sail aerodynamics

[SukiSolo]

I have seen examples of wing sails on multihulls, but have not seen any on mono-hulls.

How about the Moths?.


http://www.yachtsandyachting.com/photos/internationalmoth/yandy56103.jpg

 

[CT249]

I have seen examples of wing sails on multihulls, but have not seen any on mono-hulls.

Wings started on monos, such as Bee McKinnon's International Canoe. It had an Austin Farrar wing before Austin started to put them on cats. There was also a wing mast Moth around 1956.

Leading edge devices of several other types were also tried on dinghies years before they were tried on multis. LF Herreshoff's Suicide class is another example from the early part of last century.

As you say, and as Mark Drela explained here, in many boats you don't want the rig with the best L/D - you want the rig with the best L. As Mark says, what counts is NOT the L/D of the rig, but the L/D of the whole vehicle, and on most monos the drag of the hull is vastly more important than the drag of the rig. Add in issues like gust response and the result seems to be that wing sails and wing masts don't normally work all that well on typical monos.

As an aside about efficiency and wings, I was using our most recent wing-mast boat today, and it reminded me once again how much a PITA our old wing-mast boat was, because the big and stiff wing created very high mainsheet loads. OK, we may have got to the windward mark a few seconds earlier with the big efficient wing mast, but overall it was much less fun than with the smaller, bendier and less aerodynamically efficient wing mast and lower mainsheet loads of our current boat. The odd thing is that some people just make up conspiracy theories (like blaming rating rules and conservatism) to explain why most sailors ignore wing masts, when the simple truth seems to be that the issues they create are normally not worth the efficiency they introduce.

 

[Gary Baigent]

Of course, all those IMOCA wing mast 60's, all those winners - so inefficient, wing masts on monohulls ... maybe you're the one with the wacko conspiracy theories, or is it just ignorance?
How about the mast evolution on the new mini Transat designs.
And not to mention the rigs on ORMA designs or the G Class multihulls?
All those guys, you know, the ones with all the records - completely off course, according to you?

 

[CT249]

That's not what I was saying, and any reasonable reading of my post would show it. Nothing I wrote indicated that IMOCA 60s, Transats, ORMAs or G Class shouldn't have wing masts.

Any reasonable reading of the post would show that I stated that big wings are faster in my old class, and also in many other classes. That's great if pure speed is what you want, but the point was that being a bit faster doesn't necessarily make them better for fun sailing or as the best rig for popular types.

I also referred to "typical monos" and the plain English meaning of that phrase does not include multis or Mini Transats, which are great boats but not typical monos.

The post also said that wing masts in some classes are not always as efficient as some claim, and that is also a fact proven by race results. The plain and simple fact is that there are many classes in which wing masts are permitted, but where wing masts have failed to go faster. That shows that some claims for their superiority (which doubtless exists in other situations) are unfounded. It's also a fact that some people claim that wing masts have been banned where they were not actually banned.

All the abuse you throw around won't change the facts, Gary. Why not try discussing the issues rather than using insults?

Read the forum rules, Gary. Personal attacks like those you so often use are not allowed here.

 

[sharpii2]

How about the Moths?.

http://www.yachtsandyachting.com/photos/internationalmoth/yandy56103.jpg

Even though those are technically monos, I class them with the multis, because they have huge righting arms which cannot normally occur on a typical fixed keel mono, even with a deep bulb and a lot of rail meat. The same goes for some sailing canoes, which also have hiking wings or boards.

BTW-IMHO, canting keel monos should be classified as multis as well for the same reason.

I suppose all of these should be classified as super monos.

And those which foil should be classified as "foilers", as they don't even sail on their bottoms.

For the sake of argument, has anyone thought of the idea of putting multiple wing sails on a boat, in either a ketch or schooner form.

The one attraction I see to wing sails is that they can be feathered into the wind--especially if they have a symmetrical foil shape--producing no lift and very little drag.

I am imagining a wing sail which has three major components: a wing, a flap, and a tail with an arm.

The flap increases the lift of the sail, somewhat making up for its symmetrical foil shape. The tail with an arm will insure it feathers completely into the wind in a storm.

 

[Doug Halsey]

For the sake of argument, has anyone thought of the idea of putting multiple wing sails on a boat, in either a ketch or schooner form.

The one attraction I see to wing sails is that they can be feathered into the wind--especially if they have a symmetrical foil shape--producing no lift and very little drag.

I am imagining a wing sail which has three major components: a wing, a flap, and a tail with an arm.

The flap increases the lift of the sail, somewhat making up for its symmetrical foil shape. The tail with an arm will insure it feathers completely into the wind in a storm.

Some examples from Marchaj's Aero-Hydrodynamics Of Sailing

 

[Gary Baigent]

quote:
"I also referred to "typical monos" and the plain English meaning of that phrase does not include multis or Mini Transats, which are great boats but not typical monos.
The post also said that wing masts in some classes are not always as efficient as some claim, and that is also a fact proven by race results. The plain and simple fact is that there are many classes in which wing masts are permitted, but where wing masts have failed to go faster. That shows that some claims for their superiority (which doubtless exists in other situations) are unfounded. It's also a fact that some people claim that wing masts have been banned where they were not actually banned."

