HP to WATT to THRUST

[John David]

CDBarry----
Thanks for info. I am way past the "matching" phase. I have built a racing hydro and have purchased a custom made prop that is allegedly specificaly for the class of boat and the engine I am using.I am now trying to predict the performance of the boat.
I believe that if I could get efficiency vs speed, my prediction inputs will be complete.
(by the way, "complete" is not neccessarily the same as "accurate")
What is Blount-Hubble,an algorithm?, a text book? authors of a paper? In any event how do I get a hold of it to use. Is it in the form of General Propeller charts as were used for aircraft props. Any help pointing me in the right direction is appreciated

[CDBarry]

For a hydro you need Radojc's algorithm.

Check out PSOP at SNAME, and in the papers section for both references.

[yipster]

if we are dealing with a fluid (liquid or gas) and particularly if we are dealing with a moving fluid, keeping track of the mass gets tricky

dont know why i'm on http://www.grc.nasa.gov/WWW/K-12/airplane/thrsteq.html again, trying to keep up i guess

[RANCHI OTTO]

ETA0 ... ok! But what about ETAR and ETAH ?

RANCHI Otto

[yipster]

ok, propeller efficency is "ETA" and not "Estimated Time of Arival"
what the abriviation stand for i have to check, like ETAO, ETAR and ETAH
Geez, not so easy to learn something bout thrust...

[RANCHI OTTO]

It is not a question of abbreviation but I want only say that the thrust needed from a boat to reach a speed is not only prop's efficiency.
The values of prop's efficiency derivated from cavitation tunnel tests are theoretical because the propeller has to produce thrust behind a body (ETAR) and the speed of the boat is not the same as the speed of the water at propeller (1-w) and so on....
This was my thougth Yipster... only this....

RANCHI Otto

[yipster]

thanks for clearing these wonderings, i find "thrust" rather interesting but complicated