| Those who bothered
to read last months PANIC epistle may like to hear the sequel,
now that I am back from the South Western Regional C/L champs
in Dallas.
First, my Profi counterweights were still not quite right,
just grazing the inside of the spinner. Jed and Scott in LA
set me right on this so the next lot should be right on. They
were happy with the new "click" in feature, although at first
they thought it should be filed off!
Didn't get to meet George Aldrich, he went into hospital to
have cataracts removed. I phoned him; he is doing very well
and delighted with the results. So to George, take it easy
and we in Oz wish you a quick recovery and want you back in
harness right away! I gave the new 10X5's to Bob Lipscombe
to pass on to George, so now we must wait for the maestro
to test fly them. Incidentally, Bob thought Joe Parisi was
living in Perth! Hey, where are you Joe?
The Doppler sequel is that my FM Tx's failed to have sufficient
range at our secret base in the California desert. They were
swamped by traffic on the crowded FM band in California. I
was getting airline pilot chatter instead of engine noise!
So I bought a little book on aerials and the next step is
to build some Yagi antennas to beam the signals direct to
the Rx., rather than spray my signals all over the place with
the original vertical dipole.
Even worse, my land-lines also failed on the old Castle Air
Force B52 SAC base. This was baffling, as they tested out
fine when I first laid them. The rig comprised two microphone
units connected by 300' of cable in a T configuration to 1600'
of wire back to base and the tape recorder. With no signal
other than a country music station (!) arriving at the recorder,
I set about testing. At the recorder end, I picked up about
40 ohms which seemed about right. Disconnected at the T, the
line was open circuit, also right!
You guessed it. Not bugs, but rabbits. They ate the cable,
leaving one end shorted and the other open! Next time I lay
1080 as well. The black helicopters were also circling in
the distance, but this was definitely Bugs Bunny, that wascally
wabbit.
Moving right along, I have to tell you the folks in Dallas
were so friendly I could scarcely believe.
My reservation at the Sleep Inn was done with a phone number
the guys sent me, but I got the address off the Internet.
So I arrived at the Sleep Inn Richardson to find no booking!
Hell, that was bad. It transpired there were 3 Sleep Inns
in the area, and the one I wanted wanted was neither on the
net nor in the motel guide book! So imagine my joy when, after
traipsing over to the Sleep Inn at Plano, Rosemary the receptionist
managed to find my hotel, and then drove me for an hour through
heavy traffic to get there!
What a woman!. She started her career as a C5 jet engine mechanic
in the USAF, and ended it as an administrator working for
the Air Force Chief-of-Staff. Rosemary, I salute you, and
promote you to Honorary Man.
I think I figured out why that Sleep Inn was not in the guide
book. I woke up at 2am one morning to find ants marching over
the top of me. When I presented some ant corpses and my dishevelled
self to the front desk, the guy just asked me where were the
ants going to? Lucky they weren't Fire ants, which are slowly
spreading into Texas and wiping out the native wild life as
well as motel patrons. They even kill deer by biting their
eyes and sending them blind.
Must also thank Steve Moon who helped me with all the details
and getting to the field, and also Jim Cooke who very graciously
took me to dinner with his family and showed me around the
Model shops. These latter were every bit as you would dream
a model shop to be. Most had a good range of C/L gear, including
reproductions of the original Nobler kit, Fox 35's and fancy
carbon control linkages with titanium ends and machined clevices
(Bobbye Hall's Hobby House, bobbyehall@aol.com).
Outstanding in my memory was the MAL (Model Aircraft Laboratory,
www.flash.net/~malhobby) hobby shop. Run by Edgar Seay, both
junior and senior, this shop has an accumulation of aeromodelling
history going back to WW2. There are ancient kits, engines,
cut-on-site balsa, F/F rubber kits, magazines, you name it.
A real museum, a must-see-when-in-Dallas. If you want Texas
Timers for F/F, you should enquire there.
After all this, the contest was a bit of an anti-climax. It
was about the size of a NSW State Champs, with jet, stunt
and various forms of Goodyear the most popular.
