Rolf,
In reply to your questions:-
First the bag is made from some clear plastic and packaging tape. It doesn't have to be strong just air tight. The mould takes all the load.

Second part is a bit trickyer. The carbon is layed out flat and wet out. The width of the carbon is just greater than the dia of the tube to be made. It is layed over the bottom half on the mould (centred) The bag with a bit of 16mm dia conduit inside is layed on top pushing the carbon down into the mould. The carbon is then folded over the bag overlapping. The top of the mould is put on and hose clamps fixed in place. This is the hard part because the tube to be made is only 1 inch in dia and the carbon wants to unfold itself. So you need a second pair of hands to slide the top half of the mould along as you fold the carbon. With hose clamps in place just inflate the bag. End result is a shiny black carbon rod.

The mould is just aluminium tube sliced down its centre and lined with packing tape (because it is so shiny) and coated in PVA as a mould release.

There are 3 different ways that I know of making carbon tubes depending what you are going to use them for.

Did you have anything in mind?

Regards,
Phill