[PCW] A few things

[Malcolm Tennant]

Jim Meander.

I would like to comment on some of your questions:-

[3] Trash compactors need power to operate them, they aren't cheap [the 
probable reason for their absence] and they take up space. We have used them 
on a lot of our designs.

[4] Most propellers are in fact variable pitch, the pitch changes from the 
root to the tip. I presume what you mean is CP [controllable pitch] 
propellers. There are dozens of companies manufacturing these and there are 
thousands in use. Several of our designs have used CP propellers. However 
they are very expensive and you have to do big miles to justify their cost.

[5] All of our designs feature propeller shafts that are parallel to the 
waterline and that direct their thrust directly aft. It is one of the 
reasons why our CS hull is currently the most efficient around.

[6] It is a good idea but until recently the technology was not available in 
small enough sizes for use in most pleasure boats. Ships, and in particular, 
cruise liners and war ships have used diesel/gas turbine-electric systems 
for decades. There are now a number of manufactures of diesel electric 
systems and a large amount of published data and comment. Professional 
Boatbuilder magazine has had two articles in its most recent publications 
looking at the pros and cons of such systems and their applications to 
pleasure boats.

[7] There are a number of designs, and hundreds of patents, in operation 
using exactly what you are proposing. Just the exhaust is not enough so 
extra air is required. This takes power and is generally applied to high 
speed [planing] craft. There is a system that injects the exhaust into a 
cavity above surface piercing propellers so that they are operating 
semi-submerged right from the word go.

Regards,

Malcolm Tennant.   ARINA  MA

MALCOLM TENNANT MULTIHULL DESIGN LTD
PO Box 60513, Titirangi.
Waitakere 0642
NEW ZEALAND
Ph: +64 9 817 1988
e-mail: malcolm at tennantdesign.co.nz
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