Sir Ben & the Americas Cup

[Ayahuasca]

Paddy_N_Murphy said:

Media coverage / up to date reporting is awful


Is that it??

It is for BAR.

[ecsrobin]

It may be over for 4 years but Land Rover have said they’ll continue to sponsor the team for the next event

[anonymous-user]

Paddy_N_Murphy said:

Media coverage / up to date reporting is awful


Is that it??

Yeah, I saw much more on the tv last time and that was without British interest.

Without BT sport or free view you'd see nothing. Not even highlights.

[OtherBusiness]

I'm glad it was on BT showcase. Valiant effort, roll on next time!

[ben5575]

Agree re coverage.

I was watching the Drive video on youtube (having been searching for coverage) that was meant to explain how the foils work but failed miserably (to me at least).

One of the guys in the video gave the example that if you put one of these boats on the amazon with zero wind and a current of 10knots, then the foils would 'sail' the boat directly upstream at 20knots.

Can anybody provide a numpty explanation of how on earth this works please?

[Phud]

I am still having issues getting my head around 6Kts of wind 36Kts of boat speed.

All I can say is aerofoils and lift not sailing, but really "there be magic"

[Silent1]

Phud said:

I am still having issues getting my head around 6Kts of wind 36Kts of boat speed.

All I can say is aerofoils and lift not sailing, but really "there be magic"

Extraction of energy from the wind is greater than the amount to move the boat at the speed of the wind so in anything but a headwind they will move faster than the wind due to the low amount of friction from the water?

[Phud]

I get the principle and have a keen interest in the various hydro and aero dynamics,

but to watch this leaves me in awe, watching the various small differences in wing and foils to see the difference, also the power recharge from cyclos against hand cranks.

But yes, the less in the water the lower the friction and less power needed to propel the yacht balance against flying the hulls and not pitching bows down or taking off.

[ben5575]

I get the foil lifting the boat out of the water (like a wing) which obviously results in less drag than having the hull in the water, but I can't get my head around how these foils also propel the boat as well.

How can a foil push a boat upstream at 24knots against a down stream current of 12 knots if the sail itself (wind) is taken out of the equation?

Video in question: https://youtu.be/WBG1g8s3BT0?t=519

This video explains some of it although I'm still confused: https://www.youtube.com/watch?v=nQxmw6qSR9s

[AnotherClarkey]

ben5575 said:

I get the foil lifting the boat out of the water (like a wing) which obviously results in less drag than having the hull in the water, but I can't get my head around how these foils also propel the boat as well.

How can a foil push a boat upstream at 24knots against a down stream current of 12 knots if the sail itself (wind) is taken out of the equation?

Video in question: https://youtu.be/WBG1g8s3BT0?t=519

This video explains some of it although I'm still confused: https://www.youtube.com/watch?v=nQxmw6qSR9s

The sail is not taken out of the equation though. The whole boat is a machine for exploiting relative movement between air and water. If there is no wind but the current is 12 knots then even when the boat is at rest in the water the sail is being moved through the still air at 12 knots - and with 12 knots flowing over the rig you are then able to go places. It is exactly the same effect as if the water was still and there was 12 knots of wind.

Try getting your head around this one:

https://youtu.be/5CcgmpBGSCI

Edited by AnotherClarkey on Sunday 11th June 21:22

[ben5575]

AnotherClarkey said:

The sail is not taken out of the equation though. The whole boat is a machine for exploiting relative movement between air and water. If there is no wind but the current is 12 knots then even when the boat is at rest in the water the sail is being moved through the still air at 12 knots - and with 12 knots flowing over the rig you are then able to go places. It is exactly the same effect as if the water was still and there was 12 knots of wind.

Try getting your head around this one:

https://youtu.be/5CcgmpBGSCI

Edited by AnotherClarkey on Sunday 11th June 21:22

Ahh, now I get you. That makes sense.

That video you linked is a bit of a mind bender! There's enough energy in the blades which are connected to and drive the wheels which push the car past the speed of the wind, the wheels in turn drive the blades, which generates it's own wind through the forward motion (but in the opposite direction to the actual wind), to keep it accelerating.

Maybe

Edited to apologise for wandering off topic.

[The Moose]

I'm pretty certain it's witchcraft

What I want to know is what are the guys doing who are waving their arms around/cycling?

