Re: Slow Dobsonian
Bob Bond (rgb@ncube.com)
Fri, 3 Mar 95 09:48:31 PST
I glued two layers of 3/4" plywood together on each side of the rocker
box for my 16" scope. My mirror - upper cage separation is about 64
inches so the total length is a little less than what you have here,
although the weight would be somewhat higher. You probably don't need
two layers on the back since the primary reason for the back is to
provide rigidity to the sides. I have seen truss tube designs that use
an aluminum tube between the sides, rather than a back board. Another
thing that helps the overall strength of the rocker box is to have the
sides and back glued and screwed to the bottom. This "web" greatly
increases the rigidity. Baltic Birch and Appleply plywood are stronger
and more uniform than cabinet grade plywood - you might check into
local availability.
Bob