Speed Sailing Gets A Shot of Sanity

Interesting:
MINIMUM DEPTH NOW FOR SPEED RECORDS
by John Reed, World Sailing Speed Record Council
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. -- For comments
and complete report:
http://forum.sailingscuttlebutt.com/cgi-bin/gforum.cgi?post=5989#5989

* 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" --
http://www.sailspeedrecords.com/content/view/88/3/

 

Man, I was just on my way to Walmart to do that, now my Saturday is ruined

 

From scuttlebut:
"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. "

So what is the effective beam of a kiteboard when it is being edged? Does the test case they reviewed actually reflect what happens with kiting? It sounds like the test involved a flat planing surface instead of a kiteboard being edged. There isn't enough info here for me not to think of this as yachting fraternity protectionism.

Hardly a shot of sanity. What is the WSSR Commissioner going to do - walk the entire course before every day's runs?

 

Just don't wipe-out!
50 knots on the pavement? that would hurt.

 

Isn't this a little harsh? How many of your "yachting fraternity" associates can do 50 kts in knee-deep water? Or are you referring to the windsurfer crowd, when you speak of protectionism? You have a short memory; windsurfers weren't allowed into the "yachting fraternity" until a very few years ago--most yacht clubs still don't allow windsurfers as members.

As the the efficacy of the restriction--it's long been known that shallow water makes boats and boards faster. It isn't the "yachting fraternity's" responsibility to prove that kiteboards are similar to other planing hulls (though it's rather obvious to many of us). Rather, it's the kitesurfers' responsibility to prove they *aren't.* If you'd like to start a research program to this end, I'd be pleased to support you--to assist if possible.

Cheers,

Dave

 

Dave - kiteboards are obviously plane and therefore are "similar" to planing hulls but test described indicates that they tested a flat planing board only. Kiteboards do not just plane as a flat board so I'm not convinced that the test results are valid.

Who's responsibility it is to prove there is any speed enhancing effect - I don't know. How have other rule interpretations been done in the past? I would have thought that a fair guiding principal would be that if you were to ban a particular configuration that it should be done based on solid, relevant information. At least some research was done but was it the right research?

I'm interested in your comment about it long being known that shallow water makes boats and boards faster. Can you point me at some sources? I understand that speed records have been set in shallow water close to shore but had always understood that this was to ensure flat water, not shallow water.

I probably don't have a strong enough personal interest in starting a research program. Thanks for the offer of help though. I wonder if a CFD calculation could cast some light on effect without needing anyone to skid down a plastic tarp in a car park at 10 different water depths...

I don't think I understand your comments re yacthing fraternity associates and windsurfers so I won't comment there but please rest assured that as a kiter, sailboarder, dinghy sailor and offshore sailor I don't consider myself unfairly biased against any of these windsport enthusiasts.

 

Dispacement boats are actually slower in shallow water than in deep water.

 

From WSSRC this morning:

WSSR Newsletter No 156 05/07/08

The WSSRC's new rule on minimum water depth for speed record attempts has
seemingly caused a great deal of excitement among the kite sailing
community with strong opinions being expressed both for and against. Some
people have sent several pages of requests for technical explanations of
the most detailed kind while others have demanded that the new rule be
cancelled or delayed. We really cannot be expected to give a detailed reply
to hundreds of questions so the following is an attempt to give a general
explanation of the new rule and what led to it.

Every individual record attempt or observed speed event generates a report
from the supervising WSSRC Observer. Last year it became clear from these
that kite sailors were sometimes running in very shallow water - for
instance in the lee of a mud-bank or sand-bar. Their objective was to find
water as smooth as possible but it also rang alarm bells with members of
WSSRC who wondered if there was some other benefit of running in shallow
water which could give an unfair advantage to a particular type of craft.

