Help with Fuel Tank Choice .051

Hi Wiztom,

I got a "noreply" message from you outside this site and I answer you here:

This is the simple setup I use for balloon tanks: I buy a party balloon of the proper shape and size  in any convenience or DIY shop. The good thing is the balloon availability in a wide variety of shapes ranging from bulb to oblong, and sizes between 1/2...3 oz capacity that I typically use in my planes powered by the COX 010-090 engine size range



Unlike with the pressurized bladder tank used in C/L applications, you want the balloon NOT to pressurize the fuel when filled to the required capacity, just to remain slack so that the fuel pressure remains constant from full to empty...this consideration may orient you to select the proper balloon size...

The rubber stopper tucked in the tank throat is available in most hobby shops. These typically have 2 pre-drilled holes for the filling and feed lines and a third "blind" one that is used in clunk tanks for vent lines. I leave this 3rd one blind, or if pre-drilled, fill it with a plastic tube whose outer end is heated to melt then flattened first (= heat-butted in my Hunglish terminology)  to act as a seal.


The balloon throat is tight enough to grab on the stopper fuel-tight even without a quick-tie (you know which plastic tie with ratcheted surface pulled into a no-return head I mean but the English name escapes my mind....) But you may use a quick-tie to make sure  surprises are prevented.

I use repurposed stiff plastic tubes of abt. 1.....1,5 inch length as fuel line and filler line lead-outs from the stopper....old ballpoint pen fills....earbud stems...whatever that resists nitro (these do)..the extension to the stiff tubes inside and outside the tank is normal silicon fuel tube.

The filler tube is plugged with a stiff plastic tube piece with a heat-butted end that serves as a plug..the fuel line connects to a small filter before connecting to the fuel nipple on the carb. The one on the pic is said by my hobbyshop keeper to be used on gas helicopter models...transparent and lighter than the normal aluminum mini-filters sold for glow applications.

You may also want to flush the newly assembled tank with some fuel to make sure no foreign material remains in it before you connect it to the engine.

With regular use i.e. not leaving the tank empty for months between 2 uses - that tends to make the collapsed tank internal surfaces stick together -  the tank will serve you for years without rotting.....My experience....and even if rotten or punctured, you only need to replace the party balloon so buy a few from the same size and shape for a quick replacement in future...

I fuel the tank with a 2 oz syringe I buy in veterinary shops...fill the syringe to almost full (if you need as much fuel), connect the syringe to the fill line, hold the plane in a nose up position to allow air captured in the balloon vent through the filler hose, suck on the balloon by pulling the syringe piston further out until no more air bubbles enter the syringe, then fill the balloon until you see fuel beginning to be forced through the feed line to the carb. This is the point you have just enough but not too much fuel in the tank, i.e. no excessive pressurization.

And again, if you want to beef  that beautiful TD049 up in the nose of the plane, you may want to use the Nelson turboplug sold by www.kittingittogether.com located in Lubbock/Tx just the same state you are in...or the insert type heads sold by COX International and Exmodel engines...or the stock high compression COX head...these all work much better on COX 049 engines than the normal glow plug...just for your consideration

Good luck..