America's Cup - Wing profile

Victor,
to start for your main element section something like a NACA 0018 up to a NACA 0022 will work fine. For a flap a NACA 0009 will also work fine. This assumes about a 50/50 split in chord for both elements +- 5%

Getting your hinge location in the right place is a big one to pay attention to, and ideally have some way of controlling your slot size will make a big difference when sailing at high angles of attack such as deeper downwind.

The sections do not make a huge difference to the boats general performance. Different sections can be more slippery or draggy, but some "hook-up" more quickly meaning they are more forgiving to trim. Likewise some sections tend to "fall off the cliff" when they approach stall, meaning they go from fully flying to stall quite quickly and without much notice they are about to stall.

Our sections push the maximum thickness further forward that the basic NACA sections, mostly to have a slightly higher Clmax and also simply to cut down on the amount of heavy bits (Solid leading edge vs clysar film flatish bits).

Hope that helps.

 

I disagree in accuracy and repeatability. Measuring down from a known point isn't difficult and can be accurate as would be lining off perpendiculars, so the template can be located properly. I don't think this is the best approach on an AC boat, but certainly doable. We don't know how much filler is actually there. It could be just a skim coat or a 1/4" thick. It also could be a change that they've elected to try, with a different set of profiles, which seems to me the most likely.

 

That picture was originally posted to refute the contention of a nut case on another forum that you can't accurately fair a foil by hand. I've done it hundreds of times so I know you can but having Team Luna Rosa photographed doing just that was too good to pass up for all the RC guys building and shaping foils by hand using patterns.

 

The sections used for AC72 wingsails are proprietary to the three design teams. Different approaches have been used for the various wings.

On one extreme is Artemis' first wing, which had a main element of approximately 70% chord, a flap of 30% chord, thickness well back on the main element, and a long length of hard shell structure. This wing was evidently designed to maintain long runs of laminar flow, in order to minimize the profile drag.

On the other extreme is the wing design used by Emirates Team New Zealand and Luna Rossa, which has a main element that is approximately 40% of the total chord, a 60% chord flap, and a comparatively short amount of hard skin in the outer shell. This approach apparently assume the boundary layer would be essentially fully turbulent, and was designed for high maximum lift.

The wing section on 17 is in between these two extremes, with a 50%/50% chord main element/flap proportion. Artemis moved closer to the ETNZ approach with their second wing, with approximately 45%/55% main element/flap proportions. Their third wing has not yet been revealed.

It's not at all clear if laminar flow is even possible, depending on the amount of free-stream turbulence in the wind. So designing for a fully turbulent boundary layer is probably the most reliable approach.

A NACA 0018/NACA 0010 combination is a reasonable choice. You could move the maximum thickness forward on the flap, say from 30% flap chord to 20% flap chord to extend the pressure recovery region. That's because pressure recovery is the main job of the flap in a multi-element section. If you have a large flap chord, you could make the thickness ratio for the main element higher and the thickness ratio for the flap thinner. The shorter your main element, the larger the thickness ratio has to be in order to provide the physical thickness needed for stiffness.

What's more important than the section shape is that you have a ready means of controlling the twist. This can be done by just twisting the flap, or it can be done by twisting the main element and flap together. The tradeoff is a twisting main element can be more aerodynamically efficient, but it will be heavier and less stiff than a rigid main element. And more complicated to build and control.

The twist and camber controls should be self-tacking so you don't have to readjust them every time you tack. And it would be desirable to be able to force camber/twist into the wing, both to camber up the top and to make it twist off, rather than just relying on airloads to achieve twist.

The control system design in a wingsail is really important - more so than the choice of section shape. The biggest source of drag is induced drag, and this is controlled through the twist and planform shape. It's worth the effort to minimize friction and get a system that is easy for the crew to achieve the target camber and twist angles. One way to minimize stretch is to use an inverse purchase at the bottom and a conventional purchase at the top. This reduces the load on the control lines going up the wing, allowing the use of smaller diameter lines for less weight or less stretch for the same size line.

 

Hello,
so last weekend I started complete my plans and prepare some visualisation... here they are... I decided for NACA 0021 (60%)and NACA 0010 (40%).
Eing would be 30 ft high...

I would like to build it by composite materials...

