Re:[Paddlewise] drag vs. viscosity [was :Deck Storage (Humor)]

Doug wrote:
>>>>>>>>Besides, kayak's are sluggish in fresh water<<<<<
I wrote:
>>>>If this is not tongue in cheek please explain the reason you say
this.<<<<<

I asked for an explanation from Doug as this does not fit with my
understanding and I wanted to know why it was he felt that kayaks were more
sluggish in fresh water. Was it a feeling he got paddling in fresh water.
Did he make head to head comparisons? Did he have a scientific explanation
(or did this come from some "authority" he believed)? Several Paddlewisers
provided reasonable sounding arguments as to why Doug's statement should be
so (and Dave suggested the wetted surface difference due to the different
densities would be so small one wouldn't be able to tell the difference). I
think I could detect that difference, if only barely after many tests.

Several years ago I undertook to study just what the differences might be
due to different environmental factors because I was timing turns and
sometimes top speed for numerous kayaks (over many years and at different
locations in both fresh and salt water).  I wanted to understand what
different conditions might effect the accuracy of my times. Fresh water
weighs about 62.5 pounds per cubic foot and typical open ocean salt water
weighs about 64 pounds per cubic foot. About a 2.5% difference. Towing tank
operators mostly use fresh water in their towing tanks and correct their
results for salt water. If I remember correctly the drag difference due to
the density difference is so small it is hardly worth worrying about. Yes,
there is more wetted surface and friction due to the less dense fresh water
so that results in a little more friction. However, if I'm remembering
correctly that is mostly offset by the boat having to push through the
denser salt water (being heavier its harder to push aside than fresh water).
The combination results in only a very small difference. One that, would be
insignificant compared to the potential errors of my timing in 1/2 second
intervals (at best).

Peter is right that viscosity is potentially a much more significant factor
than density. I discovered it is viscosity changes that I must worry about
affecting my results (and mainly when I'm testing in fresh water). The
reason for this is that colder water is stickier (more viscous) at the rate
of roughly 2.5% more drag for every 10 degrees F. of water temperature
reduction. In other words a 10 degrees F. difference translates to 2.5% in
frictional drag. Tank testers correct the results they get (mathematically)
so that although the tank water temperature may vary the results they report
will be the same as they would have gotten if the tank water had been 59
degrees F.  It is my understanding that the original "Taylor Standard
series" did not take water temperature changes during the tests into account
and that much later Gertler made the necessary corrections in his
"Reanalysis of the Original Taylor Standard Series". I use graphs from that
reanalysis to calculate the kayak test drag results for Sea Kayaker
magazine.

Since lake water around here (at the surface) varies from around as cold as
40 degrees in some winters to often over 70 degrees in the summer we are
talking about a potentially large error due to the viscosity changes
depending on the time of year I do any test. I have not officially (as part
of the spreadsheets I keep and analyze the data with) corrected my raw data
yet but I do keep track of the date and location where I did each test so I
could check out the water temperature (or make a good guess based on
historical averages for a given body of water) to make a correction factor
that will take this viscosity factor into account automatically. Since salt
water around here tends to stay within a 10 degree range year round (with
the exception of places where there are large areas of shallows) testing in
salt water isn't likely to generate such large differences over the course
of a year. The vast majority of my salt water tests are also done in
September at the Port Townsend Symposium so that should improve
consistency..

Writing about the symposium and testing kayaks there reminds me:
Kirby stated, concerning his not having tried a Mariner: "For some reason
the company doesn't participate in paddling events so people can try them
out. Too bad, their loss."

There are several reasons for this that outweigh our desire to have people
try out our kayaks head to head with the most of the competition at a
symposium (like we did for quite awhile beginning with the first sea kayak
symposium in Maine in 1982). One reason is because of the test paddling I do
on other companies kayaks (750+ tested so far). It is hard to do much kayak
testing at the greatest chance to do so (a symposium)  if you are one half
of your companies work force and you are already seriously overworked
hauling around and demoing your own kayaks to potential customers. Since we
quite bringing kayaks to symposiums I've been able to sometimes test paddle
as many as 56 new kayak models in one weekend. I find that much more
interesting work than adjusting foot pedals and cleaning sand out of kayaks
all day.

