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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(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.

John Fereira ) writes:

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

I didn't claim either company sold custom plans or kits. I only wrote that
it's possible to do cheaply becuase all that has to be done is to change a
few numbers in the design program and the computer cuts out the new boat
panels or station mould patterns. Plywood and stripper kayaks could be
custom made just like you buy a custom tailored business suit, but at
minimal extra cost.

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".

you save approx 1/3 off the cost of a stripper boat by building yourself.
that's why so many people do it. that's why Ted Moores is so popular.

For many, the most efficient hull for flat out forward speed performance
might not be desirable.

please show me where I claimed speed vs horsepower was the sole reason for
choosing a kayak. I do think speed is the principle reason people choose
kayaks over other boats like canoes and punts and for that reason I think
buyers should be presented with the information on how fast their kayak is
designed to go with different levels of effort.

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.

the point of this discussion about hull resistance and horsepower
requirement is how much more effort a person has to exert to keep up with
a group of paddlers. I don't know about paddling at high speed, just the
speed the gropup is paddling at. If you don't want to be exhausted at the
end of a day of paddling in a group then the power you have to put out to
maintain the group speed is the most important factor.

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.

sadly, yes, that's how it is done now. but it doesn't have to be done that
way. last summer I was told by a couple of kayak fanatics in this very
newsgroup that it was wrong to choose a kayak based on how it felt and
that after one or two seasons such people are eager to buy the kayak they
should have bought in the first place. if sellers provided the design
range for paddler weight and dimensions potential buyers could quickly
narrow down the kayaks to the ones most suitable and they could choose
from among those kayaks. you may be aware of how igorant kayak sales staff
are. they are happy just to sell the kayak and cannot provide much in the
way of help to the buyer. buyers would be better off with relevant design
information.

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.

how many kayak buyers do you think are people with "very little experience
in kayks"? 80%? 90%? 95% people do generally know what they weigh and how
tall they are. people can take their own body measurements just like
people who buy skis and bicycles do. there are people who lurk in this
newsgroup who will say that telling people who have very littel expericne
to try kayaks for themselves in not good adivce. I tend to agree compared
to what they could do with more design information.

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.


if its possible it's out at the exteme end of the price range. compare
averages instead.

Here's an analogy. I chose my last two new automobiles by doing reasearch
at the public library and then went out and bought them. I've been driving
the most recent one for 15 years hope to keep driving it for years to
come. I understand that people buying automobiles today have even more
information available off the Interent than I had. However buying a new
automobile by going a dealership for a test drive is the worst possible
way of buyiung a new automobile that I can think of. Kayaks don't have the
volume and interest of automobiles but a better job can be done at no
extra cost providing relevant information for kayak buyers, information
which is paddler-oriented rather than boat oriented. Kayak sellers would
better serve their customers by concentrating more on the paddler and less
on the boat. that's why I suggest making power requriements, body weight,
and body size design information available to buyers. I'd certainly
provide horsepower rather than total hull resistance.


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William R. Watt wrote:

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.

Compared to what? When you factor in all the tools and other supplies,
plus the time involved, there is no savings at all. Building boats is a
labor of love, not an economic expedient.

More importantly, what percentage of kayakers build their own boats? For
that matter, what percentage is even capable of it or has a place to do
it? You seem to forget that we live in a country where most people can't
even change the oil in their cars, let alone build kayaks.

While it's certainly possible to custom design and cut panels for stitch
and glue boats, no one does so. The closest thing to it is Newfound
Woodworks will take a customer's design and make the panels for them,
but there are even fewer people who can design a boat than there are
than can build them.

... 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.

No kidding, but it's even more complex and time consuming to build one
than it is to do a S&G. BTW, I do build skin-on-frame boats, so I have
an idea what's involved.

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.

While turbulence is certainly a possibility with a poor design, it's not
a given. The wetted surface area is what makes the difference. Why do
you think that EVERY racing boat made has a rounded hull? Read the
manufacturer's literatue and read basic information on boat design and
they all say the same thing: round hulls have less surface area for a
given displacement than hard chine hulls. A spherical hull would have
the absolute least wetted area, but obviously, it would no longer be a
kayak or canoe.

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.

That's not the point, you can have two boats with the same wavemaking
resistance and one with a rounded hull will have less drag than one with
a hard chine hull, due strictly to the difference in wetted surface area.

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.

