pkasdorf 0 #1 February 11, 2003 On this year’s February Safety Check of Parachutist magazine tetrahedrons are mentioned as a solution for guiding landing patterns. As it is stated “A tetrahedron is a pivoting arrowhead that points generally into the wind. It doesn’t twitch with every vagary of light, shifting winds. The wind has to be strong enough and steady enough in a new direction to matter to a jumper before a tetrahedron will react. The tetrahedron doesn’t always face exactly into the wind, but that’s not very important. It won’t change every 15 seconds and cause pandemonium in the landing area, and that matters more. Tetrahedrons are bigger than windsocks. Jumpers can read them from much higher and plan downwind, base and final approaches that will set them into favorable landing direction.” I would like to know where they can be available and if there is a sketch or drawing to guide the home making of one. Apparently they are big and heavy and can be made of lighter materials. Can anybody help me? HISPA # 18 POPS # 8757 Quote Share this post Link to post Share on other sites
RichM 0 #2 February 11, 2003 Quote Tetrahedrons are bigger than windsocks. Llama's are bigger than frogs! Oh, sorry, this isn't talk back Rich M Quote Share this post Link to post Share on other sites
quade 4 #3 February 11, 2003 Would you like a design for one or are you looking for just a general idea? http://www2.faa.gov/arp/pdf/5340-21.pdf Shows a wind "T" and a tetrahedron is a variation of that, but I can't seem to find an FAA document specifying that. BTW, is case anyone ever wanted to know EXACTLY how to build an FAA specified wind sock http://www2.faa.gov/arp/pdf/5345-27C.pdf.quade - The World's Most Boring Skydiver Quote Share this post Link to post Share on other sites
pkasdorf 0 #4 February 11, 2003 A design would be perfect but, at least, the general idea would help. Thanks. HISPA # 18 POPS # 8757 Quote Share this post Link to post Share on other sites
masher 1 #5 February 11, 2003 Anyone got a picture?-- Arching is overrated - Marlies Quote Share this post Link to post Share on other sites
quade 4 #6 February 11, 2003 I've been -pouring- over my pictures, but I don't seem to have anything! That's really weird. We have a really nice, large one at Perris and I can't believe it's not in the background of any of my photos!quade - The World's Most Boring Skydiver Quote Share this post Link to post Share on other sites
masher 1 #7 February 11, 2003 I would like to see one. I managed to do one of my approaches wrong a couple of weekends ago because I couldn't see our wind vanes clearly until about ~150 ft. That, and the fact that the wind at the LZ was about 180deg different to the main airport windsock about 400-500 m away... (thank god for flat turns and student canopies)-- Arching is overrated - Marlies Quote Share this post Link to post Share on other sites
ltdiver 3 #8 February 11, 2003 QuoteAnyone got a picture? Here you go! Tetrahedron at Perris. ltdiver Don't tell me the sky's the limit when there are footprints on the moon Quote Share this post Link to post Share on other sites
indyz 1 #9 February 11, 2003 The easy way to visualize a wind T: Take an airplane and put it on a pivot, so that it can freely spin 360 degrees. As the wind blows, the plane will turn until the nose points into the wind. A wind T is the same idea. It's just a big metal "T" with a vertical tail at the bottom end of the vertical "stick". The wide end of the T faces into the wind. The one at my home dropzone is very easy to read at opening altitude. You can see it in this photo, inside the white circle up and to the left of the jumper under canopy. The wind is blowing diagonally up and to the right. Quote Share this post Link to post Share on other sites
pkasdorf 0 #10 February 12, 2003 Thank you, Paul and also thanks to ltdiver and indyz. Thanks a lot! HISPA # 18 POPS # 8757 Quote Share this post Link to post Share on other sites
masher 1 #11 February 12, 2003 Thanks for all of that. I'll see what I can make happen...-- Arching is overrated - Marlies Quote Share this post Link to post Share on other sites
freakflyer9999 1 #12 February 13, 2003 Be careful about relying on a tetrahedron. Airports sometimes pin them in place to indicate the runway that you are to use. This may happen when a runway is temporarily closed or for other reasons. KG Quote Share this post Link to post Share on other sites
indyz 1 #13 February 13, 2003 QuoteBe careful about relying on a tetrahedron. Airports sometimes pin them in place to indicate the runway that you are to use. This may happen when a runway is temporarily closed or for other reasons. One day at the DZ the winds were light and variable, so the DZO pinned the wind T to indicate the landing direction. The winds kicked up, the T wasn't unpinned, and an entire load took downwinders. Lesson learned, always check the windsock as well as the T. Quote Share this post Link to post Share on other sites
masher 1 #14 February 13, 2003 That said, on the last load last weekend, the main windsock was wrapped around the pole, so she didn't work all that well...-- Arching is overrated - Marlies Quote Share this post Link to post Share on other sites
eames 0 #15 February 13, 2003 The whole point of a tetrahedron is to have a structure that's heavy enough that it doesn't turn in light winds. It should only turn if the wind is significant. It should never have to be pinned down. And if you're relying on a tetrahedron at the airport that may or may not be pinned down, build one specifically for the dz. Jason Quote Share this post Link to post Share on other sites
