Brian Nystrom ) writes:

While this is certainly what attracts some kayakers, I'd say the main
attractions vs. canoes are the kayaks inherent seaworthiness and it's
ability to handle a broad rain of weather and water conditions with
aplomb.

I'd have to agree that the watertightness of a kayak is its second major
attraction, second only because all kayaks are faster than canoes while
not all kayaks are acquired for watertightness. It would be interesting to
know what proportion of kayak paddlers use spray skirts.

Of course, I'm talking about sea kayaks, rather than recreational or
whitewater boats. I'm also leaving out the class of boats like the
Kruger "canoes", which are canoes in name only and have more in common
with kayaks.

I'm of the opinion that if its paddled with a double bladed paddle, kayak
stlye, then it's a kayak. That includes undecked open "canoes" like the
Rushton Wee Lassie and excludes decked white water and sailing canoes.
It's the paddle, not the deck. One canoe club that TF Jones mentions has
that as a rule in their club races. You can't enter a canoe race with a
kayak paddle. If you want to use a kayak paddle you race with the kayaks.



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Speed VS Horsepower

Here is the data on Mike Daly's website converted into horsepower using a
conversion factor I worked out which gives hp = kt x lb x 0.003072.
I also added the speed in mph using mph = kt x 1.15 for people who
are not used to speed in knots.


Speed
kt mph Endurance Nordcapp Solstice A. Hawk Sonoma Winters
2 2.3 0.006 0.006 0.006 0.006 0.005 0.012
3 3.45 0.019 0.017 0.019 0.018 0.017 0.025
4 4.6 0.044 0.044 0.045 0.044 0.047 0.066
4.5 5.18 0.065 0.073 0.073 0.065 0.096 0.111
5 5.75 0.099 0.124 0.124 0.095 0.179 0.215
6 6.9 0.208 0.265 0.262 0.208 0.266 0.535


comments:

1. 1/20 hp = 0.05 hp which puts an average canoeist (Winters) at about 3.5 mph
and a kayaker at 4.5 mph in a dead calm.

2. an athlete can sustain 1/4 hp = 0.25 hp which puts the athlete
at about 6 mph in a canoe and 7 mph or more in a kayak.

3. a solo paddler can't go 7 mph in a canoe but a canoe can have 2
paddlers and that means more surface friction.

4. to go 7 mph the paddlers in the second fastest pair of kayaks have
to work about 30% harder than the paddlers in the fastest pair of kayaks.

5. it's a shame we don't have the resistance broken down into
friction and wave-making. That would be interesting to examine.


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wait just a darned minute, are you saying the data you presented is not
test data but is calculated from dimensions using Winter's KAPER model?
that's not data. sorry, it doesn't count as data. it doesn't support your
case. I've used Winters' KAEPER model on one of my own boats for fun btu
it's nto measured data, just calculated numbers. I also calculate numbers
with two hull design programs but they are not the same as measurements
from actual in the water tests.

Michael Daly" ) writes:

That's my website and the data was taken from Sea Kayaker magazine
(Kaper results) or from:

http://www.unold.dk/paddling/articles/kayakvelocity.html

which appears to be from SK's Broze/Taylor results. Kaper is John
Winter's old resistance program and has a factor for plastic kayaks
among other things. It's now a public domain algorithm and John
told me he no longer uses it, since a commercial product (can't
remember the name) is more useful for him.

BTW, the following figure shows what I explained in a previous post
but which you claimed was not correct.

http://www.greenval.com/fig3_1.gif

I've seen it. I'm familiar with it. It does not.



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The H20 after the Nordkapps name means "Hatches Two Oval" meaning that both
the front and rear hatches are oval instead of the configuration of the
Nordkapp Jubalee, which had only one (the rear one) hatch oval. Pre 1992 or
93 Nordkapps had only the 7 1/2 inch round hatches

Depending on the year , the Nordkapp ranges from 17 foot 8 inches to about
18 feet




"William R. Watt" wrote in message
...


I found what I was looking for at www.greenval.com/winters.html.
Writing about canoe design for frictional resistance John Winter says ...

"A 5% decrese in wetted surface is worth bragging about, but a
single year's scratches and banging can easily double coefficient
of friction from 0.004 on a new fibreglass canoe to 0.008. This
more than offsets the designer's efforts. The cavalier attitude of
most canoeists towards their boats is evidence that a 50%
resistance increase is not often noticed if only because the onset
of its effect is so gradual."

