Kites

[ath]

Out of pure curiosity, is anyone experimenting with or using some form of kite down wind?

Some years ago I had read about a ULDB that had used a kite similar to a skydiving shute (rectangular) set around mast height or higher and attached to chain plates on either side of the hull midway between mast and bow. I think that a lighter line was attached to the middle of the kite as it collapsed the shape and made it easy haul in with a windlass or by hand (maybe not by hand since it was a lot of line).

But I have never seen this developed. On first thought, I would think that it would take advantage of the wind gradient effect in some areas and in lighter conditions and in heavier conditions, with a smaller kite, would it not help to lift the bow slightly and help planing for certain flatter monohulls? Is it that they are simply too unmanageable? I wonder what happens? Would the kite stay aloft or does it lay low and pull out to the front of the boat? Couldn't it be designed to stay lifted at a certain angle to the bow?

I searched the forum and didn't find anything... just curious

[Sketch]

Check out www.kiteship.com

The video streams are pretty cool

[ath]

Ha. Interesting. Makes perfect sense.

[Skippy]

Why only downwind? :)
Here's a discussion of kites: ISAF vs KITE Sailing (http://www.boatdesign.net/forums/showthread.php?t=6641&highlight=kite)

[yipster]

I searched the forum and didn't find anything... just curiousallways good to do! but when i type "kite" in the search field onder the search button i get 2 pages with dozens of kite related threads. hope this helps.

[daveculp]

Why only downwind? :)
Here's a discussion of kites: ISAF vs KITE Sailing (http://www.boatdesign.net/forums/showthread.php?t=6641&highlight=kite)

There are dozens of types of kites, Skippy, just as there are dozens of types of sails. Some are simple, cheap and have limited performance envelopes, and some are complex, powerful and expensive.

I could fairly easily design and implement a rig-replacing kite for your boat, which would do everything the current rig can do--and more. Trouble is, it would cost almost as much as the rig it replaced--i.e.: many thousands of dollars--not counting the R&D work to get it right.

At KiteShip we have been doing just this since 1978. We have found that sailors--as a market--aren't quite ready to chuck their entire existing rigs over the side and pay for a second, free-flying one. It's a cost entry issue, do you see? In the meantime, we have found that a simple, inexpensive replacement sail for existing spinnakers--using all the boat's existing rigging and sail handling equipment--and costing about the same as an ordinary spinnaker--has a ready market, today.

OH, and did I mention, they are perfectly legal under ISAF rules? There's a storm coming, but, according to the ISAF Equipment Rules of Sailing, OutLeader spinnaker replacement kites are perfectly ordinary asymetrical spinnakers; they were carefully designed to be so. Rules such as "kitesails not allowed" are meaningless in the context of OutLeader kites and ISAF.

You may be ready for the whole shebang (rig replacement kites)--please tell us if so. The first one's gonna cost a couple of hundred throusand dollars, but if we can spread it over an entire market...

Cheers,

Dave Culp
http://www.kiteship.com

[FAST FRED]

Seems like there would be a good market as a get home for the power boat folks.

Most are far to old , ignorant ,lazy or just predjuced to contemplate a motor sailor , but the options for realistic get home are not great.

Somthing to do 3/4 hull speed over a 180 deg choice of heading should be enough.

FAST FRED

[CT 249]

Dave, how would a "rig replacement kite" work well offshore in light and sloppy winds????? You know, the annoying 0-2, circling the compass for a couple of hours sort of stuff.

Just curious.

[daveculp]

I dunno, Chris. How well does YOUR present rig work under these conditions?

Serioiusly, there are at least 3 answers, off the top of my head, for kites capable of "flying" in 0-2 kt winds. Each of them would offer more performance than a masted rig under these conditions--and each would cost more than you're willing to pay...

Dude, open your eyes. All the answers aren't on the chandler's shelf, nor in the local OD class regatta. Sometimes you need to look outside the box.

[daveculp]

Before you ask, yes, I'm willing to seriously "blue sky" about how sailing MIGHT be improved. I'm not particularly interested in throwing out ideas for conservative laggards to shoot down. Decide which shoe fits and get back to me.

Dave

[CT 249]

Dave, if you recall during your trip out here I asked whether about coming out on two kite boats. Surely that's not much evidence of being bigoted. Nor is it easy to see see exactly how owning two development-class boats and two OD boats is evidence of an OD mindset - apart from the fact that racing in a 100 boat OD regatta is more fun than sailng in a 7 boat development-class title.

My mindset is that sailing is declining in many ways and the classes that are surviving best are fairly simple, medium to slow, fairly economical one designs. The expensive fast development classes are often doing badly. Developments should surely been thought about, queried, studied in that light.

Surely the most important thing is "development" that increases and maintains popularity AND tries to improve the health of the development classes that remain. That may be a different goal to just hoping to go half a knot faster; if speed was the issue A Class cats would be more popular than Hobies, and International Canoes would be more popular than Lasers. They aren't.

And OK, kites may well be the answer in more ways than speed. I never said they weren't, but what's wrong with asking how they perform in conditions where spinnakers and kiteboard kites don't really go all that well?

My rig works pretty well in those conditions, which is very important because performance those light and sloppy conditions (too light to support a spinnaker and the sort of stuff that drives you to short-foot windseekers) can of course make an enormous difference. Surely it was reasonable to ask whether your proposed rig could work in such conditions, as a boat that stops each time the wind drops loses many, many miles in "holes".

[cristofa]

Backalong in '82, I worked on an interesting kite project ... I designed and built a dedicated kite boat to take part in the 'Mini Transat' race. The kite (which was produced by someone else) was D shaped in plan, aerofoil in cross section and filled with helium. The whole project became feasible when kevlar line (with its very high strength to weight ratio) became generally available.

The 6.5m boat was very light and, to exploit the kite's advantages, the design departed significantly from conventional sailboat practice; in fact, the low-slung, mast-free, planing hull looked more like a powerboat, than a sailboat.

It had a working (coverable) cockpit up front for deploying the kite, but the boat was 'driven' from a comfortable (car) seat, under cover, amidships. A dagger board provided lateral resistence and a 1.2m horizontal arm, rotating about a point just ahead of the dagger board, directed the lines to the kite side of the boat.