It's very obvious that you've never worked in retail. I have
extensively, including owning a retail business. Your perceptions about
the buying public couldn't be farther off the mark. Most people,
especially first time buyers of a product, are CLUELESS. Most simply
want someone to guide them to a suitable product quickly and not screw
them over. It really IS that simple! If you were to start talking about
horsepower and other technicalities, their eyes would quickly glaze over
and they'll find a reason to leave, after which they'll go buy elsewhere
from someone who doesn't bore or intimidate them. I know this because
I've worked in businesses where technical data was widely available and
we always took the approach of educating people as much as possible and
helping them make the right decision for themselves (consultative
selling). In doing so, you learn that there is a VERY fine line between
enough information and "information overload" and that it's different
for every customer. If someone comes in looking for "a yellow kayak",
they're not going to hang around while you explain advanced
hydrodynamics to them. You set them up the best you can, offer as much
information as they'll tolerate, take their money and let them be on
their way. I didn't like the way I was forced to do business in some
cases, but I figured that they were better off if they came to me and I
at least had the opportunity to offer them useful information, than if
they went and bought at one of the "Marts" from some bored high school
kid who couldn't care less.

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.

No, it's because most people have no clue what they need and they're
looking for someone to hold their hand through the buying process. It's
also because most are either too lazy or too disinterested to do any
research for themselves. Many simply aren't capable of understanding
technical data (or at least they're convinced that they're not). You may
not like it, but those are the hard facts of retail. People like you and
I and some others here are but a tiny minority of the buying public.
Only the niche market companies will bother to cater to us, because
that's what separates them from the mainstream.

Brian Nystrom ) writes:
William R. Watt wrote:

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.

Compared to what? When you factor in all the tools and other supplies,
plus the time involved, there is no savings at all. Building boats is a
labor of love, not an economic expedient.

I've already mentioned the 1/3 cost savig nin building "stripper" boats from
a kit. That includes all the materials and assumes you have a few basic
tools on hand. Buildign boats is not a labour of love, it is mostly a way
of being able to afford the cost of the boat. I don't know where you get
this "labour of love" business. The same place you got the 2% hull
scratches friction, somewhere in the deep dark obscure recesses of your
imagination?


More importantly, what percentage of kayakers build their own boats? For
that matter, what percentage is even capable of it or has a place to do
it? You seem to forget that we live in a country where most people can't
even change the oil in their cars, let alone build kayaks.

enough people build their own canoeos and kayaks to make the selling of
plans and kits profitable. belive it or not there are even people out there
building birch bark canoes and teaching the building of birch bark canoes,
and canoe camping in the birch bark canoes they built.
building a small boat is not rocket science. I've lost count of the number
of webistes full of photos of novices building their own canoes and kayaks
every one starting with a comment to the effect, "Before starting to build
my own canoe (or kayak) I'd never so much as changed a light bulb. I was a
complet kutz with two left thumbs." and so on ad infinitum. I've read
somewhere some Brian Nystrom guy built his own first boat at one time.


While it's certainly possible to custom design and cut panels for stitch
and glue boats, no one does so. The closest thing to it is Newfound
Woodworks will take a customer's design and make the panels for them,
but there are even fewer people who can design a boat than there are
than can build them.

that doesn't mean it can't be done. I wrote that it could be done. I did
nto write taht it was beign done. There are a lot of things in this world
that could be done, or could be done better, that aren't. that was my point.

No kidding, but it's even more complex and time consuming to build one
than it is to do a S&G. BTW, I do build skin-on-frame boats, so I have
an idea what's involved.

I don't see your point. The major savings in building one's own boat is in
labour. You build it yourself to save the cost or paying someone
esle to build ti for you. YOu also save other costs such as "shop" costs
by building it in your garage, attic, or living room.


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.

While turbulence is certainly a possibility with a poor design, it's not
a given. The wetted surface area is what makes the difference. Why do
you think that EVERY racing boat made has a rounded hull? Read the
manufacturer's literatue and read basic information on boat design and
they all say the same thing: round hulls have less surface area for a
given displacement than hard chine hulls. A spherical hull would have
the absolute least wetted area, but obviously, it would no longer be a
kayak or canoe.

I think you'd better take another look at what I wrote. Hard chined boats
do have a bit more wetted surface but the turbulence at the hard chine has
a bigger effect, moreso as speed increases. (Lapped strake boats have the
same increase in resistance.) Interestingly, and contrary to what yoru
write above, a spherical hull does nto have the minimum wetted surface.
That's because only part of the shpere is immersed, ie. a chord of the
circle. John Winters (www.greenvall.com/winters.html) has some diagrams to
illustrate this. I thought as you did until I saw his examples.


