Newbee with a brilliant idea needs your help!

That's a cool idea. I read that at speeds under 3knots wave drag does not play a role though (and you can leave it out of drag calculations).

Also, let's say we make the form of the bladder more elongated than the one in the pic above; more a "snake" form, this should reduce drag too, shouldn't it?

 

About power generation, yes if the wind is going the way you want to go (which by statistics alone will be a small fraction of time at sea), great, if not then all that gear you have to lug around does nothing except slow you down and take up cargo/fuel space.
Deploying and retrieving a big kite on a commercial vessel, with safety gear, pipes, misc antennae and crap all over the deck on a rolling pitching platform- I wouldn't want to do it, risk having a flopping hawser wrap around my arm or leg and tear my body to shreds. Doesn't mean it can't be done of course.

About funding and Skysail- you hit the magic topic here, money. It's most likely not about producing a cost beneficial product, but filling some politically correct company pork barrel. Who in turn then gives a chunk back to a campaign fund (sorry to let my cynic out).

As far as how much real weight you save using marine composite hull structure versus steel, it is not as much as you think. Typical hull structure alone saving is in the 30%-40% range for glass/vinylester for craft about 200 ft and smaller. As far as overall displacement savings for composite, its more like maybe 15% if lucky. Go over 300 ft, and the saving disappears, because low stiffness governs. The total displacement saving including the tug and water bladder total will be almost negligible- water is heavy. And you have more capital investment making an expensive composite ship.

Also, it is important to keep in mind the route in which the water is to be shipped. Different trade conditions/routes can mean markedly different ship dimensions/speeds which will make it either profitable or bankrupt. Remember economics is the dictating factor, and the start of all this is an economic study to determine if an investors dollar is better here, or in microsoft stock.

 

Then get rid of the kite and use an underwater sail and you've got a smugglers dream. Sam

http://patimg1.uspto.gov/.piw?Docid...ageNum=&Rtype=&SectionNum=&idkey=78766A91D329

 

I swore I would stay out of this, but of course I find I cannot... Hi, I'm Dave Culp, President of KiteShip (www.kiteship.com)

First, I'd suggest that this problem needs to be split into several; I see some arguing for and against water bags replacing hulls; for and against sail power replacing conventional engines; for and against kites replacing conventional sails, even for and against transporting fresh water versus desalination... All of these are good arguments, but cross-arguing isn't moving the agenda forwards.

Kitetug (BTW, "KiteTug™" is a trademark of and copyright to KiteShip Corporation. Thanks for the free advertising!) Kitetug, you seem to be making the presumption that towing water in soft bags via diesel tugs is already a cost-effective technology, and are proposing substituting kites for diesel powered tugs. Is this succinctly accurate?

If so, why do you presume you need a separate hull for the kite to pull? Why not connect the kite directly to the big bag? There's no chance of lifting it--even a very powerful, huge kite might pull on the order of 50 tons, and even a small water bag will weigh hundreds if not thousands of times this. It is not even feasible for such a large kite to lift a "small" tug out of the water--ocean-going tugs are several hundred feet long, weigh tens of thousands of tons... and even the smallest tugboats weigh far in excess of their bollard pull rates--or what any kite might provide.

However, not to put the cart in front of the horse; there appear to be a number of holes in your underlying presumption, some of which have been pointed out; Drag on a waterborne conveyence is what is important, not its weight. If a volume of water (or any other commodity) can be enclosed in a lower-drag steel hull than in a floppy bag, it will take less energy to move it from point A to point B than the bag. I would submit that this is so, or you'd see many more bags being towed about than you do (bag technology isn't new) Further, the website you point to presumes "solving" the drag problem principally via slowing the tow to the point (3 knots is mentioned) that it becomes financially impractical--a 16 kt freighter could make 5 trips to the bag's one, and need carry only 1/5 the capacity to equal the bag's delivered performance. More to the point, it can have equal size and deliver 5 times the water in the same time period. Sure, using 5 times the fuel (or even more), but fuel isn't the only cost of running a ship, and most of the others are time sensitive--amortization, for example, runs on a fixed rate regardless of how fast the ship moves.

