Choosing
a
sea kayak for your needs
a bit of explanation on sea
kayak design
Every week I get a lot of email from people who want this or that in a
kayak. It is often the case that they have picked up a lot of
bits and pieces of kayak design information and now know just enough to
be either hopeless confused, or fixated on one particular aspect of
design without fully understanding the tradeoffs involved. I
decided to put together this article to give a simple introduction on
how length, width, and depth interrelate. In the future, I hope
to add another article on shapes.
It is often the case that people overestimate
how fast they travel in a sea kayak, or how fast they need to travel.
I
start by saying this because how fast you need to go will influence
your
kayak choices more than any other factor. You need to
make sure your boat is long enough that it can travel at your target
speed and a little more without hitting "hull speed" (hull speed
is when your kayak catches up to it's own waves and can't go much
faster). However, it's easy to be overly concerned about
hull speed,
and as a result buy a kayak with a much longer waterline than you need.
There are a lot of downsides to a long waterline, generally the
more waterline a kayak has, the more WETTED SURFACE it has, and the
more
wetted surface a boat has the more drag it has. Long
kayaks look really cool, but they also drag around more wetted
surface and take more energy to push at normal cruising
speeds than a shorter kayak. Shorter kayaks are easier to push,
easier to manuver, lighter, more stable, less affected by wind, and
easier to fit in your garage. So, contrary to popular sentiment,
what you really want is the shortest kayak that will allow you to hit
your target speeds without hitting hull speed for that waterline.
Sixteen feet is a common waterline length for a touring sea kayak, this
will allow a strong paddler to cruise at 5 miles per hour, it also adds
a lot of volume for camping gear. However, I have found that most
people aren't doing multi-week trips at 5 miles per hour. A much
more common use of a sea kayak is day and weekend trips at 3-4
mph. For this sort of use a 13 foot waterline will be more
efficient and feel faster, and be more fun to paddle. If you want
to test
this a gps can be used in conjunction with a heart rate monitor to
calculate calorie for calorie efficiency. I am not an athlete,
but I am a strong paddler, I paddle 3 times a week and I have never
exceeded 4.5 mph under normal cruising conditions, even when paddling
with strong friends or trying to set personal speed/distance
records. My
average cruising speed is 4 mph. (3 mph upwind, 5 mph downwind.) My
average cruising speed with mixed groups is 3 mph.
What about width? Breadth is helpful to spread some volume out to
the edges of the boat so there is something holding you up when you
lose your balance. Width adds stability. Personally, I really
like a bit of stability for rough water and fishing and eating
lunch. But isn't a narrower kayak faster? Well, yes, but
not as much as you'd think. Skin friction (wetted surface) and
hull speed (waterline) have more to do with speed and efficiency.
Narrower widths really comes into play in
racing or fast touring. Racing and fast touring is hard
work because DRAG ISN'T LINEAR. Every mile per hour faster you go
takes TWICE THE ENERGY OF THE LAST, due to the increase of turbulence
in water moving across the hull. Essentially the faster you go,
the less you speed you gain for how hard you have to work for it. This
is
why I prefer to design boats for 4 mph instead of the usual 5.
To
me it doesn't make sense to me to paddle twice as hard to go 20%
faster, or to pay the penalties in windage, wetted surface, stability
and manuverability.
However, for those who need the
speed, in these conditions where you
have to expend huge volumes of energy to hold your speed, every little
thing helps, narrower is a little faster, and more importantly,
narrower allows you to get your paddle planted closer to the boat
giving you more push per stroke. Of course you sacrifice
stability, and it's worth it, AT THOSE SPEEDS, but at normal cruising
speeds, the gains you achieve from making a kayak a few inches narrower
are minimal and don't outweigh the losses in manuverability and
stablity. There is a way to get the best of both worlds, by
making the kayak with flared sides you can have a narrow waterline AND
a lot of stablilty when you need it. A shorter sea kayak with a
narrow waterline is a very quick boat indeed!
Depth and width combine to add stability. Shallow and wide just
lets water flood over the gunwale, which REALLY increases your wetted
surface, so if you are going to wide, it makes sense to go deeper
too. Depth also gives you room to pack gear, and it lets you
raise your knees. The knees up position is more comfortable,
easier on the back, and is better for delivering power to the
boat. Low back decks are popular right now for their ability to
allow super easy rolling, but an ultra-low back deck that is constantly
awash slows you down and messes with the kayaks' handling, it is also a
liability in rescues scenarios. Serious greenland rolling demands a
boat like this to accomplish the very hardest rolls, but for all of the
beginning, intermediate, and even some of the advanced rolls, an
ultra-low back deck is unneccessary and will only instill bad habits as
it allows you to flounder upright with terrible form. With good
technique you should have no problem rolling even the most unwieldly
barge of a kayak. There is nothing wrong with owning a super low
volume sport rolling boat, they can be very fun but will not make good
cruising kayaks. It is interesting to note that very few actual
hunting kayaks had ultra-low
back decks.
