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Date: Fri, 18 Feb 2005 13:39:10 -0700
From: Bob White <bob@bob-white.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Returnless Fuel System - Fuel Cooler
Message-Id: <20050218133910.6a5e1cf3.bob@bob-white.com>
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Hi Todd,

I'll try the return to the tank first.  The plumbing will be simpler 
that way.   Fortunately I don't have to deal with 6 tanks, so I will set
up a system similar to Tracy's where one tank is the primary feed and 
the other is used to refill it with a Faucet pump.  If I have any 
problems with the 1/4 inch return line, I will try your returnless 
system.  If I don't have any problems, I will have a fuel cooler for 
sale at a bargin price. :)

Both tanks are tied together with a 1/4 inch vent line which T's off to 
the engine compartment.  In addition, both tanks have a vent to the 
outside that is oriented to pick up a little ram air in flight.  I don't
see any reason that I can't remove the connection between the two tanks 
the way I'm hooking it up.  Besides if I don't, the return gas will go 
where I don't want it, into the secondary tank. (Murphy's Law)

Bob White


On Fri, 18 Feb 2005 11:12:20 -0800
"Bartrim, Todd" <Steve.Bartrim@canfor.com> wrote:

> Hi Bob;
> 
>     Sorry I didn't get back to you sooner, but I've been tied up these
> last few days dealing with lawyers as we are finalizing a land purchase,
> along with a few other personal commitments (hockey, kids swimming
> lessons, etc...). This thread seems to have run it's course already but
> I'll add in what I can.
> 
>     First OAT. While it does get extremely cold here by most of your
> standards, winter doesn't last forever and we do get some pretty hot
> summers occasionally seeing temps as high as mid 30'sC. I realize this
> still falls short of some of your temps. I don't always log OAT on every
> flight but some of my test flights I did log this, however I'm at work
> and that info isn't. I do recall at least one of those flights last
> summer was at 31C. Unfortunately I painted my wing leading edges dark
> blue, so on a sunny day my fuel temps will often be close to 40C, before
> I even get started. I've seen them get as high as 45C during taxi and
> run-up, with no problems. As soon as I get airborne with flow through
> the cooler, fuel temps immediately begin to drop.
> 	The cooler you've found looks great. I'd have bought that if I'd
> found it before, however I'm satisfied with the one I made.
> 	This nonsense that it won't work is very subjective. I've proven
> that it does work for me, however this is really no different than the
> issue with header/sump tanks. Ed is flying quite happily and
> successfully with his, while I was never satisfied with mine. This is
> probably due to the tendency of builders to not exactly duplicate a
> successful system due to differences in airframe configuration or
> required mission. Tracy on the other hand is quite satisfied with his
> arrangement and apparently it has been copied by several others who are
> also quite happy with it. I know I wouldn't be satisfied with that
> arrangement, but that is why I like the experimental category, as we are
> free to build and experiment as we desire.
> 	If you want to go with this system then go for it, but beware
> that variations in your airframe configuration and flight profile could
> have varying effects. No guarantees from me :-)
> 	If you do have an existing 1/4" return line, I would expect that
> it should suffice as long as you still have an additional vent line from
> the tanks and are not just "T" into the tank vent line to return.
> 	 I should point out that while it has been mentioned that since
> the outlet of the pumps is often less than the ID of the fuel line this
> is your limiting factor in flow. This isn't really the case. A small
> restriction such as this creates a pressure drop through the "vena
> contracta", but much of this pressure is recovered downstream. If anyone
> actually cares about this I can pass along the formula for calculation
> of the permanent pressure drop through an orifice. This means that a
> 1/4" line with a 3/16" restriction at some point will not have the same
> lower flow as a 3/16" line, but will still be slightly less than a 1/4"
> line with no restriction.
> 
> 


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