On Nov 19, 10:13*pm, Bruce wrote:
On Fri, 19 Nov 2010 23:34:40 +0000, Justin C





wrote:
In article , Wayne.B wrote:
On Wed, 17 Nov 2010 08:28:04 -0800 (PST), Joe
wrote:

Do you plan to use the captured energy to supply house loads or to use
it as recharge/propulsion when the wind dies?- Hide quoted text -

- Show quoted text -

Both would be the goal.....zero emissions. They have some very good
re-generative systems and nickel-metal hydride and lithium-ion
batteries. The boat would have plenty of room for some huge battery
banks.

You could probably supply house loads with just solar panels and/or
wind generators. * However I'm a bit skeptical about standby
propulsion regardless of battery banks size. * By the time you drag
props that are big enough to capture significant power, you'd be
adding enough drag to considerably slow the boat. *On the other hand
if you are just looking for talking points in a marketing plan, what
the heck.

quote
* *The GREEN MOTION system eliminates fossil fuel used by sailing
yachts in any way. Electrical energy is generated with the system and is
stored in batteries (lithium Iron Phosphate are optional). It will
generate sufficient energy to be used for propulsion, hot water, cooking
and all electrical equipment and navigation on board. When batteries are
fully charged or high speed is required (race) the lifted Motogens
eliminate the drag from the propulsion system and this increases the
speed of the yacht (between 5 - 15%).

* *Retractable Motogen
* *The electric retractable Motogen is new, light
weight, extremely efficient and better than any propulsion system ever
designed for yachts. Usable in all sailing yachts from 30 to 90 ft (9-30
m): monohull, catamaran or trimaran). Installation can be made inside
the hull in a monohull or on a retractable arm for multihull. 5 years of
extensive testing has been done with a ‘proof of concept’ sailing in
excess of 10.000 Nm.
/quote

URL:http://www.green-motion.com/

OK, it's a cat, and not up to Joe's cargo work, but some of the
technology must transfer. I don't fancy the cost of those li-ion
batteries though... but they do handle huge charging loads, charge
quickly, and deliver their full capacity, not just a small percentage of
it.

The idea of a boat that needs no fuel of any kind, other than that
required to sustain the crew, does appeal. No diesel for *anything*. I'm
sure that there are some cruisers out there who would find the cost of
one of these cats a whole lot cheaper when they factor in their diesel
usage over a few years.

* Justin.

I suspect that the estimates of *drag versus speed for the generator
propeller is highly optimistic. The best estimates I can find are that
the drag from a 3 bladed prop reduces speed by about 15%, not the 5 -
15% mentioned.

My own experience changing from a three bladed feathering prop to a
three bladed fixed pitch prop was that the speed reduction was
certainly very noticable.

Fromr one sourcehttp://www.ipoa.org.uk/?p=180(unknown provenance):

quote:
The drag of a propeller is not easy to quantify but some
generalisations are in order such as,

The drag effect increases with speed – actually it increases with
the square of the speed, so faster hulls are penalised much more than
slower ones.

This is true. You chain a single shaft on a quad screw crewboat you
drop from 25kts to 11kts.

The average sailing speed is reduced by about 15% by the drag of a 3
bladed propeller of a size suited to propel a particular hull. When
there is a strong wind there is often sufficient power from the sails
to overcome the drag of the propeller and hull speed is achieved.

I think thats right on for a sailing vessel, around 15% for any
displacement hull, easy to overcome with sail.

As
the wind drops, the drag of the propeller becomes more significant and
in light winds it can seriously reduce sailing speed.


unquote:

If you want to spend a couple of bucks here is what appears to be a
peer reviewed *indipendent study on the effects of props on drag
fromOcean Engineering, Volume 35, Issue 1, January 2008, Pages 28-40

/2008&_rdoc=1&_fmt=high&_orig=search&_origin=search &_sort=d&_docanchor=&vie*w=c&_acct=C000050221&_ver sion=1&_urlVersion=0&_userid=10&md5=a7ab84dce94c50 *24bf9bc438d2397827&searchtype=a

The abstract says:

All but the smallest classes of modern keelboats are fitted with
inboard engines and consequently, when making way under sail, the
craft experience parasitic drag due to trailing propellers and
associated appendages. The variety of screw configurations used on
sailing boats includes fixed-blade, feathering, and folding set-ups,
with blades numbering two or three. Although the magnitude of the
resultant drag is thought to have a significant influence on sailing
performance, the published literature having regard to this problem is
sparse. Here, the aim was to evaluate the drag effect of fixed-blade
propellers of types commonly used on sailing craft. The results of
towing tank tests on full-scale propellers are presented for the
locked shaft condition; these are presented along with reconfigured
data from the few previously published sources. For the case in which
the propeller is allowed to rotate, tests were conducted on a typical
screw with a range of braking torques being applied. It was
hypothesised that the performance coefficients of the Wageningen
B-Screw Series could be used to characterise adequately the types of
screw of interest and that these could be extrapolated to enable
prediction of the drag of a freewheeling propeller; an assessment of
this formed part of the investigation.

Cheers,

Bruce- Hide quoted text -

- Show quoted text -

Do they mention the difference from a chained shaft to a free
wheeling prop. I've heard a chained non turing prop provides less
drag.

Joe