From: "Jim Miller" 
To: "Scott Berfield" ,
        "ATM list" 
Reply-To: "Jim Miller" 


The model airplane folk have a fair amount of experience making fuselages
and wings out of fiberglass and carbon fiber.

What size tube (length and diameter) are you trying to build? How much
money do you have? Carbon cloth ain't cheap. Is a truss out of the
question?

The usual problem with vacuum bagging is how to get the male part out of
the inside of the tube you are trying to create. For things like poles with
3/4" diameter a mandrel is machined with a taper along its length, the
fiber is laid up and cured and the mandrel is cooled allowing the pole to
come off. For something like a telescope tube it might be prohibitive to
create such a mandrel.

The reason for vacuum bagging is to force as much epoxy out of the matrix
as possible. For your purpose this may not be as important as for an
ultralight sailplane fuselage. If that is the case you might be able to do
a balloon inside a female mold (tube) and carefully cut the tube off the
carbon layup. The surface quality of the resultant carbon tube will be a
function of the surface quality of the female tube used plus whatever
damage is caused by cutting it off.

ACP  http://www.deltronix.com/public/acp/acp-cat.htm ) has some good info
and video tapes on construction techniques. George Sparr, the owner and
tech support, is very helpful and will usually take time to knock around
some ideas with you over the phone.

You might also find some useful info at CST ( http://www.cstsales.com/ ).
They also have some heat shrinkable tape that you might find useful to wrap
the layup in rather than vacuum bagging it.

good luck

jtm



----- Original Message -----
From: "Scott Berfield" 
To: "ATM list" 
Sent: Tuesday, February 18, 2003 1:42 PM Subject: ATM Carbon fiber telescope tubes



Anyone have experience with fabricating carbon fiber telescope tubes? My
usual method of wooden construction is going to be too heavy for what I am
trying to build currently. I am thinking I need a vacuum bagging setup to
make it work. Anyone have any tips?

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