Inboard profile tanks

[Russell Shaffer]

It seems that I have heard talk of mounting profile tanks on the inboard side.  This would sure make for a lot more room, but what are the advantages/disadvantages?  I don't see any use in experimenting with things that have already been done by people who are much more knowledgeable that me.  Thanks

[Bob Reeves]

Works fine, actually better than fine on the two I have. One is an FP-20 the other a Brodak 25. Both have Hays 3 ounce clunk tanks on the inboard side with muffler pressure. Run is consistent from the time the engine starts till just before it quits, no change from ground to air or any funnies at all. I was skeptical but wouldn't hesitate to do it again.

[Russell Shaffer]

Thanks, I'll give it a try.  I'm having problems with an old Fox Rocket and a Hayes tank. 

[Larry Cunningham]

It'll work. Moving the tank toward the inboard increases fuel "head"
and pressure accordingly. Of course, that pressure is the result of
centrifugal force on the fuel, and ideally the fuel tank would be
centered on the engine (generalized statement) to minimize fuel
pressure changes with maneuvering changes.

However, a plastic tank with a clunk can pretty well solve the pressure
variation change (which may not be an issue anyway, since higher model
velocity increases pressure, which tends to reduce RPM and limit speed -
negative feedback = stabilty).

Ted Fancher's Imitation design illustrates a very good idea of locating a
profile tank near the center of the fuselage.

If you think that fuel tank location doesn't matter that much, first try a
thought experiment with the fuel tank moved to the outboard and
then the inboard wing tips - absurd, but an illustration of extreme
effects. Then remember how we move tanks up and down a fraction
of an inch to equalize fuel pressure for normal/inverted flight - it's
important for a stunt ship!

L.

"Only learn to seize good fortune, for good  fortune is always here." -Goethe