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Go Back   SailNet Community > On Board > Boat Review and Purchase Forum > Sailboat Design and Construction > Limit of Positive Stability (LPS)
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Thread: Limit of Positive Stability (LPS) Reply to Thread
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Topic Review (Newest First)
03-23-2014 02:09 PM
captain jack
Re: Limit of Positive Stability (LPS)

Quote:
Originally Posted by bobperry View Post
Jack:
I think you look at any number you can find on your bat. Don't put to much importance on any one number. Look for numbers that jump out at you as being out of whack and investigate why. For instance if your boat had an AVS of 100 degs you may want to take a look at why the number is so low. Seaworthyness can't be represented as a number.
that is the picture i am getting from the posts in this thread.

Quote:
Your Cal 27 AVS is right on textbook "normal" but it is a very static number derived from contrived static conditions that absolutely have no similarity to the dynamic situation you would be in when you could be heeled that far. In all ways your boat is very "normal" and I would not worry at all about it's seaworthyness if it is well kept.
that's good to hear. i just bought this boat and there isn't really much of anything that you can find, on line, about it's characteristics. in prior years, i did my sailing on a largish lake in Pa. in my dinghy, i was the only one at risk. and i was never in a situation where i was worried about my holiday 20, even when the wind got up. now i sail in the chesapeake bay. when i am in the dinghy, i am the only one at risk but, my girlfriend ( who has never been in any boat before ) will be sailing with me, on the cal, and i am responsible for her safety. the bay is known for sudden bad conditions so, seaworthiness of the 'new' boat is a concern.

Quote:
For my money tender and stiff refer to a boat's overall stability characteristics and not initial stability. However, initial stability would be part of that picture.
thanks for your input
03-23-2014 09:41 AM
bobperry
Re: Limit of Positive Stability (LPS)

Jack:
I think you look at any number you can find on your bat. Don't put to much importance on any one number. Look for numbers that jump out at you as being out of whack and investigate why. For instance if your boat had an AVS of 100 degs you may want to take a look at why the number is so low. Seaworthyness can't be represented as a number. I think it's more about you than the boat.

Your Cal 27 AVS is right on textbook "normal" but it is a very static number derived from contrived static conditions that absolutely have no similarity to the dynamic situation you would be in when you could be heeled that far. In all ways your boat is very "normal" and I would not worry at all about it's seaworthyness if it is well kept.

For my money tender and stiff refer to a boat's overall stability characteristics and not initial stability. However, initial stability would be part of that picture.
03-23-2014 12:35 AM
captain jack
Re: Limit of Positive Stability (LPS)

i have a question....
Quote:
Both the Capsize Ratio, and the Motion Comfort Index have pretty much been discredited in that the neither contain the factors now known to be primary determinants in the likelihood of a capsize or motion comfort. In other word, they tell you nothing useful about your boat.

Respectfully,
Jeff
as i said, i have heard this argument made, and i have heard it argued against, on other blogs.

the question this raises, at least for people trying to figure out how seaworthy their boats are, is this: if these ratios are not a valid way to gauge the seaworthiness of your boat, how does a person figure out how seaworthy his boat, or a boat he intends to buy, really is? does the AVS give enough insight into the issue?

by the way, the AVS of my recently purchased 1971 cal 27 is supposed to be 125.04.
03-22-2014 11:31 PM
captain jack
Re: Limit of Positive Stability (LPS)

Quote:
Originally Posted by bobperry View Post
I like kids.
Who else are you going to talk to who just sailed a brand new 63' that he designed for the very first time today?

Waiting,,,,,waiting,,,,,, Me!
That's the answer, me.
Don't you just love that?
that is pretty cool.
03-22-2014 10:39 PM
bobperry
Re: Limit of Positive Stability (LPS)

I like kids.
Hire them while they still know everything.

Jack, I think it's time you considered just sitting and listening for a while. It's good to read. It's even better to experience. You are not ready to pontificate yet. Maybe in 20 years. Ok, I'll give you the benefit of the doubt, 15 years. But for now, do yourself a favor and listen to the old farts. I do. It's a lot of fun. Who else are you going to talk to who just sailed a brand new 63' that he designed for the very first time today?

Waiting,,,,,waiting,,,,,, Me!
That's the answer, me.
Don't you just love that?

I don't read.
I do.
I used to read but real experience is so much more tactile.

You can call me all those names that I have been called so many times before, arrogant is one of the nice ones. But I do not give a rip. Not a wee rip. The good news is that I am willing to muck in and try to learn along with the rest of the SN crew so we can all be smarter at this sailing thing.

So,, bring up any subject you like. Let us kick it around. I'll bet we all come away smarter.

My wife is due home from her ski weekend any minute. She will reduce me to her humble servant. But I'm a Cancer. I like housework. I like a neat and tidy house. I have to go now and turn the record over. Furtwangler doing Schumann's 2nd. Nazi stuff but enjoyable.
03-22-2014 10:12 PM
captain jack
Re: Limit of Positive Stability (LPS)

Quote:
Originally Posted by bobperry View Post
Jack:
Not so funny. Seems like it was only 47 years ago.
yeah. i know. you have a few years on me( i am only 44 )but the years are flying by so fast.....it's actually pretty freaky.
03-22-2014 09:14 PM
bobperry
Re: Limit of Positive Stability (LPS)

Jack:
Not so funny. Seems like it was only 47 years ago.
03-22-2014 09:11 PM
captain jack
Re: Limit of Positive Stability (LPS)

Quote:
Originally Posted by bobperry View Post
Jack:
I'm just another guy who likes boats who has been working with them professionally for the past 47 years. Some stuff does rub off in 47 years. Treat me like any other opinionated know it all.
that's funny 47 years is a long time.
03-22-2014 07:07 PM
bobperry
Re: Limit of Positive Stability (LPS)

Jack:
I'm just another guy who likes boats who has been working with them professionally for the past 47 years. Some stuff does rub off in 47 years. Treat me like any other opinionated know it all.
03-22-2014 05:05 PM
captain jack
Re: Limit of Positive Stability (LPS)

Quote:
Originally Posted by hellosailor View Post
"as defined within English speaking ship and boat design community, by definition tender and stiff only refer to form stability."
So, where do dynamic stability and inherent stability factor into form stability?

As best I can recall, tender and stiff have always been used to refer to the overall stability of a vessel, without regard to when or how the vessel was heeling. Have I just been reading/hearing too many sloppy authors?
it's really funny how the way different people use different words can really affect the way we understand what is being said....and there is a huge tendency for people to use words in slightly different ways.

i have always heard tender and stiff used in relation to initial stability. so, when i hear them, that's what i think of. you get a completely different meaning from those words. you'd think that the existence of dictionaries that standardize the meanings of words would eliminate such different interpretations but, it doesn't seem to work that way in very many situations.

i used to have this thing about how many different meanings can be conveyed with the word 'yeah', based solely on how it was said. there's tons of different meanings such a small word can convey.
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