Marcus said "...as legitimate representatives of the vast majority of approximately 2000 potential record contenders as well as of the affected classes, we will be forced to install a new, independant speed record council, borne by the classes themselves"
Marcus on the windsurfing side there are only about a dozen windsurfers capable of giving the record a challenge. From what I have read most of those sailors actually favour the new rule.
Have you taken a poll of the members you claim to represent? On this forum there are more for the new rule than against, on GPS-SS it is the other way. Hardly a clear endorsement and in any case the commentators on these forums represent only a very small fraction of your claimed 2000 "members".
You are acting unilaterally without consultation , the very thing you criticise the WSSRC for, and when in fact they just did what they are supposed to do and in a measured way... identifying a potential problem....had a scientific investigation....when the results were in, had a discussion... made a decision.
They are the rule makers. They made a rule.
The only thing I can fault them for is that after finding out ground effect is related to beam they settled on a fixed depth of 50cm.
Macquarie Innovation could easily and safely sail in ground effect on a salt pond and be legal with this rule as it stands. And she is a definite 50 knot contender.
A good objective summary from my perspective Yoyo. As you say the, thoughts of the dozen or so in the 50 knot race should carry most weight. But spectators are part of a sport and we like the rules to be sound.
I think the WSSRC took the advice of the experts. In this case the Wolfson Institute who it appears did a search of the naca langley tank test US navy files (no need to reinvent the wheel).
This is quite an extentive data base of "real world" experimental data which I have used myself on many occassions.
I have not looked extensively for ground effect in water but have not found anything yet. I do remember reading years ago about differing effects on torpedos depending on the shallowness of the water and that ferry thing rings a bell as well.
If I do find something I will post the link here.
I would say that the whole rule is ill conceived and actually unnecessary. The basic premise is incorrect. If there is (and I think there probably is) and advantage to be had by sailing in shallow water this is no different to many other ways speedsailors have found advantages in the past. As long as the craft is physically touching only water and using some sort of foil in the water to counter the pull of the sail it is sailing. The example the WSSRC quotes of a craft with no fin sliding like a 'skiffle' board is clearly not possible. To sail faster than the wind, or even as fast as the wind one needs to travel at some angle across the direction of the wind and this requires some sort of sideways resistance and therefore some depth of water to lever against. Actually touching to bottom is the last thing that one wants as it will just slow one down. In this regard water depth is self limiting.
The rule is about preventing the use of pushing off a boundary through a thin layer of water to gain extra lift. Its nothing to do with water surface state (waves etc).
The canal wall is not really a wall. Its quite uneven, and since it is located on the windward side, so is exposed to the low pressure side of the fin. Not something that would give an increase in lift or decrease in drag.
Sailing on water by definition appears to be causing a lot of issues at the moment.
A few arguments seem to head in the direction that water is a lightly composed medium that gets denser or changes in some way as it is more tightly confined under pressure - at some point it does turn to steam.
Water does not compress - so for our purposes it is a hard liquid.
Are we sailing off the ground?
Yes we are always sailing off the ground and that is totally different to sailing on the ground.
We are also using the ground at all times as a solid reflection through the water - this effect might vary with depth although it always remains.
Ice sailing cannot be compared because part(the front part) of the skate needs to be touching the ice and at some stage after that the ice is likely to turn to water.
Skim boards are likely to make contact with the ground at some stage and when they do this breaches the spirit of sailing on water.
Skim boards do not run well on edge and do not have fins for obvious reasons and one,if not both of these are needed to turn wind force into a drive force.
This leaves us sailing in water until any part of the sailing vessel touches the bottom or any other substance other than water.
If the WSSRC had of set a more reasonable limit like 100mm we probably would not be having this discussion!
"Using a solid boundary to gain lift is not in the spirit of sailing"
Slowboat, can I get a refund on my solid boundry to gain lift device. Bought new from KA at Easter and still unused due to lack of suitable conditions. 23cm symetrical lift device in question is going to make sailing without very difficult so I probably will hang onto it.
"Man of" just sent me a "scuttlebutt" page with an explanation from the WSSRC in it,
here's a relevant quote.
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.
There is nothing new in this old study. The question is, how the hell can they make money if the WSSRC comes to these conclusions. Or - probably the WSSRC has taken the wrong conclusions ?
Here are the relevant statements the WSSRC uses:
1. the ground effect becomes notable, when the beam of the board is wider than the water depth. This is WRONG. the effect becomes notabel when the beam of the board is wider than the DISTANCE to the ground. Otherwise, a hydrofoil can legally sail in 51 dm og water with its foils 5 cm above the ground.
