Sorry Guys, I think I didn't give enough info so some missed the point...
First of all, it is for a boat, so will not be going into a smokebox ! Effectively I want to put a collar on the tube (chimney) but am unsure how to go about it... I will probably use layered plasticard, but am looking for suggestions on how to curve this so it fits the diameter of the tube. Do I roll it, or heat it or any other suggestions...
Not quite a railway question, but modelling in general.
I have a steel tube, that will be a chimney, but I want to make the bottom thicker in diameter - any suggestions how to do this?
It will be stepped, so no need to round of edges etc and will be painted red on completion (it's a boat chimney by the way)