[Ian Robinson]

I've asked Orion (UK) and they indicate the CFC tube on the AG10 is 2mm thick .... full fibre (I assume this means no honey comb "filler" , just how many layers of 2x2 Twill CF it takes to get 2mm full thickness).
Those astrographs are f3.7 which is more critical wrt collimation and stiffness is concerned than my f4.66 , so I can probably get away with about 1.8mm thickness ( ==> 7 - 8 layers of 2x2 Twill CF cloth ??).

I take it 2x2 Twill cloth is the way to go , rather than Plain or Satin (Harness style weaves) for max stuctural strength and stiffness ?

This means I can get my OTA with a CFC tube down to 14.3kg in photographic mode and 12.8kg in visual mode.
==> I'll still need one more counterweight , but not a 10.5kg one as my photographic mode torque on the scope side will fall from 7.25kgm to 5.23kgm ==> just one more 3.5kg CW to get RA balance (that's lots better !).

That's ceratinly worth seriuously considering either as subcontract job (Composite Components in Perth say they can do my tube .... I am waiting on their quote) .
If they work out too expensive (ie > $300 , I'll opt for to do this as a DIYS project if I can source 2x2 Twill CF cloth cheaply locally , will check on this tomorrow).

If I decide to do the CFC tube as a DIYS project , how thin can I go on steel or alumimium sheet to have a rigid enough mandrel to work on ?

I'm guessing I'd make the mandrel with a bit of pipe acrpss a couple of work horses , and 4 or 5 uniformly spaced plywood or MDF reinforcing forming disks (job for my jig saw ?) , wrapped in gladwrap (the Epoxy releasing agent).

0.4mm thick steel sheet stiff enough if reinforced by some mandrel disks ?

Would flexible plastic sheet be suitable to form a mandrel if it's stiff enough and cheaper than a steel sheet ?

Not ruling out using shiny formica to form my mandrel ....

When rollering the CF soaked in epoxy how much force do you need to apply to shift the excess epoxy ? Is the force requirement similar to painting with a roller brush ?