Upwind is a Heavy or Light boat best?

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9 years 9 months ago #15503 by Kocho
Then, there is the school of thought that more flex/compliance with the water under it makes a craft faster. That comes from folks who build skin on frame (SOF) boats, which tend to be rather flexible compared to composite boats. There might be something to it, because, rather than displace extra water cutting through waves it snakes on top of some of it. I built one a couple of years ago and it was quite flexible indeed, but I could not figure out if it was any faster for it... It was just annoying IMO and changed the rocker of the boat when in the water outside of what I had planned for it when I designed it...

Of course, the level of flex one gets in a glass boat would not be anywhere nearly as much as in a SOF as to make a difference IMO this way...

Aside from stiffness, whcih I don't think matters in this case much, I think a lighter boat will float over more waves and would need to shove out of its way less water, thus making it faster upwind. It is not only the overall weight, it is the swing weight that is important too - less swing weight (less weight at the ends) means the boat will wobble up and down more and cut less into the waves, which displaces less water, whcih is presumably good to the extent that you are not jumping up and down too much and splashing and wasting more energy this way over a heavier boat... So there might be a middle ground, depending on conditions...

Who knows... Perhaps one can next time they go out fill-up a couple of galons of water and place in the cockpit, time their upwind run, then toss the water out and time again? Repeat a few dozen times to get an average and report here? I don't think many would waste the time to try it diligently and if done otherwise any results will be pretty meaningness...

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9 years 9 months ago #15506 by AndyN
Replied by AndyN on topic Re: Upwind is a Heavy or Light boat best?
I was told many years ago that the reason for the minimum weight in K1's was to prevent the use of "disposable possibly unsafe craft" 8kg is pretty bloody light particularly if said boat has a pump fitted which marathon K1's will have! Bear in mind that it's 12kg for sprint boats and that does not seem to slow them down too much.
I've had more than a few k1's and personally I choose to go for a stronger construction that weighs around 10kg and don't notice a performance deficit. Slightly off topic I know. :-)

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9 years 9 months ago #15509 by kayakchampeen
I'd like to clarify my previous comments by saying that I never disparaged surfski pros or surfski paddlers in general at all, many of whom are most certainly insightful and inquisitive re. technique and equipment. Just meant to suggest that success racing at a high level isn't always predicated on anything more than good genes, hard work, and skill. The first guys to use aero bars in a cycling time trial or wing paddles in sprint were probably laughed at for incorporating novel equipment and techniques into their regimen. Now we cannot imagine a world without. Hell, the top tour de france guys used to smoke cigarettes, would it therefore follow that cigarettes made them faster? Sometimes people are fast despite what they do, not because of it. I only took issue with this approach to answering the question, not the answer itself, which I would suggest is that lighter boats are indeed faster at all points of sail, but ultralight, stiff boats may not be as subjectively comfortable upwind and beam-wind, and may be more difficult to manage. So please don't consider my post to be a recrimination of Dicko. He is as entitled to his assumptions as I am to mine. I just felt that it wasn't entirely on point per the OP's query. Thus is the give and take of a forum discussion.

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9 years 9 months ago #15514 by Love2ski
I think my 10.5 kg boat exposes flaws in my technique when paddling upwind due to the greater instability. A lighter boat not only sits higher out of the water than a glass boat, but also flexes less meaning the midsection sits higher again. This means the boat is narrower as it sits in the water due to the curve of the hull.

I read somewhere the deflection difference can be as much as 4 cm.

For these reasons a carbon boat is also a narrow boat as it sits in the water. The pros have the technique and core to handle this whereas I don't.
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9 years 9 months ago - 9 years 9 months ago #15522 by nell
I was in a race last year in my V12 ultra. The first leg was about 1.5 miles into front quartering 1 - 2 ft wind chop. After 1/2 mile, I was rapidly gaining on the paddlers in front of me. I glanced down and noticed that my cockpit was full to the brim with water as I'd forgotten to open the venturi. I opened the venturi and it emptied and I was now 30? lbs lighter. Over the next mile, I noticed that I was not catching and passing the paddlers in front of me any longer and that my ski was porpoising up and down much more even though my ski felt lighter and quicker.

What I gleaned from this is that while the lighter ski should have been faster according to lower drag and better acceleration, its lower momentum and more porpoise-ing movements gave it sort of a braking effect and continually killed its speed, whereas the heavier and straighter running ski was able to keep better momentum even though it took a bit more energy to keep it going. Mind you, the difference was minimal, maybe 0.1 or 0.15 mph, but noticeable.

