Why bicycles have gears (paddles & technique)^

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JulesT
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Why bicycles have gears (paddles & technique)^

Post by JulesT » Tue Apr 18, 2006 9:45 pm

Cyclists know that when you reach an uphill gradient you change down a gear. You might make it up the hill in a high ratio but you’ll get more tired. So the right gearing allows the human body to work at its optimum.

The same must be true for paddling, the equivalent of a hill being a headwind. I’m in my second season of sea kayaking and experienced a long hard slog against a headwind of between bf 4 and 5 that had developed between me and the end of my journey on Windermere on Easter monday. My paddle is great in normal conditions; (its an Epic Active touring) but on this stretch I really could have done with changing down a gear.

So I’m interested to hear peoples input on the best way to ‘change down a gear’. An initial thought is that a shorter paddle might do the trick. The marketplace shows paddles smaller in area rather than length, going down in area to the Greenland paddle; but then they are longer - confusing ! I guess the greenland paddles maybe slip through the water - less resistance but perhaps less efficiency. On the other hand one could do short strokes. One way or another it seems that the human body / regular paddle is working well in normal conditions but not so against a strong headwind.

So any thoughts or input from you more experienced paddlers out there ?

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Post by RichardCree » Tue Apr 18, 2006 10:13 pm

Hi Jules, in order to step down a gear look at technique rather than at a differant padle.

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Post by Dave Thomas » Tue Apr 18, 2006 11:40 pm

I paddle with Lendal Nordkapp blades (ie quite large). My philosophy is that the aim of efficient paddling is to minimise slip of the blade through the water - the old 'imagine you're pulling the boat past a fixed post' coaching idea put into practice. So it follows that the stroke rate has to be matched to the speed of the boat through the water, so as to minimise the 'slippage' of the blade through the water. A head wind gives more resistance and tends to slow you down. The knack is to find a lower stroke rate which matches the new slower speed of the boat through the water, and put in just enough extra effort to maintain that new balance of boat speed and stroke rate. combination.

Hope that makes sense - after a couple of pints! Anyone care to add (or subtract!) anything!!

Dave Thomas

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Post by CaileanMac » Wed Apr 19, 2006 1:34 am

JulesT,

Do I correctly understand you as wanting more power to the pedal, grunt from stroke i.e. to maintain speed / progress against headwind?

If so you need to work on your technique rather than throw your Epic in the dustbin for a shorter paddle. Work on pre rotation aspect of trunk rotation and pausing paddle at the point which it's furtherest away from your body just before it enters the water (ensures you don't chop off several cm's from your stroke and that pre-rotation has actually occurred). As for pre-rotation it's case of applying gentle pressure on one footrest whilst twisting shoulder blades to let the paddle blade escape as far forwards as possible.

It's late and this is something which isn't going to be done justice through words on an online forum I'm afraid. Recommend getting some coaching in a club or commerical setting - human's learn from actually doing and practising skills in context. Some good coaching simply ensures the techniques are learnt and applied correctly first time, rather than developing bad habits and taking a far greater time for same learning to occur through trial & error (aka pain & tiredness) ;-)

Hope this is of some use?

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Post by active4seasons » Wed Apr 19, 2006 9:06 am

Jules,

Interesting point about different paddles. Obviously the different styles of paddles available require slightly different techniques but as has been mentioned it is less common in sea kayaking to reach for a different blade. I do a fair bit of open canoeing and have a couple of paddles to chose from depending on conditions. I don't see why this could not apply to sea kayaking in that both your blades could be split and be fitted with different blade types and a different shaft length.

Certainly when it comes to winds my big Lendal nordkapp blade is my prefered shape in low winds but I would prefer something like the relaxed touring blade of the epic for higher winds with a shorter shaft to allow a faster rate of paddle and less chance of the wind catching the dry end.

Would also give the slit paddle gadget holders a chance to use thier bits of pipe when swapping the paddle over.

Why not try both methods. Get a bit of advice regarding paddling stroke with currrent paddle and also go for the two paddle approach - see which suits you best.

