Re: [ATM] 64 pound single-pole 18" f/4.3

[Ross Sackett <rsackett00@yahoo.com>]

--- Gil McFarlane <gilboastro@yahoo.com> wrote:

> Great looking scope Ross.  Can you describe the
> carbon
> fiber parts for me a bit and how they were to work
> with?  
> 
> Did you find a source or have to make them?

Hi Gil,

The 2.125" diameter tube was from (I think)
carbonfibertubeshop.com.  The 1/16" thick carbon-epoxy
plates veneered on the pole support stock were from
McMaster-Carr.  

The material was surprisingly easy to work with
carbide tools, Dremel cut-off disks, and ordinary
sandpaper.  You need to be very careful with dust and
splinters, so I always had the shopvac running to pick
up stray particles.  I cut the tubing with a diamond
wetsaw for tile to keep the dust down.  Being a little
paranoid I dressed up in Tyvec overalls, gloves, and
closed splash goggles (fun in the summer Memphis sun).

We all know how light and stiff carbon-epoxy is, but a
major downside is that its strength can be limited to
certain directions and planes.  For example, the
tubing had to be supported by internal plywood disks
to keep it from splitting at the clamping points.

It made sense to use some carbon in this project
because I was trying to save more weight.  The
non-carbon blue version of the scope I took to the
RTMC weighted 76 pounds; the new version with carbon
and some sandwich construction reduces this to only 64
pounds.

Would I use carbon again, say in a conventional scope?
 Nope: it is too expensive, finicky, and has safety
concerns.  This scope was fun to build, but I will
probably stick with wood and aluminum in the future.

Ross


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