Bob
):-{])) <---- madden@netcom.com madden@svpal.org Remember amateur astronomers: "keep looking for the next Universe"
On Thu, 20 Apr 1995, Bratislav Curcic wrote:
>
> Get the lightest carboard tube / sonotube. Peel off waxed layers
> (if there is any) and epoxy two layers of Kevlar or Carbon fibre
> (one outside, one inside). Give another layer of Kevlar/Carbon in
> stressed areas (around focusser, primary etc.). You'll end up
> with lightest and strongest tube you've ever seen !
>
> I've made tube out of balsa wood and Carbon fibre for my Wright.
> It hardly has any weight (around 300 grams for tube 8X23"), but it is
> unbelievably strong (no trace of flexure whatsoever)! Another plus is
> that Carbon has almost zero coefficient of thermal expansion.
>
> PVC tubes sag, attract dew, and are just too heavy. They will also
> expand/contract under temperature by few mm !
>
> Bratislav
>