[pmrid (Peter)]

Blasted rain: it means that I bring out old and incomplete projects and start fiddling with them.
The currect one is designing a truss OTA to house a Dall-Kirkham combo I have had sitting here for a while.
I'm aiming for an open truss system similar (if not identical) to the ones that Royce now makes using open channel struts. I'm wondering about the placement of the central box-section strut and it's positioning in the obverall design. Is there any magic ratio of weohts and distances that should be adhered to? I'm presently planning on a rear section of 400mm and a front of 700. The point of balance, with the optics etc in place would actually be at about 275 from the rear though, as far as my rough maths goes. It's a full-depth mirror of 12 1/2 inches and weighs a bomb.
And does anyone else have any thoughts on the open channel struts?
Peter