Paddler Weight & Ski Weight Ratio and Speed

So you just come up with the same solution as me only one page in the thread later, cool.......

Not biting on that one RAB.

Here are the details on the speed trials I’ve been running, as well as updated results.

I have started to test the skis in a range of conditions, but at this time have only used the flatwater, same course, low wind results to assess speed, as these provide the most consistent basis for comparison.

I sought to measure both the average speed over a total distance as well as average speed on individual 1km splits. I have only included measurements across the last four weeks, to limit the impact of any change in fitness or technique.

The courses were round trips of around 45 minutes, allowing the prevailing wind, tide or swell conditions to be borne approximately equally as a benefit and disadvantage. The courses were not straight line and included conditions being borne head on, from the stern, side-on and shades between.

The caveat on the results is that the model of the skis used are not identical (had to use what I had on hand). The heavier ski is an Epic V10 in fibreglass (16.3kg), the lighter ski a Stellar SES Excel construction (10.7kg). From the speed assessments conducted by others, the speed differential between the skis due to the make & model (rather than weight) is small. Wesley Echols rates the speed of an equally weighted V10L and Stellar SES as 5.95 and 6.0 respectively in all conditions (and 5.95 and 5.98 on flatwater), and anecdotally I read of others who would rate the V10 as a shade faster. The paddler has familiarity with the V10 and no prior experience with the SES, except for the testing period.

This isn’t a comparison of Stellar vs Epic, and I have no doubt I would get similar results on a 10.7kg V10.

Outcomes

The latest outcomes are shown below. The results to date are giving a speed differential of 7% which is similar to the change in the load ratio (being paddler weight / [ski + paddler weight]) of 6.9%.

Theoretically the impact on speed due to the change in weight and change in wetted surface area should be 1/6th of the change in the load ratio (1/6 of 6.9% = 1.2%). So the results show that potentially a larger improvement in speed can be achieved than the theoretical measure suggests.





What Does It Mean?
A lighter ski will/should give a speed benefit, there is no doubt. A lighter ski is much easier to accelerate.

While the theoretical benefit from lighter weight is 1/6th the change in the load ratio, there appear to be additional practical benefits from paddling the lighter weight which also contribute to the overall speed improvement.

Two additional benefits from a lighter ski come to mind.

When paddling into the wind, acceleration is a larger part of the paddling equation. A ski slows faster in the recovery phase of the stroke when heading into the wind, and needs to be continuously accelerated to maintain speed. In practice I have found it much easier to maintain speed in the lighter ski than the heavier ski in a headwind. This can be seen in the table above, where the variation in speed on the lighter ski is much less than the variation in speed in the heavier ski.

The theoretical improvement in speed at 1/6th of the load ratio change relies on the assumption that there is no change in the force supplied by the paddler. In practice however, the force supplied by the paddler is limited by one or both of paddler strength and aerobic ability. I suspect that in many cases, especially for your average, non-elite, run of the mill paddler like the tester, the limitation is more paddler strength than aerobic capacity. If this is the case, a lighter ski allows the paddler to increase the force supplied by as much as the full improvement in the load ratio, even if the paddler is utilising some spare aerobic capacity to do so.

The 7% difference has just about got me convinced. Goodbye fibreglass, hello kevlar and carbon.

AGA
good to see someone trying to come up with some data.

I have just come aross an article by erik borgnes on the epic international web site on how does ski weight impact on speed and performance the ski's he tested were the same only 3kg difference in weight not 5.6 like yours.

I would be interested in you thoughts of his outcome.

can be found under news and events and about the 14 page

I'm still trying to decipher your last sentence, but do you mean that because the ski is lighter, it accepts the torque on the paddle quicker, allowing more power to be produced because of it's more rapid application?

If so I agree.

My own very small data set suggested a .3km/h benefit for me to go from my current performance layup V10 to a 9kg job.

If you are in a canal, don't forget the effect of the shallow bottom tending to slow the faster ski more than the slower, as well as different tide times having different depths.

The canal down here that I spent a fair bit of time in on a loop course, responds quite differently to tide direction/ depth and slope.

With the right combination giving me a 3 min or there abouts advantage over the slowest conditions in the same boat over 6kms.

On the Erik Borgnes comments, he notices the acceleration benefit, but thinks the underlying speed difference of a 3kg change leads to a small speed benefit.

He's 90kg, so the load factor change is 2.8%, and theoretically the speed benefit at 1/6th of that is 0.47% or around 0.05kmh which is what he suggests.

He's also a competitive paddler so probably getting full use of his strength and aerobic capacity on both lighter and heavier skis, meaning the speed difference he's getting is close to the theoretical measure.

Contrast that to a lighter paddler, such as my 70kg, and consider that non-elite paddlers are paddling a bit below their maximum capacity. In this instance, it seems the weight improvement not only gives the theoretical speed difference but also allows the paddler to paddle closer to maximum capacity.

I could liken the weight change to a change of gear when riding a push bike. If you use too heavy a gear when riding up a steep hill, you will hit your strength limit and progress very slowly. If you change to a lighter gear, you may have to peddle faster, but you will shoot up the hill at speed.

RAB, that comparison might be a better explanation of what I was angling at with that other sentence.

Its a good point on depth and tides. Having spent the last few weeks with the Garmin strapped to the footstraps, its been an eye opener as to where speed variations can occur on a course. The one that's surprised me most is currents.

I'm usually thinking most about the wind impact, with light winds adding or subtracting about 0.3 kmh, and heavier winds progressively more. But I came across a short stretch where my speed jumped up by a good amount more than 1 kmh in no wind or even against the wind, and did so every time I paddled the segment. I realised I was getting a rocket from a very localised current.