AIRTRONICS GRAND ESPRIT

The Airtronics Grand Esprit is a great old sailplane designed by Lee Renaud, it was, in fact, the first multi task sailplane to be kitted! Back in the 80's when this model was kitted it was quite popular and did place well in many contests. A new company called Aerosphere has purchased the rights to the Airtronics line of sailplanes and will revive the kit in late 2007. I have obtained a copy of the plans from a friend of mine so that I could plans build one of these massive planes. The Grand Esprit spans 134" inches and should be a blast to build. My friend Jim Brandon has scratched one and has the process on the web at 

http://theshope.net/hobby.aspx

Jim is a master craftsman and it shows on his build, I will try to build mine near to his standards. In the meanwhile take a look at the builds and watch for Aerosphere to put these kits out soon.

Building the fuselage is simple. The fuse is a basic box structure with formers.

The rest of the fuselage is a fiberglass boom. I believe the original was designed around a pool cue blank. I did the same thing with a $14.00 cue from Wally-world.

$14.00 pool cue from Wal-Mart. Covered with mylar ready for rolling my boom!

Here the fuse has been sanded to shape, the root ribs have been installed (changed the airfoil to E205 on main panels transitioning to E193 at the tips) Thanks to Jim Brandon for that tip! The canopy has been cut from pink foam and also sanded to shape. Light weight spackling is used to fill imperfections and to blend the root to the fuse.

Here is a picture of the filling process, you can also see the former with the hole for the boom and the fairing between the root ribs and the fuse.

Most of the filling has been sanded away and the root blended to the fuse, starts looking like a Grand Esprit!

The foam canopy was removed from the fuselage and given three coats of medium glass from SIG, then the base was drilled and automotive thinner was poured in dissolving the foam out and leaving the fiberglass canopy.

Looking good!

The v-tails are standard built up. I used a spruce sub leading edge and trailing edge for greater stiffness.

Here is a shot of the fuse with the boom installed and trammeled, the base of the V-tail and the built up V's.

 V-tail mount base, balsa, ply and filler.

One of the major problems with the Grand Esprit was the spar system used. It was laminated from three pieces of spruce

1/8 x 1/4. Also you can see how the tube holding the wing was mounted. The rear sub spar was also very weak, but we have to see what it was designed for. Back in those days winches weren't as strong as today and zoom launches had not come into everyday flying. So as designed, it served it's purpose. I did change the spar construction, also a tip from Jim Brandon. I used 3/8 x 1/8 spruce with vertical shear webs, also capping the spars with carbon (three times as thick on top as bottom).

This is the jig used to cut the shear webs.

As you can see this method produces equal sized shear webs and they are very easy to make.

Here is the genesis of the spar system. Shear webs sandwiched between spruce ready for carbon capping and 1/16" ply to tie the top piece with the bottom piece of spruce.

Camera died during the process of building the wing. Here's what it looks like before the spoilers are built and it's covered.