Slope testing the Chocofly JS3

After Friday’s maiden flight in aerotow, I could test the new Chocofly JS3 Rapture on the slope today. The conditions were perfect for the JS3, very light lift, with great intermittent thermals. We had three JS3 on the slope, one scratch-built by Georg Staub, identical to my scratch-built, with around 6.3kg, one scratch-built by Richie Oberholzer, without FES, around 5.5 kg, and my Chocofly with JETEC E-70 with around 6.6kg. We were all flying the 18m/5.14m version (I only have this version for my Chocofly JS3, and always fly the longer wing version with my scratch-built).

The Chocofly version is virtually identical to our scratch-built JS3. The differences are of course that the wings are fully moulded, whereas our own are foam core with carbon/glass layup. The elevator of the Chocofly JS3 is approximately 1cm less deep, and the fuselage approximately 2cm thinner. In addition the wings have 3 rather than 4 control surfaces.

With the identical wing and elevator profile, the performance of both planes is however very similar. We did some formation flying in different camber settings. My JS3 and that of Georg performed equally well, with the Chocofly version giving the impression of being slightly more performant in thermals. With more robust wings, the upper end of the speed spectrum is of course also higher for the Chocofly version – I got to 230kmh in some of the low passes.

The JS3 (both my scratch-built and the Chocofly version) ist the best scale glider I have for flying in thermals. It picks up the least bit of lift and allows for slow, tight turns, very similar to a F5J glider. With the multiple dihedrals in the wings, it turns mostly on rudder and only needs minimal aileron. Even with massive camber settings it is hard to stall, and it announces a stall very nicely – nasty stalls are very rare. The nice things about the Chocofly version is that the 5.14m also allows for higher speed passes, and of course having a JETEC rather than FES makes the plane so much nicer to look at.

To note is that there is also a 4.28m version of the JS3. I have shorter outer wings for my scratch-built JS3, but, to my shame, have never flown it with these. I may however be tempted to order the shorter outer wings for the Chocofly version. With the shorter outer wings it should be quite the slope racer – although in the GPS version not as much as my Apline Edition Diana2 (with which I can do just anything). To be decided.

I’m still not done with determining center of gravity and longitudinal dihedral. I did move the CG somewhat backwards but have found that I still need quite a bit of uptrim on the elevator. I hope to get some test flights on one of our local airfields soon to sort this out. I also still need to sort out the battery issue. I’ve using 2 older 3S 3700 LiPos as a 6S setup, with 4mm plugs, which I’m not happy with. I’ll be measuring Ampere/Watt of the JETEC shortly to see what power flows, and will probably adjust plugs and battery. I’ll also replace my 2S LiPo that I use as a backup power source (next to the BEC). More on all that later.

Even with all this, the plane flies great already, it will only get better. I’m a big JS3 fan, together with the 1:3.5 Diana2 it’s my favourite plane.

 

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