All skis might not act the same way, though. I suspect a ski with a more knife-like bow will be affected less by porpoising movements and a ski with a fatter nose will be affected more.

Also, along the same lines, I remember reading a paper that compared rowing shell weights with speeds. Turned out that lighter was faster only down to a point. Too light a shell was slower (www.atm.ox.ac.uk/rowing/physics/weight.html) See 9. I suspect going upwind in small wind waves does much the same thing.
Last edit: 9 years 9 months ago by nell.
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9 years 9 months ago #15525 by sAsLEX

nell wrote: I noticed that I was not catching and passing the paddlers in front of me any longer and that my ski was porpoising up and down much more even though my ski felt lighter and quicker.

All skis might not act the same way, though. I suspect a ski with a more knife-like bow will be affected less by porpoising movements and a ski with a fatter nose will be affected more.




Displacing more water going through waves rather than floating on top can be quicker!

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9 years 9 months ago #15527 by Sandy
Bourbon Orca 3180 tons , Skandi Caledonia 4100 tons . ;)

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9 years 9 months ago #15528 by Marieski
I'm really enjoying this discussion. Something everyone of every level can contribute to.

Past skis: Spirit PRS, EpicV10Sport Performance, Epic V10 Elite, Stellar SES Advantage. Current skis: Fenn Elite Spark, Fenn Swordfish vacuum. Custom Horizon, Epic V7

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9 years 9 months ago #15529 by duncangroenewald
In general lighter boats will go faster, if everything else is equal and assuming the design envelope of the boat has not been exceeded. Yes too light can be bad, but not as bad as too heavy.

Consider "nell" above with his V12 - its possible that the additional weight of water made the V12 more stable and allowed him to apply more power to his stroke. Its also true that the excessive porpoising with an empty boat may have slowed him down more. Especially as he most likely accelerated from the start with an empty (light boat) so paid no weight penalty then.

My experience is similar with a V12, I weight around 78kg and think I am too light to sit this boat properly in the water. Also it seems to have lots of volume up front so goes over most chop and bashes down quite hard.

I now paddle a Flow Kayaks SharpSki 6.5 which seems much more suited to my weight, has a narrower bow and slices through the chop much better than the V12 did with me in it. The seat is also a much better fit and I feel 'connected' to the ski. As a consequence the boat does what my hips want it to do, not what the chop wants it to do, I feel more stable and can apply more power with less effort - as a result I seem to go faster upwind. Of course this is rather subjective but it certainly makes me feel happier. Both boats weigh virtually the same - 13.5kg with leashes and other bits attached. Of course I would prefer a 8kg boat with the same shape, stiffness because acceleration would be quicker etc.. bearing in mind that 1kg represents just a bit more than 1 percentage point more weight. So shaving off 5.5kg is bound to make a big difference to acceleration but not much to punching through/porpoising over the waves because the hull is already very narrow with relatively low bow volume and the weight coming off will be evenly distributed, unlike the water in the cockpit that is relatively forward in the boat.

Flat water I would say the V12 is a fraction quicker, like maybe 12.5kph average over 10km, vs 12.4km in the SharpSki. Not sufficiently different to really attribute just to the boat though.

just my 2 cents worth...

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9 years 9 months ago #15540 by Kocho
It's not "displacing more water makes you faster". The key to the bulbous nose is that it minimizes the effect of the bow wave and in this application also minimizes excessive up-down motion. All of this combined gives you *less* water being displaced and splashed around, not more. And the water that is being displaced, is displaced in such ways as to minimize the effect on the full.

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9 years 9 months ago #15555 by Dicko
As I slogged 5km into a head wind this morning I was wondering if there was a greater effect from boat weight the lighter your weight.

When I sit in my 15.5kg glass boat my total mass is around 110-115kg. A 4kg saving in boat weight is around 3 and a bit % (my kingdom for a calculator) of the total weight. This is a fair bit less mass to accelerate with every pull on the paddle.

If you only weigh 70kg that 4 kg saving in weight is probably getting closer to a 5% saving in total mass. So I figure the more you weigh the less critical the weight of the boat is. There is still a benefit but not as much.

Assuming that power to weight ratio is as important in paddling as it is in most other sports and assuming that a bigger paddler is probably stronger than a smaller paddler the difference is probably even less critical.

Not withstanding the effects of stability, boat, technique, paddle, weather, wave shape, wind strength etc, etc. it is probably a much bigger advantage for a lighter paddler to have a light boat with reduced volume and windage than a big guy.

