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post #161 of Old 02-24-2018
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Re: Multihull Popularity and Interesting Designs

Originally Posted by smj View Post
It’s not the poll that’s interesting it’s the post by Sandy, an old employee of the NTSB.

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Ah, sorry about that - this post...


Multihull Safety

by sandy daugherty Fri Apr 11, 2008 3:06 pm
Escape hatches are required by law in the CE. Thats why you see them on many cats. Their desireability is open to question.

Before I retired from the NTSB I had the oportunity to study the complete Coast Guard database of boating accidents and Summary Data of proprietary actuarial information from sources within the Lloyds' Groups, with a focus on vessels with accomodations including permanent berths, head(s) and galley. I tried to exclude beach cats and tris, and daysailers by excluding boats under 24 feet. The data was not user-friendly and required a lot of external correlation because many vessels were incorrectly classified. That ultimately prevented releasing any conclusions because GI+MGI=GO (garbage in plus more garbage in still equals garbage out.) This was also a problem with the older NTSB databases that included pre-digital-age reporting. However, I discovered in the process that there were few differences between monohul and multihull rates of occurrence. That's easy to understand; human error trumps mechanical failure and design deficiency evermore. Here are some of the facts that did become apparent: Vessels designed for racing and record attempts break. Vessels built for cruising don't break. People who race drive themselves and their vessels to the limit. [please forgive the pun] Cruisers drive their homes to the next nice place.
The rates of actual vessel loss (outside of competition) remained the same for monohulls and multihulls, over many years, with catamarans emerging slightly ahead of other vessels in the last years of available data. Reports of large numbers of catamaran roll-overs are probably anecdotal as accident statistics reveal a (slight) decline, with a slight increase in sinkings among monohulls. There was a lot of confusion in the data between catamarans and trimarans, which I can only suggest an interpretation for:

Vessels purpose built for competition are not recorded as such. Each accident had to be researched individually. Many were not insured, meaning that Insurance data would not take them into account. In fact, Many sinkings of monohulls were extremely difficult to document because they were never widely reported. This is changing as news media is becoming more interested, especially in colorful visuals.

A very small percentage of trimarans are sold for cruising, as a very small percentage of catamarans are sold for racing. The best correlation between racing and competition vessels was a ratio of lwl to mast height.

Where I was able to distinguish between cruising and competition vessels, I found that the rate of personal injuries and single fatalities was higher among monohulls. That should merit further study because those injuries appeared to occur in better weather conditions, not in worse. These accidents included cabin injuries, man-overboards, and deck injuries such as inadvertant jibes.

My conclusions were impaired by the quality of data, and my proposal of a National Transportation Safety Board Special Study was properly overshadowed by more important issues. But there is enough factual data to prove that cruising multihulls are no more, and possible less dangerous than cruising monohulls in all reported conditions of weather, traffic, and human frailty, regardless of location.
Well, there you have it.

Last edited by smackdaddy; 02-24-2018 at 05:58 PM.
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