-- Last Updated: Feb-23-07 1:39 PM EST --
Kind of interesting
in a half baked sort of way. It is an interesting idea that should be researched. It is not a new idea. I was reading something not long ago about someone drilling holes in their paddle to cut down on the “bite” (one of the Brozes?).
In the referenced article, there is a discussion about how it cuts down on turbulence imparted to the water, but there is no discussion on how this changes the effectiveness of the paddle. I can reduce the turbulence of my current paddle a great deal by cutting off the blades! Is this a good idea? No, because it would also reduce the effectiveness of the paddle by about 100%.
Flyswatter
By this logic, you could make an even better paddle blade from screen door mesh. That would reduce the induced eddy size to the millimeter level (that’s the mean diameter of the vortex loops created). You just a need a really big paddle to get any thrust - but you would be putting less energy into a big vortex loop, I guess. And you could slap fish with it like a flyswatter and get a free lunch while you’re at it…
As I recall, the corporal punishment crowd when I was a kid (aka the gym teacher) had a paddle with holes in it - but I think this was to more effectively raise welts on the backsides of mis-behavers (not me, I swear). Or maybe it was to reduce drag and allow the paddle to build up truly awe-inspiring velocity before the coup de grace. I’m having a hard time remembering that far back.
Seems counter-intuitive to me
– Last Updated: Feb-23-07 2:25 PM EST –
He says the reason he want to do this is to reduce turbulence in the water, and the reason he wants to reduce the turbulence is
"because there is a lot of energy involved in creating this vortex".
Seems to me that the force that creates that turbulence is also the force that moves your boat forward, especially since he recognizes that reducing the turbulence will reduce the force needed to make the stroke (and the force needed to make the stroke equals the propulsive force).
I know that the greenland paddle folks compensate for less propulsive force with a higher cadence. However, I tend to agree with the first response to this topic, and my first thought was that I can reduce that tubulence to near-zero by turning the blade 90 degrees so it lines up with the direction of my stroke. There'd be virtually no turbulence created, but the force required to move the paddle through the water would be near zero, and the propulsive force would be the same - almost zero.
Of course, I could be missing some really high-end abstract science here. It's happened before.
On that same note, swimmers open the fingers of their hands slightly to increase their propulsive force, but what I've heard is that they do this because it increases the turbulence generated, not because it decreases it. Apparently opening the fingers slightly, not too much, has the same effect as having a bigger hand because the overall surface area is bigger since the water does NOT flow easily through the little gaps between the fingers. Thus, this is not the same as drilling holes in a paddle blade which otherwise remains the same size.
Paddle / spaghetti strainer
Trepanation
There are those out there who still argue that trepanation (drilling holes in one’s head) is not only the cure to every imaginable illness, but also a way to achieve “higher conciousness.”
Perhaps the same folks are calling for drilling holes in their paddles?
Thanks, but I’ll leave my head and my paddle undrilled.
for reducing turbulences
dimples, arrangened in a pattern work far better than holes: you keep the trust of the blade.
Patend for that is already held by some moto sports helmet company in Europe, though-I had one of those years back-imagine a helmet without any turbulence and without any wind noise.
The design looked akward and was not widely accepted. But it worked great! Don’t know wether they stil make those helmets but the principle surely applies to liquids as well…
Before you start dimpling your paddles: keep in mind that wood tends to bounce back in shape when it gets wet
My non-science thoughts
first off that was about the most science I have seen since high school…and it is about paddling. WOW
Now some one needs to talk about the venturi effect. Yes some water is slipping off around the edge of the blade, but more inportantly the vortex is created because of the absence of water since the blade has pushed it. you could have the same surface area on a LONG thin blade as a short fat blade. the vortex on the later will be larger. My TurtleWorks long thin bevertail blade leaves a much smaller vortex then my Bending Branches standard paddle, but they have the same surface area.
Well I hope to see how great this person paddles with a lack of impact on the water…but also doesn’t get anywhere…so they should be alright to continue taking notes on the subject
Liveoutside
Yikes!
