Date: Mon, 24 Oct 1994 05:28:06 -1000 From: jtavo@aol.com (JTavo) Message-Id: <38gjq6$mkp@newsbf01.news.aol.com> Organization: America Online, Inc. (1-800-827-6364) Subject: Knots and line strength (again) Sorry to start this subject again but I must. I have been running into people who go into convulsions when I tell them that I do not sleeve my line. The usual story about lines having half of the strength of sleeved line comes up and when I ask where they heard this they don't know. Others still state that if a line is going to break, it will break at the knot. I do not believe a lot of what I hear so call me skeptical. But, when I state something, I do not rely on the "they said" routine. I try to prove it to myself and that usually satisfies me. As for lines breaking at the knots, let me again tell you to prove it to yourself and try it at home like I did. I took Spectra from 80# to 200# and tied 3 simple overhand knots. I then pulled till the line broke. 4 times each and not once did it break at the knot!! It broke about 1-2 inches from the knot. I did the same experiment on new Dacron line of 100 and 200# test. Again, not one break at the knot.(repeated 4 times each) I also tried it on some 200 # skybond I had and the results are the same. One problem might be that the knots are not cinched down correctly. 90 0f a knots strength comes from finishing it correctly. I suspect that a lot of people have problems with using one knot on spectra. One knot will not hold and as the line is pulled, the spectra slips, causing friction, melting, and knot failure. Thats why I use 3 knots on spectra. Don't get me wrong, if you like to sleeve line and get satisfaction from it, go ahead! What ever floats your boat. But on the other hand, try not to go around life believing in what "they" say. If something bothers you then try to prove or disprove whatever "They" say. If someone can get me some hard data on lines and knots, I WILL listen but with a large grain of salt. Theories are worth something, but in theory, helicopters are not suppose to fly, but in the real world, they do. And in theory, lines should be sleeved, but I have not had that "theory" proved to me yet. Don't worry about it. have fun instead!! later, John = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 24 Oct 1994 00:08:45 -1000 From: crowell@teleport.com (Carl Crowell) Message-Id: Organization: Kites By Carl Crowell Subject: Re: Knots and line strength (again) jtavo@aol.com (JTavo) writes: >I took Spectra from 80# to 200# and tied 3 simple overhand knots. I then >pulled till the line broke. 4 times each and not once did it break at the >knot!! It broke about 1-2 inches from the knot. this is considered 'at the knot' by those that are in the trade. If you have 300 feet of line, and it always breaks in a zone that is three inches long, ther is obviously some influence. >If someone can get me some hard data on lines and knots, I WILL listen but >with a large grain of salt. Sounds to me like you have lots of data from the above experament... just look at it. >Theories are worth something, but in theory, >helicopters are not suppose to fly, but in the real world, they do. I theroize that you are not in the real world. Who ever told you that helocopters are not supposed to fly? You think that some one stumbled across the idea of the rotor wing? = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 24 Oct 1994 14:31:14 -1000 From: jbmike@aol.com (JBMike) Message-Id: <38hjki$583@newsbf01.news.aol.com> Organization: America Online, Inc. (1-800-827-6364) Subject: Re: Knots and line strength (again) In article <38gjq6$mkp@newsbf01.news.aol.com>, jtavo@aol.com (JTavo) writes: Yup.. JTavo is at it again. Actually, I must agree with him. I have not sleeved spectra for the past 3 years and have yet to have line break at the venerable knot. The idea of a "slipping knot" melting also makes sense as during my tests, a loose knot did tend to result in "heat induced fusion" at that point. Thats just my 2 cents worth. Safe flying........... Mike Allen... = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 25 Oct 1994 11:16:01 -1000 From: swann_m@a1filton.filton.bso.mts.dec.com (Mike Swann) Message-Id: <82424152014991_1373980@FILTON> Organization: Division of Applied Sciences, Harvard University Subject: Re: Knots and line strength (again) [This message is converted from WPS-PLUS to ASCII] According to Ashley (who is regarded as the authority on knots) any knot will weaken any rope, cord or line. His experiments indicated that a break will occur outside the knot, but adjacent to it. He also points out that the the "normal" testing method of increasing the load on the sample until it breaks, and recording the load at that time, doesn't bear much resemblance to the real world. If I remember correctly, his method