Paddler Weight & Ski Weight Ratio and Speed

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10 years 5 months ago #9059 by Boef
Not buying into this technical blurb. Paddle more, get better at it, you'll be faster.

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10 years 5 months ago #9069 by AGA
I appreciate the paddling encouragement Boef and agree that however much extra can come out of the ski weight change, probably more can come from both the paddler fitness and technique.

Nevertheless for those who like the stats, I checked out Wesley Echols growing set of speed stats, which include some comparisons of speed on the same ski model but with lighter/heavier construction.

Assuming Wesley is about 80kg, for a 2-3% improvement in the load factor (which was a 2-3kg cut in ski weight)he gives an improved speed rating of 6 (from 5.8) on an SES and a 5.95 (from 5.55) on a V10L. If his speed ratings are proportionate to speed (they may not be) this would equate to a 3%-7% improvement in speed.

It was also worth noting he achieved a negligible speed improvement when ski weight was cut a further 1kg.

It is suggesting that getting the paddler weight relative to the load weight (paddler plus ski) up to a reasonable ratio makes quite a big difference, but that once the paddler strength is pushing the ski efficiently, further weight savings have limited impact.

I'm going to try and get some practical data on this over the next week or so. I've been able to paddle 3-5 times per week over the past month and have logged speed across a range of conditions (0-25 knots, flat and swells) on the glass V10. I've got access to a much lighter ski next week and will run the same courses on the lower weight ski.

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10 years 5 months ago #9070 by Rightarmbad
The noise factor will be too high.
You need to have both skis on the same day side by side.

Maybe Wes found no increase in speed as the boat was extremely light due to finding the twitchyness a problem?
Or he simply run into the resolution limits of his testing.

Wasn't most of his comparison paddles on flatter water?

I think the lighter one would find it's home in the waves.

I believe you will find there is no mathematical component to his ratings, just subjective ones.
Hopefully he will post up and tell us what he has found.

Follow the path of the independent thinker. Expose your ideas to the dangers of controversy. Speak your mind and fear less the label of 'crackpot' than the stigma of conformity. And on issues that are important to you, stand up and be counted at any cost.--- Thomas J. Watson

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10 years 5 months ago #9079 by AGA
Took the testing on the heavier ski down a new angle last evening.

Loaded up the car with all the gear and travelled several hundred metres down the road before I realised I had failed to tie the ski on.

I can report that the 18kg ski performs excellently at the speeds I was working with, roughly 30-50kmh, staying relatively grounded but showing good aerodynamic characteristics. Conditions were benign with a 3-5 knot cross wind and a few potholes.

I can't say for certain how my bodyweight impacted on the results but can see how a heavier paddler may have kept the car more stable over the speed humps.

RAB, I know you're a stickler for controlled conditions, so I must acknowledge that there was a bit of scientific noise on this exercise, and reckon that the integrity of the test could be improved by forgetting to tie on both the heavier and lighter skis at the same time.
The following user(s) said Thank You: Moll

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10 years 5 months ago #9083 by wesley
this is a great question that I have been asked many times. Below is what i base my opinion on. My extensive data base since 2005 when I started paddling skis(xt) is considerable.

One of my GPS time trial courses is a 1.62-1.64 mile course depending on my line. I have done this course 112 time and the total is almost 40 hrs. Sometime I do it out and back depending.

My other tt courses is a 6.4 mile course that includes the above course. This course I have done 240 times with a total time of almost 241 hours.

My other TT course is a 11.5 mile course that I have done 82 times for a total of almost 140 hours. This 3 tt courses start at my beach(check my race "Sakonnet River Race" for a GPS route and continue up the river.

This River is 2-4 mile wide leading to the ocean and is 11 miles in lenght one way. It is like a small bay almost that connects Mt Hope Bay to the ocean by way of this channel(Sakonnet River). Conditions are range from flat to 2ft seas and can be much bigger as the River empties into the ocean(4miles wide) with a 3-4 ft tides. My point is this is not flatwater paddling, not Surfski champ conditions, but an ideal place to tt skis and report on how they perform.

My other TT course is a 6 mile course "up the Sakonnet that I have done 129 times for a total of 126 hours.

So 4 TT course with a total of 547 hours and 3300 miles. This is just the 4TT data and does not include my races or my many, many hours of paddling not on these courses.

