Paddle problem time
 

Rick wrote:
...stuff deleted

That's true, but...

The reason for this is that you don't need a lot of paddle in
the water to propel a boat.

...that's not the reason. If the issue were simply size, then why not
just use a smaller blade? The reason asymmetic paddles are asymmetric
is the the paddle is usually inserted at some diagonal angle to the
water. If the paddle is symmetric around the shaft line, you have more
paddle in the water below and less above, causing twist. The asymmetry
tries to compensate for that. If you use an asymm paddle upside down
(ie, the longer edge of the blade down), you create more, not less,
twist, thereby requiring a tighter grip on the paddle, thereby mucking
up your tendons.

I was not commenting on whether asymmetry will, as you say, reduce
turbulance, vibration, and cavitation. What I was saying was that you
don't need a lot of blade to propel a boat and that placing the wider
edge into the water will tend to result in excess work and stress for
the paddler (the blade, be it small or large, will only move a few
fractions of an inch when pulled against). Since we were discussing the
injury here, I was pointing out that the load of an inverted paddle may
result in undue stress on the paddler.

I said nothing about "turbulance, vibration, and cavitation", just
torque (i.e., twist). BTW, paddles don't cavitate, they ventilate,
(http://www.guillemot-kayaks.com/Design/Paddlework.html), but that's not
the point here. Yes, you don't need a wide blade to propel a boat. The
Greenlanders proved that over 2000 years ago. But I still don't follow
your point. Would you say it isn't good to totally immerse the blade? Or
that everyone should use narrow blades?

Perhaps you've never heard the arguments in favor of asymm paddles. Have
a look here for a nice explanation:
http://www.getoutcanoeing.co.uk/acat...ategory&page=1

--
Steve Cramer
Athens, GA

Paddle problem time
 

Steve Cramer wrote:
....stuff deleted

I was not commenting on whether asymmetry will, as you say, reduce
turbulance, vibration, and cavitation. What I was saying was that you
don't need a lot of blade to propel a boat and that placing the wider
edge into the water will tend to result in excess work and stress for
the paddler (the blade, be it small or large, will only move a few
fractions of an inch when pulled against). Since we were discussing
the injury here, I was pointing out that the load of an inverted
paddle may result in undue stress on the paddler.


I said nothing about "turbulance, vibration, and cavitation", just
torque (i.e., twist). BTW, paddles don't cavitate, they ventilate,
(http://www.guillemot-kayaks.com/Design/Paddlework.html), but that's not
the point here. Yes, you don't need a wide blade to propel a boat. The
Greenlanders proved that over 2000 years ago. But I still don't follow
your point. Would you say it isn't good to totally immerse the blade? Or
that everyone should use narrow blades?

What is written on the site in reference to cavitation vs. ventilation
is as follows:
"Neither is any good, but what your average kayaker creates is ventilation."

My paddle cavitates when I pull hard. It goes in clean, takes no air
down with it, and it generates air bubbles on the low pressure side of
the blade, which is, by definition, cavitation (cavitation is not
limited to propeller blades, but occurs much more frequently due to the
intense pressures the blade places on the water). If I pull really hard,
the vortices on the blade will suck air down toward the paddle, creating
ventilation. This is tremendously inefficient and causes "slippage," as
referred to on the website you cited.

But that, again, isn't the point. Torque isn't the issue here. Paddles
do not generally twist in use. While there may be unbalanced pressure on
various points of the blade, the shaft should not torque on a
well-designed blade, regardless of symmetry.

What I am discussing has little to do with the symmetry of the paddle,
but upon the stresses which cause injury to paddlers. Too much blade
can, and does, cause injury. Using an asymmetric blade upside down puts
the more blade into the water, thus putting more pressure on the
paddler. Whether or not this causes injury is a function of how tightly
the paddler holds the blade and how much stress the lever (paddle)
directs to the joints where tendons meet bone.


Perhaps you've never heard the arguments in favor of asymm paddles. Have
a look here for a nice explanation:
http://www.getoutcanoeing.co.uk/acat...ategory&page=1



I use an asymmetrical paddle and know why. We are discussing two
different things here. More blade = more stress on paddler. Longer shaft
also translates to more stress on paddler, but there are points of
diminishing returns on that. A shorter shaft with a higher cadence
produces fewer injuries than a long shaft. If the shaft is too short,
however, a great amount of efficiency is lost.

A large blade combined with a long shaft can cause injury more quickly
than a narrow blade (though my understanding is that the shaft length is
the bigger issue).

Rick

Paddle problem time
 

Rick wrote:
Steve Cramer wrote:
...stuff deleted

I was not commenting on whether asymmetry will, as you say, reduce
turbulance, vibration, and cavitation. What I was saying was that you
don't need a lot of blade to propel a boat and that placing the wider
edge into the water will tend to result in excess work and stress for
the paddler (the blade, be it small or large, will only move a few
fractions of an inch when pulled against). Since we were discussing
the injury here, I was pointing out that the load of an inverted
paddle may result in undue stress on the paddler.