uses a series of impulse loads. As an example, a sheet bend reduces a rope's strength by about 50 Naturally, the type of knot, the material and the method of use can affect the results. Personally I'll carry on sleeving 'cos I find it easier to handle, and intuitively (for whatever that's worth) cushioning the line seems right. Mike -- SWANN_M@BSO.MTS.DEC.COM = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 25 Oct 1994 04:53:01 -1000 From: jtavo@aol.com (JTavo) Message-Id: <38j64d$h43@newsbf01.news.aol.com> Organization: America Online, Inc. (1-800-827-6364) Subject: Re: Knots and line strength (again) In article <38gjq6$mkp@newsbf01.news.aol.com>, jtavo@aol.com (JTavo) writes: >>Stuff about Helicopters> See! Thats what "they" told me. I should have been more skeptical!! I will not try to disprove the helicopter thing... ;-) = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 24 Oct 1994 21:52:50 -1000 From: pp@wsinti09.win.tue.nl (Peter Peters) Message-Id: <38idgi$dvk@wsinti09.win.tue.nl> Organization: Eindhoven University of Technology, The Netherlands Subject: Re: Knots and line strength (again) jtavo@aol.com (JTavo) writes: >As for lines breaking at the knots, let me again tell you to prove it to >yourself and try it at home like I did. >I took Spectra from 80# to 200# and tied 3 simple overhand knots. I then >pulled till the line broke. 4 times each and not once did it break at the >knot!! It broke about 1-2 inches from the knot. I'm no knot or line professional, just curious... How did you pull ? Increasing weight until it broke. Or sudden jerks of a specific strenght ? I think there's a difference... >with a large grain of salt. Theories are worth something, but in theory, >helicopters are not suppose to fly, but in the real world, they do. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ says who ? :-) later, Peter. -- Peter Peters, pp@win.tue.nl, http://www.win.tue.nl/win/cs/fm/pp/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 25 Oct 1994 10:54:45 -1000 From: sasaki@das.harvard.edu (Marty Sasaki) Message-Id: <38jral$5cv@necco.harvard.edu> Organization: Harvard University OIT/NSD Subject: Re: Knots and line strength (again) I applaud John "The Anchor" Tavolacci's work on testing lines, but think that a more realistic test would be better. Let me suggest the following: 1. Make two loops out of heavish dacron, say 200 pound test. The loops should have knots on them to make them just like bridle attachment loops on many stunt kites. 2. Make a length of flying line with an unsleeved loop on one end and a sleeved loop on the other. 3. Attach one of the loops made in 1 above to something solid. 4. Attach one end of the line in 2 to the loop in 3 using a larks head. 5. Attach the other end of the line in 2 to the remailing loop from 1. 6. Now pull on the loop in 5 until the line breaks. You should try both steady pulls and sudden jerks to simulate strong steady winds and gusty winds. If you can, use a scale to measure how much force is needed to break the line. I have done the above experiment with dacron and nylon line of different types with different types of knots. I didn't try sleeving since at the time sleeving was rare or non-existant. My results were that the type of knot makes a big difference and that care in tying the knots also made a difference. I have also experimented with Kevlar. Kevlar has different characteristics though. It literally self destructs when the radius of curvature is too small and is abrasive enough that it can cut through itself. Sleeving increases the radius of the curves of he knots and provides some cushioning from Kevlar's abrasive qualities. With Kevlar sleeving really is significant. Having said this, it probably doesn't matter that much anyway. Most flyers use line that is heavier than it needs to be anyway. Heavier line is easier to handle, easier to knot and easier to un-knot and un-tangle. Heavier line also compensates for wear and tear on flying line. I once put a spring scale on some hard pulling rokkakus in 10 mph wind (measured from the ground). An 8 foot tall rokkaku pulled at around 20 lbs. The kite was being flown on 200 pound test line. Even if the knot decreased the line strength by half and the force was doubled, there was still plenty of margin for error. >If someone can get me some hard data on lines and knots, I WILL listen but >with a large grain of salt. Theories are worth something, but in theory, >helicopters are not suppose to fly, but in the real world, they do. And in >theory, lines should be sleeved, but I have not had that "theory" proved >to me yet. Helicopters have a large amount of theory behind them. Rotors are really interesting beasts. The angle of attack as well as the dihedral are changing all of the time. Procession also makes things very interesting. Most of "them" (by this I take it to mean aerodynamics folks) can show you all sorts of theory about how helicopters fly. The same is true of bumble bees by the way. A simple minded approach to describing how they fly does indeed yield the "fact" that they can't fly, but to someone who really understands aerodynamics (I'm not one of them) a bumble bee's flight can be described, it does not defy any aerodynamic laws or theories. -- Marty Sasaki Harvard University Sasaki Kite Fabrications sasaki@noc.harvard.edu Network Services Division 26 Green Street 617-496-4320 10 Ware Street Jamaica Plain, MA 02130 Cambridge, MA 02138-4002 phone/fax: 617-522-8546 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 25 Oct 1994 08:08:02 -1000 From: terryh@terminus.uk.sun.com (Terry Heatlie - Support Services - SunSoft) Message-Id: <38jhi2$910@uk-usenet.uk.sun.com> Organization: no thanks Subject: Re: Knots and line strength (again) In article <38idgi$dvk@wsinti09.win.tue.nl>, pp@wsinti09.win.tue.nl (Peter Peters) writes: |> jtavo@aol.com (JTavo) writes: |> [...] |> >with a large grain of salt. Theories are worth something, but in theory, |> >helicopters are not suppose to fly, but in the real world, they do. |> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |> says who ? :-) David Gunson. He says that really they should screw themselves into the ground :-) Regards, Terry Heatlie. -- terry.heatlie@sun.com (internet). terry.heatlie@sun.co.uk (JANET) ___ Disclaimer: all my own work (except this disclaimer, which I nicked). \ / *** I want to go to 'Frisco bay, drink my liquor and spend my pay *** V = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 27 Oct 1994 20:34:05 -1000 From: windwiz@coyote.rain.org (Dan Rubesh) Message-Id: <38q60t$9nl@coyote.rain.org> Organization: Regional Access Information Network (RAIN) Subject: Re: Knots and line strength (again) In article <38j64d$h43@newsbf01.news.aol.com> jtavo@aol.com (JTavo) writes: >In article <38gjq6$mkp@newsbf01.news.aol.com>, jtavo@aol.com (JTavo) >writes: > >>>Stuff about Helicopters> > >See! Thats what "they" told me. I should have been more skeptical!! >I will not try to disprove the helicopter thing... ;-) Along the same line as the helicopter theory, most any aerodynamics type can prove, with the numbers, that a bumblebee can't fly.. It doesn't ahve enough wing area to support its weight.. The poor dumb bumblebee can't read all of this crap and goes merrily on flying.. -- Tako Buggy Naked Kichi!! Dan Rubesh AKA Member/Merchant Wind Wizard, Purveyor of windwiz@coyote.rain.org GO Stunt Kites & Accessories danr@crash.cts.com FLY A P.O. Box 5747 (805) 659-5654 (voice) STUNT Ventura, CA 93005 (805) 659-5769 (fax) KITE! Member: Kite Trade Assn. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Fri, 28 Oct 1994 07:58:02 -1000 From: silntobsvr@aol.com (SilntObsvr) Message-Id: <38re3a$rp3@newsbf01.news.aol.com> Organization: America Online, Inc. (1-800-827-6364) Subject: Re: Knots and line strength (again) In article <38q60t$9nl@coyote.rain.org>, windwiz@coyote.rain.org (Dan Rubesh) writes: >Along the same line as the helicopter theory, most any aerodynamics type >can prove, with the numbers, that a bumblebee can't fly.. It doesn't ahve >enough wing area to support its weight.. The poor dumb bumblebee can't >read all of this crap and goes merrily on flying.. All that proves is that the aerodynamicists involved don't know as much as they think they do. If the bumblebee flies, it's because it >can< fly, not because it's too dumb to know it can't. In fact, the rules change mightily when you have wings as small as those on a bumblebee -- the air begins to get "sticky" and it starts to get more important to "sling" it than to have it flow smoothly around the wing. Don't worry, though, the bumblebees have it all sorted out, and have to millenia... +------------------------------------------------------------------------- --+ | SilntObsvr@aol.com | This .sig brought to you by the Geoworks Ensemble | | Owner/Operator of | 2.01 Text File Editor, substituting for features | | TableTop Publications | left out of the AOL newsreader. | +------------------------------------------------------------------------- --+ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Fri, 28 Oct 1994 23:38:01 -1000 From: raymiller@aol.com (RayMiller) Message-Id: <38t55p$f1g@newsbf01.news.aol.com> Organization: America Online, Inc. (1-800-827-6364) Subject: Re: Knots and line strength (again) In article <38gjq6$mkp@newsbf01.news.aol.com>, jtavo@aol.com (JTavo) writes: ... Others still state that if a line is going to break, it will break at the knot. Hi John, Good to hear you are still at the workbench making all right for the kiters. My contribution to the subject deals with what I know about the tests conducted by cordage and line companies. Most of the