Ollie

p.s. Taking cover in case of flack from comment on gadgets incoming.
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JulesT
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Post by JulesT » Wed Apr 19, 2006 12:48 pm

Thanks everyone for your input but just to clarify:

In the bicycle scenario the human engine works nicely in a rev range of about 80 to 90 rpm. ie if you try to pull too high a gear ratio on the bike you rev slower and press harder but the net effect is that your muscles dont work as well as if they are going slightly faster but pressing less. Too fast and too light a pressure and you also lose efficiency. So the analogy transfers to stroke rate in paddling but thats where its not so easy to vary your distance over the ground (water) per stroke. Hope you get what I'm trying to say here!

So the objective is not necessarily an attempt to maintain speed but to make headway against a headwind in the most efficient way, ie without tiring yourself out by keeping the cadence (stroke rate) matched to optimum muscle performance.

I guess a high stroke style with the paddle close by the side of the boat could be considered a 'low gear' as opposed to reaching out as far as possible away from the boat with a long paddle (exaggerating imagine a 20 foot paddle) would casue a much longer fetch and constitute a 'high gear'.

But I'm interested to hear peoples experience on the greenland paddle which I guess must 'slip' through the water due to its narrow cross section ?

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Paddle Efficiency

Post by Mike Marshall » Wed Apr 19, 2006 1:03 pm

Bike gears involve chain lengths, I cant see how a paddler can achieve that without some risk of injury (altering paddle stroke etc) other than smaller blade areas.
I find the smaller area blades useful in stronger winds.
Nice touch I saw last Sunday was a spare pair of Lendal Norkapps trimmed to replicate the surface area and shape of the Kinetic style blades.
Significant reduction in surface area over the Nordkapp and effectively lower gearing.
When really windy use the spares, which can also be useful for long days if you have large paddle blades. Use the spares towards the end of the day to reduce stress when you are tired, just as you would use lower gears on a bike. Its always better to "spin to win."(Lance Armstrong!!!)

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Post by ianzippy » Wed Apr 19, 2006 1:47 pm

Re; Greenland paddles, although i have limited experience with them, i don't think slipping through the water rather than providing drive is too much of an issue. The 'slip' factor comes into play a bit when starting from a standstill, especially with a loaded boat, but once moving - no problems. Greenland paddles allow a continuously variable gear depending on how much of the blade area you submerge, so for high gear, use a high paddle angle, and submerge as much as you like, even use a sliding stroke if neccessary (have a look at http://www.qajaqusa.org/common_images/g ... stroke.mpg).
For a low gear, low paddle angle = less blade submerged.
If i've understood what you're asking correctly, there are parallels with the voyageurs in birch bark canoes (stick with me here...). Rough surface of boat, plus size and loaded weight = lots of drag and inertia to be overcome - therefore they used a high stroke rate, and relatively small blade area to maintain momentum, which is what you want into a headwind (keeping momentum up), therefore, I reckon a small blade area, plus high stroke rate = more efficient.

Sure there will be some disagreement with that little lot!
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Post by Dave Thomas » Wed Apr 19, 2006 4:18 pm

I can accept that there is a 'natural' body rhythm which gives optimum 'efficiency' of muscle activity. However, any stroke/paddle combination which causes the paddle to slip back through the water more is going to waste more of that energy - however efficiently it is produced by the body. Reducing blade size and increasing stroke rate (or at any rate the speed at which the blade is pulled back through the water) might protect the body from shock loading and over-straining - and it might well also give the best outcome overall, in terms of ability to actually cover the distance in adverse conditions with as little exhaustion as possible (after all, the Inuit survived pretty well with such a technique, as mentioned above) but it is more akin to slipping the clutch to keep engine revs up in a car than to changing gear. I still on balance regard the gearing effect primarily as matching stroke rate/blade speed to boat speed through the water.