I said nothing about "turbulance, vibration, and cavitation", just
torque (i.e., twist). BTW, paddles don't cavitate, they ventilate,
(http://www.guillemot-kayaks.com/Design/Paddlework.html), but that's
not the point here. Yes, you don't need a wide blade to propel a boat.
The Greenlanders proved that over 2000 years ago. But I still don't
follow your point. Would you say it isn't good to totally immerse the
blade? Or that everyone should use narrow blades?

What is written on the site in reference to cavitation vs. ventilation
is as follows:
"Neither is any good, but what your average kayaker creates is
ventilation."

My paddle cavitates when I pull hard. It goes in clean, takes no air
down with it, and it generates air bubbles on the low pressure side of
the blade, which is, by definition, cavitation (cavitation is not
limited to propeller blades, but occurs much more frequently due to the
intense pressures the blade places on the water). If I pull really hard,
the vortices on the blade will suck air down toward the paddle, creating
ventilation. This is tremendously inefficient and causes "slippage," as
referred to on the website you cited.

Never seen you paddle, but I'm betting you don't generate enough power
to lower the pressure on the back side of the paddle to the point that
water turns to vapor. That's cavitation. Air has nothing to do with it.
Kayak paddles ventilate.

But that, again, isn't the point. Torque isn't the issue here. Paddles
do not generally twist in use.

Except, perhaps, asymm blades used upside down.

While there may be unbalanced pressure on
various points of the blade, the shaft should not torque on a
well-designed blade, regardless of symmetry.

Huh? Unbalanced pressure causes torque. Push harder on one side of the
blade, and it will twist around the shaft.

What I am discussing has little to do with the symmetry of the paddle,
but upon the stresses which cause injury to paddlers. Too much blade
can, and does, cause injury. Using an asymmetric blade upside down puts
the more blade into the water, thus putting more pressure on the
paddler. Whether or not this causes injury is a function of how tightly
the paddler holds the blade and how much stress the lever (paddle)
directs to the joints where tendons meet bone.

Perhaps you've never heard the arguments in favor of asymm paddles.
Have a look here for a nice explanation:
http://www.getoutcanoeing.co.uk/acat...ategory&page=1

I use an asymmetrical paddle and know why. We are discussing two
different things here.

Indeed. I keep trying to discuss the poor guy who messed up his arms
using an asymm AT paddle upside down. You seem to be talking about
somehting else. Go get your own thread.

More blade = more stress on paddler. Longer shaft
also translates to more stress on paddler, but there are points of
diminishing returns on that. A shorter shaft with a higher cadence
produces fewer injuries than a long shaft. If the shaft is too short,
however, a great amount of efficiency is lost.

A large blade combined with a long shaft can cause injury more quickly
than a narrow blade (though my understanding is that the shaft length is
the bigger issue).

Well, yes, but we have no idea how big or small the OP's paddle blades
and shaft length were, do we?

OK, Rick, you've obviously convinced yourself, so if you say so...

Meantime, let's use our asymm blades right side up, OK?

--
Steve Cramer
Athens, GA

Paddle problem time
 

On 11-Jul-2004, Rick wrote:

My paddle cavitates when I pull hard. It goes in clean, takes no air
down with it, and it generates air bubbles on the low pressure side of
the blade, which is, by definition, cavitation (cavitation is not
limited to propeller blades, but occurs much more frequently due to the
intense pressures the blade places on the water).

Intense pressures? If you can cause a paddle blade to cavitate, you're
the most powerful paddler the world has ever seen. BTW - cavitation bubbles
are not air - they are water vapour. And they collapse almost immediately.
Check the damage on your blade. The collapse will cause severe pitting.

A paddle has an area of 80-120 sq in, typically, with some bigger still.
If yours is, say, 100 sq in and you generate an average of 0.5 psi on the
back side, that's a total force of 50 lb. It takes most fast sea kayaks
less than 14 lb to hit hull speed.

Please provide a reasonable pressure profile that will generate a peak
of 15psi and an average of less than 0.15 psi (that's a 100:1 spread).

Paddles ventilate. End of story.

Mike

Paddle problem time
 

Frank Healy wrote:

http://www.lightnings.co.uk/ Adults Paddles Guidelines PDF

Sorry it did not help - it was published to assist the youngsters who
attended a coaching day at a regatta last year. One of the GB coaches
gave a talk to parents and when the website was set up earlier this
year the information was published for their benefit...

Frank, do you (or the kids) use bent shafts in competition?

What are your opinions about feather angle? Do competitors
decide for themselves? What is the most common choice?

