# Bp delta charts and selecting the right propeller

Discussion in 'Boat Design' started by Toothbrush, Nov 13, 2017.

1. Joined: Nov 2017
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Location: Finland

### ToothbrushNew Member

Hi!

I'm trying to calculate proper propellers for twin screw vessel using the Wageningen B Screw Series data (it's essential part of my thesis). I have made calculations using Bp delta method wich is presented in the Propeller Handbook. My problem is that I actually don't understand how I can use the Wageningen B Screw Series data when trying to find the most suitable propellers for my vessel. So my questions are:
1. What is the Wageningen B Screw Series data?
2. What are the differences between screw serieses (B4, B5 etc.)?
3. Can I use B series data for ducted propellers?
4. Where can I find (and buy) propellers that match the Wageningen B Screw series?
5. Is there other serieses than B series and how they differ from B series?

English is not my first language but I suppose you understand what I'm trying to ask here. I have no problem to perform calculations or read the Bp delta charts but I have no idea what Bp delta charts to use and why to use certain Bp delta chart.

2. Joined: Feb 2015
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Location: Athens, Greece

### vkstratisMarine Designer

The B Screw (Troost) propeller series, as any other propeller series, is a set of propellers with a range of characteristics such as P/D ratio, EAR and number of blades tested by a research institution or university. These propeller series usually represent a "class" of commercially available propellers, thus a designer can use the test results to match a propeller for a commercial application. Results are in the form of curves presenting efficiency, thrust and torque coefficients against a load coefficient for different P/D, EAR and number of blades. The designer's goal is to find the propeller with the maximum efficiency to match the required load considering some cavitation criteria. This can be done graphically using the graphs or numerically using the published polynomial expressions of the the series tests. Besides the B-Series, there are several other published propeller series such as the Gawn, Kaplan, SP series. You will have to check your application requirements to choose a series that matches the needed geometry characteristics.

Some papers you can read on the subject:

Markussen, P.A., "On the Optimum Wageningen B-Series Propeller Problem with Cavitation Limiting
Restraint", Journal of Ship Research, Vol. 23, No. 2, June 1979.

Markussen, P.A., "On the Optimum Wageningen B-Series Propeller Problem with Cavitation Limiting
Restraint", Journal of Ship Research, Vol. 23, No. 2, June 1979.

Blount, D.L. and Hubble, E.N., "Sizing Segmental Section Commercially Available
Propellers for Small Craft", SNAME Propeller Symposium, 1981.

Oosterveld, M.W.C., "Wake Adapted Ducted Propellers", Netherlands Ship Model
Basin, Publication No. 345, 1970.

If you are dealing with a semi-planing or planing boat, you can check my little software (quickPlaning - www.boatdesignlab.com). quickPlaning will estimate boat's resistance and match a Gawn series propeller for specified condition, and engine characteristics.

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3. Joined: Nov 2017
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Location: Finland

### ToothbrushNew Member

Thank you SO much for this information! Now I actually have a chance knowing what I'm doing. Most books refer to Wageningen B series when calculating fixed screw propellers so I just might stick to it with my own calculations as well. It's good to know there are other published propeller serieses as well.

EDIT: I have one question though. If I use Wageningen B series data and choose, say B4-40 series propeller, how can I know what are the common diameters and disc area ratios for this specific series? Or do I need to consult various manufacturers about their propeller dimensions?

Last edited: Nov 14, 2017

4. Joined: Feb 2015
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Location: Athens, Greece

### vkstratisMarine Designer

You will calculate the optimum propeller for your application using the charts and then consult manufacturers' catalogs for a propeller that comes as close as it gets to your calculated sizing parameters. If there is no such propeller or it is financially unfeasible you will have to go back to your calculations and refine them.

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