Maybe we are applying this concept to the wrong object in the equation! If drilling holes in an object makes it slip through the water with less turbulence, maybe we should apply that idea to the kayak hull instead of the paddle!
That’s almost like my theory that since most car accidents happen in intersections, you should try to minimize your time there, and speed up as you approach them.
Thanks for the chuckle
I know the premise was supposed to be “serious” science, but I have been home for 5 days sick doing nothing, and I am about to go stir-crazy. At this point I am easily amused, and you guys just gave me a mental lift for the day. Thanks,
Donna
Best way to minimize turbulence…
is to turn the blade sideways. Who needs holes?
Andy
Size of the vortex
You are on the right track, I think, but when you say the size of the vortex made my a long skinny blade is smaller than the vortex made by a short, fat blade, you are looking only at the vortex at the surface.
If the size of the vortex is viewed in 3 dimensions, I think you’ll find a similar volume of turbulence for EITHER blade; the vortex for the narrow blade will be small as viewed from the top, but just as big if you take into account that it occupies a much larger range depth in the water profile.
!!!FREEK!!!
lol…
Proper stroke
There are three phases to the stroke. First and in my opinion the most important is the catch. When the catch is done right the vortex behind the paddle is minimal. The object is to firmly plant the paddle blade in the water fully before beginning the next phase, the power phase. The experts liken it to throwing out an anchor and reeling in the boat. Your pulling the boat forward rather than pushing the water backward. I’ve watched the best racers in the country at the start of a race and yes they do pull some water but not as much as most of us do on a normal stroke. The energy spent pushing water backwards is wasted energy. It is energy that moved the water and not the boat.
Throwback to the 60’s and 70’s
Anybody remember all the super light drilled out aluminum and magnesium bike parts made back in the day? Before they had computers and carbon fibers they just took the lightest alloy parys and drilled a gazillion holes in them.
I don’t think it will make the paddle pull more effectively, but it might make it lighter. What if i took my old mohawk rock basher paddle and drilled out a lot of the heavy plastic and sealed the holes with packing tape. Do you think I could make it a lot lighter before it got too weak? Hmmm…
Greenland misconception!!!
“I know that the greenland paddle folks compensate for less propulsive force with a higher cadence.”
From my experience - and comparing many paddles - what you claim is not correct. Is this your experience - or just a perception? If you’ve actually observed/experienced this I have to think these are either undersized GPs or less than optimally used (using like a euro, not canted, not fully buried, etc). Less power is not my experience at all, nor is any significantly higher cadence. I would characterize this impression of GPs a misconception - like the “low angle” stroke BS.
A typical GP has equivalent blade face area of a typical Euro. It is just distributed differently. It is also used differently. The forward tilt/cant of the blade both reduces the turbulence and shifts it to one side. This decreases the wastes churning of the water and increases efficiency (you can do this to some extent with a euro to, it just not specifically designed for this like Greenland or Aleut paddles)
With fair technique you should have no less “propulsive force” with a properly sized GP - and it’s longer narrower distribution of surface area and canted blade technique takes care of the wasted water churn without adding a bunch of holes (which gets me back to the main topic).
Adding holes to a paddle blade may indeed reduce the large vortexes on either side of a blade - but only by ADDING many small vortexes created by the holes (visible in the image at that link) and reducing overall bite.
Whether the water spills off the sides of the blade and makes swirlies or goes through holes in it and make them there does not matter - it’s still wasted energy. The holes also reduce effective surface area/bite.
If the blade has too much bite for a given paddler’s power/drag ratio at a given speed, it would be a lot simpler (on several levels) to just use a smaller blade.
Most people don’t have this option so are limited to altering power and cadence only (or drilling holes I suppose). With GPs and Aleuts you can also just use less blade, whereas doing this with a euro is bad technique.
