In the meanwhile, we tried some airex structu-
re for the wings and fin, as well as stabilizer,
and the weight started to drop, but not quite
enough.
Prototype number 2 was scrapped as we
ended up having problems with a test epoxy
resin that was supposed to give great results.
The airframe number 3 was made with inter-
nals in Airex/carbon fibre and ended at just 19
kgs wet, which was the max design wing load.
So I decided to proceed with assembly of this
airframe and started the ground phase testing
with fixed wing incidence and fixed landing
gear.
The airframe was extensively tested at idle
and max thrust on the ground for optimization
of the bypass system cooling and airflow.
Eight temperature sensors were installed in
the plane, connected to our CAN-TEMP sen-
sor board and ASSI module for telemetry. Also
a FLIR camera was used to check out the tem-
perature of different flows from the outside.
Initially, the plane had a nasty tendency of
running hot and imploding the pipes. This was
due to a combination of the long and narrow
inlet duct, high thrust engine and short pipe. I
went through 6 iterations of the pipe/ inlet duct
shape/ bypass venturi taper before I could
comfortably say that the internal air duct was
working properly. This process was conduc-
ted over a course of 3 months, during which I
gained a considerable experience of pipe
design and computation, sheet metal spot
welding and pipe material requirements. Once
this process was completed, we went for the
first taxi tests.
This airframe showed us during high speed
taxi tests that the main gear and nose gear
support bulkheads had to be made from
stronger material than airex/carbon fibre and I
reverted to plywood for the main gear bulkhe-
ad and 3D core material for the nose gear
structure.
After all this research and optimization, I was
finally ready for the maiden.
Unfortunately, I had an intermittent receiver
failure for the maiden of this plane and one
aileron as well as the rudder servo went to full
stop a short while after takeoff. Anyway, I
managed to land the plane in the grass with
the engine shut down and minimal damage.
This short flight showed that the plane was
very tolerant to large flight control deflections
at low speed and well mannered at high angle
of attack, as I landed it at very low speed in
the grass without any stall.
Because the repair would have increased the
weight of this airframe and as it had already
well served its purpose, I decided to retire #
and proceed with the transplant of all the com-
ponents to #4. This one had already beenbuilt and design benefited from the static and
high speed taxi tests conducted on #3.
Prototype #4 was built with full carbon
fibre/airex internals for the wings, fin and sta-
bilizers. The fuselage internals were thorou-
ghly optimized with a mix of Finnish aircraft
birch plywood for the main gear and wing bul-kheads, 3D honeycomb shock resistant core/
carbon fibre nose gear bulkheads and airex/
carbon fibre everywhere else. This plane was
built with a functional variable incidence
system as well as the final version of the
bypass and pipe system. It came out after 2
weeks of intense assembly at 18.5 Kgs wetF-8E CRUSADER
A picture of our Crusader on display at Top Gun 2017.The internal duct assembled outside of the plane. The carbon fibre full bypass is not shown here.The wing internals. The entire structure is made from carbon fibre/Airex.A FLIR rendering made during our thermal optimization process.
The skin temperature remains well within the Tg of 80c.Crusader_Layout 1 08/03/18 13.06 Pagina 7