I don't know the size of your header tank, but if it
is small consider the unused fuel recirculating
between your fuel log and header tank time and time
again and how much heat this can generate.  This is
why on most installations it is returned to a large
tank where it can be mixed with cool fuel. I don't
think shielding or cooling the pumps gets to the
problem.  Be careful guys!  Jim Coffman
--- Haywire <haywire@telus.net> wrote:
> Glad to hear your incident did nothing more than
> re-arrange your seat
> cushion.  I have never had a situation of impending
> vapor lock (such as
> caviation of the EFI pumps) that turning on the
> boost pump did not resolve.
> I do however, have my fuel pumps and header tank
> shielded with a fiberglass
> box covered with aluminum foil.  I also have an NACA
> duct funneling outside
> air to the box.  So I think your plans would
> certainly help the situation.
> Plus, you may have a bit more heat under you cowl
> what with the
> turbocharger.  Other than my header pipe which do a
> 90 deg bend and out from
> the cowl - nothing much of a heat producer, also I
> do have louvers on both
> sides as well as a rather large opening on the
> bottom.
>
> Hi Ed;
>     Fortunately our airport is very ideal for flight
> testing, with 3
> separate, long runways and a relatively low amount
> of traffic. I try to do
> my flights when there is little traffic and I always
> maintain gliding
> distance to a runway. One of the benefits of the
> turbocharger and the
> constant speed IVO prop is that I can reach circuit
> height before I reach
> the end of the runway, allowing me to maintain
> gliding distance to at least
> one of the 6 runways at all times and I've practiced
> this as well. I'm aware
> of the "oh shit, this can't really be happening to
> me" time lag that happens
> before pilots take action, but I feel I was ready as
> I run these scenarios
> through my mind, before every flight, so it was an
> automatic reaction to
> quickly assess my options and take the best one.
> While I'm pleased with the
> way I handled it, I'm very angry with myself for not
> recognizing the vapour
> press situation developing sooner.
>     As you may recall, we discussed your fuel system
> off-line way back when
> I was still developing mine and I felt that a larger
> header tank located aft
> of the firewall would reduce or eliminate the vapour
> issues while adding the
> benefit of a useable reserve. As I've just
> demonstrated, this is not the
> case. I wasn't aware that your system is shielded,
> so this reaffirms my
> decision to do this as well. The turbo certainly
> adds to the heat creating
> problems, which is ironic in that it also allows me
> to quickly climb to a
> safe altitude in case of problems, which it is
> adding to... hmmmnn... it's a
> vicious circle.
>     I had earlier considered adding louvers to the
> side as you have, but a
> post from someone indicating that louvers are
> considered to be very high in
> drag, held off my decision to proceed, but I'm again
> considering this. Does
> anybody know of a source for an off-the-shelf
> louver?
>
>   I had considered a fuel line cooler (which they do
> make), but unless you
> are funneling cool outside air to it (and no inside
> hot air) then it could
> make the problem worst by picking up more heat from
> the hotter under the
> cowl air.  In any case, I have not tried a fuel line
> cooler, but would think
> that provided with cooling air, its couldn't hurt.
>
>     I think that by ducting cool air through a fuel
> cooler at the inlet to
> the shroud around the fuel components, it should
> adequately cool the fuel
> without significantly heating the cooling air
> allowing plenty of cooling for
> the pumps and filters. I just have to find a small
> enough cooler to do the
> job. I also use a gascolator on one of my fuel
> lines, which I'm considering
> removing. I have water drains on each tank and a
> sump with a drain on my
> header tank, so I've never seen a single drop of
> water when draining my
> gascolator.
>     How large is your cooling duct to your shroud
> over the fuel pumps? Where
> do you have your inlet for this cooling air? I
> originally considered ducting
> from the rad inlets, but I don't want to be stealing
> any of this cooling
> air, so am considering a small NACA duct on the
> side.
>     Leon has sent me an off-line reply with a few
> additional suggestions as
> well. I'm considering replumbing the header tank
> vent line (which is
> normally closed), back to one of the wing tanks,
> instead of to the vent line
> header. This would allow the boost pump to
> continually recirc cool fuel to
> the header tank rather than just pressurizing it.
> This would also allow me
> to close this vent/recirc line when I do want to
> pressurize the header tank.
>     The reason that I originally opted to use a
> header tank was it seemed at
> first to be the simplest way to manage 6 fuel tanks
> without the hassle of
> returning to a single tank and transferring fuel as
> others have done. I've
> now found that it requires much more management than
> anticipated and is
> becoming much more complicated. If I was starting
> over again, I would
> certainly reconsider this idea.
>
> Thanks for any & all input.
> S. Todd Bartrim
> Turbo 13B RV-9Endurance
> C-FSTB
> http://www3.telus.net/haywire/RV-9/C-FSTB.htm
>
>    "Whatever you vividly imagine, Ardently desire,
> Sincerely believe in,
> Enthusiastically act upon, Must inevitably come to
> pass".
>
>


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