There is something about not being allowed any form of stored energy except for instrumentation. I think Petrol for the hovercraft fan would count as stored energy.

You could make your own porpoise skin and stick it to the bottom. Say neoprene with a monofilm skin.. it has been tried for reducing drag etc ( for torpedos and other US Navy S**t) but the results were inconclusive. But if ride quality is what you want it may work... but then so would thicker deck pads and they would be a lot simpler.

I'd read a geeky definition once, which for some reason I have remembered, along the lines of..

"Sailing : Utilising the velocity discontinuity between two fluids for the purpose of travel in a third direction."

It's a definition consistent with the one the WSSRC is heading towards.

frant said...

sailquik said...

There is something about not being allowed any form of stored energy except for instrumentation. I think Petrol for the hovercraft fan would count as stored energy.

Sorry Andrew. The big money boys always get their way. Now every maxi has electric winches and hydraulic systems with the generator (powered by oil) running full time. Sort of stretches my definition of sailing much more than sailing a craft in shallow water which is capable of sailing from A to B and back in open water .
Nebian I think you might be stirring though.

True Frant, but the use of those is under offshore rules, not the rules for speed sailing records which forbid such devices. I guess it is inevitable that offshore 'sailing' boats will use powered winches for rig and keel adjustment.

"Sailing : Utilising the velocity discontinuity between two fluids for the purpose of travel in a third direction."

I very much like this definition of sailing. Taking the difference in the velocity vectors of water and air and utilising the generated forces to make speed. It fits very well with my own conceptual image of what we are doing when we sail.

If we try to fit the current technologies to this definition, we can see that most systems fit well. Normal water craft use the hull and foils to grip the water, and the sail to grip the air to generate speed. Hydrofoils do it differently, using only foils in the water and sails in the air, but still is a perfect fit to the definition. Kiters on deep water also fit this definition perfectly, with the hull creating grip on the water and the kite gripping the air.

The only technology I have trouble with is using ground effect. Ground effect upsets the definition because we are now not strictly working with fluids. At least not working with fluids in the same way. By using ground effect, much of the energy loss that would be absorbed by the water to generate downwash is now retained due to the close presence of the ground, and therefore bypassing the normal bahaviour of the water. The fluid now does not respond purely as a fluid, but more as a solid. We might as well start using greased rails...

In my view, ground effect is a great thing to try out and have some fun with. It could also be used in most competitions where everyone has the same opportunity and record claims are not possible or likely. In this case, the organisers should be clear in the rules if skimming is legal. But it should not be allowed for any kind of "water sailing" record. This restriction is not a go at kites. It should apply to sailboards and specialised skimming boats as well. I can see the Macquarie Innovation being able to generate phenominal speed by shortening its foils and running in a 51cm deep ditch.

This means sailors wishing to break a water sailing record should be careful not to venture too close to a shallow bank in case they forfeit a record. A clear set of guidelines should be written so that sailors are in no doubt about what water depth they should be in. For those wishing to pursuit skimming records, then go ahead and start a new category!

Chris has set his GPS records in deep water, as have 99.9% of sailors on the planet. The only situation I can think of where a sailing record might have been broken in water shallow enough for ground effect is the nautical mile at Walvis. Looking at the photos I would suggest that it had no effect because the sailors were too far from the bank when the record was broken. But there was some discussion about sailing in very shallow water last year giving sailors a major benefit. I am not sure if Bjorn did that in 2006.

nebbian said...

frant said...
Nebian I think you might be stirring though.

Guilty as charged, m'lud


I'm still thinking that a board with an air cushion would be faster though.

Have you tried a Hypersonic?

sailquik said...
[

Maybe not. The biggest component of water drag is still probably the fin. Hard to do away with that.....

I'm up for an argument over that Sailquick The total board/sailor/rig system is about 100kg. Gravity never gives up so you always have to have 100kg of vertical lift. If you look at equilibrium of the moments and translational forces of the system in typical sailing configuration you would estimate the lateral force to be provided by the fin at about 50 kg. (assuming board contributes none)
The sail raked over head might direct a bit of its lift vertically ~ 10 kg. The aerodynamic lift on the nose .... is still board lift.

So with the fin developing roughly 50 kg of lift and the board 90 kg the relative drag gets down to the lift to drag ratios of planing hull vs fully submerged foil.

At low speed where control is not an issue hydrofoiling moths and windsurfers out perform the planing hulls. This demonstrates that fully submerged foils have better lift to drag ratios than planing hulls. Lumping drag even more with the hull.

I'd thus argue that hull drag is about 3-5 times that of the fin drag.

Even a small reduction in drag results in a noticable speed increase. Hulls generate lift pretty crudely compared to fins, for a hull of given width the subtle differences are more directed at improving control. Fins are pretty complex and the fine details do affect drag to a greater relative degree than the details of hull design. Hence fins are the focus of attention in drag reduction.

TimeMachine said...

"Sailing : Utilising the velocity discontinuity between two fluids for the purpose of travel in a third direction."

I very much like this definition of sailing. Taking the difference in the velocity vectors of water and air and utilising the generated forces to make speed. It fits very well with my own conceptual image of what we are doing when we sail.

If we try to fit the current technologies to this definition, we can see that most systems fit well. Normal water craft use the hull and foils to grip the water, and the sail to grip the air to generate speed. Hydrofoils do it differently, using only foils in the water and sails in the air, but still is a perfect fit to the definition. Kiters on deep water also fit this definition perfectly, with the hull creating grip on the water and the kite gripping the air.

The only technology I have trouble with is using ground effect. Ground effect upsets the definition because we are now not strictly working with fluids. At least not working with fluids in the same way. By using ground effect, much of the energy loss that would be absorbed by the water to generate downwash is now retained due to the close presence of the ground, and therefore bypassing the normal bahaviour of the water. The fluid now does not respond purely as a fluid, but more as a solid. We might as well start using greased rails...

In my view, ground effect is a great thing to try out and have some fun with. It could also be used in most competitions where everyone has the same opportunity and record claims are not possible or likely. In this case, the organisers should be clear in the rules if skimming is legal. But it should not be allowed for any kind of "water sailing" record. This restriction is not a go at kites. It should apply to sailboards and specialised skimming boats as well. I can see the Macquarie Innovation being able to generate phenominal speed by shortening its foils and running in a 51cm deep ditch.

This means sailors wishing to break a water sailing record should be careful not to venture too close to a shallow bank in case they forfeit a record. A clear set of guidelines should be written so that sailors are in no doubt about what water depth they should be in. For those wishing to pursuit skimming records, then go ahead and start a new category!

Chris has set his GPS records in deep water, as have 99.9% of sailors on the planet. The only situation I can think of where a sailing record might have been broken in water shallow enough for ground effect is the nautical mile at Walvis. Looking at the photos I would suggest that it had no effect because the sailors were too far from the bank when the record was broken. But there was some discussion about sailing in very shallow water last year giving sailors a major benefit. I am not sure if Bjorn did that in 2006.

Great insight Mal, I'm with you 100% mate.