This model provides challenges
for the builder due to its’ cylindrical and
tapering fuselage, swept back wings, nose cone
and elevated tailplane. There are several incidences
to consider. Building experience is preferable,
but the finished model is so pleasing to the eye
that you may like to give it a go purely as a model
builder. It is definitely not a model for learner
pilots.
Wing
You can start construction where you like, I started
on the wing.
As with any model built over the plan, use cling
wrap to protect it from glue. Use good quality
material and a flat building board.
Trace the wing ribs onto balsa sheet and trim to
accurate size, remembering there are two of each.
The template and router system is a bit of an overkill
for this model.
Pin the bottom main spar to the plan. Position
the ribs as per the plan and use the dihedral template
to get the correct angle for W1. Add the top spar,
leading and trailing edges, gussets and shear webbing.
Note the 2 degrees washout achieved by the larger
packing pieces on each rib as they move towards
the tip. Before sheeting this half, prepare and
install dihedral braces B1and B2. When glue has
set, cut out part of W1 to allow for servo mounting.
Sheet top of wing where required.
Remove from the plan and complete the bottom sheeting.
Be careful not to pull the washout out at this
stage.
Build the other half but don’t put the shear
webbing between W2 and W3. Sheet the top as above,
but only sheet the leading and trailing edges underneath
at this stage.
Test fit and join the two halves. Use 35mm blocks
under the tips to achieve the required dihedral.
Prepare and install the balsa block (trailing edge)
between W1s and W2s and the undercarriage mounts
UM. Don’t fit B3, the balsa block or the
wing locating dowels until later. The shear webbing
and remaining sheeting can now be installed, note
the sheeting at the tip as this is not common in
wing construction. Wing tips, aileron tips and
the rib caps complete the construction. Shape to
shown profiles and sand lightly.
Fuselage
The fuselage is built in two halves. The left (port)
or near side if you’re a horse rider is
built over the plan with the ink side up. You
will need to place the plan face down to build
the right (starboard) side, unless you want to
build two fuselages! To see the lines dampen
the back of the plan with paraffin oil, or kerosene,
or vegetable oil.
Formers with the exception of F9 are cut from 3mm
ply. The plan shows half formers, so tack two pieces
of ply together, overlay your template (I photo
copy the plan and rub turps on the back of the
paper which is face down to have a transfer effect).
You will now cut two symmetrical halves from the
one template. This method guarantees accuracy.
Note the bottom is cut off F6, but retain the off-cut.
F1 as you see is 2 off. One is cut in half (use
a fine blade saw) to use in fuselage construction
and the uncut one is glued on when the fuselage
is eventually joined.
Spruce longerons are pinned down; note the top
one only goes to the tail and the bottom one to
the wing cut out.
Place the fuselage crutch over the plan and accurately
mark the position of formers F2 to F5. Mark the
starboard crutch so that you have a mirror image
for later. Include the position of the wing mounting
brackets.
Slip formers over the crutch to marked positions
and place the assembly onto the longerons. F1A
is at right angles to the plan as the engine thrust
line is achieved by wedging the engine mount. When
satisfied all is square and plumb, glue together.
Don’t glue to the bottom longeron. This makes
joining the halves and installing F3 easier. The
middle longeron can be fitted and glued to each
former, back to F6.
When dry or set, pin the 6.5 x 3mm balsa spine
to the plan. Slide the dummy jet engine mount into
F7 and F8. Place this assembly onto F6. Pin and
glue to the spine over the plan. Now pull down
the protruding middle longeron taking care not
to lift the assembly from the plan. Use weights
to hold in position while the glue sets.
I sheeted from the top of the fuselage round, (grain
running lengthways), using 2, 100 x 3mm sheets
from F1 to F6. Leave an overhang at F1 to cover
the second F1 when it is installed. You may opt
to have a second balsa former at F6 to take a join.
If you’re a top balsa worker continue all
the way to F8, but my experience says plank from
F6 back. Sheeting covers the wing cut-out area
at this stage. By using only two sheets there is
now sufficient room for access to mount the nose
wheel hardware, fit F3A and clamp when joining
the fuselage halves.
Repeat the building process for the other half,
don’t forget to turn the plan over!
Joining the Halves
First thing to do is cut out the excess sheeting
in the wing seat area. By working from the inside
you can push pins through the sheeting to give
an outline of the fuselage crutch. Cut the sheeting
carefully and leave a good amount of access for
trimming when the wing seating is fitted.
A note here worth remembering is that the wing
is tapered and swept back. The profile of the wing
seat cut out shown on the plan is actually at W2
not W1 so the leading edge area of the seat will
need a fillet if you are too severe with the knife.
Don’t install the seat planking at this stage.
Test fit the fuselage halves and sand if necessary
for a neat fit. Glue and clamp. Use plenty of rubber
bands, clamps etc. Fit F1, F3A, nose wheel hardware,
engine mount blind nuts and fuel tank tray. Fit
the bottom longerons and complete the sheeting.
