Looking forward to actually buying a cat soon. Have been doing a lot of
reading and have some basic questions to ask of this knowledge base.

1. Have the new "high pressure electronic controlled diesel fuel rail"
   installations proved themselves. I.e. are the new diesel engines equal
   in reliability to the older mechanical diesel engines

2. Once the newness of your dream boat wares off, does fuel economy or
   get where you're going dominate your thoughts. Let's say two type of
   usage 1. On your boat more than 2-3 weeks at a time and/or extended
   weekend typical usage.

3. Most boats do not include a trash compactor, given the limited space
   on a boat and trash a fact of life I would think it would be a great
   item to have.

4. Technology and innovation being what it is today, why do we still
   only have fixed pitched props, where is the variable pitch props?

5. Stern drives, I fully understand the maintenance issues, but with
   the Volvo sea drives and the performance benefits, it seem to be worth
   the trade off. Pushing water downward and back is not as efficient as
   just pushing the water straight back. Is this more resistance to change
   i.e. the old diesels versus the new diesels ?

6. The concept of a stationary diesel running all the boats electrical
   and providing power to electric motors to drive the props seems like a
   good idea. Trains have used this technology for years why not boats. I
   am sure there would be a size minimum for this to work.

7. Old old idea, but. Why not create a say two inch false bottom with
   thousands of small holes in it and the exhaust fed into this space. Net
   effect under power less total water contact, therefore less drag better
   fuel economy.

Oh well sometimes we need to think out of the box, sometimes were better
off not thinking.

Jim Meader

RE/MAX Today

VM  650-610-6455

Fax  650-591-1043

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@tennantdesign.co.nz
www.tennantdesign.co.nz
www.catdesigners.com

Will do more searching on controlled pitch props and the forced air hull
cavity concepts.

Thanks for sharing your knowledge and answering my questions so well.

Jim Meader
RE/MAX Today
VM  650-610-6455
Fax  650-591-1043

-----Original Message-----
From: power-catamaran-bounces@lists.samurai.com
[mailto:power-catamaran-bounces@lists.samurai.com] On Behalf Of Malcolm
Tennant
Sent: Tuesday, August 28, 2007 5:07 PM
To: Power Catamaran List
Subject: Re: [PCW] A few things

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@tennantdesign.co.nz
www.tennantdesign.co.nz
www.catdesigners.com

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