On Wed, 28 Mar 2007 15:13:47 -0400, Jeff wrote:

The engines and performance is no problem, at 5 knots the boat is only
being pushed to half of hull speed,

Catamarrans do not have a hull speed in a conventional sense because
of the long narrow shape, and are thus easily driven in flat water
conditions. The only way they could run at night however is to have a
large power surplus during the day which seems unlikely in typical
ocean conditions.

* Wayne.B wrote, On 3/28/2007 4:46 PM:
On Wed, 28 Mar 2007 15:13:47 -0400, Jeff wrote:

The engines and performance is no problem, at 5 knots the boat is only
being pushed to half of hull speed,

Catamarrans do not have a hull speed in a conventional sense because
of the long narrow shape, and are thus easily driven in flat water
conditions.

I appreciate that, but the hull speed can still be computed. In fact,
the power/speed curves will still show a bump at hull speed, it just
isn't as noticeable. but more important for this case, the required
power formula works pretty well, especially at speed ratios less than 1.


The only way they could run at night however is to have a
large power surplus during the day which seems unlikely in typical
ocean conditions.

Yes, I'm wondering if their poor daily runs were caused by running out
of juice at night.

"Jeff" wrote in message
. ..
* Wilbur Hubbard wrote, On 3/28/2007 1:17 PM:

wrote in message
oups.com...

The max rating of the engines is not the point: IF the panels
produced
10 kW for 12 hrs a day straight, and there was not much loss in
storage, they could run on 5 kW 24 hours, which is 8 hp, and could
work. (I guess...)


I can tell you aren't overly familiar with photovoltaics. 10KW
represents the max output when the sun is straight overhead and the
temp is mild That same 10KW array will produce perhaps 5K when the
sun is at a 45 degree angle and even less when the angle is less. The
total wattage output of a 10KW array is probably 50-60 KW on a good
sunny day, not 120KW per 24 hour day.

You can't run motors and charge batteries and run electonics with
that paltry output.

Something's fishy here...

Maybe if you washed your hands ???

The engines and performance is no problem, at 5 knots the boat is only
being pushed to half of hull speed, so the requirement is only around
4-5 kW. With the efficient hull shape it might only be 3 kW needed.
The batteries seem to be able to stash 50 kWh, so that's about 12+
hours worth. The solar output is the bigger problem - the theoretical
output of a 10kW panel at 18N in the winter is maybe 65 kW-hours, so
pushing the boat and charging the batteries would seem to be
problematical. However, this would not be too different from a
sailboat getting less than expected winds - it would just slow down a
bit.

The biggest issue I see is that the "weight" is listed as "ca. 12
tons" which is about double what a lightweight cat would weigh. My
cat, without the engines or sailing rig would only be about 8000
pounds. Its possible that the "weight" is really the admiralty
tonnage and the actual displacement is much less. This would affect
the power needed in a linear fashion, so if the Disp is only 12000
pounds, it could be driven with possibly as little as 2 kW or even
less.

The weight is a bit obscene. The battery bank alone must weigh at least
two tons.

Then there's the array. 100, 100 watt panels at 20lb each is a ton.
That's a ton on the roof so to speak. And it looks like the roof is made
out of 2X4s - more weight up high. Must do wonders for the stability
curve. Oh, excuse me, catamarans don't have a stability curve. It's more
like a stability square. Very good stability till it gets to 90 degrees
then it's over she goes to stay over forever.


One more item: although they talk about doing 5 knots, the log is
filled with entries showing speeds as low as 3.5 knots, and very few
days over 100 miles, even though they had a tailwind much of the time,
plus a quarter knot current in their favor. Thus, they may have only
been getting 3-3.5 knots worth of power from the system.

You must remember photovoltaics make almost no electricity if it's a
cloudy day. Certainly not enough to power electric motors strong enough
to power a vessel. The could improve that thing about 50% quite easily
by being able to tilt the roof so the array was always facing the sun.
If they were really smart they could shape it like a wing sail and get
solar and sail power at the same time. Just a thought.

Wilbur Hubbard

* Wilbur Hubbard wrote, On 3/28/2007 6:22 PM:
....

The weight is a bit obscene. The battery bank alone must weigh at least
two tons.

