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Re: Vine seeds become 'giant gliders'

Postby ARP » Thu Feb 18, 2016 11:06 am

Kai,

All very interesting stuff. Dynamic soaring utilises wind shear to power flight so I wonder if what the spider does is more akin to "dynamic kiting" whereby it projects its silk up through the lower levels of slow moving air to the high speed flow. With the L/D @ 0/1 it gets lifted up and along like the downed pilot recovery system as shown here:-

https://en.wikipedia.org/wiki/Fulton_su ... ery_system

This system uses a balloon to get the line up to the level for the aircraft which would be the equivalent of the high speed air flow that the spider uses in its system. So nature got there first with this one.

Tony
Last edited by ARP on Thu Feb 18, 2016 11:28 am, edited 1 time in total.
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Re: Vine seeds become 'giant gliders'

Postby ARP » Thu Feb 18, 2016 11:22 am

Kai,

Further investigation on ballooning/kiting spiders shows that they may actually produce more than a single silk thread and so could be operating at higher Reynolds number after all.

". These spiders use tens to hundreds of silk strands, which form a triangular sheet with a length and width of about 1 metre (39 in)[5]"

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Re: Vine seeds become 'giant gliders'

Postby Frank Colver » Thu Feb 18, 2016 11:27 am

It's amazing how far those "flying" spiders can go.

One time, years ago, in SoCal when a hot, dry, "Santa Ana" wind was blowing toward the coast the areas near the beach were inundated with these tiny spiders. People wondered where they came from. Their origin was determined to be on the other side of the Santa Ana Mountains in the Corona and Riverside area, a distance of 25 to 50 miles. On the NE wind they had sailed through Santa Ana Canyon (pass through the mountains) and out to the coast where the wind speed slowed down and deposited them with their trialing spider web "strings" on cars and everything else.

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Re: Vine seeds become 'giant gliders'

Postby msoaring » Fri Feb 19, 2016 8:26 am

I remember one particularly robust spring day, I was in a strong thermal passing through 10,000', when I noticed I was being smothered with spiders! Must have been tens of thousands of the soaring little rascals. They immediately collected on all of the wires (on my 180 Attack Duck), covering my face and helmet, and getting into my jacket through the collar. It was creepy, yet very cool. I remember thinking about how far these tiny guys could get on their cross country journey considering a 25+ mph tailwind drifting them from 12-15K feet out into the desert.

Another time, I was looking for a thermal (near Pine Flats) when I noticed an area of (red) dust in the air a few hundred yards away. I flew to the dust and began circling when I realized I was in a cloud of thousands of lady bugs. They out climbed me by a fair margin so I didn't fly with them for very long, however, we all gained 6-7K in that thermal. I guessed that a dust devil must have passed through a bush right after the hatch and lifted them into a journey to who knows where.
I had lady bugs crawling on me well into the evening.

I wonder what the reynolds number is for a lady bug?
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Re: Vine seeds become 'giant gliders'

Postby Bob Kuczewski » Fri Feb 19, 2016 4:28 pm

msoaring wrote:I wonder what the reynolds number is for a lady bug?


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Re: Vine seeds become 'giant gliders'

Postby KaiMartin » Sat Feb 20, 2016 11:29 am

ARP wrote:Further investigation on ballooning/kiting spiders shows that they may actually produce more than a single silk thread and so could be operating at higher Reynolds number after all.

". These spiders use tens to hundreds of silk strands, which form a triangular sheet with a length and width of about 1 metre (39 in)[5]"

With a hundred threads on one metre the average separation is 10 mm. This is about 1000 times the threads diameter. This is like two hang glider wings at a kilometre distance. Consequently, the relevant Reynolds number is not affected. The aerodynamics still operates firmly in the laminar regime. In the absence of aerodynamic lift the dynamics is all about friction.

---<)kaimartin(>---
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Re: Vine seeds become 'giant gliders'

Postby ARP » Sat Feb 20, 2016 11:52 am

It may have electrostatic forces though ?
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Re: Vine seeds become 'giant gliders'

Postby JoeF » Sat Feb 20, 2016 11:53 am

Consider the spider body as a kited wing corpus. Silks with the tension developed pull the spider body (a wing); the spider body (a wing) has lift and drag; the L/D changes during the flight. Notice how the tug of a line lauches sailplanes, hang gliders, etc. All kite systems. Hook a wing to a tugging tether set and presto: kited dynamics. The Reynolds Number for the spider's body?
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Re: Vine seeds become 'giant gliders'

Postby ARP » Sat Feb 20, 2016 12:14 pm

Joe:- " Hook a wing to a tugging tether set and presto: kited dynamics. "

Interesting, so the kite system is reversed kiting the spider which is the kite wing pulled by the kite line/silk and energy from the wind dragging the line/silk to lift the spider/kite wing.
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Re: Vine seeds become 'giant gliders'

Postby JoeF » Sat Feb 20, 2016 12:39 pm

It is actually both ways in any kite system: The anchor set is a wing set; the wing set is a wing set and an anchor set. A=W; W=A; both ways. Each is A to the other. It is so even in the classic soil-anchored single-line kite; the tether does not know which way is which; the soil anchor is a wing (soil wing) and the classic Eddy corpus is an air wing; the two wings are resisting each other: the soil wing is resisting the air wing; the air wing is resisting the soil wing; the soil media is pressing on the soil anchor wing; the wind is pressing on the air wing Eddy. It is so in any kite system, even if the anchor-set wing set is moving or falling or rising in some resisting media. The paragliding human pilot's body with harness and instruments form a wing set anchor for the Jalbert parafoil evolute ram-air wing set; the pilot's body is resisting the tug of the Jalbert parafoil evolute wing; the Jalbert item is resisting the tug of the pilot-body-gear wing; in this case both are in the same media. Upside or downside ... does not matter; kite systems have wings that go up, down, sideways. When the media is totally water for both wing sets, then one has a total water media kite system. When one of the opposing wing sets is in the air and one is in the water, then we have a mixed media situation. Indeed, every kite system is technically a mixed media system, as the media around one wing set is technically differently from the media fine tuned for the opposing wing set. Study FFAWE for more matters that see these things.
Same for the kiting spiders: the silk set end region forms a wing set; the silk gradually mid region develops tension and tugs at the spider corpus wing; likewise the resisting spider corpus on average sets up resistance and play its part in forming the tension in the silk tethers. Two wing sets and a tether set in a media; at first the spider is rooting in the plant or soil media to cause resistance; then when the spider lets go, she is in a modified air media; technically the air media about the spider wing corpus is never identical to the media condition at the far region of the silk set (other wing of the kite system).

Tension in a line is with arrows opposing each other: <----->
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