Page 29 - MFW March 2024

Building & Flying
Building & Flying
Building & Flying
ed P
ed P
atr
atr
T T
olia’s
olia’s
Ted Patrolia’s
COBRA
COBRA
COBRA
Maurice Job
I saw this design on a FB page that I
follow and decided that it deserved an
attempt because of the building
challenge and because it is so
‘different.’ The plan is a free download
from Outerzone and arrived as a file
that I had printed locally. The challenge
would be in the fuselage, keeping it
straight, but the build while unique, is not especially
difficult. The plan is for a free-flight model, but comes with
a second sheet showing conversion of the stab to radio.

The history of the design, is given in the attached image,
but when I commented on FB that I proposed building it,
one group member said ”I’ve seen it fly” and when pushed
said it flew ok, not a world beater but certainly unique in
the air. Until it hit a parked car; aah freeflight! What
inspired Petrolia to design this Dan didn’t know but though
he didn’t know him well, he seems to hold Petrolia in some
regard. Was he trying to achieve some aerodynamic
feature or function or was just a ‘look’? I don’t know. The
plan is based on a sketch drawing by Petrolia after the
second model was built in the late 1990s, given to a
draughtsman to produce a plan. My initial review of the
plan showed some anomalies between the different views
as drawn, eg the ribs did not match the plan view the spar
locations were off, and fuselage sections had to be
tweaked to fit the profile view. This has led to some
skepticism on my part as to critical data such as
incidences and CoG given on it; was this data provided by
Petrolia or the draughtsman’s assumptions?

Specifications:
Wingspan 81inch (it’s an American plan)
Wing chord 13 inch
Wing area 1200 sq inch
Stab span 34 inch
Stab chord 11inch
Length 56inch
Weight 2Kg (4.4lb) incl battery
Power 1500KV motor, 3 cells
RC functions V-Tail rudder/elevator mix
Throttle with isolator

Building
First, and to prove the point as to whether I could achieve
it, I did the fuselage. There are no structural drawings on
the plan other than for the u/c leg, just shapes. The first
picture shows the first side on the table before planking
with 1/8 square. That planking took hours, one or two at a
time. Assuming the plan is correct, it is pretty much

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