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.

That's not the point, you can have two boats with the same wavemaking
resistance and one with a rounded hull will have less drag than one with
a hard chine hull, due strictly to the difference in wetted surface area.

nope, the drag of the hard chine hull includes the turbulence about the
chine which is greater than the difference in friction resistance. but
don't forget you can have a V-bottom hard chined boat which tracks better
than a round bottom hull with the same length and wetted surface and the
hard chined hull will have less residual resistance because it spends less
time slewing around, and more time going straight. as we have all seen,
the boat with the rounded bottom cross section will often have "deadwood"
added at the bow and stern or a skeg (or rudder) or both to help it track,
and these add wetted surface to the rounded hull.

It's very obvious that you've never worked in retail. I have
extensively, including owning a retail business. Your perceptions about
the buying public couldn't be farther off the mark. Most people,
especially first time buyers of a product, are CLUELESS. Most simply
want someone to guide them to a suitable product quickly and not screw
them over. It really IS that simple! If you were to start talking about
horsepower and other technicalities, their eyes would quickly glaze over
and they'll find a reason to leave, after which they'll go buy elsewhere
from someone who doesn't bore or intimidate them. I know this because
I've worked in businesses where technical data was widely available and
we always took the approach of educating people as much as possible and
helping them make the right decision for themselves (consultative
selling). In doing so, you learn that there is a VERY fine line between
enough information and "information overload" and that it's different
for every customer. If someone comes in looking for "a yellow kayak",
they're not going to hang around while you explain advanced
hydrodynamics to them. You set them up the best you can, offer as much
information as they'll tolerate, take their money and let them be on
their way. I didn't like the way I was forced to do business in some
cases, but I figured that they were better off if they came to me and I
at least had the opportunity to offer them useful information, than if
they went and bought at one of the "Marts" from some bored high school
kid who couldn't care less.

I agree when a person walks in off the street do not want to be
"overloaded" with information that has no meaning to them, however they
can understand information realted to their strength, weight, and body
size. They might not know anything about boats but they certainly do know
a lot about themselves. That's my point. The information should be
provided in a way that relates to the buyer, not the boat. It makes nto
sense to graph boat speed vs total resistance when it can just as easily
be plotted against horsepower with reference lines drawn for average (1/20
hp), athletic (1/4 hp), and absolute maximum sprinting (1/5 hp) power
output of humans. People will consult and use meaningful, relevant
information.

My areas of expertise in my former life was not selling boat but in
numerical computer systems and statistics. One my areas of research and
application was the graphical analysis and display of numerical
information. So I just might possibly also know of that which I write.

No, it's because most people have no clue what they need and they're
looking for someone to hold their hand through the buying process. It's
also because most are either too lazy or too disinterested to do any
research for themselves. Many simply aren't capable of understanding
technical data (or at least they're convinced that they're not). You may
not like it, but those are the hard facts of retail. People like you and
I and some others here are but a tiny minority of the buying public.
Only the niche market companies will bother to cater to us, because
that's what separates them from the mainstream.


I have to disagree. Blaming the buyer for the seller's failure to provide
important information in a form the buyer can use is a cop out. Sellers
who blame customers for their own failings are at risk of having someone
take their customers away from them.



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On 5-Jun-2004, (William R. Watt) wrote:

I think you'd better take another look at what I wrote. Hard chined boats
do have a bit more wetted surface but the turbulence at the hard chine has
a bigger effect, moreso as speed increases. (Lapped strake boats have the
same increase in resistance.)

The difference between hard and rounded chine in practice is negligible - at
least for kayaks. You'd have a hard time finding two kayaks that have a
difference that you could attribute to the chines and could also feel the
difference.

Interestingly, and contrary to what yoru
write above, a spherical hull does nto have the minimum wetted surface.
That's because only part of the shpere is immersed, ie. a chord of the
circle. John Winters (www.greenval.com/winters.html) has some diagrams to
illustrate this. I thought as you did until I saw his examples.

You'll have to be more specific. I looked at all the pages and figures and
can't see anything that specifies the characteristics of a spherical hull.
He has circular cross sections, but not spherical hulls.

If the spherical hull does not have the least surface to volume ratio,
please tell us what shape does.