2. taking this into account, the only fair solution is to make the rule dependant on the average width of the planing surface. Lets say 30cm for windsurfers ? 10 cm for kitebaorders ? So what about a 3m wide boat that sails in 51 cm of water ? In full ground effect, but - allowed !
3. Is this fair. This can be discussed. The rule as it is now is definately unfair. There might be the need for a ground effect rule, but not in this way.
4. Is this sailing. Definately yes. Is the vessel changing somehow when coming into shallow water ? Now, still the same sailing vessel. I am not talking about skimboards here, you all know that. I am talking about a vessel that CAN sail in deep water and takes advantage of a natural effect. Luderitz is probably 10-15 cm throughout the run, probably more, so definately not skimming.
) at my local venue and not have someoen tell me it doesn't count because in their opinion I might have, at some point on the run, have veered into water below a certain arbitrary depth.
Check the image landyacht has put in this post of then sailing a skateboard type device.
www.seabreeze.com.au/forums/topic.asp?TOPIC_ID=38787
Then imagine a skim board and spinnaker in 60kts, straight downwind at 50kts no problem, (well as long as you don't crash!!!)
Magic photos as he said "...water was only a few mm deep and the which is why there are no ripples. . Anybody thinking skim board and kite?"
Andrew when you say "For me it is very clear. A craft is 'sailing' if it supported on water and using some sort of foil or surface.." I agree, but Slowie and I know that in "ground effect" the craft is not supported by only water but ground and water. The closer to the ground the greater the proportion of lift provided by the ground. The WSSRC acted quickly to make sure that they weren't left trying to close the door after the horse had already bolted.
They realise that they will need to refine the rule, no doubt aware that MI on a 50cm deep salt pond will be in ground effect AND legal. However, as the challengers need to register in advance with the WSSRC their current rule dealt with the immediate ambiguity only.
Looking at those photos maybe I'll make a drive to Kal in the next winter storm with my gps, a sled and a kite. :-))
hi guys,
if you go dead downwind in 60kn of wind doing 50kn over ground or through water your apparent wind would only be 10kn.
hardly enough to fly the kite and most likely not enough power to pull a skimboard or whatever at 50kn...
Boogie
Not if you figure-8 the kite. Then the apparant wind could be quite a bit higher.
Actually , playing around on those apparant wind calculators you find even in windsurfing if if you go very deep even in a gale the AP drops way down. Which explains the light feel of the rig. I used to think it was the equalisation of the drag on the sail with the lift.
Not sure you're right there Andrew. There's the riders inertia he can play with, depends how much the kite has to be figure eighted.
It's not going to be as much as if the rider did have something to push on, but I'm sure he can manage something.
Select to expand quote
Even if you could get the physics to work so that you could get the kite to "zig zag" downwind it is only going to be the net downwind force/velocity that the rider is going to be able to "use" as his speed ie it is the straight line distance of 500 metres that count. Curved course has been covered in debate extensivly elsewhere. As Andrew says without lateral resistance you cant go other than as the wind blows. Depth is a self limiting factor in sailing.
Yes skiffle kite boarding downwind is so hypothetical I don't think WSSRC will ever have to worry about it. You could test the theory that they could go downwind within 10 knots of true windspeed by flying a kite in just 10 knots of true wind standing sideways on a skate board. ie. rolling transverse to the wind direction. See if you can pump it to a useful pull without lateral resistance. Then figure out a skiffle boards drag vs. speed.
But of course in 65 knots of wind the lulls are going to be at least -10 knots -
Ian, think you've missed the point, the rider/skim board wouldn't be doing any zig-zagging, just the kite.
I've tried a mate's kite when he was learning, in 5kts it was very hard to get in the air, wouldn't stay in the sky parked in the neutral zone, but swooped thru the power zone I was doing 20m heel drags. In 6kts, it would just hang in the neutral zone, could hold it with my little finger, but swooping thru the power zone lifted me head high.
I wasn't game to try swooping it in 10kts.
I've watched a grommet on a skim board with a trainer kite going dead downwind in a couple of cm of water. He was in full control, no issues there at all, he even had some directional control. This was at Shearwater on the gold coast.
Granted he wasn't doing windspeed, but it's possible.
To get a kite to pull you along all you need is some form of resistance, it doesn't have to be lateral with regard to the kite line. All you need is plain old friction drag.
Well it has been an interesting theoretical exercise, but it's getting a tad too complicated now!
