Michael Daly wrote:
On 16-Jun-2005, Peter wrote:


boats that are 18' long overall will almost
always have waterline lengths greater than boats that are 14'


Fine, but we were comparing kayaks that were only a foot and a half or
so different in length.

Your previous statement: "there is no correlation between overall length
and waterline length in kayaks" made no such distinction that it only
applied to some set of kayaks that all had about the same length, nor
was it limited to sea kayaks.

Of the 105 kayaks on the web page of Sea
Kayaker data, the average length is 5.2m (17 ft) with a standard deviation
of 41cm (16 in). 78% of the kayaks fall within one standard deviation of
the mean length. We're not talking about huge differences in length
typically, especially since the standard deviation is comparable to the
differences in LOA and LWL.


but it is very high (correlation coefficient is probably around 0.95).


Instead of pulling these numbers out of your ass, how about some facts?

Based on the data I posted on 18 kayaks (showing percent differences
in LWL and LOA), the actual correlation coefficient is 0.79.

Naturally the correlation coefficient will be less if you restrict the
kayaks under consideration to ones with fairly similar lengths (all but
one in the range from 16' to 19'). In a more complete list with play
boats, WW boats, surfskis, etc. also included the coefficient would be
much higher. Since your original statement just referred to the general
category "kayaks" my estimate was based on this broader selection.

However, a correlation coefficient of 0.79 is a far cry from your
original claim that there is "no correlation" which would imply a
correlation coefficient of 0. The numbers in this case are much closer
to perfect correlation than they are to no correlation.

In the reference to statistical terms I cited earlier, any correlation
coefficient of 0.5 or higher is regarded as "high" (0.1 - 0.3 is small,
0.3 - 0.5 is moderate) and greater than 0.7 is "very high."

Not exactly
tight.

Even taking your specified subset of kayaks, the correlation is "very
high" rather than your original statement that it is nonexistent.

snip

So, like, shorter boats are slower eh?

Sheesh, how do you guys decide what to order for lunch? Must take hours.

On 16-Jun-2005, "Keenan & Julie" wrote:

So, like, shorter boats are slower eh?

Not always - that's the point of this discussion.

Mike

in article , Michael Daly at
wrote on 6/16/05 4:58 PM:


On 16-Jun-2005, "Keenan & Julie" wrote:

So, like, shorter boats are slower eh?

Not always - that's the point of this discussion.

Mike

So, like, sure, a shorter boat shaped like a cigar is probably faster than a
longer boat shaped like a square, eh?

But bravado and mensa-style chest-thumping aside, is it not flippingly
obvious that longer boats are fast than shorter boats if they otherwise
share the same design characteristics?

i initially thought michael was nit-picking a bit... but, in matters
technical, i've found he is worth listening to... after all of this,
i'm with him...

although, keenan, i think you're quite right when you assert "a shorter
boat shaped like a cigar is probably faster than a longer boat shaped
like a square"... too right!

in article , BCITORGB at
wrote on 6/17/05 10:05 PM:

i initially thought michael was nit-picking a bit... but, in matters
technical, i've found he is worth listening to... after all of this,
i'm with him...

although, keenan, i think you're quite right when you assert "a shorter
boat shaped like a cigar is probably faster than a longer boat shaped
like a square"... too right!

LOL. I think I'm just not understanding that people actually enjoy arguing
about such things. When it comes to paddling I'm more interested in what
people see or do while paddling than whether or not you can go .000032
seconds faster depending on whether or not you wax your boat.

There's more to the simple truth of this matter than cigar vs square. If the
damned boat is the same design only longer, it goes faster.

If the boats are of different design, then obviously the difference in
design is going to have to be taken into account, not just the length.

Beyond that this whole discussion sounds like geeks on steroids to me.

Keenan or Julie wrote:

[...]
If the damned boat is the same design only longer, it goes faster.

Depending on the power of the 'engine', it could as well go
slower...

Beyond that this whole discussion sounds like geeks on steroids to
me.

Perhaps, but if you choose a longer boat with the illusion that it
goes faster while in reality it will only make you work harder or go
slower, that persons will need the steroids or may be quite
disappointed.