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Re: Why bicycles have gears (paddles & technique)

Post by Jim » Sat Apr 22, 2006 3:54 pm

JulesT wrote:So I’m interested to hear peoples input on the best way to ‘change down a gear’. An initial thought is that a shorter paddle might do the trick. The marketplace shows paddles smaller in area rather than length, going down in area to the Greenland paddle; but then they are longer - confusing !
The thing about paddling in a headwind, or any strong wind, is what the wind and paddle are doing. Yes there is more resistance on the boat but I'm not sure that your thoughts on gearing are quite right. When paddling into a headwind you have to punch the upper blade into the wind, whilst pulling the other through the water. Wind speed increases as you gain height, the wind speed is many times that of the water speed anyway, the upper blade becomes a significant handicap the higher angle you paddle at. Thus the easy solution is to use a longer paddle at a lower angle. Modern sea kayakers are often river runners and/or day trippers who are used to high paddle angles and/or only choosing calm conditions hence the current shortening of shaft lengths. Some people did use excessive shafts in the old days but from what I read many are now going the opposite way, which is great for paddling in calm conditions.

There are other issues such as feather, blade size and blade shape. Again these have followed fashion over recent years, although the original thinking was not right and greenland designs are often without feather at all so it's hard to know what the optimum angle would be (consider that the blade prescribes an arc so the angle of least drag changes throughout the stroke). It is my reckoning that greenland paddles are more efficient in the air since they have a much higher aspect ratio than say a Nordkapp, and thus rely on feather less. The fact that that type of paddle has evolved over thousands of years including rougher conditions that we normally bother to kayak in, should provide a hint that it must work.

So there you have, I reckon (and I am no authority) that you should experiment with long thin blades on long shafts at different feather angles - a set of splits with a variable angle/length joint would be ideal for that!

JIM

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Isokinetic?

Post by Chris Bolton » Tue Apr 25, 2006 10:01 pm

My take on Jules's question is that with a bike, the force required is independant of how fast you paddle. I know gears make a difference, and wind resistance increases with speed, but bear with me. The bike pedals, chain, gears and wheels are effectively a lever; you put a certain force on the pedal, and the ratios involved put a proportionate force on the road.

With a paddle, the force depends on how hard you pull it through the water. The technical term for this is isokinetic. This is what is important in the design of paddling machines; if you just connect a paddle up to a set of weights it won't behave like a paddle in water.

So if you want to "change down a gear", just don't pull so hard. I use Nordkapp blades, and if I really want to push the pace, I pull hard (and the stroke rate goes up). If I want to cruise, or it's a long slog against the wind, I pull less hard (and the stroke rate goes down). I like the big blade as I can choose how hard to pull; a small blade gives me less choice.

The apparent contradiction is that the stroke rate changes in a different way to the cadence on a bike.

It's different for racing, when it's important to choose the blade size to optimise your stroke rate; that's because in a race, you're going to paddle hard all the time, and seconds count. On a sea trip, efficiency is how far you can paddle at a reasonable pace, not how much absolute speed you can get.

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Re: Isokinetic?

Post by Dave Thomas » Tue Apr 25, 2006 11:30 pm

Chris Bolton wrote:So if you want to "change down a gear", just don't pull so hard. I use Nordkapp blades, and if I really want to push the pace, I pull hard (and the stroke rate goes up). If I want to cruise, or it's a long slog against the wind, I pull less hard (and the stroke rate goes down). I like the big blade as I can choose how hard to pull; a small blade gives me less choice.
Just back from the pub (again!!) - but I think this paraphrases at least part of what I was saying a few days ago!

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Agreed

Post by Chris Bolton » Tue Apr 25, 2006 11:45 pm

Dave Thomas wrote:I think this paraphrases at least part of what I was saying a few days ago!
And on re-reading, I think you're right, Dave. I agree with your logic; I hope I've added a view on why it works.

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Post by Bertie.. » Wed Apr 26, 2006 12:34 pm

this thread has been bugging me for a while, and I've finally realised what it is. I don't like the use of a bike with gears as an analogy to paddling.

For me, if we're going to equate it to cycling it's akin to cycling on a bike with no gears, there are only three things we can improve: technique; strength; stamina.

On a bike with no gears, could SPD peddles allow the cyclist to use more of strength by pulling up on the peddle at the rear - to me this equates to proper forward paddling technique using the whole of the body, e.g. trunk rotation, good use of leg cycling, correct placement of paddle etc.

