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Old 24 August 2007, 15:20   #1
Country: UK - England
Town: Enfield/Switzerland
Boat name: Zonneschijn II/Vixen
Make: Shakespeare/Avon
Length: 7m +
Engine: Evin' 175 DI /Yam 90
MMSI: 235055605
Join Date: May 2006
Posts: 1,425
New prop calcs

To stop hijacking Andys' build thread

Originally Posted by DGR View Post
Who's doing the calcs? I always thought that prop selection was a bit of a black art - there are so many variables that the best way is to just try one!!

Powertech marine. I'm sure it is a black art, but they said if they know top revs being achieved and a rough top speed, and prop size, they can work out the best way to go. We'll see.

Neil Harvey is offline   Reply With Quote
Old 24 August 2007, 16:01   #2
Country: UK - Wales
Town: Barmouth
Boat name: Blue Marlin
Make: Ribcraft
Length: 7m +
Engine: Yanmar 315/Bravo 2X
MMSI: 235020218
Join Date: Jun 2003
Posts: 827
OK - well it will be interesting to see how good they are at predicting performance. The number of variables involved would stump most models.

The usual assumption is that adding 1" pitch looses 2-300 rpm but adds 2-3 knots of top end speed (if it can get you there) - but that can go horribly wrong. And that's if you stick wth the same types of prop that you already have - not to mention 4-bladed, 5-bladed, duo props...etc, etc...

However, the weather has been reliable lately...
DGR is offline   Reply With Quote

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