Mike

"Michael Daly" ) writes:

The difference between hard and rounded chine in practice is negligible - at
least for kayaks. You'd have a hard time finding two kayaks that have a
difference that you could attribute to the chines and could also feel the
difference.

TF Jones disagrees with you. So do I based on what you wrote earlier about
the effect of hull scratches and gouges.
You'll have to be more specific. I looked at all the pages and figures and
can't see anything that specifies the characteristics of a spherical hull.
He has circular cross sections, but not spherical hulls.

If the spherical hull does not have the least surface to volume ratio,
please tell us what shape does.

Could you explain the significance of "spherical" hulls, because only the arc
of the circle below the waterline gets wetted?

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William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
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On 6-Jun-2004, (William R. Watt) wrote:

The difference between hard and rounded chine in practice is negligible - at
least for kayaks. You'd have a hard time finding two kayaks that have a
difference that you could attribute to the chines and could also feel the
difference.

TF Jones disagrees with you.

Reference please. My information comes from John Winters himself.


So do I based on what you wrote earlier about
the effect of hull scratches and gouges.

??? When did I ever write that gouges and scratches have a significant
effect on drag?

If the spherical hull does not have the least surface to volume ratio,
please tell us what shape does.

Could you explain the significance of "spherical" hulls, because only the arc
of the circle below the waterline gets wetted?

They are a starting point in looking at the effects of hull shape on resistance.

Mike

William R. Watt wrote:
Brian Nystrom ) writes:

William R. Watt wrote:


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.

Compared to what? When you factor in all the tools and other supplies,
plus the time involved, there is no savings at all. Building boats is a
labor of love, not an economic expedient.


I've already mentioned the 1/3 cost savig nin building "stripper" boats from
a kit. That includes all the materials and assumes you have a few basic
tools on hand. Buildign boats is not a labour of love, it is mostly a way
of being able to afford the cost of the boat. I don't know where you get
this "labour of love" business. The same place you got the 2% hull
scratches friction, somewhere in the deep dark obscure recesses of your
imagination?

It's real simple Bill, so perhaps even you can understand it. The price
of a stripper kayak kit that includes seat parts, footpegs, deck rigging
and finishing supplies is $1200-$1400 (based on the prices from Newfound
Woodworks) plus shipping, which isn't cheap since they must be shipped
by truck. Unless one is already a woodworker, you can figure on adding
several hundred dollars for the cost of tools and the materials to build
a strongback, sawhorses, etc., to the cost of the kit an supplies. That
brings your your total hardware and supplies cost up to $1500~$2000.
When you factor in the 200-300 hours of labor involved in building a
stripper (typical numbers derived from what hobbyist builders report on
kayak building sites), even if you only value your time at $10/hour
(slave wages), you're looking at a real cost of $3500-$5000 for your
first boat. Subsequent boats will be somewhat cheaper since you now have
the tools and strongback, but that's assuming that you build more than one.

Considering that you can buy a new 'glass boat for ~$2500 or a used one
for as little ~$1000 (I've bought several at that price), where is your
savings, Bill? You accuse me of imaginative, yet it's quite obvious that
your "1/3 savings" figure is wishful thinking at best. I enjoy building
boats, but I'm under no illusion that it saves me any money. The main
reason for building a boat (other than the recreational aspects of
woodworking) is that I get exactly what I want.

More importantly, what percentage of kayakers build their own boats? For
that matter, what percentage is even capable of it or has a place to do
it? You seem to forget that we live in a country where most people can't
even change the oil in their cars, let alone build kayaks.

enough people build their own canoeos and kayaks to make the selling of
plans and kits profitable.

What does that prove? It doesn't cost much to design a boat and sell
plans. Both plans and kits are much more profitable than selling
commercial kayaks.

belive it or not there are even people out there
building birch bark canoes and teaching the building of birch bark canoes,
and canoe camping in the birch bark canoes they built.

Gee, Bill, REALLY???? Wow, that's INCREDIBLE!!!! I've never heard of
anyone actually BUILDING a boat or TEACHING people to build boats!!!!
You must be the smartest, most informed person ON THE ENTIRE PLANET!!!!

building a small boat is not rocket science.

You have a truly amazing grasp of the obvious.

I've lost count of the number
of webistes full of photos of novices building their own canoes and kayaks
every one starting with a comment to the effect, "Before starting to build
my own canoe (or kayak) I'd never so much as changed a light bulb. I was a
complet kutz with two left thumbs." and so on ad infinitum.