On a bike with no gears, I can increase the distance I can peddle by regularly training - no difference in paddling, the more you do, the more stamina will develop.

On a bike with no gears, I can increase the distance I can climb up a hill, or sprint, by working on the strength in my legs etc - in paddling I can do the same.

So for me, the ability of a good sea kayaker to 'change gear' relies on them having good technique, strength & stamina to allow them to put the 'pedal to the metal' - remember we're not looking to change down gears, we're looking to open the throttle!

For me, using a smaller blade is akin to choosing to allow the bike chain to slip (if that was possible). Whilst smaller blades often means less weight & less air resistance on the out-of-water arc, in the water it means the paddle is less likely to grip the water, meaning you'll be less efficient. (assuming design of blade isn't an issue)

So, in terms of a paddle, I look for a combination of 'grip' in the water & weight/air resistance out of the water. I would suspect that this will change depending on you physical dimensions, strength etc.

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Post by mharrall » Wed Apr 26, 2006 12:43 pm

Lendal do a shaft extension widget. You could perhaps modify your paddle so that you have two available lengths to choose from. On days when conditions warrant it, you could remove the extension peice and use the short paddle, giving you a "lower gear".
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Post by Fast Pat » Wed Apr 26, 2006 1:02 pm

The "widget" is only available in 20 or 30 cms too much for most folk!

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Post by Rory W » Wed Apr 26, 2006 3:18 pm

I could be wrong and I probably am, but I had always assumed that the main reason for wanting a higher stroke rate was to maintain momentum, rather than anything to do with the human engine. Surely it is more efficient for the boat to be continually moving than for it to accelerate a lot with each stroke and then slow down again between strokes. Of course this needs to be balanced with the amount of energy that is wasted through the paddle slipping in the water. This is just through personal experience, I have no idea about the science behind it. When you start paddling from a stand still, the first few strokes are a lot harder than when you're moving. Hopefully someone will come along soon and explain why I'm wrong.
Chris Bolton wrote:So if you want to "change down a gear", just don't pull so hard. I use Nordkapp blades, and if I really want to push the pace, I pull hard (and the stroke rate goes up). If I want to cruise, or it's a long slog against the wind, I pull less hard (and the stroke rate goes down). I like the big blade as I can choose how hard to pull; a small blade gives me less choice.
When you wanted to "change down a gear", would you not be paddling faster for the same effort output if you changed to smaller or shorter paddles and kept the stroke rate up? All you are doing by pulling less hard with bigger paddles is slowing down and having a bit of a rest. The question is whether it is really practical or worthwhile to bother with the extra paddles. If they are your splits do you want to be stuck with a very small set of paddles blades if you lose your big ones?

Another question, are pulling hard and paddling fast (by this I mean turning over fast rather than boat speed) always the same thing? I have very little experience of sea paddling, but in my race boat (using the same paddle all the time), I could increase my stroke rate independently of how hard I was pushing by shortening the length of my stroke by taking it out earlier or by letting the blade slip through the water rather than catching properly (not that I would do this in a race). Could this be applied to paddling into a headwind?

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Post by active4seasons » Wed Apr 26, 2006 9:18 pm

There are some interesting points of view here - too many to read through properly.
I know what you are saying Bertie but individuals have a prefered cadence on a bike or in a kayak. When you are trying to paddle against a very strong wind Force 5-6 you need to try and reduce the amount of time a blade is out of the water so as to reduce your boat slipping backwards. Paddling faster will not necessarily acheive this. The point is to maintain your desired cadence your fitness, paddle type and conditions will all have an effect. Will having asn alternative to your blede give you a better chance of performing better. Perhaps we should look to the marathon boys to see if they alter their blades depending on prevaling conditions?
Sorry for any spelling or typos - need to get off the computer before my wife throttles me!
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More thoughts

Post by Chris Bolton » Wed Apr 26, 2006 10:40 pm

All very interesting. I'm not pretending to fully understand the topic, but I think it's a lot more complex than a bike. I think the hydrodynamics of the paddle probably matters more than the biomechanics of the paddler - on a bike, there's just the biomechanics. There are other complications; as Ollie says, against a headwind you don't want to let the boat blow backwards, so long strokes and quick recovery helps.

If efficiency means not letting the paddle slip in the water, a long slow paddle stroke should help; the lower the force on the paddle, the less it should try to slip? A deeply submerged blade can also help avoid slip if you're pulling hard. As Rory says, the first few strokes from stationary are hard, which I think is a combination of the isokinetic effect and the need to accelerate the mass of the boat. When I raced dragon boats, it was easy to get cavitation (a vacuum bubble behind the blade) on the first stroke, unless you put the blade really deep.

Raising the stroke rate by shortening it is probably counter productive. It's not the same as speeding up the paddle in the water. Not putting it fully in the water must also be inefficient, as it allows it to slip.

Chris

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Post by Bertie.. » Thu Apr 27, 2006 8:44 am

I remember reading in David Birch's 'Fundamentals of Sea Kayak Navigation' that a headwind has less of an affect on forward paddling speeds than I believed, and having conducted a few non-scientific experiments on various groups I've worked with - there seems to be some truth in this.

From what I've seen people often knuckle down when faced with a head wind in the belief that it has a bigger impact on their forward progress than it actually does. This results in the individual/group working harder, and actually travelling faster than anticipated - leading to comments like 'that wasn't as strong as I thought it was'. The problem with this is that the paddler tires themselves out quicker.

None of this is based on any real evidence, other than taking some small groups who know their flatwater paddling speed, paddling a known distance into a headwind, then comparing actual time taken against expected time. But it's enough to make me think there is something in it.

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Post by JulesT » Thu Apr 27, 2006 6:19 pm

Lots of interesting viewpoints here ! A few comments:

First of all I feel that the bike analogy is a good one, its nothing to do with the fact its a bicycle its all about the most efficient use of human muscles. ie to get the most work (/minimum tiredness / maximum efficiency etc) out of a given human the muscles need to work at an optimum rate - combination of force and speed.

Next the point about technique has to be right, and that probably comes down to using the right muscle groups in the optimum combination and range of movement. And fitness, and perhaps deliberately putting more effort in against a headwind than normal cruising.

Next is energy wasted by a blade slipping through the water ? I'm not sure about that one but I guess there has to be some wastage since the paddle produces mini-whirlpools/eddies. But this could be one factor that does in fact provide a lower 'gear ratio'.

A long paddle with a low paddling style where the blade enters the water at some distance away from the side of the kayak must provide a higher 'gear ratio' than entering the paddle right alongside the kayak as in the high paddling style (exaggerate and think of a rowing skiff where the blade entry points are approx 20' apart with each stroke)

On the Greenland paddle I'll dare to venture a theory that with the materials to hand they couldnt have built reliable and robust paddles of the modern style where a big relatively flat bit is stuck on the end of a long thin bit - after all their kayak construction technique has in general given way to modern composite and poly construction.

But the long thin paddle does seem to offer more variation in depth of paddle entry etc and slippage through the water etc. Why they didnt bother with the feathering bit ? maybe its not worth it with that shape of paddle.

Thanks for everyones input, will be experimenting - can anyone recommend sources to buy a greenland paddle to try - splits preferrable (and possibly featherable or is that a nono for the greenland technique)
?

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Post by andreadawn » Thu Apr 27, 2006 6:53 pm

Have just bought a two piece Greenland paddle from Windslicer, but it only arrived yesterday so haven't had a chance to play with it yet. Not cheap, but a real work of art. Feathercraft also make a split GP available through Knoydart but again not cheap.

Andrea.

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Post by JulesT » Thu Apr 27, 2006 7:40 pm

Andrea - thanks for this link which has an excellent description of the greenland paddle - still digesting it - perhaps they are biased because they're selling them but its making some sense

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Post by Jim » Thu Apr 27, 2006 11:04 pm

This is a difficult thread to digest but here is my engineering view of it.

