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dbotos
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PostPosted: Wed Apr 05, 2017 9:11 am    Post subject: LZ windsock design details? Reply with quote #1   
Curious if anyone could share details on windsock construction that they have found to work well in conditions suitable for hang gliding. Such as:

1) Overall size. Thinking the biggest limitation here would be the length based on what height pole you mount it on.
2) Ratio of hoop diameter (big end) to throat diameter (small end). From looking around online, it appears most are roughly 2:1.
3) Ratio of length to hoop diameter. Most examples I found were roughly 3:1 or 4:1.
4) Fabric material and areal density (weight per area of material).
5) Special features:
a) Grommets around hoop diameter. Lets you quickly attach/detach from the support ring/frame with zip ties or similar.
b) Contrasting color tail end. Makes it easy to see direction of wind without having to use pole as reference or determine ends based on relative size. Yellow with a red or orange tail section seems like a rather visible color combo against brown/green earth and vegetation.
c) Tail streamers. A best of both worlds approach where some like socks and some like streamers? Would want them long enough to be functional, but not so long that they're getting tangled up together or wrapped around the pole.

Thanks,
David
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kukailimoku
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PostPosted: Wed Apr 05, 2017 9:49 am    Post subject: Reply with quote #2   
Tough to beat this for $15...

https://smile.amazon.com/Casualfashion-39-37-Windsock-Outdoor-Reflective/dp/B019KFU1JA/ref=sr_1_8?ie=UTF8&qid=1491414495&sr=8-8&keywords=windsock

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peanuts
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PostPosted: Wed Apr 05, 2017 10:03 am    Post subject: Reply with quote #3   
kinda like wind feathers, also
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blindrodie
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PostPosted: Wed Apr 05, 2017 10:04 am    Post subject: Reply with quote #4   
Quote:
Tough to beat this for $15...


Holy COW! Impossible!!

Cool

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dbotos
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PostPosted: Thu Apr 06, 2017 8:41 am    Post subject: Reply with quote #5   
kukailimoku wrote:
Tough to beat this for $15...

https://smile.amazon.com/Casualfashion-39-37-Windsock-Outdoor-Reflective/dp/B019KFU1JA/ref=sr_1_8?ie=UTF8&qid=1491414495&sr=8-8&keywords=windsock


That may be a good starting point to measure/modify if I end up experimenting with designs. My intention starting this thread was to see if there were any existing guidelines/knowledge out there about what works / doesn't work for hang gliding LZ applications. And maybe to have some open-source designs out there so any pilot could make their own and potentially tailor it to their needs/liking. There's a FAA document with airport windsock details, but those are pretty large and can handle much windier conditions than suitable for hang gliding:

https://www.faa.gov/documentLibrary/media/advisory_circular/150-5345-27D/150_5345_27d.pdf

Also note that they call the larger end the throat:

"3.3 Framework. A framework must be provided to hold the throat of the fabric windsock fully open under no wind conditions and to provide an interface with the support."

Of course, the manufacturer that I saw who called the small end the throat was Canadian, so maybe it's different North of the border (ehh).

I'm hang gliding for fun and if there's something I can spend a little time/money/effort on that makes it easier/safer, I certainly don't mind doing that.
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dbotos
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PostPosted: Thu Apr 06, 2017 8:56 am    Post subject: Reply with quote #6   
peanuts wrote:
kinda like wind feathers, also


It would be interesting to know if anyone's ever studied the perceptibility of various wind indicator styles (i.e. which style tends to be easiest to read) as well as how certain variables/features affect that (overall size, contrasting colored tail, streamers, etc.). One shortcoming I see of the feather (flag) is that its slender aspect ratio puts all the material pretty close to the pole. I suppose the curve at the top could be used for orientation provided you're not directly over top of it. Perhaps there are tweaks you could make to the feather flag as well (contrasting color trailing edge, trailing edge streamers, etc.).
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tizon
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PostPosted: Thu Apr 06, 2017 7:03 pm    Post subject: Reply with quote #7   
I use this windsock
http://www.ebay.com/itm/5-meter-15-foot-aviation-orange-windsock-PPG-Paragliding-paraglider-7-mph-/191687931840?hash=item2ca17db7c0:g:jD4AAOSwgQ9V0h1c

it's 15 foot long and shows all the little stuff in the air.
I have it on an old 10' surf fishing pole. When the wind is light, the sock will lay on the ground and show you the last direction the was blowing

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peterc
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PostPosted: Fri Apr 07, 2017 2:29 pm    Post subject: Reply with quote #8   
Some time ago, I witnessed a pilot in a competition land with about 8 mph tailwind. Didn't end well in case you were wondering. The main wind indicators in the LZ were these type of advertising flags, and from the air, it's pretty easy to determine the plane in which the wind is flowing, but the actual direction (180 degrees either way) can be misread fairly easily.

