paddle blade dihedrals

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akhawk
akhawk
WA
1085 posts
WA, 1085 posts
5 Nov 2011 12:53pm
Does a dihedral on a paddle blade make much difference?
What are the pros and cons of a dihedral on the blade face?
Cheers.
DavidJohn
DavidJohn
VIC
17570 posts
VIC, 17570 posts
5 Nov 2011 4:41pm
They are supposed to reduce wobble/flutter but I'm not convinced because not all blades without dihedral flutter and not all paddles with dihedral are flutter free.. I think it's often a marketing thing and really often there to give the blade to shaft strength.. They (dihedral) might help with learners or inexperienced paddlers and someone with poor technique over powering the blade when paddling into a strong headwind etc.. I took this vid last week so I could see how my paddle is working as it goes in and out of the water.. Boring vid unless watching someone paddling interests you.. .. You can see that even with its perfectly flat face blade there is very little (if any) wobble/flutter.

DJ




Th0m0
Th0m0
QLD
529 posts
QLD, 529 posts
6 Nov 2011 7:30am
I recently swapped over to QB paddles with a dihedral after using Kiakaha (flat) paddles for the last 2.5 years. I've been very happy with the Kiakahas and only changed over to try somthing different. There is definetly a difference. The pull feels smoother through the water with the dihedral and I don't seem to hit the rail of my board as much. That probably means I was fluttering a bit with the flat blade.
I'm not saying one is better than the other, but it is different and which one you like will come down to personal preference. I think if you're really interested in getting your paddle stroke technically correct for racing the dihedral will help, in the surf it probably doesn't make much difference.
PonoBill
PonoBill
87 posts
87 posts
6 Nov 2011 12:17pm
You make your blade not wobble. Open your lower hand so your fingers are just touching the shaft, and open your upper hand so it's just resting on the handle, then pull. A flat blade will wobble all over the place because the flow off the blade is chaotic. We get used to our paddles and we make them stop wobbling.

Dihedral reduces the catch though, because it directs the flow off the blade. Consider the extreme--a paddle shaped line an axe. It would have nearly 100 percent slip. As you flatten the blade the catch increase but the stability of the blade decreases.

The water running off the face of the blade meets the water being pulled toward the blade on the back and makes the vortexes.

Here's the vortex from a flat blade

here's the vortex from a Ke Nalu blade with a dihedral that has concave faces.





PonoBill
PonoBill
87 posts
87 posts
6 Nov 2011 12:21pm
You'll know firsthand pretty soon DJ--There's a box headed for Jonathan on Monday. I can't wait to hear your reaction.
DavidJohn
DavidJohn
VIC
17570 posts
VIC, 17570 posts
6 Nov 2011 6:03pm
PonoBill said...

You'll know firsthand pretty soon DJ--There's a box headed for Jonathan on Monday. I can't wait to hear your reaction.


Yes... Jonathan and I did a down-winder today and he said in a couple of days we will have them here .. I'm looking forward to seeing them and taking some pictures.. I was hoping Bill would chime in with his thoughts about dihedrals.. I find it very interesting.. I think the fact that some Kialoa paddles don't have dihedrals is not because Dave Chun from Kialoa doesn't like them.. He makes a range of paddles at the prototype stage and he lets his team riders/testers use them and the feedback is that they prefer no dihedral so he makes them that way.. Maybe the oval shaped Kialoa shaft helps control flutter.

DJ




Simondo
Simondo
VIC
8025 posts
VIC, 8025 posts
6 Nov 2011 6:09pm
I added dihedral to the blade face of a paddle of mine.

A drinking straw taped to the blade face.... and it makes most people laugh, so I leave it there!
hilly
hilly
WA
8131 posts
WA, 8131 posts
6 Nov 2011 6:41pm
DavidJohn said...
Maybe the oval shaped Kialoa shaft helps control flutter.


Good point
akhawk
akhawk
WA
1085 posts
WA, 1085 posts
6 Nov 2011 6:51pm
Do Kialoa paddles not have a dihedral or is it just certain models?
DavidJohn
DavidJohn
VIC
17570 posts
VIC, 17570 posts
6 Nov 2011 10:17pm
akhawk said...

Do Kialoa paddles not have a dihedral or is it just certain models?


The big Kialoa Nalu has a slight dihedral.. See pics showing my Shaka Pu'u and Nalu.

The Toro and Ikaika paddles have what looks like a dihedral but it's there not as a dihedral but as a part of the paddle's design.

DJ





latman
latman
QLD
177 posts
QLD, 177 posts
6 Nov 2011 11:18pm
From years of outrigging (about 10) i can tell you that the back face NEEDS to be convex but the front can be concave /flat /convex and it will always work .
PonoBill
PonoBill
87 posts
87 posts
6 Nov 2011 11:28pm
Simondo said...

I added dihedral to the blade face of a paddle of mine.

A drinking straw taped to the blade face.... and it makes most people laugh, so I leave it there!

You should see my "mule" paddle for development and testing. Fugly.
PonoBill
PonoBill
87 posts
87 posts
7 Nov 2011 12:01am
Dave Chun has forgotten more about paddles than I'll ever know, and he makes his paddles work superbly. I honestly don't know why Kialoas work as well as they do, and I like the oval shaft.

What you will notice most about the Ku Nalu paddles is the absence of things. No noise, no wobble. Some people find it really weird at first.

I think paddle design is a lot more subtle than anyone expects. When you do see the Ke Nalu paddles you'll notice the dihedral is pretty soft and it turns into a double concave instead of a flat surface. We're actually doing four things with that design, guiding water off the face, slowing the exit as it reaches the edge, making the edge a little stiffer, and guiding air up the face of the blade to get it off the tip. All aimed at recovering the catch we lose by having dihedral. Most folks say our paddles catch "big". My huge moose of a brother says our 8 catches like a 9 and we need to make a 7". I don't know what to think about that.

The medium we're working with (water) is viscous and incompressible, the flow characteristics paddle designers are aiming for is for NONE. The best paddle would be one that did not move at all once it catches. But they do, and so all the design effort is aimed at something that doesn't go whacky when it slips through the water.

We've found almost as much improvement in catch and stability on the back of the paddle as the front. This is, after all, a wing. The water behind the blade has to move too and influences the catch and stability almost as much as the water on the front. We're probably going to go a lot further with this. I like that our paddles don't look weird, or have any odd appendages or gimmicks, but that might change over time.

I think most companies making a paddle think it's a simple thing. I think Warner, Kialo, Quickblade, and now Ke Nalu do NOT think that way, and so the paddles take a lot more effort to design and build.
PonoBill
PonoBill
87 posts
87 posts
7 Nov 2011 12:09am
Incidentally, DJ, looking at your video I can tell why your paddle doesn't wobble too much. You've got a firm grip on that thing. If I did that my wrists would ache, my shoulders would kill me, and my fingers would go numb.

You also have wobble in your paddle, You can see it right at the catch, especially on the left side where you have less control, the little wiggle. You're controlling it with your grip.

Next time you use that paddle, open your hands and see how it goes.
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