[LaurieAG]

Originally Posted by Turtle

I think the article gives a misimpression by juxtaposing '30 foot parafoil' with '3 pound camera', as my 6 foot box kite flown square gave easily a pull on the line of 25 pounds or more.

Granted I needed a fresh wind (steady 10 to 15 mph at least), but in the new rhomboid configuration I have the kite in now, I expect it to fly in lighter winds. With a weather proof enclosure I expect my camera to weigh ~ 4 pounds.

That's what I thought Turtle, the weight of the camera is negligible to the pulling strength of the kite (unless the winds are low).

Call me pedantic if you like, but have you given any consideration to an auto feed out/in line tensioning reel? i.e. while the winds strength generates a certain pulling force the line is reeled out but when the pulling force drops the line is reeled in until the required pulling force is reached or the kite is fully wound in. These are just thoughts based on my earlier ideas for a semi autonomous kite based power generation platform.

[Turtle]

Originally Posted by LaurieAG

That's what I thought Turtle, the weight of the camera is negligible to the pulling strength of the kite (unless the winds are low).

Call me pedantic if you like, but have you given any consideration to an auto feed out/in line tensioning reel? i.e. while the winds strength generates a certain pulling force the line is reeled out but when the pulling force drops the line is reeled in until the required pulling force is reached or the kite is fully wound in. These are just thoughts based on my earlier ideas for a semi autonomous kite based power generation platform.

I love pedantic! First, I think an effective method for power generation with a tugging kite is to use the piston/spring setup as is emplyed in ocean-wave generating schemes.

The reel business made me think of William Cody, as he had elaborate reels for his man-lifting kites. Anyway, I stumbled on this source covering Cody and much more in kite history. Go to page #14 to see a picture of Cody with a boat he took across the English channel powered by a kite. >> http://www.drachen.org/journals/a04/journal4.pdf

[Turtle]

Originally Posted by LaurieAG

...
Call me pedantic if you like, but have you given any consideration to an auto feed out/in line tensioning reel? i.e. while the winds strength generates a certain pulling force the line is reeled out but when the pulling force drops the line is reeled in until the required pulling force is reached or the kite is fully wound in. These are just thoughts based on my earlier ideas for a semi autonomous kite based power generation platform.

I have given some more thought to this 'platform' and come to a possible mechanical solution sans a piston. On the boldened, I think the idea of the kite reeling itself completely in under its own power is tanatamount to a clock winding itself, that is to say, a perpetual motion machine and so impossible.

So, using my rhomboid kite as an example, I use a 2 point bridle connection, but with two lines. The upper line is the stronger and attached to a ring a fixed distance from the kite, and the lower lighter line passes through the ring from its connection to the kite and on to the ground. Shorten the lower line and the kite takes a steeper angle of attack and develops more lift; lengthen the lower line and the kite flattens its angle of attack, spilling air and loosing lift.

On the ground, the main line is attached to a rack, as in rack & pinion gear, and the rack drives a gear attached to the generator (with appropriate transmission gears). Also attached to the rack, and acting opposite the kite-line, is a spring sufficient in strength & throw to fully pull the rack back while driving the generator.

To make this work, the kite is set to an initial high-angle of attack with the lower line attached to a pivoting arm which is attached to the rack. In this position, the kite pulls the rack outward, driving the generator and tensioning the spring. At full extension, a trigger lets fall the pivot arm which lengthens the lower bridle line spilling air and the kite falls and the lines go slack. During this drop, the spring recoils the rack driving the generator, while resetting the pivot arm. When the kite stops dropping it is again in the high angle of attack setting and climbs starting the process over.

That's all I got.

[freeztar]

The Beluga skysail has made its maiden voyage and docked into Norway recently.

“We can once again actually ‘sail’ with cargo ships, thus opening a new chapter in the history of commercial shipping”

Thus is the verdict from MV Beluga Skysails captain Lutz Heldt upon completion of the vessel’s 12,000 mile round-trip maiden voyage. The crew and vessel were at sea for nearly two months, giving the “skysail” concept ample opportunity for testing and tweaking.

The journey took the ship from Germany to Venezuela, the United States, and then to Norway, arriving on March 13...

Deployment of the 160–square-meter towing kite offset up to 20% of the engine’s power (and carbon emissions), saving an initial $1000 per day in fuel costs.

Kite-Driven Beluga Skysail Completes 12,000 Mile Journey and Proves Concept ( shipping, skysail, sail+shipping,)

[LaurieAG]

Originally Posted by Turtle

I have given some more thought to this 'platform' and come to a possible mechanical solution sans a piston. On the boldened, I think the idea of the kite reeling itself completely in under its own power is tanatamount to a clock winding itself, that is to say, a perpetual motion machine and so impossible.

