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Propeller shape


sparrowcycles

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Hi folks, I have just picked up a bargain propeller which I might try on Prince soon, it's a different shape to most propellers I've seen and it got me thinking about the merits of different prop designs..

 

Does anyone have any pearls of wisdom regarding this particular one?

 

Thanks!

IMG_20200525_145144.jpg

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51 minutes ago, sparrowcycles said:

Interesting. Can I ask what a turbine prop is normally used for, advantages and disadvantages etc.

 

Sorry, it's a whole new world to me!

Its used for just about every thing on displacement boats. A high speed boat might use an equipoise prop which has a very different shape to yours. There are weed slinger props that are less efficient and are shaped to throw weed off when in ahead. Then there are a number of "patent" prop shapes for which certain advantages are claimed but often to the detriment of other performance. Finally there are a load of folding and variable seed props that are certainly not suitable for canal use.

Edited by Tony Brooks
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It does look like someone has ground the tips off, I very much doubt that it will make any discernible difference to its performance. Propellers have plenty of compromises in their design, they have to work at a whole range of speeds and in two directions so a bit of trimming should be OK.

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Thanks everyone, I guess I was wondering specifically about the blade shape in that all the props I've seen on narrowboats so far have the bulk of the blade at the outer edge (ie each blade looks something like a teardrop with its pointy end at the centre of the prop)

But this one seems to have the widest part of the blade right by the hub and then tapers out towards the blade ends. 

 

Does this design make any difference? 

 

S

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20 minutes ago, sparrowcycles said:

Thanks everyone, I guess I was wondering specifically about the blade shape in that all the props I've seen on narrowboats so far have the bulk of the blade at the outer edge (ie each blade looks something like a teardrop with its pointy end at the centre of the prop)

But this one seems to have the widest part of the blade right by the hub and then tapers out towards the blade ends. 

 

Does this design make any difference? 

 

S

 

Presumably it is marked with its size (normally on the 'centre'), you can then ,measure it to see if it is the size it says it is, or, if it has been re-shaped. If it is the stated size, it is some unusual blade design

 

Something like this :

 

20191011_090142.jpg

Edited by Alan de Enfield
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