The 'working' kite was a mere 5 square metres, so it was easy to handle at sea level. It was generally flown on a 70-100m lines where it provided plenty of power ... you don't have to go very high to see a substantial increase in wind speed. Reefing was achieved by simply shortening the lines.

Once I got the hang of it, driving the boat was surprisingly easy. Without any control input, the kite would sit quietly aloft, producing no drive. Swing it down, and off you go ...

Lots of people could NOT get their heads around how you could sail a kite-powered boat to windward but, in fact, it pointed very well. And it worked very well indeed too ... most of the time.

I didn't have a speedo on board during most of the trials but, at times, it felt extremely fast, planing with ease. It was also possible to engage the self-steering and 'set and forget' the kite for passage-making.

The absence of heeling took a bit of getting used to and, with no mast/sails to bury the bows, and a lift component from the drive, the boat felt uncannily light and quiet.

There were two problems which, together with the usual 'insufficient funds', prevented the boat from entering the race. One was annoying, but not serious. On a damp drizzly light wind day, enough moisture would settle on the kite to sink it to sea level and deprive the boat of power. The other problem was much more serious though ... it occurred twice and was due to the 'grippiness' of wet kevlar line at the time. If the control lines crossed, they could lock solid and I would get what I called a 'twister' ... the kite would begin to rotate increasingly quickly, generating a whole heap of unwanted power along the way! As soon as it happened, I'd have to start the outboard and motor flat out towards the kite to relieve some of the pressure, while I frantically winched in the lines ... I could have 'cut free', of course, but couldn't bear the prospect of losing kite or line.

The boat did amply demonstrate the significant advantages of kite power, though, and also the need for further development of the kite. It's disappointing that there's so little work being done in the field.

atb ... Christopher

[FAST FRED]

For the anoying 0 to 2k winds the only thing I have found that works is a BIG fully battened main.

The area is there , with a "proper" airodynamic shape , just waiting for some push.

They can be vanged down hard , and arent too noisey while they wait at zero wind in a slopy sea.

FAST FRED

[daveculp]

Backalong in '82, I worked on an interesting kite project ... I designed and built a dedicated kite boat to take part in the 'Mini Transat' race. The kite (which was produced by someone else) was D shaped in plan, aerofoil in cross section and filled with helium. The whole project became feasible when kevlar line (with its very high strength to weight ratio) became generally available.

I would be VERY interested in learning more about this boat. I receive inquiries from Mini Transat guys most every day; if I htought there was a potential for a purpose-built Mini boat, I'd jump on it.

The 6.5m boat was very light and, to exploit the kite's advantages, the design departed significantly from conventional sailboat practice; in fact, the low-slung, mast-free, planing hull looked more like a powerboat, than a sailboat.

Helium inflation is one of the 3 light-wind methods I was speaking of. Not only does it make the rig truly self-supporting (and maintaining its airfoil shape to instantly take advantage of the first and lightest zephyr), it also lets you maintain the kite at 100' or so altitude--typically above the worst of the "light variables" which plague rigs down on the surface.

The 'working' kite was a mere 5 square metres, so it was easy to handle at sea level. It was generally flown on a 70-100m lines where it provided plenty of power ... you don't have to go very high to see a substantial increase in wind speed. Reefing was achieved by simply shortening the lines.

Intertesting about the "reefing." 5 meters is really pushing the minimal size capable of buoyancy with helium; both of your difficulties have been effectively solved; Modern kites are capable of depowering substantially, so can be made a good bit larger--with sufficient buoyancy to carry the condensate weight which defeated you. Also, spectra line is an order of magnitude "slipperier" than kevlar; it is not uncommon for competition fliers to fly with 8-12 full wraps in their lines and several wraps are almost not felt at all, even with quite large kites.

Lots of people could NOT get their heads around how you could sail a kite-powered boat to windward but, in fact, it pointed very well. And it worked very well indeed too ... most of the time.

Nothing has changed; it is still easy to get to windward, and people still do not believe it possible. There are real limitations with "modern" kites, only in that most laypeople regard windsurf kites as "state-of-the-art." These kites are highly specialized to have high drive and be easily water-launchable--not for windward ability or efficiency. A purpose-built helium inflated kite would be quite different, as you will recall.

I didn't have a speedo on board during most of the trials but, at times, it felt extremely fast, planing with ease. It was also possible to engage the self-steering and 'set and forget' the kite for passage-making.

This is perhaps one of the best attributes of HE filled kites, but we still find strong opposition to "cheating" with buoyant kites. Fact is, helium buoyancy cannot drive the boat. In fact, many years ago (about the time you were experimenting with it), the precurser to the WSSRC ruled helium-filled rigs to be perfectly legal for speed records.

The boat did amply demonstrate the significant advantages of kite power, though, and also the need for further development of the kite. It's disappointing that there's so little work being done in the field.

Exactly my feelings, Chris.

Dave Culp

[daveculp]

Dave, if you recall during your trip out here I asked whether about coming out on two kite boats. Surely that's not much evidence of being bigoted. Nor is it easy to see see exactly how owning two development-class boats and two OD boats is evidence of an OD mindset - apart from the fact that racing in a 100 boat OD regatta is more fun than sailng in a 7 boat development-class title.

Here you demonstrate the very thing you deny. ;) This is an opinion, not a fact; I personally would prefer the 7-boat fleet; if I had the opportunity to break through some tradition or other with new technology. Different boats--different long splices.

I don't believe I claimed you were bigoted; apologize if I did. I did fly 8000 miles to your home waters, offered half a dozen invitations (not 2) to take you kite sailing. It was a shame we could not quite put it together... We still have a willing representative in Australia and 3-4 demo kites here and there. Contact Rob Denney for a demonstration: proa@iinet.net.au

My mindset is that sailing is declining in many ways and the classes that are surviving best are fairly simple, medium to slow, fairly economical one designs. The expensive fast development classes are often doing badly. Developments should surely been thought about, queried, studied in that light.

Surely the most important thing is "development" that increases and maintains popularity AND tries to improve the health of the development classes that remain. That may be a different goal to just hoping to go half a knot faster; if speed was the issue A Class cats would be more popular than Hobies, and International Canoes would be more popular than Lasers. They aren't.

