Date: Thu, 22 Sep 1994 15:33:57 -1000 From: Don_Watson@mindlink.bc.ca (Don Watson) Message-Id: <54528@mindlink.bc.ca> Organization: MIND LINK! - British Columbia, Canada Subject: Flexi-foil line strength While flying my 6' and 8' foot Flexi-foils in an ~18mph wind on Tuesday I broke my first flying line (150# Spiderline). Until this experience I had been somewhat dubious of the high line strengths recommended by most kite manufacturers. Interestingly, the line did not break at the knot but rather inside the sleeving: || /===================\ || ------------X -|| Handle ^ \===== =============/ || bare line ^ ^ ^ knot break sleeve I had thought that the weakest point of the line would be at the knot. Any suggestions as to why it might have broken where it did? It was brand new line with about an hour of flying time. Since I have just acquired a 10' Flexi as well, and want to fly it stacked with the 6 and 8, I'm trying to determine the appropriate line strength. I had purchased some 240# Spectra for this purpose but I'm now reconsidering ;^/ Flexifoil Int'l recommends a mimimum line strength of 88, 132 and 198 pounds for the 6, 8 and 10 foot kites respectively. If I simply add these together I will need 418# line! After reading some of Andrew Beattie's Flexi articles from the archive, 418# seems overkill for my little stack - and this doesn't even include derating the line to allow for the weakness of knots and cumulative wear. If I derate the line I will need to purchase >500# according to this method. How do others arrive at the line strengths needed when flying stacks of Flexis or other kites? Don -- don_watson@mindlink.bc.ca Sometimes a cigar is just a cigar dwatson@shlvan01.vancouver.mm2.shl.com Sigmund Freud = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 22 Sep 1994 22:58:35 -1000 From: gilchgw@zoology.washington.edu (George W. Gilchrist) Message-Id: Organization: Dept. of Zoology, University of Washington Subject: Re: Flexi-foil line strength In article <54528@mindlink.bc.ca> Don_Watson@mindlink.bc.ca (Don Watson) writes: >Interestingly, the line did not break at the knot but rather >inside the sleeving: Don, Is there any chance you damaged the line with the wires while threading on the sleeving? I've started knotting behind or cutting off the line at the crimp point to avoid this problem. I've observed some cut threads after a hard pull through tight sleeving. Cheers, George ============================== George W. Gilchrist gilchgw@zoology.washington.edu Department of Zoology NJ-15 University of Washington Seattle, WA 98195 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sun, 25 Sep 1994 21:56:30 -1000 From: andrewh@phoenix.harvard.edu (Andrew Hawken) Message-Id: <365ure$eua@beta.qmw.ac.uk> Organization: Queen Mary & Westfield College, London, UK Subject: Re: Flexi-foil line strength The probable key to line strength issue is "how much can you pull back" If you are not buggying, then you are not going to throw yourself violently against the lines (buggy in one direction, kite in the other) therefore you are not going to be able to pull with much more than your body weight. I am a fairly light dude, and have been flying up to 8 * 6ft foils on 300lb line in 25+mph winds with no problem. I think that paradoxically, lower winds or less kites may put more strain on the lines. Once you have passed the point of being able to fight back and hold your ground, and are into sliding along, then you offer much less resistance. The only line that I have snapped under strain was in 0 wind flying a stack of 5 flexis. "Zero wind so 80lb line should be more than enough!" Ha Ha Ha! Andy -- ____________________________Andrew Hawken______________________________ "However many ways there may be of being alive, it is certain that there are vastly more ways of being dead" R Dawkins. Home : 0895 420110 QMW : 071 975 5542 AIIT : 0494 677045 Email : A.Hawken@QMW.AC.UK = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sun, 25 Sep 1994 23:03:32 -1000 From: gaffer@ibmpcug.co.uk (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organiszation Subject: Re: Flexi-foil line strength Don Watson wrote: >Any suggestions as to why it might have broken where it did? Only fluke, damage or some other abnormality. Things don't always break they way that they are meant to. >Since I have just acquired a 10' Flexi as well, and want to fly >it stacked with the 6 and 8, I'm trying to determine the >appropriate line strength. I had purchased some 240# Spectra >for this purpose but I'm now reconsidering ;^/ 240 should be fine. I used to fly everything on 275. I only broke it when badly abusing it doing stuff in the water and other silly games. If you go too heavy, you kill the performance of the kites. Andrew -- The Kite FAQs are at ftp.hawaii.edu:/pub/rec/kites/faq/* = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Wed, 28 Sep 1994 03:20:30 -1000 From: mallen@etsd.ml.com ( Mike Allen ) Message-Id: Organization: ml.com Subject: Re: Flexi-foil line strength I guess Don Watsons "line breaking" incident yet again shows that with spectra the "weakest point" is in the line and not the knot. Boy, this should get JTavo rolling again on the whole sleeving isue again...... :-) Mike.... = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 29 Sep 1994 14:47:30 -1000 From: johnsen@eskimo.com (Brian Johnsen) Message-Id: Organization: Cap'n Puget's Roadside Tako Stand Subject: Re: Flexi-foil line strength In article , Andrew Beattie wrote: >Don Watson wrote: >>Any suggestions as to why it might have broken where it did? > >Only fluke, damage or some other abnormality. Things don't always break >they way that they are meant to. Spectra lines consist of several dozen monofilament threads braided together. Severing even several of these threads in various places along the the length does not significantly degrade the line rating because the braided structure sqeezes them all together and prevents them from slipping relative to each other. Line breaks occur when some threads are broken close together, like where the lines cross when you spin or at knots or other kinks where mechanical abraision occurs. You may want to check how you habitually wind up your lines when your'e done flying. Did it break where the sleeved portion of the line first crosses the card (or other device) you wind them up on? You may want to make your first couple of wraps slightly less tight. Then again, line ratings are computed from the design of the line. If you have X number of Y diameter thread made of Z material then; it should support W weight. The problem being that actually producing XYZ line in the real world is subject to manufacturing error. The only way to find out what any given line will support requires a destructive test which tends to break the line. -- "Killer Manic Depressive Tigers From Saturn Defenestrated My Ankle Biter" Confirms Julia Child -- Brian Johnsen johnsen@eskimo.com = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 3 Oct 1994 02:46:44 -1000 From: steven@cix.compulink.co.uk ("Steven Thompson The ") Message-Id: Organization: The Decisions Group Subject: Re: Flexi-foil line strength You say ....... > > > Since I have just acquired a 10' Flexi as well, and want to fly > it stacked with the 6 and 8, I'm trying to determine the > appropriate line strength. I had purchased some 240# Spectra > for this purpose but I'm now reconsidering ;^/ > > > How do others arrive at the line strengths needed when flying > stacks of Flexis or other kites? > I fly 3 ten foot flexis on 300lb line - the line has only broken in very strong winds - 30MPH plus (ie when you should not be flying a stack of 3). In general try to use the line at (or just below!) the breaking limit - otherwise large line diameters just create drag. If you want to protect your line use 'weak links' that connect the flying line to the tracers on the flexis - I use 270lb dacron for this purpose - if anything does break, its a 20cm piece of dacron, not an expensive 150ft piece of spectra. Tight lines! = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =