The Birds and the Boats

siimat writes: "Wow, a bat-winged sailboat! Richard Dryden has produced "a variable geometry mast and sail that can adapt intelligently to changing wind conditions, and fold away conveniently after use without the need to dismantle. The inspiration has come from the remarkable wings of bats and birds." Too bad you won't be able to buy one until later this year..."

Comments

Dinghy going upwind?

[michaelmalak]

Without a centerboard or keel, my guess is that dinghy version would be difficult but not impossible to take upwind. The windsurfing-style universal joint would allow one to rotate the sail fore and aft, which would steer the boat upwind or downwind. But even steering upwind there would be slippage downwind without a keel. A good aerodynamic sail, which this would appear to be, could overcome (outweigh) the slippage. But a keel would help, and dinghy without a keel could be frustrating.

Currious

[CaptTrips]

I found that design uncannyingly similar to a da Vinci drawing. Does anyone else notice the similarities?

how it works

[Alien54]

The concept is pretty straight ahead, but I was wondering how you operated the wing. then I saw this:

The sailboard version changes shape according to the amount of downforce exerted on the boom - in stronger winds the increasing lift generated by the rig is counterbalanced by the sailor leaning out more over the water, which in turn causes the rig to flex

Now that's clever. But that rig is going to have to be pretty strong, given the stress on the joints.

It'll never Fly

[Anonymous Coward]

Given how much "stretch" the fabric would have to have in order for the sail to keep half decent shape... this one is "not going to fly".... A far better example of efficiency are the wing sails used in Little America's Cup Catamarans.

Sail fabric needs to have minimal "give" in order to effectively translate the force derived from the wind... into a thrust vector. I see no way to adjust how much sag/bag is in this sail... and if it's a stretchable fabric... then you're going to loose much of your efficiency...

Looks cute... but the new focus for sailboards are kites... (Robby Naish is now only playing with kites)... the wind vector is both stronger and more consistent as you get off the surface and get the sail higher up... as to multihulls... the sails are getting to have higher and higher aspect ratio sails... more like the wing sails of the previously mentioned Little Americas Cup boats... and the vast monohull community... they're still so in love with wood... no .. I'll be nice.. by and large their efforts are along the lines of hull materials and shapes... as well as trying to get the least stretch in sail cloth by new materials... roller reefing is about to catch on big time for the mainsail (on the boom please and pray not in the mast)...

This is a cute experiment... but it is a evolutional dead end....

Re:It'll never Fly

[asb]

You completely missed the whole point of the rig. It is not efficiency but it's ability to automatically adjust to the wind conditions.

The reason why sails are not used in commercial watercraft is the fact that handling sails requires much more men than handling a huge diesel engine does.

One of their patent applications suggests that they are attacking this exact problem.

Re:It'll never Fly

[2b]

I missed the part on the website where he indicated that he was going after the Little AC.

I disagree that a lack of efficency spells doom for this idea. Let's face it, the Little AC, formula 400, A-class etc etc, are extremely fast and efficient but commercial disasters. Compare them to, say, a Hobie 16. Some people race them, but 90% just want to splash around and anything that makes that easier to do has a chance to succeed, even if it won't appear on very high-performance craft anytime soon.

Re:It'll never Fly

[DrSpin]

and the vast monohull community... they're still so in love with wood...

Wood is so repairable. Its fine to use high tech materials, but what happens when they break in a remote part of the world?

You may not sail to the West Indies, but the next owner might, so wood has a higher resale value.

Wooden monohulls have a life well over 60 years with proper maintenance. Glass fibre does not.

I think stainless steel's pretty cool, but in the cold climate of Northern Europe, I'm not sure cool is what you want!

Re:It'll never Fly

[mzweng]

The reason why sails are not used in commercial watercraft is the fact that handling sails requires much more men than handling a huge diesel engine does.

Hmmm... interesting. For some reason I always thought that the reason commercial ships didn't have sails was because commercial ships have hulls that are more suited to cargo placement than speed/seakeeping, requiring much more power to plow the brick of a ship through the water than sails could ever give.