I have noted first hand how a narrower GP blade (so smaller overall) can be more efficient at a given speed (5mph) - while a slightly larger blade (just 1/4" wider - same length) feels harder at same speed because its churning more water. By feel I’d swear the wider (a long time favorite) was faster , but GPS and HRM tell the real story. More work does not always mean more speed. I got same speed with narrower blade, with noticeably less effort (the same better fit over distance the hole driller is looking for). As for cadence, the narrower is slightly more strokes per minute, but very slightly. The wider GP almost certainly has higher top speed and quicker sprints - but it takes power to do either.
My Aleut is narrower still - yet faster - and without the sprint and top end differences/limits. Really in a different league than GP and euro (though still similar to both - and wing - see my other crazy posts). So far seems even more efficient once you find what it wants to do - almost certainly due to the way it deals with this vortex/wasted churn energy issue (in two different ways depending on side used).
Trick is to balance four things:
- Paddle Bite (and leverage)
- Paddler’s power over time (strength/endurance)
- Drag (from all sources)
- Desired speed to be maintained
There are a LOT of ways to do this - for EACH paddler/situation.
Anyone really looking at this will instantly see the almost infinite variables and be vary wary of any claims of general efficiency increases for all paddlers in all situations based on some single feature/gizmo/etc.
People will point to the wing - which is generally accepted to be “faster” but this is largely dependent on technique - and I contend the technique the wing makes the paddler adopt (core power through rotation) is responsible for the bulk of it’s speed gain, with it’s single vortex/lift component a smaller secondary factor.
Some designs are certainly better than others, but which one is best depends on the individual paddler’s needs more than anything else.
Most people would rather buy stuff - or play with numbers - than get to know/develop their capabilities. The irony is that without a pretty good feel for your ability it’s hard to make the best make paddle choices. Luckily most paddle are designed around averages, and averages work well for average needs.
paddle blades
The vortex behind paddleblades is ventilation, air being drawn down the backface, not cavitation, which is gasses coming out of solution with water due to the creation of a significant vacuum. [We see cavitation with high speed propellers and bar blenders.]
Simple solution to ventilation is to drop the blade deeper in the water; use of a more vertical stroke or a longer shaft.
If the blade still wobbles under load:
- Shorten the stroke so it ends before water glops off the powerface.
- Use a dihedraled powerface to allow water to flow off the powerface more smoothly than it does off flat or cupped blades.
- Get a larger blade, understanding that the blade you overpower in a 500 meter sprint may still be large enough to do serious joint damage on a twenty mile day. [One can just back off a little.]
The best info on paddles is still found in John Winter’s "Shape of the Canoe, available in dick unline. His “gravel paddle” realloy worked in forward, while compromising sliced strokesw.
Greenland Paddle
– Last Updated: Feb-24-07 10:46 AM EST –
Thanks for that info. What you say about the Greenland paddle is ACTUALLY what I would have expected, because I know that super-long, skinny blades on canoe paddles have just as much bite, or grip on the water, as fat short blades, because the surface area is the same.
However, I have heard so many people on here refer to there being a need to pull faster during the stroke when using a Greenland paddle that I thought it was true. Several people have even likened it to dropping into a lower gear with a bicycle, suggesting that more paddle motion is needed for a given amount of boat movement, but now I think that must have been a really bad analogy, and that whatever it is that's going on with the Greenland paddle might best be explained in another way. Anyway, I see that you are claiming just the opposite - that any increas in cadence is minimal. Again, based on what I've found with canoe-paddle blades if differing shapes, that makes perfect sense. I guess I should be careful who I listen to on here. You do explain this kind of stuff in a way that actuyally makes sense a lot better than most.
As to the vorteces, I see what you mean - they are an indication of slippage, and reducing surface area by drilling holes will not reduce slippage.
Chinese
The Chinese have had diamond shaped holes in the rudders on their junks for centuries. They are more effective that way.
Vortex is not ventilation
Ventilation is air being entrained. An indication the technique needs work, as you indicated in the rest of your post. The votices also exist air free it clean catches.