http://www.boldprintadvertising.com/flags.html
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dbotos
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PostPosted: Fri Apr 07, 2017 3:29 pm    Post subject: Reply with quote #9   
tizon wrote:
I use this windsock
http://www.ebay.com/itm/5-meter-15-foot-aviation-orange-windsock-PPG-Paragliding-paraglider-7-mph-/191687931840?hash=item2ca17db7c0:g:jD4AAOSwgQ9V0h1c

it's 15 foot long and shows all the little stuff in the air.
I have it on an old 10' surf fishing pole. When the wind is light, the sock will lay on the ground and show you the last direction the was blowing


That is like a wind snake! Does it have much taper or pretty much straight?. I like the fishing pole idea.
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dbotos
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PostPosted: Fri Apr 07, 2017 3:55 pm    Post subject: Reply with quote #10   
peterc wrote:
Some time ago, I witnessed a pilot in a competition land with about 8 mph tailwind. Didn't end well in case you were wondering. The main wind indicators in the LZ were these type of advertising flags, and from the air, it's pretty easy to determine the plane in which the wind is flowing, but the actual direction (180 degrees either way) can be misread fairly easily.

http://www.boldprintadvertising.com/flags.html


I know that feeling of your upper body moving faster than your legs can run. Jumped off a skateboard in my youth that was moving too fast and getting speed wobbles. When my legs got sucked out from under me, I turned onto my left shoulder/side as I went down (figured that would be better than going face first and I could tuck my head to my chest to keep it off the pavement). Got some decent road rash, but more impressive were the melted and smeared portions of the polyester/cotton blend T-shirt I was wearing. No desire to have similar happen while tethered to 50+ pounds of glider.
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Dave Gills
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PostPosted: Fri Apr 07, 2017 6:46 pm    Post subject: Reply with quote #11   
I bought several wind socks when I started including a very expensive silk one.
They were all disappointing.

Here I read about someone using unperforated toilet paper & driveway reflector sticks (just sticks w/ reflective tape)
That worked better for light wind but the visibility was still just not there.

My solution is getting golf hole flag sticks & unperforated paper hand towels.
The paper will indicate better than any sock I've tried.

I use 2 lengths of paper.
One to the top flag hole & one to the bottom.
The golf flag holder is designed to spin 360 degrees.

Golf courses renew their sticks every so often and I get mine for free.
The hand towels come from work.

You only have to land downwind once to make you never trust a sock again.

I got an apology once from someone who used part of one of the streamers for toilet paper. Mr. Green

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dbotos
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PostPosted: Sat Apr 08, 2017 3:41 am    Post subject: Reply with quote #12   
Interesting. Looks like those golf flag poles are about 7.5 ft tall. So you're making a sort of dual flag/streamer with paper towels? How long are the sections of paper towel that you put on there? Wonder if there's a fabric with similar areal density and stiffness to those commercial paper towels. Might have to go weigh a section at work on Monday.
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dbotos
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PostPosted: Sat Apr 08, 2017 3:54 am    Post subject: Reply with quote #13   
Since accurate wind direction indication seems to have priority over wind strength indication (at least for landing), I wonder if some type of large (yet lightweight) wind vane placed atop a pole (either on its own or sharing the pole with some other type of wind indicator) would be beneficial. Perhaps made from expanded polystyrene insulation board. You could install a plastic bushing in the foam where it pivots and then have a well-polished stainless steel pin/rod on the top of the pole that it mounts on.
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Dave Gills
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PostPosted: Sat Apr 08, 2017 9:04 am    Post subject: Reply with quote #14   
Often, I've been in the pattern and seen all the flags & socks indicating no wind only to spot mine slightly deflected.



The length of the towels makes it so they just clear the ground when the pole is planted (6 1/2 to 7')
I tried very expensive light silk and it didn't work as well as free hand towels.
I looked for cloth made from "juggling scarf" material but never found it.

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PostPosted: Sat Apr 08, 2017 11:18 am    Post subject: LZ windsock design details? Reply with quote #15   
Dave Gills wrote:
Often, I've been in the pattern and seen all the flags & socks indicating no wind only to spot mine slightly deflected.
http://i50.photobucket.com/albums/f312/dlg208/IMG_0520_zpsq3chdq2t.jpg
The length of the towels makes it so they just clear the ground when the pole is planted (6 1/2 to 7') I tried very expensive light silk and it didn't work as well as free hand towels.
Campers,

I use a similar set-up, but with the cheapest, toughest single-ply toilet tissue. Use a tall pole (skinny old leading edge) or any smooth, no-snag pole. The top streamer is as long as possible without touching anything except the pole. The bottom streamer is maybe one yard (meter) shorter. Attach the streamers to the pole with rubber bands (nothing else), as far as possible from the perforations in the tissue. Slap the tissue on the pole, roll the rubber bands down the pole onto the tissue, done deal.

With any breeze, these two streamers pick up and usually form a large white V that sharply points into the wind. It is visible for miles, from the air. The one-yard separation of the streamers at the top of the pole is important; it keeps the two streamers from twining around each other.

