This year's event had many takeoff failures.. of two sorts. There were frequent deviations
from a straight path, and prop strikes..
The first is generally due to a very short wheel span on the main gears. Presumably because
the area of any landing gear support is included in the planform area, smaller/shorter is better.
Unfortunately, this isn't practical on these planes, which need all the help they can get other
than from the pilot to keep the takeoff run straight. Probably the optimum setup has the wheels
locked to the axle, which rotates in ballbearings in its mount, and has a width about two fuselages
wide. The more difficult it is for the plane to begin a swing on takeoff, the less likely one is
to occur.
I think the square edges on the purpose-built large diameter wheels have a lot to do with their
takeoff problems.. the edges of the wheels need to be rounded a bit so when the plane is going sideways
nothing can bite into the runway surface, and flip the plane around,/or bend the axle.
Large flanges where the axle passes into the wheel itself stiffen it against collapse under a side load.
Prop strikes are also a landing gear fault, and typically performed by taildraggers. This configuration
has problems with rotations.. it must first rotate tail up to minimize drag while accelerating, then
rotate tail-down to lift off. As the payload makes the rotational energies high, the first rotation
puts the prop in serious risk of striking the runway.
A designed-in rotation to takeoff stance, such as a Telemaster demonstrates would be ideal.. The Telemaster
rotates fuselage level in the first inches of the run, and tracks straight thereafter.. but..
that's due to the large horizontal area, and the lifting airfoil on the horizontal, neither of which are practical
for a Lifter..
Really long tail-momented taildraggers also have a severly restricted rotational ability, the
tail either stays on the ground or hits the ground before a useable pitch angle can develop.
A plane which is already close to the takeoff pitch angle at 200 feet with the maximum load can fly itself
off with only a minimal input from the pilot. A goodly amount of rotation adds drag right when it can't
be helpful.. :)
Several planes failed the "downwind turn" after takeoff.. this is a pilot error, failing to keep the nose down
when turning, due to the generally odd fuselage shapes, and the distance at which the plane is when
it's high enough to turn safely. The usual high-tailed shape is not a good image for judging the true
flight attitude at distance. As some of the most sucessful planes have the horizontal in line with the
wing, extreme positioning of the horizontal tail above the FRL seem unneeded..
If the turn after takeoff is performed properly, the plane will be spaced off the centerline the proper
amount when the turn to base leg is performed, with the turn to final also shallow. A steep turn here
will splatter the airplane.. QED...
Whatever makes the plane easiest to fly should part of the design consideration..
The Australian entry was impressive for several reasons.. I likes the odd configurations.. Everyone knows
a Hershey bar plane will fly.
Yawn!!!
This one had NO fuselage at all.. the smallest amount of wetted area
possible except for a true tailless, or saucer type. And it flew well. A semi-span loader, with the
payload needing no excrescence to fit inside the structure. And the prop was adequately protected.
On the frequent turnovers, due to the longish landing gear, the engine could be cut and prevent a prop
strike/replacement. Raising the thrust line a tad might permit a shorter gear.. As it performed with a
respectable payload despite the inefficiencies of a pusher prop, there's gold in them thar hills!!!
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