Date: Thu, 2 Jun 1994 09:49:56 -1000 From: wede@mike.egr.msu.edu (Henry Wede) Message-Id: <2sld54$kp1@msuinfo.cl.msu.edu> Organization: College of Engineering, Michigan State University Subject: Re: Air cloth (ZP fabric) Hi all, I am a parachute rigger (and a student, but that's not inportant right now) and wanted to throw in my two cents about "ZP" fabric. Basically, it is standard ripstop nylon with a poly-something coating. It does not allow any air to pass through the fabric. It is called both "zero porisity" fabric as well as ZP fabric. I can't remember the weight of this fabric - I'll look it up this weekend.... The big deal for skydivers: using ZP fabric to construct canopies (the ram-air style) allows the canopy to maintain a higher pressurization and hence be a more rigid airfoil. Once the designers can count on a more rigid airfoil they can get more radical with their designs while still not killing (most of) us. One final note: I have been wanting to build a couple kites just to try something different. I have been lurking around for a month or so and picked up a couple catalogs and addresses. When I get a chance to sift through all the stuff I hope to write a moderately intelligent post, probably begging for some help and suggestions. It is much easier to learn >From other peoptles mistakes! Until then, take care. Blue Skies, Henry J. Wede P.S. If you ever want to be suspended under a kite-like device.... Of course, this does entail half of a plane ride. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 2 Jun 1994 21:06:53 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Air cloth (ZP fabric) >[I] wanted to throw in my two cents about "ZP" fabric. Thanks. Is ZP a generic term or a specific fabric by a particular manufacturer? >Once the designers can count on a more >rigid airfoil they can get more radical with their designs while still not >killing (most of) us. Performance soft kite design and Performance jump chute design overlaps somewhat, but the fact we don't have to cope with opening shock and that collapse leads only to a re-launch, not death and injury means that we can design much loser to the edge. Some stuff about my Peel: 107 square foot (10 m^2) nominal area 3/4 oz ripstop polyester Bridled in 80lb and 120lb Spectra Eliptical shape Aspect ratio better than 5:1 Bridled forward to within a few mm of the point where it will collapse Turning circle radius less than span (with partial collapse) Will deflate without collapsing Not cross-vented (not appropriate for tight turning) Whilst I don't expect you to turn us into qualified riggers by Email, many of us may appreciate learning firsthand how the pros get the canopy to inflate first time, out of the bag. Andrew -- Yes Karen, some of us *do* care! Netiquette-of-the-day: Take care to attribute quotes correctly. You can FTP the kite FAQ's from ftp.hawaii.edu (directory /pub/rec/kites/faq) The FAQ's have lists of kites, kite stores, kite questions, kite books & plans. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 6 Jun 1994 07:32:25 -1000 From: wede@papa.egr.msu.edu (Henry Wede) Message-Id: <2svmj9$o8v@msuinfo.cl.msu.edu> Organization: College of Engineering, Michigan State University Subject: Re: Air cloth (ZP fabric) Andrew... 1) "ZP" is just a generic term. We're basically lazy. The only tradename that comes to mind is "SoarCoat". Oh, and "ZP3". 2) [description of 107 ft^2 kite] This is really strange for me to read! The parachute I normally jump with is 110 ft^2. This is not overly common however, this is the smallest canopy on the airport. The suspended weight is about 150 lbs (me + gear). The canopy is made of 9 cells, with each cell divided in two by a rib with three cross ports. Suspension lines are made of 825 lb spectra and terminate at four connector links on the harness. With my weight, the canopy has a 30-35 mph forward speed. Turns are such that I can see the horizon (and houses, etc.) OVER the trainling edge of the canopy durning a hard turn. Obviously, turning really low is not recommended! Although a small (relatively speaking) turn before landing can make the landing spped aproach 60+ mph. Definately not for the more inexperienced jumper. As with your kites (soft kites? correct term?) stability can be a problem. THe crossports tend to increase pressurization form cell to cell. A closed end cell after a hard turn is not too uncommon for most canopies. The wing loading has a lot to do with it. A loading of 1:1 (1 pound per square foot) is standard with loadings of 1.5 and above bordering on crazy! It then becomes very easy to get injured with a properly inflated parachute.... what a starnge world. 3) As far as openings: modern equipment opens VERY reliably once you give it a chance. In a nutshell, while keeping all the slack out of the lines you hold the canopy upside down, straighten out the fabric and lines so that nothing gets burned or tangled, then you wrap the back section (center top) around the whole mess and place it on the ground. Then, you "cacoon" it so that is only about a foot wide or so. "S" fold the cacoon back on itself a couple of time so that is cube shaped and place it into a deployment bag. Here's the cool part, the bag is held closed by the suspension lines being stowed on the outside of the bag by rubber bands. Deployment is started when the bag(and stowed line) gets into the airstream by a hand- deployed small (30") round parachute. THe lines unstow, the canopy comes out of the bag and inflates, expanding from the center out. Control is by two lines attached from the rear corners of the canopy to handles near the container. Believe it or not, THAT was a summary! Sorry I got carried away. Anyway, enjoy. Henry Wede = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 6 Jun 1994 20:42:32 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Air cloth (ZP fabric) wede@papa.egr.msu.edu (Henry Wede) writes: >The suspended weight is about >150 lbs (me + gear). [Andrew must admit to about 190] >The canopy is made of 9 cells, with each cell >divided in two by a rib with three cross ports. So each cell has two vents at the front and one set of bridles? I think tht most kite fliers would have counted 18 cells on your 'chute. The Peel is unusual in not being cross-vented. Mine has 31 ribs of which 15 have bridle lines. There are 4 bridle attatchments per rib (with no ugly webbing loops to drag on the air), which cascade 4-1 about (guess) 1/5 of the distance from the canopy to the bridle point. The kite is cross-bridled. This means that the left hand bridle point has attatchments to the right of the canopy as well as the left. This gives better canopy shape during turning (we turn tight and often compared to a jumper). Note that we turn by pulling the whole bridle - like if you were to do a left turn by grabbing both main straps on the left and yanking them down by a few feet. The cross bridle ensures that the canopy maintains a decent shape as you do this - the whole thing will continue to fly (spinning tightly) with one line released, provided that you do it carefuly. This has the major advantage that it does not involve applying a brake to slow anything down. >Suspension lines >are made of 825 lb spectra and terminate at four connector links on >the harness. Mine is 125lb and 80lb spectra as I recall. > With my weight, the canopy has a 30-35 mph forward speed. My speed is limited by how hard I can pull it. I have no figures, but I think that I should be able to exceed 30-35 by a comfortable margin. >3) As far as openings: [Andrew goes away to experiment...] >enjoy. Thanks. Andrew -- Yes Karen, some of us *do* care! Netiquette-of-the-day: Take care to attribute quotes correctly. You can FTP the kite FAQ's from ftp.hawaii.edu (directory /pub/rec/kites/faq) The FAQ's have lists of kites, kite stores, kite questions, kite books & plans. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =