When I’m about to build a model that has
its origin in a full size aircraft, I try to find
out as much as possible about the aircraft, so
I went to the net and found that there are a number
of sites by simply typing in the search box ‘Pilatus
Porter’. I was mainly looking for specifications
of the Turbo Porter and found that a number of
sites also had colour photos of most of the Pilatus
Porters made along with their history.
I printed off the general information about the
specs and then had a look at the photos to choose
a colour scheme for my model, (all of this before
I started building). The colour scheme chosen was
used because I believe that a profile model needs
some pattern to take away the thinness of the fuselage.
The particular Pilatus Porter chosen was built
in 1971 and had been used as a survey/photo plane
and for parachuting until destroyed by fire in
an act of vandalism in 2003.
Now to the Model
It should go without mention that when you receive
a plan you shouldn’t start building until
you’ve studied the plan thoroughly and worked
out your own plan of attack.
After studying the plan carefully I decided to
start by building the hardest part first - the
wing. I also decided that because of the 1.4 metre
wing span of this model and the fact that I only
have a sedan, I would make it with a detachable
wing, which created its own set of problems to
resolve and these will be seen as we build the
model.
The Wing
This wing has a constant chord with no dihedral
and as such is quite easy to build straight and
true.
First, cut out enough ribs from 1.5mm and 3mm balsa.
They can either be cut out individually or as I
did, they can be cut out using the sandwich method.
The sandwich method is very simple for this wing
because it is constant chord. I cut out two 3mm
balsa ribs very accurately and used these as my
templates. Between these templates I placed 12
pieces of 1.5mm balsa and 2 pieces of 3mm balsa.
Some people use pins or bolts to hold these together
for shaping. Then I used the balsa plane to bring
the inserts to just larger than the templates and
then sanded them until they were the correct profile.
Then I cut out the spar slots (top and bottom)
and the ribs were almost ready to start building.
As indicated on the plan, the ribs have holes in
them to lighten the overall wing, now is the time
to cut these holes. I used a compass cutter that
I bought from a discount shop for about $3.00.
These are also available from craft shops, or stationery
supplies places for around the $7.00 mark - maybe
slightly better quality. The 4 x 1.5mm ribs to
become W3’s and the 4 x 3mm ribs to become
W1’s were removed and put together into their
own little sandwich so that the slots could be
cut for servo tray supports as these ribs are to
be used for either side of the aileron servo areas
in the outer section of the wings and for the other
two servo bays in the centre of the wing. The only
other job now is to cut the W1 ribs in half as
shown on the plan and to cut out two W4 half ribs
from 12.5mm balsa.
Now Let’s Start
Building
You do have a flat building board don’t you?
Because I am transferred regularly with my vocation,
I check my board with a straight edge each time
I use it.
Lay the plan on the board and cover it with plastic
food wrap (or your favourite medium) to protect
it from the glue. I then laid down the bottom spar
and pinned it to the board, ensuring that it was
straight. As this wing does not have any dihedral
I decided to build the wing in one piece. I believe
this gives a stronger wing. This can be achieved
using 120cm lengths of spruce by splicing the extra
needed, ensuring that the splice is on a rib and
lace the spliced end of the top spar at the opposite
end of the wing. Then I placed a length of 12.5mm
balsa along the line where the trailing edge sheeting
is marked on the plan. This lifts the trailing
edge of the ribs and helps in building a true wing.
Then test fit the ribs in place as indicated on
the plan and when satisfied that all is well use
a set square or something similar and pin and glue
the ribs in place. When this has been done you
are able to fit the top spar and glue in place.
Next cut some 6.5mm hard balsa wide enough to suit
and glue in place for the aileron spar. Before
gluing the leading edge in place it will be necessary
to fit the W4 half ribs against the appropriate
rib in each side of the wing. Also, have you decided
to make the wing detachable as I did? If you have
you need to decide here what sort of strut attaching
you will be using. I set a nylon control horn into
each of the W4 half ribs before fitting them into
the wing. Once W4 ribs are in place glue the insert
and glue in place the 1.5mm ply ‘wing joiner’ -
even though building the wing in one piece it still
gives extra strength for the wing. If you are making
the wing detachable it is also necessary place
some block balsa between the centre ribs to secure
the dowel for locating the wing in the fuselage
and another piece of block balsa where the wing
bolt hole is to be drilled. As with most wings,
this one has sheer webbing between the top and
bottom spars and sheeting from the leading edge
to the rear of the spar top and bottom to ‘D’ box
the wing for strength. Next, the trailing edge
sheeting and the cap strips are added. In the servo
bays, triangle gussets made from 3mm ply were glued
into each corner, ensuring they are set low enough
that the servo bay covers are flush with the surface
of the wing. Then servo bay covers are made from
1.5mm ply. I chose to install the aileron servos
on their side so that only the servo arm extended
out of the servo cover (making for a neater finish).
