I would like to do a temporary second fuel tank on CG. How do I do this?

strap it to the top of the wing,,probably need the center of the tank to be a bit forward of the cg..have to poke a few holes in the plane to do the plumbing ,,is this one of those; just to see if it can be done things?....Rog

I have plenty of room inside, just wondering how I should hook up fuel lines etc.  Would it work?

Sure, you can hook up two tanks. But the big question is why. Remember that when you have two tank you also have twice the amount of things that can go wrong. Unless there is some big reason why you need to run two tanks it would much easier to simply install a bigger tank.

Ken

Reason -  I like to send a plane up longer than 10 Min. And I have the extra tank laying here.

This is an example of the stacked fuel tank system with the plumbing illustrated by RCKen.

There is an eight ounce in the nose and two 24 ouncers on top of the fuselage for a total of 56 ounces and almost two hours endurance. This tank system with three tanks provide an effective way to carry a lot of fuel without the sloshing and subsiquient unporting of the clunks if a single large tank were used and surprisingly still maintains CG at least within reasonable limits however it is neccessary to continually retrim throughout the flight first up then down. The airplane is a Bridi Sun Fli 111 with an OS 70 surpass.

John

Nice set up John!

And that'll show the newbies that your tank DOESN'T need to be level with the carb!

This also brings out the advantages of a hopper tank, 3d Heli's. Or Baffled tanks in C/L stunt. I have used them for long cross-country events (years ago) when we could still ride in the back of a pick-up.
-Snuts-

Hi!
Level with carb is important! That is something us old timers know!

I believe the problem with this set up is greater changes in the pressure that the carburetor sees for nose up and nose down attitudes.
For level flight, there is no problem beyond the added weight.

I put mine side by side in a quarter scale. Used same plumbing setup. Haven't tried it yet..........Too cold to go outside and turn it up.
I manually put fuel thru it and the setup worked ok.

Oh my!! It's made of PEOPLE!!

That would be true if fuel were compressable. Most liquids are not. It is the air ( or lack of it ) in the tanks which does this.

A properly plumbed system would incur no additional problems. e.g. plumb it like a Heli's header tank.

A header type plumbing arrangement, which is what should be used, only pressurizes or vents the very last tank in the chain.
So it is not much different from a pressure standpoint, from running a single tank.

Seemed appropriate since it is green and was reincarnated from two ground up and dead SunFli 3's. And proving an effective utility cross country airplane for the successful XC event I started last year with more to come this summer.

John[8D]

That is true regardless the compressibility of the liquids or gases inside the tanks and hoses.

That is the only reason for which the fuel tank is located right behind the firewall, instead of at the CG.
The change in trim during flight is a compromise for good functioning of any carburetor.

A common form of Bernoulli's equation, for any fluid at rest (velocity = 0), is:

H + (P/Density) = constant

Where:
H is the height of the column of fluid above a point
P is the static pressure at a point

http://en.wikipedia.org/wiki/Bernoulli%27s_principle