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I have been almost obsessed with Power
Scale Soaring for the past four years or so and to a great
extent, to the exclusion of all other aspects of slope
soaring.
Recent projects have been gradually
getting bigger and the foam/veneer construction technique has
been introduced in almost every airframe due especially to the
unquestionable success of this method of construction proven
by my Russian spy plane, the 'Bison'. This aircraft has
clocked up more flying hours than all my slope soarers put
together, and has survived knocks and bruises which would have
curtailed the life of most balsa airframes.
I guess the B-52 was a natural step in
the evolution of foam/veneer construction and in my quest for
the ultimate PSS machine. The B-52 is a 'dead ringer'
for PSS, having a very stable aerodynamic airframe and of
course a colossal wing area. As with the 'Bison' the
B-52 fuselage can be cut from polystyrene foam in four simple
components and with the addition of the nose block and the
tail cone a very quick and strong fuselage can be created.
Having flown large scale gliders for many
years (3.75 - 5.00 m span) I've learned that the bigger you
dared to build, the greater are the rewards in the aircrafts
flight characteristics; smooth, efficient and forgiving are
the usual traits. Having often contemplated 'over the
top' (OTT) scale for PSS I decided the B-52 was the most
likely and potentially successful contender yet. 'OTT'
scale has been tried and tested successfully in all other
aspects of R/C model aircraft, so why not take "a giant
step for PSS and boldly go where no man has gone before!"
So, 3 rolls of decorators lining paper
later I had designed all the details and drawn plan and side
views of a 4.2m 1/16th scale B-52 with a wing area of 20
square feet.
The B-52 fuselage shape is so simple I
only had to produce two different formers. Thanks to Len
Whalley again for kindly printing out the wing, tailplane and
fin profiles on his computer.
Pat Teakle of 'West Mendip Sailplanes'
was commissioned to cut the mammoth wings etc, the tailplane
area and planform for example is practically the same as the
wing on an LMC (Leicester Model Centre) 'Mirage 2000'!
Each wing panel had three 1/2 x 1/4" ramin
spars and two lengths of straws to pull the servo leads
through. Anyone know where you can buy continuous lengths
of straws? Pat I'm sure, is fed up of threading straws
onto one another! The panels were superb, as is all
Pat's foam/veneer work, but he had to admit that they were
"the biggest pair he had ever handled" - (Mrs.
Teakle - don't worry!) The length of the leading edge on
each panel is very nearly 8 foot - the root is 26"
David Suckling of Sutton Aviation was
persuaded to produce the fuselage parts. The main
section was cut from blue foam for added strength while the
rear section where weight was more critical, was made from
normal white foam (medium density.) 1" walls were
cut which were then veneered both inside and out. There is
still ample structural integrity but plenty of room
inside. The fuselage when glued together looks like (in
section and size) a loaf of "Mothers Pride"
bread. It is 10' 2" long and it's a one piece
fuselage!
It took me altogether 12 months to build
the B-52. I had to take a number of 2 months rest from
the project as the problems resulting from it's sheer size in
a workshop accustomed to "sensible scale aircraft"
caused me almost insurmountable frustration!
After a lot of nagging from flying
friends, I finally found the impetus to finish the
airframe. Covering the monster required 20m of
'Solarfilm' and the project was draining my bank balance and
patience. To my delight, Derek Hardman of 'Solarfilm'
came to my rescue and agreed to donate the silver coloured
film rather than see the effort dwindle to total despondency.
My sincere gratitude goes out to Solarfilm who provided the
encouragement at just the right time to finally complete the
challenge - single handed. It still took a month of
solid work to cover and decorate - never again!
The B-52 sports a striking day-glow
orange and silver colourscheme, a variant which was used for
carrying aloft the X-15 test space plane for launch from
42,000 feet. The X-15 was a rocket powered test vehicle
which achieved an amazing speed of 4,520mph - Mach 6.7 - as
well as accumulating valuable data for future manned space
exploration. I have already produced the basic foam
components for the X-15 and I also intend to emulate the full
size launch technique, which should be good for a laugh.
Even with a stretched wing and lifting
body fuselage I do not expect the X-15 will be capable of more
than a couple of fast passes, circuit and landing and that's
from 1000 ft launch! Could be interesting though with a
couple of solid fuel rocket motors in the tail as recently
imported from the USA by 'Link Model Supplies'. Anyway I
had better see how the B-52 flies first - Test Pilot in
shaking trepidation!
