Have a large enough flat building
board that has a surface that can accommodate pins
for holding
the fuselage and wings etcetera, well, only a delta
wing in this case. Craftwood, MDF or similar are
good or even either of these then covered with
compressed cork floor tiles will give a good flat
surface and allow the holding pins to do their
job.
Also necessary is a means of accurately transferring
lines from the plan to materials such as tracing
paper or better still, a photo copier. If you
do get the plan photo copied you can then cut out
the various components and lay them face down
onto
the required piece of either balsa or ply, then
by applying heat with a household iron, the reversed
image will be transferred to the wood. It is
now only a matter of accurately cutting out the required
shape.
Good quality material and adhesives go
without saying. This aircraft can be built with
basic tools and clamps so no costly machinery is
necessary.
Study the plan thoroughly before commencing
construction so that you have a full understanding
of the
way you are going to build the "Stop & Give
Way".
Using this review as a building guide
and you are sure to have a fun machine.
Although this plane is not your conventional
wing, fuselage and tail assembly job, the
principles of construction are the same.
Keep weight to
a
minimum without compromising strength, (some
builders weigh materials in their quest for
lightness) and
ensure twists and warps are not built in.
In this model the potential for twists is
significant
as
the shape of the wing can lend itself to
the problem if you are not careful.
Getting Started
Start by cutting out the wing ribs. Transfer the
outline to balsa sheet. I used yet another method
of transferring the rib shape to the balsa. Using
the wing rib photocopy, I rubbed a rag soaked with
turpentine on the back of the copy to transfer
the ink to the wood. Smelly but works just as well
as the cloths iron method. There are only 5 ribs
per half so balsa waste can be kept to a minimum
by careful positioning of the transfer. You may
prefer to photocopy from the plan, cut out the
shape and use it as a template. Remember to place
two sheets of balsa on top of each other when cutting
pairs of ribs so that ribs are identical. Mark
a centre line length ways through the ribs so that
the leading and trailing edges can be kept straight
when they are fixed to the ribs. Position each
rib over the plan and bevel the leading edge to
match the angle of the leading edge spar so that
a larger surface area is available to glue to when
the time comes.
Construction of the "Stop Give Way" plane
is different in that the fuselage is constructed
inside the wing. Each half of the wing is built
separately over the plan. Protect the plan with
cling wrap film or similar. Make sure that the
centre line of the ribs at the front and back are
straight to prevent built in warps. The centre
ribs, which form part of the fuselage, are placed
with an outward (top towards the tip) slant as
determined by the dihedral angle. When the halves
are joined these centre ribs sit vertically to
attach to the fuselage sides.
Cut four spars per
half as per the plan, the top two will be trimmed
to accurate length when the
halves are joined. Note the front two are spruce,
not balsa.
The leading edges can be cut to length.
Mark a centre line full length on what will be
the inside
of this piece. It should be tapered now, but
leave oversize to allow for sanding after the
leading
edge sheeting is installed. Glue the leading
edge in place ensuring that the centerline
of both the
leading edge and ribs match. Also prepare and
fix the balsa elevon spar in a similar manner.
When
both halves are built to the above stage, prepare
the ply dihedral brace as per the plan
and trial fit to both halves. When satisfied
with the dihedral brace fit, put it aside.
The leading
and trailing edge top sheeting can be trimmed
and fixed in place; this gives the wing some
rigidity
for the following steps. Again remember the
potential twist problem. We install the trailing
edge lower
sheet when the centre sheeting is fitted.
The top trailing edge sheet does not meet in the
centre,
as it has to accommodate former F5 passing
through to the bottom of the fuselage.
The
wing halves can now be joined. This is where trimming
of top spars will be required
to accommodate
the dihedral, they are all butt joined.
Remember the dihedral brace and consequent dihedral
angle. Dihedral is built in by placing
a
30mm block
under each wing tip. The other important
guide is that
the centre ribs should now be vertical.
Butt join the spar inner ends and glue, adding
any required
fillets for strength. The trailing edge
join is strengthened by former F5.
The wing can now
be turned over and the dihedral brace in glued
place. The spar
will hold
the dihedral angle but be gentle. It
is a good
idea to check
that nothing has moved by re-blocking
the wing tips while the glue sets. The trailing
edge
and centre sheeting is ready to be installed.
Start
at the trailing edge and work forward
to within about 30mm of the leading edge sheet.
The gap
left will make clamping of the fuselage
and doublers easier when they are fitted.
Now
sheet the top
centre from the trailing edge forward
to where the rear spar comes through the centre
ribs.
The
reason being the fuselage sides sit in
top of this sheeting from this point
aft.
I installed the 9.5mm block which supports
the fin at this stage for added strength
and in preparation
for mounting the fuselage.
Fuselage. What Fuselage?
As stated before the fuselage is built inside the
wing ribs. Prepare the balsa strip (6.5 x 3 mm),
which covers the wing centre-sheeting join, it
needs to be in two pieces as it crosses the rear
spar. Also prepare formers F4 and F5. Fix the
balsa strip over the bottom centre-sheeting join
(inside) and glue F4 & F5 in place. Fit the
second piece of balsa strip, taking care to have
it centred.
