Constructing a dob

Here's the base of the scope without the mirror box:

www.astroshot.com/Dob/6.jpg

It makes it alot lighter at the base and a little narrower. However, the lack of weight at the base pushes up the centre of gravity. Pivot point is now approx 350mm from mirror. Therefore, this would require 28" diameter bearings, which are large.

Any suggestions around this?

Dave,
I took another look at the size of the mirror cell and sized it down. Images are now updated. Nice to see it getting a little smaller again! :0)

With obsessions, you can put counter weights directly behind the mirror cell, so lowering the center of gravity, these are detachable, handy for balancing eyepieces also.

In terms of the sling, why not have it slightly above the center of the mirror, enough so that the supports can be in slightly in so saving on width.

In terms of the sling, why not have it slightly above the center of the mirror, enough so that the supports can be in slightly in so saving on width.

That's what I've done now and allowed a 1/2" gap for the bolt, bolt hole, nut and washer of the split bolt.

With obsessions, you can put counter weights directly behind the mirror cell, so lowering the center of gravity, these are detachable, handy for balancing eyepieces also.

If possible, I'd like to try and avoid having to carry extra weight around.
Instead, I think I will need to look into some sort of spring system or an elastic-type of rope. I'm thinking of bungee cord, but this might be not be elastic enough. Anyone able to think of other alternatives perhaps?

If I do go with large bearings, it's be nice to be able to fold them in two, like on the Obsession UC . However, I'm not sure exactly how to make this sort of hinge & clamp system or where to even get the parts. Looks a little complicated to make unfortunately.

I really cant see bungee cord working, it would have to supply appropriate tension (acting like gravity) in order for the scope to remain balanced, sounds like it would be very difficult to tune.

In terms of the counter weights, its not as bad is it might seem, Obsession supply hollow light weight aluminium tubes with cap ends, I simply filled one of them with enough sand to balance the system. I could have used gravel/small rocks/lead shot or anything that could be found locally.
So in your case, you'd bring the scope abroad and fill up the tubes with local beach sand.