I presume, then, that you drive a Ford sedan, and have little use for the odd Aston Martin; after all, it is "fact" that the most popular sedan is the best...

And OK, kites may well be the answer in more ways than speed. I never said they weren't, but what's wrong with asking how they perform in conditions where spinnakers and kiteboard kites don't really go all that well?

My rig works pretty well in those conditions, which is very important because performance those light and sloppy conditions (too light to support a spinnaker

Again, I think you answer your own question, at least regarding spinnaker-replacement kites; they will not excel in places where spinnakers won't work either.

Then again, the genus "kite" of which OutLeader spinnaker replacement kites are a single species, offer a huge set of potential performance--which includes continued drive in sloppy light and variable conditions.

Cheers,

Dave Culp

[nero]

cristofa

Do you have any photos of the kite and boat that you could post?

thanks

[cristofa]

nero

That would be delving the archives ... I'm afraid I don't remember what I have, but will have a look.

Christopher

[Doug Lord]

Christopher, that was one of the most interesting accounts of kite sailing I have ever read; thanks! I've never read about using helium in a kite which seems positively brilliant.
Dave or Christopher: any idea what a helium filled kite designed for high performance would cost for a 16' lite weight boat?
How big a problem is helium leakage?

[cristofa]

Doug

I haven't done anything on kite boats since that time, but I strongly suspect that what you are after does not yet exist ... so cost doesn't come into it.

We used a thin, extremely tear-resistant, polyurethane film for the kites; this contained the gas remarkably well.

Christopher

[daveculp]

Would love a photo of the boat (maybe drawings??) I wonder if it might be re-invigorated for its original purpose? There is much interest in kites for Mini Transat boats.

Did you find that the kite was more or less de-powered when brought overhead? How little was "depowered"? 90%? 75%? You mentioned "reefing" via shortening the flying lines. Did you experience this, or was it just planned? What ration of "depower" could you achieve via altering altitude? (25%? 50%? more?) How long of lines could the kite loft with its buoyancy?

Thanks!

Dave

[cristofa]

I will see what I can find in the way of photos this weekend ...

Thinking about my response to your next question, I'm not sure I can explain what I experienced. Max trial's windspeed, BTW, was 20-25 mph.

Deploying the kite, I would fill it and let it float straight up. While the kite sat aloft there was no drive from it and the boat would remain stationary. By the same token, centralising the kite controls while sailing would allow the kite to float up, and the boat would come to a standstill ... this meant that I could 'drive' the boat into the harbour, let the kite go, and walk forward to pick up my mooring. I suppose that the horizontal force from the drag on the kite is very small in relation to the predominant vertical force.

I certainly did experience the 'reefing' effect of shortening the line. The lines were 100 metres long. Judging by what was left on the spool, I guesstimate that I normally sailed with 75 - 100 m of line. Strange, I never measured the elevation of the kite in sailing mode, but I would guess it was about 30° ... which puts the kite at 50m above sea level in a good clean airstream. You will have better access to wind sheer figures than I do, but the windspeed falls dramatically as the height decreases. (Wind direction also changes more than I was expecting.) 5 square metres at sea level is about right for a storm jib ... up yonder it was plenty!

Except in drizzle, the kite could lift the 2 x 3mm x 100m Kevlar lines OK.

atb ... Christopher

[Kiteship]

Except in drizzle, the kite could lift the 2 x 3mm x 100m Kevlar lines OK.

Whooee; that's almost 7.5 lbs of kevlar--even before it gets wet. Likely more than 10 lbs wet. 50-80% more than spectra, but of course, we didn't have spectra back then... ;-) (spectra's specific gravity is about 65-70% that of kevlar, plus it is hydrophobic; doesn't wet-out. Unlike Kevlar...)

Since that kite weighed no more than 3 lbs; that's a lot of lift. Let's see; 5.5 kg including lines, means some 5.5 cubic meters volume of helium in the kite--that's one heckuva lot, in a 5 meter kite! (I'm guessing you were getting some pretty good dynamic lift for the second half of that 100 meters!)

Dave

[cristofa]

spectra's specific gravity is about 65-70% that of kevlar, plus it is hydrophobic; doesn't wet-out. Unlike Kevlar...
... that would certainly have been very handy, and would have solved the project's biggest problem.

I'm guessing you were getting some pretty good dynamic lift for the second half of that 100 meters!
... that was undoubtedly the case.

Sorry I haven't had a moment to dig for pictures, but I have not forgotten.

atb ... Christopher

[CICCIO]

may be small kites would be usefull for emergency propulsion on motor/sail boat broken or emergency raft, they would be not too mauch expensive , and wold give the possibilty of moving a bit with some wind, don't???
cheers
Francesco

[cristofa]

Francesco

may be small kites would be usefull for emergency propulsion on motor/sail boat broken or emergency raft, they would be not too much expensive , and wold give the possibilty of moving a bit with some wind, don't???
... I entirely agree. Keith Stewart, who developed the Kite I used, tried to market the 'Stewkie Rescue Kite' for just that purpose. It was inflatable, folded up very small, and incorporated a radar reflector ... it should have been a standard accessory in every lifeboat. I never understood why that product was not successful.

atb ... Christopher

[CT 249]

Here you demonstrate the very thing you deny. ;) This is an opinion, not a fact; I personally would prefer the 7-boat fleet; if I had the opportunity to break through some tradition or other with new technology. Different boats--different long splices.

I don't believe I claimed you were bigoted; apologize if I did. I did fly 8000 miles to your home waters, offered half a dozen invitations (not 2) to take you kite sailing. It was a shame we could not quite put it together... We still have a willing representative in Australia and 3-4 demo kites here and there. Contact Rob Denney for a demonstration: proa@iinet.net.au



I presume, then, that you drive a Ford sedan, and have little use for the odd Aston Martin; after all, it is "fact" that the most popular sedan is the best...



Again, I think you answer your own question, at least regarding spinnaker-replacement kites; they will not excel in places where spinnakers won't work either.

Then again, the genus "kite" of which OutLeader spinnaker replacement kites are a single species, offer a huge set of potential performance--which includes continued drive in sloppy light and variable conditions.

Cheers,

Dave Culp


Your right, it was merely an opinion (albiet a very common one).

