Surf ski speeds

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7 years 6 months ago #26526 by Aurelius
Surf ski speeds was created by Aurelius
I've read many reviews comparing one surf ski to another, but what's always missing is any hard data to support claims like, "Surf ski A was faster than surf ski B". Why aren't these performance differences expressed in some objective metric like miles per hour, so that readers can fully grasp what's being asserted?

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7 years 6 months ago #26527 by [email protected]
Replied by [email protected] on topic Surf ski speeds
There are so many factors involved with surfski speeds, I'm deeply sceptical about claims that one ski is faster than another - especially when they're fairly similar.

For example, a stable intermediate boat like an Evo II will actually be faster than a top of the line Fenn Elite S or Epic V14 - when it's paddled in choppy water by an intermediate paddler.

So any comparison should include caveats about the capability of the paddler, how long they've been paddling the boat and what the conditions were for the test.

Many years ago we did a comparison of a number of boats using a group of paddlers going flat out over a short distance. The idea was to try to average out the results over the paddler capability and to take out complexity caused by rough water (we did the test in a harbour) and we came up with a set of results.... I think that was probably the closest anyone could get to an objective comparison.

Of course you can subject hull shapes to flow dynamics modelling and you can say which hull has the least drag - but if the super sleek hull responds badly to confused chop, it changes the situation completely. I don't don't think anyone has been able to model how hulls respond from a stability point of view in confused water - or how they respond going downwind...

So there's a lot of black magic involved... you'll always go better in a boat that you're comfortable in!

If you hear a manufacturer claim that their boat is 4% faster - all it means is that they think that the drag of the boat is slight less than the competition - but they can't tell you whether your backside will fit the boat comfortably or whether you will feel more stable because their cockpit is 20mm wider at the thighs...

Rob

Currently Fenn Swordfish S, Epic V10 Double.
Previously: Think Evo II, Carbonology Zest, Fenn Swordfish, Epic V10, Fenn Elite, Red7 Surf70 Pro, Epic V10 Sport, Genius Blu, Kayak Centre Zeplin, Fenn Mako6, Custom Kayaks ICON, Brian's Kayaks Molokai, Brian's Kayaks Wedge and several others...

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7 years 6 months ago #26528 by Aurelius
Replied by Aurelius on topic Surf ski speeds
Just for clarification, I recently tested two skis made by Stellar on a smooth lake in pretty much windless conditions. One was the SR and the other was the SEI. The SEI was not only rated the faster of the two, but the one I happened to test was the lightweight Excel layup, weighing just 26 lbs compared to the SR's Advantage layup at 33.1 lbs (according to their website).

Yet despite these differences, my top speeds in both boats were identical according to my GPS. The SEI was noticeably less stable than the SR at the start, but any instability issues went away once I reached speeds of 5+ mph. I repeated the test several times, but in each case the result was the same: no speed advantage at all for the SEI. Given the superior stability of the SR and it's much more attractive price, that's the one I ended up buying. I don't regret my decision in the least, but I am very puzzled as to why the SEI's more aggressive hull geometry and lighter weight didn't translate into better speed. My only thought is that perhaps whatever speed advantage it does have is so minuscule that it simply didn't register during the relatively short sprints I performed on the lake, but that it might show up in a race several hours long. Or could it be that the SEI's performance advantage only shows up in turbulent ocean water?

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7 years 6 months ago #26529 by [email protected]
Replied by [email protected] on topic Surf ski speeds
Another complicating factor is that hull drag varies with speed and it's possible that at the speeds you were paddling the boats, the drag might have been similar but that with a Hank McGregor or an Oscar Chalupsky in the boat, the drag of the SEI might be less at the speeds that they'd be doing...

But I'd wager that on a longer paddle, especially on rough water, you'd be faster on the SR given that you noticed a perceptible difference in stability with the SEI.

I used to paddle a Fenn Elite, but although I loved the boat downwind and scored my personal best Miller's Run in it (44:52), I've come close in the much more stable, yet theoretically slower Think Evo II. I'm pretty sure that in small conditions, I'd be faster in the Elite, but in bigger, choppier conditions, I'm sure I'm faster on the Evo II because I'm not losing power to staying upright.

I think your decisions was absolutely the right one.