The closest analogy is with singlespeed bikes. They have one gear and you are in it all the time. When paddling you have one gear and you are in it all the time. To change gears with a singlespeed, you have to buy a new sprocket or chainring, dismantle the bike and replace the existing one with it. To change gears in a boat you have to buy a different size paddle, dismantle the one you have been using (or put it in the garage) and use the new one instead.

I think we need to understand better why bikes have gears.

You go faster for a given power input in a higher gear. When rolling on the flat and only overcoming friction in the bearings and the air resistance you will reach a comfortable cadence (closely related to power output) in a fairly high gear, your input overcomes the resistances and you continue at constant velocity. Add a hill into the equation and you are now working against gravity as well, and gravity is quite a significant force. Now, if you stay in the same gear you will need to put in much more power to maintain your speed, but your body physically can't provide the extra, or if it can your knees can't transmit it safely. So you change down a gear thus enabling you to put in the same power but travel at a reduced velocity, If the gradient was constant you would soon reach a constant velocity again where your input is equal to the resistance. Of course gradients are rarely constant and momentum masks the lag so unless you get into a long climb you might not be able to relate this to experience.

A gear train is basically a lever, the lower the gear, the more mechanical advantage you get.

Now with paddling things get more complicated. To get more mechanical advantage you use a longer lever, or a longer paddle shaft. This however leads to a lower paddling angle which may not be as efficient as a high angle (if it requires more energy for each stroke for example, but I'm not sure that it does), also the lever thing is important because the further your blade is from the boat, the more yawing moment it applies to the boat, so you can waste more energy in yawing.
Where the blade area/efficiency comes in is even less intuitive. A larger blade catches more water, the force on it is directly related to how much water it catches. This force however, does not resist your motion, but creates it. What the bigger blade allows you to do is exert more force into the system before the blade will "slip" through the water. In practice all blades slip and the shape can be as important factor as the area. So an easy to paddle blade shape/size is more of a safety valve than a gear, it simply prevents you from stressing your system as much as a bigger or more aggressive blade shape. Assuming neither blade slips, it doesn't actually matter whether you have a big or a small blade for a given power exertion, you will provide exactly the same propulsive force to the kayak. If you paddle at a power input where each blade is just about to slip, you will be able to put more power in to the bigger blade, which means you will go faster, but also tire more quickly. The thing is that laden sea kayaks have considerable momentum and inertia, it takes a lot of force to get them moving at speed but oncethey are it is relatively easy to keep them going. A bigger blade will allow you to put much more power in early on providing fast acceleration to your cruising speed, whilst a small blade will take longer to reach it, requiring the same energy overall but not forcing it through your muscles so quickly. This is different to the gear scenario where you can keep putting more power in until something breaks but to cruise in a lower gear requires a much higher cadence (power) - in paddling the cruising should require the same power.

So back to levers again - long = easier but slower, short = harder but faster. High angle paddling is much better for racing and sprinting and stuff because you can accelerate much faster but you get less mechanical advantage from the paddle. It seems that everyone thinks that the high angle technique typically uses better trunk rotation and more powerful muscle groups than the low angle, but I'm not so sure since the low angle approach requires a much bigger body swing, or trunk rotation. It would take a proper ergonomist with a scientific study to decide that one for sure (may already have been done) but the important point is that what is good for racing (relatively short bursts at max power or above) is not necessarily good for cruising (extended activity at lower exertion).

Now to get back to paddling in wind.

Wind is an extra resistance, like the hill. To successfully paddle into the wind without knackering yourself it would be good to change down a gear, which means using a longer shaft for more mechanical advantage. It also suggests a low angle stroke (even with shorter paddles) to keep the blades in the slower air, which is in turn a slower stroke than a high angle one. The temptation in strong wind is to try and keep your speed up, which results in putting much more power into the system, with a large blade you may just succeed but overstress your muscles, with a smaller blade you should find the "safety valve" or maximum power limit before you hurt yourself. The thing is though, that if you were able to maintain the exact same power input in and out of wind, you would simply find that the resisting forces slow you down, in fact the wind can make up such a big contribution to resistance that you may well find you need to paddle harder just to keep moving because even without boat resistance the wind needs more power. This would be where a longer paddle would come in useful, also it would be where a smaller blade might end up slipping before the wind forces are resisted (you'll be going nowhere if this is the case but shouldn't wreck your shoulders trying).

