Coefficient of Thrust Calculations......Urgent help please!

[Biomechanist]

We are trying to calculate the thrust produced by the propeller. We have everything except a chart that somehow gives us the value of coefficient of thrust (Cd)....we are trying to find charts which correlate this coefficent with other values of propeller. I have tried to research to look for charts...but I couldn't. All our calculations are on hault because of this....so if someone knows any site, please do let me know.

thanks
Biomechanist.

[dougfrolich]

I don't know about the "coefficient of thrust" you are talking about, but for estimating thrust as it relates to static ballard pull I use:

Pull in Lbs.= 62.72 x ( Shaft HP x Diameter/12)^.67

from the Propeller Handbook

or for typical conditions

Thrust in pounds = (326 x Shaft HP x Propeller Efficiency ) / Speed of water at Propeller


A chart for approximations of propeller efficiency can be found on page 58 of the Propeller Handbook by Dave Gerr.

Hope this helps

[waterman]

look in the P.N.A. (principle of naval architecture) vol 2. The notation symbol for the thrust co-efficient is Kt. Look on page 145. You can buy the PNA at the SNAME website. Also, check Dave Gerrs book as well. It is cheaper, and very easy to read.

[CDBarry]

Actually, for boat propellers, you need to use the Blount Hubble coefficients. The coefficients in PNA and Gerrs book are for Troost props, which are a bit different. You also need to match engine torque with the prop. If this is a serious matter with money at stake, you should contact a naval architect, perhaps Elliott Bay Design Group in Seattle because there are other pitfalls. It is a short, quick job for an experienced NA.

I am doing an online course starting shortly through E Marine if you want to learn how to do propellers in general. The course includes various prop programs and spreadsheets.

[nevd]

Hello Chris,

How do I get more info on this course?

Thanks,

nevd

[CDBarry]

http://www.emarinetraining.com/pages/1/index.htm

The date listed is not correct. It was delayed due to IBEX and hasn't started yet.

[FAST FRED]

If you only need a simple rulle of thumb , one gallon of diesel will create 16 to about 20 hp .

Each HP can produce about 20 lbs of push with about 25 possable if you crank all the numbers well .

On most boats the 3 rd or 4th prop "is the one".

No Engineer!

FAST FRED

[dougfrolich]

Chris,

When does your course start, I would be interested in it if I am in town.

Thanks