Not very fancy but easy to do..........  Use a section of rocket body tube and fuel proof it.

How about an aluminum cigar tube? Very light ~ 1/2" diameter. And each tube comes with a treat inside.

In Dale Kirn's article for the Lil Pronto (American Modeler, Sep/Oct 64) he shows a hard tank and a soft balloon tank. The balloon tank (attached, might need to enlarge to see details) is not inflated like a bladder, just used as a soft fuel container. He said to squeeze all the air out then fill without inflating so that when the filler is remove no fuel comes out. Seems this then just collapse as the fuel is drawn out by the engine. I think one could do this type of non-pressure soft container by using fingers from a large vinyl or other type of glove. This way you could see fuel/air in the fuel sac and get out the air. I think this would fit in almost any shape holder like oval shape, smooth wedge or round and sit on the side of the fuse nicely. I intend to try this on the test block and see how the whole thing works. If anyone has used this approach please post your experience with it.

Did a little search and the RC pylon and combat guys have been using this type tank for quite a while it is called a Bubbless fuel tank system.

Best,    DennisT

I was reminded of the "little red nozzle caps" from a Q on Barton site. These are like finger protectors but smaller and used to roll onto the end of clack tubes to seal them after use. They are available from ACE Hardware (and eBay, Amazon) about $6 for a 10 pack. Should be just the right size for 1/2A with low/med pressure.

Best,   DennisT

check classafied for 10cc brass profile tank