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introduction
The BAC Strikemaster began life in the early
1950’s as the Percival Provost basic trainer for the RAF.
This was developed into the Jet Provost by adding an Armstrong
Sidley Viper 5 jet engine to the air frame. This led to a docile
aircraft with excellent flying characteristics that was adopted
as the basic trainer for the RAF in the mid to late 1950’s.
As development of the basic airframe continued with changes
to the aerodynamics and up rated engines an ability for close
support work was recognized and developed. This led to the MK
5 which had a new nose, housing advanced avionics, a pressure
cabin and hard-points under the wings. When Hunting aircraft
was taken over by BAC in the early 1960’s they developed
the MK5 into the BAC Strikemaster. This was a rugged aircraft
able to operate from rough airstrips and carry a variety of
loads up to 1360Kg (3000Lbs).
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Airspeed must be maintained
in the
Strikemaster, even the landings are hot. |
The Strikemaster was one of the most successful light
attack jets of its day and was still being produced into the 1970’s.
They are still flying with some Air forces today.
Construction
The model is a 1400mm wingspan, .40 to .46 low
wing sport scale model of built up construction. It is a straight
forward model that should present no problems to any modeller who
has built one or two planes from plans.
| I begin by building the tail
feathers, then the wings and finally the fuselage. This is just
my particular method of construction, you may choose to begin
any where else. I also do not start by cutting out all the parts.
I find it easier to cut the parts as I go. While this may appear
slower it makes it easier to make modifications if necessary as
I build. |
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The Tail-plane
The tail-plane is a simple built up structure
using 6.5mm strip. Cover the plan with plastic wrap and cut the
various strips to suit the plan. I find a balsa stripper invaluable
for this. If you don’t have one they are available from
your local hobby store. Ensure all the glue joins are square,
as you need a solid joint. I used poly-aliphatic glue for most
of the construction as it is cheap and easy to use. When the frame
is dry, cut 1.5mm sheet to size and glue to the frame. You may
need to weigh this down to stop the frame warping as the glue
dries. Ensure that before you glue the frame for the elevators
that you have cut the balsa to match the profile of the elevator.
When sheeted and dry, sand the required leading edge profile and
dry fit the hinges. You may wish to glue the hinges at this point.
I glued mine after the fin was attached to the airframe. |
Both the fin and tailplane are flat
surfaces builtup over the plane.
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The Wing
To begin the wing cut W1 and W3 from 3mm balsa,
W2 and W4 from 3mm ply the remaining ribs are cut from 1.5mm balsa.
The quickest way of cutting the ribs is to photocopy the rib profile
then with a hot iron transfer the outline to the wood. At this point
also cut the 3mm ply dihedral brace also included a brace for the
leading edge out to W4. Cover the plan with cling wrap and pin the
bottom spar over the plan. Place the trailing edge over the plan using
balsa packing to achieve the correct position of the spar as shown
on the plan. Glue ribs W4 to W10 in place ensuring that they are square
to both the spar and vertical. Glue in the top spar and the false
leading edge and leading edge. I cut the leading edge 4mm wider than
the rib to allow for the D section sheeting to butt against as well
as making it easier to sand the leading edge profile in place as necessary
Repeat this process for the remaining wing . Roughly shape the leading
edge to shape before joining the wing halves. Check both panels to
ensure that they have no warps. To join the halves together build
a simple jig that will hold the wing tips both square and at the correct
height for the dihedral using slow epoxy glue the dihedral brace in
position ensuring both halves are firmly joined and then clamp and
leave overnight.
Once the wing is joined fit the
remaining ribs in place and then fit the webs to the spars.
Ensure these are a good fit. Fit the landing gear block with
slow setting epoxy. Now fit the under side D section sheeting
to the leading edge and the under side center sheeting, the
tip and trailing edge sheeting. Set three degrees washout in
the wing panels before adding the top sheet. This will ensure
the twist will remain in place. Add all the capping strips.
Ensure that where the wing retaining bolts go through the wing
you place the solid balsa blocks to take the bolts. Shape the
leading edge to the correct profile fit the leading edge dowels
and servo tray. At this point I covered the center section with
some glass cloth and resin to add extra strength.
