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.
Rudders are different
Holes could reduce stalling and let teh rudder maintain grip at extreme angles.
…because of surface area!??..
NO, you’re incorrect. The density of deeper water is greater, thus…the face of the paddle blade has more resistance acting on it at depth…and the paddle is “working” with more leverage at more depth. Just for starters…
$.01
Okay, so why not…
– Last Updated: Feb-24-07 5:52 PM EST –
... just poke a dowel rod down there and paddle with that? You still need surface area. You are right that the deeper water provides greater resistance and bite but it's not due to higher density (simply dropping the water temperature from 70 degrees to 40 will increase the density hundreds of times more than you can get with an increase in depth which is many times the reach of your paddle, but even that increase in density is miniscule and you'd never feel it, so density is not the issue here. Remember that water is for all practical purposes non-compressible? That means you can't easily squeeze it into a smaller volume). Instead, the water a couple feet below the surface is more tightly confined by the weight above it and is less able to spill and swirl than water right at the surface which is has less confinement weight), but that doesn't mean you can do without having a similar surface area with which to get a grip on the water. I'm sure there's even more I'm leaving out, but since I was only commenting on what Grayak wrote, maybe take it up with him as well.
I’ll leave the intellegent answers
– Last Updated: Feb-24-07 9:20 PM EST –
to you intellegent sorts. I would only drill a hole in a paddle to stop a crack or split. Worries about resulting hydrodynamic innefficiencies would be remedied with duck tape or a band aid. The innuit or greenlanders would never even know. Or care. Golf ball type dimples in a paddle or hull could maybe reduce turbulence of a solid moving through liquid? Not my idea, I read it somewhere.
All wet on that one!
One of water’s odd/interesting qualities is that it is nearly incompressible.
This is why water fire extinguishers need air in them that can be compressed and then expand to push the water out. It’s why subs use air or other compressed gasses to “blow ballast”. A diver may need a phone booth worth of surface air to fill his lungs at depth - but a lung full of water at same depth is just a lung full at surface. A ball filled with air will compress with depth - and re-expand when surfaced - but a water filled ball will not. It stays the same.
PRESSURE changes with depth, but density changes VERY little . Temperature and salinity are the primary density variables.
The immediate surface layer - often down to several feet (sometimes hundreds) is most commonly a mixed layer without much difference in these values.
At least that’s what I recall from my oceanography classes, salinity and bathymetric readings I took in various parts of the Worlds oceans, anti-sub warfare stuff, etc.
Yup - keep it simple, skip the dimples
Dimples aren’t good either - for hull or paddles. Need different velocities and lower viscosities (water too dense - kayak too slow) fro that sort of fluid mechanics.
Good stroke techniques hardly move the paddle blades through the water at all. This is not intuitive to most - but I’ve looked at stop motion images of this, and now not it in my own paddling. Blade motion is mostly the up down of catch and release and the tilt of the lever action of the shaft. There is also the added small sideways motion of wing type strokes (and similar flying of canted blades) - that keep the the blade face moving into clean water and the single vortex* behind and slightly trailing. Blade is kept between high pressure on the face and lower pressure on the backside - which reduces slip/adds bite/creates a lift force forward (depending on how you like to look at it and what terminology you prefer).
-
- Note: vortex forms from pressure difference on either side of loaded blade - not speed of blade through water - (unless you’re tied to a dock and paddling in place!).
- Note: vortex forms from pressure difference on either side of loaded blade - not speed of blade through water - (unless you’re tied to a dock and paddling in place!).
tell me this, does more bite equal
more vortex?
doesnt bite come from the interplay between water and the outside edge of the paddle, e.g. bite is created when the paddle moves through the water right? a planted paddle generates no bite right.
if you measure the length of the edge of the blade many GPs have more edge than EPs and theoretically should have more bite…my layman’s view of bite is that it exists because moving water does not like to turn an edge, sine the GP usually has more edge (agreed the amount increases from the beginning to end of the stroke)it should have more bite than an EP…the EP gets more paddle face/edge in the water quicker than the GP, that’s why it has more power initially but I doubt it does by the end of the stroke…so GP users wanting more power should practice getting more of the blade completely in the bite zone quicker…
Now on drilling holes…reminds me of the paddle the principal used on my behind…more holes in a paddle blade should equal more bite right? since more edges for the water to have to curl around???
has anyone ever tried
With all the super materials we have available, has anyone ever made something like a hoop paddle? It would be a paddle with kind of like tennis racquet ends, but instead of strings, a very light, resilient, impermeable cloth or plastic. And it would form a very shallow spoon when it was being paddled. The hoop or edges would of course have to be much thinner than a tennis racquet. Only good for lakes/ocean, probably not tough enough for river use. Probably pretty light. Don’t they make a raquet like this for beach use, beach paddle ball?
Remeber rocket fins?
Jet fins and Rocket fins sold a bunch of fins to scuba divers with this smae concept. They were designed with vents in the power face to allow some water to flow through the fin.
While I am not prepaared to drill holes in any of my paddles just yet (even the failry small 25mm ones discusssed here), I am interested in seeing more data.
More bite = less slip
Better traction. Not really an edge thing that I see (if I understand you). More about simple drag, and some manipulation of the low pressure area though shape and technique.
Edge and attack angle can be looked at for vortex size/shape to - but since different shapes can have the same area it may be more interesting to look edges as they relate to catch/release and other paddle handling qualities.
As I said elsewhere, paddles pull through the water a LOT less than people think. Acts more as a lever once you are moving, and more so as speed increases. Longer narrower blades probably do allow more control of the lever action.
Technically less slip is better, but real world some slip prevents us from overworking engine or blowing a transmission. Mixed mode. Blades have to work over a range of slipping, levering, and all other sorts of motions in control strokes. All paddle designs are compromises - by necessity. Wing gives up some generality to get more bite, etc.
Have to match/balance things. Most paddlers just back off - altering power and cadence to handle the extra bite they might want for sprints. The other option is to adjust paddle size and maintain form/cadence that results in best aerobic output for a given paddlers power and endurance over distance, using cadence/power changes to sprint.
Being variable ourselves, most just adapt to and use what’s available, popular, standard, etc. Works well enough. Still sort of funny how much folks will obsess about hull design/speed in comparison.
When looking to alter/adapt/innovate - it would help to start with the major variables - and decide on priority/focus - rather than just going after some generic improvement from holes, dimples, etc.