Katana’S 120 by Sebart.
Following the German Acro Masters 2010, on our way back to Spain, we took a detour through Italy in order to spend a couple of days with one of the worlds best designers and pilots, Sebastiano Silvestri.
I was very fortunate in that we were able to bring back to Spain one of his Katana’S 120 in order to perform this article.
Even though these models can be put together in either electric, glow or petrol, I prefered to follow Sebastiano’s procedure, of using an electric motor. Furthermore, to assure the best possible system was used, after some conversations with Sebastiano and Hacker, I decided to go for the Hacker A-60-22S and it’s speed controller , the Jeti Spin 99.
Having recently used Sävox servos in the 2.6m Sbach, I decided to use them in this Katana’S also. Even though they are much more powerful than what this model required, the speed and precision is a great advantage.The model used was the SC-1268MG, which on 7,4v have a torque of 26Kg at just 0,11s
As I wanted to get the full power and speed from the servos, so I run them on 7,4V direct from a 2S lipo. However, as I did not want to have to use a powerbox to distribute full voltage to the servos and only 5,9v to the receiver, I managed to make a set of extension leads that end up with all positive and negative wires together, in such a way that these can go to the lipo, and an independent Powerbox-Systems regulator uses the same lipo to power the receiver at 5.9v
The build of the model is very easy, and I did not encounter any real problems.The only process that slightly delayed the build was that the Robart hinges needed to be glued into their predrilled slots
Bolting the servos in was just like in any model, using the included high quality accessories to attatch them to the control surfaces.
Bolting the Hacker A60-22S on to the firewall was a very simple process using the motor cage also produced by Hacker-Motor, which allowed me to center the spinner to the cowl to perfection. The speed controller only requires to have the gold banana plugs soldered on and then attaching to the motor just in the same way as with smaller motors (three wires, which if the motor spins the other way simply swap two over.
With the model finished, it’s time for the best part, the flight!
Being my first electric model of a good size, the test flight was a new experience, but what an experience!
From the take-off, it was obvious that there was nothing to be worried about and that the model was going to be very precise and smooth.
Once correctly trimmed out with just a couple of clicks of trim, using the recommended surface setup the precision of the plane is quite amazing, but having said this, what else could I expect from a model designed by one of the greats of the F3A, as is Sebastiano Silvestri.
With full throws we start trying all the different 3D maneuvers, and don’t seem to find any that it does not like doing.The only inconvenience is that a small mix is required from rudder to elevator, in my case %6 one way and 8% the other (due to the engine torque)
With the throws set up as I like them is when I really started having fun. The model is a mix between a 3D shocky and a feel of a model quite a bit larger than it actually is, while also being very precise, allowing us to pointthe model anywhere we want.
The high alpha maneuvers are surprisingly stable for the models size, I was especially surprised at how stable the positive harriers where, as in other models these are usually rocky with the Katana it is quite the opposite.
With the electric motor, the 20*11E prop and full rates it is even possible to perform the anti-torque-roll, which other than in shockies is a very rare maneuver to see.
The power plant is spot on, with an amazing power, possibly even too much. I have currently reduced the full power to 85% as it is almost too powerful for the model, and at 100% you never reach full power.
So that you can see how it flies for yourselves, as well as shows this year you can find the first video and photos here: