Kites

cristofa

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

thanks

 

nero

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

Christopher

 

Kites+Helium

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?

 

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

 

Mini Transat kiteboat

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

 

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

 

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

 

... that would certainly have been very handy, and would have solved the project's biggest problem.

... that was undoubtedly the case.

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

atb ... Christopher

 

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

 

Francesco

... 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

 

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.

 

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 ******* factor of some of the bozos out of it and it's pretty safe, too.

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

 

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

 

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

 

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.