my SSC planes for the
2005 AMA Nationals,
posted July 3rd, 2005
design. I have watched Don Pruitt (RCCA Southeast District
Representative) fly his planes for going on three seasons with only minor
repairs. Anyone who knows Don and has watched him fly knows that he is
very agressive and his airplanes suffer a lot of impacts. Don's planes keep
on going with very little need to repair. So when I needed new planes
quickly for the 2005 AMA Nationals in Muncie, Indiana I was very glad that
Don Pruitt had some partially built airframes on hand that he could provide
to me.
The Georgia Gorilla started out inspired by, and owing a lot of design effort
to Lee Liddle and Roy Appleton's "SMACK II" design. This is an excellent
design that was eclipsed when Lee came out with his Cobra design which
Roy kitted. The SMACK is a very robust design, though not as sexy as the
Cobra, it will probably last a lot longer and is easier to set up to fly well.
Lee had used an airfoil sort of like a Clark Y. Roy made it a true Clark Y
and programmed his laser cutter to reproduce it. Roy also made the front
portion of the foam wing from EPP to absorb impacts and dissipate shock.
You can see Roy's work on his web site (click on kit sales).
The first SMACK used a wooden fuselage but Roy later adopted the
electric fence post material to the design.
Click here for an illustration of the Fi-Shock 200-260 fence post
Don Pruitt made some further changes. First he changed the wing airfoil to
a ClarkYH which he gets CNC cut in Roswell, Georgia by Mike Nemesh, you
can click here for Mike's web site Aerowings. The wing cores are beautifully
cut and feature the EPP leading edge with blue foam for the rear of the
wing. Another change that Don made was to use 1/8" glass rods for upper
and lower wing spars. The spar slots are cut into the wings as they are
CNC produced by Aerowings.
The next change Don made was to shorten the overall fuselage. He placed
the wing on the fencepost material and measured the minimum spacing
that would be required for a servo to fit between the trailing edge of the
wing and the stab. From this he created his fuselage. Don tells me that he
really likes the performance of the flying wing combat planes but hates the
way a wing strike destroys and entire airplane. His reasoning is that he
may lose a wing from time to time but seldom will he lose the entire plane. It
works, he has been flying the same fuselages for three years and has only
lost one entire wing in the process.
Some other ideas that Don incorporates came about from experience. For
instance his receiver is in the wing to protect it from damage. That means
the elevator and throttle servo connections and the battery can be ripped
apart if the wing shifts in a midair collision. So Don puts an extension on
each one so that it will pull loose without damaging the connector. He also
uses velcro between the wing and the fence post fuse to make it as strong
as possible but still able to shift in a hard impact. You can't argue with his
success.
So how does it fly? Very well. It flies light and the CG can be adjusted
easily by moving the wing on the fuselage. Mine came out slightly under
2-1/2 lbs but make weight by adding extra rubber bands to them.
Watch out for the Georgia Gorilla coming to a contest near you in the near
future.
lbs exactly. Spans 60
inches with 11-1/2" root
chord and 7-1/2" tip chord.
The wing has one inch of
leading edge sweep and
the CG is located 2.75"
back from the leading
edge.
flat lower surface of the
CLARK-YH airfoil and the
fence post fuselage. Look
at the very rear of the fuse
to see the holes for the
three screws that hold the
vertical stab in place.
(cutting board material) slid
inside the fuse and held in
place with sheet metal
screws. The needle valve is
held to the fuse with two
small tie wraps. Makes for
a simple, neat and strong
powerplant installation.
HS 81 on the top of the
fuselage then puts the
battery right behind it. I
cut into the fence post
and mounted a GWS Naro
servo in the side of the
fuse so I could move the
battery farther forward.
vertical stab are made
from 4mm coroplast. The
stab is held in place with
four sheet metal screws.
Three sheet metal screws
go through the bottom of
the fuse into the flues of
the rudder to hold it firmly
in place.