I didn't say you offered me just two invitations to sail the kites, I said I asked about getting out on two boats. I'm also sorry I couldn't make it out on a kite, after the big boat fell through I decided to sail RD's proa but it broke before I could. The A10 schedule didn't fit mine. I would still like to try both proa and kite (being a proa fan).

Don't reckon the Ford is "better" than the Aston Martin as a car - but surely it demonstrates that if you want something that is popular the simple, cheap, no-hassle reliable option is the one to take. Where would be motor industry be if all they tried to promote was Aston Martins, and they told buyers that Corollas and Ford sedans were old-fashioned crap?

I'm NOT saying kites are an expensive hassle, by the way. It'd just be interesting to streamline the way to introduce ideas like the kites, without bagging the existing sailing scene. That's all.

[daveculp]

Don't reckon the Ford is "better" than the Aston Martin as a car - but surely it demonstrates that if you want something that is popular the simple, cheap, no-hassle reliable option is the one to take.

A complete (basic) kitesurf setup costs something like $1400 (US). Check out www.zeroprestige.org for doing it for half that. Kitesurf setup fits in the boot of any car, can be backpacked across miles of beach if that's all the sailing venue you have. What could be cheaper, less hassle or more reliable? Take the dipshit factor of some of the bozos out of it and it's pretty safe, too.

I'm NOT saying kites are an expensive hassle, by the way. It'd just be interesting to streamline the way to introduce ideas like the kites, without bagging the existing sailing scene. That's all.

Chris, there are a lot of OD's that don't allow spins; also not carbon, some even no fiberglass. Kites aren't going to ruin your OD experience--we aren't looking to break into OD classes in the first place. We're looking to put kites on older boats, so called "non-competitive" boats (like the A10). Kites can do more to make "old" boats competitive than anything out there. More bang for the buck, too. They can put the fun back into sailing; the "Oh sh*t, we've never gone this fast!"

In the meantime, guys in multihulls and state-of-the-art boats (AAPT, Cone of Silence, etc) are taking a look. It's for the fun, my man. Not to ruin your day. Give it a try--call Rob Denney.

Dave

[rob denney]

G'day,
No need to call me Chris, here I am. I will be in Sydney in the next month or so, but meanwhile there are kites at Pacific Sailing School (J24s) and on XL2 (38' cat). Pretty sure either would take you for a spin if you provided lunch. There is also a 130 sqm demo kite at Coffs Harbour. Organise a boat within an easy drive of there and we can take you for a spin.

This offer applies to anyone interested, not just Chris. I also have my 40 sqm here in Perth. The winter project is learning to fly it singlehanded from my 120 kg 7.5m proa. Anyone wanting a go, let me know.

regards,

Rob

[daveculp]

For the anoying 0 to 2k winds the only thing I have found that works is a BIG fully battened main.

The area is there , with a "proper" airodynamic shape , just waiting for some push.

They can be vanged down hard , and arent too noisey while they wait at zero wind in a slopy sea.

FAST FRED

I think you are right, Fred. A sail which is self-supporting and, as you say, "just waiting for some push" is surely the best way to deal with 0-2 on conventional boats. Chris 249 seems to agree with you as well, if I'm not putting words in his mouth

I'd love to build a "wind finder" kite for these conditions; rigidly inflated with helium, flying 100m or so above the waves, sitting quietly above the slop and surface turbulence.

As Christofa says, a kite such as this is rarely becalmed and will keep the boat moving in wind you cannot feel on the surface. A couple of questions:

Is it the consensus that a kite like this should/should not be "legal" for sailboat racing? Keep in mind that helium lift cannot develop forward drive, so isn't "cheating", at least according to the rules of physics (it's been ruled legal for speedsailing by WSSRC, for instance), but that such a kite will "obsolete" many boats.

How would readers feel about the cost and complexity of such a solution? (cost maybe $100-200/sq meter; complexity involves wrestling helium cylinders into/off the boat (or building them in), also wrestling with a big inflated kite on the foredeck, perhaps in a rising wind. We'd include some "trick" launch/recovery equipment/methods, but the basic facts remain--it's big, it's on the foredeck, and you've got to muzzle it.

This sounds like a potential solution for cross-ocean "open" type racing--and for "painless" cruising with smaller kites. Will cruisers pay this kind of price and will racers put up with the hassles?

Yeah, I'm doing market research here. Your opinion counts. Thanks for all replies,

Dave Culp
KiteShip

[skinny boy]

Dave, I think there is too much room for abuse to have a helium kite legal for racing. Self supporting and just starting to roll it with the waves a bit and see if you can generate some apparent wind across it by trimming it back and forth and oops now we have lift being generated. Sitting out alone or at night there is just another reason to push the kinetics rules.

[daveculp]

Hmmm, The WSSRC apparently disagrees with you on this, from a physics POV. Also, are you suggesting that conventionally-rigged boats *aren't* tempted to abuse kinetics rules at night? ;-) Or that current rules--and Corinthian spirit--are not sufficient to stop either kinds of boats' breaking rules?

Dave

Hey, let's start a "pumping" thread. I got lots of ammo for one of these. Like, how about building a "self-pumping" rig, which uses wind power to pump the main and jib. You lose because of the energy taken to "auto-pump", but you gain from the pump. Physics says there'll be a net gain... Legal? Illegal? Cheating? You be the judge...

[Paul B]

..how about building a "self-pumping" rig, which uses wind power to pump the main and jib. You lose because of the energy taken to "auto-pump", but you gain from the pump. Physics says there'll be a net gain...

Really? Whose physics? Energy out exceeding energy in? Sound like you have designed the perpetual motion machine. And they said it couldn't be done...

[skinny boy]

So you ask for an opinion and then try to argue about it.

I don't care what WSSRC says. I don't care what you say. I think kites are stupid. If they were so great they would be on all the new boats. The reality is kites have not proved out to be anything other than a niche fad that will never find a home in true racing.

As I said it is another reason to push the kinetics rule, not that it is the ONLY reason. Don't ask for opinions if all you want to do is argue. I don't find it constructive to have to throw around huge generalizations like the above. However it seems that is what you were looking for so now you have so now you can go away.

