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From: PeterO <rebyl_kayak_at_iprimus.com.au>
subject: [Paddlewise] Bad forward sweep
Date: Wed, 9 Jan 2002 07:11:34 +1100
G'Day,

Thanks very much indeed to everyone for their advice and their summaries.

I've been thinking about how what has been said applies to the weaknesses in
my technique. So will summarise my situation and then ask some more
questions.

- My boat tracks very straight even when edged if
  I am not using some kind of turning stroke
- The most I can edge this boat, which is usually
  carrying some load in the rear hatch, is to get
  the coaming to the level of the water line. I
  can't edge the boat to get the coaming below the
  water line without leaning as well. If I increase
  the thickness of knee pads my feet go to sleep
  although I'm still modifying along the lines
  suggested in earlier posts.
- If the boat is leaned it will almost turn on a dime
  (20c in Australia:~)
- I've got no problem with straight arm paddling or
  body rotation or locking the shoulders to the body
  as I use an "Olympic" stroke unless in rough water
  and have practised this lots. Despite this I do
  extend the paddle for rotation strokes.

>From what is being said on Paddlewise I think my real problem is not leaning
enough with a good enough support component in the stroke so information on
blade angle and body lean and their variation as the paddle passes through
the water would be particularly welcome

I'ld be very interested in what degrees of turn with a forward sweep are
achievable if anyone happens to have assessed this

Also I'm confused as to whether the first or last part of the stroke has
most turning effect.

>From what Marinell says it sounds like lean turns in rough water are
probably not reasonable and using the waves is a better option.

Thanks again for all the advice it is very much appreciated

All the best, PeterO

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From: Jed <jluby_at_teamnorthatlantic.com>
subject: RE: [Paddlewise] Bad forward sweep
Date: Tue, 8 Jan 2002 16:44:18 -0500
Hi Peter,

- My boat tracks very straight even when edged if
  I am not using some kind of turning stroke

	It is not uncommon for a boat to require a sweep stroke to initiate a turn
before edging will have any effect. SO it's OK and normal to need to perform
a sweep stroke to get your boat to turn.

- The most I can edge this boat, which is usually
  carrying some load in the rear hatch, is to get
  the coaming to the level of the water line. I
  can't edge the boat to get the coaming below the
  water line without leaning as well. If I increase
  the thickness of knee pads my feet go to sleep
  although I'm still modifying along the lines
  suggested in earlier posts.

	To a lesser or greater extent all edging is leaning. We edge our boats by
moving our center of gravity to one side or the other. The boat reacts by
listing, lowering the edge beneath the center of gravity. Move your torso to
the left the boat edges on the left. People describe this as lifting the
opposite knee, but that happens after you move your CG (Center of
Gravity)and is really a way to keep from falling over.

	The boat does not know or care if your torso is vertical or leaning at an
angle. It only cares about where your CG is relative to the boats center of
bouyancy and the degree of heel (edging).

- If the boat is leaned it will almost turn on a dime

	If you need to lean to get your boat edged enough to turn quickly, then
have at it. Lot's of shorter paddlers do the same thing as do paddlers in
relatively wide boats.

-From what is being said on Paddlewise I think my real problem is not
leaning
enough with a good enough support component in the stroke so information on
blade angle and body lean and their variation as the paddle passes through
the water would be particularly welcome.

	I heard things a bit differently. Steve Scherrer taked about moving the
stern rather than the bow. I'll let him go into it in greater detail but I
agree completely with his explaination. I will say just this, to turn the
boat while moving forward one must move the stern, not the bow. To try and
move the bow is a waste of time.

	I would consider two things; firstly seakayaks are designed to run straight
when on an even keel. So to turn you need to edge the boat. A little edging
is good, more edging is better. This will lift the fine ends out of the
water, shortening the waterline and present a much more manouverable (sp)
hull form to the water.

