OPEN 60's: Lifting Foils (still) OK!

Fantastic interpretation of the rules means that a boat designed to use a one design rig and keel can use lifting foils.Here's an excerpt from the story in Scuttlebutt tonight:
(Read the whole article here: http://www.sailingscuttlebutt.com/2...r&utm_term=Racing around the world with foils )

Since the last America’s Cup, foils have been the focus of much attention in the world of sailing. These appendages take the weight off the boat, improving their performance, and in the case of multihulls allow them to fly. In the IMOCA class, which is in charge of the Open 60 monohull for the singlehanded non-stop Vendée Globe race, they recently established its new class rules following much debate around this question: should foils be banned?

In the end, it has been decided that the rules should not be changed, thus leaving the door open for these rather ‘exotic’ appendages to be allowed. Here the President of the IMOCA, Jean Kerhoas is interviewed on the Vendee Globe website:

JKJean Kerhoas, can you explain to us how the IMOCA came to a decision concerning the use of foils?
“To understand this matter, you have to look at the major decisions concerning the IMOCA rules currently in force and that everyone now knows: the mast and canting keel are one design features, while the hull and appendages remain open. It’s true that within the class there has been some discussion about this question. Without revealing any secrets, some teams applied pressure stressing the need to strengthen still further the mast to take into account the development of more powerful hulls and the possibility of using “exotic” appendages, including foils.

“Opinions diverged with some pleading in favour of more changes to the rules (with a ban on foils for example, editor’s note) with others arguing that the recently modified rules should not be changed again after all the previous lengthy discussions. In the end, the IMOCA board decided not to modify the class rules. This decision is quite simple. No change to the rules means that everything that was allowed remains allowed.”

Just to be clear, that means that “exotic” appendages, such as foils, are a possibility for the new boats?
“In theory, yes. It really means that the choice of appendage remains open (or in other words that designers and studies can continue to work in this area, editor’s note). But that doesn’t mean that any old thing is possible. Everything on the boat has a bearing other elements and as nothing is being changed, what they come up with still has to respect the use of the one-design mast and keel. Those are designed for a certain power (30 tonnes/metre for the mast). Respecting those parameters limits the possibilities. But it is true that “exotic” appendages are not banned.”

 

Imoca 60 the Foiler.

 

Open 60 foiler

Cool, but I wonder if the extra RM from a big DSS foil might not be better?

 

IMOCA 60 Foiler.

Might be better? But the DSS foil does not provide resistance to leeway. Therefore does require a fixed keel or different appendage and does not have the benefits of a swing keel.

 

Open 60 Foiler

Good points!

PS- it looks like the foil section would be dictated-to some extent- by the hull surface? The recess in the hull when the horizontal foil is deployed seems like a drag-maybe that could be solved with some sort of flexible membrane?
DSS can be retracted completely so it doesn't need to be used in conditions that don't warrant it. Both DSS and this foil system seem like they would be disadvantaged by sailing at an angle of heel-but tests would surely show one more effective, I'd imagine. Good idea, Yves-have you got an interested client?

 

Can they use both the traditional Daggerboards and DDS? Seems like that would be the most logical, but is that allowed?

 

Open 60 Foiler(s)

Yes, DSS(Dynamic Stability System) has been legal for some time. And using it and a conventional daggerboard is legal-but so is Yves idea. The question came up after they converted to a one design keel and one design mast. While those two one design elements constrain a foil systems effectiveness to a degree, the clarification on the foils was recently released-I gather after a few designers must have asked. The ruling is outstanding because it puts the innovation level back up almost where it was before the one design nonsense came up-and gives designers a golden opportunity to try new kinds of foils. And lifting foils are the future in so much of sailboat design.....

 

I think they have sealed cups like a airplane. Look up at a jetliner sometime, lot of them you can see the wheels in the well when retracted, long as it's not open in the backside they don't induce much drag at all.

Barry

 

Open 60's

IMOCA reaffirms that foils are LEGAL by an overwhelming vote:
http://www.vendeeglobe.org/fr/actua...s-imoca-les-explications-de-jean-kerhoas.html

Skippers and owners of the IMOCA gathered for their annual meeting this Wednesday, October 15, Nantes, following an important question raised by one of its members: should allow or disallow the holders of new generation appendages called also "foils"? These appendages would not fly in the real sense, as now do the multihulls America's Cup, but to "relieve" and therefore "alleviate" some points of sail boats and wind forces. After debate where each view has been expressed clearly, the General Assembly of the IMOCA finally followed the opinion already expressed by its Board of Directors a month ago (September 15): we do not change again the rule. This means that new appendages remain allowed. This decision has been taken by a large majority: of 77 enrolled, there were 69 voters and the vote was as follows: 53 for, 15 against, 1 abstention.

 

Open 60's with Foils

Interesting article found on SA: http://www.thedailysail.com/offshore/14/67270/0/dss-foils-to-revolutionise-imoca-60-fleet
They speak of the possibility of using an "L" foil with the tip pointing outboard to combine a daggerboard and a DSS foil. Not a good idea......

Two renders from the article and my sketch that explains why its not a good idea(leeway arrow shows the direction the boat and foil move due to leeway) :

 

Open 60 with Foils

Hugh Welbourn's comments on this:

Theres another issue on the movement plane/axis being one plane/axis only, no helical movement for example, so that forces you into solutions that you wouldn't necessarily want to use.
The outward L is such a solution and the cfd run was one of many looking at the crossed lift vectors as Doug correctly describes.

This though was a suitable solution for the boat in question - a good but outdated design - and despite the drawbacks would be 5 days quicker around the Vendee course.
It is still a foil covered by DSS patents.

The thing is here, when you need sideforce then you don'ty actually need that much, even in the uphill condition. The keel when canted still produces a good chunk of that, rudder contributes, hull too, and by the time you are running full cant and maybe some wster and need SF from the board, then you are also quick enough that the lift and RM generation works on the + side of the equation.

Then as you get faster and cracked off, you don't need so much SF so can rise the board and still have the lift/RM you are after. When you don't need anything at all, then the geometry raises the end out of the water so all good there - and there are other similar geometries too.

Thing is though, this is a classic case of the rules forcing a solution that you wouldn't want to consider given a free hand.


Starting from scratch, then its another ballgame altogether, you can separate lift and SF producing foils and then you end up with a very different animal....and the potential speed gains from that are quite something!

 

Open 60's with Foils

More on DSS for Open 60's: http://www.sailingscuttlebutt.com/2014/10/21/dynamic-stability-systems-revolutionise-imoca-60-class/

 

Very interesting topic. I like that the DSS system can breathe new life into older boats.

It was previously mentioned that the new IMOCA designs could afford to be narrower because DSS reduces the dependence on form stability.

How narrow could a monohull theoretically go by substituting form with foils? Has there ever been a discussion about moving a DSS box to the stern of a narrow boat to compensate for very wide transoms used now?

I think Yves Tanton drew up something like this recently. In theory, couldn't you almost retrofit the Vaka of a multi, lose the amas and replace with a combination of foils and keels?

Just curious.

 

DSS- Foil.

You mean this one or that one ?

 

It was probably the first one except neither boat looks like very narrow and I thought that was one of the benefits of DSS. What would be the effect of moving the DSS box, as in this picture, all the way aft in combination with other foils forward?