Absolutely Open 100sqft upwind sailing craft

Maximum sail area, say, 100 sqft upwind, and that is all !

 

Oversized Moth foiler will win over about 8 knots (or less) until about 25. Just a wild guess.

 

Would a 100sqft flying Moth be a winner...

against a 100sqft C class-like catamaran , on an Olympic or America s cup course?

 

It certainly seems very possible, looking at comparable boats, that the Moth would win.

I race against the guys who have won 3 of the last 4 A Class worlds. The 18'/5.5m long A has (if I recall correctly) 170 ft2 of sail and weighs 75 kg all-up. It is probably THE most efficient of catamarans and As regularly beat Tornadoes in light winds until Tornadoes got spinnakers.

A cat with 100 ft2 would be much slower than one with 170 ft2. It would have to be shorter to reduce wetted surface accordingly I assume. C Class-type wing rigs are efficient, but there is evidence that they are not SO efficient that a 100 ft2 wing would beat a 170 ft2 A Class rig.

The A rig is about 30' tall, has a carbon wingmast, very high aspect. It's a nice rig. In 18 m2 and C Class the wing masts have not always dominated the "soft" rigs. Wings have been tried (years ago) in Moths and 10 sq m International Canoes with no success. In a small cat, the pitching moment of the inherently heavier wing would be more of a problem than in the C Class.

The 11m2 surfcat types and the 14 sq Nacra tend to sail best downwind going quite square. They are sometimes surprisingly fast compared to the efficient high-aspect cats like A class and Taipans which have to tack downwind. The Nacra 14 sq isn't a bad boat and it's hard to see how a 10 sq cat would be a great deal faster than the Nacra 14sq (judging by the way the Nacra 16 sq, 5.8 and 14 compare to the A class etc) .

So our 10m2 cat will have to run fairly square, with the rig at very high angles of attack. That is very bad news for a very high aspect rig and very bad news for a wing sail AFAIK. I assume it will need zap flaps etc which all increases weight.

The Moth is inherently lighter (28kg all-up) and has less wetted surface. The world Moth champ (on a foiler) claims to often be beating the A Class cats upwind and around the course. Even conventional Moths are great upwind performers, able to beat boats like the world Flying Dutchman champion in open water and moderate winds.

 

Downwind, one should use some short of spinnaker/gennaker/kite I suppose, to compensate the high aspect ratio of a wing sail. We are talking about a really open class here, but we could accept an additional downwind maximum sail area limit too, let us say 100 or 200 sqft more.
Many people have tried wing sails on A class cats. I do not think we have reached the end of the line in C and/or A class wing sail development yet. I wonder if one could control excessive pitching forced by these heavier rigs with the help of some sort of horizontal tail fins.
If we use a beamier cat than the A cat, I thing that we could also go a little longer and a little faster, in moderate winds, with an effective 100 sqft wing sail. Hull foil is a beautiful way of achieving speed, but hull length is beautiful too !

 

Have there been many experiments with solid wingsails in As? I heard Mitch Booth tried one but I wasn't sure whether that was actually in an 18sq and someone had the story wrong. While we may not have reached the end of development of wingsails, development of foilers that work on a racecourse has only really started.

Beam means extra weight....what sort of lift/drag improvement does a wingsail create? Would it be enough to compensate for the loss of about 50ft2 of sail?

I forgot to mention I assume a monofoiling windsurfer may faster than a big Moth-type foiler, simply because a non-foiling windsurfer (longboard) is faster than a non-foiling Moth and the two are similar in most dimensions.

Actually maybe I shouldn't be talking "big Moth", because a 10m2 + spi Moth-type boat is very much what the Assymetric International Canoe would be if it didn't have to conform to rather old rules on hull beam and weight. Say "foiling AC" instead.

 

<<While we may not have reached the end of development of wingsails, development of foilers that work on a racecourse has only really started.>>
Nobody can deny that, and it is a pity that foils are expelled from A class and the other development classes as well. But why limiting the length and the beam when you have a maximum sail area? The M-18 is beamier than the Marstrom A class, isn t it? Beam adds weight, that is true, but also increases the righting moment to a point where a hull can stay clear of the water through most of the race course. Combined with the MUCH greater L/D ratio of a wingsail, a beamier and perhaps a little longer 100sqft wingsail cat would be a tough competitor to A class and bifoilers and trifoilers Moths.

 

Some guidelines

I think this could be much fun.
Although you might consider stndardizing the sail area at another place in order to get some current comparisons and also to get some benefit of current sail design on the cheap.
Two sail areas seem logical.
8M^2 which is the SA of a Moth.
Or 10M^2 which is the SA of an International Canoe.,
The problem with that of course is that both the Moth and IC are devilishly quick and fairly highly developed, so it is unlikely that one would beat upon them right out of the box and people may get discouraged. Also they are fairly pricey.
Otherwise, I think it would be good to get some agreement on what the test course would look like and some idea of the client population.
Suppose we said "Harry Anderson course (Also known as a "Figure 4") and everyone who brings a boat sails every boat." This means that the boat has to sail on every point and a really good sailor couldn't bring an extraordinarily difficult boat ( like a foil borne Moth or super skinny IC) and walk away with it.
Would make us target normal skill levels....
SHC

 

<<everyone who brings a boat sails every boat>>

Sounds fair and nice, but everybody must trust everybody else on a first time ride upon a not so cheap experimental craft...It would be really sporty if it could happen someday.
I think that what sailors with "normal" skill levels need is a beamy craft where the transverse balance and righting control of the boat is easier. On the other hand, see what happened to the beamy Macquerie Innovation while some people were happy riding unifoiler Moths...

 

Qualification

I think designing a boat,building it and bringing it to an evaluation event would pretty much qualify you to take a ride on anyone elses boat. Yeah, people would have to trust each other, but it would also tend to drive people toward user friendiness instead of extreame solutions.
I just think there is such a range of skills necessary. For example, I have won International Canoe World Championships and happily sail an A Class catamaran, but I would probably flail around in a foil borne Moth for quite some time. So its kind of key to focus on an intended skill level and then optimize performance with that population in mind.
Another way of qualifying people: Laser Masters. These are middle aged people with what would have to be regarded as very good small boat skills, but certainly are not Rohan Veal. Neither are the completely clueless klutzs who havent hiked in their lives.
Other options?
SHC

 

What ever happen to rigid foils that split in two like a clam for downwind performance?

 

clams

Gonzo,do you mean they become lifting foils when they split? I can envision something like that: a daggerboard where the lower 18" or so is split and opens up downwind but I've only heard about something like that once before-where did you hear/read about it?

 

Having only skim-read the thread, I'm not certain, but I think Gonzo is suggesting a solid foil (wing) sail, that splits open for downwind use...

 

clams

Thanks, Will! I bet you're right. It seems to me if a boat was using a wing sail to start with it might be capable of sailing fairly hot angles downwind and wouldn't need to open up for improved performance.

 

Yes, I am thinking of the halves opening up and doubling the sail area. It could solve the problem of not having a spinnaker.