Rob

Currently Fenn Swordfish S, Epic V10 Double.
Previously: Think Evo II, Carbonology Zest, Fenn Swordfish, Epic V10, Fenn Elite, Red7 Surf70 Pro, Epic V10 Sport, Genius Blu, Kayak Centre Zeplin, Fenn Mako6, Custom Kayaks ICON, Brian's Kayaks Molokai, Brian's Kayaks Wedge and several others...

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7 years 6 months ago #26530 by Aurelius
Replied by Aurelius on topic Surf ski speeds
I'd considered that possibility as well, but I have no idea how fast elite paddlers like McGregor and Chalupsky normally go. Right now I'm hitting speeds of 7 to 7.5 mph on flat water. That's about what Wesley Echols does in his videos, but of course he does it in the sea and for much longer periods. I've only paddled in open water twice, once in Bristol, RI, and at Daytona beach. My recollection is that it's much harder to go fast in the ocean, not just because of the added challenge of keeping the boat upright, but because you need to time your strokes just right to make decent power on rough water. Once I get back in shape, I may give the Stellar SEL a try, just to see how it compares to my SR.

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7 years 6 months ago #26531 by M.v.E.
Replied by M.v.E. on topic Surf ski speeds
I paddle a Stellar SR for 5 years now but it´s the old version. A few years ago I bought a SEI Advantage. I am not a fast paddler. So with the SR I was able to hold an average speed of 6,5 mph over a longer distance on flatwater.
With the SEI its around 7 mph. The new SR is supposed to be faster so the speed difference might be less.
I have the impression that the SEI has a lot more speed potential but with my technique and power I am not able to go much faster. I don´t get the chance to paddle in decent waves that much but when I do I prefer the SR over the SEI because of it´s stability.

Michael

Current Ski: Nelo 550 L
Previous Skis: Stellar SR 1. Gen. / Stellar SEI 1. Gen. / Stellar SR 2. Gen.

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7 years 6 months ago #26533 by photofr
Replied by photofr on topic Surf ski speeds
Indeed, there are a lot of variables going on.
As mentioned, the weight of the ski, the hull shape, the fit, the conditions that you may be more comfortable in, etc...

There are also factors where a ski might be slower for YOU, and faster for me, sometimes because of my weight, and vise versa.

Specifically for me, the 560M is the fastest ski I have ever been on - all the while I am in the worst shape ever. I do believe the comfort of the cockpit, and elevated seat have more to do with the speed I now attain than anything else - for flat water.

Downwind, I feel that with my experience, I am able to surf and stay on runs far longer than ever before. At 5.6 meters, the ski is far more maneuverable for me.

Specifically, with my feather weight, I averaged 10km/h with the Spark, and now 11km/h + with the 560M - and I still feel like I am not even close to the shape I was in last year with the Spark.

Basically, you'll find that stability and speed is an "individual" thing on flat water. Add rough water or downwind, and it's even more complex as mentioned by others.

Ludovic
(Brittany, France)

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7 years 6 months ago #26534 by Crossey
Replied by Crossey on topic Surf ski speeds
It's actually both harder and easier to paddle quickly in the ocean. While paddling upwind is always going to be slower than paddling in calm conditions paddling downwind for any experienced ocean paddler, let alone elite paddlers, will be quicker than paddling in flat conditions.

As already raised by others, this throws in an additional complication, in that even for the same paddler different skis will perform optimally in different conditions (flat, small runners, big swell etc) so you are better off finding the ski that works best for you in the conditions you're likely to be paddling. Which is what it sounds like you've done.

After that, you're going to see much better returns from increased fitness and more importantly improved technique than jumping to a new boat. Which is good because it's cheaper, even if it's harder work!

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7 years 6 months ago #26535 by Ranga
Replied by Ranga on topic Surf ski speeds
There is a good article on the Epic web site on the speed difference between the Epic range. Greg Barton did the tests so this will be accurate, plus he has the ability to paddle ALL of the craft at the same ability. What does come out of it is that the speed differential is very little for most of us. This is not a sprint test.
I often get this, "This ski is much faster!" I ask, " How much", and the answer is usually " It feels faster", well this is useless info to anyone. Like a top end sprint, unless you are doing a race of 30m or so whats the point. The weight of the ski is more important if you want to get on the waves, acceleration is what you want, instant speed.
As for me I am faster on the V10 Sport than the V10 over longer 12-25km distances downwind. The reason is stability and manoeuvrability and weight of the ski, so there are many variables, all add up to around 2min over a 2hr race.

