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  #11  
Old 04-06-2011
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First, the strength of knots depends a good bit on the SPECIFIC rope type, so let's just agree that all of the data is probably correct. Have done strength testing on knots and sewwing and there is a lot of varability due to materials.

Second, plenty of folks never use splices; mountaineers, for example. Ropes that are well-sized almost NEVER break in the knots; it is chafe and cutting that gets them.

Another knot to consider is the figure-8 with back trace:

Sail Delmarva: Tired of splicing? Substitue a 90% Strength Knot..

Not too bad to untie unless really loaded hard and 85-90% strength. Absolutely reliable.

There are many other good choises.

There are at a few reasons to use knots in place of splices:
* Splicing used braided rope can be impossible and probably weakens it. Which leads to...
* A knoted halyard is easy to renew; just trim a few feet and retie.
* Splices can jam in some blocks.
* Knoted ropes are much easier to untangle than spliced ropes. On some tackles this is reason enough.

Not to say splices don't have their places; they certainly do. Try running a knot through a windlass.
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  #12  
Old 04-06-2011
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Addressing Paul's comment, frequently rope selection is not based exclusively on breaking strength -- knotted or single line breaking strength -- since the strength of modern ropes frequently would allow selection of a rope smaller than can comfortably handled. Additionally, stretch resistance is a determant when selecting rope for halyard, guys, and spinnaker sheets.
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  #13  
Old 04-06-2011
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Quote:
Originally Posted by Minnewaska View Post
Holy probabilities, Batman!!! A test of sailing stuff with replicates!!! What is this world coming to?

Now, if they would just have presented their stats properly....sigh....well, at least it's a start.
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  #14  
Old 04-06-2011
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Originally Posted by SlowButSteady View Post
Now, if they would just have presented their stats properly....sigh....well, at least it's a start.
What was wrong with their representation? I mean, if you're going to complain about something, why not the tiny sample size?
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Old 04-06-2011
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Quote:
Originally Posted by AdamLein View Post
What was wrong with their representation? I mean, if you're going to complain about something, why not the tiny sample size?
When I teach BioStatistics I spend about two and a half lectures (almost an entire week of class) on data presentation, so I could give you a pretty long list of the errors made in the presentation cited.

But, to start (since you ask):

- "Figures" 1, 2, and 3 are tables, not figures
- Standard Errors (in addition to Standard Deviations) should be given, as we are interested in a comparison of means
- Units should be SI, not American/English customary (however, engineers never seem to understand this)
- The Abstract is a disaster (don't get me started)
- The Equipment and Methods sections (essentially analogous to a "Materials and Methods" section of a standard format scientific paper) should be expanded with greater detail
- Figures (and Tables) are presented but not cited in the text
- Figure 8 is presented as if the different knots have some ordinal relationship, which they do not.
- Figures are inconsistent as to orientation (strength is scaled horizontally in Figs. 4 - 7 and vertically in Fig. 8)
- Fig. 7 is redundant, it simply repeats means presented in Figs. 4 - 6
- All of the figures present means, yet none have error bars (SD or SE)
- Differences in knot breaking strength, as it relates to material strength, are discussed (albeit briefly) without any tests of statistical significance
- And (one of my pet peeves), the word "data" is the plural of "datum". Therefore, "the data was" is grammatically somewhat akin to saying, "the cows was," (and sounds like fingernails on a chalkboard to Yours Truly)

As to the small sample size; it's actually probably OK for such a study. The variation about the mean here appear small enough that increasing the replication would probably not change the over-all results enough to worry about.
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Old 04-06-2011
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Quote:
Originally Posted by SlowButSteady View Post
When I teach BioStatistics I spend about two and a half lectures (almost an entire week of class) on data presentation, so I could give you a pretty long list of the errors made in the presentation cited.

But, to start (since you ask):

- "Figures" 1, 2, and 3 are tables, not figures
- Standard Errors (in addition to Standard Deviations) should be given, as we are interested in a comparison of means
- Units should be SI, not American/English customary (however, engineers never seem to understand this)
- The Abstract is a disaster (don't get me started)
- The Equipment and Methods sections (essentially analogous to a "Materials and Methods" section of a standard format scientific paper) should be expanded with greater detail
- Figures (and Tables) are presented but not cited in the text
- Figure 8 is presented as if the different knots have some ordinal relationship, which they do not.
- Figures are inconsistent as to orientation (strength is scaled horizontally in Figs. 4 - 7 and vertically in Fig. 8)
- Fig. 7 is redundant, it simply repeats means presented in Figs. 4 - 6
- All of the figures present means, yet none have error bars (SD or SE)
- Differences in knot breaking strength, as it relates to material strength, are discussed (albeit briefly) without any tests of statistical significance
- And (one of my pet peeves), the word "data" is the plural of "datum". Therefore, "the data was" is grammatically somewhat akin to saying, "the cows was," (and sounds like fingernails on a chalkboard to Yours Truly)

As to the small sample size; it's actually probably OK for such a study. There variation about the means here appear small enough that increasing the replication would probably not change the over-all results enough to worry about.
Wow, I feel dumb after reading this! Good stuff!
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Old 04-06-2011
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This is a mere minor detail to me..
Seeing that I've been splicing sense Norah was a cabin boy. I'll just go ahead and splice it. And if the line is solid single braid I will put a couple of seizings on it and not worry about minor details.
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Old 04-06-2011
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Quote:
Originally Posted by SlowButSteady View Post
- "Figures" 1, 2, and 3 are tables, not figures
- Standard Errors (in addition to Standard Deviations) should be given, as we are interested in a comparison of means
- Units should be SI, not American/English customary (however, engineers never seem to understand this)
- The Abstract is a disaster (don't get me started)
- The Equipment and Methods sections (essentially analogous to a "Materials and Methods" section of a standard format scientific paper) should be expanded with greater detail
- Figures (and Tables) are presented but not cited in the text
...
- Figures are inconsistent as to orientation (strength is scaled horizontally in Figs. 4 - 7 and vertically in Fig. 8)
- Fig. 7 is redundant, it simply repeats means presented in Figs. 4 - 6
- All of the figures present means, yet none have error bars (SD or SE)
- Differences in knot breaking strength, as it relates to material strength, are discussed (albeit briefly) without any tests of statistical significance
- And (one of my pet peeves), the word "data" is the plural of "datum". Therefore, "the data was" is grammatically somewhat akin to saying, "the cows was," (and sounds like fingernails on a chalkboard to Yours Truly)
And I thought I was a stickler for presentation :P

Quote:
- Figure 8 is presented as if the different knots have some ordinal relationship, which they do not.
Okay, you have a point with this one. That's really grating.

Quote:
As to the small sample size; it's actually probably OK for such a study. There variation about the means here appear small enough that increasing the replication would probably not change the over-all results enough to worry about.
Then maybe it was okay that they didn't include error bars

Anyway if that sort of thing is like fingernails on chalkboards, try this one on for size: My battery's have a "capacity" of 170 amp's.
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  #19  
Old 04-06-2011
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Quote:
Originally Posted by AdamLein View Post
And I thought I was a stickler for presentation :P
Well, as I said, you asked.

Quote:
Originally Posted by AdamLein View Post
Then maybe it was okay that they didn't include error bars
Nope. The author (with the title of "Technical Director", no less) is presenting means. A mean is an estimation of some sort of theoretical value, in this case breaking strength. It is NEVER acceptable to present a mean w/o an estimation of the error (e.g., variation) about that mean.

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Originally Posted by AdamLein View Post
Anyway if that sort of thing is like fingernails on chalkboards, try this one on for size: My battery's have a "capacity" of 170 amp's.
My ears!!! My ears!!!

OK, which is worse: "My battery's have a "capacity" of 170 amp's" or "The harbor isn't far, only about 3 knots from here" ????
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  #20  
Old 04-06-2011
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Originally Posted by SlowButSteady View Post
OK, which is worse: "My battery's have a "capacity" of 170 amp's" or "The harbor isn't far, only about 3 knots from here" ????
Aside from my creative syntactical choices, I'd say they are isomorphic

also: xkcd: Significant
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