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

On Tue, 15 Apr 2008 07:20:21 -0500, Brian Whatcott
wrote:

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

Certainly the weight of the rig slows the roll speed by some figure
but whether it has an effect on the boat rolling over I seriously
doubt. I have had the spreaders in the water (not on purpose, I might
say) and the boat popped right back up. I don't believe that a
properly designed sail boat will roll over except when it is overcome
with a breaking wave and the boat effectively falls down the face of
the wave.

This assumes some mediocre level of seamanship, i.e., not full sails
in a typhoon....

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

On Tue, 15 Apr 2008 20:41:41 +0700, Bruce in Bangkok
wrote:
/snip/
There are conflicting factors (as usual): the pro-stability factor is
the considerable mass far from the roll center (called moment of
inertia) /snip/

Certainly the weight of the rig slows the roll speed by some figure
but whether it has an effect on the boat rolling over I seriously
doubt.
/snip/
Bruce-in-Bangkok

This is not the first time that you have not quite understood an
engineering input, but felt comfortable about doubting it.
The concept is "second moment of inertia" Bruce, not mass.

Easy to look up though.....

Brian W

On Apr 16, 4:10 pm, Brian Whatcott wrote:
The concept is "second moment of inertia" Bruce, not mass.

Hmmm. I think mass moment of inertia is what you're after (http://
en.wikipedia.org/wiki/Moment_of_inertia). Second moment of inertia is
form stiffness (eg. the "I"'s in a mast section description).

-- Tom.

On Wed, 16 Apr 2008 21:10:11 -0500, Brian Whatcott
wrote:

On Tue, 15 Apr 2008 20:41:41 +0700, Bruce in Bangkok
wrote:
/snip/
There are conflicting factors (as usual): the pro-stability factor is
the considerable mass far from the roll center (called moment of
inertia) /snip/

Certainly the weight of the rig slows the roll speed by some figure
but whether it has an effect on the boat rolling over I seriously
doubt.
/snip/
Bruce-in-Bangkok

This is not the first time that you have not quite understood an
engineering input, but felt comfortable about doubting it.
The concept is "second moment of inertia" Bruce, not mass.

Easy to look up though.....

Brian W

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)

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

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.

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/

"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. :-)


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

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)