Take, for instance, a tanker, where the block coefficient (the ratio of the displaced volume of the ship's hull to a rectangular block having the dimensions of the ship's length, breadth and draft) approaches 1. That's honestly a brick, and unless you want it to travel at a disgustingly slow speed, you really need more than sails.

Forgive my antagonistic, sarcastic post, but that's crap.
_________________________________________
fear the wrath of the naval architect...

Re:It'll never Fly

[Phrogz]

Sail fabric needs to have minimal "give" in order to effectively translate the force derived from the wind... into a thrust vector. I see no way to adjust how much sag/bag is in this sail

I'm just guessing based on the minimal pictures at the site, but the whole point of having a flexible, changeable frame system, as this does, is to adjust the give in the sail by changing the structure of the support geometry, not by attaching an enormous rubber sieve to a frame.

Do you see anything in the original article itself about using a flexible fabric? I sure don't...

Re:It'll never Fly

[Grab]

But most of the sailing community never goes beyond a couple of hundred miles of home, and certainly won't go outside "civilisation" (ie. somewhere with shops, or at least somewhere you could hire a car to get somewhere with shops). Most ppl just sail between marinas, where there's good facilities at each end if you have had problems in between, and where there's a coastguard to rescue you if you do get into a situation you can't handle. So most boats sold today are GRP - the benefits of wood or steel aren't worth the extra cost or maintenance problems.

The key with wood is the phrase "with proper maintenance". "Proper maintenance" on the exterior of a wooden boat involves vast amounts of work on sanding down and revarnishing every year. "Proper maintenance" on the exterior of a GRP boat is basically limited to applying antifouling and filling any bubbles in the gelcoat which do appear. A wooden boat takes an order of magnitude longer to maintain, believe me. It currently takes my parents much less time to sort out the underside of their GRP cruiser (Achilles 27 IIRC) than it ever did for them to rub down and repaint the 16-foot wooden Fireball dinghy they had before, or even the 10-foot Mirror dinghy we had when I was a kid.

For serious cruising use in the boonies, steel is usually recommended - whatever place you limp back to after grounding out, there's bound to be someone with a welding set. And steel only punctures at the place you hit, unlike wood (and GRP) which crack and splinter. But you get all sorts of condensation problems with steel, and the boat tends to get too hot in summer and too cold in winter, so you need lots of insulation.

Grab.

Alright! Finally!

[mESSDan]

Quick Robin! To the BatBoat! ;)

Holy floating vessels Batman!

[Xpilot]

I looked for "Richard Dryden" on Google but all I got were soccer sites. His name seems vaguely familiar... something to do with NASA?

Re:Holy floating vessels Batman!

[Moofie]

You're probably thinking of the Dryden Flight Research Center, where they have all SORTS of cool airplanes. And one of the best aviation photography resources on the net.

Older news (new to /. I guess)

[cryptochrome]

I heard of this a long time ago... the key thing about this design is that although it is very adaptable, easy to use, and stable, those same qualities come at a cost to performance. For speed, you gotta go with another design.

Never gonna make it

[Brento]

Sorry, folks, but as a sailor, I've gotta tell you that this bat will never fly. A big, big part of the romance of sailing is the beauty of the sailboats. Spend enough time around sailors, and you'll get to know the various boat designers and be able to recognize their work from afar.

Anything with this hideous-looking contraption on board is going to be shunned at the local yacht club, and that's where the real decisions are made. Whether you agree with the rationale or not, most sailboat buyers are going to live with their purchase for a decade or more, and they want their boat to be a representation of their own personality. Boats are purchased with 30-year loans - think about that for a second. Do you really, really want a boat ahead of its time? Nope, almost everybody wants timeless classics, gorgeous boats with clean lines.

Take a look at any marina, and you'll see what I mean. This is an industry where teak is still preferred over carbon fiber, where people talk about canvas sails, and where tradition dictates that you never change the name of a boat. A lot of people still don't even accept catamarans as real sailboats, let alone contraptions with folding bat-like sails.

Re:Never gonna make it

[Moofie]

I'm a hardcore aero geek and an aspiring sailor. I'm really looking forward to the day I can actually afford to design the boat of my dreams, and I could give a damn what those poncy jerks at the yacht club think. I'll be glad to show them EXACTLY why my boat will be funny lookin', by blowing them out of the water on the race course.

