Lüderitz Speed Challenge

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Created by

seanhogan > 9 months ago, 1 Nov 2012

Te Hau

495 posts

24 Nov 2012 2:42am

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Ian K said...
Yes the 58 kph in Dr Speed's diagram is less but not insignificant.

Putting in a few estimates, put in yours if you like, Cd for a person 1.0, cross sectional area presented to wind 0.5 sq metres, density of air 1.2 kg/m^3, 58 kph = 16 m/sec. Put those estimates in the drag equation ie. drag = 1/2 Cd A rho V squared and get drag = 76.8 newtons. (7.8 kg).

Looks like from Dr Speed's diagram only about Sin 45 of that is in direction of travel = 5.46 kg. The other 5.46 kg transverse to the direction of travel adds load to the fin, but the fin has a good lift to drag of say 20:1? 10:1 ?? (I've never been able to wind up a fin designer sufficiently for them to hazard a guess on this ) So maybe add 0.5 kg of extra fin drag to give 6 kg drag opposing the direction of travel. That's a fair bit, how much would streamlining reduce that by?

Cyclists reckon 58kph is real significant dragwise.

seanhogan

QLD

3424 posts

24 Nov 2012 8:13am

quote :
(A² talking about Bjorn's runs)

" I watched his first run, didn't take any risk and I would've done the same, but on the following runs I would've sheated in much more, especially with the wind at the moment".....

stringer

703 posts

24 Nov 2012 8:00am

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Te Hau said...

Ian K said...
Yes the 58 kph in Dr Speed's diagram is less but not insignificant.

Cyclists reckon 58kph is real significant dragwise.

Any excuse to take EPO and wear spandex[}:)]

Te Hau

495 posts

25 Nov 2012 4:38am

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Te Hau said...

Cyclists reckon 58kph is real significant dragwise.

Seems to me.....that human being standing next to the air flow entry area is a problem, 'bout as aero as a barn door.
Sail Rocket........, now that's aero.
Perhaps we need to work on getting the w/surf rider out of the drag story?

seanhogan

QLD

3424 posts

25 Nov 2012 2:53pm

A² speed clinic in Namibia :

"ok kids, one at a time !!!"

top bloke, he took the locals kids for a "quick" ride on his board, legend !!

seanhogan

QLD

3424 posts

25 Nov 2012 3:01pm

hardie

4129 posts

25 Nov 2012 9:32pm

Bjorn just did 50.9kt 500m in 30 to 35 kts of wind

seanhogan

QLD

3424 posts

26 Nov 2012 6:25am

51.09 for Bjorn

hardie

4129 posts

26 Nov 2012 6:39am

A2 100km 2sec 54kts www.gps-speedsurfing.com/default.aspx?mnu=user&val=111345&uid=412

stringer

703 posts

26 Nov 2012 12:20pm

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DarrylG said...
How about drafting. Cool to see 6 guys on the course at once.

or just one AA

seanhogan

QLD

3424 posts

26 Nov 2012 4:30pm

100.26 km/h on 2sec, removing half of the boom seems to work !!

seanhogan

QLD

3424 posts

26 Nov 2012 4:55pm

but it's still the tandem board

JonesySail

QLD

1120 posts

26 Nov 2012 5:38pm

These speeds are totally unreal!
The length of the harness lines really stands out as being extra long..really using their body weight as apposed to arm strength...
Does anyone have an idea what length lines A2 is using?

LeStef

ACT

514 posts

27 Nov 2012 12:02am

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JonesySail said...
Does anyone have an idea what length lines A2 is using?

Looks like he has put both on the starboard side !

sailquik

VIC

6166 posts

27 Nov 2012 12:06pm

New GPS World Record

Antoine Albeau has had his claim for the WGPSSRC record ratified.

WGPSSRC record is now 52.91 Knots (97.98 KMH)

www.gps-speedsurfing.com/default.aspx?mnu=forum&forum=1&val=43772

www.gps-speedsurfing.com/default.aspx?mnu=records

Posted session here:

www.gps-speedsurfing.com/default.aspx?mnu=user&val=111345&uid=412

Te Hau

495 posts

28 Nov 2012 3:52am

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JonesySail said...
These speeds are totally unreal!
The length of the harness lines really stands out as being extra long..really using their body weight as apposed to arm strength...
Does anyone have an idea what length lines A2 is using?

those long lines also get his body away from the air feed onto the sail, less blockage?

seanhogan

QLD

3424 posts

2 Dec 2012 6:14am

It's over,

Final results :

Antoine Albeau 52,05 noeuds

Anders Bringdal 51,45 noeuds

Jurjen Van Der Noord 51,26 noeuds

Bjorn Dunkerbeck 51,09 noeuds

Nick Vardalachos 50,56 noeuds

Patrik Diethelm 50,49 noeuds

Cedric Bordes 50,23 noeuds

End of posts

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