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mstrebe 16-08-2015 22:51

And the safest hull material is...
 
There are frequent discussions regarding the various merits of hull materials on this site. My own personal opinion is quite open; I own two FRG hulls and one plastic hull, and I've lived aboard a steel hull for years. Probably my natural preference would be aluminum.

But it occurred to me that all of the material science posts, the anecdotes, and the discussions of maintenance, damage, and degradation all really come down to one thing: Which hulls are best for survival?

Well, I'm a statistics person, especially when we're talking about risk of mortality, so I like to avoid stories about what somebody somewhere once heard, and go with the largest collection of good numbers I can find.

The USCG compiles the most complete publicly available numbers regarding pleasure boat accident statistics, and they do track hull materials. Now, they don't track how many boats exist of a specific type, so there aren't numbers to say how likely a boat is to have an accident by hull type, but they do provide us with a more important number:

Given an accident, how likely is death or injury by hull type?

With no further ado, these are those numbers for the past three years, along with the three-year average (sorry about the crappy formatting, blame forum software):

2014 Accidents fatalities injuries f/a i/a
Aluminum 815 163 411 20% 50%
Fiberglass 3946 299 2041 8% 52%
Plastic 134 69 67 51% 50%
Rubber/Vinyl/Canvas 60 27 32 45% 53%
Steel 51 0 10 0% 20%
Wood 71 8 17 11% 24%

2013
Aluminum 862 190 425 22% 49%
Fiberglass 4087 253 2013 6% 49%
Plastic 126 48 55 38% 44%
Rubber/Vinyl/Canvas 55 19 28 35% 51%
Steel 36 1 12 3% 33%
Wood 84 13 22 15% 26%

2012
Aluminum 861 197 439 23% 51%
Fiberglass 4529 332 2357 7% 52%
Plastic 107 45 65 42% 61%
Rubber/Vinyl/Canvas 65 37 25 57% 38%
Steel 47 1 6 2% 13%
Wood 81 4 26 5% 32%

three-year Average
Aluminum 22% 50%
Fiberglass 7% 51%
Plastic 44% 51%
Rubber/Vinyl/Canvas 45% 48%
Steel 2% 22%
Wood 11% 27%

The bottom line is that the statistics for all hull types except Wood are very "normal", meaning there's enough data that they don't vary much from year to year.

The next results are pretty shocking: They show definitively that of boats involved in accidents, Steel boats are by far the safest, at 2% fatality rate per accident, fiberglass at 7%, wood at 11%, aluminum at 22%, and other materials at about 45%.

Now, it's important to understand that these hulls are of all pleasure boat craft (not just sailboats), that sailboats represent a very small number of the overall statistics, and that all accident types tracked by the USCG are included.

There is also a very strong "unseen attractor" in these numbers: Size of vessel. Steel vessels are the very largest. Rubber are the very smallest. Obviously larger vessels fare better in accidents. So there is some serious skew to the numbers that we can't divide out.

That said, for the hull types we really care about (steel, aluminum, fiberglass, and wood) we can work out the sizes. Fiberglass fares particularly well considering that on average, they would be the smallest of these four hull types. There are very few 25' steel hulls, but there are hundreds of thousands of 25' fiberglass hulls.

These numbers are large numbers with real meaning. The fact that aluminum fares so poorly compared to FRG is shocking to me, especially considering that aluminum boats would be in the same size range or larger than fiberglass. The fact that steel is by far the safest material is also a bit shocking, and not what I would have predicted, but it may be that only the very largest boats are made of steel.

I have to wonder what it is that I don't know about aluminum that makes it three times more likely than FRG to have a fatality in an accident and ten times more likely than steel, especially considering that the average aluminum boat is larger than the average FRG boat.

Anyway, it's changed my opinions about hull material dramatically.

JPA Cate 16-08-2015 22:57

Re: And the safest hull material is...
 
There are a whole lot of aluminum runabouts. Fishermen go missing from them often. Perhaps that skews the aluminum statistics.

To evaluate that data, it would help to know more about the types of boats involved.

Ann

Jim Cate 16-08-2015 23:36

Re: And the safest hull material is...
 
From memory, if you look at the statistics overall, the number of fatalities recorded in sailing vessels of any construction is tiny. The numbers that you are providing prove absolutely nothing about the sort of boats that we all use. As Ann says above, "tinnies" as they are called here in Oz (10-20 foot open aluminium craft with outboard motors) supply the majority of accidents, both fatal and just debilitating.

Find another horse to beat.

Jim

El Pinguino 16-08-2015 23:49

Re: And the safest hull material is...
 
Statistics show that 97.25% of statistics are rollocks.

Delancey 17-08-2015 02:39

Re: And the safest hull material is...
 
When someone has a heart attack and dies out on the water they become a statistic. Can happen on any boat, doesn't matter what the boat is made from, and it happens all the time. What percentage of the above fatalities are heart attacks? These numbers you have provided are meaningless.

Sandero 17-08-2015 03:08

Re: And the safest hull material is...
 
Sorry to say it's hard to get any useful information to inform one's decision as to what sort of material would be "safest". Would one have to analyze similar or identical "collisions" / incidents of the different materials, controlling for size and design and of course conditions? YES!

