Re: [ATM] making carbon tubes

["matt" <electro_optic@bellsouth.net>]

A cheap and simple way to make tubes is not out of fabric but out of
unidirectional carbon tow.
Need to wrap the mandrel in a spiral layer of tow, then apply a second layer
of longitudinal unidirectional tow uniformly distributed around the mandrel,
then wrap it all in a top spiral layer of tow.
Advantages are no seams to deal with, can be vacuum bagged and oven
postcured, and tow is the cheapest type of carbon per weight available.
Also, you decide how much you need in the longitudinal direction and how
much strength in the hoop, rather than use some woven cloth or biaxial at a
preset ratio. The whole tube is going to have a continuous fiber structure
rather than a bunch of cuts .This will result in the lowest weight to
strength ratio , so this is no tradeoff, you get it both strongest and
cheapest at the same time .


best regards,
matt

-----Original Message-----
From: RodShea <RodShea@comcast.net>
To: Cord Scholz <cord@astro-image.com>; atm@atmlist.net <atm@atmlist.net>
Date: Tuesday, January 31, 2006 9:50 PM
Subject: Re: [ATM] making carbon tubes


>Cord,
>
>>From what I can tell, tubing is often made by wrapping the
>mandrel-composite-(?bleeder+?breather+release ply) with heat shrink tape,
>instead of vacuum bagging it.  This might give you better control of the
>fabric.  I have not done this, but it seems reasonable.  I would also have
>thought it would work better to cut unidirectional CF to exact width, equal
>to diameter, for each ply, or to do all the layers of uni as one piece,
>rolled around the mandrel.  I'm guessing  the wrinkles come from excess
>width material, meaning > diameter, that becomes a problem when the vacuum
>decreases the effective diameter of the mandrel plus whatever thickness of
>cloth is under the ply that wrinkles?
>
>Rod Shea
>
>----- Original Message -----
>From: "Cord Scholz" <cord@astro-image.com>
>To: <atm@atmlist.net>
>Sent: Tuesday, January 31, 2006 9:01 AM
>Subject: [ATM] making carbon tubes
>
>
>> Hi all,
>> I'm trying to make a carbon tube using an aluminum tube as a positive
>> mandrel. Does anyone know ho to prevent the carbon cloth from wrinkling
in
>> the vacuum bag? In my first attempt I used several cloth pieces that were
>> about 1" longer than the circumference of the tube and moved the seam
from
>> layer to layer a few inches, the result were several nasty wrinkles in
the
>> cf part.
>> I know that there must be a way to do this with a positive mandrel
because
>> I
>> have a sandwich tube that was made this way but I don't how it was done
>> exactly.
>>
>> Cord Scholz
>> www.astro-image.com
>>
>>
>>
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>>
>
>
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