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Alex Varv is best known for his sales and support of the Black Devil
motor in the U.S. but last year he set out to create his perfect
paramotor, basing it on the Kangook frame made by RSUltra in Canada and
a harness by U.S. maker Sun Sails Florida. Everybody has different ideas
on what makes a perfect machine but, in one area we all agree: torque
twist sucks. And in that area, Alex unquestionably has succeeded in
Spades.
The machine is a low hook-in style with a modified version of the
Kangook's gooseneck swing arms. Those arms give the stock Kangook very
good pitch stability. Alex prefers a lower hook-in at the expense of
fore/aft pitch stability so his swing arms don't have as pronounced a
gooseneck shape.
I didn't weigh the machine but it's a hand-start black devil motor so
the weight would probably be about 65 pounds with everything ready to
fly except gas. This was the last machine I demoed at the Salton Sea and
it had finally warmed up. It was calm and 75°F. I weigh about 145 Lbs
and flew it under my 18 m² Pluto.
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Weight: Average for the power and well balanced.
Harness & Suspension: The harness, designed by Sun Sails, was
comfy and seemed well built. There were some prototyping issues that
he's resolved regarding fit but I didn't notice -- it worked quite well
both for launching and in flight.
Starting (-): A properly tune black devil with everything
working is easy to start. This was no exception. Alex pulled the cord so
I don't remember the specifics but it felt standard to me. There is a
good place to hold your hand while starting and the black devil recoil
starter is quite reliable now that they've beefed it up.
Ground Handling & Kiting (-): I didn't get to ground handle
because it was calm but standing around with it on my back for some time was
fine as long as you keep it hiked up.
Launch (-): Typical, smooth cage hoop let the lines come
up nicely and it was easy to get in the seat with one hand pushing down
on the aft part of the seat. Had I tightened the leg loops more I may
not have needed the hnad.
Climbout (-): Great climbout because of the torque twist was
so well managed. I could easily go to full power with no discernible
twisting. More on that important statement shortly. There was some
fore/aft tilting in response to throttle changes until I got fully
seated. This slight pitch instability, like many low hook-in machines,
is likely because the pivot point is below the thrustline. It's absent
once seated which is why most pilots don't mind it.
Flight (-): Comfy with great throttle response. I have a Black
Devil motor and this is one of the things I like about it -- predictable
throttle response throughout the range with plenty of thrust.
Weight Shift (-) Excellent weight shift of at least 6 inches of riser movement
with minimal effort.
Torque (-):
Here is where the machine shines and why I was so keen to try it.
Remember there are two dimensions to torque,
weight shift (roll axis) and yaw (vertical axis). The prop twists
counterclockwise (viewed from behind) so you will twist
clockwise--that's right weight shift torque and does very little. The
big bugaboo is the part of torque that makes your body twist (yaw) left
which redirects thrust. When you see someone crash because of torque,
it's this element of torque at play. I call this the horizontal
component of torque. Picture a motor hanging back so far the cage is
level with the ground. Throttle up and you'll swing (yaw) powerfully
under the risers. Tilt up and it does it less but still does it as long
as there's any tilt-back.
By offsetting both the risers AND the engine/cage, Alex has managed, for
the first time in MY experience, to eliminate this horizontal component
of torque. That's big. It still weight shifts, but that's almost
nothing. I was able to go to full power and could not tell any torque
turn. It tilted right, causing some weight shift, but didn't yaw my body
left. You've got to fly it to believe it.
I've been wondering for years why nobody simply moves the thrustline onto
the pilot's left shoulder (or right for geared machines) enough to
counter this twisting tendency. Finally, someone has. It's even in the
book (page 241) of the PPG BIble 2 on how to do this. Now I know it
works.
The key is moving the thrustline relative to the risers. Most machines do
so by offsetting one or both risers to the right which works well -- its
just never quite enough. Alex did that *AND* offset the motor and cage
an inch or so left which turned out to be key.
Thrust (-): Good. Probably 135 pounds worth and easily usable.
Endurance (-):
The Black Devil is a thirsty motor. The tank is large enough to
probably get two hours on a reasonably efficient wing.
Vibration (-): Average -- didn't notice anything more or less
than normal. My eyeballs didn't shake at any RPM range.
Sound (-): Average. No raspiness.
Safety (-): Prop clearance is good but I don't know if it would
pass the hand test on the cage. In other words, you may be able to get a
hand or shoulder into the prop through the cage if it went to full
power. There are some largish openings but they seem to be well away
from where you would be able to get a hand through.
Construction (-):
Seemed well built and reasonably stout with appropriate reinforcements.
The cage is offset so it doesn't look perfectly symmetrical but that's
its secret. Changing that will ruin the remarkable torque management.
The
Reparability (-): One nice thing is that all three cage pieces
are identical. So if you dink one, it's probably cheaper to get a
replacement. There are lots of curves so, although you can re-weld it
(aluminum) you'll eventually want a new piece.
Transport (-): It looks like it comes apart as easy as any and
having the cage pieces all the same make them compact to box up.. Overall:
For anyone who likes low hook-ins, this is a great selection. By largely
conquering torque, Alex has hopefully paved the way for all machines to
eventually follow. At least we know its possible.
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