in Jet International about his L-39 in a future issue as he has pow-
ered it with a Schuebeler EDF unit: an interesting conversion that
we’ll describe in depth.
The airbrakes required a lot of work to install and to get them mov-
ing freely, adjusting their shape to correspond to the recesses
moulded into the fuselage. As Fei Bao operates the airbrakes with
two air rams, there are no parts that can be used to convert them
to be controlled by single or twin servos. So we made our own
Vetronite epoxy/glass composite control horns, which were also
used as pivoting hinges, glued inside the airbrakes with Hysol.
We then decided to use one servo for each airbrake for simplicityAUTHOR:MARCO BENINCASA
A nice scale jet deserves a nice scale cockpit!The fuel tank mounting system comprises of 3 additional for-
mers, and the tank is secured with glued on aluminium strips
that screw to side supports. Note that the original tank fittings
are been replaced with higher quality products by Osvy Modeland to ensure perfectly synchronised movement. It’s possible to
arrange things so that only one servo is used, but this would have
required more time and effort to make a positive and slop free link-
age between both control horns and the servo, and as we needed
the model completed and ready to test fly as quickly as possible,
the twin servo solution was much simpler and quicker.
There was no information in the instructions about the tank instal-
lation in the fuselage, and no fitting parts were supplied, so we had
to develop a mounting solution. We wanted to secure it firmly in
place with a strong mount (we must always remember that our jets
often have to cope with flight loads of more than 4 G, which means
that a full 4 Litre tank can have an effective weight of at least 16
Kg!), but allow it to be removeable easily for maintenance.
After a lot of thinking we (and when writing “we” I mean my father
Giulio and I!) made 3 new wooden formers, (two on the upper side
and one underneath) using the wingtube outer mounting tube as a
2nd lower mount, gluing a horizontal wood plate onto it: the tank
was now secured between these mounts, where we glued some
white rubber soft mounting strips. To secure the tank in the longi-
tudinal axis, we made two wood/carbon supports glued to the
inner sides of the fuselage, matching the front section of the tank.
Two rectangular metal pieces are glued on to the tanks, and are
secured to these supports with two screws. To be super safe, we
then glued an “L” shape metal piece to the rear of the tank, this
being secured with a screw into a hardwood block glued in the
centre of the “Y” shape of the air intakes. In this way the tank is not
going to move in flight no matter what happens, and we can
remove it from the fuselage by undoing just 3 screws.L39_Layout 1 08/03/18 10.13 Pagina 6