The end

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9 years 9 months ago #15559 by [email protected]
Just to add an anecdote, earlier this season we had a fairly extreme race from Fish Hoek out to the Roman Rock lighthouse and back... It was only about 12km including the side-one leg around the corner of the bay, but we did have a 25-30kt southeaster blowing.

So we had a major head-bang out to the lighthouse and then a superb 5km downwind back to Fish Hoek.

I was on a heavy Evo II (somewhere around 18kg). I found that I was able to grind away into wind, when some of the other guys seemed to be affected far more, being flung sideways as they ramped over the oncoming waves.

At the lighthouse, thinking I knew the ground far better than most, I cut the corner too sharply and was dumped out of the boat by a breaker. I had to swim it past the rocks before I could get back in, by which time the mob that I'd been with had pushed out way in front.

One of them was on a very light Nelo; another on a light V10. Once I got going again, I overtook the Nelo and V10 and caught up with the (female!) Fenn Elite on the beach.

Of course this could all be due my stunning rough water skills, but I rather think the stability and perhaps the weight of the boat helped. (I'm hopefully getting a light Evo II to test in the near future...)

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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9 years 9 months ago #15560 by PaddleFaster
I think that it all subjective, according to the strengths and weaknesses of the individual paddling.

Those with rock solid balance and a strong, quick stroke will probably, for the most part, be fastest in the lightest boat.

Those that are not near pro level strong paddlers, have possibly a slower cadence and possibly weaker balance skills, will probably be faster in the slightly heavier, slightly more stable boat.

In other words, I do not feel that there is an absolute, definitive answer, to the question. A beginning to low level intermediate paddler may achieve their fastest upwind times in one layup, and a higher level, intermediate to pro paddler, in another.

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9 years 9 months ago #15561 by Sandy
My guess is that hull shape and overall volume play a way bigger roll in the equation the actually boat weight. Take a 25 pound ski , put a 185 pound paddler in it then put a 150 pound paddler in it , two different effects and the hydrodynamics of the hull change with the change in waterline . Look at the video of the North Sea tender ships , very different hull shapes , not to mention power plants and who knows what cargo was on either one ? Way to many variables to call it on weight alone. As for paddling surf skis into the wind....No mention yet of technique . Timing and weight shift make a huge difference paddling into the wind. The subjective ultimately seems to take the cake regarding surf ski paddling in conditions. (not discounting race results or times here) , just that hanging it all on ski weight ?

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9 years 9 months ago #15562 by Sandy
oops , you beat me to it paddle faster !

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9 years 9 months ago #15563 by PaddleFaster
No I didn't Sandy! My comment only came up first because the forum posts in alphabetical order.

Besides, I don't even know what I said anyway! :laugh:

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9 years 9 months ago #15568 by Pleuston
At speed, a heavier boat will maintain more momentum than a lighter boat; momentum = mass x velocity. The heavier boat will resist being pushed backwards by wind more than the lighter boat. So you maintain more hull speed between strokes with the heavier boat vs. the lighter boat which means that it takes less energy from each stroke to maintain a certain velocity against wind. The trade-off is that it will either take more energy per stroke to accelerate to speed at the same rate, or it will take a longer time/ more strokes to accelerate to speed with the heavier boat.

Racing pros push their boats to the max with each stroke. The real speed advantages come from expertly picking lines downwind, where lighter boats with quicker acceleration mean the difference between catching runs or not.

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9 years 9 months ago #15573 by slim white
The design has a lot to say. If a surfski is planned to have a certain water line,considering the weight of the rider were the more sailing efficient is done, lighter weight of the boat will not improve the stability or speed of the surfski,with the same weight of paddlers, but the contrary, could be harmful in theory, only in theory.....
Lighter surfskis in rough could easily run away if not secured and less stable in the rough too.
Lighter skis start moving easily the first two meters later on the heavier ski maintain the cruise speed by its inertia.
On sea I prefer heavy boats, on flat water races lightest as possible ones.

When you get what you want you don´t want what you get

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9 years 9 months ago #15585 by Love2ski
Had some solid upwind slogs in Sydney today. I found my carbon xt was faster upwind than my friend on an 18 kg xt. My friend is a better paddler than me on the flat.

Provided I could keep the hammer on I was jumping ahead into the chop. Its all about technique.

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8 years 10 months ago #19624 by photofr
Having tried many different boats, I can only attest to my personal findings.
A lighter surfski will always be faster upwind - but…
Said ski must ALSO:
Be designed for my weight (120 pounds).
Mustn't have too much volume out of the water so as to not act like a sail.

Ludovic
(Brittany, France)

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