HydroComp, Inc. > Knowledgebase and software help desk > Knowledgebase

Search Knowledgebase:

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.

Was this article helpful? yes / no

Related articles

Contra-rotating stern-drive propellers
Propeller tunnels
Sizing tunnel thrusters
Bow thrusters
Simple propeller analysis

Article details

Article ID: 33
Category: NavCad
Date added: 2015-07-02 15:11:21
Views: 344
Rating (Votes): Article rated 3.1/5.0 (17)

Copyright © 2019 HydroComp, Inc. All rights reserved. http://knowledgebase.hydrocompinc.com/

« Go back

Powered by Help Desk Software HESK, brought to you by SysAid