[bolger] Re: various threads knotted
Peter:
Do not be falsely modest. That four-part, free-verse poem
"oysters=sharpies, etc." was a stroke of genius. I posed the question with
malice aforethought, hoping to trigger a controversy. A few (maybe two) rose
to the bait before you had the last word. I bow my head in hommage.
Do not be falsely modest. That four-part, free-verse poem
"oysters=sharpies, etc." was a stroke of genius. I posed the question with
malice aforethought, hoping to trigger a controversy. A few (maybe two) rose
to the bait before you had the last word. I bow my head in hommage.
----- Original Message -----
From: "David Ryan" <david@...>
> I recall the author of "The Perfect Storm" saying that the typical
> commercial fishing boat is built to withstand a 25 year stress, i.e.
> the worst weather it would statistically (there's that word again,)
> be likely to experience in 25 years. I think he also said North Sea
> oil platforms are built to 100 year stress.
============
With considerble safety factor. Since you usualy have to balast crusing
boats any way there is little reason not to considerbly over build the
hull of a boat. The cost of thicker plywood is not a lot and steel is
even cheaper.
An oil platform is another story. Overbuilding cost a lot more and makes
positioning the platform a lot harder.
>
> Of course, both fishing boat and oil platforms are overwhelmed by the
> weather all the time, and Momma has little regard for statistic. My
> hometown had "100 year floods" in two successive years.
>
You also see accounts of boats with standing unblievable storms and
waves. There is usualy a failure some where in the chain of judgment or
some weak spot on the boat that leads to loss if the vessel is really
suitable
for world crusing. The sea can find the smallest flaw in either.
I have been in at least three 100 year storms forturatly on dry land but I
suspect
that there statistics are not real good. I know 3 of the top people in
hydrology in
the USA and programmed models for them. A lot of the models are linear
models of
non linear systems. They work well inside the end points but supprizes
happen
if you extrapolate beyond the known data.
I would expect golbal warming to result in much larger stroms as one of it's
first
signs. Wind speed can store a lot of energy since the formula for enrgy is
mass
times velocity squared. So going from 60 knot winds to 70 know winds results
in
over a 30% increase in energy of the storm. I think we are seeing this in
the
increased frequency in 100 year events. Possibly by a factor of 10 so 100
year
events become 10 year events.
I think it is possible to build an unsinkable boat I am not sure you find an
unsinkable
crew. Fatigue and loss of sleep will eventualy get you. But the story about
the
guys that made it though a 100 foot tidal wave in an Alaskan Bay in
commercial
fishing boat show what can be done by the boat. And the idiots that have
rowed
across the Atlantic show you can find men with the stuff to do the job.
If I was designing a boat for a crossing I would go for someting in around
35 feet
in plywood or steel. If I was building her my self a large dory like the
Badger would
be a tempting choice. It gives lots of space and easy to build. I would go
with
short masts and about a 65% rig. I would add a steel and lead bulb keel as
the
folks on the Badger did. I would probably use steel constrution. It is
probably
a little cheaper than plywood and goes togeather a little quicker. I would
probably
choose an outboard for aux power probably in a well.
Gordon W5RED
G. C. Cougergcouger@...Stillwater, OK
www.couger.com/gcouger
"You miss 100 percent of the shots you never take." - Wayne Gretzky
david ryan <davi-@...> wrote:
original article:http://www.egroups.com/group/bolger/?start=2935
There is another approach possible: if you REALLY do your homework so
you know the exact stresses anticipated, and you have excellent quality
control,
you can shave down the safety factor quite a bit. I remember a lecture
from one of my professors asserting that jetliner pressure hulls have a
safety factor as low as 1.5.
Of course, if you modify the environment a little when using such a
small factor you can get a Boeing 737 convertible, as occured in Hawaii
some years ago.
lies, damn lies, and statistics."
