<br><font size=2 face="sans-serif">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 size=2 face="sans-serif">Thanks,</font>
<br><font size=2 face="sans-serif">Jim W.<br>
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<td><font size=1 face="sans-serif"><b>ronlock@comcast.net</b></font>
<br><font size=1 face="sans-serif">Sent by: discussion-request@nsrca.org</font>
<p><font size=1 face="sans-serif">08/13/2004 08:34 AM</font>
<br><font size=1 face="sans-serif">Please respond to discussion</font>
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<br><font size=1 face="sans-serif"> To: discussion@nsrca.org, discussion@nsrca.org</font>
<br><font size=1 face="sans-serif"> cc: Jerry Budd <jbudd@QNET.COM></font>
<br><font size=1 face="sans-serif"> Subject: Re: hopper theory & practice</font></table>
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<br><font size=3 face="Times New Roman">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 size=3 face="Times New Roman">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 size=3 face="Times New Roman">Maybe hopper serves to eliminate foaming and bubbles? Do I understand heli pilots use hoppers for that reason?</font>
<p><font size=3 face="Times New Roman">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 size=3 face="Times New Roman">Still wondering, Ron Lockhart</font>
<p><font size=3 face="Times New Roman">-------------- Original message -------------- <br>
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> >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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