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7 years 6 months ago #26536 by Oskar
Replied by Oskar on topic Surf ski speeds
Many years ago I was curious about the same thing and did some controlled tests using gps speed and heart rate as parameters. What surprised me was how little difference there was between the "fastest" and the "slowest" boat. Throughout the speed range from easy cruise to all out maximum the difference stayed very close to 5%, which works out to less than a boat length over 100m.

Differences in speed of more than 5% are all about the paddler, not the boat.

www.fennkayaks.co.nz/speed.htm

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7 years 6 months ago #26537 by RedBack
Replied by RedBack on topic Surf ski speeds
Aurelius, - boats of different sizes and hull geometries will invariably have a different and non-linear relationship between (additional) effort and (additional) speed.

For example the difference in effort required to paddle a K1 at 12 kph versus a ski at 12 kph is minimal.

Increase the speed to 14 kph though, and significantly more effort is required to maintain that on the ski than in the K1.

Imagine a graph with speed on one axis and effort on the other. Up to around 11 kph, two boats may have indistinguishable differences in their plot lines, but at speeds above that, the two lines might diverge rapidly.

Perhaps this is what you encountered with the SEI and the SR?

Having said that though, the "new" SR seems to be a pretty quick boat and I know several paddlers who have swapped across to it from other brands and immediately picked up speed.

Enjoy your ski!

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7 years 6 months ago #26539 by Ronbo
Replied by Ronbo on topic Surf ski speeds
As others have said, it’s pretty difficult to isolate all the variables for ocean paddling, so it’s always going to be pretty subjective. Experienced paddlers that have done a course many times, saying “I was two minutes slower on this ski” is about the best you can do to get a feel for it.

I recently did some objective flat water testing on two of Carbonology’s latest intermediate skis, the Boost and Zest. Everyone seems to know and love the Swordfish as an intermediate ski, so used that as a standard to measure against. Even flat water testing was a challenge to remain objective. Things I tried to neutralise include:

  • have both skis I am testing available at the shore to easily swap between them
  • pick a relatively calm day with very little non-gusty breeze. My two afternoons of tests were a steady very light 4kt breeze.
  • paddle over the same courses. My courses were about 1km long, one into the breeze and one with the breeze
  • paddle on flat lake in an area with no tidal current. I was western part of Narrabeen Lagoon in Sydney.
  • do a few km’s warm up before any measurements
  • pick a steady “all day” heart rate so as not to get tired doing multiple back to back trials. I chose 130bpm, speeds of around 10.3 to 10.9kph.
  • make sure you are at that steady state heart rate and speed well before the beginning of the trial course
  • I had a solid carb based meal well before paddling, with no sugars or caffeine before or between testing each ski
  • big drink of plain water between each ski change to remain fully hydrated


The results were interesting:

Zest (hybrid) v Swordfish (carbon)
Zest was 2-3% quicker than the Swordfish. This confirms about how it “feels” and was not surprising.

Boost (hybrid) v Swordfish (carbon)
Swordfish was 0-1% quicker than the Boost. This is the one that was surprising, since the Boost is wider, flatter bottomed, heavier, and shorter than the Swordfish. I expected it to be several percent slower. After double and triple checking my data, I was questioning my methods. GPS and heart rate monitors don’t lie though. The breeze didn’t fluctuate during the afternoon.


People don’t normally buy any of these skis for their all-day cruising speed on flat water, but it’s an interesting data point for comparison. As mentioned above, it doesn’t mean the relationships will hold in downwind, faster flat water efforts, or different sized paddlers (I am 90kg).

That was the first and last time I’ll ever do those kinds of trials. Pretty dull spending a couple hours paddling up and down the same courses in minimal breeze at a steady moderate heart rate. It satisfied my inner geek though. I can fully understand why there isn't more comprehensive objective speed data available across all ski models.

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7 years 6 months ago #26541 by photofr
Replied by photofr on topic Surf ski speeds
Last year, we gathered a bunch of people to do speed tests on the latest SUP gear. It took the best part of the day to complete, including 5 boards and 5 people in the water. We all took turns, and YES, the results were very interesting.