What about the rest of design? I'm not saying that width, depth,
and length are the only things to look at, but these are what many
people fixate on and by looking at them first you identify a starting
point to give you an idea of what sort of boat you might be looking for
and then you can try different boats in that range to see which one
works best for you. Every choice is a tradeoff, but the more you
know about kayaks, the more informed you'll be to actually be able to
make those choices instead of letting marketing or fashion make them
for you. Personally, I paddle my F1, it's 14 feet long and 23
inches wide and allows me to paddle VERY easily at 4 mph. I
like the feel of my LPB (16 feet long and 22 inches wide) more on
flat water. The ergonomics are a little cleaner and the sprint
speed is pleasant, but over long distances, the increase in wetted
surface
means that I am NOT any faster. In rough water I much prefer
the F1 because it is utterly unaffected by wind, super easy to
manuever, loves to surf, and
is rock solid stable. The kayak is more than just a set of
numbers and drag
coefficients, it's a work platform, and I can tell you from experience
that 'faster' longer boats really slow down when they are fighting the
wind or are capsized. I'm not saying the F1 or any other
short boat is the right choice for everyone, but it's right for
me. If I were a strong fitness paddler on calmer waters most of
the time I'd probably chose a 16 foot boat. If you can get in a
boat 3-4 times a week and really push, you'll get the body you need to
make a 16+ foot waterline really sing, otherwise think about going
shorter. An exception to this is for people who will be doing a
LOT of sea kayak camping where the extra length is helpful to add room
for gear. Still, for week long trips or less, I simply carry a
lighter kit. My freinds are all in 55lb boats with 75 lbs of
camping gear, I'm in a 28 lb boat with 35 lbs of camping gear and due
to my shorter waterline and lightweight, I have...(to hammer the point
home here).., MUCH LOWER WETTED SURFACE, which is why I can keep up
just fine despite my shoulder injuries.
What about hunting kayaks? Inuit kayaks are fascinating and what
I've written applies to them as well, what is different is how much it
mattered to the inuits. As recreational paddlers we tend to focus
on
how easy a boat is to paddle, how stable it is, and how it handles in
the wind. We pay much less attention to things like little
splashing noises that would cause a kayak hunter to starve. Many
people are surprised to find hunting kayaks somewhat challenging to
paddle, and they look at these boats as though they might benefit from
'improvement'. It will greatly increase your appreciation of a
traditional kayak to accept it for what it is, a hunting tool, designed
above all to bring as much meat home as easily and safely as
possible. When you slide into a hunting kayak you go on a
cultural journey, and you'll enjoy that journey more if you let the
kayak be what it was designed to be.
Racing kayaks? I'll touch on this briefly by saying that you give
up almost every other favorable aspect of kayaking: stability,
seaworthieness, cargo room, efficient touring speeds, in pursuit
of the ultimate top speed. Racing kayaks are sexy and alluring,
but they are also easy to find used for a reason, people buy them and
realize that they are unpleasant to paddle. For serious trained
athletes, the drawbacks of a very narrow boat and a long waterline are
a necessity, for everyone else, I say leave them alone.
Another consideration is that once you surpass a certain length to
width ratio, you kayak is considered an unlimited class racer, and when
you race you will be competing against VERY strong athletes. If
instead you choose a kayak that is on the edge of this classification,
you can enter in the sea kayak class where you might have more fun and
a much better chance of placing well, and you'll have a kayak that is
actually useful for doing other stuff.
I hope this helps you choose the best kayak for your needs, whether you
buy a boat or build one it's important to remember that just because a
boat is fashionable or common doesn't mean it's the right boat for
you. Kayak designers make kayaks that will sell, and kayaks that
sell influence the kayaks that people use and buy. It has become
common place that a sea kayak needs to be 17 feet or longer to be taken
seriously, some designers are finding sneaky ways around this.
I've noticed a few of the hottest new designs have much shorter
waterlines, with long ends that stay out of the water most of the
time. When I asked one designer about the purpose of these
ends he confided (paraphrased) 'We have to sell kayaks.'
Kayaks I currently own:
Sea Kayaks: 2 of my F1's
Racing kayak: My Tyak
Hunting kayaks: My Disko Bay IV-A-375
Whitewater: 2 Necky Jives, Dagger
CFS, Liquid Logic Jefe, Jackson Rocker
Squirt/Surf: Mega Venon, New Wave Vulcan
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