Waxing the boat will make it go slower as the wax will repel the thin
layer of water called "Laminar layer". Laminar flow must be maintained
for the layer to make proper contact along the hull to form a so called
slip stream. Only way to do this is to compound or wet sand the hull to
make the laminar layer stick to the hull surface.

Also, compare long boat to short boat. 13'2" race boat can attain, make
many more moves than a short boat. Hense, make far more use of the river
than any drop and spin boat that only sits in holes throwing ends.

Keenan & Julie wrote:
in article , BCITORGB at
wrote on 6/17/05 10:05 PM:


i initially thought michael was nit-picking a bit... but, in matters
technical, i've found he is worth listening to... after all of this,
i'm with him...

although, keenan, i think you're quite right when you assert "a shorter
boat shaped like a cigar is probably faster than a longer boat shaped
like a square"... too right!


LOL. I think I'm just not understanding that people actually enjoy arguing
about such things. When it comes to paddling I'm more interested in what
people see or do while paddling than whether or not you can go .000032
seconds faster depending on whether or not you wax your boat.

There's more to the simple truth of this matter than cigar vs square. If the
damned boat is the same design only longer, it goes faster.

If the boats are of different design, then obviously the difference in
design is going to have to be taken into account, not just the length.

Beyond that this whole discussion sounds like geeks on steroids to me.

On 16-Jun-2005, Peter wrote:

Your previous statement: "there is no correlation between overall length
and waterline length in kayaks"

From a perspective of useful information, that is still true. You can argue
semantics all you want, but sea kayak lengths (LOA and/or LWL) are all over
the place.

made no such distinction that it only
applied to some set of kayaks that all had about the same length, nor
was it limited to sea kayaks.

But for the fact that the discussion is about sea kayaks. I guess you
just forgot.

Naturally the correlation coefficient will be less if you restrict the
kayaks under consideration to ones with fairly similar lengths (all but
one in the range from 16' to 19'). In a more complete list with play
boats, WW boats, surfskis, etc. also included the coefficient would be
much higher.

WW boats? You're joking, right? They have even more variation in LOA
vs LWL.

I made no such restriction on lengths, I merely took the data that was
available and since we are discussing se kayaks, that's the data I used.

It still remains that overall length is not a useful indicator of
performance.

Mike

Michael Daly wrote:

On 16-Jun-2005, Peter wrote:


Your previous statement: "there is no correlation between overall length
and waterline length in kayaks"


From a perspective of useful information, that is still true.

No, it clearly was never true. Even taking the subset of kayaks you
chose, you calculated a correlation coefficient of 0.79 indicating a
very high level of correlation. If all kayak types were included the
correlation would be even higher.

You can argue
semantics all you want, but sea kayak lengths (LOA and/or LWL) are all over
the place.


made no such distinction that it only
applied to some set of kayaks that all had about the same length, nor
was it limited to sea kayaks.


But for the fact that the discussion is about sea kayaks. I guess you
just forgot.


Naturally the correlation coefficient will be less if you restrict the
kayaks under consideration to ones with fairly similar lengths (all but
one in the range from 16' to 19'). In a more complete list with play
boats, WW boats, surfskis, etc. also included the coefficient would be
much higher.


WW boats? You're joking, right? They have even more variation in LOA
vs LWL.

Not joking at all. In a compilation of all kayaks, the play boats and
WW boats will have short LOA and LWL figures, the surfskis will have
long LOA and LWL figures, and sea kayaks will come in in between. The
overall correlation coefficient between LOA and LWL will be very high.

I made no such restriction on lengths, I merely took the data that was
available and since we are discussing se kayaks, that's the data I used.

It still remains that overall length is not a useful indicator of
performance.

I have two sea kayaks. One has an overall length of 11' 8" and the
other has an overall length of 17' 6". I bet you can tell already which
one has a higher top speed - and you'd be right. Seems to be a pretty
useful indicator.

In the particular case of the two kayaks considered by the OP, their
lengths only differed by about 2' but the hull shapes appear to be quite
similar with no obvious difference in overhang. Therefore it's highly
likely that the Biscyne which is longer overall will also have a longer
waterline length.