[Paul B]

I think kites are stupid. If they were so great they would be on all the new boats. The reality is kites have not proved out to be anything other than a niche fad that will never find a home in true racing.


Twenty years ago people said the same thing about Assymetric Spinnakers. Now all the new boats use them. In fact, "single luff" spinnakers were not allowed under most racing rules, just like kites today.

I have yet to see a boat flying a kite, and have yet to see any good race result based on someone using one. There seem to be some real challenges in using them in a tight bouy race. But times may change, development will probably continue, and maybe twenty years from now everyone will be using kites.

I wouldn't bet on it. I also would not have bet on all new Jboats having prods and A-Sails back when we were sailing the first J24s either.

Maybe the proponents of kites need to reel in the rhetoric a bit until they prove something in boat types that most of us are familiar with. I still use a Symmetrical Spinnaker and don't feel it is obsolete just yet.

[Doug Lord]

In the dark of night in the middle of the ocean if you're going to cheat there is no one to stop you. You can wag your canting keel if it's fast enough or just start the engine.Sailing is not for cheaters and technology shouldn't be limited because poor excuse for a human being might violate the rules. Go Dave!

[cristofa]

If daveculp comes across a bit heavy at times, it's probably down to a passionate believe in a product that moves sailing evolution forward a notch, and a frustration at the the sailing world's extraordinary resistance to change.

I suspect that kites will not be used in normal racing to begin with simply because the 'rules' so successfully stifle progress. Kites need a lot of development before they can become an everday sea-level sail substitute, but they do have substantial advantages and, in due course, someone will produce a fully sorted rig which will probably be used initially for ocean passage-making. Then word will get around ...

I don't race sailing boats, and don't know what the 'kinetics rule' is, but in a real kite powered boat, when you 'sweep' the kite on a broad reach in a stiff breeze, the speed you get is just enormous grin ear to ear FUN!

atb ... Christopher

[cristofa]

Now that IS interesting!

I have just read in our local paper that ... "Dom Mee will officially announce today that it is his intention to traverse the North Atlantic from St Johns, Newfoundland, Canada using the Worlds first ocean going Kite Boat. He is expected to arrive into Exmouth, Devon, anywhere between thirty five and seventy five days later." You can read all about it on his website:-

http://www.dommee.co.uk/pgs/news/news-room.html

And who do you think is supplying the kites?!

In politics and business you are obliged to declare an interest ... on internet forums I guess it's just down to plain good manners. But I now understand why you were so keen to pick my brains on my ocean-going kite boat, Dave.

I wish Dom Mee all the luck in the world, and believe he might need it. I thought that at 22' 3", my boat was decidedly on the small side ... I can't begin to imagine why Mee would choose to attempt this trip in a craft measuring only 14'! I am also intrigued how he will fly and control a kite from his boat, though, as it seems to be lacking features that I would have thought were important. Oh well! Pity he doesn't have some video clips (or even photos, come to that) of his craft in action.

For those who are curious, I have found some pictures of my boat ... unfortunately, the only ones of the boat under 'sail' out in the bay were taken by someone else, and I can't get hold of him.

pics 1 and 2 show fitting out ... I used the plywood cover during trials pending the arrival of a Lexan-windowed cabin top. pic 3 shows the boat under way in the harbour ... I was sitting on the floor inside flying the kite through its built-in control system. (it's a pity the guy standing up didn't stand in the middle and ship the boat:). pic 4 is on the quayside after a trip in the bay ... 3 an 4 show the small, 2.5sqm kite which I used to get the hang of the controls.

atb ... Christopher

[nero]

thanks for posting the photos.

Kite has a different shape than I imagined.

Did you have a big bow wave with that round bow? or does the kite keep the bow up?

[daveculp]

Now that IS interesting!
http://www.dommee.co.uk/pgs/news/news-room.html

And who do you think is supplying the kites?!


Try here: http://www.kiteship.com

Pity he doesn't have some video clips (or even photos, come to that) of his craft in action.

There will be. The boat was only launched this week--they've been practicing with an ordinary dinghy, prior to that. There wil be photos in flight, and I'm told, videos.

Thanks for the photos, Chrostopher!

Dave

[daveculp]

Really? Whose physics? Energy out exceeding energy in? Sound like you have designed the perpetual motion machine. And they said it couldn't be done...

That's my point--pumping is NOT the same as "air rowing." Sure, you can row a boat along with its sail, but pumping is not the same--there's far more energy coming in than going out. No it's not perpetual motion, it's using hysteresis effects to--very temporarily--gain a great deal more lift from the sail. Insects use this all the time or they couldn't fly at all.

And yes, "working" the kite is also similar to pumping, except that almost no power is input by the pilot--but 3-10 times the kite's "static" power is taken out.

Probably too good an idea... Better ban it. :p

Dave

[cristofa]

Did you have a big bow wave with that round bow? or does the kite keep the bow up?
I guessed someone might pose that question, but I don't have pics of the hullform below those near-vertical topsides to show the reasoning behind the shape. The hull was very light and, with the lift from the kite, it was easy to plane. To provide lift and make the boat as sea-kindly as poss (to reduce the fatiguing effects of prolonged slamming), the bow below the topsides is quite deep and rounded. It worked pretty well and that blunt bow, in fact, hardly got wet as the spray shot off the chine.

I look forward to seeing pictures of Dom Mee's boat in action ... what size kites will he be flying?

atb ... Christopher

[CT 249]

"If daveculp comes across a bit heavy at times, it's probably down to a passionate believe in a product that moves sailing evolution forward a notch, and a frustration at the the sailing world's extraordinary resistance to change."

The first sounds fine, but is the sailing world really THAT resistant to change?

I suppose it depends where you come from, and how reasonable you think it is to throw away (from the racing scene at least) perfectly usable boats and gear. About every ten years or less we see an enormous change in boats. What a vast waste (in many ways) of money, enthusiasm and scarce resources just to go a bit faster!

