Guppy Foam Glider
This pages describes the build of a nice glider, based on Guppy design of Misja Sersen. A beautiful curved glider design!  You can find lots of info on this design on the RC forum  I have enlarged the Guppy-II design to get 2.1m wingspan.

The construction is completely different from the traditional balsa build; Instead, I used Depron and carbon fiber rods, with a sandwiched center plate for the fuselage.

Basic setup is a 6mm diameter carbon tail boom, and sandwiched fuselage (2 x 1.5mm multiplex sides with 6mm Depron in between)

T-Tail with carbon tubes glued in tail boom with one pushrod curved upward for elevator and the other for rudder. Tail covered with 2 halves of 6mm Depron.  Rudder hinge will be transparent tape.

Finished fuselage structure, tail boom sandwiched in Depron, and glued into fuselage.
Elevator section from 3mm carbon glued into two 3mm halves of Depron. Elevator hinge will be transparent tape.

Fuselage sides constructed from multiple layers of sanded Depron. The basic shape cut with hot wire.

Canopy made from PET bottle: First a canopy shape from blue foam, then insert the blue-foam with kegs to make a tight fit. Then shrink the PET plastic in boiling water.

The result is a nice tight shrunk plastic over the blue foam dummy. Cut with some margin, and then trim on final fuselage.

Canopy has Depron insert, with space for battery and speed controller. Canopy slides in tube at front, and clicks to wing section with small Neodymium magnet.            

I added a small brushless motor with 8x4.5 folding prop to the glider. 

Servo's for rudder and elevator mounted under the wing. The Depron sides have the spaces cut-out for servo, receiver and speed controller. Depron painted with water-based Acryl paint using roller. Then the Depron is covered with transparent self adhesive tape (packaging tape)

Wing construction is also from Depron and carbon rods: The top and bottom are 6mm Depron, with trailing edge cut to 0.5mm thickness with hot wire. Carbon rod is sandwiched between two balsa strips. 

Two aluminum tubes are glued to the carbon rods: The wings are slid over two 4mm steel rods on the fuselage. The top depron cover is glued to the bottom layer leading edge: then using hot air gun (sufficient distance!), the Depron is gently bent backward. Use white wood glue to glue everything together under weight pressure.  

The wing tips have around 14 degrees dihedral. glued to main wing with some re-enforcements.
Use an accurate fixture when gluing the wing and tip together. There is around 5mm wing-tip twist.
Wings are also painted with Acryl paint and covered with transparent packing tape.

Some pictures of the wing to fuselage construction:


Finished model: total weight 850 gram.

First flight: Looks good in the air, relatively stable, but sink rate still a bit poor. The small engine has insufficient power to make fast climb possible. (only 270gram pulling force)

To get some idea of motor characteristics with different motor / prop  combinations, I made a jig that measures battery current and pulling force.

This is a slightly larger motor, a brushless 400 type: A24-12L-1600KV.
The 1600KV gives high RPM, but is not suitable for big props. Therefore I rewound the motor with 23 turns instead of 12 turns. Still connected in Delta configuration as original. KV will be around 830.
With this setup with 11x8 folding prop I get 350 grams of force with 5.5A @ 7.2V : good for ~ 20 minutes @ full power with 2.8Ah battery.

With this motor, better climb rate is possible, and is more efficient than the small brushless CD ROM type.

I may build new wings for the glider, with aileron and airbrake function added.