One also needs to consider that GRP can be manufactured since molds are involved but metal boats are one off. This means that GRP is more suited to pleasure craft and not large boats.

And what is the point of this thread?

Delancey 17-08-2015 03:20

Re: And the safest hull material is...
 
90% of boating related fatalities occur between 4PM and 6PM, involve alcohol, and have nothing to do with type of hull construction.

Learned that at the stupid boating safety class the law mandated I take.

Also if you have a gas engine you should have a flame arrestor, bow riding like in the movie Titanic is dangerous, you can't have more than two people on a jet ski rated for two people, and that a vessel that is not under command (at anchor) is the give way vessel.

valhalla360 17-08-2015 03:37

Re: And the safest hull material is...
 
How many high speed planning boats are made of steel?


Lots are made of fiberglass and aluminum.


How many boats under 20' are made of steel?


Lots are made of fiberglass and aluminum.


Wood has a similar pattern.


This alone invalidates the vast majority of your assertions. If you wanted to get something meaningful, you would have to split out sailboats first and remove the small day sailors but even then steel boats traditionally have been the bigger boats and often designed for different purposes.


Also most people buy fiberglass because it's easy to maintain. Those who go with wood or steel tend to be fanatics about maintenance. Take away fiberglass as an option and those who don't like to do maintenance suddenly are on wood or steel boats changing the numbers.


It gets very hard to pare out the unrelated aspects to determine the impact of material on safety.

FSMike 17-08-2015 04:40

Re: And the safest hull material is...
 
Just to show my ignorance, what do f/a and i/a stand for?
Thanks

estarzinger 17-08-2015 05:07

Re: And the safest hull material is...
 
Quote:

Originally Posted by Delancey (Post 1892575)
90% of boating related fatalities occur between 4PM and 6PM, involve alcohol.

Flat out not true.

just looking at the 2014 USCG data*:

- only about 12% of fatilities occur between 4:30pm and 6:30pm (graph on page 18)
- only 18% had alcohol listed as a primary contributing factor. (108 out of 610 fatalities on page 19 table)

*(https://www.uscgboating.org/library/a...stics-2014.pdf)

Unfortunately the safety and law enforcement communities have long standing 'political' agenda's regarding alcohol and life jackets that are not well supported by the data. I might quote from the latest academic research (2015 statistical boating risk analysis by Viauroux and Gungor) on the alcohol subject "our result is consistent with the results of Loeb et al, who also find that there is no persuasive evidence of alcohol contributing substantially to operator fault in fatal accidents".

Delancey 17-08-2015 05:19

Re: And the safest hull material is...
 
I am also pretty sure that a vessel not under command (at anchor) is not the give way vessel, but that's what the instructor at the required boating safety class said.

Of course her day job was a Driver's Education instructor and I think most of her boating experience was as a passenger on the Staten Island Ferry so I didn't put a lot of stock in what she said.:banghead:

David M 17-08-2015 05:43

Re: And the safest hull material is...
 
There are so many other reasons why someone might die other than hull material that I think relating deaths to hull material is almost entirely irrelevant. No offense intended at all.

One brings in indirect relationships such as the fact that all personal watercraft (PWC's) are made of fiberglass where the actual cause of PWC deaths are related to the fact that most of their operators are young and inexperienced and therefore many PWC's are operated in a dangerous manner...which has nothing to do with the fact that PWC's are made of fiberglass.

PortClydeMe 17-08-2015 05:44

Re: And the safest hull material is...
 
2 Attachment(s)
Safest hull material? You need look no further than Boston Whaler. :wink:

farshore 17-08-2015 05:52

Re: And the safest hull material is...
 
99.99% of all vessel tonnage is built from steel. There are structural reasons for this that have been well known for over a century. If you are fgoing to sail your boat say up on an atoll because you spent to much time on computers rather than learning to navigate, you might want steel.
Next best might be epoxy/kevlar; might get all wobbly after bulkheads break loose but immensley strong. There are no perfect materials, every casualty involves different circumstances and dissimiliar outcomes depending mainly on your skills and a good dose of luck! If you need all these statistics to go to sea....understand that if you stand with one foot frozen in a bucket of ice and the other in a bucket if boiling water....statistically you are comfortable.
Or in the USA the unemployment rate is statistically 5.3%....

FamilyVan 17-08-2015 06:10

Re: And the safest hull material is...
 
Quote:

Originally Posted by farshore (Post 1892665)
99.99% of all vessel tonnage is built from steel. There are structural reasons for this that have been well known for over a century. If you are fgoing to sail your boat say up on an atoll because you spent to much time on computers rather than learning to navigate, you might want steel.
Next best might be epoxy/kevlar; might get all wobbly after bulkheads break loose but immensley strong. There are no perfect materials, every casualty involves different circumstances and dissimiliar outcomes depending mainly on your skills and a good dose of luck! If you need all these statistics to go to sea....understand that if you stand with one foot frozen in a bucket of ice and the other in a bucket if boiling water....statistically you are comfortable.
Or in the USA the unemployment rate is statistically 5.3%....

Uh oh, you're going to incurred the wrath of the anti steel club with that comment ;)

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