In the last 50 years there have been several enormous changes. The "state of the art" 40 footer in 1955 was timber, long keeled, with a heavy slender hull and stiff rig. By 1965, it was masthead rigged, fin keeled and fibreglass like the Cal 40. By 1975, it was a beamier, higher IOR type like a Peterson. '79, and the state of the art 40 footer was something like a lightish, fractional centreboarder. Centreboards came and went in just two years in the IOR.....not much resistance to change there. Another 10 years and it was a Beneteau type or an early Sportsboat, maybe a water-ballasted Open type. By 1999, the "state of the art" was a canting keeler or Farr 40 OD. Speed is up by 20% or so, which isn't bad considering these boats are inherently limited by waterline length most of the time. How much change do you want??

Same in skiffs and dinghies. State of the art 1950, an Uffa Fox style International 14 - planked, no trap, little buoyancy. State of the art 1960, 505. State of the art 1970, a Farr plywood 18' skiff - much lighter, much more rig, three men all on trapeze. State of the art 1980 - a carbon fibre skiff with racks. State of the art 1990 - skiff with flex-tip mast, assymetric spinnaker. State of the art 2000 - maybe a foiler.

Have you sailed a replica 18' skiff and a modern skiff? Have a go and see how much change there HAS been.

Over the same time the multis have gone from Pivers and Shearwaters to ORMA 60s and carbon A Class. Foilers have gone from Williwaw to Hydroptere. Have you sailed a Piver 25 and then hopped on a modern carbon 25 foot multi? The difference is enormous. How could such an enormous advance come if the sailing scene hated change so much?

Exactly how much change do you want? How much money do you want people to throw away just to go a bit faster?

[water addict]

imagine trying to untangle the kites at a crowded mark rounding!

[CT 249]

Note to all...sorry I got a bit strident, and I'm not attacking kites or development per se. Just not sure that the sailing world is so anti development.

[CT 249]

I think you are right, Fred. A sail which is self-supporting and, as you say, "just waiting for some push" is surely the best way to deal with 0-2 on conventional boats. Chris 249 seems to agree with you as well, if I'm not putting words in his mouth

I'd love to build a "wind finder" kite for these conditions; rigidly inflated with helium, flying 100m or so above the waves, sitting quietly above the slop and surface turbulence.

As Christofa says, a kite such as this is rarely becalmed and will keep the boat moving in wind you cannot feel on the surface. A couple of questions:

Is it the consensus that a kite like this should/should not be "legal" for sailboat racing? Keep in mind that helium lift cannot develop forward drive, so isn't "cheating", at least according to the rules of physics (it's been ruled legal for speedsailing by WSSRC, for instance), but that such a kite will "obsolete" many boats.

How would readers feel about the cost and complexity of such a solution? (cost maybe $100-200/sq meter; complexity involves wrestling helium cylinders into/off the boat (or building them in), also wrestling with a big inflated kite on the foredeck, perhaps in a rising wind. We'd include some "trick" launch/recovery equipment/methods, but the basic facts remain--it's big, it's on the foredeck, and you've got to muzzle it.

This sounds like a potential solution for cross-ocean "open" type racing--and for "painless" cruising with smaller kites. Will cruisers pay this kind of price and will racers put up with the hassles?

Yeah, I'm doing market research here. Your opinion counts. Thanks for all replies,

Dave Culp
KiteShip


The idea sounds cool in some ways. I suppose you could have a massive "panic button" patch that would be torn open for instant deflation when you got a 3 am southerly buster half-way across the Tasman Sea. The worst thing I know to handle on a foredeck is a windsurfer rig (when rigging at anchor while cruising) and this would probably be better which would make it a thorough biatch, but handleable in the end.

But I remain waaaaay too worried about long lines to use one in the harbour on a regular basis. And there's no way I want to have to fart around with gas while sailing. Maybe it should be "legal" for sailboat racing but not for most PHRF and IRC ("normal yacht") racing.

On the other hand, I suppose if you had a kite that developed lift, you could have larger diameter lines going to more points, which may dispel one of my fears about kites on boats. You could also perhaps keep it lower - OK you'd go a bit slower but why is sailing so horrible you have to hurry to the finish? :-)

Most of my cruising is done with kids and it's normally just loafing along.

[Paul B]

That's my point--pumping is NOT the same as "air rowing." Sure, you can row a boat along with its sail, but pumping is not the same--there's far more energy coming in than going out. No it's not perpetual motion, it's using hysteresis effects to--very temporarily--gain a great deal more lift from the sail. Insects use this all the time or they couldn't fly at all.

And yes, "working" the kite is also similar to pumping, except that almost no power is input by the pilot--but 3-10 times the kite's "static" power is taken out.

Probably too good an idea... Better ban it. :p

Dave

Wha?

OK, can you give any examples of "self pumping" rigs that make the main and jib more efficient? With all your AC involvement can you explain why they are making the mistake of ever stiffer rigs to glean the most power out?

With the Tour de France in the news, why don't the bike designers incorporate "pumping" technology into their frame designs? This effect must make a far better climbing bike, yeah?

[daveculp]

Wha?

OK, can you give any examples of "self pumping" rigs that make the main and jib more efficient?
No, I cannot. They do not exist yet.

With all your AC involvement can you explain why they are making the mistake of ever stiffer rigs to glean the most power out?

With the Tour de France in the news, why don't the bike designers incorporate "pumping" technology into their frame designs? This effect must make a far better climbing bike, yeah?
I do not understand your comparison of stiff rigs and stiff bicycle frames to the aerodynamics of hysteresis. I'm guessing you are still confused regarding energy input/output versus transient aerodynamics.

Let's try it this way: Do you understand that, when pumping for instance a J105 mainsail (a boat and sail far too large for a human's relativfely puny input to have much direct effect), that the energy actually harvested and applied to the yacht's hull is greater than that input by the crew? Let's try to establish this first, shall we?

Dave

[Paul B]

I don't feel confused at all.

I'll intently watch the next round of AC action to see if the competitiors there are smart enough to understand this hysteresis effect. That is the top of the research game, and a stone this big surely won't go unturned.

I'm wondering, if you get hit with a puff and your boat heels over (decreasing power) then comes back upright ("increasing" apparent wind) is that better than if the the boat didn't heel and used the available power? If the boat heeled, righted, heeled, righted, ad nauseum would that promote this hysteresis effect?

Have you ever been able to measure the power out of a spring greater than the power in? Nevermind.

Good luck with proving your theory. I hear there's a guy in FLA who is now in the business of making RC models to prove these sorts of theories out, so they can be patented and sold to investors more easily. Maybe you shold contact him.