It was worth it, but so boring, and time consuming... and in the end, we only data for flat water.

I much prefer the following method that seems to work best in open water:
Take two paddlers of similar weight, and speed. Say, a slightly faster paddler, and me.
Put him in ski No. 1 and place yourself in ski No. 2.
Go downwind, and swap skis (get on the same ski at least twice).
If I am able to catch the faster paddler in Ski No. 1, then this tells me that ski No. 1 is faster.

Even then, it's subjective - but it's my favorite way to test boat speed in open water, because you can apply this technique upwind, or side wind... and even apply this to chaotic conditions.

Ludovic
(Brittany, France)

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7 years 6 months ago #26542 by [email protected]
Replied by [email protected] on topic Surf ski speeds
Yep, this is such a cool topic - yet such a fraught one.

Like Ludovic, I've tended to paddle a couple of downwinds, swapping boats with a paddling buddy whose capabilities I know in order to try to perform comparisons.

The problem is that you have to do it a number of times in order to try to average out the changing conditions... And even then...

The conditions on our Miller's Run vary radically from day to day. Ostensibly it's the same run, the same distance, but the wave conditions vary from round, clean swell in the same direction as the wind, to choppy mixed wave fronts coming from several different directions. In these conditions (short, messy, mixed) I find some boats get thrown sideways more than others - and although the boats are equally stable, I find it really difficult to accelerate some but not others. But then the next time the runs are clean and long and it's easy to get any of the boats going...

The more I know, the more I don't know!

Rob

Currently Fenn Swordfish S, Epic V10 Double.
Previously: Think Evo II, Carbonology Zest, Fenn Swordfish, Epic V10, Fenn Elite, Red7 Surf70 Pro, Epic V10 Sport, Genius Blu, Kayak Centre Zeplin, Fenn Mako6, Custom Kayaks ICON, Brian's Kayaks Molokai, Brian's Kayaks Wedge and several others...

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7 years 6 months ago #26543 by Aurelius
Replied by Aurelius on topic Surf ski speeds
So I guess the takeaway from all this is that unless you're a seasoned racer trying to save every calorie of energy, the differences in speeds within the same class of surf ski are negligible?

That's pretty much how things look in the world of cycling, which I've been involved in for the past five years. Hundreds of hours of computer simulations and wind tunnel testing have produced aerodynamic frames and wheels faster than anything that preceded them, but what manufacturers fail to mention is that these speed increases are typically measured in seconds gained over a 40 meter distance. Mere seconds may be the difference between first and third place in a closely contested time trial, but it's absolutely meaningless to the average cyclist.

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7 years 6 months ago #26544 by Aurelius
Replied by Aurelius on topic Surf ski speeds
That had occurred to me. It's well known to aircraft designers that a shape optimized to produce the least drag at a certain velocity will not be optimal at other velocities, so it's hardly surprising that the same principle applies to boat hull designs. In fact, boat hulls may be even more sensitive to velocity, given the much higher viscosity and resulting drag of the medium they travel through.

Still, I had both the SR and SEI up to 7.5 mph, which seems to be in the ballpark of what experienced paddlers average in a race, so I would think that if the graphs did diverge sharply at a certain point, it would have to occur at around 7 mph for racers to be able to capitalize on the SEI's superior efficiency. It obviously wouldn't do any good for that divergence to occur at say, 9 mph.

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7 years 6 months ago #26545 by Aurelius
Replied by Aurelius on topic Surf ski speeds
16.1 kph is a very impressive speed in a Mako XT!

My XT never seemed to go that fast. Perhaps it was due to a factory defect. ;-)

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7 years 6 months ago #26553 by nell
Replied by nell on topic Surf ski speeds
A couple of things that seem to make sense to me - other than what's already been mentioned:

It's really difficult to evaluate the speed of the ski if you're not doing the comparing yourself and putting in high effort. For example, when I evaluated the V10, 12, and 14, I compared them at "the steep part of my curve", which was at steady state speeds of about 13 kph for about 8 minute intervals. It would have been meaningless to compare them at lesser speeds where I can't tell the difference between putting in marginally more or less effort.

