François Cahour – Troll at Col du Joly

This is, unequivocally, one of the finest aerobatics videos I’ve ever had the privilege to make. François Cahour should need no introduction… enjoy.

About the Troll:
The Troll comes from the lineage of the Quartz, which was originally published by François in an issue of the French RCM in the mid 1970s, according to this article on RC-Pilot published in 2006, when the Quartz celebrated its 30th anniversary.

The Troll is the latest iteration, and is 2m span. The Quartz is 2.5m and the Sylphe is 3m. When I visited François at his chalet in the Alps, I was privileged to get to see, hold and closely inspect all of these gliders, and they are truly inspiring works of art.

François, on his own, built each glider from scratch, and they’re all very similar iterations of what is clearly his idea for the ideal “polyvalent” aerobatics glider, capable of executing in precise and perfect manner every conceivable aerobatics figure, including flips and flat spins, while also being light enough to VTPR and absolutely capable (it was demonstrated to me) of thermalling for hours.

The planes have composite molded fuselages, and foamcore wings that are laid up in a female mold and (I believe) cured under pressure. The wings use carbon fiber reinforcement and the ailerons were as stiff as steel – I was really impressed.

The really fascinating technology is “under the hood” in the cockpit area. François has setup these planes with everything:

• A slop-free mad-stab (driven by an elliptical pulley which is itself mounted to a servo in a sliding tray that allows the pulley to be tensioned via a bolt) allowing flips without any hint of flutter, even at very high speed;
• The full span flaperons are driven by linkages entirely contained within the wing of the plane (wasn’t sure if this was hidden pushrods or RDS, but you get the idea)
• The wings themselves are ALSO setup for wingeron control
• The most conventional thing is a pull-pull rudder, which somehow routes through all of the previous stuff with no worries and helps keep the tail very lightweight and very powerful
• There is an auxiliary motor used only when the lift dies, to prevent huge hikes (François is, I believe, in his mid 70s, though he easily beat me up every hill we climbed together)
• The whole plane is light enough that it slows down for delicious low-level VTPR passes
• I was utterly blown away

Here’s an “under the hood” shot of the cockpit:

It was a really powerful experience for me, to be honest, seeing what one is capable of achieving if he or she puts their mind to a task and maintains focus on achieving the goal, no matter how long it takes. It was a lesson I really needed to learn, and I’m forever grateful that François’s example was made so concrete for me.

Steve