Wondering if weather analysts in your town are unbiased or doing all
their homework, and if upstream someone has eliminated water absorbing
features.
original article:http://www.egroups.com/group/bolger/?start=2935
>snip10
> >As far as boat construction, I think the paradigm is 'safety factors'
> >rather than 'safety chains'. That is, the keel may be designed to be
> >times stronger than the greatest force expected. A less importantpart
> >may be only 5 times stronger than the greatest anticipated stress.snip
There is another approach possible: if you REALLY do your homework so
you know the exact stresses anticipated, and you have excellent quality
control,
you can shave down the safety factor quite a bit. I remember a lecture
from one of my professors asserting that jetliner pressure hulls have a
safety factor as low as 1.5.
Of course, if you modify the environment a little when using such a
small factor you can get a Boeing 737 convertible, as occured in Hawaii
some years ago.
> snipsnip My
> commercial fishing boat is built to withstand a 25 year stress, i.e.
> tsnip I think he also said North Sea
> oil platforms are built to 100 year stress.
>
> hometown had "100 year floods" in two successive years.I think Sam Clemens (Mark Twain) said: "There are three kinds of lies:
lies, damn lies, and statistics."
Wondering if weather analysts in your town are unbiased or doing all
their homework, and if upstream someone has eliminated water absorbing
features.
>
> David Ryan
> Minister of Information and Culture
> Crumbling Empire Productions
> (212) 247-0296
> > Sounds both interesting and important. So that I can try toYes, in climbing some things simply cannot be backed up, the "chain"
>make sure I
> > understand it, could you give me an example from boatbuilding of a
>system
> > that is "backed up" rather than "chained"?
>
>1) A spare part, e.g. an extra sail or emergency tiller, that is kept
>below.
>
>2) epirb and SSB radio
>
>3) life jacket and safety harness
>
>4) vane steering and electromechanical steering
>
>As far as boat construction, I think the paradigm is 'safety factors'
>rather than 'safety chains'. That is, the keel may be designed to be 10
>times stronger than the greatest force expected. A less important part
>may be only 5 times stronger than the greatest anticipated stress.
is one link long, so it better be a BIG FAT link. Unfortunately, at
sea, nothing is fail safe when Momma comes calling.
I recall the author of "The Perfect Storm" saying that the typical
commercial fishing boat is built to withstand a 25 year stress, i.e.
the worst weather it would statistically (there's that word again,)
be likely to experience in 25 years. I think he also said North Sea
oil platforms are built to 100 year stress.
Of course, both fishing boat and oil platforms are overwhelmed by the
weather all the time, and Momma has little regard for statistic. My
hometown had "100 year floods" in two successive years.
David Ryan
Minister of Information and Culture
Crumbling Empire Productions
(212) 247-0296
The problem with twin engines is fuel contamination and
depeletion is probably the biggest risk to the system and will
probably affect both engines.
Gordon W5RED
G. C. Cougergcouger@...Stillwater, OK
www.couger.com/gcouger
"You miss 100 percent of the shots you never take." - Wayne Gretzky
depeletion is probably the biggest risk to the system and will
probably affect both engines.
Gordon W5RED
G. C. Cougergcouger@...Stillwater, OK
www.couger.com/gcouger
"You miss 100 percent of the shots you never take." - Wayne Gretzky
----- Original Message -----
From: "David Ryan" <david@...>
To: <bolger@egroups.com>
Sent: Thursday, February 17, 2000 12:24 PM
Subject: [bolger] Re: various threads knotted
> >In a message dated 00-02-17 10:18:56 EST, you write:
> >
> ><< I think may be an argument for maximum simplicity. Budget is always a
> > design constraint, and the simpler and cheaper things are, the more
> > easily they can be backed up rather than chained.
> > >>
> >David,
> > Sounds both interesting and important. So that I can try to make
sure I
> >understand it, could you give me an example from boatbuilding of a system
> >that is "backed up" rather than "chained"? Thanks, Warren
>
> A boat with two motors is backed up, a boat with one (and cannot get
> you out of trouble with paddles and oars) is chained, i.e. if the
> motor fails, you are stuck.
