Brits having a hard time in AC?

[MikeBz]

The technology is un-deniably incredible and this is without doubt the bleeding edge of the sport.

However, from what I've seen so far, the racing leaves a lot to be desired. Since they increased the size of the start box yesterday, there is now no pre-race argy-bargy. There is little or no tactical racing. Nobody is hunting out the puffs, tacking on the shifts, or picking a favoured side of the course, because the gains are massively outweighed by the losses suffered through a manoeuvre. So they are just banging the corners, and it is just a drag race.

Added to which, a small mistake doesn't lose a team 50m, it basically spells the end of the race. There have been a few "bits" of racing here and there over the past 2 days, but overall it's been boring.

As amazing as these boats are, my feeling is that they have gone too far with it to the point where it's no longer match racing and is just drag racing where the team with the best technology wins.

I completely agree... but... that has always been the case with the AC. Even after multiple cycles of 12 meters the final would be dominated by one boat. The best it got IMHO was towards the end of the IACC boats when they really did start to converge and give some great match racing. One advantage of the rapid pace of development possible these days is that if you allow one set of rules more than a couple of iterations (cup cycles) then the designs really do converge and give the possibility of good racing. Sadly it generally seems to be in the winner's interest to consort with the Challenger of Record to change the rules and give themselves a head start, thus restarting the arms race and the gulf between different early design approaches.

 

[wully1]

From the very little foiling I’ve done it takes surprisingly little power to get up , much, much less to stay up but then controlling ride height was the hardest thing to master.

Extrapolating my pathetic attempts to the extremes of the AC boats and watching videos of Ineos their foils do not seem to be as well tuned as the opposition- I always thought there was excessive spray from them- I cannot imagine how difficult it must be to design and fly the foil they need. I assume they tune the angles of attack as they accelerate, transition to foiling then accelerate to speed in conjunction with trimming the sails and hull balance....
Im impressed they get those boats off the water.

 

[matt1]

Interesting! I noticed the large amounts of spray and kind of thought... “that can’t be clean or efficient”

 

[Laser310]

Interesting! I noticed the large amounts of spray and kind of thought... “that can’t be clean or efficient”

compare the mass of water contained in that spray, with the mass of water contained in the wake of a 75ft displacement boat

it's probably a few orders of magnitude less.

 

[wully1]

compare the mass of water contained in that spray, with the mass of water contained in the wake of a 75ft displacement boat

it's probably a few orders of magnitude less.

The lift generating part of the foil is under water so should generate no spray or wake? Only the vertical part is breaking the surface and should generate minimal spray? Spray = turbulence =drag? These boats should be foiling so displacement rules should not really apply?
I really don’t understand how all the trade offs between lift, drag, heeling moment, lee way etc. can be balanced - but it looks like the Kiwis do.

 

[Laser310]

The lift generating part of the foil is under water so should generate no spray or wake? Only the vertical part is breaking the surface and should generate minimal spray? Spray = turbulence =drag? These boats should be foiling so displacement rules should not really apply?
I really don’t understand how all the trade offs between lift, drag, heeling moment, lee way etc. can be balanced - but it looks like the Kiwis do.

i was not suggesting that "displacement rules" apply to these boats.

i was observing that what might seem like a lot of spray is actually a small amount of water compared to the water in the wake of a displacement boat.

the spray you noted is a sign of inefficiency, in that the sails have to accelerate that water in addition to accelerating the boat. comparing with a displacement boat that has little to no spray.., we need to look at the displacement boat's wake- the wake represents water that was originally not moving, but is moving after the boat passes - the force to accelerate the water came from the sails, and is an inefficiency. in fact, a displacement boat is dragging quite a bit of water around...

 

[Bobc]

Now looks like the entire Christmas Cup regatta has now been cancelled due to lack of wind. You really couldn't make this up.

I wonder whether the Prada Cup will end up going the same way.

 

[wully1]

i was not suggesting that "displacement rules" apply to these boats.

i was observing that what might seem like a lot of spray is actually a small amount of water compared to the water in the wake of a displacement boat.

the spray you noted is a sign of inefficiency, in that the sails have to accelerate that water in addition to accelerating the boat. comparing with a displacement boat that has little to no spray.., we need to look at the displacement boat's wake- the wake represents water that was originally not moving, but is moving after the boat passes - the force to accelerate the water came from the sails, and is an inefficiency. in fact, a displacement boat is dragging quite a bit of water around...

I am still puzzled as to why some teams spent so much design time and effort in the underwater hull shape - I’d imagine you’d want all your effort toward the best foils and aerodynamic hull shape for Flying. They don’t look like the planing hulls of an IMOCA for example and all the slot effect talk should not apply if they foil which is what the good teams seem to do virtually all the time.

 

[halcyon]

I am still puzzled as to why some teams spent so much design time and effort in the underwater hull shape - I’d imagine you’d want all your effort toward the best foils and aerodynamic hull shape for Flying. They don’t look like the planing hulls of an IMOCA for example and all the slot effect talk should not apply if they foil which is what the good teams seem to do virtually all the time.