Earlier I wrote in this online discussion that paddling in a group
would require extra effort to keep up with other members who were
in similar boats with smooth hulls. I only assumed a 10% increase
in frictional resistance. Winters implies a 50% increase is not
unusual. I used performance data from Winters' former website. All
Winters data applies to canoes (at one point he mentions a
"typical" 16 foot canoe) and is provided to illustrate the
principles he is writing about. Its not specific to any boat,
particularly not kayaks.

I was kicked off the computer at the public library after an hour,
but not before taking a look at the kayak data provided by Mike
Daly at http://www.greatlakeskayaker.ca/spee...anceGraphs.htm. I
found the graph very interesting. I've copied down the numbers and
would like to replace the resistance in pounds by the effort in
horsepower when I get a free moment. Of the 5 kayaks, the
Endurance 18 and the Arctic Hawk are equivalent and fastest. I
don't know if they are the same length. However the Nordkapp H20
and the Solstice GT are equivalent and second fastest even though
the Nordkapp is 2 ft longer than the Endurance (if I'm
interpreting the names correctly). Up to a speed of 4 knots all
four of these kayaks are equivalent. The two pairs only begin to
diverge at speeds over 4 knots. The remaining kayak, Sonoma, is
the slowest. Its length is unknown. There is an error in the data
for the Sonoma at the fastest speed, revealed by a sudden change
in its graph. The slowest boat is one for which John Winters
suppled the data and I'm sure it is for a canoe, not a kayak, as
all the Winters data I've seen is for canoes.

Even though the boats I currently paddle are only cheap home made
experimental plywood boats I'm careful not to treat them roughly
and get the hulls scratched and gouged. That is why I was so
disgusted to see the condition of the used rental boats offered at
a recent sale here.

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expanding on what I typed in haste yesterday ...

William R. Watt ) writes:

...I also calculate numbers
with two hull design programs but they are not the same as measurements
from actual in the water tests.

I wrote a computer program which, like KAPER, accepts dimensions and
calauclates areas, volumes, and other numbers. Unlike KAEPER this program
uses analystical geometry to do its calcuations. My program is only for
flat bottom skiffs. It was inspired by a clever geomertical analysis of
teh dory hull by Barend Migchelsen of Dorval, Quebec who developed an
simple, elegant method of designing and buidling dories based on geometry.
This appreoach is pretty accurate. The program I wrote produces a tabel of
offsets which is the usual way boat hulls are described for computer
analysis and for boatbuiling. However, whe I input a table of offsets from
my program into the two hull design program I use there is quite a
variation in the areas (wetted surface) and volumes (displacement)
displayed by all three programs. The bigger the boat the more they
diverge. From 7% on a 12 ft skiff to 17% on a 20 footer. the
discrepenciews arise from the different assumtions and formuale used by
the different programs, adn by the way the two hull design programs accept
teh data. they both interpolate between stations and the both produce
different numbers depending on which order you type in the stations.

The program I wrote is on my website under Boats and Design. It is not in
the public domain but it is open source. Anybody can use it an modify it
so long as they don't attempt to sell the result.

So what I'm saying is design numbers are only a guide to boatbuilding. To
verify the numbers you have to test the boat and collect data. I've always
assumed that Winters' numbers were test data. I've also assumed his KAEPER
program was verified against test data. Often a scaled down model is
tested in a tank but even then there are assumptions made in the scaling
and testing apparatus. I've seen them explained in wind tunnel tests for
sails as well. Failures result when the design, despite teh best efforts,
is not good, and there are failures in real life, some quite expensive.
I'm sure some canoe and kayak designs are not very good despite the use of
computers.

BTW, the following figure shows what I explained in a previous post
but which you claimed was not correct.

http://www.greenval.com/fig3_1.gif

I've seen it. I'm familiar with it. It does not.

in your previous post you claimed minimal total hull resistance occurs
when the frictional and wave-making resistance are equal. if you'll notice
on the graph the minimal total resistance occurs when the frictional
resistance is about 1.5 lb and the wave-making resistance is 4.5 lb. There
is a local minimum but it's not the simple intuitive tradeoff you've
claimed.


