Rolf,
Summer is approaching but it's not that warm just yet.
I went for a short 40km ride today and it was only 12 deg C.

Speaking of cold you reminded me of a little experiment I thought I'd try a week or so back. I tried making a glass tube over a solid aluminum mandrel for a part of my Carbon Chain plate.
Rather than coating the mandrel in candle wax that I'd melt later to release I got this bright idea of freezing the final tube and mandrel to shrink the mandrel for release.
Just in case your thinking of trying something like this don't bother, go with the candle wax. I did finally get the glass tube and mandrel apart undamaged but it took a winch and some snap straps to do it. The glass tube has an inside dia of 12.5mm an outside dia of 18.5mm, 190mm long and weighs 47gms. and it took a 1metre length of 200gm plain weave glass to make.

Below is just a couple of pics of my setup. I spun the mandrel with the drill slowly to wrap the glass around it and then quickly while gripping the glass to compact the layup and remove excess resin. Then applied the peel ply and finally tape.



Once cured the peel ply and tape is removed. This is a good time to sand it if required, while the drill can still spin it.