Dirty Dan!!!

[Randy Ryan]

Dan I read your post about multiple tank setups in the weird tank setup thread. NOW GUYS I DON'T WANT TO START UP ANOTHER BASHING SESSION, THIS IS A LEGITIMATE QUESTION.

I've been thinking about a dual or multi tank or chambered tank setup myself to try to balance feed better from beginning of run to end. The issue I always corner myself with is how you fill the buffer tank from the feed tank and get all the air out of it. Do you have anything you could share on that?

[dirty dan]

Randy,

Good question! Not sure I remember the answer. This was all done several years ago and I was merely winging it anyway. Plus testing sessions with Impact setup were augmented with use of a "normal" hard tank (built to specs Brett supplied on SSW). About my 2nd or 3rd hard tank it all came together with really nice runs and so I lost interest in 2- and 3-tank experimentation.

As I recall pipe pressure was used and of course on 20FP-powered Skyray with three 1-ounce tanks it was muffler pressure.

This is a weasel answer but remember pretty much treating multi-tank setups as if they were merely one tank. Fuel goes in here, vent is there. Okay, there has to be more to it than that and I suggest that a bench mock-up, especially for a clever guy such as yourself, will answer a lot of questions prior to burying it all in a built-up fuselage.

The basic idea is worth it in my opinion even if I ended up bailing on the whole concept. Put the big tank where convenient. Snuggle the small tank right up against back door of engine, mount it such that it can easily be raised or lowered, moved left or right, even cocked to place rear of tank such that fuel cut-off is as desired (no warning, lots of warning, screaming dead-lean run just to freak everybody and so on).

As it happens I am throughly cleaning my shop. Should I come across my tank setup or even some notes made during testing I'll let you know.

My best,

Dan
   

[Randy Ryan]

Randy,

Good question! Not sure I remember the answer. This was all done several years ago and I was merely winging it anyway. Plus testing sessions with Impact setup were augmented with use of a "normal" hard tank (built to specs Brett supplied on SSW). About my 2nd or 3rd hard tank it all came together with really nice runs and so I lost interest in 2- and 3-tank experimentation.

As I recall pipe pressure was used and of course on 20FP-powered Skyray with three 1-ounce tanks it was muffler pressure.

This is a weasel answer but remember pretty much treating multi-tank setups as if they were merely one tank. Fuel goes in here, vent is there. Okay, there has to be more to it than that and I suggest that a bench mock-up, especially for a clever guy such as yourself, will answer a lot of questions prior to burying it all in a built-up fuselage.

The basic idea is worth it in my opinion even if I ended up bailing on the whole concept. Put the big tank where convenient. Snuggle the small tank right up against back door of engine, mount it such that it can easily be raised or lowered, moved left or right, even cocked to place rear of tank such that fuel cut-off is as desired (no warning, lots of warning, screaming dead-lean run just to freak everybody and so on).

As it happens I am throughly cleaning my shop. Should I come across my tank setup or even some notes made during testing I'll let you know.

My best,

Dan
   

Thanks Dan, I'm thinking allot like you were. I think it has some merit for several reasons. Adjustability as you mentioned and I think with the right size and proportioned main tank you could better equalize the head on the needle valve though not completely. I may start tinkering with it, there's gotta be a way.

[Doug Moon]

I have seen this on some large scale RC planes. Large tank in the middle of the plane with a pump that feeds a smaller tank right behind the motor.  The motor draws from the little tank easy enough due to its size.  And ease of draw and short fuel line means hard maneuvers wont shut it off.  Very cool stuff. 

[dirty dan]

Randy,

Nothing to add, but there is a correction to make. That Skyray 35 mentioned earlier did in fact have three 1-ounce (round) clunk tanks fitted, just not in the manner I described. There were two tanks on left side of fuselage and they were indeed stacked vertically. However, lower tank fed a tank mounted to right side of fuselage and did so via piping punched through fuselage.

Dan

[Steve Hines]

I seen 2 tank setup on Heli's but I never ask how it worked.

Steve

[Curare]

The idea of a surge tank is nothing new, and yeah it'll fix a lot of fuel starvation problems in high G (or just plain crazy heli) manuevures. If I recall correctly you rely on having enough fuel in the chamber that you can do whatever you need to, and even though the fuel to the surge tank may be weakened or interrupted, the engine won't notice it, as the fuel draw from the surge tank is easy.

We used to run these on some motors that weren't pumped, so we could have the tank on the CG (no CG change as the tank drains), but with the advent of pumped motors, this became a bit of a non, wheras they're pretty prevalent in glow powered choppers.

Not sure what it would do in a CL setup, and more to the point, isn't what were describing, a chicken hopper tank of sorts anyway?

[Randy Ryan]

Randy,

Nothing to add, but there is a correction to make. That Skyray 35 mentioned earlier did in fact have three 1-ounce (round) clunk tanks fitted, just not in the manner I described. There were two tanks on left side of fuselage and they were indeed stacked vertically. However, lower tank fed a tank mounted to right side of fuselage and did so via piping punched through fuselage.

Dan

Thanks Dan, I've really been thinking about this allot and I will be bench running a few configs when winterlets go. Not quite what you describe, but a pure airless system.

[Douglas Ames]

From what I understand, it takes the sloshing effect (uncovered pickup) of a partially filled main tank out of the equation.