Etnz boat 2

[Island Time 1,313]

So I went to the launch last night. Sure is an impressive vessel up close. Took lots of pics, here are some.

[Island Time 1,313]

The foil bearing pics are on the old boat, but give some idea of the structure arrangement for the foil pivot. A LOT of carbon for the huge loads...

So, the canoe body is more pronounced, to help earlier lift off.

The large flat hull is not for plaining, but to meet the form stability requirements.

The crew will now be below deck in the side pods, and the deck is clear.

The lower deck gives about 400mm more sail area for free.

Yes the foils in the pics are different on each side, these are foils 3 and 4 of the allowed 6.

She is to be out sailing this morning.....

[ex Elly 267]

Looks more like the British boat now.

[madyottie 82]

Are the aft sides actually a concave section as they appear in some pics? or is that just optical illusion?

I'd been thinking about ways to gain aerodynamic advantage, one obvious one is to angle the flat bottom down, thereby generating vertical "push", and I'd wondered about using hullform, since the apparent wind is always forward of the beam,  either using concave sides, which could be angled to generate forward thrust, or perhaps tunnels through the hull, which could be optimised to whatever the designed apparent wind angle would be.

I'd be quite interested to hear a bit more about the design philosophy of this "hull." I asked one of the US chase boat crew why they had a wave-peircing bow on a hull that never touched the water, apparently it's to reduce drag at marginal foiling speeds. That was all I could get!

[Island Time 1,313]

The hull is like it is to reduce wind resistance,  with the canoe body to help earlier lift out, the flat sections esp aft to provide the required form stability for the AC 36 rules. The flat deck is to provide end plate benefits to the sails. I dont think the sides are concave, they don't appear that way in reality. 

[Frank 185]

These modern AC boats must present a fascinating head game for the team modelling the fluid dynamics. I'm guessing the hull is in some sort of ground effect and there must be an endless list of hydro and aerodynamic factors to optimize at 50 knot +.

 

 

[Island Time 1,313]

Yep, I have it on reasonable authority that the aim is for this boat to fly low. The engineering is really impressive 

[Island Time 1,313]

The more I watch this boat, the more I like it! It's a marvel of engineering!!

 

[Deep Purple 530]

I was watching a bird fly across Lake Rotoiti at the weekend, wingtips almost touching the water as it flew very low, very fast and I was thinking how millions of years taught that bird that the lower it flew the less effort to remain airborne and therefore the more effort was available to move forward. 

So much like the current TeamNZ boat

[erice 732]

yes it's a dead sexy boat and the very low foiling height must help aerodynamics and probably ground-effect

as alinghi used to do they seem to have been able to launch last with a mk2.5 boat containing enough subtle improvements for that all important 1sec lead 1st mark 

and as always it seems quite possible there are even bigger improvements in the soft-wing sail and its control

[Jon 412]

2 hours ago, erice said:

yes it's a dead sexy boat and the very low foiling height must help aerodynamics and probably ground-effect

as alinghi used to do they seem to have been able to launch last with a mk2.5 boat containing enough subtle improvements for that all important 1sec lead 1st mark 

and as always it seems quite possible there are even bigger improvements in the soft-wing sail and its control

Interesting that the 3 challenging skippers where asked last Friday evening about the soft mains and all agreed that they wished they were solid wings