[Blaster72]

ben5575 said:

AnotherClarkey said:

The sail is not taken out of the equation though. The whole boat is a machine for exploiting relative movement between air and water. If there is no wind but the current is 12 knots then even when the boat is at rest in the water the sail is being moved through the still air at 12 knots - and with 12 knots flowing over the rig you are then able to go places. It is exactly the same effect as if the water was still and there was 12 knots of wind.

Try getting your head around this one:

https://youtu.be/5CcgmpBGSCI

Edited by AnotherClarkey on Sunday 11th June 21:22

Ahh, now I get you. That makes sense.

That video you linked is a bit of a mind bender! There's enough energy in the blades which are connected to and drive the wheels which push the car past the speed of the wind, the wheels in turn drive the blades, which generates it's own wind through the forward motion (but in the opposite direction to the actual wind), to keep it accelerating.

Maybe

Edited to apologise for wandering off topic.

I don't get it

If the boat is being taken downstream at 12kts I understand there is then wind passing over the sail. This is used (with witchcraft) to push the boat forwards. Surely when the boats forward speed reaches 12kts all that witchcraft stops as the boat will in effect be stationary on the river.

Mindbending stuff this has all the hallmarks of the aircraft on a conveyor belt debate.

[ben5575]

I can only think about this on a numpty level so my explanation is at that level. It is also probably completely wrong, so feel free to tell me I'm talking bks! Four numpty principles:

1. Tack - The fact that you can sail a boat into wind. Which is in itself a little counter intuitive
2. As above, if you are drifting on the water flowing at 12knots then you will have 12knots of wind over the sail
3. The foils are no different (for simplicity) to a sail, just that they are using water power instead of wind power
4. It is not the speed of the air or the water, but the energy that they carry

Take water flow out of the equation for a moment. If you had 12 knots of wind blowing down the river (that wasn't flowing), then to travel upstream you would tack against this wind to sail upstream.

However, in this example of the flowing Amazon with no wind, you don't have wind in the sail (for the moment), but you do have 12knots of water flowing against the underwater sail, i.e. the foils. So instead of using the sail and the wind to tack upstream, you use the water flow and the foils to 'tack' upstream.

Once you have movement upstream, then you have wind in the sails generated by the movement of the boat (much like sticking your hand out of the window of a moving car on an otherwise windless day).

This wind is then in turn used to propel the boat as well as the water flow. The energy in the millions of tonnes of water flow and the generated wind captured in a big sail is used by the lightweight single machine (boat) to propel itself faster than either the wind or the water is flowing at.

Maybe.

[CrutyRammers]

Wasn't really aware about this stuff until I saw the pitchpole the other day. It's quite fascinating though, reminds me of when F1 was interesting.

[AnotherClarkey]

ben5575 said:

I
4. It is not the speed of the air or the water, but the energy that they carry

This is the key statement. The speed of the boat is limited by the efficiency with which it can exploit that energy, not by the speed of the wind (or water) itself.

It all comes down to the lift:drag ratio of the whole shebang. Boats suffer from lots of drag associated with pushing a hull through the water - hence the interest in hydrofoils to reduce this. Land, and especially Ice yachts quite easily manage 5 times windspeed.

[MBBlat]

The key is Apparent Wind - as your speed increases, you generate airflow due to your speed, which in turn gives you more speed. The downside is the extra wind comes from the direction you're going, this is why the AC yachts are still close hauled when going downwind. The other impact is that directly down wind is a lot slower than 20 degrees off dead downwind, so much so that both upwind and downwind are sailed as zig-zags.

For foiling without the AC budget, try a Moth
https://youtu.be/xHkPfnhLoZY

[CrutyRammers]

MBBlat said:

For foiling without the AC budget, try a Moth
https://youtu.be/xHkPfnhLoZY

Can't even sail, but I want that.

[MBBlat]

CrutyRammers said:

MBBlat said:

For foiling without the AC budget, try a Moth
https://youtu.be/xHkPfnhLoZY

Can't even sail, but I want that.

Are you sure?
https://youtu.be/11pEhHsge2E
It can be a bit wet I want to try one though

[Ayahuasca]

CrutyRammers said:

MBBlat said:

For foiling without the AC budget, try a Moth
https://youtu.be/xHkPfnhLoZY

Can't even sail, but I want that.

That's not sailing - it's flying! Awesome.

I wonder if the side wings generate any lift in the air?