"Roger Long" wrote in message
...
Uh oh. Don't get me started on Metacenters. As the name implies they
aren't real and nothing makes stability harder to understand from what is
generally written. I've given many lectures on stability and I usually
have to spend the first third of the lecture getting the students to
forget all the stuff they read the night before.

Metacenters and metacentric height are very useful calculation shortcuts
for naval architects but a very poor way to understand the forces
involved.

Even buoyancy is imaginary. Anybody want to try and guess what really
holds a boat up?

--
Roger Long

Bad weather and/or beautiful women.

--
"j" ganz @@
www.sailnow.com

wrote in message
news
On Thu, 17 Apr 2008 12:12:26 -0400, "Roger Long"
wrote:

Uh oh. Don't get me started on Metacenters. As the name implies they
aren't real and nothing makes stability harder to understand from what is
generally written. I've given many lectures on stability and I usually
have
to spend the first third of the lecture getting the students to forget all
the stuff they read the night before.

Metacenters and metacentric height are very useful calculation shortcuts
for
naval architects but a very poor way to understand the forces involved.

Even buoyancy is imaginary. Anybody want to try and guess what really
holds
a boat up?

A Coast Guard Boarding.




Heh... pirates!

--
"j" ganz @@
www.sailnow.com

"Bruce in Bangkok" wrote in message
...
On Wed, 16 Apr 2008 09:35:58 -0700, "Capt. JG"
wrote:

"Bruce in Bangkok" wrote in message
. ..
On Tue, 15 Apr 2008 20:07:00 -0700, "Capt. JG"
wrote:

"Jere Lull" wrote in message
news:2008041519282516807-jerelull@maccom...
On 2008-04-15 08:20:21 -0400, Brian Whatcott
said:

On Tue, 15 Apr 2008 12:55:37 +0700, Bruce in Bangkok
wrote:


Are you stating specifically that a sailing boat that loses its mast
is in more danger of capsizing then when the rig was in place?? I
would appreciate it if you could elaborate on this as it was always
my
understanding that once the rig was either cut away or retrieved and
lashed on deck the boat rode no worse then it had with the rig in
place.

It was always my thought that once the rig was gone that stability
of
the ballasted hull would become slightly better with no weight above
the deck line.

I emphasize that I have no interest in this discussion other then
this
single point which is probably of interest to most cruising sailors.


Bruce-in-Bangkok
(correct email address for reply)

There are conflicting factors (as usual): the pro-stability factor is
the considerable mass far from the roll center (called moment of
iniertia) which slows the rate of roll in adverse seas.
The con-stab factor is the increased windage and weight above the
water line.

Brian W

As I read this thread, the mast *might* slow wave-induced roll enough
to
prevent a roll-over. Anyone who's taken their boat out without a mast
up
can attest that the boat is a lot less "stable".

But such waves don't come without wind trying to roll the boat all on
its
own.

I can only believe that having the mast and remains of sails "up" once
the
boat is inverted would be a distinct disadvantage to coming back up in
a
timely manner. Dinghy sailors know how much drag a little bit of cloth
can
create.

--
Jere Lull
Xan-à-Deux -- Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/



Likely true. For catamarans, if inverted, they're more stable upside
down.
Of course, this comment might open up a religious war about which one is
better offshore. :-)

Being a bit bored this afternoon - the glue is hardening. My car is
broke and I don't have anything pending for an hour or I'd like to
forward the proposition that Catamarans are the safest type of vessel
to sail. Think about it for a moment.

1. They are stable in either the upright or inverted position

2. Modern Cats have a hatch in the bottom of the hull so it doesn't
make any difference which side up you are you can get in and out.

3. If inverted the strongest part of the boat - the hull - is the
portion exposed to the waves.

4. The rig is pretty simple with only one shroud a side and a head
stay.

5. Cats don't rock so bad so you don't need a gimbel stove, and your
significant other seldom barfs in the mashed potatoes.

6. Cats have big windows so you don't need so many lights.

7. Cats have two separate bedrooms so when you really have a bruhaha
with She Who Must be Obeyed you can go off to the other hull to lick
your wounds.

8. Cats usually have a BIG cockpit which allows you to sit out in the
summer's breezes in the evening and enjoy a cool beverage. It also
allows you to feed the mosquitoes but what the Ha, mosquitoes got to
live too. Living in tune with nature. That's the ticket. Participating
in the Malaria Fever Research Project if also a worthy undertaking.

