637 replies to this topic

[Tom Ray]

Back in 1999 I built and flew a solid wing kite as part of the development of my speedsail design. It was small (2.4m x 0.8m) and we flew it several times in 10-12kts of wind. It was brutal. Zero force at take off (I had to run upwind) then with the very low drag it would accelerate across the window so rapidly it was impossible to control (I had a three line setup, but it traversed the window in around 1 second on 40m lines, and I couldn't react fast enough). The force generated at these speeds was so great that I was snatched back down the sand for 20m or so, really viciously.

Not sure I'm understanding this right. In 10-12 knots of wind, that little kite dragged you 20 meters?

Forget anything you know about inflatable traction kites. Powerful as they may be, compared to a solid wing, they are docile and slow, and they don't make power at the high angles of the flight window. That little solid wing could accelerate to 75kts in 12 kts of wind (9 deg AoA), and the momentary force generated was around 2.5kN peak (my calc, not measured). Because the force is generated so high in the flight window, it is not possible to dig your feet in, it just lifts you up and throws you downwind.

I was using a cruciform control bar, which in retrospect was a mistake, because as the wing shoots up it applies more and more angle of attack, which doesn't stall the wing as it was going faster and faster, until I was pulled off the ground and rotated by the control line, but the wing still continued climbing and arcing to windward until the AoA is lost and drag, plus me hitting the ground to leeward, prevent it going any further.

The photo is with the wing flying on very short lines (5m or so) in an attempt to limit speed and hence add some control, but it was like holding on to a bucking bronco and no better controlled, though less dangerous as the forces were lower. In the photo the wing is fluttering back to leeward having already overshot me, and looks like it is about to crash with so much roll. It was very hard to get pictures of it soaring, as the soaring portion happened so fast. Somewhere in the old tapes there may be some video.

I know very little, so it's not too hard to forget all I know about them.

Your comments make me wonder if there's some way to attach a hard kite to a boat instead of a human and still control it somehow.

[couchsurfer]

I know very little, so it's not too hard to forget all I know about them.

Your comments make me wonder if there's some way to attach a hard kite to a boat instead of a human and still control it somehow.

................like this??.................

 SailRocket.jpg   21.52K   3 downloads  SailRocket.jpg   21.52K   3 downloads

[Tom Ray]

Yes, like that, but I have in mind ordinary propulsion, not setting records.

Propulsion for events like the Everglades Challenge. Last year, there were strong headwinds. Competitors who could stowed sailing rigs, masts, etc, to reduce windage while under human power.

A kite seems like something powerful that could be put away quickly and easily, and also light, so it would not be that big of a problem for the beach launch part of the competition. It's also a sailing rig that would be easy to put away to go under the low bridge at Placida.

[yowie]

...And here in the Herals-Sun, so the entire sum of Australian reporting was two items as far as I can see.

http://www.heraldsun...f-1226520836617

[couchsurfer]

Yes, like that, but I have in mind ordinary propulsion, not setting records.

Propulsion for events like the Everglades Challenge. Last year, there were strong headwinds. Competitors who could stowed sailing rigs, masts, etc, to reduce windage while under human power.

A kite seems like something powerful that could be put away quickly and easily, and also light, so it would not be that big of a problem for the beach launch part of the competition. It's also a sailing rig that would be easy to put away to go under the low bridge at Placida.

.......I've always wanted to rig-out a laser hull with a kite system running off a traveller.....

....that could do the trick!

[JohnMB]

I know very little, so it's not too hard to forget all I know about them.

Your comments make me wonder if there's some way to attach a hard kite to a boat instead of a human and still control it somehow.

absolutely
been done several times, works very well
peter lynn has a rig for this http://www.powerkite...kitecat-cat.htm

crossbow did it....

[Tom Ray]

I remember seeing one example in this video:

[hump101]

If you follow it ll the way down the rat hole, you end up with Sailrocket.
The kite s made larger and more efficient an brought closer to home so it can be more accurately controlled and more tightly linked to the payload.
It might be possible to build a less massive Sailrocket, which might lead to some efficiency, but frankly it seems that the waves ( or lack of them) becomes a bigger and bigger problem the smaller you get. So there is some merit in going the other way ( a la Hydrotere) and building a large vessel that can operate in more normal conditions.
Like these guys : http://project.kiteboat.com/
SHC

Not necessarily. This is my thinking:

The basic problem is that if you want to run in smooth water, you have to have high efficiency, which dictates a large wing, and then a large offset between wing and foil, and then a large vessel, with all the high wind handling issues this entails. This is the Sailrocket route, but it is eventually self limiting, simply because the maximum efficiency (2.5?) times the maximum windspeed associated with the limiting wave height equals the maximum speed attainable, if you can actually handle the vessel in this windspeed (35kts?). So something like 85kts peak, so say 80kts average, but the efficiency will drop off further as the speed increases, so my VPP says 75kts average over 500m.
The kite surfers are heading down a different path. They are still Smith vessels, like Sailrocket, but they have a simple system that can be handled in much higher windspeed, and then to get the flat water they use a canal. Their current limit is the ability to find enough wind at suitable locations where a canal can be dug, allied with the grossly inefficient kites currently being used. Nevertheless, if a canal was dug in the way of a tropical storm then even in their current configuration they would be able to beat 75kts, if they don't kill themselves in the process.

However, I am looking at a third option currently, and that is to reduce the requirement for flat water, allowing windspeeds similar to the kites currently use, but by running in deeper water a more efficient foil can be used. Not as efficient as Sailrocket, but it doesn't need to be.
Foil-wise, we've been running wedge section foils with concave trailing edges at 175kts for many years, as rudders in C1 powerboats, so I don't see the foil as being a huge factor, as it will not have to perform at the very tight angles, and hence high loads, required by Sailrockets efficiency. The kite is the issue, as we need to get the efficiency up to around 1.6 from the current 1.1-1.2. 1.6 is achievable with a semi-soft kite, so not as radical as the solid wing I flew years ago, and according to my calcs this efficiency is achievable with similar levels of control as are currently enjoyed by the inflatable power kites.

So that is the proposal, a kitesurfer with a normal board and a semirigid kite, but with an J foil on his back, hinged from the back of his harness and with yaw control from his board. He sails normally on the board, and when up to speed deploys the foil. Once the foil is pulling, he lifts his feet up, and continues to control yaw and pitch by moving his feet, with his weight supported by the tension between the kite and the foil. The only thing at the interface is the foil, so less sensitivity to waves, but he can touch the surface occasionally if he needs to make small corrections. This arrangement should be able to get close to 100kts in 65kts of wind (120kmh - a typical mistral), and since the foil only has to work above 40kts (the board provides the acceleration phase), it can be very small.

[JohnMB]

this also has some good techie stuff on kites
http://peterlynnhims..._For_Yachts.php

for this who have never heard of peter lynn, he's worth reading up on, he was a major force in the development of traction kiting.

[Tom Ray]

The only thing at the interface is the foil, so less sensitivity to waves, but he can touch the surface occasionally if he needs to make small corrections.

But how do you avoid launching into the air if there are waves?

[couchsurfer]

The only thing at the interface is the foil, so less sensitivity to waves, but he can touch the surface occasionally if he needs to make small corrections.

But how do you avoid launching into the air if there are waves?

....................wear a helmet

................if it's not dangerous,,,it ain't fun!!!

[Tunnel Rat]

So that is the proposal, a kitesurfer with a normal board and a semirigid kite, but with an J foil on his back, hinged from the back of his harness and with yaw control from his board. He sails normally on the board, and when up to speed deploys the foil. Once the foil is pulling, he lifts his feet up, and continues to control yaw and pitch by moving his feet, with his weight supported by the tension between the kite and the foil. The only thing at the interface is the foil, so less sensitivity to waves, but he can touch the surface occasionally if he needs to make small corrections. This arrangement should be able to get close to 100kts in 65kts of wind (120kmh - a typical mistral), and since the foil only has to work above 40kts (the board provides the acceleration phase), it can be very small.

Is this still at the theoretical stage or has it actually been trialled, and if it has is there any film anywhere? Please keep us up to date with your progress.

It is great to hear about other paths being explored.

[nroose]

Well, now this stuff has gotten a little too crazy for me to figure out, but I am very entertained on this lonely wet Wednesday night imagining the guy with the foil attached to his back being flung into the air by the hard kite when his foil loses traction!

[auscat]

Well, now this stuff has gotten a little too crazy for me to figure out, but I am very entertained on this lonely wet Wednesday night imagining the guy with the foil attached to his back being flung into the air by the hard kite when his foil loses traction!

Pretty sure Larso went down that path or should that be up
Wonder how a solid wing strapped to your back while sitting on one of those foiling water ski chair things would go?

[IC Nutter]

The only thing at the interface is the foil, so less sensitivity to waves, but he can touch the surface occasionally if he needs to make small corrections.

But how do you avoid launching into the air if there are waves?

A guy called Fritz Roth has been developing an idea for a while which, in principle, solves this problem. He calls it the "Vector Fin". Basically it's a self adjusting hinged hook foil which he uses to provide stability for a proa. ( http://www.proadesign.com )

[Tom Ray]

The only thing at the interface is the foil, so less sensitivity to waves, but he can touch the surface occasionally if he needs to make small corrections.

But how do you avoid launching into the air if there are waves?

A guy called Fritz Roth has been developing an idea for a while which, in principle, solves this problem. He calls it the "Vector Fin". Basically it's a self adjusting hinged hook foil which he uses to provide stability for a proa. ( http://www.proadesign.com )

That's a very interesting page and it addresses some problems that have been on my mind, but I think hump101 has a different set of problems. Basically, I can't see that thing adjusting to each wave quickly enough at really high speeds. As mentioned, things go horribly wrong if it lets go. With apologies to Paul...

[hump101]

The only thing at the interface is the foil, so less sensitivity to waves, but he can touch the surface occasionally if he needs to make small corrections.

But how do you avoid launching into the air if there are waves?

A guy called Fritz Roth has been developing an idea for a while which, in principle, solves this problem. He calls it the "Vector Fin". Basically it's a self adjusting hinged hook foil which he uses to provide stability for a proa. ( http://www.proadesign.com )

This is not a new idea, it has been tried for 30 (40?) years, but as the Sailrocket designers have just demonstrated, it is not the original ideas, but the research and development that leads to a succesful outcome.

Regarding waves, the vessel would not be operating in developed seaways, just chop from near shore fetch. With winds above 50kts, the chop tends to get flattened by the wind as long as the fetch doesn't exceed 400m or so. As long as the foil can cope with 0.5m change in surface elevation it should be able to cope with the conditions specified.

[hump101]

The only thing at the interface is the foil, so less sensitivity to waves, but he can touch the surface occasionally if he needs to make small corrections.

But how do you avoid launching into the air if there are waves?

A guy called Fritz Roth has been developing an idea for a while which, in principle, solves this problem. He calls it the "Vector Fin". Basically it's a self adjusting hinged hook foil which he uses to provide stability for a proa. ( http://www.proadesign.com )

That's a very interesting page and it addresses some problems that have been on my mind, but I think hump101 has a different set of problems. Basically, I can't see that thing adjusting to each wave quickly enough at really high speeds. As mentioned, things go horribly wrong if it lets go. With apologies to Paul...

The foil runs below the waves, the strut is the only thing extending through the range of surface elevation, and the strut has a neutral AoA at all times, so will not entrain air. The problem with VSR1 above is lift from the crossbeam/rig being ahead of the CoG, not something that is problematic with kite strings.

[Hike, Bitches!]

I didn't bother to read this whole thread, but congrats to the Sailrocket guys..I did watch their youtube videos...Smokin'!

[Willy Clark]

You kidding me Larso!?

http://clarksail.com...en-you-serious/

Somebody stop him!

Best,
Willy

[Tom Ray]

You kidding me Larso!?

http://clarksail.com...en-you-serious/

Somebody stop him!

Best,
Willy

No! Nobody stop him! He's one of the greatest shows on earth!

After shocking the world by saying that the boat probably has 70 knot potential in a recent interview with ClarkSail, Paul has now changed tacks. Having conquered speed it is now on to survival and next on the agenda a re-enactment Sir Ernest Shackleton’s voyage of the James Caird early in the new year.