So based on all the paddling, with various brands/models and models of different layups(weights) here is what I have concluded. I use the SES as the example because I have owned/paddled the 21/22lb Ultra, 24-27lb Excel(i had one layed up at 27lbs vice 24-25lbs, 30lb advantage. I have owned others brands with different layups but I have much more data on the SES since I have paddled them for 2years now.

1. My general rule of thumb has been that if there is difference of 4 lbs in boat weight between the weights of 22lbs and 32lbs. this generally equates to 10 seconds per mile difference.This is what someone else said on this thread 4-6% difference over a 10k, provided stabilty is not an issue. For example there is not marginal difference between my 22lbs SES and my 24lb SES, but between my 22lb SES and my 26/27lb SES, 4-5lb difference is very noticable in racing and often is the difference in the race standings. I have paddled with the same group of paddlers for years now in races and the difference generally as 1-4 minutes in races of 1 hours to 3 hours. So if you are racing boat weights counts even at my midpack racer level.
2. A boat that weighs 27/28 lbs is the best overall weight if you can only have one boat, paddle in all conditions, and durability is a concern.This weight of ski is light enough for racing, durable for everyday use, and stable enough for bigger conditions. This is a general rule of thumb. I know many of us have lighter skis that we use every day, etc.
3. If you are a hard core racer or just want to beat your buddies, paddle the lightest ski you can afford while maintaining your paddling techique without sliding back in big conditons. We all know lighter skis get pushed around, are less stable, especially pronounced with lighter and mid weight paddlers. For example in bigger conditions I do significantly better in my 27lb SES vice my 22lb SES. This is even more pronounced in a longer race over 2 hours where boat fatigue in rough conditions comes into play. My stability and hence my paddling techique suffer in my 22lb SES compared to my 27lb one. while I can paddle both and stay upright, I am slower in a lighter ski due due the difference in stability in rough conditions. Flat to moderate conditions I go with the 22-24lb ski.
4. Unless cost is a major concern, any ski over 32lbs is too heavy to train in on a regular basis. I have had atleast 5-7 skis that weigh 32-38 lbs and that is alot of boat to push unless you always paddle downwind and never load it on a car. Remember I am 51 now. I use to load 55lbs kayaks and race those.
5. As a long time runner, I know extra weight is a killer. I forget the exact calculation but just an extra 10lbs in body weight can cause you to be 20 minutes slower in a marathon all things being equal. Chris(surfskiracing.com web master) causally pointed out to me last year, it is the slim guys that are winning the races. I was the exception being 12lbs over what my optimum weight should be for a 51 year old and it is not muscle!!
6. So my goal is to lose the 12lbs before next season and that alone should give my another 10 seconds per mile over last years racing times. That is what i am hoping for.
7. Oh, rudders as most of us know make a huge difference in speed, stability, and and handling. So use the smallest rudder you can get away with for the conditions you are paddling in. The difference can be as much as 10 seconds per mile. When comparing skis, you must use the same length rudder to be fair.

Hope this helps. Remember this is my experience, it may not be yours.

Wesley Echols
SurfskiRacing.com
#1 in Surfski Reviews.

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10 years 5 months ago #9145 by AGA2
Thanks for the comments and insight Wesley. There aren’t many who’ve had the chance to directly test across such a range of skis.

Here are a few very preliminary thoughts coming from my trial of the lighter and heavier ski weights.

I’ve undertaken a number of runs on the lighter ski. Unfortunately I didn’t view 2 of the runs as completely clean (got caught in a skiff race in one and the wind had a lot of variability in the other), so need to do some more work to be comfortable that I’m getting adequate comparisons of the skis in like for like conditions.

The data from the trials where the wind conditions were sufficiently consistent for comparison is pretty interesting.

Some thoughts so far:
A. The lighter ski has been faster on each occasion in aggregate than the heavier ski, notwithstanding any caution on my part having never paddled the lighter ski before, and the other minor disruptions (ie encountering skiff race and a strong gusty headwind).

B. I have been able to get a speed improvement on the lighter ski that is significantly higher than the proportionate improvement in the load factor (7%) – but only over limited time periods.

C. I achieved better speed improvements at the start of each trial than the end.

D. If I put the lighter ski on my car and forgot to tie it on I'm sure I'd lose it before I reached 40kmh.

See the following graph which shows the speed improvement of the lighter ski over the heavier ski over successive 1 km segments in the course of a 7km run.