Good point Turtle,

But remember that the wind isn't a consistent factor and also consider that the power generated (and stored in a battery pack) could be used to reel the kite in. As long as the power expended in keeping the kite in the air as well as reeling it in (could be difficult in really strong winds) is less than the total power generated and stored you should have an excess.

While most of my kiting experience is with delta wings, do your box kites have any problem with 'dead stalls'?

[Turtle]

Originally Posted by LaurieAG

Good point Turtle,

But remember that the wind isn't a consistent factor and also consider that the power generated (and stored in a battery pack) could be used to reel the kite in. As long as the power expended in keeping the kite in the air as well as reeling it in (could be difficult in really strong winds) is less than the total power generated and stored you should have an excess.

While most of my kiting experience is with delta wings, do your box kites have any problem with 'dead stalls'?

I thought more about it too and agree on the reeling in and having an excess of stored energy; my comparison was in error.

The box does stall sometimes, as most kites can & will in changing wind conditions. My earlier versions of large box kites used lighter sticks, which twisted causing the kite to turn & then stall & fall. The sticks would straighten, the kite right itself, climb, and then twist, turn, stall & fall again.

My current kite is heavy, but it does not twist. Looking forward to seeing how it flies as a rhomboid as I have never tried it before. This good 'ol kite is ~25 years old.

[LaurieAG]

Originally Posted by Turtle

The box does stall sometimes, as most kites can & will in changing wind conditions. My earlier versions of large box kites used lighter sticks, which twisted causing the kite to turn & then stall & fall. The sticks would straighten, the kite right itself, climb, and then twist, turn, stall & fall again.

Hi Turtle,

How would a propeller with a light weight fan cowl or nacelle (for safety) go in the center of the box kite? It would probably strengthen things up a bit (everything would have to be lightweight but provide a solid central mount) and, due to its angle to the wind, would sit along one of the axis poles (raked).

Originally Posted by Turtle

My current kite is heavy, but it does not twist. Looking forward to seeing how it flies as a rhomboid as I have never tried it before. This good 'ol kite is ~25 years old.

I've been playing with small electric R/C helicopters (I was actually thinking of building a model on this scale using the rotors and main motor to see if a charge will be generated on a multimeter) and note how the twist does destabilise things a bit. Possibly this twist could be used to counter out the twisting of a lightweight box structure?

The rhomboid shape would be interesting as a neutral rotor (unrestricted) would actually provide some extra lift in low winds if set up correctly. If the fan cowl was fixed in place into the box structure (as opposed to free rotation of the cowl) you could expect this type of assistance and also expect to generate power in winds that are too light to actually lift the kite. off the ground (the main reason for the kite is to get the generator up into higher wind speeds)

Also there's an added benefit of using a cowled rotor on a box kite, how many birds have been knocked out of the sky by box kites?

p.s. I noticed your new 'avatar' title, it's a good show.

[Turtle]

Originally Posted by LaurieAG

Hi Turtle,

How would a propeller with a light weight fan cowl or nacelle (for safety) go in the center of the box kite? It would probably strengthen things up a bit (everything would have to be lightweight but provide a solid central mount) and, due to its angle to the wind, would sit along one of the axis poles (raked).

It is possible to add equipment to the interior of the box kite structure, however this changes the center of gravity, as well as interupting the air that normally passes through the open front and impinges on the inside of the back panels where it develops additional lift. The box kite is very strong in the 'standard' configuration and other structure simply adds weight. Properly constructed, the cross bracing is in compression and holds the panels in tight tension.

As with my camera work, I think any equipment is best suspended on the flying line far enough below the kite to not dirty its air. A turbine generator mounted to head into the wind like a regular wind vane seems doable.

Originally Posted by LaurieAG

...Also there's an added benefit of using a cowled rotor on a box kite, how many birds have been knocked out of the sky by box kites?

Uhhhmmmm....no birds? I can't recall ever seeing any bird knocked out of the sky by any kite.

[LaurieAG]

Originally Posted by Turtle

As with my camera work, I think any equipment is best suspended on the flying line far enough below the kite to not dirty its air. A turbine generator mounted to head into the wind like a regular wind vane seems doable.

Hi Turtle,

I've actually been thinking a bit about it (especially ease of construction/repair/strength etc) and I might play around with something like styrofoam and 1/8 ply composite. I could use a central block of foam to house the generator/fan while 4 extension arms could be used to create a decent gap between the ends. As long as there is a large enough gap between the center block there shouldn't be a problem with air flow restrictions and a COG change might actually be desireable.

Also, a rhomboid box shape might be very interesting with these types of materials although other possibile shapes abound .

[LaurieAG]

Originally Posted by Turtle

Uhhhmmmm....no birds? I can't recall ever seeing any bird knocked out of the sky by any kite.

I forgot that the strings can cause serious rope burns but luckily all of the seagulls seem to stay well clear.