We don't see underwater cargo submarines for good reason--a submarine hull has reduced wave-making drag--so is good for a warfighting machine expected to travel at 50 kts--but has far more friction drag than a well-designed surface hull, so is much more inefficient at "normal" speeds. (a cargo ship's total drag is dominated by surface friction, not wave drag). You also don't speak of side-force production; without some manner of creating sideforce, your kite-powered bag can only be towed 20-30 degrees either side of dead downwind. What about reaching, or upwind courses?

You don't speak to longevity; if I build a cargo "bag" for $1 versus a steel barge for $5, which lasts for 5 as long, they are equivalent in cost, over their productive lives. Also, unpowered barges make up a tiny fraction of all ocean-borne water traffic; self-powered hulls being more desired--by far. Ask--and answer--the why of this before proceeding. (Just one small example, sailing ships--including kites--largely cannot sail under bridges, will have problems maneuvering near other vessels or in flukey winds near cities, etc.)

Last, you don't look at the economics of carrying water as a cargo--this isn't a common cargo. I'd ask myself "why?" before trying to solve it. Why not carry crude oil in this manner? Or corn syrup? Both are more valuable cargos than water, and both command higher transport rates.

Now, speaking to kites (which is, after all, what I do ;-)

IF one presumes there is a market niche for wind powered waterborne transportation--and I assure you there is--then a good case can be made for kites versus masted sails, for a number of reasons. For example:

This is really interesting, Water Addict. We have graduate students replicating this work ourselves today. What if you updated your work, presuming today's cost of $350-550/ton for fuel versus "years ago" pricing (I bet you used something on the order of $50-80/ton)? Would your results be the same? What about after allowing for the new SECA regulations, which require using a secondary fuel system on many near-land routes (including all the costs of redundant tankage, filters, pumps, etc), with its $60-100/ton additional increase in cost for low-sulphur fuel? Still no advantage?

What if we consider kites, instead of masted sails? Kites cost 20-30% of what a masted sail setup costs (which savings propagates throughout the amortization process), and neither infringes on interior space (strength bulkheads) nor on exterior deck space (kites go into a box on deck; masts block not only bridges, but also cargo unloading booms and cranes). Kites do not heel the boat, so no ballast needed = more cargo than a conventional sailing ship. Would these various and cumulative savings have altered your conclusions? How about the fact that the kite can be manufactured, repaired and rebuilt off-site, and delivered ready to deploy in a standard container; thus requiring no downtime for the ship, as opposed to masted sails? Is the fact that kites can be efficiently and cheaply retrofitted to already partially-depreciated ships a consideration?

It is unlikely that sails--or kites--will replace diesel engines any time in the near--or even far--future, but as an assistive technology--use kites to reduce engine revolutions and fuel consumption, whenever you can--not only can, but already do offer significant short- and long-term savings for shipboard use.

And to the naysayers who've posted additional objections; you are absolutely correct; there exists today no off-shelf complete kite-powered solution for sailing (Skysail's biggest kite to date is smaller than 250 sq ft. Even KiteShip, with its world-record 4,500 sq ft commercially-available traction kites, aren't yet large enough for ship-pulling use. However, both companies *will* be building ship pullers in the near future). There remain engineering challenges, but these are *engineering* challenges; no breakthrough technology needs discovering or inventing. Each of the objections you make are well-known within the industry and have been--and are being--addressed as we speak (Well, OK; today we are closed for the Christmas holiday!). Companies like KiteShip are finding significant investment--and potential applications--even today, which is why companies all over the world are looking at this technology.

Cheers,

Dave Culp
http://www.kiteship.com

 

Thanks Dave for a very clearifying post

 

First off, what an impressive company. It seems like you are steaming ahead with this exciting technology. I'm not an engineer, but I have a healthy dose of common sense, and I think KiteShip's like SkySails' technologies definitely await a bright future, given Peak Oil, global warming and so many other issues.

Thanks for your very succinct and clear explanation of the main points.

I didn't know "KiteTug" was a trademark of your company, and if you don't object I'll keep using it on this forum.

Absolutely. There are several companies out there towing water-bags to places where there's water-scarcity (one of them regularly tows water from Turkey to Greek tourist islands in the summer). Others are planning to do so (amongst them a company which will tug Congo-water to dry Namibia).

They do it with ordinary diesel-tugs. I don't see why a kite system couldn't be attached to such a tug, in order to save money.

Well, the bags are made of fibre-reinforced polymers, so they're not that strong, I think. I don't have any real data on the strength of the polymers involved.

