Excalibur, cliff glider.

The Excalibur

Would you prefer a long or a short Excalibur ? Or both ? ;-)

You have reached the Excalibur page, which is not finished. But there is already food for thought !!

I. General conception and philosophy

   Why this Excalibur ? To allows the airplane pilots from our club to try to fly a glider. This glider had to be funny to all pilots, but not too much hard to fly. It had to be used as a "school glider", too.
   Moreover, it must be cheap, easy to build and strong to put up with hard landing in the cliff turbulence.
   We computed in our brains, and it gave that :

Main characteristics
Wing span	1750/2200 (mm)
Length	1130 (mm)
Chords	Root : 190 (mm) Wing tip : 130 (mm) Removable wing tip : 90 (mm)
Airfoils	SD-6060 (modified E374) Removable wing tip : SD6060 to modified S-4083
Wing area	27/32 (dm²)/
Weight	950 (g)
Wing loading	35/29 (g/dm²)

   As you can see, the proportions are fairly common, this gives good handling capacities. The fuselage is a bit long with short wings, but that is a good thing for fun flying. And there are removable wing-tips which transform the Excalibur to a calm sailplane that looks bigger than it is.
   This wing tips were design so that they don't change the CG location, thanks to the soft "mean aerodynamic chord"

   The airfoil, in fact a modernized E374, was choosen for its gentle habits and its habilities to revert flying. I am learning to master negative flight with gliders thanks to my Excalibur. The Excalibur likes revert flying.

II. Building.

Fuselage.

The fuselage is made of a simple "balsa box", greatly smoothen by sanding the edge, thanks to triangular spar inside the fuselage : the section is nearly circular next to the tail. The belly is covered with 100g/dm² glass fiber, to make a sort of skid.
This fuselage is large enough to accept standart radio installation.

Wing.

Les deux types de saumons : court ou rallonge.

It is made of white foam, covered with 1.5mm balsa skin in a vacuum bag. The balsa is glued with PU (PolyUrethane), instead of epoxy resin usually used. And the concusion is that it works very well, it is light and strong.
The aileron are quite large, maybe too much on my model : the following will have less large but as wide ailerons. Anyway, they can be used as flaps and airbrake.
The removable wing tip widden the flying enveloppe, so that they become quite usefull as soon as wind weaken, or for thermik flying. They are classicaly built, with ribs and spar. A small piece of scotch tape will secure the wingtip in flight.

Les empennages.

III. Flying the Excalibur.

Thermik flying.

At the cliff.