Extend Cox 049 run time with a remote tank

Although I’ve always enjoyed flying 049 size airplanes, one thing I don’t like is the short flight time that you get from a standard Cox 049 integral fuel tank.  The logical solution to this problem is to use a “product engine”, which is one of those engines found on the plastic airplanes that Cox used to sell millions of.  They come with a plastic backplate with mounting holes and an external fuel nipple for use with a remote tank.  You can also mix and match by taking the tank assembly off of a Babe Bee, Black Widow, Texaco, etc, and replacing it with the plastic backplate from a product engine.

On the plane in the photos I used a product engine from eBay and a one ounce Perfect metal fuel tank.  I soldered forward pointing brass extension tubes to the tank and drilled holes in the fuselage with the correct spacing to match the tubes.  Here’s a photo of one tank in its unaltered form, and the fuselage with the modified tank installed.


To get the brass lines through the holes I inserted a 1/16″ wire through one hole into the radio compartment, then stuck the brass tube over the end of the wire.  When I pushed the tank into the tank compartment the 1/16″ wire guided the tube right through the hole.  Then all I had to do was rotate the tank slightly until the other tube lined up.  Then I epoxied both tubes right into the firewall for an oilproof  installation.  Here’s the tank as seen from the radio compartment.


In the next photo you can see the vent line sticking out of the firewall.  Theoretically the prop blast will enhance fuel draw in this type of installation.


The engines with integral tanks make the incoming air charge go through a tiny tube, which robs the engine of power.  The product engine backplate increases performance by having a shorter air induction path.  I originally had a Black Widow cylinder on this engine, which has dual bypass ports.  You may notice that I like to build Q-Tees without landing gear for a better glide after the engine dies.  The lack of landing gear combined with the high power engine made this a terribly overpowered airplane that I didn’t much enjoy flying.

So I took off the Black Widow cylinder and piston and replaced them with a set from a single port Cox engine.  I also put on a less efficient black Cox propeller.  After all of this fine tuning, or de-tuning, this plane became a really nice flier.

Here’s the radio compartment.  The Q-Tee is a nice plane for learning to build from scratch, and it’s a great subject for experimenting with design modifications.  Be sure to check out my other Q-Tee article about building swept back wings to make it easier to get the center of gravity right.