I've done both auxillary fuel tanks that did not drop, and also dummy tanks that did drop. I haven't had much success dropping a real aux fuel tank after the fuel is gone - mostly because of the separation of the fuel line - really a lot of trouble to accomplish, and not always reliable.

The non-droppable aux tanks are really easy (on the fuse centerline). I take the scale tank, cut it apart around a convenient panel line and then find the biggest plastic bottle that will fit into the scale tank. I always get funny looks at Walmart/Kmart when I'm looking for shampoo bottles that fit - BTW, round shampoo bottles are about the only bottle that will work. Most of the others have funny shapes that don't really lend themselves for this project. Plumb the plastic bottle just like any other tank with a clunk, vent, etc., and then I place it at the last point in the fuel system (outside vent line) so it will empty first. My outside vent line is attached to the tank to vent the whole system. Make up some thin ply tabs to epoxy around the circumference where you cut the tank apart, and then drill and screw the front part of the scale tank back on. Feed your vent and fuel lines through the bottom of the aircraft, and the fasten the tank onto your pylon securely. I've never had a problem losing the tank during flight, but make sure it is mounted securely. Most of the time I end up with around 30 or so additional oz of fuel. My F-15 took a 38 oz shampoo bottle, and has worked just fine. So far, I've had good success doing this, and it can add much needed fuel. I've done a Bobcat, a couple of Rookies, and a Skymaster F-15 so far, and all have fed fuel with no problem.

Dropping dummy wing or fuse tanks is really easy using BVM release mechanism. I put wing tanks on my MiG 15, and they worked fine. So far, dropping them over grass on the side of the runway has protected them from damage. Kevin Whitlow has had good success dropping a couple of Nerf bombs off his Bobcat - I think using the BVM system, too.

I'ts not hard, and is fun, plus by adding an external tank you can extend your flight time, but be aware when you take off with a full fuel load, you can sure tell it. The airplane will be heavy, but will lighten up as the load burns off.

Have fun, and try it - it really is easy.

Regards, Les