Martin Whitelaw takes us through
the stages of his Gloster Javelin T Mk.3, from conception
to maiden flight.
When Alan Hulme
asked me, or was it commanded(?) to write an article on one of
my PSS projects I thought this was a chance to put something
back into our sport (sentimental poohoo), but which model?.
Would it be the technically difficult Victor SR2 or the aerodynamic
phenomenon that is the Buccaneer S2. Alan wants to encourage
new blood so I decided to use my new 'floater' as the basis
for this article - the Javelin T Mk.3.
The Javelin project
started out after a discussion with my design guru, Ron Collins,
who told me that it had already been done but was not an ideal
PSS subject. That's all the motivation I needed and off I
set to get my hands on a scale plan and elevations. I decided
on the T3 trainer version as, to my eye, it looks better than
the shorter combat version and the increased nose length would
allow for an easier CG correction.
As with all my
recent models I started with a 3/32" balsa box parallel
centre section with tapering sections fore and aft. To this
I attached the fin, complete with elevator mechanism. On the
Javelin the all-moving tailplanes (brass square tube in tailplanes)
had to be more or less complete before moving on to the next
stage, which was fuselage foaming.
Using 1/8"
thick balsa formers as a guide at all significant changes
in fuselage section, white foam blocks are glued to the central
box and formers. Don't use ply for the formers as small corrections
to the finished body shape are then more difficult. Once the
white glue has dried the fun starts and the foam blocks can
be hack sawed and sanded until the fuselage shape is achieved.
I always trust the finished foam outline to eye and it always
amazes me that on returning to the model you invariably see
other high spots and areas for improvement. Never rush this
stage as the finished model will suffer if you do. Go away
and cut the wings while viewing the fuselage from time to
time and returning to 'fettle' the shape as necessary.
Talking of the
wings, I prefer to foam cut and veneer mine and the Javelin
presented a few problems in this respect.
Firstly, the wing
position in the fuselage meant that there would be very little
left of the fuselage if a one piece wing was adopted and
secondly, the production Javelin's had reduced sweep back on the wings'
outer panels. No problem I hear you say - go for plug-in,
built-up wings. Not me. I stuck to a one piece foam veneered
wing.
To reduce drag
on the delta wing, while maintaining a reasonable scale look.
I opted for an E374 wing root profile with a 5% thickness
ratio and a 'bit' of additional thickness on the underside.
The outer wing panel, including the tip, is again E374 this
time with 6% thickness ratio. Thanks again to Ron for the
use of his computer programme. A satisfactory taper from root
to tip being achieved despite the change of outer panel sweep
back. Inner and outer wing panels were epoxied together before
cutting out the ailerons, fitting the 'inner' trailing edge
and aileron torque rod. Refitting the inner wing foam trailing
edge over the aileron torque rod, then allowed each wing
half to be veneered - minus ailerons. Aileron sections were
edged separately with 1/4" balsa before they too were
veneered. The wing halves were glued together and balsa wing
tips, with 1/ 32" ply sandwiched in between, fitted,
checked for alignment with each other and sanded leaving the
ply to form the hard trailing edge. A good aileron fit was
achieved before the wing was laid aside.
|
An
excellent photo showing just how thin the fuselage on
the Javelin is with the wing section removed |
A
shot of the underside showing the wing seat and elevator
servo position. Note the receiver and battery shoehorned
into the aperture just in front of the bulkhead! |
 |
Back
to the fuselage, a ply spine was cut into the top of the fuselage
to strengthen the wing aperture and, with a temporary pink
foam nose cone fitted, the fuselage was planked with 1/16"
balsa, white glue and thousands of dressmakers pins. On completion
of planking the rough edges were sanded down and the temporary
nose block replaced with a laminated balsa one, again sanded
to a final profile. I find that this method of construction
allows for a more complex body shape to be achieved without
adding significantly to the overall weight of the model and
resulting in an extremely tough fuselage, no impact tests
please!.
With
a steady nerve the fuselage wing opening was marked and hacksawed
out (always a tense moment). The wing seat was sanded and
lined with liteply and balsa. The fuselage bottom portion
was shaped and refitted to the wing underside and with wing
bolts front and rear the fuselage/wing was ready for the servos
and actuating rods/cables. One result of the mid mounted wing
design was a requirement to hollow out the wing root around
the fuselage mounted elevator servo and careful routing of
the actuating rods and cables.
An
'in the raw' test flight was thought necessary to check out
the tailplane incidence, fuselage flying attitude and of course,
Ron Collins' predictions. With a well forward C of G, the
Javelin was launched into a stiff breeze and to my surprise
all appeared to be within tolerance and it flew steadily,
given the amount of elevator up trim I had to apply to correct
for that extra nose weight (video available for any doubters).
No heroics. I cut the test flight short when I remembered
that I had only secured the ailerons with drafting tape, good
job too as one of the all moving tailplanes had worked its
way close to coming off. A tighter fit is obviously required.
Martin
Whitelaw obviously pleased with his Gloster Javelin
T Mk3 |
 |
Finishing
the model in solarfilm, silver underneath and drab green top
surfaces, the upper surfaces were then masked off to produce
a camouflage pattern using car spray. Nose, black and
yellow coloured rings were spray applied and roundels were hand cut
from solarfilm and lining added with tape and pen. Cockpit
canopy was beautifully made by Andy Conway to my less than
perfect wooden former, showing all my inbuilt imperfections.
I'll have another go at the cockpit canopy some day. The upper
surfaces of the Javelin were finally sealed with a light coat
of clear lacquer.
Now
that its finished I'm hoping for a good flight at the Hole
of Horcum event in October. (We can inform our readers that
the Javelin did indeed fly successfully on a number of occasions
at the event).
Gloster
Javelin T Mk.3 model details:
Wing
span 38"
Model length 39"
Flying weight 2lbs 6ozs.
Wing loading l4ozs/sq.ft.
No.
of channels 2. Aileron & Elevator Construction:
Wing
White foam and veneer.
Fuselage White foam. balsa skinned.
Fin Built up. balsa skinned.
Tailplanes Laminated balsa.
Finish
Solarfilm and car spray.
Martin Whitelaw.
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