Personally I like smaller blades on a relatively long shaft by modern standards (not old school length though) - the type I use have a nice springy carbon shaft which means I can get enough acceleration without damaging myself if I really want it, but most of the time I will just strokethe boat along gradually building speed and then maintaining it with minimal effort (except when weathercocking). It also means that I can get a very swinging low rhythm going that works well in wind, and the smaller blades catch less in the wind, which is good because it's so light it could get ripped out of my hands really easily by a gust (in fact it has, which is why I wear a leash, with bigger blades it would be worse still).

I wonder if we will start to see regional variations in paddle length around the UK depending on how windy each region is?

Oh yeah, and wind seriously affects what gear bikes need to be in as well - considerable added resistance!

JIM

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Post by Rory W » Fri Apr 28, 2006 1:28 am

Thanks that makes far more sense now, there were some rather large chunks missing out of my reasoning.

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Post by jurgenk » Fri Apr 28, 2006 2:03 am

Thank you for that Jim... I think my brain is full now. This has been an interesting thread and makes me want to try to make a Greenland-style paddle once my brain cools sufficiently.
Restlessness and discontent are the first neccessities of progress. Thomas Edison

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Post by active4seasons » Fri Apr 28, 2006 9:44 pm

Jim,

I am afraid there are holes in your reasoning - quite a few and it sounds like you should get yourself down here for a paddle sometime. No excuse about having to fix your boat - I have as demo boat to try.

Not sure where to start? The analogy of a single gear bike is no good as a human paddling a boat is able to alter many variables. For example when I need to accelerate to get on a wave I slide my hands closer together and bring the paddle closer to the side of the boat but also reduce the area of paddle I place in the water. These three things increase my speed of rotation but lessen the force applied to the blade and my body. As the boat speed increases I am able to alter all three variables which is unlike the single gear bike you talk about!

I place the blade wider and deeper and reduce the cadence - bingo! I reduce the energy output due to the momentum I have created allowing me to maintain pressure on the blade and therefore the boat speed is maintained and my energy systems are allowed to catch up as it were - moving from anaerobic to aerobic metabolism.

What a great activety we have - where else can you pit yourself mind and body, against nature and get such a reward. I will be paddling the beautiful NE coast testing two demo boats waiting for my wife to ring telling me to get the garden done or some other chore.

Ollie
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Post by Chris Bolton » Fri Apr 28, 2006 10:38 pm

I agree with Ollie - his comments reflect what I was trying to say about the isokinetic resistance of paddles. The harder you pull, the more force you get, and as the boat speeds up the force drops off automatically.

I'm not sure that I agree about putting less of the blade in the water; that's like slipping the clutch on a car. You only have to slip the clutch to avoid stalling the engine, but the human body can pull hard even with no motion.

Chris

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Post by Rory W » Fri Apr 28, 2006 11:12 pm

Hm I'd just managed to convince myself I vaguely understood it. Never mind I give up.

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Jim
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Post by Jim » Sat Apr 29, 2006 12:48 am

active4seasons wrote:Jim,

I am afraid there are holes in your reasoning - quite a few and it sounds like you should get yourself down here for a paddle sometime. No excuse about having to fix your boat - I have as demo boat to try.
Like I said, I'm an Engineer not an Ergonomist!

However you have unwittingly agreed with me, the only way you can actually change gear is to change the lever, all the other things you mention are tinkering with the way the engine runs or the grippiness of the tyres (moving more into a motoring analogy).

Altering the throttle, choke or mixture on your car doesn't change the gearing, nor does changing the tyre compound or tread pattern, camber, toe etc. but they all affect the way it performs overall. I think people are getting too caught up with the concept of changing the mechanics of the paddle, when in fact no 2 of us use the tool in the exact same way with the exact same results. I was hoping an engineering perspective hinting at the further human complexities might put people off :-)

JIM

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