Truss Dob Design Questions

Hello,

I'm kicking around building a truss style dob in the 12.5" to 15" class. I plan on basing it largely on K & B's design. But I have quite a few questions about some of some of the components.

1. The Mirror Cell. This is probably the most complicated issue I have. So I shall just ask all the things I can't quite figure out.
1. Is 1" steel really necessary on a smaller dob? I know Ed Tachyert used 3/4" steel on his 18" and Michael Zammit used aluminum. Could I get away with less or lighter material than steel?
2. What the best alternative to a kevlar/nylon sling? My friend had an 18" Obsession and hated collimating it. So I want to improve it there. Do stainless steel slings work better? Or are the double wire slings best? I'm really not too hopped on wiffle tree support or removable cells. The thought of my clumsy self handling such precious cargo as my primary mirror in the dark gives me the willies. I would consider making a tail gate to make it easier to clean.
3. Should the cell be finished black or is raw unfinished metal fine?

2. Connecting the trusses. Does anyone have any experience with Moonlite's units? I was thinking about using the captive blocks on the mirror box and ball and sockets on top. Any comments would be appreciated. Is the a better alternative out there?

3. Spider. Are curved vanes helpful enough that I should consider them for my scope? I know in lager aperature the struggle to maintain enough tension to hold the secondary still, so is it worth it to put them in or would a high quality unit from Protostar or Astro Systems be better? Also should I offset it?

Thanks in advance.

Eric

1) The thing about a lighter cell is that it may not make the scope or mirror box lighter.

The weight of a truss dob is dominated by one of the lightest pieces -- the upper cage.

Lightening the mirror box doesn't help if you need to add counterweights to make the scope balance or if you need a much taller rocker box to reach the balance point.

You need to consider the whole system. Create a spreadsheet and calculate weights and torques. You really need to balance to torques, not weights.

Once you understand this, then ask yourself if you want to make the cell lighter.

Of course, if you are going beyond the fairly conservative K&B design, then you will probably want to save weight everywhere. But with the "standard" K&B, the mirror box weight may not be the limiting factor.