RE: [Paddlewise] Boat and People sizes

Craig asked:



A) Do other "big" paddlers also have an aversion to really getting their
kayaks on edge?



Most folks have an aversion to really getting their kayak on edge. This is
because once you have leaned the kayak beyond the point of maximum righting
moment any further leaning momentum will result in a nearly instant capsize as
the righting force will decrease quicker than you can stop your momentum
(unless, of course, a solid brace is in place). Kayaks vary on how far over
they can be tipped before this point is reached. This also varies by how much
weight the paddler has above the center of gravity that they are shifting
while leaning the kayak. Given the same hull, and if they want to avoid a
capsize, the heavier paddler (and the more weight they have higher
up--typically males) the less thay can lean that particular kayak without
being dependent entirely on their bracing ability, their strength/weight ratio
and their attention to where the kayak/paddler's capsize point is.





B) Have they chosen a kayak based on that?



Most likely they chose their kayak based more on the feelings of security
(more based on initial stability) since a bigger taller person has a higher
center of gravity and more weight that is shifting making a kayak that a
smaller paddler would feel very stable in, feel quite tippy for them.


C) Can a boat designed to "fit" a larger paddler be as quick and nimble as one
designed for a smaller paddler?


No, on average most bigger folks aren't as nimble as smaller folk. They have
more mass to accellerate. However, relative to other paddlers of their weight,
the kayak they choose will limit how nimble they can be.



D) All else being equal is it possible to simply scale a design up or down to
fit a larger or smaller paddler while retaining the characteristics that made
the boat "good" at its original size?



Yes, but you have to scale all the dimensions, not just make the kayak longer,
wider, or deeper (just one dimension) so the paddler can physically fit the
kayak. The Illusion came in many depths but most middle to larger paddlers
feel it is pretty tippy (see latest Sea Kayaker review). Making it deeper
might mean a bigger paddler could physically fit in it but it would need to be
wider to have the same feeling of stability and likely longer or fuller in the
ends to have it sit in the water the same (as a smaller kayak does for a
lighter paddler). Sterling recognizes this (and is a huge guy himself) and
that is why he is developing the Grand Illusion.


E) Can a big guy ever hope to get a boat with the same performance
characteristics as an "average" (smaller) paddler can get or does "mass" play
an important role here?


Wider and longer mean more wetted surface and more friction but typically the
bigger paddler is stronger and is therfore more likely to be able to deal with
the extra wetted surface and windage that his bigger kayak will have. The
smaller paddler gets blown around easier and needs to be careful to get a
smaller (in all dimensions kayak) so as to maximize the advantages of less
wetted surface and less windage and lever arm for the windage to act on. A big
paddler in too small a kayak also may have a rescueability problem in that
that kayak might not support his weight when swamped. The small paddler has a
problem with too wide a kayak because it takes too much effort to lean it on
edge and they must lean their body way out into a much more vulnerable
position to get the kayak to lean much. Because they have had to force the
kayak up on edge (and had to lift their body more against gravity to do it) it
is easier to go too far. The smaller paddler will have a problem with too long
a kayak because of windage and the lever arm the wind has and the extra wetted
surface will likely mean they won't be able to take advantage of the higher
potential hull speed anyway but at the same time will have had to work against
more friction all the time they paddle it. Both the longer and deeper kayak
will increase the windage the smaller paddler will have to arm wrestle against
(no advantage to a better strength to weight ratio a smaller paddler may have
here--like they would with gravity). The deeper kayak will likely fit the
smaller kayak so that they feel they are having to paddle out over the sides
of a bathtub because they have to hold their paddle so high. Because their
hands are lower to start with they will have to stroke further off center with
a wider kayak (as well as find it too much work to lean the wider kayak to
increase turning speed).



Craig also wrote:

"It seems to me that if you weigh somewhere around 150 to 170 pounds you have
a much better chance of getting excellent performance out of a kayak design
than if you weight 240 to 300 pounds (or 100 pounds). Is there any basis for
this?"

As a big paddler you will get way better performance out of your Nimbus Telkwa
HV than a lot smaller paddlers will. It is kayak dependant, not a general
rule. Of course, those in the middle of the bell-curve always have more
choices in the market than those at the extremes. Most manufacturers are going
to concentrate their energy (especially initially) towards the largest
markets. As there became more customers for sea kayaks, sea kayak designers
found they could also profitably make kayaks for market niches and so some do.
Our Sprite model was designed for smaller paddlers, but it wasn't as small as
some smaller paddlers actually needed. The Coaster was designed for playing in
ocean surf (and fitting us more like a WW kayak) but at least half of those
sold because they fit the niche for small paddlers (even though
unintentionally). The Elan was derived from the Express but it was made
narrower and more V-bottomed (as well as much lower and with the cockpit
lowered even more by recessing it into the deck) so it wouldn't be too stable
to easily lean with a gear load or sit too high in the water for smaller
paddlers (who wanted a longer, narrower, kayak than the Coaster). The windage
was also substantially reduced from the Express even though the lengths are
about the same, again to make it easier for a smaller, lighter, less strong
paddler to turn it into a higher wind when it was unladen (when these things
matter most). Cam and I can't even fit into the Elan comfortably because our
thighs are too deep and our feet are too big, but then it wasn't designed for
folks our size.



So my conclusion is, the world isn't picking on you Craig. Even if it
sometimes feels to you like it is.









Date: Sun, 27 Jun 2010 17:59:56 -0700
Subject: Fwd: Boat and People sizes
From: crjungers_at_gmail.com
To: marinerkayaks_at_msn.com

Since you may not get this - or any replies - in a timely manner I thought I'd
send this to you separately. :)

Craig
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