Maybe you should re read what you have posted.
BTW, what is a typical mono in these times of radical monohull change? And is not a mini Transat 6.5m, although a leading edge class, (along with other advanced thought mono designs) still very much a "typical monohull?"

 

[CT249]

I did re-read it, and I stand by it.

What is a typical mono? Well, the normal meaning of the word is that something that is "typical" is something that is pretty normal or average of its type. Something that is in a tiny minority (like wing masted or radical monos) is NOT normal, average or typical.

The current normal mono - even the current normal production mono racing yacht - is a crewed fixed keel cruiser/racer or perhaps a sportsboat for local racing, NOT a canting or water-ballasted singlehander for ocean crossing like a Mini. Canters, Minis, and wing masted monos form a small percentage of the boats that are racing being built, therefore they are not typical in the plain English meaning of the word. Sure, they are great, but they are not typical.

The Mini is great, but only about 900 have been built over three decades or more. There are currently 5000 yachts racing under one French rating system (HN) and allegedly about 20,000 in US PHRF alone. Add in the many thousands of other yachts and it's obvious that Minis and similar boats form a tiny proportion of the overall racing fleet, therefore they are not "typical". A simple check of results and numbers shows that the vast majority of boats in every country are fixed keel cruiser/racers and older one designs, not "radical" types.

The entire Mini Transat breed (great boats though they are) are therefore much less "normal" than a single "conventional" boat like the First 31.7 (1500 built), First 210/211/21.7/20 (basically the same boat with around 2500 launched and still in production). In terms of modern designs the J/70 (750 built in a few years) would currently be easily out-selling the Mini, and the latest incarnation of the Firsts from 40 to 20 feet would probably be doing so as well.

The same thing applies in small monos - wing masts have been tried and have failed in many classes (12s, Rs, 18s, Gwens, Moths, boards, Merlins, Canoes among them) and only work well in a few.

I started building my first wingmast when I was 23. I have owned a boat in the world's most popular wingmasted crewed mono class for 20 years. I have a wingmasted multi as well. I have also interviewed people like Alex Vallings and several others who have tried wingmasts in development monos. It is not being ignorant to point out that wingmasts in monos have not demonstrated the performance advantage that some hype claims. Sure, wingmasts work well in some classes (which is why I own some) but I never claimed they didn't.

PS - Personally, I tend to think that "advanced thought" can be just as much about making sure that the sport stays simple, affordable and easy enough to interest the average person - the sort of "advanced thought" that people like Spencer had. "Average thought" doesn't have to be about adding extra complication to boats that will always be beaten by a multi.

 

[Mikko Brummer]

I think you are slipping off topic arguing what is a typical mono and what is not.

As for wingmasts, clearly CT249 has more experience & knowledge about them than most of us. Respect.

When it comes to IMOCA 60, the boat has a choice between a standard rig and a wing rig. My brother who designs these masts says the verdict is still out which one is more efficient, even for the IMOCA which is sailing around the world, always fetching, reaching or running, never beating upwind. New designs has adopted the wing mast, mostly because it has the outriggers that help sheeting code zeros and gennakers more efficiently, says my brother. The fixed rig has to have normal spreaders.

 

[Doug Halsey]

The same thing applies in small monos - wing masts have been tried and have failed in many classes (12s, Rs, 18s, Gwens, Moths, boards, Merlins, Canoes among them) and only work well in a few.

Could you please clarify what you mean by the term "wing-mast." Do you mean something like Austin Farrar's large-chord catamaran mast (shown below), or any smaller streamlined, rotating masts?

As for the Moth class : Smaller-chord streamlined rotating masts were very successful (at least in the U.S.), before the adoption of the sleeve-luff in the late 1960's. And I'm not aware of any examples of the Austin Farrar type rig ever having been tried.

 

[powerabout]

hard to believe there is any downside to a rotating wing mast if we are talking performance?
I like the no diamonds ones like on the SmartTri 40 and others

 

[Gary Baigent]

CT249, I think, is writing about small chord wing masts as on his own boats, not full wing rigs - as on C and AC Class catamarans.
Imo all rotating masts are really wing masts because they are aerofoil cross section shape, even though their chord/length may be as low as 1:3.
If not airfoil but a round tube, then that kind of defeats the original purpose of a rotating mast, may as well leave it fixed.
It appears that wing masts are, for some reason, not efficient on sailing dinghies, according to CT. Probably because they are heavier than conventional fixed rigs. But they work extremely well on larger craft; just read the history. In NZ, on monohulls (multihulls had rotating small chord, and larger, wing masts dating back to the mid 1970s) - Greg Elliott has had wing masts on a number of his designs beginning with Excess in the late 1980s.
However on numbers of wing masts I have looked at, many cannot rotate correctly - and this is a basic fault because the side staying points are at the thickest cross section of the mast and not taken from a forward facing beak, for want of a better word.
If the mast can't rotate past 35 degrees either side because the side stays bind, then that too, is near useless for going through the effort of construcing an airfoil mast. They need to rotate a lot further if you want a clean flow and feed from mast to sail. Otherwise, again, why bother having such a restricted mast, may as well stay fixed.