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Kayaks should be designed around people instead of designing for
isolated boat performance. I don't know of any kayak designers who
do this. Instead of concentrating on hull resistance, designers
could concentrate on paddler horsepower requirement. A low cost,
mass marketed kayak should be designed to suit a range of
horsepowers, paddler weights, and paddler dimensions. A kayak
produced for a more limited market can be designed to suit a
smaller range of horespowers, paddler weights, and paddler
dimensions. An expensive one off kayak can be custom designed to
suit the power, weight, and dimensions of an individual paddler.
It would cost no more to custom design a plywood kayak built with
computer cut panels than to design a mass produced plywood kayak
built with computer cut panels. The design ranges should be listed
in the sales information for each model of kayak. Design
performance graphs could be included, and for some boats actual
test data plotted. Such an approach to designing would answer the
buyer's perrenial question "which kayak is right for me?". The
approach is particulary appropriate for kayaks because they are
are primarily transporters of people using the person's own power
resources for propulsion. The cost of the design is small compared
to the cost of materials, labour, distribution, marketing, and
sales. It would not cos much to do a more complete job of the design
and provide better information for the buyer.
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William R. Watt wrote:

Kayaks should be designed around people instead of designing for
isolated boat performance. I don't know of any kayak designers who
do this. Instead of concentrating on hull resistance, designers
could concentrate on paddler horsepower requirement. A low cost,
mass marketed kayak should be designed to suit a range of
horsepowers, paddler weights, and paddler dimensions. A kayak
produced for a more limited market can be designed to suit a
smaller range of horespowers, paddler weights, and paddler
dimensions.

That's exactly what the boats currently on the market do, it's just not
expressed in terms of horsepower, since the average paddler wouldn't
have a clue as to what that means.

An expensive one off kayak can be custom designed to
suit the power, weight, and dimensions of an individual paddler.

OK. One can build a custom boat and there are companies that will do so.

It would cost no more to custom design a plywood kayak built with
computer cut panels than to design a mass produced plywood kayak
built with computer cut panels.

How do you figure that? The most efficient hulls (least wetted surface
for a given displacement) are rounded in shape, which cannot be built
from flat panels. The cost to produce a mold for a one-off design is
prohibitive. One could have a boat custom designed and strip built, but
how many people are going to pay in excess of $5000 for a kayak?

The design ranges should be listed
in the sales information for each model of kayak. Design
performance graphs could be included, and for some boats actual
test data plotted.

To what end? This information is often available for racing boats -
where the paddler actually cares about such things - but do you honestly
think that the average recreational or touring paddler would have any
interest in this whatsoever? I'll bet most of them don't even read the
owner's manual, let alone a bunch of technical data that they don't
understand.

Such an approach to designing would answer the
buyer's perrenial question "which kayak is right for me?".

Not if they don't understand the information. Most won't and they're not
going to be willing to learn about hydrodynamics in order to do so.

The
approach is particulary appropriate for kayaks because they are
are primarily transporters of people using the person's own power
resources for propulsion. The cost of the design is small compared
to the cost of materials, labour, distribution, marketing, and
sales. It would not cos much to do a more complete job of the design
and provide better information for the buyer.

Perhaps so, but whatever money it did cost would be largely wasted,
since most paddlers are more interested in the color of their boat than
performance graphs. I think it's safe to say that the vast majority of
kayaks are purchased based on:

- Impulse. One sees a cheap rec boat at one of the Marts or wholesale
clubs and buys it

- Recommendations of a salesman. One goes to a sporting goods store or a
local kayak dealer and buys what they suggest.

- Recommendations of friends. One speaks with friends who are paddlers
and takes their advice.

- What's available in the area. Not all boats have dealers in every
area. Locally made products or those carried by local dealers will
predominate, regardless of whether they're the best boats for specific
paddlers. Few people will special order a boat and pay to have it
shipped to them. While there are a few niche manufacturers that cater to
this market, I'll wager that their combined annual output is less than
2000 boats out of a market of over 300,000.

While you and I and some others here may care about performance data,
it's pretty obvious that most kayak owners don't and never will.

Brian Nystrom ) writes:

It would cost no more to custom design a plywood kayak built with
computer cut panels than to design a mass produced plywood kayak
built with computer cut panels.

How do you figure that?

companies like Chesapeke(?) Light Craft and Pygmy Boats sell plywood boats
and kits make from computer cut panels. people buy the boats or they
can assemble the kits themselves and save a lot of money.

... The most efficient hulls (least wetted surface
for a given displacement) are rounded in shape, which cannot be built
from flat panels. The cost to produce a mold for a one-off design is
prohibitive. One could have a boat custom designed and strip built, but
how many people are going to pay in excess of $5000 for a kayak?

yes, avoiding moulds for building resin boats one off was my point.
you can custom design and build a plywood or a "stripper" boat cheaper.

as for the preformance of flat panel (hard chine) hulls its actually the
turbulence at the chines which creates more drag at higher speeds compared
to smooth chined hulls. the wetted surface vs wave-making again.

some places you read about wetted surface vs wave-making. other places
its wetted surface vs residual resistance, where residual resistance is
any kind of drag that's not surface friction and includes drag due to
wave-making, poor tracking, hard chines, etc.