But I don't know about material of profiles... I have many experiences with AIREX tecnology.. but I think it is to much expensive... what about normal polystyren and plywood?

I thought, I will build it by AIREX and laminate it or use carbon fibre...

And then is here question about surface of the wing... i thought to use
fibreglass cloth (360g/m2) and laminate it.. but I don't have experiences with using it for wing...

Thank you for your response...

 

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Foils! Thats great...... Are you planning on sailing with the windward main foil retracted? I'm not sure whether you know or not but the Flying Phantom is based on an F18-but much lighter and with a 10' beam. There is a Phantom thread here and more on both the Phantom and Nacra F20c foiler used by the Hydros Team in the LAC thread-also here.

 

Maybe they are altering the original profile. Yes ?

Par, "and the two fairing that foil probably can't spell CFD"

That is just rude, arrogant, judgemental, elitist etc. Oh and totally unnecessary.

 

Catamaran is only for "illustration"... at this moment I work on wing sail... for first testing we are going to use original F18... but on the program is also foiling F18 with all elements for sailing...
I helped with building of boat for Class Mini 6,50 in prototype class... (Boat of czech sailor Milan Koláček - boat number 759) so I have some experiences with asymetric daggerboards...

In my plan would be boat like Phantom... ligtheer body, asymetric profile of surface of girder for supporting fly up catamaran... and I also think about foils and T-rudder style...

I designed few months ago foiling rudder by using symetric profile Eppler... boat has some interesting resolts!!..
At this moment I' thinking about ASYMETRIC profile of rudders... does any one have experiences with this?
Btw...aperture between wings is 4 cm.. but I will build it with possibility to change this distance during the testing...

For example another news from my work! I also work on new system of soft wing which could be same and still different from Omer Sail and there soft wing.. it's based on junke sail system as "innovation"... but this maybe next time
Visit website of my friend - www.multihulls.cz... we are finishing 32 ft long trimaran!

 

The wing profile for the Ac 72 is constrained by class rules, so it is arbitrary and should not be used as an example of research and development.
Wing construction can be achieved using very low cost materials, the weight and durability of the wing will be affected. Lindsey Cunningham's wings were largely built out of very ordinary materials. The frame was built out of carbon fiber tubes about like a bicycle, but everything else was plywood, aluminum and styrene foam covered with airplane fabric. We use lighter packaging films for our covers, but spend a bit more time and money molding parts.
SHC

 

Voiles and Voiliers has another of their excellent articles, this time featuring designers Dimitri Despierres and Joseph Ozanne explaining America's Cup wings (in French. This is the first of a 2-part article, but the 2nd part will be subscribers-only).

Dimitri Despierres et Joseph Ozanne vous dévoilent les ailes (1)

Some of you may recall that during/after AC33, it was Joseph Ozanne who first described in greater detail the 72 meter tall wing of USA17/Dogzilla, then also in Voiles and Voiliers.

I've not had much spare time on the internet lately, but if anyone finds bits that are difficult to translate then refer to them on the America's Cup thread and I'll see if I can help!

 

It's very important to build the wing to be as light as possible. Having built a wingsail out of plywood, I think it would be much too heavy for use on a boat.

I think the typical construction is to use carbon fiber skins with foam or honeycomb core to construct a D tube spar for the leading edge. Then ribs cut from carbon & honeycomb flat sandwich panels. The covering is typically a shrink-wrap packaging film from Clysar, applied with double-sided tape.

Something like North's Thin Ply Technology (TPT) laminates might be the way to go for a small cat.

 

Perhaps an investigation of methods used for building the wings of ultralight and homebuilt "experimental" aircraft would be useful.

 

Sometimes there is a little work of disinformation, with "fake" pics and so on. The method on the picture looks so primitive that's confounding. Just for some guys trying to make photometry and reproduce the profile (there are softs for that...)

I've worked long time ago (in a galaxy far far away...) on a F40 catamaran with dagggerboards-foils that worked very nicely, calculated and tried by the Centre d'Essais des Carenes.
Some wanted too badly the profile(s)...so I left on the cata 2 daggerboards we have tried before and reproved as being unstable and dangerous. They remained on the boat during two days at Brest, just the time to get nightly measured and copied. One month later a concurrent had the same kind of daggerboards and got the same bad results...Big laugh.