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From: PeterO <rebyl_kayak_at_iprimus.com.au>
subject: [Paddlewise] FW: Why does rocker and carving work?
Date: Mon, 3 Dec 2001 16:05:16 +1100
Scott wrote

>Also, when a kayak is leaned with the right knee, does
>the boat turn because the water on the right side has
>a longer path

G'day Scott,

Just to continue. From your description I could see how the boat might drift
to the side due to a "lift" effect similar to an airfoil. However I'm not
sure that edging a boat should automatically turn it unless there is also
some element of sweep from the paddle. During training exercises we were
required to keep a kayak tracking in a straight line while holding it on its
edge. The trick being to paddling evenly despite the knee lift. Was never
quite sure of the point of the exercise and whenever I use knee lift my
stroke seems to automatically bias to one side to assist a turn.

Regards, PeterO

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From: Kevin Whilden <kevin_at_yourplanetearth.org>
subject: Re: [Paddlewise] FW: Why does rocker and carving work?
Date: Mon, 3 Dec 2001 19:01:09 -0800
----- Original Message -----
From: "Alder Creek Kayak & Canoe" <aldercreek_at_qwest.net>
To: <rebyl_kayak_at_iprimus.com.au>; "Paddlewise (E-mail)"
<paddlewise_at_paddlewise.net>
Sent: Monday, December 03, 2001 2:52 PM
Subject: Re: [Paddlewise] FW: Why does rocker and carving work?


>
> Where's Mr. Broze?
>

I agree... I hope Matt will lend his authoritative voice, even if he has to
make it up on the spot... ;)

>
> According to Matt, Mariner kayaks turn by being edged alone.  No
initiation
> required. Something about the asymmetric shape of the hull.  Tilt right
and
> the hull turns left and visa versa.  Most boats I have paddled are more or
> less neutral when edged and need some sort of persuasion or initiation to
> turn.

My Pygmy Arctic Tern will initiate its own carve, provided that I lean
forward. I have found carving turns to be quite sensitive to forward/back
leans.  Sitting in the nuetral position, it needs "help" to initiate the
turn.  Still, the Tern responds very quick once the turn is initiated and
carves beautifully.



> Once initiated the hull will build up spin momentum as the water
> pressure balance changes.  Tilt the hull either to the outside or the
inside
> of the turn and it will carve and turn faster. We call it YAWHOO, but
that's
> another story altogether.
>

So what is YAWHOO?? I have seen this mentioned on your website, but with no
explanation.  Some kind of mnemonic for kayaking skills, perhaps?

> I would think that a neutral hull would be better, so when doing a peel
out
> into current, a downstream tilt would allow the hull to freely turn
> downstream, instead of trying to turn the hull up against the current.
>

I just don't understand what you mean here.  How can the subtle hull design
differences that account for the characteristics of a leaned turn have
anything to do with eddy turns? If sea kayaking in a place with current, and
you happen to cross an eddyline, the only kind of hull that will "freely"
turn upstream is one that is not contacting the opposing current. In other
words, the hull needs to be completely out of the water. Get ready for a
peel-out as soon as the bow touches the oncoming current, unless your angle
w.r.t. the eddyline is exceedingly small (at least for sea kayaks... short
flat rodeo boats are more forgiving). The drag of the current against the
hull will completely dominate over the edged-turn characteristics in calm
water.

Cheers,
kevin


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From: Steve Scherrer <Flatpick_at_teleport.com>
subject: Re: [Paddlewise] FW: Why does rocker and carving work?
Date: Tue, 4 Dec 2001 07:56:48 -0800
Kevin writes:
>>So what is YAWHOO?? I have seen this mentioned on your website, but with
no
explanation.  Some kind of mnemonic for kayaking skills, perhaps?>>

Something that has to do with YAW, what we are discussing.
yes, a mnemonic that may go public soon.  ;-)

> I would think that a neutral hull would be better, so when doing a peel
out
> into current, a downstream tilt would allow the hull to freely turn
> downstream, instead of trying to turn the hull up against the current.
>

>>I just don't understand what you mean here.  How can the subtle hull
design
differences that account for the characteristics of a leaned turn have
anything to do with eddy turns? <<snip>>The drag of the current against the
hull will completely dominate over the edged-turn characteristics in calm
water.>>

I'm being pretty picky here but......if a boat has any tendency to turn when
leaned isn't there going to be resistance, while obviously not enough to
turn the boat against a current flow, but enough to *not* allow the boat
free release to the downstream side.  I don't really want my boat to resist
an inside edge turn by trying to turn the hull the opposite direction.  I'd
rather it was neutral so *I* could make the call, inside or outside edge,
starboard or port turn.

steve



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From: Kevin Whilden <kevin_at_yourplanetearth.org>
subject: Re: [Paddlewise] FW: Why does rocker and carving work?
Date: Tue, 4 Dec 2001 11:37:13 -0800
----- Original Message -----
From: "Steve Scherrer" <Flatpick_at_teleport.com>
<< snip >>
> I'm being pretty picky here but......if a boat has any tendency to turn
when
> leaned isn't there going to be resistance, while obviously not enough to
> turn the boat against a current flow, but enough to *not* allow the boat
> free release to the downstream side.  I don't really want my boat to
resist
> an inside edge turn by trying to turn the hull the opposite direction.
I'd
> rather it was neutral so *I* could make the call, inside or outside edge,
> starboard or port turn.

Okay, thanks for clarifying.  I think I understand your statement now.  You
are saying that when edging is constrained to one side only, as when
crossing an eddyline, that you still want the option of being able to turn
the kayak in the same direction as the side that was edged.  Is this
correct?

My answer is that in this case, the question is moot, because the current on
the far side of the eddyline will inherently dominate over the tendency of
the boat to turn away from an edge.  This is the because the edged-turning
momentum is created by the bow moving forward through the water and
displacing water preferentially to one side.  However when entering current
at an angle, the bow is no longer moving forward through the water, and the
water pressure will be on the opposite side of the one that causes a carved
turn. And thus the turning moment will point downstream, regardless of the
YAW... ;) Even very weak currents will dominate, as long as we are talking
about sea kayaks.  Not even a rudder hard over would any difference here
(i'm guessing). But I haven't tested it... Are your comments spoken from
experience? Which kayak were you paddling?

And by the way... does the HOO stand for what you might say if you forget to
yaw when crossing an eddyline... "Hoo boy, this water is COLD" (after you've
flipped over).

I will probably swing by AC's winter party tonight. Will you be there?

Kevin

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