Guys,
I guess that I'm in the mood to throw my pennies into the pot
here. I have the exact set up that is being talked about here and have no
problem with it for low pressure or CG management. I have in fact been
testing max climb angles and durations at those angles. I don't have the
info in front of me but I can tell you for sure that I have been
getting close to straight up. This morning was 75 deg for sure. I make
sure that the header is full when I am doing this and with the 3100 it
will climb pretty long before the speed bleeds down to where I push it
over. I took it down to 65mph indicated today. the fuel pressure
indicated .6# yet then.
As far as the CG and transferring fuel from the wing tanks it
really doesn't add much work load. On X-C flights I transfer fuel once
per hour. In other words I turn on the pump. It takes 15 to 20 min. to
refill the header to full and I repeat at 1 hour after the header was
full. I use very little trim adjustment if any during these cycles
usually only adjust the trim if I need to let go of the stick to work
with maps or something that I need both hands for. I have flown down to
4 gal left in the header tank and for my plane again the Cg does not seem
to be an issue. Yes it is a little more but nothing that is not well with
in the trim limitations. I actually feel more need to adjust trim from
speed or power changes than anything else.
As for fuel in the cockpit I put that into the personal comfort
decision. I am not bothered with it having the header tank. My personal
idea was if I have to worry about the fuel tank being ruptured I have a
lot of other problems to deal with or maybe not to have to worry about at
all anymore.
I did have a CG just slightly ahead of the forward limit form the
beginning and it most likely a little bit further forward with the
equipment that has been added over the past year. I know that my CG is
well in front of the last 2" of the rear limit.
Bottom line is the 2S is a very stable platform and both systems
of carrying fuel will work well.
I vote no on the header tank only also. It just reduces the options that
you may need some day.
Joe Horton, Coopersburg, Pa.
[email protected]
>
> "Keeping the header tank"...yes, as long as you also have wing tanks
> or a
> fuselage fuel cell like Bill mentioned. Header tank ONLY, I'd vote
> no.
> With wing tanks only, the CG changes very little throughout the
> flight.
> Mine moves a little more than an inch, but if I had a only header
> tank it
> would be at least double or triple that (depending on the size of
> the tank).
> And with wing tanks the CG moves more forward as you fly, unlike the
> header
> tank which moves the CG aft as you fly. Forward CGs make it easier
> to fly,
> and easier to land. Landing is not the time when you want an aft
> CG. Bill
> addresses that by moving fuel to the header, but that means you
> either land
> with extra fuel, or if you make a long flight with very little
> reserve, you
> land with a CG that would be aft of where it would be with wing
> tanks only.
>
> As for gravity being reliable using a gravity feed carb, that's only
> partly
> true in my mind. Gravity feed carbs rely on head pressure alone,
> and when
> climbing with a header tank, head pressure is going to be reduced
> during
> climbout as compared to level flight, which is not the time to be
> running
> lean. Apparently the Aerocarb is set up to run at really low
> pressures, so
> Bill's runs fine, but I've heard stories of some carbs running
> leaner on
> climbout than in level flight. And with only gravity feed, clogged
> filters
> or other obstructions can make a huge difference. With pumps there
> is a lot
> more "headroom" for such things. That's not to say that there
> aren't a lot
> of KRs flying around with header tanks only though.
>
> I do think that if you've got a gravity feed carb feed (or even a
> regular
> float bowl or pressure carb), a small header tank (used in
> conjunction with
> wing tanks) which you keep full all the time is probably a good
> idea. But
> you'd need to rig an automatic pump system to keep it full, a
> warning to
> tell you when it's not, and an overflow back to the tank for when
> something
> goes wrong and the pump doesn't shut off when it's supposed to. I
> think Ron
> Eason made something similar, as well as Don Reid and others. This
> makes
> sense, if you don't mind fuel in the cockpit.
>
> Mark Langford, Huntsville, Alabama