Jet was interesting, as Mr Bailey of Bailey jets was present.
He mentioned all the different problems he came across trying
to weld thin sheet metal into tail pipes and combustion chambers
for pulse jets. These problems are not yet solved: he is looking
at laser welding at present. Among these problems were titanium
contamination of the stainless steel, and oxygen embrittlement
along the edge of the weld. Mr Bailey had spent two years
just trying to get one decent weld out of his new welding
machine.
The Bailey jet has a larger combustion chamber than the Dynajet.
Evidently the Dynajet gives most power when its pulse frequency
is lowest, so that the model emits a moaning sound. Since
the tail pipe diameter is fixed by the rules, it is hoped
that the larger combustion chamber may have the same effect.
Incidentally, I had a portable computer (Acer) with built
in microphone with me, so I was able to do a Dopplers analysis
on the jets. One could see from the Spectrogram trace that
it took the jets about 3 laps to get up to speed. The fastest
there showed a pulse rate of 13800 ppm at 200 MPH on the Doppler.
Stopwatch was a little less, probably due to the slow wind-up.
This was an extraordinary model, by the way. Its appearance
was distinctly alien, enhanced by the jet-black finish. The
outer wing was raised above the out-slung jet, while the inner
was level with the jet. Fuel was 80% methanol, 20% propylene
oxide.
I noticed this chap polishing his valve seats
on a sheet of glass covered with fine abrasive paper. Starting
was all done with the traditional hand pump. Real tough work
in the heat and humidity of Texas at that time of year. There
were some 6 jet entries, and lots of flying.
The Stunters were mostly well flown, although I noticed that
many were too slow to handle crisp overhead 8's in the varying
wind conditions. Many Eather/Firecracker props were in use
on the piped engines, while the unpiped engines wore a whole
range of props, with B-Y&O props most in demand. Also
saw some Stalker carbon-fibre/wood and carbon stunt props.
These were reported to work very well on the Stalker engine,
which has a great reputation for performance and reliability.
I noted that the Stalker props had a lot of pitch at the tips.
The chap who owned them claimed that stunt props work best
if they have a roughened surface finish.
On the subject of pipes in stunt, I noticed one piped model
flew well through the pattern but leaned horribly and screeched
around the circle for about 10 laps before the motor cut.
Some guys had done temperature probe measurements in the pipe
and found that when the motor went lean the temperature went
right up; then it was impossible to needle the motor rich
again.
Also of interest, there were many profile-fuselage stunters
present.
Finally, some insight on fuels.
Bob Lipscombe filled me in on NACA work on water in fuel (methanol).
This is a problem we have experienced in FAI F3D pylon. The
organisers supply the fuel, and it is often contaminated with
water. The result is detonation, and compression has to be
lowered, a very annoying problem for the contestants. Adapting
to the fuel is one problem we don't need.
Methanol absorbs water from the atmosphere quite readily,
so just opening your tin is a problem. NACA found that this
water can form microscopic droplets which, when in the combustion
chamber, become super-heated, then flash into steam and cause
detonation. (I assume from the increased compression)
Now it happens you can test for water in your methanol using
silica gel. You dry out the dyed variety, which I think is
blue when dry, and lower some into the methanol. If it turns
pink, you have water in your methanol, and problems if you
run high compression or want consistent needle settings.
But all is not lost. There is a second form of silica gel,
which looks like sand and is white. It is used for drying
out flowers. You dry this out and leave it in your methanol
for several days and this removes the water from the methanol.
Retest, and repeat if the test fails. You need 500g of gel
for 4 litres of methanol.
If the fuel is already mixed with oil, I do not know what
happens. Bob says it ruins the silica gel. However, it would
be interesting to know if the mixed fuel could be tested with
the blue gel, even if it ruins the gel, as this could save
a lot of heartache. Nitro does not appear to absorb water.
There is some controversy about this, check
out what Lance Smith has to say: Comment
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That's it for this month, keep those cheques rolling in, I
am now destitute from all this travelling. |