Yet boat builders are still a MINUSCULE percentage of the total number
of kayakers. You really need to get a grip on the reality of the market.
To put some perspective on it, I belong to a club with over 400 members
in it. Out of those, I know of 9 (2.25%) who have built boats. That's
among paddlers who are dedicated enough to join a club. We represent
only a small fraction of the total kayaking population, the majority of
whom paddle plastic recreational boats. Based on that, I think it's safe
to say kayak builders represent well under 1% of the kayaking
population. Is that specific enough for you???

I've read
somewhere some Brian Nystrom guy built his own first boat at one time.

You read wrong. I built my third boat. My first two were commercial boats.

While it's certainly possible to custom design and cut panels for stitch
and glue boats, no one does so. The closest thing to it is Newfound
Woodworks will take a customer's design and make the panels for them,
but there are even fewer people who can design a boat than there are
than can build them.

that doesn't mean it can't be done. I wrote that it could be done. I did
nto write taht it was beign done. There are a lot of things in this world
that could be done, or could be done better, that aren't. that was my point.

Whether it CAN be done or not is irrelevant if it's NOT being done. If
you think it's such a good idea and has profit potential, go ahead and
do it. The people who already possess the equipment and the expertise
aren't doing it, so I suspect that they don't believe that it's a
commercially viable proposition.

No kidding, but it's even more complex and time consuming to build one
than it is to do a S&G. BTW, I do build skin-on-frame boats, so I have
an idea what's involved.

I don't see your point. The major savings in building one's own boat is in
labour. You build it yourself to save the cost or paying someone
esle to build ti for you. YOu also save other costs such as "shop" costs
by building it in your garage, attic, or living room.

I've already addressed this fallacy above. Either it's a "labor of love"
and you don't count the labor cost, or you're not saving anything. You
can't have it both ways, Bill.

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.

While turbulence is certainly a possibility with a poor design, it's not
a given. The wetted surface area is what makes the difference. Why do
you think that EVERY racing boat made has a rounded hull? Read the
manufacturer's literatue and read basic information on boat design and
they all say the same thing: round hulls have less surface area for a
given displacement than hard chine hulls. A spherical hull would have
the absolute least wetted area, but obviously, it would no longer be a
kayak or canoe.

I think you'd better take another look at what I wrote. Hard chined boats
do have a bit more wetted surface but the turbulence at the hard chine has
a bigger effect, moreso as speed increases. (Lapped strake boats have the
same increase in resistance.)

Where does this come from? I don't see any reason why a chine has to
cause turbulence. Lapstrake boats are not comparable with single chine
kayaks, whose chines are typically fully immersed and which have
smoother entries and exits. You're comparing apples and oranges.

Interestingly, and contrary to what yoru
write above, a spherical hull does nto have the minimum wetted surface.
That's because only part of the shpere is immersed, ie. a chord of the
circle. John Winters (www.greenvall.com/winters.html) has some diagrams to
illustrate this. I thought as you did until I saw his examples.

That link doesn't work. The correct link is:

www.greenval.com/jwinters.html

I realize that only a chord of the sphere is in the water. If you look
at the diagram at

http://www.greenval.com/fig1_3.gif

....it shows exactly what I was talking about. For a given beam width,
the spherical hull has the least wetted surface. If you ignore the beam
width and look only at equal displacement, a spherical hull still has
the least wetted surface. Although shape E is not perfectly spherical,
it's pretty obvious that a spherical shape with slightly increased depth
would have as little or perhaps slightly less surface area. This
explains why racing boat hulls are narrow and round. It's too bad he
chose not to include such a sample in the diagram.

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.

That's not the point, you can have two boats with the same wavemaking
resistance and one with a rounded hull will have less drag than one with
a hard chine hull, due strictly to the difference in wetted surface area.

nope, the drag of the hard chine hull includes the turbulence about the
chine which is greater than the difference in friction resistance.

Again, where is the reference? I don't believe that a single hard chine
is going to cause turbulence in an of itself in a well designed kayak.

but
don't forget you can have a V-bottom hard chined boat which tracks better
than a round bottom hull with the same length and wetted surface and the
hard chined hull will have less residual resistance because it spends less
time slewing around, and more time going straight. as we have all seen,
the boat with the rounded bottom cross section will often have "deadwood"
added at the bow and stern or a skeg (or rudder) or both to help it track,
and these add wetted surface to the rounded hull.

