Howdy I have a sure start 049 with a Cox International sub induction piston cylinder and a merlin head, a real sreamer on the ground but even with a ballon tank it quits when ever I try to do a loop, what am I doing wrong and is the another tank I can try?
Thanks
Dwayne

Agreed. A simple but detailed picture could quickly help us help you.

I am all for the balloon tanks for both cost and ease of use. However should you decide to have an intergral tank and radial mount, our gracious sponsor, Cox international sells brand new tank sets.
5 cc: http://coxengines.ca/product.php?productid=322&cat=0&page=8

8cc: http://coxengines.ca/product.php?productid=320&cat=0&page=8

Robert

Dwayne, if the balloon is done correctly they are the most reliable stunt tank i have ever used. I use the 9 inch all the time. You should be able to draw the balloon down without any leaks before fueling. The setup you show in the pic should work fine, i would go back over everything again, the 9 inch is kinda hard to scrunch in the small film cannisters so that may be your problem. I use anything i can find for a holder to let the balloon expand and not get kinked. Keep checking i think you will find your problem. Good luck and let us know.

I also wondered if there was a vent on the film canister so that air could get in as the balloon collapsed.

The fuel hose should run all the way to the back of the balloon, and have a couple of holes punched in it.  This prevents the rubber from sealing off the fuel entry.  Suck all the air out of the balloon before filling it.  With all that, reliable fuel draw is guaranteed.

Another thing to check is the ID of your fuel hose.  Standard small silicone tubing as found in the hobby shops is too small an ID to allow good fuel draw.  Texas Timers stocks the "good stuff", 1/16"ID, 1/8" OD (1/32" wall).

Here I was going to suggest moving the tank in board.  The engine may be leaning out too much like the bigger engines.

That's also an idea I was thinking about.
Thanks

Hey Dwane is that a merlin head on your engine, how do you like it? T.J.

      I think you have a great looking plane Dwayne. I run those engines frequently. I have several,  4 of them are real good runners. I've yet to run the (spi) cylinder I purchased. I did though find them to run extremely well on 25% nitro as well as 35%. I use 5x3 versions mostly APC's and the black Cox prop. I have a few Tornado props of this size as well that work well. I just never really could get them to turn up with a 4 pitch prop. I use the Merlin head as well and found that I had to use several gaskets due to overcompression. I'm currently using one of those plugs in a Tee Dee which required 6 gaskets. This may not be a factor when using 18% as you stated. You can press out the spraybar on those backplates and open the venturi hole for a bit more power as well. Ken