While the chart looks like I must have got excited on the lighter ski and gone hell for leather in the first few km, in practice I was paddling with roughly the same intensity as normal.
In very general terms, some tentative conclusions are:

1. A lighter ski can be accelerated with greater ease and /or to a greater speed.

2. When momentum becomes the larger contributor to forward motion (which happens as speed increases), the paddler has to apply more effort to maintain a lighter ski at speed.

3. While the lighter ski enables the paddler to get to a higher speed, the paddler then needs to run the engine at a more intensive level to keep the ski travelling at the higher speed.

In a nutshell, the lighter ski improves the strength ratio, giving you the potential to go faster, but you may have to operate at a more intensive aerobic rate to get full use of that potential.

I’ll feed back some more accurate data as I build up the lighter ski history.

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10 years 5 months ago #9148 by Dicko
What we need is a carbon ski weighted to 17kg. Then we could compare times. That may give us more insight as to whether the increase in speed is due to the weight of the ski or the stiffness of the ski. If it is purely due to weight, then a lightweight vacuum bagged glass ski is a true bargain.

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10 years 5 months ago #9178 by AGA
Came across this from the Editor of RoguePaddler from a few years back. Further thoughts highlighting that it takes more energy (either via more force or faster cadence) to maintain a lighter boat than a heavier boat at high speeds, due to the lower momentum.

"In a lighter boat, more force must be supplied by the paddler to punch through waves, maintain speed, and stay on track. In contrast, a more heavily loaded boat possesses greater momentum, meaning that more kinetic energy is built up and stored in the hull... True, more effort is required initially to accelerate the heavier kayak, but this effort is not entirely "wasted" as many people think. A loaded kayak can easily maintain the same cruising speed as it can unloaded. In fact, once brought up to speed, the energy required to maintain a steady "glide" in the loaded kayak is negligible compared to the unloaded kayak. Yet the loaded boat possesses a much higher kinetic energy that can power through diverting forces with less penalty to speed or direction. In many conditions, it is even true that the loaded boat can maintain its efficient glide despite a slower paddling cadence... the additional energy expended to accelerate a heavier kayak does become advantageous again in the form of greater momentum. It is not "wasted," but rather stored and re-released in a way that typically yields better tracking and a slower paddling cadence as I mentioned."

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10 years 5 months ago #9182 by Rightarmbad
Unfortunately, our boats don't maintain a steady speed.
If you listen to your scuppers or watch the water in your footwell, you will no doubt see the constant accelerations and decelerations.

There is always a loss involved in accelerating or decelerating things, always.

The more mass you have to change direction/speed, the more the losses, so no, a heavier boat, even if it's water line stayed the same as a lighter boat is not as efficient.

His argument dies in the details.

Follow the path of the independent thinker. Expose your ideas to the dangers of controversy. Speak your mind and fear less the label of 'crackpot' than the stigma of conformity. And on issues that are important to you, stand up and be counted at any cost.--- Thomas J. Watson

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10 years 5 months ago #9199 by AGA
At low speeds the ski's forward motion is driven mostly by the force from the paddle, with momentum contributing little. Hence you get a large proportionate benefit from a lighter ski (which improves the result you get from each paddle stroke).

The faster the ski goes, more of the forward motion comes from the momentum of the ski and a lesser proportion from the force of the paddle. Once more than 50% of the forward motion comes from momentum it takes more energy to paddle the lighter ski (as the decrease in momentum has a bigger impact than the benefit of the lighter ski on the paddle stroke).

I actually think this supports your fast cadence strategy. The lighter ski improves both the efficiency with which you can get to a high speed, and the better strength ratio allows you to get to a higher speed than you can on a heavier ski. But once you are at the higher speed you have to offset the momentum loss with more intensive paddle work (either or both of fast cadence or more pull).

The fast cadence is also needed to get the paddle to bite at the higher speed with which you're moving through the water.

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10 years 5 months ago - 10 years 5 months ago #9207 by Kocho
The acceleration argument aside, I don't think it is nearly as straightforward and I think there maybe a valid argument to be made that a really heavy kayak (70lb, let's say) may indeed be more efficient to paddle at a steady pace in slightly choppy conditions than a lighter one with similar shape (so that wave and friction resistance would be similar in flat water). The lighter one would bounce off each ripple in the water, splashing and jumping about. My reasoning is that the lighter one would go up/down and would thus splash a lot more, dive or go "up-hill" on waves, etc. and thus offer an underwater profile that is not ideal. The heavier will move water aside and maintain a steady heading with a nice consistent underwater profile, thus creating less of a drag wave (splashing is presumed minor compared to the waves created due to speed).