	What ever support is gained from your paddle is done at the expense of
turning or propulsion. If you use your paddle for support during a sweep
then you are not getting the most turning force out of that sweep. Many
paddlers set their paddle for some support during a sweep but it's most
effective to keep the paddle vertical to the path and apply support only as
needed by rotating the paddle blade.

-I'ld be very interested in what degrees of turn with a forward sweep are
achievable if anyone happens to have assessed this.

	After I initiate my turn with a sweep stroke on the opposite side, I can
ride the carved turn for 90 degrees or so. This works going forward or in
reverse.

Good Luck,
Jed


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From: John Blackburn <digipixs_at_erols.com>
subject: Re: [Paddlewise] Bad forward sweep
Date: Tue, 08 Jan 2002 19:49:46 -0800
I was always taught that a boat turned around it's center of flotation, which is
somewhere around your rear end!  You can't turn a boat without turning both ends.

John Blackburn

Jed wrote:

> Hi Peter,
>
> - My boat tracks very straight even when edged if
>   I am not using some kind of turning stroke
>
>         It is not uncommon for a boat to require a sweep stroke to initiate a turn
> before edging will have any effect. SO it's OK and normal to need to perform
> a sweep stroke to get your boat to turn.
>
> - The most I can edge this boat, which is usually
>   carrying some load in the rear hatch, is to get
>   the coaming to the level of the water line. I
>   can't edge the boat to get the coaming below the
>   water line without leaning as well. If I increase
>   the thickness of knee pads my feet go to sleep
>   although I'm still modifying along the lines
>   suggested in earlier posts.
>
>         To a lesser or greater extent all edging is leaning. We edge our boats by
> moving our center of gravity to one side or the other. The boat reacts by
> listing, lowering the edge beneath the center of gravity. Move your torso to
> the left the boat edges on the left. People describe this as lifting the
> opposite knee, but that happens after you move your CG (Center of
> Gravity)and is really a way to keep from falling over.
>
>         The boat does not know or care if your torso is vertical or leaning at an
> angle. It only cares about where your CG is relative to the boats center of
> bouyancy and the degree of heel (edging).
>
> - If the boat is leaned it will almost turn on a dime
>
>         If you need to lean to get your boat edged enough to turn quickly, then
> have at it. Lot's of shorter paddlers do the same thing as do paddlers in
> relatively wide boats.
>
> -From what is being said on Paddlewise I think my real problem is not
> leaning
> enough with a good enough support component in the stroke so information on
> blade angle and body lean and their variation as the paddle passes through
> the water would be particularly welcome.
>
>         I heard things a bit differently. Steve Scherrer taked about moving the
> stern rather than the bow. I'll let him go into it in greater detail but I
> agree completely with his explaination. I will say just this, to turn the
> boat while moving forward one must move the stern, not the bow. To try and
> move the bow is a waste of time.
>
>         I would consider two things; firstly seakayaks are designed to run straight
> when on an even keel. So to turn you need to edge the boat. A little edging
> is good, more edging is better. This will lift the fine ends out of the
> water, shortening the waterline and present a much more manouverable (sp)
> hull form to the water.
>
>         What ever support is gained from your paddle is done at the expense of
> turning or propulsion. If you use your paddle for support during a sweep
> then you are not getting the most turning force out of that sweep. Many
> paddlers set their paddle for some support during a sweep but it's most
> effective to keep the paddle vertical to the path and apply support only as
> needed by rotating the paddle blade.
>
> -I'ld be very interested in what degrees of turn with a forward sweep are
> achievable if anyone happens to have assessed this.
>
>         After I initiate my turn with a sweep stroke on the opposite side, I can
> ride the carved turn for 90 degrees or so. This works going forward or in
> reverse.
>
> Good Luck,
> Jed
>
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> PaddleWise Paddling Mailing List - Any opinions or suggestions expressed
> here are solely those of the writer(s). You must assume the entire
> responsibility for reliance upon them. All postings copyright the author.
> Submissions:     PaddleWise_at_PaddleWise.net
> Subscriptions:   PaddleWise-request_at_PaddleWise.net
> Website:         http://www.paddlewise.net/
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From: Jed <jluby_at_teamnorthatlantic.com>
subject: RE: [Paddlewise] Bad forward sweep
Date: Tue, 8 Jan 2002 23:06:17 -0500
Hi John,

John wrote:
>I was always taught that a boat turned around it's center of flotation,
which is
>somewhere around your rear end!  You can't turn a boat without turning both
ends.

