Originally Posted by jbarchuk
Otto mentioned prop charts and calculators. http://www.ecalc.ch
*JUST* recently changed to a 'subscription' format. They give -some- data for free users but I think only 25%. By that I mean that they have hundreds of batteries and motors and props in the database, but it 'varies' what it displays to free users, and cuts waaaaay down on the options. So, a particular motor you're looking for might not be in the displayed list at the moment. I've been on the net for 25 years (flying for only 3 years) and this is the *FIRST* subscription site I've ever signed up at because it is extremely valuable -and- reliable. $10/year for all the calculators is reasonable, and I use it at least several times a week. By reliable I mean that the -site- says calculated numbers should be within 10% of measured, and I have usually seen it around 5% and never over 10. That's pretty cool. There are other online calculator. I've tried a few and they've usually been to convoluted or limited or uncomfortable to use. Nope I'm not a shill and I gain no $ from the site for writing this, I simply find it spectacularly valuable.
Great info. I use the old Scorpion Calc and the prop charts for the Cobra and Scorpion motors at: http://www.innov8tivedesigns.com/
They do extensive testing with each motor and each prop on a thrust stand/dyno. I've found that if you have any motor and know the stator dimensions and kv you can use these tools to get a good handle on thrust and load.