On the other hand, I can make the argument that a lighter kayak will go "over" waves as opposed to cutting through them, thus displacing less extra water when going over wave crests or plunging down the wave face compared to a heavier kayak.

I realize the two arguments I just made are somewhat contradictory, but depending on conditions one may indeed be valid and the other not, when in other conditions the opposite may be true...

Who knows...
Last edit: 10 years 5 months ago by Kocho.

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10 years 5 months ago #9211 by Rightarmbad
So, ignoring a greater waterline of a heavier boat and just assume that there is the same wetted area and displacement.

A heavy boat will still be hit by the same forces to slow down as a lighter one.
If the force you apply to the boat with your paddle exceeds the decelerations, you will go forward.

This decelerative force is exactly the same, if the accelerative force you apply is exactly the same to both boats, irregardless of boat weight, you will go forward

But...

There is more losses in the process to accelerate the heavier craft. More paddle drag
There is still the same drag on the hull.

Because the boat is always, slowing down and speeding up on a micro scale, any energy gleaned from forward momentum is offset by the more force required to get it back up to speed, but the inefficiencies involved in applying these larger powers will always leave you on the negative side.

If not, there would be all sorts on perpetual motion machines around to claim some pretty big prizes on offer for doing so.

Follow the path of the independent thinker. Expose your ideas to the dangers of controversy. Speak your mind and fear less the label of 'crackpot' than the stigma of conformity. And on issues that are important to you, stand up and be counted at any cost.--- Thomas J. Watson

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10 years 5 months ago #9222 by Kocho

Rightarmbad wrote: ...A heavy boat will still be hit by the same forces to slow down as a lighter one.


True, but the same force applied to a lighter boat results in a larger reaction so to speak - the hull will jump up/down/sideways more. So, while I do not claim this to be true, I think (until proven otherwise), one could technically argue that the hull will not glide as smoothly and will not be aligned along its intended path nearly as well, requiring more corrections and being subjected to water forces from directions that would not be hitting the heavier hull which is just plowing forward.

But as I said in my own "counter example", one can argue that the above is offset by the lighter boat floating over ripples and thus disturbing less water compared to the heavier boat, which has to displace more water while resisting the said ripples and tossing them aside or going under...

I was actually trying to argue both points and my conclusion is that without actual tests one can write arguments for both sides -;)

However, my own subjective observations are that lighter boats tend to cover distance better for me, with less effort, and are definitely easier to get up to speed to catch waves or to maneuver (not necessarily speaking about skis here, but kayaks in general).

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10 years 5 months ago - 10 years 5 months ago #9224 by Kayaker Greg
But a heavier boat should have more glide before its slows, meaning your cadence can afford to be slower, because if you do try to paddle too fast, before the boat glide slows, the act of putting your paddle in the water is a brake so slowing before the stroke begins, so putting your paddle in the water before it slows is counter productive and a waste of energy, more glide, slower cadence, easier on the cardio. Follow?

But a ski race can be all about acceleration, to get on a wake, a wave, break away, so I believe lighter is better.
Last edit: 10 years 5 months ago by Kayaker Greg.

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10 years 5 months ago - 10 years 5 months ago #9225 by Kayaker Greg
Recently I paddled to a sea kayak race being held on an Island. I had all my camping gear, food, water, after paddle clothes etc for the weekend on board so I guess the weight of the gear was about 50-60kg my kayak weighs roughly 20kg. At the last minute a local guy shows up with his 12kg Supernova which is a light weight racing sea kayak. Within about a minute of the race start he accelerated and I could not go with him to get on his wash, no way and I tried. However I did get up to speed and at the end of the 10km he only beat me by about a minute. My heart rate held 92% of max the whole way and I felt good, but if my boat had been lighter and I could of accelerated, who knows? Perhaps he only did enough to win, but he was training for a big multisport event the following weekend and was probably half my age as well. Next year I might unload my boat, but really couldn't be bothered on the day. I did beat all the other sea kayaks that were not loaded down with gear like mine was.
Last edit: 10 years 5 months ago by Kayaker Greg.

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10 years 5 months ago #9227 by Rightarmbad
What makes you think putting your paddle in the water slows you down?