Such an approach to designing would answer the
buyer's perrenial question "which kayak is right for me?".

Not if they don't understand the information. Most won't and they're not
going to be willing to learn about hydrodynamics in order to do so.

all part of the education of the paddling public.

I agree with everything you wrote below about the motivation to
buy a kayak but when it comes to the actual purchase people do ask about
which kayak is best for them, likely because they will be spending so much
money on the boat and accessories.

I think people can relate to how much power it should take a person of a
given weight to get the boat to go a certain speed than to how many pounds
of resitance the boat should have at a that speed, especially when you
tell them how much power an average person can sustain paddling. I also
think people could relate better to how tall they should be or how much
they should weigh for a given kayak than just to say "for light people" as
the brochures usually do. The data could be on a website rather than print
a more costly booklet to replace the brochure. All of thse numbers should
be avialable from desingers now, just restate and pass along to buyers.

While you and I and some others here may care about performance data,
it's pretty obvious that most kayak owners don't and never will.

I've actually seen a lot of queries about "what kayak is right for me" and
I suspect its because of the high cost of the boats which makes people stop
and think. Kayaks and canoes cost more than bikes, skis, and skateboards.
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Hi Brian
you forgot about the seat thing. After the sales talk ends, the final
purchase many times is determined (for the first time buyer) by the way the
seat fits. I see tons of boats bought and sold , not so much by the way they
handle, as by the way the seat fits. Seems like only a small amount of
people will plunk down their money, take the boat home, rip out an
uncomfortable seat and replace it with something that works for them (then
drill a hole for the bilge water exit fitting/ mount a foot pump or a C50 or
an electric of some sort such as a waterbuster)

best wishes
Roy


"Brian Nystrom" wrote in message
...
William R. Watt wrote:

Kayaks should be designed around people instead of designing for
isolated boat performance. I don't know of any kayak designers who
do this. Instead of concentrating on hull resistance, designers
could concentrate on paddler horsepower requirement. A low cost,
mass marketed kayak should be designed to suit a range of
horsepowers, paddler weights, and paddler dimensions. A kayak
produced for a more limited market can be designed to suit a
smaller range of horespowers, paddler weights, and paddler
dimensions.

That's exactly what the boats currently on the market do, it's just not
expressed in terms of horsepower, since the average paddler wouldn't
have a clue as to what that means.

An expensive one off kayak can be custom designed to
suit the power, weight, and dimensions of an individual paddler.

OK. One can build a custom boat and there are companies that will do so.

It would cost no more to custom design a plywood kayak built with
computer cut panels than to design a mass produced plywood kayak
built with computer cut panels.

How do you figure that? The most efficient hulls (least wetted surface
for a given displacement) are rounded in shape, which cannot be built
from flat panels. The cost to produce a mold for a one-off design is
prohibitive. One could have a boat custom designed and strip built, but
how many people are going to pay in excess of $5000 for a kayak?

The design ranges should be listed
in the sales information for each model of kayak. Design
performance graphs could be included, and for some boats actual
test data plotted.

To what end? This information is often available for racing boats -
where the paddler actually cares about such things - but do you honestly
think that the average recreational or touring paddler would have any
interest in this whatsoever? I'll bet most of them don't even read the
owner's manual, let alone a bunch of technical data that they don't
understand.

Such an approach to designing would answer the
buyer's perrenial question "which kayak is right for me?".

Not if they don't understand the information. Most won't and they're not
going to be willing to learn about hydrodynamics in order to do so.

The
approach is particulary appropriate for kayaks because they are
are primarily transporters of people using the person's own power
resources for propulsion. The cost of the design is small compared
to the cost of materials, labour, distribution, marketing, and
sales. It would not cos much to do a more complete job of the design
and provide better information for the buyer.

Perhaps so, but whatever money it did cost would be largely wasted,
since most paddlers are more interested in the color of their boat than
performance graphs. I think it's safe to say that the vast majority of
kayaks are purchased based on:

- Impulse. One sees a cheap rec boat at one of the Marts or wholesale
clubs and buys it

- Recommendations of a salesman. One goes to a sporting goods store or a
local kayak dealer and buys what they suggest.

- Recommendations of friends. One speaks with friends who are paddlers
and takes their advice.

- What's available in the area. Not all boats have dealers in every
area. Locally made products or those carried by local dealers will
predominate, regardless of whether they're the best boats for specific
paddlers. Few people will special order a boat and pay to have it
shipped to them. While there are a few niche manufacturers that cater to
this market, I'll wager that their combined annual output is less than
2000 boats out of a market of over 300,000.

