| F2B is probably the
last area of aeromodelling that I should brave to comment
on (on which I should comment!). My list of bad engines and
clunky aeroplanes would fill quite a few pages.
Others, Al Rabe, Bob Hunt etc have certainly
filled a few pages with their successes. However, being a
failure has never stopped me before, so here are some reminiscences
and thoughts for the future on F2B Stunt.
My interest in Stunt was first piqued in about
1960, when I visited Sydney's Centennial Park to watch a stunt
comp. I was stunned by the gorgeous Thunderbirds of Ian Brown
and Ron Diprose, not to mention Paul Turners beautiful "Peter"
Commanche style-airplane. I was hooked, so it was off to Hobbyco
for a Mk6 T'Bird
and OS35 Max3.
This model had a chequered career. It think
I got a third place in one comp, but I could never get that
motor to run right. The model suffered various indignities,
including Gary Lynch taking off the inboard wing with a combat
model. Still, the wing glued back on all-right; the model
meeting its ultimate end at the 1964 Victorian Nats when both
lines broke and it went through the rear window of the passing
garbage truck. I thought the driver might get mad, but he
just sat there and didn't move. He was still sitting there
an hour later. Maybe he was dead.
By the way, that was the era of the gorgeous
Victorian giant stunters, all beautifully finished with Olde
English lettering and very swank.
"Angelique" was number one by me,
but others were the "Shark 45", and John Hughes
"Rebel", with Kyowa 45 engine. The latter model
flew at a beautiful constant speed, leaving a strong impression
on me. If only I had a motor that ran like that!
But returning to the Thunderbird: Palmer had
introduced differential flaps, which used independent horns
on each flap. By using a shorter horn on the inboard flap
to give more deflection, the effect was to roll the model
out on the lines during manoeuvres. This worked a treat; you
could wind in the overhead eights really tight. Its rare these
days to see overhead eights about the 45 degrees required.
But with the T'bird, you could lie on your back and do them
till the tank ran dry. You were in trouble then, of course,
but being younger we could jump up and land safely. These
days, just a loop gives me a heart attack.
In the late '60's, I was impressed with Dick
Mathis "Chizler" design, which he claimed to fly
very slowly, something like 45MPH. Now our T'Birds were screaming
around at 60 MPH, and you really needed good reflexes. Cutting
furrows in the grass with the fin was not uncommon.
But the T'Bird would not take to being slowed
down, at least for me. The problem seemed to be the flaps.
While the model rolled out nicely in the loops, it over-rolled
in the squares. At high speed, you didn't see this. So in
the late '60's I came up with my "Rivets" design,
which had "constant differential" flaps.
The problem with the Palmer differentials was
that they were progressive.
More deflection gave more differential between
the flaps.
In my system, again two horns were used, but
this time they were the same length. However, the outboard
horn had a horizontal slot instead of a circular hole. This
way, the inboard flap deflection always lead the outboard
flap by a fixed amount.
This remains the sweetest flying model I ever
had, and I remember with affection the days flying in Centennial
Park with Reg Towell, Ron Nyberg, Will Sutton, Ian and Robert
Mooney, Ian Korner, Tom Barry and others. We always had a
lineup of 6 to 8 stunters every Sunday. Actually it was Ron
Nyberg who sold me the best Stunt motor I ever ran.
He pulled this beat-up looking Enya 35 6001
out of his pocket and sold it to me for $3. This was really
a dubious buy, it had bits of araldite stuck to it and looked
horrible. But it had exhaust lugs that were strong and you
could hang an OS "Jetstream" muffler off it no trouble
at all.
But mostly, it ran beautifully! You set it rich
on the ground, with just enough power to get the model rolling.
This gave beautiful long take-off rolls which were very impressive.
Once in the air, it lumbered around slowly picking up revs
until by the time the reverse wingover was called the power
was there. Every time!
That is, until the Northam Nats, when the rod
let go. That motor had so much running the crankpin was worn
triangular!
At about this time (1973), Dave Campbell built
the first "Anna Domini", which was published in
"Airborne" magazine. This was the first of the long-fuselage
stunters. The earlier designs, including "Angelique",
were short moment models, reflecting I feel the Palmer and
Aldrich set-ups. But "Anna Domini" was more than
48" long, a trend continued by Reg towells "Caudron
C-460" series and Brian Eathers "Firecracker"'s.
In "Anna", I abandoned differential
flaps in favour of a new system. The problem with differential
flaps, of any type, was that the increased lift on the inboard
wing also produced increased drag. So while the model rolled
out nicely, it also yawed inwards. This compromised the line
tension, especially in the square eights. That is not something
you want on a slow flying model.
The solution seemed to be some sort of outboard
spoiler. The spoiler would reduce lift, thus rolling the model
out: and at the same time increase drag, thereby yawing the
model out as well. This is the best of both worlds. Furthermore,
the spoiler can be retro-fitted, as the mechanism is all external.
I flew this set up at the '74 Camden Nats, but
my luck was really out that year. Firstly, I had an undercarriage
leg break off in practise. Then in the first round, I had
my silicon fuel line split where it entered the venturi, stopping
he motor dead after the loops. Finally, the heat affected
my black and red finish, so that the spoiler jammed over-centre,
leaving me with a model flying severely wing-up. Sheesh, some
days you should just stay in bed!
Now in the year 2001 I have another shot at
this idea. Recently I have retrofitted my Eather "Firecracker"
with an outboard "anti-flap". I didn't want the
spoiler, due to the over-centre problem. But the new method
won't do this. Check out the photos.
A small flap is mounted near the tip of the
outboard flap. A simple linkage drives this flap in opposition
to the main flap, thereby always rolling the model out, and
also yawing it out. Test flights so far have been very good,
plenty of line tension everywhere, and no possibility of jamming.
Now I've just got to fix my tank problems!!!!!!
Finally, there is a secondary trimming problem
I want to address. The fore-and-aft position of the tip weight
has always worried me. Should the weight be near the leading
edge, on the C/G or near the trailing edge??
When a model turns, one would assume it turns
about an axis that passes through the C/G. But where does
the rest of that axis pass? If it passes thru the inboard
tip leading edge, the model will yaw outwards. Conversely,
if it passes toward the outboard tip leading-edge, then it
will yaw inwards.
Maybe the tip weight position needs to be adjustable
fore-and-aft for trimming purposes.
Well there you are folks. Would you like to
hear about all my dud stunt engines next? |