I'm not saying it will be commercially successful: Only competitively successful. : )

Re:Never gonna make it

[cnkeller]

Take a look at any marina, and you'll see what I mean.

Hmm, I would disagree. Being from the *real* sailing capital of the world, Annapolis MD, I tend to see plenty of carbon stuff at AYC (from Fahr's shop), St Francis, NYYC, Wakiki YC, etc. I've had the luxry of racing from a few of the more prestigous (snobby) yacht clubs around the country and I've seen plenty of both. Those with the money buy the latest toys (Sayonnara???) and others buy the classics. Much like cars, everyones tastes are different and usually go along with the cash flow. It also depends a lot on where you are sailing or racing. I race, not pleasure sail, so that usually dictates the latest and greatest gear. Perhaps you are visiting yacht clubs where racing isn't big?

Re:Never gonna make it

[armb]

> Boats are purchased with 30-year loans

Windsurfers, small dinghys, and sea kayaks aren't, and are among the target applications. Some windsurfers and dinghy sailers absolutely want a boat ahead of its time so long as it's legal in their racing class (for values of "ahead of its time" that mean "faster", which this might not).

If he can really make a sail that instantly reefs to best suit conditions while retaining efficiency, there might be a market. I'm dubious, but it's possible.

Then again, your arguments certainly seem to apply to rigid wingsails. Boats like
http://www.linfield-yachts.com/lnfield-yachts/ze fy r43/technology.html exist, but are hardly common.

(See http://www.baloghsaildesigns.com/pro.html for an existing "batwing" (non-folding) kayak sail. Is it really any more elegant than the new one?)

Re:Remember the Rotating Sail?

[Moofie]

The problem is that magnus effect sails (and aircraft wings, for that matter) are colossally draggy. You're looking at approximately three times the lift/drag ratio, and that's a Bad Thing. Couple that with the power requirements for spinning the drum, and you've got a really poor compromise design.

I was fascinated with this idea for about five minutes in my aerodynamics class, but the drawbacks are rather massive.

Why a bat, when a Star is just a good

[theEd]

I sail a Star boat(www.starclass.org) and this one-design class has used a flexible rig since the 1930s. The mast is extremly long and thin and tapers at the tip. The running backstays have both an upper and lower attachment and each is a adjustable so that one can change the shape of the mast changing the tension of the stays. There is also a rammer which allows one to move the mast fore/aft in the step.

Another thing is the sail needs to be cut correctly because in a situation in which one increases the bend of the mast during a heavy air condition could lead to increased fullness, which is the opposite of what one wants in heavy air. The Star main is shaped such that when the mast is bent back, most/all tension on the upper backstay. the main is "flat". As one shifts the tension from the upper to the lower, the sail is pulled in a way that increase the fullness of the main, which is better in light wind conditions. But I'm sure Mr. Dryden has thought of this.

Resistance to change...

[chazR]

...is not as strong as you think.

Otherwise, we'd all be sailing gaff cutters. The gaff rig is *much* prettier than a bermudan. Unfortunately, it's less efficient, more expensive and takes a lot more effort to use.
In the fast dinghy/sailboard arena, this could sell *because* it's new and unusual. For Eris' sake, sailboarders have been known to use dayglo pink sailcloth.

I'm sticking with my high-aspect fractional rig while the class rules require it...

Looks cool, but...

[jcr]

The only advantage this design offers is that you can increase or reduce your sail area (reefing, we call it), quickly.

Well, that's nice and all, but frankly, you don't NEED to reef a sail all that often.

This looks to me like the kind of thing someone who's not a sailor would have designed.

-jcr

Re:Looks cool, but...

[jcr]

But if you, like me, take any opportunity to go sailing - almost regardless of conditions - then the ability to reef becomes very important.

Of course reefing is important, but it's not something you need to do as often as you trim sail. When you're out in heavy weather, how often to you change how much sail you've reefed? I don't know about you, but I've rarely had occasion to reef or unreef a sail away from the dock.

-jcr