[Paddlewise] Turns Easier When Loaded (was:RE: Baja Trip report and photos)

From: Matt Broze <mkayaks_at_oz.net>
Date: Wed, 16 Jan 2002 01:00:53 -0800
Mary wrote:
>>>>>>Well my CD GTS boat likes to track... I mean really likes to track
straight.
Turning it can be a challenge.  When it is empty I have to lean hard and do
sweep stroke to turn it.  I noticed that when I had it heavily loaded it
seemed to turn easier. It did not take a strenous knee lift.  I have a
couple of theories about it, but perhaps someone will have a better
explanation.  Theory 1 is that the boat is lower in the water so doesn't
take much of a lean to get on the edge.  Theory 2 is due to the extra weight
it was easier to get on edge.  I like my GTS but it is not an easy turning
boat.  Most of my kayaking is straight line point A to B so the strong
tracking is great.<<<<<<<<<<<<<

Theory 1 seems unlikely unless you and the gear and kayak are heavy enough
that the kayak is sunk to its widest point and the kayak is also relatively
narrow and rounded on the hull and deck (above the widest point) or the gear
is free to shift position (like free water does). Once a kayak like this is
sunk to its widest point additional lean shouldn't increase the stability
much especially if the center of gravity of the paddler/gear/boat is near
the midline of the hulls "cylinder" (sort of like a half sunk "rolling"
log). Most kayaks get more stable and much harder to lean when loaded with
gear mostly because of their lowered center of gravity. I suspect the GTS
does too unless maybe it is extremely heavily loaded.

Theory 2:  I ask you, does your GTS get easier to put on edge when loaded? I
strongly doubt it.
I also bet that you will find that it is actually slower to turn a kayak
when heavily loaded than when empty if you actually time how long it takes
to do a 180 degree turn at cruising speed both ways (even more so if timing
spinning the kayak in place). If you try this please let us know the
results.

Theory 3: (The one I'm about to propose)
The GTS is a very stiff tracking kayak that doesn't easily maintain a turn
even once the turn has been started (which was my experience--it took me 22
seconds to do a 180 degree leaned turn--and 43 seconds when I held the kayak
level--using only broad forward sweep strokes on the right side--Note: the
average of the over 300 hundred North American kayaks--admittedly including
some real short recreational ones--that I've done this with is: 11.4 seconds
leaned and 20 seconds when level. The GTS is nearly 3 standard deviations
(99.7%) above the mean of North American kayaks I've tested (but the very
stiffest in each measure were 38 and 55 seconds). Even when leaned, the GTS
tends to still track straight unless effort is expended to keep turning it.
In other words, when empty the GTS doesn't easily transfer its forward
momentum into turning momentum and what turning momentum you generate with
the paddle is readily dampened out by the tracking stiffness of the keel
(unless you maintain the turning force).
This behavior changes with a heavy gear load added because now there is a
lot of mass out near the ends of the (gear laden) kayak. Once that mass is
set into a rotational motion the tracking stiffness (even though it has also
increased some as the keels have been sunk deeper into the water) is no
longer enough to quickly kill the vastly increased rotational momentum that
now can keep the kayak turning in the direction in which the turn was
started. So with a heavy gear load the GTS now acts more like a more
maneuverable kayak does when it is empty.

For the same reasons, the very maneuverable kayak will often be more likely
to tend to wander when fully loaded, even though its tracking stiffness
might be just fine when it is empty. There are other factors involved as
well so this loaded/unloaded difference can be counteracted to some extent
by hull design as well as with a well chosen compromise between tracking
stiffness and ease of turning that minimizes the penalty to be paid with
each extreme. One downside to very stiff tracking can be turning that kayak
during a strong wind when it is empty and the ends can be blown back at a
wave crest as much as you could turn them in the trough. Faced with having
to paddle in a very strong wind without a gear load I'd ballast such a kayak
with genuine "Canadian Ballast Rocks" (or even a poor substitute like "U.S
Waterlogged Ballast Wood" if I wasn't paddling in Canada) out near the ends
of the kayak in order to increase the kayaks slug-feet-squared (although
this is normally discouraged among the cognoscenti). Maybe slugs are
embarrassed by their square feet and so always keep them out of sight. I've
seen a lot of slugs (living in the NW) and have never seen their feet, have
you?

Matt Broze
http://www.marinerkayaks.com


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Received on Wed Jan 16 2002 - 00:56:49 PST

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