It's not as though it's unknown technology, just an adaption of this

Brian

 

[Bobc]

I am still puzzled as to why some teams spent so much design time and effort in the underwater hull shape - I’d imagine you’d want all your effort toward the best foils and aerodynamic hull shape for Flying. They don’t look like the planing hulls of an IMOCA for example and all the slot effect talk should not apply if they foil which is what the good teams seem to do virtually all the time.

I doubt they were focussing on the underwater profile from a displacement sailing perspective, other than looking at the modes between displacement and foiling, in order to encourage early foiling by reducing drag quickly whilst keeping a bit of buoyancy and lift. Most of the the hull shape work was on achieving ground effect and using the water as an end-plate to create a venturi under the hull.

 

[Mudisox]

Maybe they could ask the guys who designed and developed the buccaneer aircraft.

 

[wully1]

I doubt they were focussing on the underwater profile from a displacement sailing perspective, other than looking at the modes between displacement and foiling, in order to encourage early foiling by reducing drag quickly whilst keeping a bit of buoyancy and lift. Most of the the hull shape work was on achieving ground effect and using the water as an end-plate to create a venturi under the hull.

These boats were designed to foil - they ‘should’ only need to get up ONCE so the focus should have been on efficiency on the foils. Devoting time and money on the tiny amount of time they are transitioning to foiling seems like a real waste of effort to me.

Anyway, I hope the brain trust are successful in getting the boat up to competitive speed for the rest of the racing.

 

[dunedin]

These boats were designed to foil - they ‘should’ only need to get up ONCE so the focus should have been on efficiency on the foils. Devoting time and money on the tiny amount of time they are transitioning to foiling seems like a real waste of effort to me.

Anyway, I hope the brain trust are successful in getting the boat up to competitive speed for the rest of the racing.

Except, as Britannia sadly demonstrated in the last race, if in the prestart you drop off the foils and cannot get airborne again, the losses are so huge that you are promptly LAPPED by the opposition still on its foils. So getting flying in low wind speeds is absolutely critical

 

[Bobc]

These boats were designed to foil - they ‘should’ only need to get up ONCE so the focus should have been on efficiency on the foils. Devoting time and money on the tiny amount of time they are transitioning to foiling seems like a real waste of effort to me.

How do you know what proportion of time they spend on the foils. Anyway, it's not as simple as that. The bigger the foils and the more lift they create, the more drag they create also. So big foils with a high lift profile will get the boat foiling sooner but will have a slower top speed, whereas smaller, thinner foils will allow a higher top speed but will not create as much lift. So the whole "ground effect" hull shape really does matter, as this can create lift without the associated drag. Don't forget that the first iteration of the boat (and the American boat) were basically very flat underneath, and I suspect that they found the hulls very "sticky" (i.e. it took a lot of power to get the hulls to break clear of the water), which is why they have all shaped the hulls with things that look like steps (they are basically steps which reduce the wetted area, and hence the drag, quickly in stages as the boat begins to foil). This is a horribly complicated subject.

My worry is that it all comes crashing down because if there isn't enough wind for these boats to foil, the entire event becomes a failure.

 

[Ravi]

Now looks like the entire Christmas Cup regatta has now been cancelled due to lack of wind. You really couldn't make this up.

I wonder whether the Prada Cup will end up going the same way.

Watching the AC mega yachts doing 4-5 knots in 10 knots of wind in the last race made me wonder if any previous AC race could have been won by a club racing dinghy.

 

[Kukri]

Well, yes, but all yacht races become failures if there is no wind.

 

[Bobc]

Well, yes, but all yacht races become failures if there is no wind.

True, but wouldn't be a complete disaster if every race ended-up like the last one, with one boat being able to foil and the other not. That's a sure fire way to turn everyone off the Americas cup for a generation.

 

[Daydream believer]

True, but wouldn't be a complete disaster if every race ended-up like the last one, with one boat being able to foil and the other not. That's a sure fire way to turn everyone off the Americas cup for a generation.

You mean like the current Vendee?

One thing in our team's favour is that in displacement mode it was definitely faster than team NZ. In the event of a loss of wind toward the end of a race that could be a race winning point.
That might have been down to Benny boy & not the boat.
It also should help a boat get up on the foils. The faster it can go in displacement the easier it should be to get up
So it is a small element of design that should possibly be retained, if it does not impact elsewhere

 

[RJJ]

Watching the AC mega yachts doing 4-5 knots in 10 knots of wind in the last race made me wonder if any previous AC race could have been won by a club racing dinghy.

It would certainly seem that in any race where the boats spend significant time non-foiling, that a decent 505 would be in with a shout not to mention an 49er or 18 skiff.

 

[RJJ]

I agree with earlier posts. The IACC, after two or three iterations, gave us punters the closest match racing the event has ever seen.