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Old 01-09-2012, 07:52 PM   #41
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RE: Paper Charts

Quote:
RickB wrote:markpierce wrote:
*a flying bridge raises the boat's center of gravity*so reducing a boat's stability.*
Not necessarily a negative thing.* Adding a flying bridge or standing up there will reduce the rate of roll, make the boat ride better, and make it less likely that someone will be "thrown off" the deck or the bridge.

There is a lot more to stability than the KG.

*Right you are Rick!
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Old 01-09-2012, 08:03 PM   #42
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RE: Paper Charts

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markpierce wrote:I'm sure I was a lot more comfortable*with a cabin*on the fourth deck rather than the eleventh while 50-something-foot waves were hitting broadside.**
I'm sure you were but what has that got to do with anything?

You would probably have had a stroke if you knew that they reduced what you call stability on that floating hotel so the decks wouldn't be awash in barf.

That thing had less "stability" than your own boat. The GM was probably around a foot. Let us know what yours is.
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Old 01-09-2012, 08:03 PM   #43
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RE: Paper Charts

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Nice little boat in Bellingham. **Sorry Mark, but I had to do it.*
I showed Mark some photos of that boat when his Coot was under construction.* Turns out it's owned by a fellow who during the summer*teaches courses in the PNW*aimed at getting master's licenses and such.* The boat is*his office.* He's been wintering it in that same spot for a year or two now.
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Old 01-09-2012, 08:05 PM   #44
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RE: Paper Charts

Quote:
Carey wrote:RickB wrote:markpierce wrote:
*a flying bridge raises the boat's center of gravity*so reducing a boat's stability.*
Not necessarily a negative thing.* Adding a flying bridge or standing up there will reduce the rate of roll, make the boat ride better, and make it less likely that someone will be "thrown off" the deck or the bridge.

There is a lot more to stability than the KG.

*Right you are Rick!

*If this is so, why don't sailboats have ballast in their masts rather than the keels?
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Old 01-09-2012, 08:08 PM   #45
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RE: Paper Charts

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RickB wrote:
That thing had less "stability" than your own boat. The GM was probably around a foot. Let us know what yours is.
It's hard to believe from a layman's standpoint*looking at today's*horzontal hotels *that they have any stability at all.* It's my understanding that they have massive active stabilizing systems to keep them relatively level, perhaps even at the dock. :-)
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Old 01-09-2012, 08:09 PM   #46
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RE: Paper Charts

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markpierce wrote: If this is so, why don't sailboats have ballast in their masts rather than the keels?
You have already had enough hints. If you are going to post about stability it is up to you to do your homework..
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Old 01-09-2012, 08:17 PM   #47
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RE: Paper Charts

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Marin wrote:It's my understanding that they have massive active stabilizing systems to keep them relatively level, perhaps even at the dock. :-)
Stabilizers don't add stability, they reduce roll rate for comfort.

The ordinary measure of stability is GM, the distance between the center of gravity and the metacentric height. If the two coincide, the boat is as stable as a beachball. The greater the distance the more stable the boat but the faster the roll ... to the point that things like sat antennae, liferafts, and people start getting flung off the top.

That maritime obscenity or "horizontal hotel" probably had a GM of around a foot after they reduced it as much as prudent in order to keep the self loading cargo from wallowing in puke.
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Old 01-09-2012, 08:18 PM   #48
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Paper Charts

Having fun even if I'm an ignoramous!

*


-- Edited by markpierce on Monday 9th of January 2012 09:19:54 PM
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Old 01-09-2012, 10:55 PM   #49
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RE: Paper Charts

Mark,

Rick is just taking advantage of the fact that he knows something you do'nt. Drawing attention to it makes him look real smart. And about the issue at hand it sounds like he does know a great deal but putting you down dos'nt make him as smart as he looks.

Eric
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Old 01-10-2012, 01:08 AM   #50
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RE: Paper Charts

Quote:
Marin wrote:RickB wrote:
That thing had less "stability" than your own boat. The GM was probably around a foot. Let us know what yours is.
It's hard to believe from a layman's standpoint*looking at today's*horzontal hotels *that they have any stability at all.* It's my understanding that they have massive active stabilizing systems to keep them relatively level, perhaps even at the dock. :-)

*Stabilizers on cruise ships are "little wings" underwater.* they work with water flowing over them like air on a plane's wings.* Thus, they don't work while docked, and my understanding is that the stabilizers are withdrawn before docking to reduce potential damage.* Also, the ship stabilizers reduce roll but not pitch.
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Old 01-10-2012, 03:42 AM   #51
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RE: Paper Charts

"If this is so, why don't sailboats have ballast in their masts rather than the keels?"

Interesting that in the Fastnet disaster , they found the boats with heavier rigs survived far better than the light weight rigs.

