Forums > Windsurfing   Gps and Speed talk

Dead Water effect

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Created by Spotty > 9 months ago, 5 Jul 2015
Spotty
VIC, 1619 posts
5 Jul 2015 9:54AM
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Thought this may be of interest for discussion re sailing inlets etc where fresh and salt water combine or are at one extreme or the other... is it a factor after storm surge, heavy run off... or a minimal impact as long as it's blowing it's ring off and the water is flat.

I think we all have days at Sandy Point where we all hit a wall on certain days, maybe it's just another component amongst the many we manage or go up against where we don't go as fast as we expect on average.

Spocktek
WA, 281 posts
5 Jul 2015 10:03AM
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hmmmm, interesting Spotty. I went for a fang on a salt lake once, waterstarting was easy.

barney831
110 posts
5 Jul 2015 10:49AM
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This effect can be important for displacement hulls but is of little relevance for high speed planning boards.

yoyo
WA, 1646 posts
5 Jul 2015 6:27PM
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Based on what.... I am sure wave making resistance is part of the equation in speed. But just how much on a speed board we will probably never know. Interesting video.

AUS4
NSW, 1249 posts
6 Jul 2015 12:48PM
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You are always going to go faster in salt water because you float higher, have you ever noticed its easier to swim in the ocean than in a fresh water pool.

mathew
QLD, 2019 posts
9 Jul 2015 2:36AM
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Select to expand quote
barney831 said..
This effect can be important for displacement hulls but is of little relevance for high speed planning boards.




yeah... because when the water moves in the opposite direction to the wind, planing boards dont benefit from the added lift. <sarcasm>


sailquik
VIC, 6068 posts
10 Jul 2015 10:51PM
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That is why we wait until the fresh water has evaporated off the top at LG!

andysails
SA, 79 posts
14 Jul 2015 8:09AM
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Fresh water is less dense than salt-water, that's why it sits on top. Less dense could allow greater speed due to less resistance!

sailquik
VIC, 6068 posts
29 Jul 2015 10:56PM
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But denser water allows the use of a much smaller fin and board.

The big question? Which is better for best speeds?

From the evidence so far, I suggest that the denser water has the edge.

boardboy
QLD, 554 posts
13 Aug 2015 5:33PM
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best results are achieved by starting in salt water with small board and fin and then sail into fresh water when up to speed. obviously.



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Forums > Windsurfing   Gps and Speed talk


"Dead Water effect" started by Spotty