--- In harryproa@yahoogroups.com.au, Mike Crawford <jmichael@g...>
wrote:
>
> <<Boats have been knocked down and righted. Including the amusing
case
> of one of Russ' friends falling asleep on his watch and waking up
to
> find the boat happily loping along in the pod immersed condition.>>
>
> Good point. I'm not impressed by arguments that boats are safe
> because they have made ocean crossings. Safe miles at sea are
often
> more a product of good seamanship and good luck than actual boat
> safety. But actual knockdowns and recoveries say something.
That's not true. Boats are 99% safe (as far as design optimisation
is concerned) and a prooven concept evolved over thousands of years,
we are only doodling at the margins.
Or,
That isn't the argument, the argument is that Brown had the uniquie
opportunity of growing up with one of the greatest designers of the
day who' pals were designers, and while we were playing with blocks,
he was playing with proas, long before they were fashionable, and
then he sailed them way out there for years beating other boats
surviving shipwreck and generally getting the concept roughed up in
way he hasn't been willing even to talk about, and along the way
built 4 or so boats, the biggest footage of proas every built by any
one persons... Yatta Yatta.
>
> For the record, I've been a fan of the "Dutch Proa" ever since I
first
> saw the web site, and would like to see more people work on the
> concept. I think it's neat that you can have a training wheel
which
> will increase righting moment to give you time to loosen the
sheets. As
> Han Biljard points out, this removes the temptation to push the
boat
> past its limits because you slow down as soon as that leepod starts
> creating drag. What a great combination.
You might like the quadramaran too.
This would be a lot better than the 150%
> buoyancy amas we see on some trimarans, which will raise the whole
boat
> and make a capsize much more dangerous.
You're design wise, I don't at all mean this as a personal coment, a
glass half full guy. Here we have the design format with the
greatest stability per dollar or calorie of building efort, but
you're not happy because having protected you better than any known
boat form, it can be capsized in some eventuality. You will sell
safety down the river any day as long as the capsize is gentle. Good
news is I think we can find you a boat.
>
> If the leepod is integral to the leeward hull, such as on Jzerro,
then
> it's not inconceivable that it would fit these criteria.
>
> The challenges of a leepod on a harryproa would then be twofold:
>
>
> A) Structure and complexity
>
> The leeward hull in a harryproa has a lot of stress going
through it,
> and you'll need some solid structure if you're going to want to put
> storage or accommodations inside the leepod. This is not
impossible,
> but it adds complexity to what is a very simple (and easy to
construct
That's just in the sales borchure they gave up on that a long time
ago)
> design.
You are right.
>
>
> B) Increased requirement for righting moment
>
> A Jzerro design is great for a leepod because it has most of its
> weight in the leeward hull. Even with water ballast in the
windward
> hull, there's not a whole lot of weight up there in the event of a
> knockdown, and it is angled in such a way as to contribute to
righting
> even when the mast hits the water.
Basically agree, they are rarely required to use water apparently
>
> The harryproa has more than half of its weight to windward,
though,
> and with standing headroom and a cockpit there, that weight is a
lot
> higher up. Between the additional weight and its angle to the
leeward
> hull, this will create a lot more heeling moment than a Jzerro
design if
> the boat goes past 90 degrees due to sea action or wind pressure on
the
> upturned hull.
You are right. Which is why we don't let this bother us. Repeat
after me: "It can't happen, it can't happen..." This boat throws
all it's eggs into this one basket. Even if you could figure out a
way to stop this from happening I wouldn't pay five cents for the
privilege, any more than I send my money to those people who sell the
full=face TV watching helmets, for people who doze off watching TV
and fall onto the floor. I don't see the rationality to persuing
with enourmous cost the one thing least likely to happen. There are
three other capsize directions this isn't going to help at all; there
are meriad other potential disasters. I'm not throwing the budget and
the design functionality out of the window for the least likely
concern. I'd pay 10K to make the boat bigger, I'd feel safer then,
by the wat that was the whole point of the design. I won't pay for
what you are suggesting.
>
> It's this heeling moment that the leepod would have to counter,
and
> that's different than with Russ Brown's boats.
>
> ---
>
> With enough design time and experimentation it's probably
possible to
> overcome both of these challenges. The resulting design would get
away
> from Rob's criteria of maximum speed, accommodations, and righting
> moment for a minimum of weight, structure and complexity, but no
one
> every said that every single one of Rob's criteria is sacred.
Least of all Rob, we are a long way form Kansas on this project
already.
>
> I think the key is in getting data on how a leepod would affect a
> weight-to-windward proa once it's in a capsize condition of 90+
degrees
> heel. If there were some solid calculations or real-world tests of
this
> combination, I believe a number of people would consider adding
leepods
> to their designs.
I probably wouldn't but there may be a reason to add something to the
base of the spar. For me I would probably look at control issues or
ways of lowering the spar cost if that also created a way to get a
bump on the lee side it might be worth considering.
>
> - Mike
>
>
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