Polish C/L Nats 2019

[Matt Piatkowski]

Hello,
The Polish C/L Nationals in stunt (F2B), C/L racing (F2C) and C/L speed flying (F2A) were held in Wloclawek, Poland from May 31 through June 02, 2019.

I participated in F2B with my Big Red.

The F2B results and the group photo of the F2B competitors are attached.
F2A and F2C results are available on http://f2b.cba.pl.

Details: the contras (counter-rotating propellers systems) were used by five competitors, including Krystian Borzecki who won, Sylwester Kubik who was third and Pawel Dziuba who was fourth. Tomek Jadczak (14 th. place) pioneered the use of modified Himax 3516-1030 system that was changed to Kv=500. This system is therefore known now as Himax 3516-500 and works with 6S battery.

The contras offer immediate improvement in the pattern execution and quality and are, in my opinion, the way of the future in the C/L stunt. I expect to see more stunt planes powered by contras during the next year WC in Wloclawek.

Please contact me with questions regarding these unique power systems.

Regards and Happy Stunt Flying,
M

[Peter in Fairfax, VA]

Thanks for the report.  Why am I not surprised that the favorite colors are red and white?

[Christoph Holtermann]

Thanks for the Update. Not a bad participation at your NATS!

How about the sound of the HIMAX-System? It should be somehow a little more silent than the geared system of Krystian and others.

Congrats to Krystian. He is an excellent pilot and I was impressed in Bitterfeld (GER) early May how slow he could fly the wingover. He flew 5.4 sec laps and the wingover literally lasted forever :-)

Also, I had the impression that his plane turned around an axis further forward than many other planes, comparable to the Gee Bee Sportster of Remi Beringer at that time. Is the CG on Krystians plane so much more forward? I remember having seen his batteries just inside the wing more or less at the CG position.

Christoph

[Matt Piatkowski]

Hi Christoph,
Himax system is subjectively quieter than the geared (Gaudynski==Polish Contra) system but no noise measurements were done. I would love to use the noise meter and compare the frequencies distribution and the noise level.
I will think about it.
The Polish competitors using contras use basically 12x6 propellers but these props. differ from model to model. For example, Krystian Borzecki and Sylwester Kubik use 12x6 carbon composite props. similar to Graupner's electric. Pawel Dziuba uses his own and Gaudynski's carbon composite props and Tomek Jadczak uses another 12x6 prop. geometry.

Krystian's plane (see the attached), has the thrust axis, the wing and the horizontal stab in one plane - this makes the plane virtually symmetrical w/r to the pitch axis (Y). Perhaps this causes the "ease of pitching" about the Y axis located a bit more FWD than the other stunt planes? I do not know the exact location of the C.G in the Krystian's RTF RED BULL plane. I will check this during the F2B WCup in Wierzawice, Poland (28-30 June 2019).

Krystian's batteries are loaded from the top and are 6S 2300 mAh. The hatch is visible on the attached photo.
More questions? Just ask...

Later,
M

[Naomi Macklem]

Hi Matt,

Thanks for the results and the photos.  Your Big Red model looks great.  Keep up the good work.  Len & I are getting read to leave for the Brodak Fly-In.  Hope to see you some time soon.

Naomi

[Wolfgang Nieuwkamp]

Hello Cristoph,

Using counterrotating motor/prop combinations, you will completely get rid of any gyroscopic effects ( assuming that the motors and their props have the same inertial moment, they rotate at the same speed, and the wheels are not turning :-) ).

Then there is no need to put the motor axis above the wing chord (or below, for pusher systems), or to give the stabilizer a small incidence.

For me, this explains the easier turning.

Regards,

Wolfgang

[Matt Piatkowski]

Hi Wolfgang,
You wrote: "assuming that the motors and their props have the same inertial moment...".

The plane that is being discussed, namely Krystian Borzecki's RED BULL, has the geared contra system. In this system, a single motor powers the gear box that powers the counter-rotating propellers. In this system, the gyroscopic moments of the props., created by sharp corners, have the opposite signs and cancel each other. The motor's rotor, however, has its own gyroscopic moment in corners and this moment is not cancelled. The gear box has four straight teeth gears (spur gears) and these gears have almost the same weight and dimensions. Two of these gears rotate CW and two - CCW. In this situation, the gyroscopic moments of the gears in sharp corners almost cancel each other.
 
Consequently, RED BULL flies the corners with minimal but existing unbalanced gyroscopic moments coming from the motor's rotor and the gear box gears.

The effect that Christoph was writing about, namely: "...his plane turned around Y axis (PITCH) further forward than many other planes" cannot come from the effect of the unbalanced gyroscopic moments described above as they, whatever their magnitude, act about the Z axis of the plane (YAW).

Regards,
M