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Skorpion

So of course you've read part one here. This instalment is being written whilst the Skorpion charges on top of La Muela in Spain. It's now had five or so hours of airtime and its first competition - the La Muela Eurotour F3F.

So what do I think? Well firstly it's important to point out that conditions here are constantly changing and this makes it very hard to perform an analytical comparison with other planes. But this amount of airtime in vastly different conditions does enable me to give a balanced view.

First flights with the Skorpion were uneventful affairs, other than the occasional and complete dissipation of whatever slope lift I started off with establishing fairly early on that, fortunately, the Skorpion will thermal soar with the best of them.

The few glimpses of good or even average air were enough to show that it handles very well at speed and seems to have the raw speed and energy retention in a way not dissimilar to some of the 'unobtainium' German models. Indeed, although I got the impression there was more to come from this plane as I tweaked the set up, it already showed me enough to know it wouldn't do me a disservice in the event. So, rather unusually for me, I decided to give this largely untried plane a shot at La Muela glory.

Sadly though this isn't a comic book and the thermal gods had other favourites over the two day competition. What I can say though is to finish sixth out of an entry limited to 60 or so top class pilots without getting any good stuff to play in is a testament to the Skorpion's ability to keep putting in times that belied the lift it was presented with.

Having done F3F for 10 years I'm normally pretty good at guessing what times I can get out of the lift I'm in but with the Skorpion I was regularly pleasantly surprised. So much so that when Ken and I started playing 'predict that time' with Carlos Cantero, I would pick my time and then deduct a few seconds for the Skorpion effect> And we were consistently right.

Since the competition I've learnt a lot more about this plane. Probably enough to have gained another place or so in the competition if I had been more familiar with it. For example, in anything like average to good air (say sub 45 seconds) it absolutely gobbles up reflex. It can achieve quite amazing performance with very little ballast. Alternatively you can load it up and it really enjoys the Norwegian up and over style.

The design is quite optimised and as such it will flick if you take liberties. The secret is to get your snapflap in early on a curve and use negative exponential on the elevator. This way you get a stunningly quick turn with a significantly reduced risk of pilot over exuberance asking more than any plane could give

I can't wait to get this plane back to some familiar slopes and a few more competitions. It's done enough for me to try another competition with it and take out an option to buy another if it continues to impress when I get it in a more familiar environment.

Summary

There is no doubt that this plane was the best kept secret in F3F. In fact it would probably have been shrewder of me to leave it that way. It's well built, strong, has that certain joy of ownership and delivers the goods in the air. It takes a little setting up to get maximum performance but it's worth it and you can always use my setup.

The waiting list is circa two months but I would be surprised if it stayed that low for long.

Building tips

Pretty standard but there are a couple of pointers that won't hurt.

Use thin (10 or 11mm) wing servos (Volzs or Futaba S3150 work well) which lets you bury the whole linkage which is very worthwhile. As usual you'll need to grind away some of the clevis at the servo end to get bags of flap for crow.

Use fast fuselage servos. The maximum thickness without serious modification is 13mm. Even then with the Volz I needed to lower the tray a little and grind off some of the arms.

The supplied wing wiring plugs work well but don't forget that the solder pins are offset to make room for the solder joint. Don't solder to the wrong side as although the difference is subtle it's enough to mean you'll need to open up the factory holes in the wing and fuz a little.

My elevator hinges were a little stiff. No problem, just open up the elevator and run a small flat head screwdriver along the hingeline from the inside a few times. Stop and check after each time as you don't want to do too much and compromise the hinge (although if you did, silicone hinging would work fine).

Leave plenty of aerial dangling or use a trendy bit of thin piano wire as there's a lot of carbon around.

The fuselage is flat sided where the flaps drop to try and trap air spillage and make for better braking. Works well but you may need to relieve the flaps slightly.

More information from the designer is here and one of the best build documentaries around is here. www.t9hobbysport.com are about to get a consignment for the UK, for the rest of the world contact Thuro.

Click on any photo to see a larger version. Thanks to Mike Shellim for figuring out my camera enough to take some excellent flying shots.

CG circa 104mm from leading edge

Surface/acting as Mode Direction Travel (mm)  
Aileron/Aileron race up 8 all measured at wing tip
aero up 7  
thermal up 8  
race down 5  
aero down 6  
thermal down    
Flap/Aileron race up 0 all measured at root
aero up 0  
thermal up 0  
race down 0  
aero down 0  
thermal down 0  
Aileron/Crow All up 6 at tip
Flap/Crow All down loads at root
Elevator/crow mix All down 6 Measurement at full crow at ele root
Elevator All up 10 Measured at root - neg 10% expo.
Remember I like a very sensitive elevator!
Elevator All down 10 Measured at root - neg 10% expo.
Rudder race up 11 All measured at root
Rudder aero down 10  
Thermal flap (flap)   down 6 At root
Thermal flap (aileron)   down 1.5 At tip
Thermal ele comp   down 1.1 At root
snapflap good air down 4.5 flap at root
    1 Ail at tip
snapflap light air down 3 flap at root (on curve to come before half ele applied)
    0.5 Ail at tip
Reflex     2.5 At flap root worked equally outboard
Reflex ele comp   up 0.4 At root