I also marked these covers because I have found
that no matter how carefully I make these compartments
they are always slightly different and one will
not fit in another.
Now the ailerons and the rear centre section between
the ailerons, which are open framework, are made
over the plan from 9.5mm balsa and sanded to the
desired profile. The ailerons and the aileron spar
are slotted to accept the hinges, but the hinges
are not installed at this stage. Once all has been
shaped it is a simple job to transfer the outline
of the total wing onto 12.5mm balsa to shape the
wing tips. Sand the entire wing and the wing is
ready for covering, but do not cover at this time.
Tail Feathers
The horizontal stabiliser and the fin are built
up over the plan from 9.5mm balsa in a similar
fashion to that used for the ailerons because
these too are open framework. The rudder and
elevators are made from solid 9.5mm balsa sanded
to shape and then aerodynamic counter balance
pieces added on the top of the rudder and outer
edges of the elevators. It is necessary to make
an elevator joiner from 2.5mm piano wire. Again
I slotted the fin, horizontal stabiliser, rudder
and elevators to accept the hinges, but again
do not attach at this time. Sand the fin and
horizontal stab leading edges to the profile
shown on the plan.
Fuselage
I have left this until last because the wing and
tail feathers are fitted to the fuselage and
I use the outline of made parts to draw the lines
for the cut outs to insert these.
The fuselage is basically made of four pieces of
12.5mm balsa with some substructure and then sheeted
with 1.5mm balsa.
First it is necessary to mark out the four different
pieces of 12.5mm balsa and then to cut them out
accurately allowing for the engine bearer spacing
to suit the engine you are going to use. I cheated
here because I cut it out as per plan, leaving
the bearers as part of the balsa and then cut out
where the bearers would fit the old OS 40 FP that
I had not used for some years. These bearers should
be set into the fuselage using slow setting epoxy.
The four pieces of 12.5mm balsa are then laid over
the plan to ensure they fit together properly to
give the correct profile. When satisfied that these
fit together properly, I glued them together with
aliphatic resin and installed the vertical and
diagonal braces as shown on the plan. All the time
ensuring that these are pinned over the plan and
to the building board. The wedge piece at the rear
of the fuselage is now installed along with a 12.5mm
square hard balsa (grain vertical) to support the
tail wheel. The tail wheel is bent from 2.5mm piano
wire and according to the plan has a light spring
that holds it straight, but on my model I used
a rubber band instead. Also the 12.5mm square hardwood
support for the struts and undercarriage is set
in place using epoxy. It is now necessary to make
the undercarriage mount (UM). I laminated four
pieces of 3mm ply and then set it in place again
using epoxy resin. If you are making this with
a detachable wing as I did you now need to install
the threaded nylon block and ply plate for dowel
location into the appropriate place in the fuselage.
Again epoxy this in place. Another dowel is to
be located at the rear of the wing to stop the
wing twisting on the narrow fuselage, but this
is done at a later part of the construction. Whilst
the fuselage is still pinned to the building board,
the 1.5mm balsa laminating sheeting should be glued
in place. It is necessary to join two pieces of
100mm wide sheets of 1.5mm balsa for each side.
This can be done by laying the two sheets of 1.5mm
balsa on a flat surface and using masking tape
along the join edge. Then turn them over and either
use thin cyno or fold the sheets back and run some
aliphatic along the edge to be joined, then again
lay it flat to allow the glue to set. I left it
for 24 hours to set thoroughly before removing
the fuselage from the building board to laminate
the other side. Be sure to mark where UM has been
installed so that it is easy to locate for fitting
of the undercarriage holes. The undercarriage is
formed from 3mm aluminium and once made needs to
be test fitted and location holes drilled. Also
mark the centrelines and location of the wing and
horizontal stabiliser so that these may be cut
out after tracing them onto the fuselage size.
After cutting out for the wing installation, and
if you are making the wing detachable, be sure
to cut from the rear of the wing up to the top
of the fuselage at about a 45 degree angle. This
is where the other dowel is fitted to stop the
twisting of the wing. Also fit and glue the wing
saddle in place. Mark and cut out the slots to
install the fin in the correct location. Fit and
glue the horizontal stabiliser in place ensuring
it is true and straight. This is easily done with
a set square with a profile model.