That seems a bit high. Plus, the motors are quite light and there's
no fuel tank. And how much does the rig and sails, plus other gear
for a sailboat weigh?


Then there's the array. 100, 100 watt panels at 20lb each is a ton.
That's a ton on the roof so to speak. And it looks like the roof is made
out of 2X4s - more weight up high. Must do wonders for the stability
curve. Oh, excuse me, catamarans don't have a stability curve. It's more
like a stability square. Very good stability till it gets to 90 degrees
then it's over she goes to stay over forever.

You keep saying that, but you seem to have trouble finding cases of
them going over.



One more item: although they talk about doing 5 knots, the log is
filled with entries showing speeds as low as 3.5 knots, and very few
days over 100 miles, even though they had a tailwind much of the time,
plus a quarter knot current in their favor. Thus, they may have only
been getting 3-3.5 knots worth of power from the system.

You must remember photovoltaics make almost no electricity if it's a
cloudy day. Certainly not enough to power electric motors strong enough
to power a vessel.

Actually, the new ones do better on cloudy days, but total output
seems to be the liming factor on this boat. I think its really
designed as a water taxi that would get a shore power charge every night.

The could improve that thing about 50% quite easily
by being able to tilt the roof so the array was always facing the sun.

They are at a low enough latitude so that that's not much of a factor
towards the side, and tipping fore and aft could be a problem.

If they were really smart they could shape it like a wing sail and get
solar and sail power at the same time. Just a thought.

If you could invent a sailcloth that functions as a solar panel, you'd
really have something!

* Gogarty wrote, On 3/29/2007 9:05 AM:
In article ,
says...
You keep saying that, but you seem to have trouble finding cases of
them going over.

There are many, some of them of very famous people in very famous round the
world races. It's why competition cats have an escape hatch in the bottom.
They trip on big waves when broaching and go all the way over --
permanently.

Competition boats are in a whole different category. You might just
as well say cars are dangerous because so many crash in a simply 200
mile race. Neal has frequently claimed that the fate of every
cruising cat is to capsize, when in fact its hard to find more than a
handful of cases.

If you could invent a sailcloth that functions as a solar panel, you'd
really have something!

I have no doubt that it will be done. One type of solar cell is an amorphous
crystal, meaning it is essentially glass. Modern high-tech sails are not
made from woven fabrics but laminated sheets. Could not one of those
laminates be amorphous solar cells?

Someday, and probably within 50 years.

"Jeff" wrote in message
...
over forever.

You keep saying that, but you seem to have trouble finding cases of
them going over.

I guess you have a short memory. I recall one washing up on the beach in
California upside down will all hands missing and most likely dead. It
washed up on the beach upside down. About a month or two ago.

Wilbur Hubbard

* Wilbur Hubbard wrote, On 3/29/2007 1:59 PM:

"Jeff" wrote in message
...
over forever.

You keep saying that, but you seem to have trouble finding cases of
them going over.

I guess you have a short memory. I recall one washing up on the beach in
California upside down will all hands missing and most likely dead. It
washed up on the beach upside down. About a month or two ago.

Yup, that's certainly one case. Although, there were a number of
interesting issues with that one, such as what were they doing out
there, and how many other people died in the same storm. One key
point is that had they stayed below they would have survived, and
anyone who might have been on deck on a monohull in the same
conditions could easily have been lost. If the EPIRB had been rigged,
they may have been rescued, since there was evidence that at least one
person was on the overturned vessel for some time.

And as I said, there have been a few such cases, but not very many.
Showing that cats have a capsize rate roughly the same as the monohull
sinking rate does not mark them as unsafe.

Gogarty writes:

They trip on big waves when broaching and go all the way over --
permanently.

Broaching is a feature of monohulls not multihulls. I guess you think
of pitch-pooling which is kind of common for beach cats.

--
Martin Schöön

"Problems worthy of attack
prove their worth by hitting back"
Piet Hein

Gogarty writes:

Indeed, some good friends of ours have 42 foot cruising cat that they have so
far sailed from France via the US to Australia where she now lies, for sale.
They had some bad weather but nothing that would topple the boat, not being in
the Southern Ocean. Their longest uninterrupted time out of landfall was only
two weeks.


Boat named Zazen?

--
Martin Schöön

"Problems worthy of attack
prove their worth by hitting back"
Piet Hein