No, there is no question but what Catamarans are safe, congenial and
in tune with nature. The only way the thinking man will sail.

Bruce-in-Bangkok
(correct email address for reply)


Hard for me to disagree... probably the only major negatives are stowage
and
cost, the former of which you have to watch or it'll get out of control
and
really slow down the boat. Crew fatigue is a *big* factor for
long-distance.
I saw a cat that had screens up around the cockpit, so screw the
mosquitos.

When we charter in various locations, we always rent a catamaran... makes
for a much pleasant vacation.

Disclaimer: I own a mono. :-)

Well, one simply advises the Captain that the crew will be limited to
a single "tee" shirt and pair of shorts. Keeps the weight down and
also restricts the use of fresh water, don;t you know?

Bruce-in-Bangkok
(correct email address for reply)


I have tried this several times, and the women just won't go for it.

--
"j" ganz @@
www.sailnow.com

"JimC" wrote in message
...
I absolutely have evidence that a dismasting will cause a capsize in
heavy seas. Pulling a boat over is quite, quite different than being on
the ocean in heavy seas. Is there some evidence you would like to present
that shows this isn't true? Have you ever been in a boat rolling from
side to side in ocean conditions?

Yes.

I have.

So, what did you experience? Do tell. Certainly, this wasn't on your Mac.

So, you're saying that because a boat supposedly will continue to float
means that it won't capsize over and over? Perhaps you should read
Fastnet Force 10, and get back to us. That's exactly what happened to
several boats. They continued to float, yet rolled over and over to the
point where the crews abandoned them (to their peril).

Did I say that? - (Nope.) But so far, you haven't provided evidence that a
Mac, with a sea anchor deployed, would roll over and over again. You said
that it would several times (over and over again) but you didn't support
your assertions.

I haven't presented any evidence that the moon revolves around the Earth
either. Do I need to support my assertion that it does?

You're assuming a situation that likely will not be possible after a
dismasting with someone trying to stay on a boat that is totally
unstable. That's a pretty weak assumption.

From your last statement, it's pretty clear that you don't know much
about boats. A dismasting in and of itself, doesn't cause a sinking.

Did I say that? Don't think so.

Capt, this entire string revolves around slamming the Macs. - Check out
Neal's original post.

My mistake. It *is* about your Mac!


--
"j" ganz @@
www.sailnow.com

wrote in message
...

You can stop right there. There is no attachment point on a Mac26m
that is anywhere near strong enough to attach a sea anchor.




How about around his thick head?

--
"j" ganz @@
www.sailnow.com

"Capt. JG" wrote in message
news:WISdnRUtNokGEZrVnZ2dnUVZ_oOnnZ2d@bayareasolut ions...
I have tried this several times, and the women just won't go for it.

--
"j" ganz @@
www.sailnow.com



Women don't want sex with girly-men!

--
Gregory Hall

"JimC" wrote in message
...
Assuming the boat can't sink (which I seriously doubt - given the
pounding it would endure, it would likely break up),


--- Any evidence or proof to back up that statement Capt? No?

Is there any proof that if I go after it with a sawsall it'll remain intact?
No.

it would be dismasted for sure.

Any evidence or proof to support that assertion Capt?.... No?

Like I said, you know next to nothing about boats. That is certainly my
assertion, and the proof is what you bought and then claim it's going to do
fine offshore in storm conditions.


Then, (not that sailing would have ever been an option), your only chance
for survival would be below decks, while the boat rolled over and over
and over, perhaps even pitchpolling from time to time.

Any evidence or proof to back up that particular assertion Capt? ....No?

See other thread parts. This is boring.

It would be like being in
a washing machine with heavy and sharp objects. You'd find yourself in a
non-habitable environment of flying hazards including yourself that would
break your bones into mush.

LOL.

Not so funny if you happen to be there.

In desperation to escape, you would vacate the
premises, and then either be thrown off the boat by the wave action or
you would remove yourself from the boat deliberately.


That's fascinating piece of fiction Capt. - Have you considered writing a
novel?

Read it as fact in a non-fiction book... actually several.

Either way, you wouldn't
survive.


Great fiction Capt. Too bad you have no evidence or proof whatsoever to
support it.


Yeah, too bad.




