There has been much debate about the attempting of sailing records in very
shallow water. The controversy has only recently come to light because up
until now the need for skegs on windsurfers made water depth self-limiting.
However the high speeds being claimed by kite surfers has circumvented this
as although they need to "edge" their boards somewhat to generate lift, at
50 knots and at deep wind angles, the edge doesn't run very deep. There was
a real concern that unless some sensible ruling was brought in, a world
record claim using water only as a lubricant was a possibility. For example,
creating a record course by covering a large car park with a plastic sheet
and then wetting it to a few mm depth. There was a general feeling that this
stretched the aim of breaking records on "water" too far.
* The new rule states that "Record claims will not be ratified when, in the
opinion of the WSSR Commissioner, the minimum water depth over the whole
course is below 50 cms"
don't know much about it but I'd suggest that too shallow water will actually have a negative effect on the maximum speed attainable due to drag ?
Also agree though, that all records attempts should be under ratified conditions with appropriate measuring instruments to be held valid.
hey rick im no scientist ethier but i would say that as long as you are not hitting the bottom shallow water will go faster. i remember reading about some effect where the shallower water (under a certain depth) actually compressses less than deeper water, so in theory you are pushing the water less and intead just gliding over the top of it which involves less friction so you could go faster. much like ground effect in aeroplanes.
Yeah it's basically ground effect, but with water as the compression medium instead of air. essentially the water cannot be dispersed laterally fast enough as the board travels overhead, creating a moving area of high pressure directly underneath. this means that effectively the water directly under the board is "more dense" (yes i know water cannot be compressed but it's a good description of what happens) and therefore the board rides higher, with less subsequent displacement (drag)
same reason this thing flew over water so well: en.wikipedia.org/wiki/Ekranoplan
Shallow water is also really smooth. Watch some footage of speed kiters at the end of their run as they hit the chop in deeper water and start to skip out. But Rowdy's on it, the beef here seems to be about "shallow water drag reducing effect".
I did a bit of digging, here's the rule change at the World Speed Sailing Record Council (WSSR)
www.sailspeedrecords.com/content/view/88/3/
"There is much anecdotal evidence about the positive effects on speed by the shallow water effect and certain published study including the effect on fast ferries when entering shallow water and using the effect to "unstick" seaplanes. However in order to obtain some hard data, the Council commissioned the Wolfson Unit of Southampton to prepare a paper on the specific subject.
Their conclusion of this detailed study was that the drag of a planing board is reduced when the water depth is less than the beam of the board, with a possible reduction of 50% in very shallow water of less than half the beam of the board. A water depth of 50cm would be deep enough to avoid shallow water effects.
It was agreed by Council that to introduce a ruling which would require the width of a board to be measured in order to establish the water depth would be impracticable and thus an overall 50cms depth has been introduced, as follows:
"Record claims will not be ratified when, in the opinion of the WSSR Commissioner, the minimum water depth over the whole course is below 50 cms"
It is believed that this depth of water negates the "shallow water drag reducing effect" but does not disadvantage the usage of existing courses that are protected and relatively free from current and waves."
It smells to me like they are just shifting the goalposts so that mega millionaire yachties stand a chance of taking the record from windsurfers who have dug a canal in some French beach, and no kiter with a cheap 9m Bow kite (a Caution Answer is tillmann's choice) and a homemade board can claim 50 knots.
