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July 2, 2015


Under-hull boat drive systems



I read the article about contra-rotating stern-drive propellers. Is this information applicable to under-hull boat drive systems?

Almost everything can be applied as written to the recently introduced under-hull drive systems, such as the Volvo IPS or CMD Zeus. However, there is one aspect for which I would suggest different figures – the hull-propulsor coefficients.

The following are typical values that can be used for an under-hull tractor unit (e.g., IPS):

   Wake fraction = 0.00
   Thrust deduction = 0.03

And these are typical for an under-hull pusher unit (e.g., Zeus):

   Wake fraction = 0.06
   Thrust deduction = 0.05

If the drives are put into a tunnel, then you would expect a reduction in wake fraction and an increase in thrust deduction. Relative-rotative efficiency is also likely to be reduced in a tunnel.

 
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Article details

Article ID: 33
Category: NavCad
Date added: 2015-07-02 16:11:21
Views: 166
Rating (Votes): Article rated 3.0/5.0 (10)

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