The alarm bells began to ring more loudly last year when German newspapers
reported that a kite sailor had exceeded 50 knots. It turned out that this
'claim' was neither observed nor measured in any acceptable way and was
therefore rejected by virtually all reasonable sailors but certainly caused
a good deal of confusion at the time. It was reported that this run had
been made over mud-flats covered by a thin film of water and raised the
questions:

- is this fair?
- is it sailing?
- does it have wider implications for future record attempts?

As the body responsible for ratifying records, WSSRC felt it must
investigate.

One WSSRC member pointed to the game of 'skim-boarding' in which a flat
board is thrown down onto very shallow water followed by a rider who runs
and jumps onto it. If you do it right, the board skims along for many
metres with apparently very small resistance. This proves the existence of
some kind of 'ground effect' in which the water acts as lubricant rather
than support. Most of us have scared ourselves at some time by driving
into water on the highway when the tyres unexpectedly 'aquaplane' and lose
all contact with the road. This also shows how a very thin film of water
can act as lubricant.

The questions that arise are:
- how significant is the effect?
- how shallow must the water be to create this effect?

The Council therefore decided to consult the Wolfson Unit of Southampton
University to see if they could come up with some hard evidence. They did -
and the results are really surprising. When investigating the performance
of seaplanes, a full programme of tank tests had been done years ago by
NACA in the United States and the Wolfson team extracted and analysed the
relevant data, also adding their own knowledge gained from tests on fast
ferries and the science of sailing in general. To greatly simplify these
results, they show that a planing surface experiences progressively lower
resistance in water depths less than about 50cms. When the water is
shallower than the width (beam) of the planing surface, the reduction of
drag can be dramatic and in the extreme case when the water depth is less
than half the beam of the board, the drag reduction can be as much as 50%.
This clearly explains the performance of the wide, flat, skim-board running
in a few centimetres of water.

Going back to the earlier questions -

- Is this fair? WSSRC thinks not because it is an advantage only
open to a very specific craft; one that is effectively flat-bottomed and
can be sailed at very deep wind angles without needing a skeg, board,
hydrofoil or other device that counters leeway.

- Is it sailing? We do not believe that the public could possibly
accept running in 10cm of water as a World Sailing Speed Record and neither
would it accept that only kite-boards could hold the record in future.

- Are there wider implications for the future? Yes. Once it is
generally understood that there is a big advantage to be had from running
in shallow water, there will surely be efforts to create a perfect
artificial course (just as the windsurfers created the 'trench' course in
the past). This could be a flat piece of ground such as a car-park on which
is laid plastic sheeting to contain the necessary few centimetres of water.
And what is meant by 'water'? Must we analyse it to ensure that polymers
such as soap solution have not been added to lower resistance further? The
safety of competitors is not the responsibility of WSSRC but even so it
might not be advisable to recognize a 'sport' in which there is real risk
of falling onto concrete at 50 knots. So far, the ISAF has not played any
part in these discussions but if they found out that WSSRC was intending to
ratify a World Record under such circumstances, they would surely be
horrified.

Three more points need to be made.

It is not possible for an Observer to carry out a complete and accurate
survey of the area in which record attempts will be run. In practice he
will use all means at his disposal to check that in general the water is at
least 50cm deep. There could easily be stones, bumps or sand ripples
standing higher and these will surely not affect the speed.

This new rule is nothing to do with measuring speed by hand-held GPS, which
is a completely different discussion.

The intention of the new rule is to ensure that a wide variety of craft
have a fair chance of establishing records. With the 50 knot record
currently under attack by multihulls, hydrofoils, planing craft,
windsurfers and kiteboards, it is particularly important that all should
have the same opportunity of success. Nothing prevents kite-surfers from
finding or creating a course where the water is 50cms in depth very close
to the shore.


John Reed
Secretary to the WSSR Council

 

I can appreciate this, Munter, but just who *do* you believe has the responsibilty to determine that your specific case is sufficiently "different" to warrant some different rule? WSSRC spent some significant time--and cash--before making this determination. What set me off was *you* were the one claiming "yachting fraternity" collusion, despite their stated reasons, specific research and considered opinion.