Another reason we quit going to the symposium (around ten years ago now I
think) was the politics (at that time) of the Trade Association of Sea
Kayaking and the West Coast Sea Kayaking Symposium they ran (both of which I
helped found in the early 1980's). When the overriding goal of the trade
association was to increase member company profits by trying to expand the
population of sea kayakers as much as possible (while we felt that paddling
areas were already getting too crowded--among other policy disagreements) we
did not want to be trade association members any longer as we did not
support the same goals as the big companies that provided most of the
officers. At first after no longer being a listed member we had to pay all
the dues anyway to be able go to just one symposium a year (where big
companies went to many). Later we were pressured (by the withholding of the
benefits unless we submitted to the indignity of being listed in the trade
association roster as being a member (and therefore appearing to support
their goals of bigger and bigger expansion of the market). Next we were
singled out for punishment for not joining by being assigned very poor
locations way down the beach where few folks ever got to and increasing the
hard work of hauling many kayaks to the beach that was many times further in
distance across loose sand than at the choicer locations. This was done even
though we had signed up among the earliest companies to do so (which had
been the criterion for requesting a location up to then) and we had paid the
same prices everybody else did for a beach location.

It is also hard for a very small company (which we always intended to
remain) to operate a store in one place and have your entire work force of
two people at a symposium (even if it is less than 100 miles away by car and
ferry).
Furthermore, we didn't need the symposium nearly as much as most kayak
companies. We can demo our kayaks on the water (just outside our window)
just about any day we are open. Anybody going through Seattle (as most
symposium attendees at Port Townsend could easily do and many probably did
in just getting to Port Townsend) could stop by and try them at their
convenience.

Symposiums used to be a bargain hunters paradise (now selling is not allowed
on the beach). Until a few years ago most all kayaks were discounted at
least 10% at the start of the symposium. Many companies, desperate to sell
the kayaks they had brought that were now scratched up, used, and needing a
good cleaning, discounted them far more on Sunday afternoon. This was easy
for most manufacturers to do because they were selling direct at the
symposiums then (rather than wholesale to a dealer) and therefore had the
usual dealer mark-up to play with. We mostly have operated more like a
retailer selling direct rather than to a dealer as most manufacturers do.
Because most Mariner kayaks were custom made for the customer ordering it we
usually had only our old demo kayaks at the symposium with none to sell
right there anyway (after 1990 we sold Seda Kayaks at a discount and even
did that for a year or two as Seda's representative after we pulled out as
Mariner Kayaks). We also have a policy to not ever discount Mariner kayaks
because of our limited production capability we could not handle building
many kayaks at once. Selling a bunch of kayaks at a discount would make for
a boom and bust economy with sales mostly being made at the discounted
prices during sales. Many paddlers would simply wait for the next predicable
sale or symposium discount program to actually make their purchase even
though it might take months for us to catch up with those orders (just about
in time for the next sale).

Even though it was relatively expensive for us to be at a symposium and we
rarely sold a Mariner kayak on the spot there (because we didn't have any to
sell that way) we would get orders over the next year or two from folks who
had paddled the kayaks at the symposium and remembered they had liked that
particular Mariner kayak the best back then. So while probably profitable to
be there it was not worth the extra work that would now take me away from
testing new kayaks at the symposium (while Cam is free to mind the store and
demo and sell our kayaks in Seattle at the same time). For those looking to
decide on which sea kayak to buy I don't see going to a symposium having
many benefits for us over our present set-pup and location. Many competitors
kayaks can be tested head to head with ours at our store which is only a few
doors away from our competitor Northwest Outdoor Center. NWOC carries
several other lines of kayaks from the ones we sell. REI's flagship store is
only a few miles away. Local more expert kayakers can even pick especially
windy days to make comparisons where at a symposium the weather is unlikely
to cooperate with the serious tester who wants to know how the kayaks
compare when it really counts.
In balance, I think the loss is more Kirby's than ours.

However, I'm still curious about why Doug wrote that kayaks are sluggish in
fresh water. If you are reading this Doug, please let us know.

Matt Broze
www.marinerkayaks.com
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