While you and I and some others here may care about performance data,
it's pretty obvious that most kayak owners don't and never will.

(William R. Watt) wrote in
:

Brian Nystrom ) writes:

It would cost no more to custom design a plywood kayak built with
computer cut panels than to design a mass produced plywood kayak
built with computer cut panels.

How do you figure that?

companies like Chesapeke(?) Light Craft and Pygmy Boats sell plywood
boats and kits make from computer cut panels. people buy the boats or
they can assemble the kits themselves and save a lot of money.

Both CLC and Pygmy offer a line of designs that one can build either from
computer cut panels or from a set of plans and cut the panels according to
the plans. They don't offer custom designs. If for example, someone wanted
a CLC Northbay, but wanted it 21" wide instead of 20" and 17'6" long instead
of 18'6" long the only way they'd be able to do that is take the standard
set of plans, modify them, then cut the panels according to the modified
plans. CLC isn't going to provide a modified set of plans, nor would they
provide computer cut panels for a custom designed Northbay. We'll, they
might, but at a considerably higher price than what one would pay for a
standard CLC Northbay.

Even for the standard models, while the plans + materials or a kit costs
less than a similarly designed composite boat, when one adds in the cost of
tools necessary to build it, extras like varnish, and the cost of labor, I'm
not sure that in the end one will save "a lot of money".
]

... The most efficient hulls (least wetted surface
for a given displacement) are rounded in shape, which cannot be built
from flat panels. The cost to produce a mold for a one-off design is
prohibitive. One could have a boat custom designed and strip built,
but how many people are going to pay in excess of $5000 for a kayak?

yes, avoiding moulds for building resin boats one off was my point.
you can custom design and build a plywood or a "stripper" boat cheaper.

While many people can and do build plywood or stripper boats (I've built one
of each) most kayakers don't build their own boats. No matter what boat
anyone chooses to own there are trade-offs. Many don't have the space or
woodworking skills (or at least they think they don't) to build their own.
Many would rather pay the extra cost to have a boat built for them rather
than spend the time to do it themselves. In that case, they can buy a boat
built from a mold or have something custom built (to the tune of $5000+ for
a cedar stripper as Brian mentioned).

For many, the most efficient hull for flat out forward speed performance
might not be desirable. An efficient hull optomized for higher speeds is
going to have some trade offs in manoeveribility and stability. While there
are many kayakers for which a highly efficient hull optomized for paddling
at high speeds for long distances is very important, I would guess that most
kayakers want a boat does other things efficiently as well.

For example, one of the most popular production boats on the market is the
NDK Romany. There are certainly faster boats available, but the Romany is
"fast enough", is fairly manoeverable, handles rough water well, and is
constructed strong enough that it can handle a variety of paddling
environments.
Such an approach to designing would answer the buyer's perrenial
question "which kayak is right for me?".

Not if they don't understand the information. Most won't and they're
not going to be willing to learn about hydrodynamics in order to do
so.

all part of the education of the paddling public.

I would imagine that most of the paddling public isn't really interested in
hydrodynamics. It's a lot easier to go out, try a few boats, and buy the
one that fits their needs the best.

I think people can relate to how much power it should take a person of
a given weight to get the boat to go a certain speed than to how many
pounds of resitance the boat should have at a that speed, especially
when you tell them how much power an average person can sustain
paddling.

If paddlers were only concerned about paddling at a high speed for long
distances you might have a point, but paddling is much more than that.

I also think people could relate better to how tall they
should be or how much they should weigh for a given kayak than just to
say "for light people" as the brochures usually do.

While there are some that will buy a kayak based on the stats or brochure
(and the appearance of the boat), pretty much every paddler with experience
will recommend that one actually sit in a paddle a boat before buying it.
It doesn't take a brochure to tell me that a boat is too small if the
cockpit is so tight that it cuts off circulation to my legs.

I've actually seen a lot of queries about "what kayak is right for me"
and I suspect its because of the high cost of the boats which makes
people stop and think.

That question is typically asked by people that have very little experience
in kayaks, and is often accompanied with little addtional data that would
help answer the question. I've answered the question many times, and
usually recommended several models with the suggestion to try as many as
possible and decide for themselves what kayak is right for them.


Kayaks and canoes cost more than bikes, skis,
and skateboards.

I don't know what a skateboard costs but it's certainly possible to spend
more a bicycle or snow skis than on a kayak.