boat behaviour ?

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Keith White
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boat behaviour ?

Post by Keith White »

edging and carving: the same ?

If i edge my sea boat left, I turn right. If I set up 'right edge', sweep right, edge, or mostly 'lean' left, boat goes left if I turn in to look where I'm going.

However: my short boat, edge left, goes left regardless of whether I look left, or right.

Why ?
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Re: boat behaviour ?

Post by TechnoEngineer »

With a displacement hull, edging the boat makes it behave like an aircraft wing (on its side). With a planing hull, it carves, particularly when there is a hard chine ("rails").
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Keith White
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Re: boat behaviour ?

Post by Keith White »

Cheers for the explaination. I thought I was going nuts.
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andibs
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Re: boat behaviour ?

Post by andibs »

I had this really brought home when I got some coaching last week. I was asked to turn right so I swept on the left side and leaned right to try and put it on what I thought was an edge. I was them asked to turn right by simply lifting my right knee. Try it and see. What was explained to me was that the boat wants to go to the highest side and by sweeping and leaning we are actually over powering the boats natural urge thus hard work on longer paddles

Have a play - it was an eye opener for me

Andy

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Re: boat behaviour ?

Post by Mikers »

It's all to do with the shape of the hull that's in the water, and the asymmetry of that shape.

For example, moderatlely lean a sea kayak to the right. The water line on the left side of the boat will be a long straight line from bow to stern (formed by the straight 'keel'). On the right side of the boat, you'll have a curve.

In contrast, on a river boat, as you lean it over to the right, you'll get a straight(ish) edge on the right hand side - formed by lowering the rails into the water and a curve on the left hand side (from the rocker of the boat).


Interestingly, if you really lean the sea boat over, you'll get the hard edges at the nose and tail to come out of the water. When this happens, the turn direction from your edge will reverse and will once again be the same as a river boat.

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Re: boat behaviour ?

Post by Ken_T »

Hi,
Most conventional boats will tend to turn so that you are edging out of a turn, ie lifting the right knee tends to make the boat turn right. Edging into a turn is usually done to improve stability.
Ken

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Mike Mayberry
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Re: boat behaviour ?

Post by Mike Mayberry »

Ken_T wrote:Hi,
Most conventional boats will tend to turn so that you are edging out of a turn, ie lifting the right knee tends to make the boat turn right. Edging into a turn is usually done to improve stability.
Ken

The stabilty comes from your core, regardless of whether it's an inside or outside edge turn. When crossing eddylines an inside edge is definately more stable for obvious reasons. There is a big diference in speed, momentum and the type of turn produced from an inside and an outside edge turn. It's important to play with both to recognise them so that you have a greater choice of which is appropriate in any given situation.

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Edging and the low brace turn

Post by nickcrowhurst »

This potentially confusing phenomenum was bought home to me some years ago when I owned a Capella RM Mk 1 with the square hatches. When following the text book instructions to perform a low brace turn, I consistently turned "the wrong way", however much I edged and leaned, and however much I trailed the blade on the water slightly aft of my hips, and however much I swept in the forward quadrant before changing edge. I probably managed a turn in the "correct" direction about one time in five. I was under the eye of my excellent Level 5 coach, undergoing old 4* training, and following every instruction. After many frustrating attempts, he decided we should give up and have lunch. I still don't know if it was my incompetence, or the shape of the hull, that caused this, or a combination of the two.
Nick.

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MikeB
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Re: boat behaviour ?

Post by MikeB »

The original Capella was known for this, depending on load. Mike

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Jim
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Re: boat behaviour ?

Post by Jim »

Keith White wrote:edging and carving: the same ?
No, but edging can be part of carving.

Edging is tilting the hull from the hips whilst keeping the body upright.
Carving is a type of turn where the deck edge (preferably with a sharp transition) is immersed to provide grip on the water through the turn, which makes the boat carve dynamically in the direction it is tilted. Much of the time carving is done by edging, but if you watch serious surfers you may identify that they sometimes lean the boat into a carve by throwing themselves off of static balance with their CG out from the boat to the inside of the turn. You need to be moving fast to use lean rather than edge, a bit like riding a bike.

All boats are different shapes and respond differently to edge, and can respond differently depending whether they are full or empty. Some boats are fairly neutral and actually depend more on the last stroke than on which way they are edged, but my experience seems to be that unloaded sea kayaks generally turn away from the low side when edged.

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Re: boat behaviour ?

Post by nickcrowhurst »

MikeB wrote:The original Capella was known for this, depending on load. Mike
Thanks Mike, that's good to know.
Nick.

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