	While it's my belief that the boat actually turns around the boat/paddler's
center or gravity when at rest, descibing this as it's center of floatation
is close enough for me. With regard to turning the boat by turning both
ends, this is true *as long as the boat is not moving* but different forces
come into play when the boat is moving.

	When the boat is *moving forward* there exists a bow wave that has a
similar effect as pushing the bow deeper into the water, retarding any
tendency for the bow to move left or right appreciably. The first part of a
forward sweep is pushing against this bow wave and having little effect. The
middle part of the sweep cannot turn the boat either because the bow wave
again fights any effort to move the bow left or right. So the middle part of
the sweep tends to move you forward. But the last part of the sweep is
acting against the stern that is not "anchored" by a bow wave and may in
fact be in a wave trough. This makes it possible to pull the stern  towards
the paddle during the last phase of the forward sweep, in effect performing
a stern draw.

	A clear example of this can be seen by taking your boat up to speed, say
about 4 knots. Then try to turn the boat by doing only the first 1/2 of a
forward sweep. Count the number of 1/2 sweeps that are required to turn the
boat 180 degrees. Then perform the same test only this time use only the
last 1/2 of the sweep stroke. To keep things easy, try to do the turns with
no edging of the boat and be sure to take the last 1/2 of the sweep all the
way to the stern. Think hit the boat with the paddle. Most people find that
the boats turn with significantly fewer strokes when they use the last 1/2
of the sweeps compared to the first 1/2 of the sweep stroke.

	There are other people on this list, much more technically inclined than I,
that can do a much better job of explaining why this works. I only know that
it works and my own simple model that helps me understand why. Hopefully one
of our engineers will step in and correct/clarify my explaination.

Jed


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From: Nick Schade <schade_at_guillemot-kayaks.com>
subject: Re: [Paddlewise] Bad forward sweep
Date: Wed, 9 Jan 2002 10:10:49 -0500
One of the goals of leaning a boat is essentially to give it more 
rocker. Even a kayak with a very straight keel will appear to the 
water to have a lot of rocker when leaned to one side. The degree of 
lean or edging required to get this effect will depend on the boat, 
and leaning by itself may not be enough to make some boats turn, you 
will still need to apply a steering force with a sweep.

As you turn, your center of gravity wants to stay going straight. 
This can actually accelerate the rate the boat turns. As you initiate 
your turn the bow will be exposed to water pressure on the side that 
is on the outside of the turn, actually so will stern. But if you 
lean forward slightly it will drive the bow down, causing the 
pressure on the bow to increase while decreasing the pressure on the 
stern. This by itself might be enough to get the boat turning. You 
will also may get a small amount bow-down pressure just do to 
deceleration (like applying brakes in a car,  where the car leans 
squats in front slightly).

To continue the turn, the stern needs to slide sideways through the 
water faster than the bow. Leaning towards the outside of the turn 
will turn any "skeginess" at the stern away from the sideways moving 
water making it easier to get by. But if the general flow of the 
water is still along the length of the boat, it will want to stay 
going that way. You somehow need to break the stern free of the 
flowing water and get it moving some other direction. The best way to 
do this is pulling in strongly towards the back of the boat at the 
end of your sweep stroke. Once the water is flowing side ways across 
the stern and the stern is swinging outwards more freely it will tend 
to keep doing that, until you change something.  To stop the turning 
you generally only need to return the kayak to an even keel, although 
some boats will continue turning until you stop it with a slight 
sweep on the other side.

Nick


-- 
Nick Schade
Guillemot Kayaks
824 Thompson St
Glastonbury, CT 06033
(860) 659-8847

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