Seems the moment of inertia , harder to get started and stopped , was a great savior in keeping the mast out of the water.

Most boats that had masts hit the water were left for the life raft.
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Old 01-10-2012, 05:52 AM   #52
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RE: Paper Charts

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nomadwilly wrote:
Rick is just taking advantage of the fact that he knows something you do'nt.
No Eric, I have no "advantage" to gain here or anywhere else. If I wrote a thousand word post telling mark why his concept is flawed it would teach him nothing compared to what he will learn by approaching the subject on his own.

He might be "having fun" but I didn't call him an ignoramous, I gave him hints so he could find his own answers at his own pace rather than continue to post silliness.

I am happy to share information or knowledge. It is a "pay it forward" sort of thing because a lot of talented and skilled people shared their knowledge with me, but I don't have much time for fools and poseurs and I have no reason to try and "look good" to a bunch of people I don't know and will probably never meet and will sure as Hell never make a penny from. Take it or leave it,
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Old 01-10-2012, 06:14 AM   #53
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RE: Paper Charts

Having taught stability at the 100-200 ton masters level (baby licenses but the basics are still the same)*...not sure how adding weight aloft...and not changing ANY other factors would improve stability.* You would be raising the center of gravity and not doing anything to the metacentric height or center of buoyancy....thus reducubg the righting arm.

Granted there are many factors that affect stability and safety...the consensus in my readings that tenderness is never really a good thing.* Plus a*sufficiently long enough roll period is necessary for safe movment around the boat in harsh conditions.

Would love to know why because I'm in the process of redoing my flying bridge.
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Old 01-10-2012, 08:27 AM   #54
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RE: Paper Charts

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psneeld wrote:*...not sure how adding weight aloft...and not changing ANY other factors would improve stability.*
*Who said it did?
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Old 01-10-2012, 09:42 AM   #55
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RE: Paper Charts

Wait, I thought this is a thread on charts?* I'm soooo confused....*
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Old 01-10-2012, 10:16 AM   #56
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RE: Paper Charts

Quote:
RickB wrote:markpierce wrote:
*a flying bridge raises the boat's center of gravity*so reducing a boat's stability.*
Not necessarily a negative thing.* Adding a flying bridge or standing up there will reduce the rate of roll, make the boat ride better, and make it less likely that someone will be "thrown off" the deck or the bridge.

There is a lot more to stability than the KG.

*I understand the weight aloft*will reduce the rate of roll and "possibly make the ride better"... however, when you finished off with the stability statement I couldn't decide exactly how you were connecting the two..
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Old 01-10-2012, 11:07 AM   #57
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RE: Paper Charts

Quote:
nomadwilly wrote:
Mark,

Rick is just taking advantage of the fact that he knows something you do'nt. Drawing attention to it makes him look real smart. And about the issue at hand it sounds like he does know a great deal but putting you down dos'nt make him as smart as he looks.

Eric
*I don't look at it that way.* I want to know when I'm "wrong."*
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Old 01-10-2012, 11:56 AM   #58
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RE: Paper Charts

Quote:
psneeld wrote:*I understand the weight aloft*will reduce the rate of roll and "possibly make the ride better"... however, when you finished off with the stability statement I couldn't decide exactly how you were connecting the two..
KG is the distance between the CG and the keel, if you add weight high on the boat, you*raise G*and bring it closer to the metacenter, M, which is determined not by G but by the location of the center of bouyancy, *B.

Because the distance between a line drawn vertically from*B*to*M defines the righting arm Z, as G rises the distance between G and M (GM) and roll rate decrease and we say that stability has decreased. When G and M coincide the boat is neutrally stable.

the locations of B and M will* begin to move quickly beyond about 10 degrees of roll and at some point (the point of vanishing stability) M will move below G and the boat can capsize. We conduct inclining experiments to determine where stability vanishes. Because different boats have different hull shapes is why I said there is more to stability than the height of the center of gravity above the keel.

I never said raising G increased stability, I said it provided for a better ride due to a slower rate of roll. And that is why I said*decreasing stability is not necessarily a*negative thing.*
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Old 01-10-2012, 11:57 AM   #59
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RE: Paper Charts

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markpierce wrote:*I don't look at it that way.* I want to know when I'm "wrong."*
*Thank you Mark, it was not intended that way either.
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Old 01-10-2012, 12:19 PM   #60
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RE: Paper Charts

Pineapple Girl:

"Wait, I thought this is a thread on charts? I'm soooo confused...."

I'm with you, Girl.* The OP said,

"I use paper charts to double check my Nobletec running on a laptop. I do not update the paper IAW notice to mariners. ...*

My travels are in Washington and British Columbia. Am I in the minority as far as not religiously updating paper charts?"

and no one has responded on topic since page 1.

?

OS*
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