-- Last Updated: Sep-02-16 11:58 AM EST --
We have noticed that some have flat blades past the transition from the loom and some are elliptical. The blade surfaces are concave or flat.
Is there an advantage either way?
No answer for you
But, I had one blade I carved flat on one side and convex on the other. I never decided which I liked better. I’d paddle with the flat side and it would feel weird, but after some time I’d think, oh, ya, this is it, how it should be. Then I’d paddle the convex side, it would feel weird for a bit, then I’d think, yep, this is how it should be.
Not surprisingly, the flat side is slicey.
Most recent blades have been convex on both sides, so I guess maybe I did make up my mind.
~~Chip
I’ve Never Seen Concave
Mine are convex. I remember a thread about those paddles that were super-convex on one side and ‘normal’ on the other side. I asked what the purpose of the extra meat on one side was. I was told it reduced flutter.
The best shape for GP blades is…
…lenticular (lens-shaped). It creates a smooth, quiet flow of water over the blade, increasing lift and efficiency, assuming that you’re using a canted stroke. The thinner the blades are at the edges, the quieter and more efficient the paddle will be.
Think you (OP) meant convex
Did you mean convex?? Concave is scooped out and I have never seen a GP that is concave, though I have seen some Aleut style paddles with slightly concave “dishing” of the inside of the blade.
I have two GP’s that I use and one has flatter blades and square off ends. I quite prefer the other which is a fully rounded elliptical blade with no sharp edges or corners. It’s smoother and quieter yet seems to provide just as much power in propelling the boat.
You might get more responses and opinions than you can imagine if you posted this question on the QajaqUSA.org Greenland aficionado forums.
flat are easier to shape
although not as quiet or efficient as lenticular which has sharper edges than elliptical.
Good to hear from you Bryan.
I’ve progressed a little in my paddle making since you first advised me about a century ago.
well
Lenticular or flat…sharp edges are totally independent of the face shape. as are all other attributes of a carved Greenland paddle.
Lenticular is the traditional shape…not flat
and works well with the canted stroke.
Best Wishes
Roy
A better question is…What shape of tip? since through-out time…tip shape has changed, not the lenticular face shape. The flat paddle face is a recent thing not traditionally part of a historic Greenland paddle. some mainland Inuit like the Copper Inuit used flat faced paddles…Soooooo… flat faced are not really traditional for Greenland.
answer
to answer your question in more detail.
The Lenticular shape imparts a couple of things that, for a Greenland Seal Hunter, would or could mean life of death.
One is the strength of the shape {forget weight, it mattered very little to a hunter} A seal hunter may cover 18 or 20 miles in a day of hunting going to and from the hunting area. If successful, might have to tow back up to 1000 lbs of meat. They didn’t carry a spare paddle…only had one. If that paddle broke, they might not make it back. They could die and the meat wouldn’t make it back either…so the possibility of their entire family starving was also real.
Another attribute of the higher volume lenticular shape was flotation. The paddle was also used as an outrigger and a brace for many of the seal hunters activities…the more flotation, the better the brace against the surface of the water.
To get wet might mean death. Climbing in or out of the kayak onto an ice flow or shore …staying dry was very important.
The new search for light weight is a new concept and shows the way Non-Seal Hunters think. The day is upon us where light weight is more important than strength. Paddling and subsistence hunting is not what very many do with a kayak…much less in the harsh conditions sometimes encountered just to keep from starving to death. Today most carry a spare paddle, because they can…plenty of deck space if you don’t have a harpoon, killing lance, line tray etc on the deck.
I hope some of this helps. {the lenticular shape also works better for a canted stroke YMMV}
Best Wishes
Roy
Yes. I meant convex. or an outy
as opposed to an inny.
weight vs funtction
Not sure I agree with the premise - I don’t think anyone makes a flat-faced GP to save weight. I think it’s done because we have tools that make a flat face easy to fabricate.
The difference in weight between a lenticular profile GP and one with flat faces has got to be close to negligible - I don’t think it would be noticeable. The difference in buoyancy would be even less. A lenticular blade would be stronger, but not by much - the area distribution of the two is quite similar.
However, the hydrodynamic advantage of lenticular over flat profiles is significant and important. Flat faces tend to encourage flow separation, which generally results in backflow, eddies, increased vorticity and ventilation of the blade. All of these processes are noisy and reduce lifting forces (or thrust, if you prefer) created by the paddle. Also, as you point out the tip shape is important.
If
you are talking presently made commercial carbon Greenland Paddles, then you are correct.
But if you are considering home made wood Greenland Paddles, {past and present} then I believe you are making assumptions that are not necessarily accurate from what I have personally seen as far as volume comparisons and available flotation. {stiffness and strength included}
{I would also like to believe that the flat blade is not a product of lazy wooden paddle makers and instead was part of their intended design…obviously with carbon, a flat blade would have been intentional.
again…obviously YMMV
Best Wishes
Roy
I Found It - Aleut
I used an Aleut style once and wasn’t impressed. I didn’t see or feel any advantage it had over my GPs and it had a couple of disadvantages. Here’s what these folks have to say about it:
http://www.ravenwoods.org/aleut-paddle/
Aleut
The explanation given on that site as to how the Aleut paddle functions is not believable, in my opinion. I doubt the rib does much to encourage turbulence, or that turbulence is particularly beneficial. Turbulence increase skin friction (viscous drag), which is a small portion of the drag on a bluff body - the largest component is form drag, i.e. pressure drag based on the shape of the object in question.
The explanation also implies that GP and Aleut paddles function solely in drag mode, which is true only if they aren’t canted during use. A canted GP or Aleut paddle will generate a small lifting force, a component of which points in the direction of motion, acting as thrust.
I’ve heard it argued that the rib acts as a stagnation line on the paddle and helps reduce flutter, which seems reasonable. I’m sure it increases bending strength.
Also, the Aleut paddle shown on their site does not look much like Aleut paddles I’ve seen and used. The tip shape seems particularly wrong, but it all looks off to me.
You’re correct…
…that looks nothing like a traditional Aleut paddle. It’s like the Betsy Bay “Greenland” paddle that looks nothing like the paddles that Greenlanders use. Apparently, some people just like to make up weird paddle designs and try to pass them off as “traditional”.
Makes me wonder if the originators
of GP and Aleut paddles had a design shop where their engineers worked with fluid mechanics to improve performance.
Whether you call the “engineers”…
– Last Updated: Sep-09-16 4:46 PM EST –
...may be up for discussion, but it's obvious that they had an understanding of fluid dynamics based on experience and living on the water. Whether by trial and error, serendipity or just luck, they learned what worked best for their needs.