 

[CT249]

Mikka, I was just trying to answer the question "what is a typical monohull". Thanks but I'm no expert, just someone who has studied the history.

Gary - Yes, I was referring to wing masts not wing rigs, although our old F16 rig had a bigger than average chord - around the same as an A Class if I recall correctly. Yes, wings work well in larger boats.

Doug H; by wing masts I was referring to sections with a larger chord than the standard Moth round or pear sections. There were some larger wings tried in scows in Australia in the '50s and '60s, at least. Given that the Bethwaites were heavily into Moths I assume that they would have also at least considered wings if they were practical, as well.

Powerabout - there's a long history of wing masts in small performance monos that show that there IS a downside (in fact more than one) to wingmasts in such classes. That is why they have been tried and discarded in 18 Foot Skiffs, International Canoes, R Class, Merlin Rockets, 12 Foot Skiffs, Gwen 12s, Z Class renjollen (if I recall correctly), Cherubs, Suicides, Bembridge Redwings (I think) and other classes and types such as windsurfers.

The normal problem is the lack of gust response with a wing mast, because the thick chord means that it's hard to get the mast to bend automatically while staying strong enough to survive. Weight is also a problem. So wings have generally failed to provide enough all-round performance to be competitive. At times they have shown potential but in the end the problems are too much for them to be adopted, even when top class crews have spent several years and several different iterations. Even one of the most dedicated creators of dinghy wing masts, Frank Bethwaite, later concluded that simple non-rotating sections were better for modern assy boats.

Some have claimed that wingmasts give a 25% or more increase in lift, and a 60% decrease in drag. If they really did give such an advantage, they'd win just about every time. It's been proved time and time again that the on-water advantage, if it exists, is very marginal and that most classes lose more due to handling issues than they gain through the superior aerodynamics.

None of the above is meant to say that wingmasts don't work in certain classes, like the NS14s and MG14s with their small rigs, una-rigged Finns, or multis where many factors are different. I assume that in the Finns, the wing mast may work because the improved airflow over the mast is more significant in a una-rigged boat, and perhaps the unstayed rig and heavy, rounded hull mean that gust response is less of a problem. Mikka is clearly the expert there!

 

[brian eiland]

Conservative Sailors & Rating Rules

Everything I've seen the "aircraft theorist" write here actually matches perfectly with what actually occurs in our sailing vessels. The same can't be said of most of the amateurs who decry the rigs that work and spuriously claim that they are only used because of rating rules or tradition.

..... The odd thing is that some people just make up conspiracy theories (like blaming rating rules and conservatism) to explain why most sailors ignore wing masts, when the simple truth seems to be that the issues they create are normally not worth the efficiency they introduce.

I think some of CT's criticism is directed at me and my aftmast ideas. I have commented both on my website and on the forums here about the 'conservative nature' of the sailing community accepting unusual ideas, and the rating rules utilized in a number of instances 'outlawing' new ideas.

Most recently I was looking back over Marchaj' book Aero-Hydrodynamics of Sailing:..
...excerpt
Some readers may be interested to know that headfoils are neither new, nor revolutionary invention. They are a new answer to an old problem. According to Herreshoff's memoirs from Ref 3.29, The Common Sense of Yacht Design, W.F. Herreshoff:

A few years later I designed three or four rigs with a spar forestay, believing that by doing away with the backstays, a saving in wind resistance could be made, but none of the owners of these yachts liked or kept the spar forestays, and gave them up. The spar forestay is not an invention of mine, but has been used in central Europe for thirty or forty years, and there is probaby something in it, although the revolving streamline ones are my invention.

In 1925 I was much interested in schemes for reducing the wind resistance of rigs when closed-hauled. I was working for Starling Burgess at the time, and perhaps because he had been an aeroplane designer we were over wind resistance conscious. At any rate I was allowed patents on a double luff rig with revolving or oscillating mast. This scheme was developed principally to do away with exposed wires and an R boat. I believe it did away with about 200 running feet; in other words, there was no headstay, intermediate shrouds, upper shrouds or backstays.

The R boat Live Yankee was designed to come out with this rig, but the regatta committee of the New York Yacht Club, hearing of it, promptly passed the rule prohibiting revolving masts, double luffed sails, and similar contrivances.

 

[brian eiland]

Another posting related to 'rules' limiting advancements with the unusual....

http://www.nytimes.com/1988/07/31/sports/yachting-british-can-t-race-but-they-ll-watch.html

The New York State Supreme Court ended Britain's plans for 1988 by ruling last week against the Royal Burnham Yacht Club, Blue Arrow's club sponsor. The club aligned itself with the San Diego Yacht Club, the America's Cup defender, in asking for recognition as a challenger. Redfern said the syndicate planned to stay involved in cup campaigns at least through 1991. The group's major financial support comes from Blue Arrow, an international employment agency, and de Savary.

http://www.boatdesign.net/forums/multihulls/historical-multihulls-42019-71.html#post751240