>
> David Ryan
> Minister of Information and Culture
> Crumbling Empire Productions
> (212) 247-0296
>
> ------------------------------------------------------------------------
> GET A NEXTCARD VISA, in 30 seconds! Get rates
> as low as 0.0% Intro APR and no hidden fees.
> Apply NOW!
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>
>
>In a message dated 00-02-17 10:18:56 EST, you write:A boat with two motors is backed up, a boat with one (and cannot get
>
><< I think may be an argument for maximum simplicity. Budget is always a
> design constraint, and the simpler and cheaper things are, the more
> easily they can be backed up rather than chained.
> >>
>David,
> Sounds both interesting and important. So that I can try to make sure I
>understand it, could you give me an example from boatbuilding of a system
>that is "backed up" rather than "chained"? Thanks, Warren
you out of trouble with paddles and oars) is chained, i.e. if the
motor fails, you are stuck.
David Ryan
Minister of Information and Culture
Crumbling Empire Productions
(212) 247-0296
> Sounds both interesting and important. So that I can try tomake sure I
> understand it, could you give me an example from boatbuilding of asystem
> that is "backed up" rather than "chained"?1) A spare part, e.g. an extra sail or emergency tiller, that is kept
below.
2) epirb and SSB radio
3) life jacket and safety harness
4) vane steering and electromechanical steering
As far as boat construction, I think the paradigm is 'safety factors'
rather than 'safety chains'. That is, the keel may be designed to be 10
times stronger than the greatest force expected. A less important part
may be only 5 times stronger than the greatest anticipated stress. I've
heard that the rigging in America's Cup 12-meters had safety factors
just over 1. They had almost no margin of error at all.
Peter
In a message dated 00-02-17 10:18:56 EST, you write:
<< I think may be an argument for maximum simplicity. Budget is always a
design constraint, and the simpler and cheaper things are, the more
easily they can be backed up rather than chained.
Sounds both interesting and important. So that I can try to make sure I
understand it, could you give me an example from boatbuilding of a system
that is "backed up" rather than "chained"? Thanks, Warren
<< I think may be an argument for maximum simplicity. Budget is always a
design constraint, and the simpler and cheaper things are, the more
easily they can be backed up rather than chained.
>>David,
Sounds both interesting and important. So that I can try to make sure I
understand it, could you give me an example from boatbuilding of a system
that is "backed up" rather than "chained"? Thanks, Warren
>If you do something with a 2% chance of killingClimbers talk a lot about safety statistic. Some of the early
>you every year, you have little chance of collecting Social Security,
>but if you just do the one thing, because it is important to you,
>perhaps it's reasonable.
pioneers were Bell Labs scientist, so maybe that has something to do
with it.
Anyway, the usual context is protection, i.e. things you put in the
rock to keep you from hitting the ground. You are alway supposed to
"back up" your protection, so you're never totally dependent on one
piece of pro.
The worst thing you can do in climbing is create a "chain," that is
to say a protection system where failure of one piece means failure
of the whole system.
The math goes something like this.
If you have one piece with 25% likelyhood of failure, backed up by
another piece with a 25% failure rate, the overall rate for the
system is 6.25%
If you have one piece at 25%, what you see is what you get.
If you have a chain of two 25% pieces, the system failure rate goes
up to 43.75%.
Some chains are unavoidable; harness to rope to belay, and are build
on rock-solid, virtually failure-proof devices. The rest of the
system is build to avoid any sort of chaining. It's safer to be at
the mercy of only one sketchy piece than two.
So what does this have to do with boats?
I think may be an argument for maximum simplicity. Budget is always a
design constraint, and the simpler and cheaper things are, the more
easily they can be backed up rather than chained.
As to serial probability; Vegas has been reaping the rewards of it's
counter-intuitive behavior for years. If you do something that has a
2% chance of killing you every year, you have a two percent chance of
being killed each time you do it.
YIBB,
David Ryan
Minister of Information and Culture
Crumbling Empire Productions
(212) 247-0296
Thoughts related to various threads.
