Anglesey Eye Candy

[EEL]

Ran across these three Youtube clips. Production values low, but nice eye candy. Quite a bit to learn as well by watching how strokes are used, paddler awareness, etc.

And yes, the camera paddler was doing a 5* Assessement using a GP.

I liked the part where the paddler in the white Romany(?) within a distance of maybe 30 along a cliff used a draw, a crossbow rudder and a stern rudder for directional control. Blended seamlessly with forward stroke it seemed.

Ed Lawson

[tyson]

And yes, the camera paddler was doing a 5* Assessement using a GP.

I noticed that their GP's seem to be a bit wider than most, yet probably still narrow enough to use as a GP. I've noticed that GP's have a VERY hard pull to them if you are precise with your catch to avoid any cavitation* and have a proper cant to the paddle. I suspect that the narrow blade is a factor in GP's being so sensitive to cavitation. (It is also a factor in the efficiency of a GP) So, I wonder if their wider bladed GP's are more forgiving of this, thus making it easier to put in a quick power stroke without quite so much discipline and technique?

* Cavitation is not really the correct term here, but it seems to be what I've heard people use. Cavitation is the formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapor pressure. Here it is surface air getting into the vortex behind the blade, not water vapor "boiling" off the back side of the blade due to low pressure. ...unless you have one heck of a powerful stroke.

[Pintail]

Hey, I thought you were a pilot: so -- cavitation is <exactly> the right word! I have never noticed what you describe as a "hard pull" on a Greenland paddle; but there we are. I believe that the cause of the drag or cavitation experienced when using these paddles is simply due to the stocky chord of the Greenland concept, which is why it is necessary to use the paddle at a slight "falling off" angle -- not so? Propellers of many aircraft are similarly long and narrow (ie, having a high aspect ratio), yet they do not suffer the same cavitation. Greenland paddles, remember, are essentially a crude design. It must be the fat chord to blame, don't you think?

[kate]

I noticed that their GP's seem to be a bit wider than most, yet probably still narrow enough to use as a GP. I've noticed that GP's have a VERY hard pull to them if you are precise with your catch to avoid any cavitation* and have a proper cant to the paddle. I suspect that the narrow blade is a factor in GP's being so sensitive to cavitation. (It is also a factor in the efficiency of a GP) So, I wonder if their wider bladed GP's are more forgiving of this, thus making it easier to put in a quick power stroke without quite so much discipline and technique?

They look like standard size GP's to me.

I have not noticed that GP's are sensitive to cavitation. It is extremely rarely noticeable for me. The only time I find it to happen is if I am very sloppy with the entry angle of the blade, and then pull very hard on it. I don't think I could make it happen purposely. My paddle is the smallest, narrowest one I have ever seen (sized to fit me).

Could be that I just have a well-designed stick. Yay Don Beale!

Thanks for sharing the clips. Looks like exciting paddling!

kate

[Brian Nystrom]

They look like standard size GP's to me.

One of them looks to have 4" - 4.5" blades, but the others look like a more typical 3.5".

I have not noticed that GP's are sensitive to cavitation.

The term you guys are looking for is "aeration", as cavitation can only occur at high speeds.

It is extremely rarely noticeable for me. The only time I find it to happen is if I am very sloppy with the entry angle of the blade, and then pull very hard on it.

That's typical. Reaching too far forward for the catch is a common cause, as it changes the cant angle of the blade. As you said, it takes sloppy technique to cause aeration. There is nothing inherent in the blade design that makes it prone to it.

Could be that I just have a well-designed stick. Yay Don Beale!

The shape of the blade definitely plays a big role. Blades that are overly thick and "clubby", with blunt edges tend to aerate more. They're also noisier and less efficient. A more refined blade shape is better for paddling, if not for doing chin-ups.

[bob budd]

One nice thing about 3.5" wide blades is you can make them at home from 2x4s and craft them to your own particular idiom. I'm much better off with a blade that's a bit "clubby" and a thicker shaft as well as I'm rough on my toys.

