34th America's Cup: multihulls!

There is no vacuum there, I can really assure you about that.
It is all about directing the flow where one wants it to go, in order to obtain an aerodynamic effect one wants to obtain.
Cheers

 

Relative to the comments about the effects on the airflow over the AC72's of the "high" speeds they a capable of consider this:

If an AC72 was an automobile it would be slow. Many if not most of us routinely drive faster than the top speed of an AC72.

If an AC72 was an aircraft it would be very slow for it's size. Even a Piper Cub with a much smaller wingspan has a considerably higher top speed.

 

Cheers for the reminder about attached and laminar - forgot about that. I remember that laminar flow is very hard to achieve and can be ruined by a waterdrop on the wing - lots of water here.

 

ETNZ are quite good at presenting red herrings as well. The 7th will be an interesting day. The air flow ahead of the boat is probably turbulent. True laminar flow is unlikely in this environment. Peter

 

e4th AC

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Peter, I was thinking the same thing. But if they're not red herrings can you see an aero benefit?

 

No Idea!! but heres some logic. 1) the horizontal surfaces are too small to provide vertical trim or effect (theory) so it may have to do with the verticals. ie the top is just an end plate. 2) So if its the verticals they again are not big enough to act as an "air rudder" so they could be fences for a particular flow off the boat. There has been some comment about the wing vortex but this is a sheet vortex off the entire trailing edge of the wing so hmmm???? I think its a rostrum to stand on when they win!! It maybe just a device to visualise the air flow in that particular region. They may have identified a sweet spot there and the telltales on these fins allows them to see the flow and check its correct eg the telltales will be pointing down when they stand on it to accept the CUP! Peter

 

To doug & petereng: I was thinking a red herring-thingies too. I would not put it past the NZ's to keep the pressure on OTUSA.

But also, maybe they are adding some anti-pitch-poll hardware. ROTFLMAO. When & if real racing starts, it will be balls-out & they will be on a ledge they haven't been close to yet.

 

A quick calc shows that if we use a Cl=1.5 and we are at 40knots we need an area of 24m2 to generate 1 tonne of lift. Those spoilers are not enough to dint the loads needed for trimming. So its a fence , rostrum or a herring. Cheers Peter S

 

or it could be some where to mount the rocket launches or jet engines.

 

I wrote earlier about the curved daggerboards that no one wanted back in the later 1970's. The other idea we had back then was to use the bridgedeck as a lifting surface, much like racing hydroplanes have. But a quick calculation showed it wasn't sensible unless the bridgedeck clearance was very low - and we were interested in offshore boats, so gave the idea up

For many years car designers concentrated on reducing air drag on the body shell. It was a long time before they realised that most of the drag came from the underside - exhausts, engine , suspension etc. Never mind wing mirrors and door handles.

Another thing - soaring birds achieve lift in two ways. Very high aspect ratio wings, as on the albatross and frigate bird, for example. Or shorter LAR wings but with the addition of individual feathers at the wing tip, as on eagles, owls etc. They are obviously very effective at fooling the air into thinking the wing is longer

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Since they mention racing LR in the video, maybe the additions to the aft bridge are meant to further spoil the air going to the trailing boat or the boat rounding after ETNZ... ?

 

Now that is interesting.....heck if they add some smoke it could be a real advantage.

 

34th AC

One of these spectacular boats will win the Americas Cup-JNavas video:
http://www.youtube.com/watch?v=UrR9D5-x9ig

 

Kiwi underhand tasteless tactics.

I go to watch a Oracle USA video, BMW ORACLE Trimaran and it starts with a ad from a KIWI challenger boat.


I wonder want Coutts And Larry think about this. Watch

http://www.youtube.com/watch?v=LZJ8m4yLFwY

Oc

 

Hi Guys - You may notice that the port and stbd camera stalks have gone. I think the spoilers are the new mounting points for these cameras, sans cameras. The round stalks would have had considerable drag, the new spoilers will have small drag. Make sense?

Opps stalks are still there cancel that comment!! Peter