But you provided the answer I was looking for: a kite attached to a small tug will work. The kite won't lift the tug out of the water. That's all I really needed to know!

True, but I have read about new bags which contain water at pressures, to make the bag almost rigid. "Medusa bags" are much more "hydrodynamic" (I don't know if this word exists), not floppy, and they are very rigid when they're filled with water under pressure.

The main reason why we don't see bags any longer is because environmental laws do not allow it, I think. In the 1960s and during petroleum crises in the past (Suez), dracones were used to tow petroleum. The system worked very well and, volumetrically speaking, these dracones used about just as fuel much as a steel tanker.

Of course today it would be unthinkable to use this technology for petroleum, given stringent environmental laws and double-hull requirements for oil-tankers.

For water, they are being used.

Yup, but if the numbers are: bag for $0.5 and steel barge for $10, which lasts only 3 times as long, then we have a deal.

For bulk water transport, this deal is on. (Worldwater S.A., a company working on this has calculated it in quite some detail.)

http://www.worldwatersa.com/

Yup, but according to some, water is going to be the blue gold of this century - a very valuable commodity which will make the economics of bulk water trade and transport work out, provided desalination remains as costly and as environmentally unfriendly as it is today (which is likely).

http://www.polarisinstitute.org/pubs/pubs_blue_gold_ch6.html

I think environmental laws do not allow the use of this kind of polymer tankers for anything else than water. If you spill it, you have sweet water ending up in sea-water - not a disaster. If you spill petroleum, you're done. That's why both the US and the EU now have double-hull requirements for oil tankers.

I for one don't need any convincing at all here. Not after I've read Skysails and (now) KiteShip's info. I also happen to be up to date on Peak Oil - and quite honestly, I know enough...

I'm not surprised you're finding investments. I wasn't surprised either to see SkySails finding enough financial means from institutional (as in "EU") investors. The technology makes big sense, and we'll see it being used pretty soon, I think.

And if bulk water transport becomes routine too, this might be one of the first niches to adopt kites for assist, since the margins for water won't be that high to start with, while bunkerfuel prices will continue to increase dramatically.

Some suggested using the old fleet of single-hulled oiltankers (which have to be decommissioned) for bulk water transport. But the problem is that you won't have anything to carry on the return or forward trip - and this makes the economics of using those converted oil-tankers unattractive; the big polymer bags however can be folded up [see pic], stored onboard the tug, and the tug can "race" back to the water-source for its next trip.


This is why the bag beats the idea of using single-hulled tankers.


In short, my idea remains brilliant!

 

Glad you could not stay out....Nice and interesting post.

About this possibility :

I have a question:It seems to me that a kite demands expertise in its control, I mean we are not talking about sport, but about everyday use by normal sailors that normally have far less demanding tasks.

The only experience that I have with kites is flying the one that belongs to my brother, that is the kind of kite that pulls surf boards. It's amusing but requires training and skills, and a mistake can crash the thing.

How do you propose to control safely a huge kite developing enormous forces?

A servo mechanism and a computer? Can they be up to the task?

 

Dave,

Interesting post. Thanks. I, too, am an expert on kite propulsion. On a kayak trip a few years back I tried to use a parafoil kite as a power assist. It was more difficut than I had imagined.

1st - as you mention, it seems that the wind is NEVER going your direction.

2nd - it was difficult to launch. Required someone downwind in another kayak to toss it up into the air. But often the kite ended up in the drink, then it was wet, and harder yet to launch. I think it was successful one time, but that time was pretty effective... How would you launch such a large kite from a ship? Balloons? Cannons?

3rd - once moving, the apparent wind dropped and the kite wanted to stall. If I had been out in 30 kts that might not have been a problem, but in a kayak in cold Alaskan water... not me.