1) I was so impressed with myself by reducing my leeboard boat pics
from 2.5M (in tif format as scanned by a friend) to 250K (in jpg
format) that I was going to stop there. I'll hold off until I get the
size down some more.
2) On crossing oceans in small boats. It is ironic that Tinkerbelle
(and the Kelpper) made it across an ocean that has claimed so many much
larger, better built, and better designed vessels. It is difficult to
access the danger. What chance of drowning is considered dangerous?
What chance is acceptable? As a benchmark, consider Mr. Bolger's
comments about crossing the pond in Centennial II. 'It would be quite
dangerous. If 1000 started out over the space of 10 years, I wouldn't
be surprised if 20 or so went missing.' (quoted from memory) That's a
2% chance of drowning. If you do something with a 2% chance of killing
you every year, you have little chance of collecting Social Security,
but if you just do the one thing, because it is important to you,
perhaps it's reasonable.
Incidently, there was an article in Yachting a long time ago about 2
men who sailed US to England in a Cal 20. It might be interesting to
review their preparations. As I remember, they strengthened the transom
and reduced the cockpit volume. It was probably in the 1960's.
Incidentally, if you do try to look up something like this, you may
well find that the copies in your public library are pretty beaten up.
Try a university library. When I was at graduate school at Brown, the
library had absolutely mint copies of Yachting (in case I wanted to
look up the lines of Phil Rhodes's Weatherly) and The Saturday Evening
Post (where I could find every Nero Wolfe story serialized there).
(Someone is sure to ask: Nero Wolfe is the main character is a series
of detective stories and novels by Rex Stout. But, if you are a serious
reader of mysteries, you already know that.)
3) Here I am doing my best to be sorry for taking myself too seriously,
and the next thing I am being hailed as a literary genius for a "bot
mot" about oyster shells and codfish bones. I was really just trying to
make the point that the distinctions are less about what the boats are
than about how they are derived.
4) Thanks for the references to Gavins design list and site.
Peter
1) I was so impressed with myself by reducing my leeboard boat pics
from 2.5M (in tif format as scanned by a friend) to 250K (in jpg
format) that I was going to stop there. I'll hold off until I get the
size down some more.
2) On crossing oceans in small boats. It is ironic that Tinkerbelle
(and the Kelpper) made it across an ocean that has claimed so many much
larger, better built, and better designed vessels. It is difficult to
access the danger. What chance of drowning is considered dangerous?
What chance is acceptable? As a benchmark, consider Mr. Bolger's
comments about crossing the pond in Centennial II. 'It would be quite
dangerous. If 1000 started out over the space of 10 years, I wouldn't
be surprised if 20 or so went missing.' (quoted from memory) That's a
2% chance of drowning. If you do something with a 2% chance of killing
you every year, you have little chance of collecting Social Security,
but if you just do the one thing, because it is important to you,
perhaps it's reasonable.
Incidently, there was an article in Yachting a long time ago about 2
men who sailed US to England in a Cal 20. It might be interesting to
review their preparations. As I remember, they strengthened the transom
and reduced the cockpit volume. It was probably in the 1960's.
Incidentally, if you do try to look up something like this, you may
well find that the copies in your public library are pretty beaten up.
Try a university library. When I was at graduate school at Brown, the
library had absolutely mint copies of Yachting (in case I wanted to
look up the lines of Phil Rhodes's Weatherly) and The Saturday Evening
Post (where I could find every Nero Wolfe story serialized there).
(Someone is sure to ask: Nero Wolfe is the main character is a series
of detective stories and novels by Rex Stout. But, if you are a serious
reader of mysteries, you already know that.)
3) Here I am doing my best to be sorry for taking myself too seriously,
and the next thing I am being hailed as a literary genius for a "bot
mot" about oyster shells and codfish bones. I was really just trying to
make the point that the distinctions are less about what the boats are
than about how they are derived.
4) Thanks for the references to Gavins design list and site.
Peter