[PCW] 20' cat

[by way of Georgs Kolesnikovs]

From: "East Cape Marine Ltd" <tech@nzboatbuilders.com>


Hello David,

Sounds like what they call "Porpoising"

Without seeing all the details on the actual design:  I am only able 
to offer a place for you to start looking for the potential problems, 
in any catamaran set-up.

1. Check to see if the  LCB and LCG are too far apart in the design. 
(If possible)  They should be no further than 75 - 100mm Maximum 
distance between the two at any speed and trim. The closer the better.
2. Weight, such as driver, tanks and other gear could be moved to see 
if the attitude of the vessel changes at different speeds and trim. 
This will have effects on moving the LCB closer, or further away, 
from the LCG. ( start by adding weight aft, or removing weight 
forward.)
3. Asymmetric hulls with air vents may have an adverse effect on a 
design under 26 feet if the weight in the vessel is set-up 
incorrectly.
4. Once the above is cured, try a jack plate for the engine.


This is by no way an opinion or criticism on the actual design of the 
catamaran in question.

All the best,

Noah Thompson
Director / Designer
East Cape Marine Ltd.

Design / CNC  Facility:
Unit 4 / 5 Reynolds Place
Papamoa Beach
Tauranga 3118

Mail:
Po Box 705
Te Puke
New Zealand 3153

Phone: +64 7 542 5175
Fax: +64 7 542 5176
Mobile: 021 11 00 984
info@eastcapemarine.com
www.eastcapemarine.com


----- Original Message ----- From: "david walker" <dwalker434@earthlink.net>
To: <power-catamaran@lists.samurai.com>
Sent: Friday, 25 May 2007 4:01
Subject: [SPAM] [PCW] 20' cat

>I just bought a new 20' single engine (150 e-tec) tunnel-hull 
>catamaran and have had nothing but surprises. I will not mention the 
>name hoping I get some resolution of the problems. This is my first 
>catamaran.