Bertram31.com General Bulletin Board

Re: Cummins 370's or 330's?

Posted By: jp
Date: Wednesday, 22 February 2006, at 9:23 p.m.

In Response To: Re: Cummins 370's or 330's? (J.J. Soares)

Prop Pockets,
Wow there's a topic. Hatteras and Viking have gone with pockets to reduce drafts back to the 6ft number on the big boats. Apparently 6ft is the magic number for the Bahamas and other out island marinas.
The use of 5 blade props becomes needed because you can't swing the right diameter wheel due to clearance issues. So add a blade a add some pitch and try to stream line the struts to reduce cavitational errosion.
If you've ever run a boat with pockets its a real experience. The (viking)pocket boats have a tendancy to take in air if they are over tabbed and the noise and shutter from cavitation is like running over a grizzly bear. The same thing happens if the boat becomes off level (heals over) due to sea conditions at cruise. If your not ready for it it will jump you right out of the helm seat and make you start checking gauges and wiping your butt.
Don't let people tell you only pocket boats burn props. Most of the boats that don't have the clearance for large diameter wheels are forced to add a blade and compensate with pitch, this equals prop burn. I've been on vikings and a Bertram that burned wheels these boats had no pockets.
My guess with the B31 cavitation with pockets is all those lifting strakes in front of the pockets channel air. Shave the strakes, lower the boat get the pockets into clean water. Maybe after the next powerball.
Good Luck

KR
JP

Messages In This Thread

Cummins 370's or 330's?
J.J. Soares -- Wednesday, 22 February 2006, at 6:29 p.m.

Re: Cummins 370's or 330's?
Al -- Wednesday, 22 February 2006, at 6:43 p.m.

Re: Cummins 370's or 330's?
Harv -- Wednesday, 22 February 2006, at 6:46 p.m.

Re: Cummins 370's or 330's?
bruce -- Wednesday, 22 February 2006, at 6:52 p.m.

Re: Cummins 370's or 330's?
mike ohlstein -- Wednesday, 22 February 2006, at 7:05 p.m.

Re: Cummins 370's or 330's?
bruce -- Wednesday, 22 February 2006, at 7:13 p.m.

Re: Cummins 370's or 330's?
mike ohlstein -- Wednesday, 22 February 2006, at 11:37 p.m.

Re: Cummins 370's or 330's?
jp -- Wednesday, 22 February 2006, at 6:52 p.m.

Re: Cummins 370's or 330's?
J.J. Soares -- Wednesday, 22 February 2006, at 7:52 p.m.

Re: Cummins 370's or 330's?
bruce -- Wednesday, 22 February 2006, at 8:36 p.m.

Re: Cummins 370's or 330's?
jp -- Wednesday, 22 February 2006, at 9:23 p.m.

Re: Cummins 370's or 330's?
Vic Roy -- Wednesday, 22 February 2006, at 9:51 p.m.

Re: Cummins 370's or 330's?
JPH -- Wednesday, 22 February 2006, at 9:45 p.m.

Re: Cummins 370's or 330's?
Fishmonger -- Thursday, 23 February 2006, at 8:14 a.m.

Re: Cummins 370's or 330's?
JPH -- Thursday, 23 February 2006, at 12:53 p.m.

Re: Cummins 370's or 330's?
Capt. Dave Kosh -- Thursday, 23 February 2006, at 1:06 p.m.

Patnovic's B31 @ 46 mph *LINK*
zerocavity -- Thursday, 23 February 2006, at 2:10 p.m.

Re: Patnovic's B31 @ 46 mph
bruce -- Thursday, 23 February 2006, at 2:26 p.m.

Re: Patnovic's B31 @ 46 mph
Wayne -- Thursday, 23 February 2006, at 4:02 p.m.

Re: Patnovic's B31 @ 46 mph
randall -- Thursday, 23 February 2006, at 6:09 p.m.

Re: Patnovic's B31 @ 46 mph
Capt. Mitch -- Thursday, 23 February 2006, at 7:12 p.m.

Re: Patnovic's B31 @ 46 mph
Walter Kaprielian -- Thursday, 23 February 2006, at 8:21 p.m.

Re: Patnovic's B31 @ 46 mph
Doug LeBlanc -- Friday, 24 February 2006, at 9:50 a.m.

Re: Patnovic's B31 @ 46 mph
Walter Kaprielian -- Friday, 24 February 2006, at 10:59 a.m.

Re: Patnovic's B31 @ 46 mph
Harv -- Friday, 24 February 2006, at 11:46 a.m.

Re: Patnovic's B31 @ 46 mph
randall -- Friday, 24 February 2006, at 1:21 p.m.

Re: Patnovic's B31 @ 46 mph
Wayne -- Thursday, 23 February 2006, at 9:30 p.m.

Re: Cummins 370's or 330's?
JK -- Thursday, 23 February 2006, at 8:31 p.m.

Re: Cummins 370's or 330's?
bruce -- Friday, 24 February 2006, at 6:42 a.m.

Re: Cummins 370's or 330's?
J.J. -- Friday, 24 February 2006, at 7:57 a.m.

Re: Cummins 370's or 330's?
Walter Kaprielian -- Friday, 24 February 2006, at 11:05 a.m.

Re: Cummins 370's or 330's?
Rocket -- Friday, 24 February 2006, at 1:02 p.m.

Slow speeds w/300hp
JK -- Friday, 24 February 2006, at 9:59 p.m.