 

Thaks, all, for the kudos. I'm sorry, but I'm not able to "preview" proprietary technology-which competitors already are watching rather closely--on a public website. I can say that all of the concepts mentioned here by others--balloons and cannons for launch, and servos/computer controls for big kites--have all been tried and tested, some as long ago as the 1980's. Some worked very well, some failed for lack of computing power, materials science or incomplete knowledge of kite aerodynamics. So, the simple answer is; all of the above--and more, of course. ;-)

I might mention that only KiteShip--and no one else on the planet; prototype or even experimentally--have managed to self-launch and self-recover--completely dry--kites above about 200 sq ft. We're routinely doing this with kites to 4,500 sq ft at present--not in prototype testing, but in commercially available products. (here's a link to our latest "big kite" delivery; a 3,250 sq ft OutLeader on a big 65' sailing catamaran the first week of December: http://www.kit-cats.com/kite/300 meter kite sail.htm )

Cheers,

Dave Culp

 

Interesting... something to keep in mind for my next boat project. I guess the big advantages over a spinnaker are that you don't need standing rigging, and since you can tie it off on bow cleats you don't have the big fear of pitch-poling. A possible accessory for a long-distance powerboat doing a downwind run.

If I had to figure a way to launch a really big kite from a ship, I'd consider using a smaller kite, or series of smaller kites, to raise the bigger one. Launch a small kite that could be manually handled, then use that to "lift" the next, larger kite, and so forth until the megakite was launched. Bias the smaller kites for vertical lift rather than horizontal pull. Maybe use a pair of small kites to help stabilize the big kite - keep the corners pointing up. Just might work...

 

At the moment it would appear that we're all missing the main point - this is about carrying cargo and of course making money. Which is why sailing vessels with all their magic rigs became unusable; too bloody inconsistant. However a time will come when ALL fossil fuel will be exhausted and then, AND only then will mankind have to look to other ways to keep living!

It is then that this style of technoligy (?) will be needed. So to all the doubters; at this stage it's all research and learning but it WILL be needed, the sooner we learn the better! To the rest of you; this may not be the way to go but it's got to be tried for the sake of mankind in general - keep it up! Wether you are the smalltime dreamer or the 'bigman' looking to make money from it all (I believe your misguided in this aspect alone but...) keep on trying. Eventually mankind will need your designs for real (not just playing with one or two vessels as you are now!!! sorry if your offended but that's the way it is)!

 

Walrus - I like how you call it how you see it, but you're too much of a pessimist.

Take a look at this: http://www.oilendgame.com/ Read the exec summary for starters.

 

Thanks for your thoughts, Walrus, and no, I'm not offended, but I find it's useful to remember that this isn't an "all or none" game. Sure, It'd be cool if people stopped consuming so much petroleum in the interests of our children and our planet, but you're absolutely right--it's about money.

Then again, we don't need to run out of oil in order to get shippers to look elsewhere for energy sources; we only need to make the alternatives less expensive ( = more profitable). With current oil prices, more than 60% of a ship's operating costs are for fuel (up from 20-30%, historically). For the first time, it looks like these high prices aren't going to go back down. There is a HUGE "economic opportunity" in this disparity. As I've said before, sail won't replace petroleum, but it CAN--today--reduce the total cost of shipping when used as an assistive technology. If it increased net profit margins, who *wouldn't* use it?

That's my job; make it profitable to use sail--and modern kites are the tool I chose to use. I wrote and co-wrote two seminal papers on the subject, almost 10 years ago: http://www.dcss.org/speedsl/KiteTugs.html and http://www.dcss.org/speedsl/Trans_Sailcraft.html

In these, we came to the conclusion that the world could "make a go" of kite sailing for commercial vessels when ships' fuel reached $1/gallon. The papers are somewhat out of date today, but cost and profit variations have run both ways; unsurprisingly, costs have increased faster than we foresaw and solutions have become less expensive, again faster than we foresaw. Marine diesel, today, is just under $2/gallon...

 

Deering, Kiteship - thanks for your comments! I agree you are both right and the "technoligy" (never could spell that word, tells you something, but what?) is slowly becoming fact. and a good thing too, however please remember how the oil companies got their monoploy. By pretending to care, and help, then they fund the development and promptly destroy the idea one way or another - keeps them rich and powerful (it's that money thing again!) . OK they are changing, but only because they have to! They need watching at all times, theres some bad hats out there!

Incidentally Deering my philosopy is that of a 'pessimistic optomist' - I believe that everything will be OK in the end, but I look at everything from the worst viewpoint! that way when it goes right (and it normally does - eventually) I get a big bonus! bet there's more ups in my life than yours! Think about it!

 

Brilliant!

Wind power is old and true to its nature. Using wind to transport water is best done by filling a hull and hoisting a sail. Capturing the jet stream woud be cool but oh so problamatic.

This thread was interesting but mostly useless disfunctional garbage.