Dear all,

What would be the impact of a projected planning cat hull if we set up
engines for lower speeds? Is there loss of efficiency? Confort? Any
other points?

Roger

Roger Jacob.

Dear Mr. Jacob,

The result could be an unmitigated disaster economy wise. If you go to my
web site and look under latest news on the right hand side you will see,
when you scroll down, some [not so recent] news for April 2004. This shows a
graph of fuel consumption at various speeds for different types of catamaran
hull forms. Depending on exactly how fast you want to go, you could be using
some 5 to 10 times as much fuel as compared with a CS hull form. If you are
travelling at a speed that is  right on the resistance "hump" then you will
also be pulling the biggest quarter wave your fellow boaters have ever seen,
or experienced!

Planning hulls are designed to travel efficiently at planning speeds, not
displacement speeds. So why would you travel at a speed where they were
never going to be economical regardless of what horsepower you use.

Regards,

Malcolm Tennant.

Malcolm Tennant Multihull Design Ltd
PO Box 60513 Titirangi,
Waitakere 0642
NEW ZEALAND

ph +64 9 817 1988
fax +64 9 817 6080

e-mail malcolm@tennantdesign.co.nz
www.tennantdesign.co.nz
www.catdesigners.com