[PCW] MCAT 88

[Malcolm Tennant]

Dear Brian,

Thank you for forwarding John Winters comments on the MCAT 88. I 
certainly agree with his comments on the MCAT 88 but there are a 
couple of comments that he makes about the Pacific Harmony that need 
clarifying.  He says "I have since learned [28 knots] are a little 
out of reach on canoe body pure displacement hulls of most 
lengths".If this is what he has been told then it  is incorrect. If 
john goes to our web site he will see the 1992 design Red Diamond II. 
This 17.5m Loa design used our typical CS hull form and did a 
certified [by NKK the Japanese classification Society] 31.5 knots 
over the measured mile using  450hp per side. 30 knots can be 
achieved relatively easily by a pure displacement power cat with a CS 
hull.

It also needs to be recognized that the "super skinny" hulls of the 
Pacific Harmony are not a function of the original design but were 
caused by the increasing of the LOA from the original designs 72' to 
the final 86' without increasing the hull beam. This resulted in a 
hull beam of around 1.4m/4' 6" [depending on where you measured it] 
whereas if it had been designed from scratch to be 86' it would have 
been at least 1.8m/ 6' in beam. So any problems ascribed to the 
ultafine hulls are actually attributable to the increase in length 
rather than the basic design. We certainly do not usually use such an 
extreme fineness ratio as all our data indicates that it is just as 
counter productive as making the hulls too wide. We have yet to see 
any published, and certified, data that indicates that there are 
currently any better [fuel use wise] hull forms than our optimised CS 
shape over the speed range where our designs usually operate [see 
graph concerning fuel consumption on our web site].

The 22m x 10m current design previously mentioned  has island berths 
with all the [4] cabins located up in the wing.

Regards,

Malcolm.

MALCOLM TENNANT MULTIHULL DESIGN LTD
PO Box 60513, Titirangi.
Waitakere 0642
NEW ZEALAND
Ph: +64 9 817 1988
e-mail: <mailto:malcolm at tennantdesign.co.nz>malcolm at tennantdesign.co.nz
<http://www.tennantdesign.co.nz>www.tennantdesign.co.nz
<http://www.catdesigners.com>www.catdesigners.com