[daveculp]

It's not "my" theory, Paul, but an established field of aerodynamics. Have you read Marchaj? Or try googling aerrodynamic hysteresis; see if you can learn something new. In the meantime. thanks for your comments. Have a nice day.

Dave

[Paul B]

It's not "my" theory, Paul, but an established field of aerodynamics. Have you read Marchaj? Or try googling aerrodynamic hysteresis; see if you can learn something new. In the meantime. thanks for your comments. Have a nice day.

Dave

I like learning. I tried to google aerrodynamic hysteresis but only seemed to come up with hysterical and hissyfit.

Do you think a self pumping rig would be able to power an AC boat at 7 knots? Would it be eligible for a Guiness Record?

If you design a self pumping rig maybe Langman will put one into his new, larger Zena/Grundig/AAPT.

[daveculp]

I like learning. I tried to google aerrodynamic hysteresis but only seemed to come up with hysterical and hissyfit.

F'ing troll. Climb back under your rock.

Dave

[Doug Lord]

Hah! Dave you hit the nail on the head with that one!!

[usa2]

Hey Dave, would you mind explaining this "self-pumping" rig to me? I find the concept interesting even though it would probably be illegal for racing.

Thanks

[daveculp]

Hey Dave, would you mind explaining this "self-pumping" rig to me? I find the concept interesting even though it would probably be illegal for racing.

Pumping is currently illegal in almost all racing classes, but the definition of the term varies, so it's hard to guess. Sometimes "pumping" is defined as crew-supplied input to the rig and sometimes it is defined as any rythmetic motion of the rig--likely anything which makes the boat faster will be found to be illegal... ;-)

"Self-pumping" is any method of using wind power to "pump" the rig. A conceptually simple one might be a wind vane on a long boom extension, with a mechanism to alter its attack angle and also sense the boom's current position. It isn't hard to imagine designing a series of rods and cranks to have the boom's position set the attack angle on the vane, causing the boom to pump in and out on its own (It's useful to rememberr that pumping does not require large amounts of force--you don't, for instance, need to cause the boom to exceed the wind speed in order to gain power--you do not need to "air row")

Another approach would be to use an "aerorig" type of rig, where the jib is mounted on a forward extension of the boom. Such rigs are almost balanced to begin with; causing them to "autopump" would require much less energy than the first way.

A third would to be to use a fully balanced, rigid wing sail. These have almost zero tension on the sheet, and would require very little imput to get them to pump. You could even (perhaps) design a wing sail with negative stability which will auto-pump itself, with proper linkage. There has been some question (on internet fora) regarding whether the movement of the leading edge to windward during the pump (or the whole jib if an aerorig) might upset the hysteresis aerodynamics. I think not, but others disagree.

What is uncertain, but unlikely, is whether the drag of the vane will exceed the increase in total power to the system; not only are the physics complex and little understood, there's going to be real-world losses in efficiency in any vane system as well. What is likely is that the self-pumped rig will be more powerful than a static rig; the boat will accelerate and you'll be promptly banned. ;-)

For reference, see C.A. "Tony" Marchaj's 'Sail Performance', Part 3, Chapter 5, "Pumping--a Legitimate Technique?" ISBN 0071413103

Or just ask Paul B to take you for a sail on his ACC yacht and show you how...

Dave

[Paul B]

Or just ask Paul B to take you for a sail on his ACC yacht and show you how...

Dave

Wow, that's some weak sauce.


Let's take a J24 in 10 to 12 knots of breeze as an example.

What's the required amplitude and duration of the pumps of the main and jib to create the hysteresis effect upwind?

What is the load on each sail?

What is the power input from the boom-mounted vane? How large does it have to be to provide this amount of power? How well does it work in the gas of the main? What k do you calculate in for mechanical losses?

Do the sails receive input to have the required twist as the open and close?

So many details in the physical world.

[sharpii2]

Now that IS interesting!
For those who are curious, I have found some pictures of my boat ... unfortunately, the only ones of the boat under 'sail' out in the bay were taken by someone else, and I can't get hold of him.

pics 1 and 2 show fitting out ... I used the plywood cover during trials pending the arrival of a Lexan-windowed cabin top. pic 3 shows the boat under way in the harbour ... I was sitting on the floor inside flying the kite through its built-in control system. (it's a pity the guy standing up didn't stand in the middle and ship the boat:). pic 4 is on the quayside after a trip in the bay ... 3 an 4 show the small, 2.5sqm kite which I used to get the hang of the controls.

atb ... Christopher

Interesting boat.

I have been thinking about a kite sail as a jury rig for my 20ft mini cruiser which I someday hope to design and build. Something like Ive seen in Ft. Lauderdale where they use it with what looks like a small surf board. I like the idea that the thing can be rolled up into a real small package and not take up too much space when not needed.

My boat design calls for an unstayed mast, so it is highly likely that if it were ever rolled it would come up minus the mast. The kite, even if its good for only down wind, could get me somewhere.

I then started thinking about making it more controlable. I grew up flying kites so I know all about bridles. I thought why not have two. One fore and aft and one athwartship on the kite. The fore and aft one would be adjustable only with the kite in hand. The athwartship one would have an electric 'bridle creeper' which would be controled from a radio transmiter on the boat.

The bad thing about this idea is that the 'creeper' would need batteries and a way to charge them. All would add weight. The good thing would be that the kite would be attatched to the boat with only one line.

Along with this rig, the boat would have tandem dagger boards to minutely adjust the boat's CLA for course setting purposes. It would have a rudder as well for quick maneuvers. I have also thought about using hydrogen rather than helium for the lifting gas. Hydrogen can be made on sight; helium can't.

Any way. I like your boat and can't help noticing that it would fit nicely within in the rules of my proposed 1x19 class offshore sailboat (see Proposed Class of Small Off Shore Racing Sailboat thread). The main idea of this proposed class is to encourage sail design developement beyond the usual sloop rig (while keeping the costs down) by measuring the entire sail area, not just the foretriangle and mainsail.

The kite could be a great off shore sail development. I wouldn't want to see them racing in crowded coastal or inland waters (especially with power lines about). But I would much rather see them than the Canting Ballast Twin Foils that really look like I'm about to see.

