In message , David
writes
On Sun, 01 Apr 2018 10:20:28 -0700, Osprey wrote:

I have an external structure Im using to House my smoker.
The roof is 20mm plywood (shed felt on outside) ... I really need to put
in a chimney to allow free flow out of smoke ... a 2€� pipe would be
enough ... though could be bigger, dont really want bigger than 4€�.
Needs to able to let smoke out and stop rain coming in ....

Anybody think of a fitting that I can use ... simple flange fitting
would be ideal ....

How hot is the smoke likely to be?

If you are cool/cold smoking then you might get away with drainpipe or
soil pipe.

Or find someone who still has old iron drain pipes.

Might be something suitable in the galvanised air duct suppliers.

http://www.ductstore.co.uk/

--
Tim Lamb