--
"j" ganz @@
www.sailnow.com

cavelamb himself wrote:
Bruce in Bangkok wrote:


Well, I do understand "moment of inertia" but I do not understand how
a rig that when you put it in the water has a negligible effect on
stability, i.e., the boat rights itself, is going to have a major
effect on a boat rolling over.
Now, for argument's sake we are talking about my boat. the mast can be
picked up by four Asians so lets say, for argument's sake it weighs
500 lbs. It is desk stepped and is forty feet long with the spreaders
about half way up the mast.
I can carry one set of shrouds with no problems so say 100 lbs X 2
sets = shrouds = 200 lbs. Four terminate at the spreaders and two at
the mast head. The fore and aft stays probably weigh a little less
then the stays so say 75 lbs together, both terminating at the mast
head.

The boat displaces 12,000 lbs. It was built in 1971, sailed across the
Pacific Ocean, among other places and hasn't rolled over to date.

It would be a kindness for you to explain it to me the real life
dynamics that will cause my rig to make my boat to roll over.



Bruce-in-Bangkok
(correct email address for reply)






http://en.wikipedia.org/wiki/Metacenter


Just go study the wiki page.
It's a pretty clear explanation.

Capt. JG wrote:

"JimC" wrote in message
.. .

I absolutely have evidence that a dismasting will cause a capsize in
heavy seas. Pulling a boat over is quite, quite different than being on
the ocean in heavy seas. Is there some evidence you would like to present
that shows this isn't true? Have you ever been in a boat rolling from
side to side in ocean conditions? I have.-

But do you have evidence that a dismasted M26 would roll over in heavy
seas? - That happens to be the issue of this particular discussion.


Nope. I also don't have evidence that cockroaches are smarter than
elephants. So, back at you... do you seriously believe that a dismasted boat
is stable in heavy seas? Because that's the real discussion whether or not
you choose to acknowledge it.

Actually, that's not the "real discussion." My initial comments related
to my contention that, had Joe been in a Mac 26M, his boat would have
remained afloat. Whether or not he would still want to call the CC, in
view of his wife's condition, is another issue. In either case, he
wouldn't have lost his boat. And had he elected to stay on the boat, he
wouldn't have sunk when the boat sank.





So, you're saying that because a boat supposedly will continue to float
means that it won't capsize over and over?

Did I say that? Don't think so.


You pretty much did in your previous comment. You should read what you
write. It's a gas.

Not nearly as interesting as the sensationalized fiction you have bee
posting Capt.



Perhaps you should read Fastnet
Force 10, and get back to us. That's exactly what happened to several
boats. They continued to float, yet rolled over and over to the point
where the crews abandoned them (to their peril).

You're assuming a situation that likely will not be possible after a
dismasting with someone trying to stay on a boat that is totally
unstable. That's a pretty weak assumption.

Your comments regarding the instability of dismasted boats apparently
assumes that, with the mast, the crews would have been able to keep
their boats stable by reducing, possibly heaving to. But in heavy seas
such as those Joe described (the conditions observed several hours prior
to the CC rescue), it seems likely that a boat would not stay on course
when hoved to. For example, when the boat was below the waves, the winds
would be erratic, and the boat would wander about unpredictably, ready
to be broad sided by the next wave. As stated above, I personally think
it would be wiser to deploy a sea anchor and forget about trying to
heave to. But in any case, you don't have evidence or proof that one or
both of these tactics would be for a boat in the situation Joe
described. You also don't have evidence or proof that a Mac 26 would
roll and roll and roll if a sea anchor were deployed, whether or not it
was dismasted. In any case the boat has floatation that would keep it
afloat, which would be preferable to being pulled to the bottom by a
heavy keel in a boat with no floatation.


Again, do you have any evidence (other than anecdotes, hearsay, or
speculation) that the Mac 26Ms typically become "totally unstable" in such
conditions? No? I didn't think so.


As I said. You're now claiming that the Mac is somehow a special case. Yes,
I know so.

Obviously so. The design of the Mac26M IS different from that of a
conventional boat with weighted keel and no positive floatation.




From your last statement, it's pretty clear that you don't know much
about boats.

It's even more clear that you know nothing about the most basic
principles of evidence and logic. - You have none, yet you can't seem to
recognize it, much less admit it.


A dismasting in and of itself, doesn't cause a sinking.

Once again, did I say that? Don't think so.


You don't know much about boats...


And, as noted above, you know nothing about the basic principles of
evidence and logic. - You have none, yet you can't seem to understand
that fact, much less admit it.




clearly, and I do think so.