Fuselage sides can now be trimmed
and fitted. Note they are in two halves. When
satisfied glue and
clamp / pin the rear halves FS2 in place. F3 can
be glued in place as it will assist in holding
the fuselage sides. A variety of clamps purchased
from the local $2 shop are an invaluable building
tool. The front halves FS1 are installed, note
the fuselage sides stop at the firewall position.
Next step is to fit and fix the ply fuselage doublers
FD. Again take care with length and clamp well
while glue goes off. At this stage the second formers
F1, 2 and 3 and undercarriage block are built in,
study the plan to fully understand what is required.
The
bottom balsa sheeting can now be completed and
top fuselage longerons fitted and fixed. Prepare
ply sheeting UF which is used forward of the
undercarriage block. Epoxy is the preferred adhesive
as this
is potentially a high stress area.
Shape the leading
edges. I have recently purchased some of the ÒPerma-GritÓ range
of tungsten carbide sanding, cutting and grinding
tools and this is where the leading edge sanding
tool came into its own. Being pre-shaped (concave),
the job of getting a good uniform leading edge
was made easy with this accessory. When first
looked
at this would seem a difficult task especially
at the inner end as the edge is so wide and
there is only 12.5 mm to work with. However, with
a
little patience a quite satisfying shape can be
achieved. Now fit the wing rib caps.
T4s are fitted
either side of the slot in F5.
These pieces help support the fin. Sheet
the fuselage
top from F2 to F3, there is a hatch from
F1 to F2 for fuel tank access, from F3 to the
front
edge of where T1 will be placed, there is
another hatch.
From the front edge of T1 over F5 and down
over T4s sheeting is fixed. A slot will need
to be
cut to fit the fin.
Building the elevons and
tail is quite easy. Follow the requirements of
the plan. This
is where a flat
surface is again important. When complete,
hinge slots can be inserted in preparation
for covering
and installation.
After sanding, cover the
plane with a good quality product and make sure
edges are
well sealed around
the engine area. The red trim is iron
on covering over the top of the white base.
For those not
used to this process a cool iron is needed
and work
from one edge towards the other or from
the middle out each way to avoid bubbles.
If
too much heat
is used the shrinking will cause uneven
lines along the edge. Fit the fin in
the slot,
removing the
covering where glue is to be applied.
Glue in elevons and the rudder.
Mount the motor with
2 degrees of right thrust. This is achieved with
a small
wedge behind
the engine mount. Install servo trays
and fit out
with servos. Note the receiver and
battery pack are
mounted in the rear of the fuselage.
Now install the undercarriage and tail
wheel.
You may prefer
a steerable (with the rudder) setup
as this will make the model easier to steer
on the
ground.
Centre of Gravity
Being an untried plan, the centre of gravity was
not included, consequently it needed to be calculated.
Using the formula from the book mentioned in
an earlier edition of Airbourne where the Dassault
Falcon was reviewed a theoretical point was established.
As described later, this in fact was very close
to the final point. Flying a prototype model
the first time can be a bit nerve wracking. Is
the airfoil OK? Is the motor matched OK? Are
the control surfaces large enough? Do they throw
far enough or too far? And most importantly is
the centre of Gravity (C of G) somewhere near
the all so vital balancing point? The last thing
you need is a tail-heavy model!
Lets Fly...First Flight
The Hamilton area turned on a perfect day and there
were ten or so members present to witness the
maiden flight. Fueled up, radio range check completed,
do the elevons work the correct way? Likewise
the throttle and rudder. All had obviously been
checked during building, but it still pays to
check especially with multi model capable radios.
For
this flight I fueled to the max, tested the throws
yet and taxied out to the runway. The elevon
throw was maximum at about 30mm each way.
Lift off
was after a run of about 20 metres; basically it
became airborne by itself. Move the elevon stick
and Òtwitch twitchÓ, too much throw
for a test flight and nose heavy into the bargain.
When I let the elevator go, down would go the nose.
Rolls were savage with such a high rate and the
rudder had plenty of authority in that you could
roll nearly as well with it as with the elevons!
When on final approach to land almost all the elevon
up was needed for the slow approach because it
was nose heavy.
To achieve the balance during building
and to meet the previously calculated C of G,
the battery and
receiver were mounted between the throttle and
rudder servos. I now moved them to the rear of
the fuselage to counteract the nose heavy attitude.
Elevon throws were reduced to about 20mm each
way and the rudder to around 30mm with expotential
control.
Second Test Flight
The second flight was great, a shorter takeoff,
more easily controlled flight characteristics
and no dropping of the nose and still a good
roll rate. Testing the slow flight speeds was
impressive with no vices displayed. Slow passes
were done for photos and a good range of aerobatics
were tried, even a rough hover a fair way above
the ground. With rudder and elevon input, diving
spins were very fast, loops and rolls are easy
and no stall traits are displayed.
On returning home the C of G was checked on the
jig and found to have moved about 10mm from the
point calculated.
In Summary
This is an easy model to build with no hidden obstacles.
It would be easily constructed by a novice builder.
It is certainly not a beginners model to fly,
but anybody with solo experience would be able
to manage OK, however a test flight by an experienced
pilot would be advisable.