The entire entire fuselage can now be sanded ready
for the attachment of the horizontal stabiliser
and fin. The fuselage is now ready for doping and
painting in your colour scheme.
The Struts
For my model I made the struts from long threaded
rods and laminated (using epoxy) two 9mm x 3mm
pieces of spruce over the rods. These were shaped
to the contour shown on the plan. On the wing
end I use a metal clevis and on the fuselage
end I fitted nylon strip underneath with a hole
to take the bent threaded rod. This set up can
be adjusted to ensure the wing is straight and
secure.
Assembly & Finishing
Test fit everything to the bare bones stage, and
visually check everything is right.
When satisfied, you can now start to cover the
wing, ailerons, horizontal stabiliser and the fin.
I covered these with Solarfilm because it is easy
to use and light.
The radio gear used was my JR 662 with the R700
receiver and standard size servos. There are 5
servos in this model because it uses one for each
aileron as well as throttle, elevator and rudder.
I found that it was a tight fit installing all
this into the wing, but it did fit. I used a short
section of inner Nyrod to guide the aerial up through
the top of the wing and I also fitted the switch
into the top of the wing.
The fuselage, rudder and elevators were given two
coats of dope and then painted in the scheme chosen,
using spray enamel and allowing 24 hours drying
between different colour coats.
The OS 40 FP set at the 3 degrees right thrust,
along with the fuel tank, rudder, elevators, control
linkages, tail wheel and undercarriage were all
installed. Throws were set as follows: the ailerons
6mm up and down, whilst elevator was set on low
rate at 10mm up and down and the rudder 25mm either
way to give plenty of ground control. These proved
to be sufficient to perform the desired manoeuvres.
The model balanced right on the main spar of the
wing which proved to be the correct location. Overall
weight was just on 2kg.
To The Field
The day was less than perfect because of a strong
wind blowing down the strip, so I took the mandatory
photos and did the range check of the radio and
a final C of G check. I thought that I would
still give it a go so I fuelled it up and fired
up the motor and set it to run a little rich
because it had not been run for a number of years.
The Pilatus was taxied out to the strip into the
wind and the throttle advanced and within about
10 metres it was airborne. The climb rate was great,
but I did continue to fly upwind until I believed
it have enough air speed to turn down wind. I then
flew around to get the trims set but this proved
difficult because of the gusty wind, so I compromised
and had it flying mostly straight and level into
the wind. It only needed a couple of clicks on
the rudder to have it behaving. This little plane
is quite able to handle these conditions easily.
Time to try it out. It loops nicely and rolls well. When trying to put it into
a stall, at first I first actually had it flying backwards in the wind until
it just dropped the nose a little and wanted to continue on its way. Now it
was time to bring it in for a landing in the gusty wind. I kept the speed up
on the approach and over the field I just backed off the throttle and it almost
helicoptered in with a roll out of less than 3 metres. Truly a STOL (Short
Take Off & Landing) aeroplane just as the full size one was designed to
do.
Added Flying Info
Since the initial try out day I have flown this
little beauty a number of times and this is
how it went. The first time back at the field
was even windier than the first day and I had
a flame out and had to come in dead stick,
and it just kept on gliding into the wind because
it is so light. The next couple of times to
the strip were good weather and I was able
to have some fun. It flies really well and
considering it is only powered by a 40, it
has heaps of power. Stall turns are simple,
as are Cuban eights, inverted flight and knife
edge. I even believe with a little more practice
I will be able to hang it on the prop. The
ailerons are very effective on the low rates
but with high rates set at 12 mm either way
it rolls very quick and is fun if you are an
experienced pilot. I am still a little reluctant
to put it through a snap roll because of the
stresses placed on the wing anchoring point,
but I believe that it will snap fairly slowly
until the C of G is moved rearward a little
to make it more responsive, not that it needs
this for the learner to intermediate pilot.
One point to remember is that with wooden engine
bearers it is important to check that the mounting
bolts are tightened regularly (after each flight)
especially for the first few flights whilst the
wood compresses. I forgot this because I haven’t
had a model with wooden engine bearers for some
years and the plane got very noisy as the motor
worked a little loose so I landed straight away
and tightened the bolts. The vibration from the
loose engine had broken one of the fuel tank
straps. So a few rubber bands were used and another
flight able. So don’t forget to constantly
check the engine bolts.
As stated at the beginning I believe this would
be a good model for your first scratch build,
particularly if you are a learner to intermediate
pilot, but it will perform for those who want
throw it around the sky. So enjoy the experience
of building and the fun of flying this little
plane.
