RE: [ATM] Carbon Fiber for Spider Vanes

[Thomas A Simmons <tasimmons@raytheon.com>]

FWIW, The local Ace Hardware has Brass shim stock 0.016 by 1 inch by 36
inches for
under 4 bucks, and Stainless Steel the same size but 1 foot lengths for a
buck.
Both of these were easily cut with tin shears.

Noticed no problems with spiders made from either materials-and I didn't
bother
painting the stainless version.

Tom
Tucson ,AZ

Date: Sun, 3 Apr 2005 16:03:23 -0400
From: "Peter" <peter@kitgear.com>
Subject: RE: [ATM] Carbon Fiber for Spider Vanes
To: "Bruce MacDonald" <brumac@gmail.com>,        "ATM" <atm@atmlist.net>
Message-ID: <NIBBJHBJELJAJOJEJNOBIEMODAAA.peter@kitgear.com>
Content-Type: text/plain;            charset="iso-8859-1"

I'll eventually post how I make the vanes but since you asked I'll explain
it here. I purchased unidirectional CF tape 5" wide 0.007" which I will
laminate into a very thin stiff structure. The stack up is 3 layers fiber
running the length of the vane and the two inner layers rotated by 90
degrees. You can add more layers if you wish. The tape cuts easily with an
exacto knife then epoxy the layers and press them overnight with waxed
sheeting. The epoxy is squeezed out and you are left with a nice flat
sheet.

Thanks Cord for teaching me this!

Total cost for the vanes is $7.55 for the CF plus another $2 for the
laminate epoxy.


Peter

-----Original Message-----
From: Bruce MacDonald [mailto:brumac@gmail.com]
Sent: Sunday, April 03, 2005 3:57 PM
To: Peter; ATM
Subject: Re: [ATM] Carbon Fiber for Spider Vanes


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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