Bob

[CT 249]

I wouldn't know much about hysteris if I sat on one (I think it's in a later ed. of Marchaj than my one) but don't we all know that on windsurfers, Lasers etc in light air you can get a considerable increase in speed from a minor amount of pumping? I know those are not the most precise and quantifiable of terms, but doesn't it indicate the efficiency of hysteris and therefore that a (partly) self-pumping rig would be possible?

Then again, one reason not many people have investigated it thoroughly is that unrestricted pumping is pure shyte. I mean, really, really bloody unrewarding pain in the arse sort of hard work. I mean, not wimpy stuff like grinding a big boat or straight-legging a Laser to cube level, but the hard work where an Olympic class puts out a bulletin warning that deaths may occur if RCs hold too many races in hot weather. The hard work that leads even Olympic medallists to say that the pumping is killing the popularity of the class.

And if you allowed pumping and a top offshore racing crew were becalmed in an offshore race, they WOULD pump and roll a 40 footer until they dropped. It would be more effective to just pump and roll and ignore most of the subteties of light-air trim and tactics. OK, older crews would be left behind, skill would go down to fitness, and we would basically end up with very innefficient rowboats, but they would do it and everyone would hate it and fleets would drop. It would be much more efficient and honest to just put bike-driven propellers out the back.

So how you balance the self pumping rig with that problem, I dunno.

[daveculp]

Too right, Chris. I'm certain that's why it is so broadly outlawed--the line between "efficient" pumping and air rowing is too narrow.

OTOH, if you built a self-pumping rig, the crew need never touch it--which would make the nice clean line--if the wind causes all movement, it's OK; if the crew gets involved; it's illegal.

This is the whole reason I'm looking at self-pumping rigs.

Dave

[water addict]

I'll give an example of an "almost" self pumping rig. If you sail a Laser upwind or close reaching you can do the "pop". In moderate wind so that you aren't quite fully hiked you bounce on the rail with a very small bounce. The trick is to bounce at the rigs' natural vibration frequency which seems to be about 1-2 seconds in a 6-8 knot wind. This will start the flexy mast fanning like a birds' wing and with each bounce the amplitude will increase until after a few bounces you can get the rig going back and forth about 3 feet or more at the tip. And does it ever increase your speed and pointing- you will blow by anyone not doing it- that's why it is against the rules. You literally have a flapping wing with practically no energy input- here again the trick is to pop at the resonance frequency of the rig.

[CT 249]

Hmmmmm, interesting stuff Dave. Intriguing. My gut feeling is that sailing with a rig that self-pumped gently may also not throw tactics out the door as much as unrestricted pumping does, and that would be a good thing too.

When beating and pumping in very light winds in boards we sometimes actually aim to sail in the dead calm lulls, rather than the 1 knot puffs, because it's easier to pump dead "upwind" in a calm than in one knot. There are certainly some possible tactics going on, but the problem is that (say) 95% of the race is fitness and pain and only 5% is the tactics and trim etc. The tactics and trim are still there when pumping, and if we could get rid of the fitness and pain element they would come back into significant play.

I came across a heated thread discussing whether a windmill boat could sail directly upwind and thought it was funny, because when we stand on the foredeck and roll a Laser home in a calm, we do exactly that. Totally irrelevant to the thread apart from the fact that we're talking pumping, 'scuse me.

[rob denney]

Chris,

Fubn thread. Kites, pumping, now windmills.

Is the windmill thread still going? I built a 9.5m dia windmill driving a 1m diameter propellor on a 9m cat a few years ago. Went directly into 20 knots of breeze at 6 knots, despite a bunch of inefficiencies.

regards,

rob

[CT 249]

Interesting beast, Rob. There was a windmill rig on a converted Daimond in NZ years back too, wasn't there?

[daveculp]

You literally have a flapping wing with practically no energy input- here again the trick is to pop at the resonance frequency of the rig.
This is really interesting stuff; thanks. Your point about using resonant frequency vibrations is an excellent one.

Dave

[daveculp]

Is the windmill thread still going? I built a 9.5m dia windmill driving a 1m diameter propellor on a 9m cat a few years ago. Went directly into 20 knots of breeze at 6 knots, despite a bunch of inefficiencies.
At the risk of drawing the trolls back out; it's interesting to note that the scenario of a windmill boat sailing dead to windward, at any speed greater than zero, is precisely analogous to that same boat sailing dead downwind, at some speed in excess of the true wind speed--only the relative fluids are reversed. That this is so tough to demonstrate has to do with Rob's inefficiencies, not the mathematics of it. (has to do with gaining buoyancy and hull drag from within the high-speed versus low speed fluid--works in your favor when windmilling upwind; works against you when water-milling downwind; when you use a water-supported hull for both)

[rob denney]

G'day,

Jim Bates built Te Waka, a Diamond cut in half lengthwise and reassembled with a large triangular piece inserted in the stern. The windmill was similar to mine but smaller (other way round, he was first), but he claimed better performance, 7 knots up, down and across the wind, from memory. He was an engineer, with associated skills, money and equipment, so this is believable.

Neil Bose put a 2 blader on a 19' heavy mono in Scotland. Very nicely done, helicopter blade controls and commercial controllable pitch prop. Worked as well as could be expected.

Jim Wilkinson put one on a 26' Scirrocco cat, cruised across the english channel and back (mostly under motor, as no wind). He has since built a bigger one, taking my biggest in the world record.

Phil Weld was involved in a day sailor version in the USA, built by Havilah Hawkins. Featured in Wooden Boat, I think.

Fun times, sceptics were even more vociferous than they are now about proas and kites!! And just as wrong.

regards,

rob

[cristofa]

A note for those interested ... Dom Mee has set out on his attempt to cross the Atlantic in a (very tiny) kite powered boat, and you can check out his progress at

http://www.dommee.co.uk/pgs/news/kitenews/news-LIVE.html

While I wasn't too happy about his claim to have 'the first ocean-going kite powered boat', I have a fair idea what he's taken on and wish him the best of luck.

Christopher

[cristofa]

Further to the Dom Mee transatlantic kite powered boat saga ...

http://kitequest.typepad.com/mission_updates/2005/09/rescue.html

Christopher