You're drawing a lot of invalid conclusions here. A long, narrow,
rounded hull with straight keel line (typical racing hull configuration)
tracks VERY strongly. One reason why most of them have rudders is to
enable the paddler to turn the boat, not because it won't track. The
main reason for rudders is to get maximum efficiency from the powerplant
(the paddler). It's more efficient to have a small rudder to control the
direction of the boat than it is to use leans and sweep strokes, which
reduce the biomechanical efficiency of the stoke.

By "deadwood" are you referring to bow and stern overhangs? If so, they
do nothing to aid tracking, as they're not in the water most of the time.

It's very obvious that you've never worked in retail. I have
extensively, including owning a retail business. Your perceptions about
the buying public couldn't be farther off the mark. Most people,
especially first time buyers of a product, are CLUELESS. Most simply
want someone to guide them to a suitable product quickly and not screw
them over. It really IS that simple! If you were to start talking about
horsepower and other technicalities, their eyes would quickly glaze over
and they'll find a reason to leave, after which they'll go buy elsewhere
from someone who doesn't bore or intimidate them. I know this because
I've worked in businesses where technical data was widely available and
we always took the approach of educating people as much as possible and
helping them make the right decision for themselves (consultative
selling). In doing so, you learn that there is a VERY fine line between
enough information and "information overload" and that it's different
for every customer. If someone comes in looking for "a yellow kayak",
they're not going to hang around while you explain advanced
hydrodynamics to them. You set them up the best you can, offer as much
information as they'll tolerate, take their money and let them be on
their way. I didn't like the way I was forced to do business in some
cases, but I figured that they were better off if they came to me and I
at least had the opportunity to offer them useful information, than if
they went and bought at one of the "Marts" from some bored high school
kid who couldn't care less.


I agree when a person walks in off the street do not want to be
"overloaded" with information that has no meaning to them, however they
can understand information realted to their strength, weight, and body
size. They might not know anything about boats but they certainly do know
a lot about themselves. That's my point. The information should be
provided in a way that relates to the buyer, not the boat. It makes nto
sense to graph boat speed vs total resistance when it can just as easily
be plotted against horsepower with reference lines drawn for average (1/20
hp), athletic (1/4 hp), and absolute maximum sprinting (1/5 hp) power
output of humans. People will consult and use meaningful, relevant
information.

I'll guarantee you that if you stick a graph in the faces of customers,
the overwhelming majority of them will have no idea what they're looking
at, nor will they care. On the other hand, if a dealer simply told them
that a particular boat was well suited to someone their size, that same
percentage would accept that. The few that would understand the graph
might ask "why", in which case you can offer a more detailed explanation.

My areas of expertise in my former life was not selling boat but in
numerical computer systems and statistics. One my areas of research and
application was the graphical analysis and display of numerical
information. So I just might possibly also know of that which I write.

That confirms something I had suspected.

While I certainly wouldn't question your data analysis capability, it
has nothing to do with the way people react to information in real
world. What makes perfect sense to you would be nothing more than
"technical gibberish" to most people. I've dealt with people in the real
world (as a retailer and as a technical trainer) and I can tell you
unequivocally that's a FACT.

No, it's because most people have no clue what they need and they're
looking for someone to hold their hand through the buying process. It's
also because most are either too lazy or too disinterested to do any
research for themselves. Many simply aren't capable of understanding
technical data (or at least they're convinced that they're not). You may
not like it, but those are the hard facts of retail. People like you and
I and some others here are but a tiny minority of the buying public.
Only the niche market companies will bother to cater to us, because
that's what separates them from the mainstream.

I have to disagree. Blaming the buyer for the seller's failure to provide
important information in a form the buyer can use is a cop out. Sellers
who blame customers for their own failings are at risk of having someone
take their customers away from them.

Sorry Bill, but whether you like it or not, that's the way it works in
the real world. While I agree that that manufacturers should make
technical information available, doing so would be largely a wasted
effort as the overwhelming majority of customers would neither
understand it or care. Given that, I can't fault them for not wasting
their resources to distribute this information widely. Selling the boat
is the dealer's job; the manufacturer should provide them with the
information to do so, but they're not responsible for getting it to the
customer. If they want to put it on a web site where interested
customers can find it, fine, but including it in marketing literature
would be an unnecessary expense and waste of paper.