Propeller calculation

Hi guys,
I am newbie in this forum and also to the topic of efoils and therefore got a lot of questions.
How do you calculate/choose the perfect propeller for a given motor? For RC-builds it is quite common to do some try and error (those props are small and cheap) but how do you do it on an efoil?
Is there a program or an online calculator?

Try this

This is a very complex scientific procedure (rocket science, I’d say), which is why almost everyone here uses a proven commercial propeller for a given motor.

Trial and error works also here. Obviously Flite and FR props works fairly well on many combinations so usually a safe bet, but don’t overestimate the value of the theory side, for sure you only know after testing in practice.


One of the last here on the forum, who seems to have underestimated the “value of the theoretical side”, admits it here 3D-printed folding propeller - #83 by Seaman by evaluating his new DIY propeller by saying “160mm size seems overloading my engine …”

A few days earlier, a forum member who had a propeller made on a high quality commercial CNC mill privately admitted to me that the propeller was not working. So even this trial and error method failed.

Many, many trial-and-error methods have been done over the lifetime of this forum, but to date, not one has outperformed the Flite propeller or the FR propeller. So, logically speaking, all trial-and-error methods to date have failed. And the same seems to be true for wings.

I recall the creator of FR propeller mentioned somewhere he had made 30 various( or something like that) different propellers and tested them in PRACTICE before he found out the best model so far. It is not just something You can just calculate behind the keyboard in theory …

Obviously You don’t start from zero each time and obviously there is well known theoretical background also, still result from field testing might differ from what can be expected in theory.

My preferred prop differs significantly from the FR prop.
Bigger, more pressure and tailored to 6s Lipo …
Of danger, please do not make such general theses, dynamics!!

There are few trial and error propellers that were working good. Not super great. Some of the users gave their models for other people and they were working very good. Yes, no1 practically outperforms Flite or FR stuff but where u got information that both FR and Flite didn’t go with trial and error technique? U saying they got their props straight out of theory and working “flawlessly” without at least few dosen props before “final version”?