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Stewart
has already had plans of his Supermarine Spiteful and a
Supermarine Attacker PSS models published in R/C model
magazines - see the plans guide on this site. His latest
model, now successfully flown is the Avro 707A delta, one of 3
similar sized test models in the Avro Vulcan development
program. Stewart explains his thoughts on the design of
this fine model.
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A
study of Stewarts' delta model - finished in
an overall gloss red scheme as per the full size. |
For
quite a while I have had the desire to build a delta.
Having worked on Vulcans off and on over an 18 year period I
first considered it as a subject to model. In the end I
decided on its'
baby
brother - the 707A. It is a nice bright red, and is
still scale when flown aerobatic. I based my model on
WD280, which is the aircraft that finished up in a back garden
in Australia for many years. I now believe it is to be
installed in a museum out there. This aircraft finished
up with modified outer leading edges rather like the Vulcan
Mk2. It was originally painted salmon pink but was later
repainted bright red to compliment the blue 707B and the white
707C formation flight.
I
based the outline of the model on the 1/72 scale drawing in
"Aeromodeller"
from
October 1952. It is built in my usual method of all wood
structure, planked fuselage, built up sheet covered
wings. The wings and fuselage are covered in light
weight glass cloth and epoxy resin. The centre section
of the wing is integral with the fuselage. The fuselage
being constructed in the old method of top and bottom keels
and the frames split vertically down the centre line.
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The
span is 34", overall length, less the pitot probe
which is removed for
flying,
38", all up weight, 2 lbs. This is the
lightest PSS model I have built so far. The
aerofoil section is Eppler E180. |
The
flying performance was very disappointing at first.
Instead of following my gut feeling of where the C of G should
be I used a formula given by a gentleman who writes in a modeling
magazine and flies powered deltas and was not where I thought
it should be. It was too far aft and the model was
decidedly divergent in
pitch. Launch it upwards and up it would go and
over. Launch it downwards and it would go into the
ground. I loaded up the nose with lead and at Pendle
Hill last October, in the rain, it flew stable at last, but
with full up in and plenty of sink.
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Another
view of the Avro 707A showing the true delta planform. |
Back
at Moel Famau in North Wales, on a dry day I gradually moved
the C of G back a bit at a time until I obtained satisfactory
flight. I was not surprised with the eventual C of G
position! The model is now a joy to fly. Nice
smooth loops, although you have to go easy on the elevator
input or it will drag to a standstill. This phenomena of
the delta is handy for landing. In a good breeze just
hold the nose up high and down the model comes for a vertical
landing. Rolls can be quite fast but a bit barelly
(although this may be due to my input.)
The
down side of the model is that it is a devil of a job to
launch it. It is like a wet bar of soap. You need
a helper to launch it. I must try to allow for finger
holes to aid self launching on future models.
Stewart
Redfern.
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