There have been many, er, enhanced attempts at speedsailing in the past. Slime has been tried; dropping off hulls has been tried, all manner of "cooking" timing systems have been tried. As you might imagine, there is considerable commercial value in breaking world records--well beyond the personal rush. As is (I believe) appropriate, the WSSRC have pretty much always put the onus on the competitor to prove an "unusual" system is fair to all. Frankly, your original response smacks distinctly of the current fad for "entitlement", wherein the competitor (student/voter/citizen) is somehow "entitled" to run whatever they want, in whatever conditions they want, and somehow it's the organizers' responsibility to conclusively prove unfair advantage (never call it cheating). The world just doesn't work that way.

Let's be completely transparent, shall we? What *disadvantage* would such a minimum water depth place on any competitor, using any boat type, and why is such disadvantage--equally applied to all, "unfair" to some?

Cheers,

 

Yep, if you didn't believe there was a big advantage in running in very shallow water just because its very shallow you wouldn't be whinging so much. And so if water depth is to be considered irrelevant, that's great. Reducio ad absurdiam and all that. I'll set up a craft to run in a miilimetre of water on a frozen lake - actually, no better than that, how about running on the 25 micron or whatever film of water between the runners of the ice boat and the ice? 50 knot barrier? No worries...

 

If nothing else, when you biff it and eat **** when kiteboarding, you can really eat ****. 18" makes a reasonable pad , better than a shell-strewn mudflat at 50mph or damn close to it. To answer a question upthread, I was just out kiteboarding the other day; I can say with confidence that the board (when leaning hard) is immersed at about a 45 degree angle, maybe as much as 60 at times. Board depth I would say would be about six inches to the lowest point, on a true elliptical board ("Bubbles"), two layers of 1/4" birch underlayment with a 3/4" core of hobby foam and fiberglassed on the bottom.
But remember that the board is under those conditions, creating a supercavitation effect. I can clearly feel air and water spray being sucked past my lower legs into the air pocket above the board. I can see how very shallow water would give a "tip plate" effect to this (fairly inefficient) foil shape, and giving it greater-perhaps even much greater- efficiency and lift to windward.

Never really thought about it that way. I think that if somebody got busy with a fluid-modeling program, it would at least be apparent on whether the potential for this phenomenon to exist at all; and if it does, and it feels right to me, then it should be possible to get a quantitative gain, yes?

I haven't done a whole lot of masted sailing-- a disastrous episode on a Hobie most recently-- but from what I remember of that and how the kite behaves, there are an awful lot of parallels and corrolaries (and coronaries LOL) between the two ways of doing it. It's the difference between karate and judo--they're very similar, with a similar praxis, but different in their own ways.

Kites are coming, guys. Time to think, maybe about powering with them... I hope to see within a year or so whether or not a dinghy could use a kite effectively. I bet one might work just dandy in an Atkin Seabright, about 20' long....

 

When travelling in my flat bottomed, outboard powered net boat at speed I will often pass over sandbars where the water is just deep enough for the outboard leg. With the throttle in a fixed position the punts acceleration as it hits the shallows is very noticeable, enough to make me lose by balance a bit when I'm standing.

 

Maybe we need an unlimited category (anything goes so long as the hull doesn't actually touch the bottom including sailing along a moist ditch) to allow the extremists a measure of participation and recognition. The water not allowed to be frozen, of course.

The 'sailing craft" used for sailing speed records are one-way specialised boats intended for a specific and highly atypical water course. Maybe there is a need for a real sailing category, say on a triangular course. That is, unless it already exists.

The problem with speed for its own sake is that, unlike racing, much of the research doesn't seem to translate into performance improvements for the everyday joe. Takes all kinds ...

 

I for one would love to see point-to point racing for some of the more extreme designs. Not every boat could compete for the Transatlantic trophy but I bet with a little thinking, some of the shorter races are quite possible. Chicago to Macinac, for example. Let's see if it can be done in 12 hours or less....

 

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Not Hydroptere-she can sail any direction any other sailboat can.