made up of carbon/foam/carbon sandwich of 6mm thick (same resistance
as aircraft plywood of 6mm but 2.5 times lighter).
The assembly of the framework, is done directly over a plan with the proper jigs. The total weight at this point including the firewall, landing support, and wing mount support, is only 480g.
The advantage is realized by the installation of accessories. On a fiberglass fuselage, the landing gear is held by a plywood structure made into a box, which is 300g for nothing. On the this structure, a carbon plate plus foam, 6cm x 18cm (30g) is all that is needed. The firewall only serves to bolt the cowling, as the engine now mounts directly on the structure via a Hydro mount. Resulting in an extra 300g gained on the engine mount. The radio, is mounted directly on the carbon tubes via nylon adapters. The servos, mount directly on the tubes with 2mm nylon screws (it is plenty big and it adds a bit of give). Again, more weightsaving because I did away with the servo trays.
The "Skins"
The exterior skin which gives the shape of the fuselage is molded with a single layer of fiberglass ((163g/m2), with the whole thing coated with a carbon veil. When the skin is removed from the mold, it is very flexible, but due to its utilization, this meant no problems. In reality, the fuselage only serves to decorate, and does not participate in any way to the integrity of the structure, as it is completely removable from the firewall to the rudder. It is held in the front by 2 Zeus and in the back at the bottom of the fin, by 2 nylon screws. The canopy, to lose even more weight, is fixed permanently to the outer skin as a canopy of this size (72cm long) is rather hard to make removable, and is a risk factor should it get detached.
Wing Construction:
There are many solutions possible:
--Cut foam which is very fast to build and is one of the better solution if
you find the proper materials. I had the occasion to look at the wings that
are fabricated by ZN Line and I came to the conclusion that we can
fabricate wings almost as light as buildpups. good for you Mr. Nowik, the
materials must have been finely selected.
--Fiber/foam sandwich; (check the results on the full size Cap 232), I
think that this is still the best solution. Unfortunately, to master the
technique of Nomex and Honeycomb and Vacuum Molding, still remains
a mystery to most of us, and the price would be the same as with built-up
with contest balsa.
--Built-up structure: this is the solution that I decided to use. Lightness
and solidity is of the utmost priority. With this type of construction, you
start with the purchase of a good electronic scale (if you don't already
have one, you know what to give your wife for mother's day...) The balsa
selection is the secret of success. The simplest solution is to order the best
contest balsa from your retailer, but expect to pay top maney for the
diifference. Don't rely on the color of the balsa, only rely on the scale. The
weight of a plank can vary as much as a ratio of 1/3.5, ex. 16g for contest
quality compared to 40g for regular balsa. For a realistic example, an
airplane like my Sukoi, utilizes 800g oa balsa, so with regular balsa you
would have 2800g. That's 2kg of extra weight.
--The wing is made up of 2 longerons (superior and inferior). They are
made up with 2 sticks of balsa 5mm x 5mm glued on a light skin of
carbon 4/10. Believe me, it tough for the flying qualities of the Sukoi. All
of the ribs are 20/10 and lightened and are 8cm between each. Only one
side is reinforced vertically and the whole wing is sheeted with 20/10
balsa. The wing is made of opposite spiraling carbon fibre of 20mm dia.
(length of 75cm of which 24cm in the fuselage), it weighs 75g. The
sockets are made of fiberglass. A finished wing without the servo or the
final covering (Solarfilm) weighs 370g (1m long, 56cm at the root and
27cm at the tip. The final covering as I said is with Solarfilm because of
the weight, (always the weight). With the wing finished, with 2 air brakes
37cm and 2 servos @ 54g/each, it weighs 740g.
