# Bp series propeller chart

Discussion in 'Props' started by Laranjo123, Oct 21, 2011.

1. ### Laranjo123Previous Member

Hello gudday sirs. Where can i find a bp series propeller chart?. Cause mine is very blured?

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3. ### Laranjo123Previous Member

Sir sorry to ask such question but how do i read this graphs....? i have bp=69.15

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### jehardimanSenior Member

I don't understand why you would want to use a Bp-Delta chart instead of calculating Kt Kq directly for any wheel. If you have Bp based upon installed power and desired speed, then you will have to check several of the charts to get the best fit blade number and size. By calculating directly you can get a more optimum prop. You already have all the data you need (i.e. torque, rpm and speed) to start optimization.

Anyway, here is a source of Bp-Delta charts for some wheels. With the Kt, Kq data above you could develop your own charts.

http://hem.bredband.net/lagaren/props.htm

So was your question on how to use a Bp-Delta chart or how to convert Kt,Kq and J data to Bp-Delta?

5. ### Laranjo123Previous Member

I want to know the delta, pitch ratio and the efficiency using the bp. I don't know how to use the BP chart it's my first time to use this...

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Dear,

You can find the method to D.Gerr "Propeller Handbook" Chapter 6 p.66-82.
There is an extended and popular breakdown of Bp-δ method.

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### jehardimanSenior Member

Enter your chart with your Bp accross the bottom. Go up your Bp line until you reach the maximum eta (efficency), it is usually marked as a line that curves down left-to-right through the eta curves (think of the eta curves like a topographical map, you want to be on the highest point you can). Use this point to read off your delta (the curves that sweep down from right-to-left) and your pitch ratio (left axis).

I will tell you right now that your Bp is too high for good efficency. Are you using the wake reduced Va? And if so, you should consider increasing the reduction in your gearset. Increasing reduction will make the prop larger and increase the pitch ratio.

8. ### Laranjo123Previous Member

Yes i did use of that wake..What will happen if i still continue?...

9. ### Laranjo123Previous Member

Sir what chart which is which? What B do i have to use?...Btw how many blades are involve in this chart?.....

10. ### Laranjo123Previous Member

Sir i would like to know which is the ( efficiency , delta, MWR, BTF )
The yellow = pitch ratio
the cyan = my BP somewhere there
the violet = bp ranges
red =?
blue ? ( is it the eta? )
red =?
green =?

11. ### Laranjo123Previous Member

Mr.Adler i don't have that book do you own one? Do you mind could you share it to me?...Please

12. ### Laranjo123Previous Member

Any help people just tell me what B chart do i need and what particular name does those color stands for.?..

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### AntteyJunior Member

Now quite the similar topic here. I am at the diameter determining stage. The series is Wageningen.But first I'm suppose to determine the blade number so that I could proceed to Bp-delta chart. I'm asked to determine it from the simmilar type of yachts I'm working on..

Would anyone suggest me the number of blades for a twin screw motor yacht?
L=26.17
B=6.96
T= 1.22
Cb= 0.46
for 30knots iv around 3000HP per screw.

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### daiquiriEngineering and Design

Start with the lowest number of blades commercially available, find the optimum prop and then perform the cavitation check. If cavitation is predicted, increase the number of blades. Repeat the process until the cavitation check returns an acceptable value.
Cheers

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### AntteyJunior Member

Thank you.
Cheers

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