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Heartened
by the ease and speed with which our Tucanos were put
together, Mike Briggs and I set out to design a smaller
dual-purpose model for PSS or Speed 400 power, and settled on
the Fairey Barracuda as a different and, in some respects,
challenging subject. Eventually we decided that a scale of
1:17 gave a model of about the right size, working out at just
over 37” span with 200 sq.in. of wing area. Basing the
fuselage structure on that of the Tucano (though obviously a
different shape) and using a fully-sheeted built-up wing
produced a bare model weighing in at 8.6 oz, and which was
built and covered in a fortnight. Covering with Easycote and
Solartrim decals brought the weight up
to 9.7 oz, promisingly light.
There
are two reasons why I say it was challenging. The
Fairey-Youngman flaps are suspended ½” below the wing, and
extend rearwards by about 1”, and their effect on the
model’s flight is unknown. We have started by aligning them
at 0 degrees relative to the wing incidence, but are prepared
to adjust this angle if we can detect any adverse effect.
Initial test flights, as a glider, will be without them, so we
are no more confused than usual about the causes of any
problems we might find. The second reason is that the
Barracuda is a fairly bulky aircraft, with a high cruciform
tail configuration, and we were concerned about its weight
when powered by a Speed 400 motor, and possible tail-heaviness
in either case. Fortunately, no weight problems have surfaced,
but the issue of the flaps remains to be resolved when we get
an opportunity to undertake some intensive testing. As shown,
but balanced up as a glider and with the motor and propellor
removed, it weighs 17.3 oz, and we are hopeful that this might
be reduced a little after final CG location, although at that
weight it has a wing loading of only a little over 12 oz./sq.ft
and may be quite acceptable. With motor (geared), battery,
speed controller and propellor fitted, we estimate its weight
at about 25-26 oz, giving a wing loading of the order of 19
oz./sq.ft.
The
model is to fairly accurate scale in outline, deviations being
a slight (about 6%) extension of the span, shortening of the
canopy, the substitution of an all-moving tail (for simplicity
and lightness), an increase in span of the ailerons at the
cost of reducing the span of the flaps, and a flattening of
the fuselage bottom for ease of construction.
Fuselage
structure follows our current favourite approach, being
3/32” sheet sides over a framework of 2mm lightply outline
formers, a hardwood main longeron (in this case, ¼” x
1/16” basswood), and 1/8” sq. stringers in the corners,
with 3/16” sheet top and bottom. Soft block and sheet form
the nose contours and canopy. The tailplane is 3/16” sheet,
actuated by a bell-crank linkage with 18swg wire snake and
final pushrod, pivoted on a 16swg wire running in bearings
made from snake outer tube. The non-structural tailplane
struts are 20swg wire glued to the edges of ¼” strips of
1/32” ply, then wrapped in light glasscloth applied with
cyano. They hook into the ends of the tailplane pivot tube,
and so offer no resistance to its movement (but are marginally
behind true scale position). The wing is Clark Y section
(unusually for us), with the ribs dropped into a slotted
full-span spar, the whole being sheeted with 1/16” balsa.
Aileron operation is by 16swg torque rods from a central
servo.
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Steve
Griffiths' Fairey Barracuda
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The
colour scheme of navy blue throughout is the only one I have
ever seen of a Barracuda that lends itself to film covering,
and represents the Admiral’s barge used aboard HMS Vengeance
in 1948, according to the documentation I have. The balsa
canopy (hooray! no pilots to make!) is covered in pale grey
Profilm (left over from the Tucano) and framed with 3/32”
strips of Easycote ironed on, and the decals are all home
made.
The
aileron servo is a metal-geared Hitec HS-80, and the elevator
a Protech SD200, which happened to be what I had to hand.
Perhaps 20 grams could be saved by fitting lighter ones, and I
may do that if it proves necessary, and a few grams more could
be saved by using a lighter Rx, so I think the weight could
come down to about 16 oz. at a pinch. Now all we need is the
right wind and the right slope and we can find out whether it
works!
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