Follow the path of the independent thinker. Expose your ideas to the dangers of controversy. Speak your mind and fear less the label of 'crackpot' than the stigma of conformity. And on issues that are important to you, stand up and be counted at any cost.--- Thomas J. Watson

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10 years 5 months ago - 10 years 5 months ago #9228 by Kayaker Greg
Just something I read somewhere on the internet so it must be true, right? But seriously, I'm not sure where I read it, it was on something I was reading on paddle technique, sure you have to be careful what you believe, just adding to the overall discussion and food for thought. I have no hard evidence that its true or not.

Ok just did a very quick Google search and this came up, might find it interesting, have not read the whole thing myself yet but it does mention about glide and letting the boat run and the paddle acting as a brake if put into the water too soon.

www.oceanriver.com/training.htm

Also here, www.canoeicf.com/...technique/chapter%206%20-%20technique.pdf Greg Barton on stroke rate states that if your accelerating, the boat starts to slow as soon as the paddle leaves the water (obvious right cause the power is no longer on) but if the boat is up to speed in flat water, you can afford to have a pause between strokes because it will maintain most of its speed, which to my mind is more efficient. Also laws of physics dictate that a heavier boat will have more glide, right? Off course flat water, rough water, lots of variations, and as I said before, acceleration is important in ski racing, so again, a lighter boat should be a better choice.
Last edit: 10 years 5 months ago by Kayaker Greg.

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10 years 5 months ago #9229 by Rightarmbad
Boat glide is only good if you expending all of your effort in the stroke and have nothing more to give.

For me, I simply am not.
The more strokes a minute I can get in, the faster I go.
If I could halve the time taken for my recovery stroke, I would simply go faster.

With a K1, the glide is important as it is the only time that the boat is not significantly disrupted by the paddle stroke, and is therefore a very fast part of the total stroke.

With our long lean machines, there is very little disruption from the paddler and the boat maintains it's efficiency even throughout the power phase.

From what I have seen in a technical stand point, the shorter/bigger the power phase is, the faster the boat goes.
Even if a long stroke has more total power, the shorter higher peak is faster.
So the more of the these peakier strokes you can get in the better.
Also links to a larger paddle size.


In the kayaking world where 220cm and larger paddles seem to be the norm, putting the paddle into the water may very well act as a brake, the same reason why I cannot start paddling at very high speeds with a longer paddle, yet have no problem with a shorty.

The ability to get a shorty more vertical I think is an important benefit.

Follow the path of the independent thinker. Expose your ideas to the dangers of controversy. Speak your mind and fear less the label of 'crackpot' than the stigma of conformity. And on issues that are important to you, stand up and be counted at any cost.--- Thomas J. Watson

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10 years 5 months ago - 10 years 5 months ago #9230 by Kayaker Greg
I was told one time by Katie Pocock (top World Womens ski racer) during one of her squad sessions that when she is racing next to a fellow ski racer that she works on slowing her cadence so that she is maintaining speed with the other paddler, but is working more efficiently, so I guess maximizing her technique rather than trying to up her rating and perhaps blowing up. Just something else to consider.

Opps, think we might be crossing over into the other thread on paddle size and length and cadence.
Last edit: 10 years 5 months ago by Kayaker Greg.

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10 years 4 months ago #9253 by AGA
As I've worked through this a bit more, I can correct some of my earlier thoughts about momentum.

The force which the ski must overcome in order tomove forwards is drag. It turns out drag is not dependent on weight. It is primarily dependent on the speed of the ski (squared) and the shape of the hull which dictates the surface area on which the drag acts.

Total ski speed is the combination of the speed of the ski before the stroke plus the benefit of the acceleration provided by the paddle stroke. At low speeds most of the speed comes from the paddle stroke, and at high speeds most of the speed comes from the existing speed of the ski before the stroke.

The only place weight comes into this equation is that the lower the weight of paddler + ski, the greater the acceleration benefit from the paddle stroke.

If you combine the drag equation and the equation for the acceleration benefit from the paddle force being applied to weight, the speed improvement from lower weight is 1/6th of the change in the combined weight of paddler and ski.

The important concept is the fact that drag from liquids on a surface is not weight dependent. I think that also suggests that two skis of different weights at the same speed would slow at exactly the same pace, which may answer the question in another thread looking at that issue.

Where momentum (the weight x the speed) does impact on a ski is where there are non-drag forces, such as wind and waves. In these instances the weightier ski carries more momentum and will be slowed less by a headwind and be accelerated less by a tailwind.

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