hopper theory & practice

[Rcmaster199 at aol.com]

If foaming is your problem, then a bladder tank will likely help. If it is 
not, then there will be no change, real or imagined, for that reason. There 
could be other problems tho.

Make little mistake: if the fuel is foaming, the pump will most likely 
cavitate and be of little use in fuel delivery. I have long suspected this to be a 
significant contributor to pump problems we have been reading, by so many of us.

To solve fuel foaming, isolate the tank from the vibratory source as much as 
possible. Any fuel delivery system will benefit, doesn't matter if it's simple 
pipe pressure, diaphragm pump, cline regulator or pressurized tank

MattK
Any one using a bladder tank with their Webra 145 or 160?  Some poeple at the 
local fuel has started using them in sports plane for fuel related problems.  
Seems to sovle thier problems.

Randy
----- Original Message ----- 
From: Wayne Galligan 
To: discussion at nsrca.org 
Sent: Friday, August 13, 2004 10:43 AM
Subject: Re: hopper theory & practice


There has to be more pressure(muffler tap) to the main tank then there is 
draw from the carb in order for this system to work properly.  Inertia can effect 
this as I stated in one of my other posts.  I proved this in my Prophecy that 
had the tank higher then the needle valve and when I pressed a hard negative 
"g" load it would go lean.  At all other attitudes it ran fine, i.e, uplines, 
downlines, snaps, positive maneuvers.  All up it has its merits but the best 
is that it reduces the possibility of picking up air in the main feed line and 
reducing the possible lean run or lean burp, something you don't want 
happening on a turbine or helo engine.  The hopper will reduce the amount of air that 
enters the hopper when the main pickup encounters bubbles of foaming.   The 
hopper pickup will still be in bubbleless fuel (fairly fuel tank) if the tank is 
isolated well enough. Jet and helo guys use then for this reason.  The other 
is if you are trying to move weight forward for a tail heavy airplane. This 
makes good use of the fuel transfer and extra tank instead of adding lead 
ballast.  I think the bladder tank(like the Tettra) is the best alternative to 
bubbleless feed and I am seriously considering using it.  

Wayne Galligan

- Original Message ----- 
From: Jim_Woodward at beaerospace.com 
To: discussion at nsrca.org 
Sent: Friday, August 13, 2004 7:54 AM
Subject: Re: hopper theory & practice



I'll take a stab as why the hopper tanks work.  Liquid may be incompressible, 
but it is "movable".  The hopper tank has a fuel entry and exit point.  Exit 
point being the clunk line that goes to the engine, entry point being the vent 
line.  The hopper tank becomes a reservoir of fuel.  Although I think you can 
argue that the entry and exit point fuel velocity (or suction force) is the 
same, this cannot be said for the middle of the tank were the suction force is 
diffused over a larger volumetric cross section.  The image in my mind is a 
wind tunnel's stilling chamber.  I think an interesting question would be this:  
How small can a hopper tank be to still provide the ease of fuel draw we are 
looking for?  Can the hopper tank
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