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Old 15-01-2007, 18:44   #16
smm
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Wow, ID that was really impressive. Thanks.

So what your statistics say is that the categories are more alike
than different and I agree. More specifically, the only boat
in your light category that I think of as high-performance is
the Outremer.

Quote:
Originally Posted by Intentional Drifter
Light

Kelsall Space 52
Outremer 45
Dragonfly 1200
Nautitech 40
Lagoon 410
I'm not familiar with the Kelsall, but the others seem to be
smaller non-performance orientated designs which would
easily be overloaded, particularly with a crew of 3 or 4.
I don't think that your pounds per waterline foot variable
accounts for this adequately.

While it isn't statistical, I note that the Outremer finished
behind (by 7 hours) a Catana which was 13 feet longer,
and just behind the Kelsal 52. The first Lagoon 410 finished
3 days after the Outremer, the Dragonfly 2 days. The Outremer
also bested the winning (56 foot) monohull by several hours.

So anecdotally, the "high performance" catamaran is _much_
faster that both larger catamarans and larger monohulls. You can
average the performance of the Outremer and the Lagoon 41, but
I don't think that the resulting number means anything. I wish you
had some data on the Australian cats...

On the subject of numerical performance, I've been looking for
a way of comparing performance that is risk-neutral. Since the
ultimate limit to multihull performance is tipping over, I think that
the risk of capsize needs to be factored in. If, for example, the
Outremer won just because it had a huge rig and was sailed much
closer to the edge, then I'm much less impressed.

The best I've been able to come up with is to look at boat speed
(or VMG upwind) relative to the true wind as a percentage of
the static capsize windspeed.

-Scott
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Old 15-01-2007, 20:46   #17
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Scott --

I would also like to see data on the Australian cats. From what I can tell, several of the designers have been doing some very interesting things. I've looked at the literature on the Fusion and it seems like a slick package for not a lot of money. I do wonder, though, about their seeming attraction to putting the helm station on the salon bulkhead in such a way that you have to look through the salon. Many of them do it this way.

The Kelsall used to be built in the UK, but they moved to NZ a number of years ago. They are built light and seem comparable to an Outremer in several respects.

Of course, you are correct in that this analysis really can't say much about individual boats. Most of the boat models in the ARC were only represented by one boat and n's of one are always to be avoided with inferential statistics.

RE: capsize risk, I seem to recall a paper written by John Shuttleworth on the topic. I'll see if I can find it.

ID
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Old 17-01-2007, 13:19   #18
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International drifter, I do second Evan's comments. This chart is fairly revealing, it shows the same boat at different weights with wind being constant. In order to have any sort of statistically valid comparison, you have to limit the variables to only a few, this is a nice diagram because it shows the affect of only one variable, weight.

I think the ARC is mainly concerned with safety, not speed in crossing, so you'll have too many variables to be predictive. If in your analysis you see a wide variation in identical boats, then obviously the predictive factor is something other than boat type. If there is a race with different boat types which offers some serious money for winning, look at that. I wish I were a racer who could point you to just such a race, but I'm a family cruiser with a 2 year old, and can only go as fast as my wife will let me while carry around everything I own! SLOOOWWWWW!
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Old 18-01-2007, 05:47   #19
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Quote:
Originally Posted by Intentional Drifter
Scott --
I've looked at the literature on the Fusion and it seems like a slick package for not a lot of money. I do wonder, though, about their seeming attraction to putting the helm station on the salon bulkhead in such a way that you have to look through the salon. Many of them do it this way.

ID
I havent sailed a fusion - but I have raced against one, it was camp cruising light but even so it was impressive. To be very accurate the designer is Gary Lidgard who is actually a KIWI I think. But he lives on the gold coast know (again - I think). The fusion is a semi production boat, thus far I think most of them have been finished post factory. They were being built in the whitsundays but I heard that they were moving offshore, but thats not confirmed. Also thus far I have only seen one come on the second hand market, which is at least a pointer to owner satisfaction.
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Old 18-01-2007, 09:32   #20
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light?

I don't think any of the boats on that list are "light"

This monohull 58' cold molded was 25,000 when launched. (with a 14000 pound keel)

http://www.cruisersforum.com/gallery...p?i=2765&c=502
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Old 18-01-2007, 09:59   #21
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Tnflakbait (interesting handle -- does it have a story?) --

"Light" is, of course, a relative concept. For the analysis, this was not determined by any sort of established definition, but rather empirically. Using the displacement numbers as published (and we have no idea what the actual weight of the boats were, as they sailed), I simply plotted out those numbers and using the natural break-points in the "pounds per foot of length at the waterline" and assigned them to their respective categories.

Now, it may well be that some of the boats (Sir Henri, for example, which seems to have been in every other ARC for over 10 years) worked very hard to keep additional weight off the boat, while others in the same category really paid no attention to it. This would likely result in even greater variability within the category, such that some of the "light" boats -- as they actually sailed -- were heavier than boats in another category. But, of course, this is conjecture and we don't know it.

Surely, one of the most frustrating parts of this discussion is the lack of actual knowledge and common measuring methods.

ID
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Old 18-01-2007, 10:17   #22
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Schoonerdog -- Actually, I'm going to disagree with you (at least a bit) about what makes for a valid comparison. If, we had a situation where we could have a reasonable number of boats of the same model (even as few as 4 each would be much better, but 10 each would result in a high degree of confidence), outfitted the same and then compare those to another group, of the same model, varying only with the weight variable, then I would say that you are correct. This would be a far superior test of the hypothesis and be a true experimental design (assuming they were sailing the same course at the same time).

Unfortunately, I was limited to the data available, which did not conform to the needs of a true experiment. So, we're stuck with what we have, but within that, the statistics run and the results can be trusted. I say that because across the boats we can further assume that there were many variables that were not systematically controlled (by boat model) and therefore would be the same as a random selection. In such a design, the goal is not "making everybody the same", but to approximate reality, which is full of uncontrolled random variation. (By the way, this is a commonly misunderstood feature of research designs, even in the scientific community.)

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Old 18-01-2007, 10:30   #23
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It's pretty clear there is a lack of hard data. Maybe we all just need to enter in the same race to generate some? We could even get real weights on the boats.

How about the Marion to Bermuda race? It's only about 4 days, so not a huge investment in race time, but long enough to be somewhat representative of a normal ocean passage. It is a race oriented to cruisers so is also typically not hard core racing boats.

I won't be ready for this year, but how about 2009?

Mark.
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Old 18-01-2007, 10:40   #24
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Mark --

I think you are right. Furthermore, I think that this is the only way we will ever get such data. I really don't see the manufacturers being interested in doing it (too much risk of having their advertising debunked). Likewise, I think the magazines would be even less interested, since the results would guarantee that some of their advertisers would be unhappy.

Of course, what you're talking about would be a logistical nightmare, but it could be lots of fun! I'm game, so long as my cruising plans would allow.

ID
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