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Forums > Windsurfing General

Well done Bjorn, World Champion

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Created by choco > 9 months ago, 14 Aug 2011
choco
SA, 4098 posts
14 Aug 2011 9:05AM
Thumbs Up

from PWA site;

Bjorn Dunkerbeck:
“It has been a very successful year for me, my Starboards and my Severne Reflexes have been going really fast. We have been working for three years on a sail that can win competitions, and so far I won four firsts and a second so it's mission accomplished. With one competition to go I am the world champion, it's been a while. This is my fourth sail maker, I won my first title in 1988 with F2, I won lots with NeilPryde, then a couple with North and this is my first victory with Severne sails so that makes me really happy.

This guys a real legend

Haircut
QLD, 6483 posts
14 Aug 2011 9:51AM
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orsm

antoine looks like a monster when you see them all standing together

SWS
SA, 196 posts
14 Aug 2011 9:21AM
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Most likely

choco
SA, 4098 posts
14 Aug 2011 9:32AM
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Still find it amazing that these bigger guys are still faster in lighter winds than the light weight sailors, ok they might take a bigger board and sail but someone lighter on smaller kit should be faster.

terminal
1421 posts
14 Aug 2011 8:18AM
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If you're good enough, you're young enough.

SWS
SA, 196 posts
14 Aug 2011 9:52AM
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choco said...

Still find it amazing that these bigger guys are still faster in lighter winds than the light weight sailors, ok they might take a bigger board and sail but someone lighter on smaller kit should be faster.


They can hold a bigger sail down in a more stable position thus taking advantage of the gusts.

seanhogan
QLD, 3424 posts
14 Aug 2011 10:45AM
Thumbs Up



Go Bjorn !!!!!!!

a legend !!!!!!!!!!

Ian K
WA, 4122 posts
14 Aug 2011 10:33AM
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SWS said...

choco said...

Still find it amazing that these bigger guys are still faster in lighter winds than the light weight sailors, ok they might take a bigger board and sail but someone lighter on smaller kit should be faster.


They can hold a bigger sail down in a more stable position thus taking advantage of the gusts.


A lot of things going on but I've had a go at a dimensional analysis.

Parasitic drag of the rider goes up with the cross sectional area or the square of rider dimension. Righting moment of the rider goes up with the fourth power of rider dimension. (The weight has gone up with the cube of dimension and the arms are longer to get further outboard).

The counteracting moment of the sail goes up with the area and height of the centre of lift above the deck. ie the sail dimension cubed.

So, balancing moments, we have the cube of the sail dimension going up with the 4th power of rider dimension. Call this equation 1.

The force generated by the sail is proportional to the sail area or the square of the sail dimension.

So taking the 2/3 root of both sides of equation 1. we have sail power going up with the rider's dimension (height) to the power of 2.7 . And the sailor's parasitic drag only goes up with the sailors "height" to the power of 2. So the lift to parasitic drag ratio gets better as the rider gets larger.

What do you reckon? Pretty sure it's a valid analysis. I've thought though it a few times.

A lot of other things going on though. Chunky riders vs. lean riders? signals from the brain to the feet of tall riders? Chop at the short end of the spectrum can be ignored by large riders.



elmo
WA, 8779 posts
14 Aug 2011 3:13PM
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Respect

jp747
1553 posts
15 Aug 2011 12:26AM
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finally! been waiting for such a long time..congrats to him

Willaus0001
QLD, 333 posts
15 Aug 2011 9:29AM
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hahaha I feel sorry for the guys who havent got to the top yet and have to beat Antoine and Bjoern to get there! Bjoern only has about 10,000 world titles in the pool room already hahaha!

da vecta
QLD, 2514 posts
15 Aug 2011 10:36AM
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elmo said...

Respect


Yes, I second that.

da vecta
QLD, 2514 posts
15 Aug 2011 10:37AM
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Haircut said...

orsm

antoine looks like a monster when you see them all standing together


That's not a real lighthouse he's holding!

Chris 249
NSW, 3434 posts
15 Aug 2011 11:06AM
Thumbs Up

Ian K said...

SWS said...

choco said...

Still find it amazing that these bigger guys are still faster in lighter winds than the light weight sailors, ok they might take a bigger board and sail but someone lighter on smaller kit should be faster.


They can hold a bigger sail down in a more stable position thus taking advantage of the gusts.


A lot of things going on but I've had a go at a dimensional analysis.

Parasitic drag of the rider goes up with the cross sectional area or the square of rider dimension. Righting moment of the rider goes up with the fourth power of rider dimension. (The weight has gone up with the cube of dimension and the arms are longer to get further outboard).

The counteracting moment of the sail goes up with the area and height of the centre of lift above the deck. ie the sail dimension cubed.

So, balancing moments, we have the cube of the sail dimension going up with the 4th power of rider dimension. Call this equation 1.

The force generated by the sail is proportional to the sail area or the square of the sail dimension.

So taking the 2/3 root of both sides of equation 1. we have sail power going up with the rider's dimension (height) to the power of 2.7 . And the sailor's parasitic drag only goes up with the sailors "height" to the power of 2. So the lift to parasitic drag ratio gets better as the rider gets larger.