Whenever I'm ready for a maiden flight, I
can guarantee the wind will turn to an awkward direction or
will disappear. The B-52 was no exception, after a month
of South Easterlies the wind conceded to a North Easterly,
still not the North Westerly I'd been patiently waiting for,
but it would do.
At the crack of dawn on a clear Saturday
morning, Steve Belshaw and I sneaked up to the slope before
our club members arrived. Two other specially invited
helpers were due to meet us up there to help launch, video
and photograph.
Having carried out the list of pre-flight
checks I didn't have any more excuses not to fly, except that
our two compatriots hadn't rolled up. Steve decided that
he was up to a one man launch, he being the impatient type, so
I thought, if he insists on giving himself a hernia, fine.
The windspeed was only 10-15mph but
smooth and steady so Steve did not have much trouble
positioning up into wind on his own. He had one hand
steadying a leading edge of the wing, and the full weight of
the beast - 23lbs - sitting in his other hand - I was glad to be
on the 'tranny' end! So, here goes - fly or splat!
Before Steve had taken 3 strides the B-52
left his hands and flew up and out as if on rails to our
dumbfounded amazement. Perfectly in trim, the monster
steamed up like a train, penetrating well into the lift - what
a magnificent sight to behold.
All the flying surfaces responded with a
positive, crisp feel and she felt as comfortable to fly as a
1/4 scale glider. Very smooth in the air and
convincingly realistic. The amount of sky consumed by
its sheer volume and by its scything passes along the slope
were simply stunning.
The B-52 only required aileron and
elevator to guide her around the sky. This is just as
well because the rudder had very little effect! I
confess that I tended to pull angles of bank far beyond what
the full size would even dream of. This looks quite
alarming for a B-52 as the model is such a convincing
replica. The enormous flaps are tremendously efficient -
10-20º creates instant height gain without any noticeable
pitch change. I used full flap a few times to dive down
from cruising height of 3-400 feet, an altitude the B-52
seemed to attain through non of my doing. The efficiency
and stability of the B-52 is simply astounding and far
exceeded my wildest expectations.
I didn't plan on executing any foolish
maneouvres on the maiden flight. The satisfaction of
simply soaring was reward enough and made all the effort
worthwhile.
The flight however was not without
incident. After 20 minutes of flying beyond the cameras
reach (we don't have expensive zoom lenses unfortunately) I
decided to do some low, low passes and get a few full frame
shots. Having dived from 300 feet against the flaps down
to 30 feet the elevators started to flutter. The
violence was such that it sheared a threaded rod (as I
discovered on the post mortem) and although I recovered from
this alarming situation there was no elevator control, it
having failed during recovery. The B-52 then pitched
down at about 45º and hit the deck. Under normal
circumstances it would have survived as the gradient of the
hill was 35º and covered with heather, I even levelled the
wings.
I was very unlucky, the only obstacle on
the slope for 400 yards was a fence beside a cluster of rocks,
and it had to get them both. The damage was
extensive. The flight had been so exhilarating that I
set about repairing the B-52 straight away.
Fortunately the foam/veneer airframes are
a fairly quick and easy material to repair. I simply cut
away the distorted mess to leave big but clean cut gaps.
I made appropriate formers and produced the odd shaped foam
components, veneered them with 1/8th balsa and glued them into
the gaping voids. With the addition of a mixture of
1/8th and 1/4" ply fillets let into cross brace weakened
structural areas the B-52 went back together again - not
forgetting 1/4 of a tonne of fast setting PVA glue!
The model has since been successfully
flown on numerous occasions, both off the slope, and, with the
incorporation of nose release gear, in aero tow events.
Boeing
B-52 SPECIFICATION
Wingspan
: 153"
(3.88m)
Wing Chord : 26"
(660mm)
Wing Area : approx
20 ft2
Fuselage Length : 10'
2"
AUW : 23
lbs
Wing Loading : 18.4
oz / ft2
Wing Section : Eppler
205
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The B-52 was flown
using FUTABA Challenger 5 R/C gear, with a plug
on failsafe between servos and receiver. Circuit
design from back issue of 'RCM&E' magazine.
Failsafe is a condition of
compliance stipulated on the CAA exemption certificate.
Model fitted with a huge 2.4 Amp
Rx battery pack installed in the nose (Takes a
week to charge on a normal charger!!)
Engine nacelles formed from ABS
and are 'knockofffable" - see diagram. Cut
out intake and jet nozzle to allow airflow right through
- no noise so presume little drag.
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Diagram
showing detail of Simon's ABS 'knockoffable' nacelle design
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