Paddle problem time
 

Steve Cramer wrote:

http://www.atpaddle.com/WhitewaterGateway.html

The AT3 and AT4 paddle blades look very poorly designed to me.
In any asymmetric paddle, the surface area on one side of the axis
should be equal to the surface area on the other side of the axis,
to help prevent flutter when the paddle shaft is loosely held.
Preventint flutter also helps avoid too-tight gripping.

I can't quite discern axis in the AT2 picture, but the AT3 Edge
and to a lesser extent the AT4 Play seem to have more surface area
on the upper half. The ATX and Zen blades look more equalized.

Paddle problem time
 

"Bill Tuthill" wrote in message




Frank, do you (or the kids) use bent shafts in competition?

What are your opinions about feather angle? Do competitors
decide for themselves? What is the most common choice?


No bent shafts are not used in sprint - at least I have never seen
anyone use them. I have just purchased a new paddle for my grandaughter
which is being set at 65deg against the standard 90deg - many of the
problems asociated with injury are due to incorrect paddling action. If
you study any sprint/marathon competition videos then you will see
people paddling in a style that has a great deal of scientific research
behind it. When you are competing for Olympic Gold you ensure that you
are using the most effective stroke. At present one of our coaching team
is working with the youngsters to ensure that they paddle correctly.
This will reduce the risk of injury. When I moved into racing I needed
to relearn much that I had been taught, it took a while to perfect my
paddling technique but I found that I could paddle faster and further
with less effort at the end. With regard to how much of the blade goes
in the water this is a red herring. If you only need half the blade size
why not reduce the size of the blade? - The answer is to get decent
coaching and you will then get the maximum benefit. The problem with
being taught by people who have picked it up with no formal teaching is
they teach their bad habits.

Frank Healy


--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

Paddle problem time
 

On 12-Jul-2004, "Frank Healy" wrote:

The problem with
being taught by people who have picked it up with no formal teaching is
they teach their bad habits.

But what about those _with_ formal training that teach bad habits?

I've met folks both with and without formal training and they can have
both good and bad technique. Add to this that paddling technique has
been in a state of flux, to some extent, recently and you get all sorts
of techniques being taught with no clear idea (for the student) of what
is right.

Another problem is that most racing is short distance (i.e. Olympic
C and K) and those techniques are inappropriate for long distance
or for recreation.

Mike

Paddle problem time
 

The less blade surface area the higher your cadence will be thus requiring
less effort. The more surface area the slower your cadence yet more
powerful the stroke. That's why it feels like you're going faster with a
smaller blade. This works great for some people but not everyone as it
depends on their own personal strength and paddle style along with what type
of water they paddle.

Courtney

"Frank Healy" wrote in message
news:391c5cc48d9ae45ce88d1e75f21feac0.8098@mygate. mailgate.org...
"Bill Tuthill" wrote in message




Frank, do you (or the kids) use bent shafts in competition?

What are your opinions about feather angle? Do competitors
decide for themselves? What is the most common choice?


No bent shafts are not used in sprint - at least I have never seen
anyone use them. I have just purchased a new paddle for my grandaughter
which is being set at 65deg against the standard 90deg - many of the
problems asociated with injury are due to incorrect paddling action. If
you study any sprint/marathon competition videos then you will see
people paddling in a style that has a great deal of scientific research
behind it. When you are competing for Olympic Gold you ensure that you
are using the most effective stroke. At present one of our coaching team
is working with the youngsters to ensure that they paddle correctly.
This will reduce the risk of injury. When I moved into racing I needed
to relearn much that I had been taught, it took a while to perfect my
paddling technique but I found that I could paddle faster and further
with less effort at the end. With regard to how much of the blade goes
in the water this is a red herring. If you only need half the blade size
why not reduce the size of the blade? - The answer is to get decent
coaching and you will then get the maximum benefit. The problem with
being taught by people who have picked it up with no formal teaching is
they teach their bad habits.

Frank Healy


--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

Paddle problem time
 

Michael Daly wrote:

I've met folks both with and without formal training and they can have
both good and bad technique. Add to this that paddling technique has
been in a state of flux, to some extent, recently and you get all sorts
of techniques being taught with no clear idea (for the student) of what
is right.

Another problem is that most racing is short distance (Olympic C and K)
and those techniques are inappropriate for long distance or recreation.

Exactly. Frank Healy mentioned 90 degree feather as being standard,
but for long distance and recreational paddling, it was long ago decided
that this extreme angle exacerbates RSI (repetitive stress injuries)
so feather angles moved to 75, then 60, and now 45 or less. A worthwhile
tradeoff of increased wind resistance for less likelihood of RSI.

For whitewater sometimes you need a big blade to get in a quick stroke
to stay on-line. Also in whitewater, some blade designs perform better
for backpaddling than others, a trait racers needn't worry about.

It's an interesting datapoint that racers are NOT using bent shaft...