Genesis, a design by Bob Hunt published
in 1974, is a Control Line Stunter that captured my interest. I am not
exactly sure why this was but I think it had something to do with the long
flat look that it presented in flight. About 1996 I was evaluating a number
of stunter design airplanes and this happened to be one of them. It's funny
when you get a wish granted, as another local builder offered a set of
plans to me. I had every reason to build it and many reasons to get in
my way of finishing it.
Something significant in this design is the use of a "plank" or "yard
stick" style to enhance the look of flat sections in the stunt pattern.
Coupled with a snappy corner, the flat portions of maneuvers end up appearing
quite smooth and flat. In order to achieve this presentation in the pattern
a pilot needs a light airframe to make it around tight corners at normal
flying speeds. Bob designed this airplane to come out at 39 ounces completed.
Most regular stunters come out at 48 to 50 ounces completed. My goal was
just to complete an airplane from the set of plans at whatever weight it
came out at.
During my 1996 flying season, we were experimenting with lightweight stunters
by using modern day .25's instead of later day .35's and getting good results.
Two theories were being experimented with, that of lighter engines in normal
sized stunters and running these modern engines at higher rpm's in a short
2-4 cycle mode to a steady 2 cycle mode.
The theory is that lighter is better and that includes the use of engines
and the OS .25 FP is about 5.95 oz compared to a Fox .35 which is 7 oz.
The idea being with a smaller engine, smaller tank, smaller lines we begin
to move in a direction that allows us lighter airframes in general. I kept
on feeling like many of the airplane designs, were moving in the wrong
direction by making things bigger to support the larger .60 sized motors.
However, there are many different theories that take people in directions
of their own.
In order to pull a lighter airframe around with a .25-sized engine, we
began to change the way we ran our .25's to maximize the engines available
power. Since these engines are not the traditional cross-port motor, they
operate at a much higher RPM than the traditional .35-sized engine that
used 10,000 rpm and the traditional 10-6 prop. In our case we wanted to
operate the .25-sized engine at 11,500 rpm on a 9.5-5 prop. In order to
do this we had to accept that these smaller engines would not run the traditional
4-2 break cycle but a very high rich 2 cycle to a very lean tuned 2 cycle
while pitched up into the climbing sections of the pattern. This was an
rpm range of 10,500 to 11,200 and would sound like the engine was leaning
out as the airplane was pitched up. A fine pitch prop was used in this
set-up to control over accelerations in the descents out of looping maneuvers.
The biggest problem with this arrangement of engine characteristics was
obtaining a steady engine run on the ground before releasing the airplane
to flight. The use of a tachometer was mandatory and our modifying of props
seemed endless. The fact that these airplanes were light allowed this combination
of small new technology engine and standard airplanes sizes to be aligned.
Once balanced the combination was really nice and produced fine performance
for stunt pattern use with newer engines.
My Genesis construction is far from complete, and it has had a number
of years of neglect as it awaits its fate. It is beyond half way in construction
and is worthy of completing. This was not a very small airplane and when
I took it out to get pictures I was reminded of this fact.
The Genesis in this magazine was made with foam wings but my building
skillsI had not progressed to that point yet. For me to do foam wings I
needed tools like a power supply and a hot cutting bow for foam. What was
presented on the plans was the option to make this airplane with built
up wings and so I did what I knew best.
I think with the built up wings I will have a very light airframe as all
wood is of contest grade and is very light.
This design is very narrow, and the OS .25 is a very tight fit width wise.
The wing is large as is the stab. The tail section is a little weak at
this point in the construction and I am banking on the top and bottom decking
making things much more sturdy. Because of this narrowness I had to make
a custom fuel tank that is slightly narrower than any factory made tank.
I will add to this presentation as I make progress on this design.