I looked at the HK site for the Turnigy SK3 5055-430Kv motor- http://www.hobbyking.com/hobbyking/s...ner_Motor.html
-And whilst there are several good comments, no-one has <span style="font-size: small">actually</span>measured current and prop RPM(and actual voltage) atthe same time -which is what we need for proper simulation. However ther was just ONE comment: <span style="font-size: small">" ... I put this motor on a 90 size F3A model. ... with a 6S 5000mAh ... It run a 17x10 TGS prop at 6690 RPM ...static traction is 5 kg. ...in-flight maximum current is 78A. ... I obtain a constant speed for F3A program. Good value! ..."
</span> -So he measuredcurrentand prop RPMat the same time, and we know he was using 6S LiPo (=driving voltage of 22.2V).
This allowed me to simulate this motor on DriveCalc -see attached pic 1for the motor using a 16x10 prop, and 6S LiPo.
Here are some values that DriveCalc gave, all with 6S LiPo, and for different props:
prop Current (A) RPM Thrust (Kg)
15x8 53.6 7965 5.10
16x10 68.4 7500 5.16
17x10 79.5 7156 5.96 (-this is close to values given on HKsite)
18x8 83.6 7028 7.24</p>

-Look like, from the low-ish g/W values, the 17x10 and 18x8 may have been overloading the motor a little.
Interestingly, there was almost the same thrust for15x8and 16x10 props -I would not have expected this ... The 16x10 prop drew much more current, and only gave the same thrust -so there was no advantage in using this prop.</p>

<span style="font-size: small">However: A 16x8 prop gave: 63.2A, RPM 7662 and 6.4Kg thrust (see pic 2)-</span>So: You may well be much better off with a 16x8 prop (-which is the exact prop that rosnik wants to use .. -but he is using 5S LiPo ...)
<span style="font-size: small"> It is notablethat the 16x8 prop drewless current than 16x10, but gave <u>much</u> more thrust (6.4kg)
</span> -Notice also that the 16x8 prop has a much better "Thrust efficiency" of 4.6 g/W (compared to the 16x10 prop which has only 3.4 g/W).

<u><span style="font-size: small">It looks like with 6S LiPo, the <span style="font-size: medium">16x8 prop </span>may be optimal for this motor ..?
</span></u>
From the HK website, manuf. specs state this motor has a max current of 70A, and max power of 1750W. The 16x10 prop is almost at this limit of 70A.

-Hope this helps</p>