Streamer material then is cheap, and it stands up to very strong winds. It's always a good idea to have toilet tissue on the truck, anyway . . . Laughing

Mr. Green

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Dave Gills
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PostPosted: Sat Apr 08, 2017 6:45 pm    Post subject: Reply with quote #16   
I'm going to try red Nylon Chiffon fabric next winter because the white is so hard to see in the snow.

Maybe this.

https://www.etsy.com/listing/62859691/nylon-chiffon-fabric-you-pick-color-4

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dbotos
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PostPosted: Mon Apr 10, 2017 9:10 am    Post subject: Reply with quote #17   
dbotos wrote:
Wonder if there's a fabric with similar areal density and stiffness to those commercial paper towels. Might have to go weigh a section at work on Monday.


Continuous white bleached commercial paper towel from Kimberly-Clark dispenser (not sure what brand the towel actually is). 7.75" x 12" piece weighed 1.72 grams on the R&D lab scale that reads to three decimal places in grams. Doing the math, that's an areal density of about 0.85 oz. / yd^2. Found some nylon that's roughly that weight:

https://dutchwaregear.com/argon-90.html
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DMarley
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PostPosted: Tue Apr 11, 2017 7:42 am    Post subject: Reply with quote #18   
In my main pasture (LZ) on my farm I have a line of 3/8" diameter x 5' tall white fiberglass rods with florescent hot pink survey tape at the tops. These are spaced out at about 12 yards, for approximately 400 yards. They are very flexible so if you run over a few, it's no biggie. The LZ / pasture is quite undulating with a treeline 100 yrds away, parallel to the major dimension of the field. Always helpful to see what the air is doing across the whole field. These are great for doing uphill sprints as well, timing myself between 7 posts. Gotta keep the legs quick and strong for those launches!
Also, I constructed a main wind indicator with just 2" diameter PVC pipe that stands 20' AGL on the highest hump in the field. I have the same survey tape streamers attached up and down that pole and it is very easily seen from the air. A 1" diameter x 7' tall fiberglass post is driven 2' into the ground and the PVC pole is slipped over the post. The nice thing about the PVC is that if somehow I hit it, it will either bend out of the way, or break. And it is very inexpensive. The survey tape can be replaced once a season. The stuff flies in 2 mph breezes.
Fiberglass fence posts can be found at many farm fencing supplies websites, or are super-inexpensive if you can find a surplus sucker-rod supplier near you.
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dbotos
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PostPosted: Tue Apr 11, 2017 8:33 am    Post subject: Reply with quote #19   
Doug,

That is a good point about multiple wind indicators around an LZ. I flew at Blue Sky this past weekend and the wind was a little weird - it'd be coming in fairly straight at launch and then further down the runway it was 90° cross.

I have a length of flagging tape on a fiberglass driveway marker pole that I stick out in the dirt by the driveway when I use the pressure washer or leaf blower so I can see which way exhaust or debris are going to get pushed by the wind. It does seem pretty responsive and very cheap (Home Depot has the 600 feet of the 1" wide orange for $5). The driveway marker came with a little vinyl cap on the end, so I just popped that off, laid the end of the flagging tape over the tip of the pole, and replaced the cap, pinching the flagging tape in place.

Bendy poles seem like a good idea too. I donked one of Steve's big feather flags with the left wingtip on one flight when I was coming in for a landing this weekend (got pushed over to that side of the runway and didn't have enough altitude to turn away from it sufficiently). It didn't spin me or do anything crazy and the leading edge of the glider was fine (good thing cause I was test flying someone else's glider that they were selling).

One thing I've noticed with a single streamer on a pole is it's sometime difficult to quickly discern direction if you're at the same level as the streamer. If it's rotated around in the azimuth (angle going around the pole; i.e. wind direction) it can almost just look like a shorter streamer. Sometimes you just have to watch it for a bit and as it makes (slight) changes, you get a better sense of what it's doing in both angles (wind strength and wind direction). The higher you are above a streamer, the easier it is to tell direction (assuming you can tell which end is attached to the pole).

David
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dbotos
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PostPosted: Tue Apr 11, 2017 8:39 am    Post subject: Re: LZ windsock design details? Reply with quote #20   
red wrote:
The top streamer is as long as possible without touching anything except the pole. The bottom streamer is maybe one yard (meter) shorter. Attach the streamers to the pole with rubber bands (nothing else), as far as possible from the perforations in the tissue. Slap the tissue on the pole, roll the rubber bands down the pole onto the tissue, done deal.

With any breeze, these two streamers pick up and usually form a large white V that sharply points into the wind. It is visible for miles, from the air. The one-yard separation of the streamers at the top of the pole is important; it keeps the two streamers from twining around each other.


red,

I like that dual streamer idea. Does the longer streamer at the top tend to make less of an angle with the pole due to its weight? Like this:



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