Re: [ATM] Carbon Fiber for Spider Vanes

[Bruce MacDonald <brumac@gmail.com>]

Wow!
I didn't know that you could get CF that thin!  That is thinner than
the spider that came with my scope.  That particular spider has the
opposite problem -- It is so rigid that it is not possible to shift
the secondary by adjusting the mounting bolts.  Couple that fact with
the fact that the tube is too thin (or not rigid enough) for its
diameter.  What happens is that when I attempt to adjust the secondary
position, the tube goes out-of-round.

Can you divulge the source you use for Carbon Fibre?

Note:  I realize that my first reply went off-list.  I'm copying this
message to the list.

--BM

On Apr 3, 2005 12:44 PM, Peter <peter@kitgear.com> wrote:
> Hi Bruce,
> 
> I am currently planning to make 0.035" thick vanes for my 16" scope. Do you
> think this is too thick?
> 
> You and I think much a like because I used scrap strapping to make the
> spider for my briefcase scope http://www.kitgear.com/atm/briefcase.htm. It
> is 0.025" thick but only 3/8" wide. I find this combination of width to
> thickness not stiff enough because the secondary does rotate a bit when
> adjusting the mirror. For a small portable scope it does OK though. Your
> 5/8" width should  be better especially if you go for 4 vanes but you may
> want to go a bit thicker if you chose 3 vanes.
> 
> Good choice!
> 
> BTW - Carbon fiber is also conductive.
> 
> Thanks for your response Bruce.
> 
> Regards,
> 
> Peter
> 
> -----Original Message-----
> From: Bruce MacDonald [mailto:brumac@gmail.com]
> Sent: Sunday, April 03, 2005 3:34 PM
> To: Peter
> Subject: Re: [ATM] Carbon Fiber for Spider Vanes
> 
> Would it not be too thick -- and therefore create more prominent
> diffraction artifacts?
> 
> I've just begun to experiment with this stuff:
> http://www.signode.com/na/systems_products/sss_strapping.htm
> It is very thin (I'm trying the 5/8" .017" thick stuff).  This allows
> the position of the secondary to be adjusted with the secondary
> mountings.  Also, since it is conductive, I can use two vanes to carry
> power to my dew heater, as long as I use non-conductive mounts of
> course.
> 
> It also has the advantage of being considered garbage by most people
> who have finished with it.
> 
> What other design considerations come into play?  Esthetics?  Weight?
> 
> --BM
> 
> On Apr 3, 2005 10:20 AM, Peter <peter@kitgear.com> wrote:
> > Anyone have either good or bad experiences with using CF for making spider
> > vanes?
> >
> > Excluding cost is this a good idea or not?
> >
> > Thanks,
> >
> > Peter
> >
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