is free to get out with
minimal resistance. After you got the pattern tube out,  grab the end of the
foil, pull on it with simultaneous twisting, unwrapping layers of the plasti
c foil inside the tube. If the tube is very long you might need to do the
same from the other end too. Now you will see why the plastic must extend
well outside of the glassed area - it gets shorter as you twist it like a
rope and you might need some sort of a clamp to hold it inside the tube  if
the plastic is too short. Once the foil is twisted like a rope it will
separate from the produced tubing, leaving very good surface inside.

You can even use a fluorescent tube as a pattern but  you do not have to
make mess crashing it. Of course the method is useless for complicated
curved shapes.

The longest tube I made that way was around 5 feet long with 3 inch diameter
for use as an air conduit from the tail to the overhead console in the KIS
Cruiser.
Jerzy

 
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