F5J gliders

COBRA F5J is a unique new concept for FAI class F5J.
Goal was to create a optimized airplane with best weight-to-strength ratio. All parts and details were optimized for this reason.
Also important was to keep the drag as low as possible to achieve perfect gliding performance at low flying weight. The new model design ( geometry, construction details...) should also provide all the requirement of modern F5J competition.

This ended in following details:

*minimized fuselage diameter for the tail boom to get best strength and weight
*very thin airfoils for low drag
*winglets and pylon fuselage for best drag and handling
*variable fuselage design to optimze length of nose and boom for various components.


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Main point was a high tech wing construction with doublecarbon cc26 carboline together with new cascell foam. Lot of effort was put in fuselage design with 5 single carbon pieces for optimal building technique for best strength and weight. Tailboom starts at wing leading edge with 32mm going down to 16mm at the v-tail. Fuselage nose has maximal room for 4s1000mAh Lipo batteries.
Pylon configuration fuselage offers best grip for throwing the model gider and low drag in fuselage-wing interferrence.
v-tail servos (2x dymond 45) are placed in v-tails in STANDARD and STRONG-version. Light FAI-version has servos under canopy.

There will be 3 versions available:
LIGHT/FAI-Limit: wingloading about 12,9 g/dm² / CC26 wing / light spar
STANDARD: wingloading about 15 g/dm² / CC26 wing / standard spar
STRONG: wingloading about 17 g/dm² / C64 Spreatwow / strong spar

COBRA comes in high pre-fabrication.
*ready installed wires and connectors in centerwing
*ready installed gap sealing
*ready installed iDS linkage horns in flaps and ailerons
*ready installed horns in v-tail

Airfoils and winglet aerodynamics are designed by Max Steidle ( 6,5% thickness and about 2,2% camber) and overall idea and model construction design was done by Stefan Eder:

HISTORY:

Background for COBRA was Stefan Eder`s PACEMAKER from 1995. This F3J-glider had a very sleek fuselage with 20mm diameter and carbon vaccuum badged wings with winglets featuring a Norbert Habe airfoil. Stefan Eder built also some hand launch gliders in the early 90`s with winglets and made lots of testing with those details.

Pacemaker had very good performance and Stefan Eder won a international EuroTour competition in Chrudim/CZE 1996. But soon the F3J tows are gettering harder and harder and the thin tailboom was not able to do these hard launches and alternative material was not available these days. For this reason the model concept was delayed until the new FAI class F5J appeared and now it was time to bring it back in a modern version.

We tested several winglet configurations and other details on our models ORCA and SATORI to prove the best model design.