That's not a shocking claim after watching Sailrocket perform. It darn near went 70 knots and looks like it can without too many more tweaks and attempts.

Re-enacting the voyage of the James Caird sounds pretty dangerous, depending on how accurate they are trying to be, but I'm looking forward to hearing about it. I think this adventure needs a new thread.

[auscat]

You kidding me Larso!?

http://clarksail.com...en-you-serious/

Somebody stop him!

Best,
Willy

Wow that took a while see post #4.
When I first met Larso he was travelling around Australia in a kombi towing an ultra light,you just never know whats next.Bound to make you shake your head and grin though.Crazy bastard.

[Tom Ray]

you just never know whats next.Bound to make you shake your head and grin though.Crazy bastard.

This should probably be Paul's epitaph, which I hope will not be needed any time soon.

[MR.CLEAN]

The Caird trip has been in planning for a long time now. We've been speaking with the guys behind it, I'll ping them for an update.

[Presuming Ed]

Is it this one? http://shackletonepic2013.com/

IIRC, the voyage has been re-created in replica boats a couple (??) of times.



ETA Arved Fuchs did it in 2000.

http://www.arved-fuc.../sh2000engl.htm



I vaguely remember there being one other voyage.

FETA: Looks like Skip Novak accompanied an earlier voyage in 1997, the South Aris Project
http://www.pelagic.c...rvices_over.asp



Any more?

[shaggybaxter]

You're not thinking of this one are you?

http://www.petegoss.com/mystery/

Funny they now each other, mad bastards this lot.
Where would we be without them?

SB

[Tom Ray]

Sailrocket write up in Wired:

http://www.wired.com...sailrocket/all/

[Guitar]

Gotta love this..."We’ve had the test-pilot phase,” he says. And sailing has had its sonic boom."

Great read.

Thanks Tom.

[MisterMoon]

I remember the on Skip Novak accompanied. The weather started to get the best of the guys on the Caird replica and the elected to get off and aboard Skip's boat between storms. Before they left their replica, they drilled 1/2" holes below the waterline to sink her. Kind of sad, really.

[auscat]

Sailrocket write up in Wired:

http://www.wired.com...sailrocket/all/

Great find.Thats the best description of Larso yet.

[couchsurfer]

Sailrocket write up in Wired:

http://www.wired.com...sailrocket/all/

Great find.Thats the best description of Larso yet.

....posted on the FP today,,,,,too bad the ed didn't check here first........

................-SCOOPED-,,,by TomRay!!!

[HASYB]

Extensive history of Sailrocket on MainSail CNN: 3 parts !

http://edition.cnn.c...ul-larsen-a.cnn

[nroose]

Extensive history of Sailrocket on MainSail CNN: 3 parts !

http://edition.cnn.c...ul-larsen-a.cnn

Great stuff... But a bit late, no?

[Tom Ray]

Complete video from the RC airplane that was filming Sailrocket on the record run. You might want to go to youtube to see Paul's comments about this. He says the plane can only go 110 km/hr and could not keep up with the boat. The hobby shop owner who did the flying says Paul won't beat his next plane.

[dogwatch]

^

I find what those responsible for Sailrocket have done much more appealing than AC33/34. That's an emotional reaction. I think it's based on a belief that they are driven by huge enthusiasm rather than the commercial coldness of today's AC and also the purity of the objective - to produce the fastest boat on a speed record course. That's quite different to producing the fastest boat around a course while subject to a rule. While it could be argued that the AC33 boats had close to similar purity of objective, I had a distaste for both leading protagonists which was a barrier to emotional connection for me.

[yowie]

Great pics, thanks for the link. The RC landing looks like sticking it on a carrier deck, guess that's down to wind-strength.

[Tom Ray]

Hmmm... from the Concept Boat thread...
 
 

This from the Dolphin Research Center in Grassy Key, FL
Seems tha the hull skin could benefit from the same sort of construction.

Timo:
That, micro ridges or micro grooves, was tried many years ago on 12 meters. As I recall it was succesful but subsequently banned.

Being banned by racers is a ringing endorsement of an idea.

[Presuming Ed]

Maintenance and fouling are significant issues, AIUI.