[Brian Nystrom]

One nice thing about 3.5" wide blades is you can make them at home from 2x4s and craft them to your own particular idiom. I'm much better off with a blade that's a bit "clubby" and a thicker shaft as well as I'm rough on my toys.

It's interesting that 3.5" is the most common width here, primarily due to the availability of 2x4 dimensional cedar. Historic Greenland paddles are almost always narrower. I suspect that's due to them using as little of their precious wood resources as necessary to make an effective paddle. One of these days I have to make my self a narrower twig to see if I'm missing something.

[Pintail]

Brian, I believe "cavitation" was <exactly> the word I wanted -- and I stand by it. Here is one definition:

<The sudden formation and collapse of low-pressure bubbles in liquids by means of mechanical forces, such as those resulting from rotation of a marine propeller>

I think "aeration" would imply other means to put air deliberately into water, whereas cavitation occurs in marine or aviation airscrews -- or behind a coursely-controlled paddle!

It's really a matter of controlling overall drag, mostly by good design, and any wing or propeller will have drag occuring all along its trailing edge -- the best wings and propellers minimize the total drag by controlling those vortices and allowing them to occur almost entirely at the very tip.

I may not be an engineer in fluids; but I know something about aviation applications.

[tyson]

Brian, I believe "cavitation" was <exactly> the word I wanted -- and I stand by it. Here is one definition:

<The sudden formation and collapse of low-pressure bubbles in liquids by means of mechanical forces, such as those resulting from rotation of a marine propeller>

The reason that the definition of cavitation is tied to low-pressure and collapse is that the bubbles are not air bubbles. In the case of water, it is water vapor bubbles.

Cavitation is when the pressure is dropped low enough to cause the water to boil at ambient temperature. The bubble then collapses and returns to its liquid state when it travels out of the low pressure region. This is a problem on boat propellers and hydrofoils where the pressures generated are very high (or low).

As paddlers, we are not creating pressures which are that extreme. The bubbles we see are air that came from above the water. These bubbles float to the surface, they do not collapse.

[Brian Nystrom]

Brian, I believe "cavitation" was <exactly> the word I wanted -- and I stand by it. Here is one definition:

<The sudden formation and collapse of low-pressure bubbles in liquids by means of mechanical forces, such as those resulting from rotation of a marine propeller>

Therein likes the rub. Cavitation is caused by low pressure created by a fully submerged object moving at high speed. The low pressure causes dissolved gasses in the water to form bubbles which collapse once the pressure returns to a level above the point where cavitation occurs. While a marine prop can do this, there is no way that a person pulling on a paddle can create low enough pressure to cause cavitation. This has been discussed on other paddling sites.

I think "aeration" would imply other means to put air deliberately into water, whereas cavitation occurs in marine or aviation airscrews -- or behind a coursely-controlled paddle!

Aeration has no component of "intent". Water is aerated as it flows over rocks in a stream, but nobody is "deliberately" injecting air; aeration is a side effect of the interaction of the water and the rocks. Viewed that way, you can see that a paddle is very much the same situation, except that the water is (relatively) stationary and the paddle is moving. Surface air is drawn down into the water as a side effect of paddling (poorly, in this case). The air bubbles are being added to the water, not coming out of solution, then re-dissolving.

It's really a matter of controlling overall drag, mostly by good design, and any wing or propeller will have drag occuring all along its trailing edge -- the best wings and propellers minimize the total drag by controlling those vortices and allowing them to occur almost entirely at the very tip.

I agree.

I may not be an engineer in fluids; but I know something about aviation applications.

Air acts a fluid too, as I'm sure you're aware. The principles are the same, whether it's air, water or molten lava (YIKES!).

[tyson]

Air acts a fluid too, as I'm sure you're aware. The principles are the same, whether it's air, water or molten lava (YIKES!).

While gases and liquids are both fluids, they behave differently because a liquid is (mostly) non-compressible and can cavitate. A gas is compressible and does not cavitate. Cavitation is not a concern for aircraft.

Cheers!

Ty