One would assume that Pete built N500F this
way. The trouble is, by the time *I* was flying it,
the carb heat and the mixture controls had switched
places! Had Pete built it that way all along...or had
it been swapped during the plane's restoration in 1982?
Could be either way.
The one sort of marginal thing here is the location Pete
shows for the mixture: It's *right* on the edge of the
inner curve of the STA 3 bulkhead. Take a look at this
close-up of my cockpit sidewall.
Notice the carb heat on its Kneecapper
support...and the relative position of the diagonal on
the fuselage side. Obviously, if the carb heat had
been positioned on the STA 3 bulkhead, there would have
been a chance that the fuselage diagonal wouldn't have
let the knob come out all the way.
Apparently, you CAN position the knob successfully
there...probably if you put it *right* on the edge of
the bulkhead. But the builder of my plane didn't
like the looks of it, and installed the carb head
control on a 1/4" plywood extension glued to the STA 3
bulkhead.
Note, also, the Very Comfy (tm) kneepad just below the
carb heat control. The previous owner of my plane
had been about eight inches shorter than I; the pads
were probably ideally located for him. However,
with my towering six feet of height, my knees hit the
damn plywood support, instead. This was very
uncomfortable. And, of course, it was like that on
BOTH sides, with the cabin heat control on the opposite
side (albeit on the other side of the bulkhead). I
had previously removed this one, moving the control to
the bulkhead supporting the fuel tank.
Even worse, the two kneecapper plates had been installed
with sharp edges pointing inward. One of the first
things I did after buying the airplane was to carve a
curve into the inward-facing sides of both plates....as
you can see in the above photo.
The Repair
So, how to fix it.
I'd like to have put it smack dab in the same location N500F
had it. But...was concerned about clearance (like the
original builder) and I would have had to strip the entire
old plate off the bulkhead to have any chance of making it
work. Plus I'd have to drill the new holes with the
diagonal potentially getting in the way.
Move it to the fuel tank support bulkhead, like I did the
cabin heat control? Would work...but the area itself
is out of sight from the pilot seat. The carburetor
heat control is pretty important on a Continental; I didn't
want to have to fumble under the panel to work it.
Cabin heat gets turned on in the fall, and off in the
summer. Doesn't get a lot of work, doesn't hurt it
it's out of sight.
So the ideal solution would be to move it to
the lower edge of the top side of the Station 3 bulkhead,
alongside the mixture and the primer.
Two problems there. First, there's not really a good
spot for it. If you look at the first image on this
web page, if I were to install the control equally spaced
with the others, it'd be nearly center in the cockpit...and
a good foot from the throttle. That's bad cosmetics,
and bad human factors. On a Continental, the carb heat
knob should be turned to "hot" before ANY power
reduction. Better to have it close to the throttle.
The other factor is the difficulty in making a new mounting
location on the STA 3 bulkhead of a completed
aircraft. The control itself is designed to go into a
~1/2" thick panel, yet the STA 3 bulkhead is a sandwich
that's about an inch wide. Just drilling a hole for
the control won't work, one has to go behind the bulkhead
and rout out the back of the bulkhead, as the diagram to the
right shows. And that's just too tough to do, with all
the structure, wiring, and piping of a completed aircraft.
The solution: Install the carb heat knob where the
mixture control is located.
What to do with the mixture? Remove it entirely.
Now, some of you are probably going through the roof.
"You need it to kill the engine!" "You need it to
optimize the mixture for altitude!"
Allow me to point out that my aircraft has a Stromberg
carburetor. They were pretty much standard equipment
on Cubs and Champs.
And on these airplanes, the mixture control was an
extra-cost
option...one that not every purchaser chose to have.
"Wha....."
It's pretty simple: The Stromberg actually doesn't
adjust very far. In fact, one cannot shut down the
engine using the mixture...it doesn't lean it out enough!
Altitude-wise, the mixture on a Stromberg doesn't start to
work until one gets above, say, 5,000 feet. And,
despite living in the shadow of the Cascade and Olympic
mountains (on clear days, I can see three volcanos from
pattern altitude), I rarely fly much above 3,000 feet.
So, I removed the mixture control, and ran the carb heat
control in its stead. My A&P would be coming by to
perform the Condition Inspection, and I had him wire the
Stromberg full rich.
Hardest part was getting the nut started to attach the
control itself. As I mentioned, the mounting location
is recessed due to the thickness of the bulkhead. I
slide a socket over the sheath for the carb heat, holding
the nut, slid it up to the mounting location, and tried to
get the nut engaged on the threads. The trouble was,
the socket was too deep to actually shove the nut against
the threads so it could attach.
My solution is on the right... a short piece of tubing
between the socket and the nut to shove the nut hard into
the threads.
Upshot
The hardest part is getting used to the new carb heat
location. My airplane's was located below the
throttle, in approximately the same location N500F had
it. Was pretty darn used that location, and the new
location threw me off. I'd reach down for the carb
heat and find myself caressing my left knee.
Which was resting, quite comfortably, on the Very Comfy (tm)
kneepad.
It's been a couple of months, and I'm starting to get used
to it. It's too bad I
had to do the
change, but I'm happy with it, now.