If the boat

is water-tight, a relatively straightforward thing to do, then the boat
won't sink. The interior will become untenable, however, pretty quickly.
I love it... "as unpleasant as that would be." Now that's truly funny.
Keep at it Jim, you're providing lots of cheap laughs, again proving my
point... QED.

You seem to think that I'm slamming that piece of garbage Mac in this
post. I'm not man..... LOL


So you're not slamming the Macs after all Capt? Really? - You certainly
had me fooled.


Well, that's apparently pretty easy to do!

Feel free to show us some empirical evidence that a Mac will not roll,
capsize, and kill anyone stupid enough to be in the conditions previously
described. Nope, didn't think you could.



Capt., I didn't start this particular discussion thread, but since I'm
one of the few Mac owners on the ng, I feel some obligation occasionally
to provide a degree of balance and rationality to such discussions. Keep
in mind that I didn't claim that the Mac would be preferable to other
boats for extended ocean crossings, or that it doesn't have limitations
or shortcomings. - I merely stated that, with it's floatation system, I
thought it would have remained afloat under the conditions Joe
described. The original note in this string (and subsequent ones such
as yours) simply assumed that negative, sarcastic comments about the Mac
would of course be accepted as the Gospel truth. What I have done is
simply to point out that most of such assertions about the Mac 26M are
not supported by evidence or proof, but instead consist largely of
hearsay, speculation, and personal bias.

Jim

Capt. JG wrote:

"Bruce in Bangkok" wrote in message
...

I absolutely have evidence that a dismasting will cause a capsize in
heavy
seas. Pulling a boat over is quite, quite different than being on the
ocean
in heavy seas. Is there some evidence you would like to present that
shows
this isn't true? Have you ever been in a boat rolling from side to side
in
ocean conditions? I have.-


Jim

Are you stating specifically that a sailing boat that loses its mast
is in more danger of capsizing then when the rig was in place?? I
would appreciate it if you could elaborate on this as it was always my
understanding that once the rig was either cut away or retrieved and
lashed on deck the boat rode no worse then it had with the rig in
place.

It was always my thought that once the rig was gone that stability of
the ballasted hull would become slightly better with no weight above
the deck line.

I emphasize that I have no interest in this discussion other then this
single point which is probably of interest to most cruising sailors.


Bruce-in-Bangkok
(correct email address for reply)



If it was bare poles, then no as far as absolute stability goes, but in
storm conditions, the generally accepted best method of survival is to heave
to, rather than lying ahull.

Capt., I don't think that heaving to is the "generally best method of
survival" in storm conditions. For example, as pointed out in the
Annapolis Book of Seamanship, Heaving-to leaves a boat vulnerable to
steep breaking waves, so it is not the best tactic early in the storm or
in an exceptional storm. As also stated in the Annapolis work, different
methods may be preferred under different conditions, and for different
boats. - For example: "Discussions of storm tactics often stray into
debates about families of drag devices. In their quest for absolute
answers, many participants (Capt?) in these heated arguments choose one
device and damn the other, studiously ignoring the fact that there is
nothing aboluste even about a storm at sea. Conditions are constantly
changing... Different tactics and gear work best at different stages and
on different types of boats."

Because of it's light weight, my opinion is that the Macs would do
better with a storm anchor (as previously stated) rather than being hove
to or under a reefed sail plan.



Despite Jim's rather bizarre assumptions about survivability in a Mac in
heavy seas, the discussion did get me thinking about rigging.

In other words, you're backing off your previous dogmatic position...


Seems to me it
would not make the boat more stable than under bare poles due to weight
aloft and no sails for stability, but the rigging would resist or at least
dampen a 360 roll... probably just one time around.

Dismasting would reduce the inertia of a boat when rolling in one
direction or the other, and would therefore lessen the forces acting
against the forces opposing it, e.g., the "boat-righting" forces exerted
by the keel or ballast. Permitting the keel or ballast to more
efficiently resist a knock-down or complete roll.


If what I wrote was interpreted to imply that one would simply have bare
poles vs. being dismasted (as thought that would be much of a choice), it
was not my intention - I suppose Jim will be bitter, sorry for the political
pun -- I was always thinking that if I can put any kind of sail up, that'll
be an advantage, which is why they make storm sails.... heaving to, making
some progress vs. being at the mercy of whatever comes your way.

Why not accept the position suggested in the Annapolis text? - That is,
the best solution may depend on the particular conditions and the
particular boat. But under severe storm condidions, heaving to is not
recommended.

Jim