To produce the tip tanks cut the eight 9.5mm
profiles, hollow four of them and glue them together to create
two tanks. To get the required shape cut a hole in some card
to the correct diameter of each tank and using a balsa plane
and sand paper carve to shape. When the diameter is correct,
again shape the nose and tail of each tank to the required shape
then glue each tank to the wing tip ensuring that it is square
to the tip. |
Commencment of the wing assembly.
Wash out is essential on the wash out
and is built in with sheeting of the wing. |
The Fuselage
The fuselage is a standard box structure of
built up balsa with ply doublers. Begin by cutting out the sides from
3mm sheet and the formers and the doubler from 1.5 m ply. Pin the
side over the plan and cut and glue the 6.5mm longerons in place.
Next glue the doubler to the side and clamp or weight it down to ensure
the fuselage side does not warp, allow to dry over night. Build the
other side ensuring you have a left and right set. Mark the position
of the formers on both sides. this makes it easier to join the two
halves together. Glue formers F2, F3, F4 and F5 in place making sure
that they are square. Now join the second half to the formers, allowing
to dry over night. Place the fuselage over the plan and fix F9 in
place again ensuring the frame is square. Now fix F6, F7, and F8 in
place. F1 can now be fixed using slow cure epoxy, at this point fix
the gussets. I also fixed 6.5mm gussets to F 3 and F5. At this point
I fixed the fin and tailplane.
The fuselage is a fully sheeted box type
structure with rounded corners. |
The top sheeting can now be glued
in place, beveling the edges to fit. Fit the cockpit floor and
instrument panel. The rear bottom sheeting can be put in place
after fitting the desired push rods in place. I used nyrods. Carve
and sand the top and bottom to shape using balsa block to build
up the rear of the cockpit deck. Fit a floor for the fuel tank
then fix the front fuselage bottom in place. Build the nose cone
from soft 9.5mm balsa and carve and sand to shape. Build the intakes
as per the plan ensuring you carve the concave top surface, a
photo of the Strikemaster is helpful here. Before fixing the intakes,
fix the wing to the fuselage and set the correct incidence. When
you are happy with this glue the intakes in place. With the wing
still in place build the bottom surface to match the fuselage.
The last thing to add is the tail pipe. The plan shows a solid
block but I used 9.5mm sheet as this was handy and saves a little
weight. Sand the tail to shape. |
Finishing
The wing was sanded to a smooth finish and
covered with Sig Coverall. After shrinking and doping a coat of
oil based under coat was applied and sanded back then two coats
of oil based paint applied. I chose a grey, green camouflage paint
job.
The fuselage was sanded then any imperfections filled and sanded
again.
A coat of talcum powder (micro balloons are good also) in dope
applied and sanded. The paint was applied as per the wing.
The cockpit was painted and the canopy glued in place. I did not
fit a pilot which was a mistake as there is a large canopy to
show off the cockpit and it really does need a jet jockey in there.
I also chose not to use formers C1 and C2 but rather used trim
tape to simulate these formers
Fit the radio gear as shown on the plan. On my model this gave
the balance point at the main spar, which I found suitable for
flying. Paint the national markings of the plane you have modelled. |
Front view reveals a wide fuselage and
drag
producing dummy jet intakes which will slow
the model up quickly with power off. |
Flying
After setting the control throws for conservative
movement it was time to start the engine and go for that first flight.
I used a 7.5cc engine but this plane would fly on any good 6.5cc engine.
I placed the ‘plane at the end of the strip and gave it full
throttle. The Strikemaster tracked down the center of the strip and
after about 20 metres it lifted itself into the air and began to climb.
After a few circuits to trim the plane a few simple manoeuvres were
tried. Rolls are positive with little down elevator required. Loops
are gentle rather than tight but using high and low rates can make
the loops tighter if you wish. My model tends to drop the left wing
in a stall but this is gentle and easy to correct. Landings are a
little on the fast side but you must keep the air speed up until over
the threshold. Landing are then straight forward.
Conclusion
The Strikemaster is a simple model to build and just a little different
to the current crop of ARF planes at many fields. While not a super
fast aerobatic model (who’s going to be the first to put in
a hot .46 or even a .60 size donk?) the Strikemaster does all the
basic manoeuvres at a steady speed suitable for any pilot with some
low wing experience. With patience a more scale like model could be
produced or perhaps
scaled up with a ducted fan ?
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