Fuel foaming

[jivey61 at bellsouth.net]

> Richard
 I just experienced a problem that will be of interest to all.A friend spotted bubbles so small, in my DZ fuel line, that I couldn't see them. At the nats my plane noise checked at 92 when most all  others were 89-90. Mine was also loud to the ear( like bark).  When I figured out what was happening to cause both of these problems it was simple. When I used teflon tape around the front bearing of the Dz to make it tighter in the nose ring and hold the engine better I caused the engine vibration to be transmitted to the airframe through the nose ring. The fuse was a virtual sounding board which amplified all the engine noise. This created very tiny bubbles and ran up the noise level.I watched the tank while running at high speed and it looked like a fish frenzy in the water,the fuel  jumping up and down.
 I took the tape off the front bearing housing, the nose ring is loose, the fuel is calmer and my friend can't see tiny bubbles anymore,and the engine has that calm muffled sound again.
Seems like I heard of this before.I will have a loose nose ring from now on.

 More war stories.
Jim Ivey

> From: "Fletcher, Richard" <Richard.Fletcher at gs.com>
> Date: 2004/08/13 Fri PM 04:53:46 EDT
> To: "'discussion at nsrca.org'" <discussion at nsrca.org>
> Subject: Fuel foaming
> 
> I have heard that adding a capful of Amorall to a gallon of fuel eliminates
> all fuel foaming.
>  
> 
> -----Original Message-----
> From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On
> Behalf Of Rcmaster199 at aol.com
> Sent: Friday, August 13, 2004 4:52 PM
> To: discussion at nsrca.org
> Subject: Re: hopper theory & practice
> 
> 
> 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 <mailto:wgalligan at goodsonacura.com>  
> To: discussion at nsrca.org <mailto: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 <mailto:Jim_Woodward at beaerospace.com>  
> To: discussion at nsrca.org <mailto: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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