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<DIV><FONT face=Arial size=2>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. </FONT><FONT face=Arial size=2>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. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Wayne Galligan</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV>- Original Message ----- </DIV>
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<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=Jim_Woodward@beaerospace.com
href="mailto:Jim_Woodward@beaerospace.com">Jim_Woodward@beaerospace.com</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, August 13, 2004 7:54
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: hopper theory &
practice</DIV>
<DIV><BR></DIV><BR><FONT face=sans-serif size=2>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 be reduced
to a section of fuel tubing that is "bubbled"? Would the "bubble" work
is there was a separate entry and exit point like the ven t and clunk lines of
the hopper tank? If the bubble was 5 times larger than the ID of fuel
tubing would it work?</FONT> <BR><FONT face=sans-serif size=2>Thanks,</FONT>
<BR><FONT face=sans-serif size=2>Jim W.<BR></FONT><BR><BR><BR>
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<TD><FONT face=sans-serif size=1><B>ronlock@comcast.net</B></FONT>
<BR><FONT face=sans-serif size=1>Sent by:
discussion-request@nsrca.org</FONT>
<P><FONT face=sans-serif size=1>08/13/2004 08:34 AM</FONT> <BR><FONT
face=sans-serif size=1>Please respond to discussion</FONT> <BR></P>
<TD><FONT face=Arial size=1> </FONT><BR><FONT
face=sans-serif size=1> To:
discussion@nsrca.org, discussion@nsrca.org</FONT> <BR><FONT
face=sans-serif size=1> cc:
Jerry Budd <jbudd@QNET.COM></FONT> <BR><FONT
face=sans-serif size=1> Subject:
Re: hopper theory &
practice</FONT></TR></TBODY></TABLE><BR><BR><BR><FONT face="Times New Roman"
size=3>Ive been a hopper tank diss-believer for years. I also wonder why
many continue to report benefits. What's responsible for the
benefit?</FONT>
<P><FONT face="Times New Roman" size=3>I'm in agreement with Nat, and what "I
think" Jerry has said regarding the fuel system with a FULL hopper tank being
a column of fluid, and the hopper would have no benefit.</FONT>
<P><FONT face="Times New Roman" size=3>Maybe hopper serves to eliminate
foaming and bubbles? Do I understand heli pilots use hoppers for that
reason?</FONT>
<P><FONT face="Times New Roman" size=3>In practice do we usually have some air
in the hopper? Or do we usually have a hopper tank that is flexible?
Might we be drawing from the hopper without replenishing from the main
tank during a vertical? Then the hopper gets replenished during
level lines?</FONT>
<P><FONT face="Times New Roman" size=3>Still wondering, Ron Lockhart</FONT>
<P><FONT face="Times New Roman" size=3>-------------- Original message
-------------- <BR><BR>> >Matt, <BR>> >With or without the hopper
tank we still have a solid column of <BR>> >incompressible fluid for
gravity and G's to play its tricks on. I <BR>> >contend if it runs ok
with the hopper it will run just as well <BR>> >without. Nat <BR>>
<BR>> Nat, <BR>> <BR>> While not exactly accurate as stated, your
point is well taken. Your <BR>> hypothesis has some merit when the tank is
full, but it falls short <BR>> anytime else (which is most of the flight).
Adding just a small <BR>> amount of air causes the system to become
compressible (just like the <BR>> brakes on your car). <BR>> <BR>>
Jerry <BR>> -- <BR>> ___________ <BR>> Jerry Budd <BR>>
mailto:jbudd@qnet.com <BR>> ===================================== <BR>>
# To be removed from this list, go to http://www.nsrca.org/discussionA.htm
<BR>> and follow the instructions. <BR>> </FONT>
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