Fitting the Wing
One point five mm balsa is fitted between the
fuselage crutch and the skin. You may find it
easier to
sheet over the edge of the skin, either way works
well. The success of this operation will depend
entirely on the trimming job as just described.
When complete, fit B3, wing dowels and the under
belly block. The wing can be bolted in position.
Take care to measure from a common point at the
tail to the wing tips to ensure accurate positioning.
The Back End
The fin is very easy to build over the plan. However
accuracy is required when the balsa frame above
and below the tailplane slot is installed (this
is not the triangle support), note the 1.50 negative
incidence. Sheet this side of the fin, remove
from the plan and cut the tail plane slot gaining
access from the unsheeted side. Cut the nyrod
exit point. Sheet the other side, include the
other nyrod slot and cut out for the tailplane.
The sheeting goes into the fuselage so don’t
skimp.
The tailplane is built as per the plan. Use the
ply dihedral braces, ensureing each tip is 11mm
above the building board when joining and that
there isn’t a twist in the tailplane when
it is glued together. Fit the tailplane into the
fin and glue in place, be sure the angles in relation
to the fin are equal.
Mounting the Completed Tailplane
The unit can now be mounted to the fuselage, again
fitting and trimming. This may take time but the
incidence needs to be correct. Use plenty of glue
(I use a good epoxy) as access to the fuselage
spine is only through the top slot. Rudder, elevator
and bracing fillets can now be completed.
Dummy Jet Engines
Find a cardboard tube of appropriate diameter and
glue on formers E 1s (there are 2 per set), 2
and 3. Plank with 3mm strips. This is a challenge
as the circumference of E2 and 3 is bigger than
E1. Three mm balsa will stand a fair bit of sanding.
You may cover the pods and install later or install
and cover.
Building the Nose Cone
This is a labour of love but the results are pleasing.
I laminated scrap together with a rough hollow
inside. I then shaped outside to the required
profile and hollowed out the inside with a modeller’s
grinder. The worst part is that after all the
work you need to cut large holes in it to fit
the motor. Again please yourself whether you
glue it on or use mounting blocks and screws.
Bring it all Together
Fit out the Mystere with control surfaces and hardware.
Be conscious of weight and positioning of gear
as the model will easily become nose heavy. Remember
the full size Mystere has two engines that are
mounted behind the C of G and we only have cardboard
and balsa!
Speaking of C of G
The plan I built off, being a review plan had no
centre of gravity marked so it had to be calculated.
Fellow club member Andrew Barber loaned me a
great book called “Scale Aircraft Models
for Every Day Flying” by Gordon Whitehead.
It was originally published in England by RM
Books. It explains in layperson terms how to
calculate the point. It was an interesting exercise,
taking into account wing areas, root and tip
cord lengths of wing and tail and the tail moment.
All calculated, the position was determined as
now shown on the plan. To gain a good balance
the hardware was mounted aft as describe earlier.
A good quality covering material and some pinstripe
set this model off with a touch of class.
Flying
Sunday afternoon at the Hamilton club. Many of
the members were aware of the construction project
as Wednesday evenings is usually building night
at my workshop where we gather to do a little
building and talk a lot. So there were plenty
present to witness the maiden flight.
The usual checks were done, radio range check,
correct control surface movement, and most important
of all, engine reliability test. The Mystere is
powered by an Enya SS 40. Control surface movement
was a hot topic of debate, but being an untried
model it was decided to use a good amount of travel
because you obviously can’t increase it in
flight. However my radio has dual rates and I therefore
had a good range of control.
Roll out to the runway, final wiggle of the sticks,
a deep breath, and power up. The Mystere lifted
off after a long build up of speed and climbed
away with minimal trim required. The long run was
a precautionary measure as there were no known
flight characteristics to go by. Just a couple
of up trim clicks were needed. Control surface
throws used are, elevator 16mm total, aileron 16mm
total, rudder 30 mm total, but governed by the
position of the elevators.
Fly it like a passenger plane. It is a fast flying
plane, great for circuits and low passes, the odd
loop is okay but I don’t think the passengers
like them much!
Height was gained and a stall was tried, more
screams from the passengers! It drops a wing at
low speed, but power up and fly away no problems.
After several minutes in the air there is no choice
but to land. On my first attempt I overshot the
strip not allowing for the high approach speed.
Throttle on, climb away and try again. Next approach
was longer and flatter, trying not to wash off
too much speed. Yahoo, a successful landing. This
is a sleek machine which has an approach speed
higher than that of a 40-size sports model.
This project has been well worthwhile. I’ve
learnt a lot, enjoyed the challenges and love the
look of a great model. The old man reckons he wants
to hang it in his office when I’ve finished
with it! He’ll be waiting a while.