What do you reckon? Pretty sure it's a valid analysis. I've thought though it a few times.

A lot of other things going on though. Chunky riders vs. lean riders? signals from the brain to the feet of tall riders? Chop at the short end of the spectrum can be ignored by large riders.






Good post.

Also, induced drag is inversely proportional to the length of the leading edge of a foil, so induced drag drops as rig height and fin depth increases. If the big guys can carry taller masts and deeper foils they get another benefit.

I've checked the speed of brain-to-limb signals, and there's basically no difference because the speed of the signals is so quick.

Of course, as soon as you move off FW/slalom/speed gear and into the more popular racing formats (hybrids and longboards are something like 150% as popular worldwide) and you start racing in light winds with restricted sail size, lighter sailors get a very good chance and medium weight sailors may dominate.

oldie
VIC, 356 posts
15 Aug 2011 12:31PM
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Bottom line of any deep analysis is the wisdom of early unlimited everything car racing-
"A good big one will always beat a good little one."
The reason for this phenomemem is that as rider and kit grow bigger, kilometers remain the same size . Einenstein thought deeply about this effect when developing his theories, I believe.

oldie
VIC, 356 posts
15 Aug 2011 12:33PM
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So a windsurfing ant will always be back of the pack....

yoyo
WA, 1646 posts
15 Aug 2011 11:26AM
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Ian, they have a bigger advantage than that. Have a look at some graphs for drag on cylindical sections at reynolds numbers around 200K. Then work out the Reynolds No.s of Finian's etc thighs at speed compared to your own and see which side of the slope you are on... :-)

Chris 249
NSW, 3434 posts
15 Aug 2011 1:38PM
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Small to medium size windsurfers can be very competitive. The male RSX sailors average around 74kg (using the figures I can find on the net) with highly competitive women around the 55-60kg mark (guessing at Jessica's weight).

Sure, in FW, slalom and speed bigger may be better. But while they are great disciplines, they are NOT all of windsurfing and in fact there are more people racing longboards and hybrids than racing FW and slalom. And I think there's a very high chance that there are more full-time sailors in the Olympic class than in FW.

So without knocking FW and slalom in any way, you can't just say what works in them works for all of the sport, or even all of racing.


Ian K
WA, 4122 posts
15 Aug 2011 12:59PM
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yoyo said...

Ian, they have a bigger advantage than that. Have a look at some graphs for drag on cylindical sections at reynolds numbers around 200K. Then work out the Reynolds No.s of Finian's etc thighs at speed compared to your own and see which side of the slope you are on... :-)


Don't Reynolds numbers often have to change a fair bit to get into another flow category?

And we've left out board drag, which to a first estimate goes up with weight of the rider or his/her dimension cubed. So far I've got sail force going up to the power of 2.7, parasitic drag of the rider only going up to the power of 2 but hull drag going up by a whopping power of 3. Plus all the other factors mentioned. It's getting complicated.

That power of 3 suggests hull drag might eventually catch up with large riders? Is there an optimum weight or is it always bigger is better?

One of the restrictions of windsurfers, compared to craft with trapezes and wings, is that we are limited in how far out we can get the ballast. Light riders with very long arms might equate favourably.


Aus06
SA, 235 posts
15 Aug 2011 6:13PM
Thumbs Up

Well done Bjorn - nice to have that familiar feeling back again I'm sure.

Well done also to Starboard - a great achievement for their outstanding iSonics.

And a big congrats to Ben Severne - Adelaide boy who has gone on to design sails that can achieve multiple event wins and world championship wins.


Wet Willy
TAS, 2317 posts
15 Aug 2011 7:38PM
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da vecta said...

elmo said...

Respect


Yes, I second that.


I third it.

Mr. No-one
WA, 921 posts
15 Aug 2011 6:29PM
Thumbs Up

da vecta said...

Haircut said...

orsm

antoine looks like a monster when you see them all standing together


That's not a real lighthouse he's holding!


Looks like it takes batteries

Great effort to Dunks and the team at Serverne and Starboard.

slalomfreak
NSW, 304 posts
15 Aug 2011 9:12PM
Thumbs Up

Wet Willy said...

da vecta said...

elmo said...

Respect


Yes, I second that.


I third it.



Forth it!

Haircut
QLD, 6483 posts
15 Aug 2011 9:20PM
Thumbs Up

da vecta said...

Haircut said...

orsm

antoine looks like a monster when you see them all standing together


That's not a real lighthouse he's holding!


that's a lighthouse?.......I thought he'd won this

slalomfreak
NSW, 304 posts
15 Aug 2011 9:45PM
Thumbs Up

Ian K said...

SWS said...

choco said...

Still find it amazing that these bigger guys are still faster in lighter winds than the light weight sailors, ok they might take a bigger board and sail but someone lighter on smaller kit should be faster.


They can hold a bigger sail down in a more stable position thus taking advantage of the gusts.


A lot of things going on but I've had a go at a dimensional analysis.

