I first ran into this too many years ago in engineering statics. A = head or=20 column of liquid exerts a pressure per unit area only=20 dependant on how high the column and the density of the = liquid. No=20 calculus involved to calculate the pressure at the bottom if the density = can be=20 considered incompressible such as fuel or water, but not air if the = column is=20 very tall. Now if we wish to calculate the total force on a dam or a = container=20 that has a vertical component, then we need calculus to be able compute = the=20 force. Do not have a neat analogy at the moment to explain it = better.

One thing that grabbed me was to calculate the force exerted on a = dam is=20 that you only need the dimensions of the dam and density of the liquid, = ie it is=20 independent of how far or how much water is backed.

If we build a dam that backs a tremendous amount of water and now = build a=20 second dam just upstream of it, the force on the first one will not feel = any=20 change. Now if we pump all the water from upstream of the 2nd dam, the=20 downstream or original dam will still not feel any difference, but = the 2nd=20 dam will now feel the same force in the opposite direction. Hope this = might=20 clear the muddy water a little :>)

Back to original question of where to dump the return fuel. I doubt = if the=20 pressure at the fuel injection point will be changed as a function of = where you=20 put it back in the tank. This assumes the regulator does not hit a limit = of=20 travel.

Bernie Kerr, 6A sold :>( Hopefully 9A rotary flying = soon.

----- Original Message -----

From: Bob Darrah

To: Rotary motors in = aircraft

Sent: Friday, February 13, 2004 = 6:23=20 PM

Subject: [FlyRotary] Re: EFI = Fuel=20 Pressure

----- Original Message -----
From: <echristley@nc.rr.com>
To: = "Rotary=20 motors in aircraft" <flyrotary@lancaironline.net>
Sent:=20 Friday, February 13, 2004 3:29 PM
Subject: [FlyRotary] Re: EFI Fuel = Pressure

Snip
> Actually, the rest of the feul will exert = some=20 extra force on the column,
but it requires calculus to figure it = out and it=20 won't be much.
>

I must have been playing hooky the day = they=20 taught that. Could you explain
that just a little more? = It=20 doesn't correspond to my learnin and
experience.

Bob=20 Darrah

>> Homepage: http://www.flyrotary.com/
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