I don't see how skis can be compared downwind with much accuracy at all because paddling downwind is 90% skill and decision making and 10% the hull's speed (generalizing about the numbers). However, different skis have different qualities like steering and weight distribution that allow one to go faster on one ski than on another, so I "get it" that someone can go faster downwind on a certain ski. But, I don't necessarily think that it's the ski's speed that's evaluated as much as it's the paddler's ability to mesh with and go faster downwind on a particular ski .

I recently tried to compare the speeds of a couple of elite skis and thought that max sustainable speed might be somewhat reliable if using deep flat water on the same course and a gps readout that is averaged over a few seconds of time. Of course, the comparison would only be considered reasonably valid if the skis were of similar length and shape - which they were. I was able to consistently go 0.5 mph / 0.8 kph faster in one of the two after comparing them back to back about 20 times total. While it's tempting to conclude that one hull shape is therefore faster than the other, the "slower" one had a slightly wider catch and a slightly lower seat height which might have contributed some if not all of the difference in speeds.

I find this curve interesting - especially the Nelo data - but, of course, it's all subjectively derived:
www.performancepaddling.net/nelo_560_2016model.html (scroll 2/3's down the page)

I'm scratching my head about this one because I used to think that a shorter race boat with less surface area would have less resistance (be faster) at lower speeds, but that a shorter waterline would have more wave resistance (be slower) at higher speeds. Racing K1's were somewhat"immune" to this idea since they have such a narrow waterline - or so I thought. The 560 has a ski's waterline width, so it should follow the rules of longer elite skis, but the curve suggests the exact opposite, i.e. it's slower at lower speeds and faster at higher speeds. I know it's complicated, but if this data is reasonably accurate, what am I missing here?

EB

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7 years 6 months ago #26554 by red_pepper
Replied by red_pepper on topic Surf ski speeds
I interviewed Dr. Ted Van Dusen for a Canoe News article a few months ago, and he had some interesting things to say about speed vs. waterline length (for flat water):

....
CN: Tell me about the Mohican: how did it come about?
Ted: I found myself taking a few too many swims in my ICF boats as I worked on developing my paddle technique, causing me to focus more on staying upright than on my paddle stroke. I decided that to improve I wanted to design a boat I could paddle comfortably but which would have the speed of an ICF boat. I intended to build a shorter boat initially, but as I worked thorough the various iterations I found I needed a 21 foot waterline to achieve good speed. I gave the boat an ICF –type cockpit because I liked the paddling position of the ICF boats. The prototype boat had an open hull like an ICF boat, but subsequent models had sealed hulls and an Andersen bailer like surf skis. Dumping the boat once in a race convinced me that emptying a 21 foot open boat was a greater challenge than I cared for. As for speed, the Mohican is as fast as an ICF boat up to 8 mph, but with greater stability. It was also carefully designed for minimum drag in shallow water, where wave drag can increase 4x – 6x what it would be in deep water; this design characteristic has given the Mohican its reputation for being somewhat immune to the effects of “suck water”.

CN: Why is the Mohican as fast as an ICF boat only up to 8 mph? I’ve heard that wetted area drag predominates until typically 4.5 mph or so, when shape drag predominates.
Ted: As a boat builds speed it creates a wave at the bow, followed by additional wave crests. When the boat is going fast enough so the second crest is at the stern it is said to be at “hull speed”; because, it takes a large increase in power to go faster as the stern drops and the boat climbs up on its bow wave. As the boat is pushed further above hull speed there is a point where the increase in wave drag becomes less severe and may actually increase less steeply than the viscous drag from the wetted surface area. With its hull shape and long waterline, the Mohican has less wave drag than an ICF kayak; however, above 8 mph its viscous drag is increasing more quickly than its wave drag and with its larger wetted surface it loses to the ICF kayak. Interestingly, a fuller bow and stern with a thinner midsection is also optimal at higher speed, rather than the sharper bow and stern that works effectively at slower speeds. It took quite a bit of analysis to find the minimum total drag at the power output of an athlete with the additional effect of varying water depth.
The following user(s) said Thank You: nell, RedBack

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7 years 6 months ago #26555 by Aurelius
Replied by Aurelius on topic Surf ski speeds
Fascinating article, red_pepper. Where can I buy one of these Mohicans? B)

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