Parasitic drag of the rider goes up with the cross sectional area or the square of rider dimension. Righting moment of the rider goes up with the fourth power of rider dimension. (The weight has gone up with the cube of dimension and the arms are longer to get further outboard).

The counteracting moment of the sail goes up with the area and height of the centre of lift above the deck. ie the sail dimension cubed.

So, balancing moments, we have the cube of the sail dimension going up with the 4th power of rider dimension. Call this equation 1.

The force generated by the sail is proportional to the sail area or the square of the sail dimension.

So taking the 2/3 root of both sides of equation 1. we have sail power going up with the rider's dimension (height) to the power of 2.7 . And the sailor's parasitic drag only goes up with the sailors "height" to the power of 2. So the lift to parasitic drag ratio gets better as the rider gets larger.

What do you reckon? Pretty sure it's a valid analysis. I've thought though it a few times.

A lot of other things going on though. Chunky riders vs. lean riders? signals from the brain to the feet of tall riders? Chop at the short end of the spectrum can be ignored by large riders.





Ian,
There are sooo many variables to take into account but ultimately I think the bigger sailor wins in light planing conditions because he can generate more power or lift and control the power, from the bigger gear he can handle.Lift from the board,sail and fin increases exponentially to the surface area, as you said.
Which means the big guys should win at Formula ?

SeanAUS120
QLD, 759 posts
15 Aug 2011 10:08PM
Thumbs Up

The thing is ......

We don't really do much lightwind racing in the PWA. I only used my big board (iSonic 127) in 2 races in Turkey this season and both times I was super overpowered on it. Costa Brava, which I skipped had 1 lightwind day but otherwise there were really no other light wind days this season.


Definitely in lighter winds the lighter sailors have a better chance at closing the gap but in places like Turkey where its flat water the big guys could carry massive sails (ie, using 7.8 in +30 knots) and would go double the speed of smaller guys on smaller sails. It's not really comparable looking at slalom vs Formula/RSX/Hybrids etc because they are all going upwind/downwind and more factors come in to play than just top speed.

Most of the racing we did this season on the PWA was in 20-30 knots whereby most sailors are on 7.8 and 110L boards. In these conditions being +100kg vs 80kg is a massive, massive advantage.

If you want to look at it more scientifically, look at it from a 'Sail Carrying Power' perspective.

SAIL CARRYING POWER =
Righting Moment / Distance between the centre of effort of the sail and the combined lateral resistance of the hull and fin.

Antoine or Bjorn at 100kg would have a sail carrying power of 20% more than someone like Steve Allen at 82kg.

If you have a copy of anything Bethwaite has written you can read more about that (though he also looks at total weight of the hull but slalom gear is so light compared to boats).

AUS4
NSW, 1277 posts
15 Aug 2011 11:12PM
Thumbs Up

Man up Sean.......put some lead in your pockets.

Rob11
240 posts
15 Aug 2011 9:30PM
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SeanAUS120 said...


Antoine or Bjorn at 100kg would have a sail carrying power of 20% more than someone like Steve Allen at 82kg.


How about the guys from 7th to 20th place in Alacati, not really the bulky guys and they manage to be upthere, top 10 quite regularly. Do they sail more in these conditions etc... what's their secret??

choco
SA, 4098 posts
15 Aug 2011 11:12PM
Thumbs Up

Magnus8
QLD, 365 posts
15 Aug 2011 11:45PM
Thumbs Up

SeanAUS120 said...

The thing is ......

We don't really do much lightwind racing in the PWA. I only used my big board (iSonic 127) in 2 races in Turkey this season and both times I was super overpowered on it. Costa Brava, which I skipped had 1 lightwind day but otherwise there were really no other light wind days this season.


Definitely in lighter winds the lighter sailors have a better chance at closing the gap but in places like Turkey where its flat water the big guys could carry massive sails (ie, using 7.8 in +30 knots) and would go double the speed of smaller guys on smaller sails. It's not really comparable looking at slalom vs Formula/RSX/Hybrids etc because they are all going upwind/downwind and more factors come in to play than just top speed.

Most of the racing we did this season on the PWA was in 20-30 knots whereby most sailors are on 7.8 and 110L boards. In these conditions being +100kg vs 80kg is a massive, massive advantage.

If you want to look at it more scientifically, look at it from a 'Sail Carrying Power' perspective.

SAIL CARRYING POWER =
Righting Moment / Distance between the centre of effort of the sail and the combined lateral resistance of the hull and fin.

Antoine or Bjorn at 100kg would have a sail carrying power of 20% more than someone like Steve Allen at 82kg.

If you have a copy of anything Bethwaite has written you can read more about that (though he also looks at total weight of the hull but slalom gear is so light compared to boats).


What about Tatty?

If you watch BD closely in his races, he sails some very good angles. A lot of other blokes spend to much time bearing up, then down before the gybe mark...he does the opposite.

But WTF would I know....

da vecta
QLD, 2514 posts
16 Aug 2011 11:01AM
Thumbs Up

At work I like to distance myself from the centre of effort. Does that mean I'm fast?



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"Well done Bjorn, World Champion" started by choco