tests done deal with heavy line and hawsers, used for shipping and tackle. The lines tested have centered around natural fiber lines, cotton, manila, hemp, etc. vs. man-made fibers like nylon, polyester, dacron, and kevlar (more recently spectra, but I know of no "official" testing of this latest development by cordage companies). Since people can be killed and mamed, and property damage can be extensive should tackle fail, much testing has taken place regarding strengths of various materials used to construct rope, lines, etc. that are put under stress. Since knots, hitches, and bends are used to secure or tie together rope, all rope is tested with and without knots. Not having any specific tests to reference here, I can only say that it has been found that *A*L*L* rope has been found to be weaker with knots than without. I am sure if one were to contact Sampson Cordage (the maker of braided nylon and dacron rope used in recreational/competitive sailing, as an example), they would substantiate these claims. I believe that those who hear of these tests, usually far removed from any research on the subject, such as military duty training and the like, they remember only that rope is weakened by "knots" and do not really understand what is behind the claim. The tying of a knot twists and bends the rope in ways that can, and do, break and stretch individual fibres within the rope. The more the rope is tied at the same point, the more it is weakened at that point. The same can be true of "small stuff" like kite lines (super small stuff). The weakening happens over time, and therefore, must be tested in those conditions that cause the weakening. The length of the fibers and the tightness of the weave or twist of the rope affect the resiliance of the rope, thus affecting the amount of stretch and the overall strength. As a rope (or kiteline, for that matter) is stretched, it lengthens due to the inability of the fibers to return completely to their original size (length). After awhile, the fibers cannot stretch any longer, and they begin to fail and break. I hope this gives you some food for thought. By the by, I am still flying the big pink monster with my buggy. I love it, although it is slow and combersome compared to the Sky Tiger. Take care... = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sun, 30 Oct 1994 08:58:39 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: /usr/lib/news/organisation Subject: Re: Knots and line strength (again) raymiller@aol.com (RayMiller) writes: >Since knots, hitches, and bends are used to secure or tie >together rope, all rope is tested with and without knots. Prey tell, If one wishes to test the breaking strain of a line without knots, just how do you attatch it to the measuring device? Andrew -- You can FTP the kite FAQ's from ftp.hawaii.edu (directory /pub/rec/kites/faq) /-\ () >< () |\/| () >< () /-\ For sale: 10' Flexis with std & UF Spars, 10m Peel (I want the new reefers) What should I know? I can't even axel yet :-( = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 31 Oct 1994 14:38:02 -1000 From: hayden1009@aol.com (Hayden1009) Message-Id: <3942la$bav@newsbf01.news.aol.com> Organization: America Online, Inc. (1-800-827-6364) Subject: Re: Knots and line strength (again) In article , andrew@tug.com (Andrew Beattie) writes: >testing line strength without knots??? So, what about splicing the line (you know where you weave the end back into itself 3 or so times to get that chinese finger cuff effect). Would that put less stress on the line? Is that strong enough to hold the kites requiring 150# or 200# test? Of course, this is especially difficult if the line isn't braided. ;-) Alice = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 31 Oct 1994 14:23:06 -1000 From: mikeda@microsoft.com (Mike Daly) Message-Id: Organization: Microsoft Corporation Subject: Re: Knots and line strength (again) jtavo@aol.com (JTavo) writes about knot strength.... The various navies conducted lots of tests of line strength several centuries ago and developed standard tables of strength vs. diameter for the various rope materials. For example Manila Hemp is stronger than Sisal Hemp (and neither is the same as the Canabus flavor of hemp). There are also standard tables telling you how much to derate each line for the various types of knots and splices. I have seen these tables and I'm pretty sure you can find a copy in the two volume work "Masting and Rigging a Square Rigger" (Chapple?) (or perhaps a reference to some other work which may have it). Another source would be the folks at Mystic Seaport in Conn. I don't know if the sailing community worries about this anymore. Perhaps the lines and shrouds are over-built now. I've been thinking about how a knot weakens a rope and have some observations which may help: - a knot tends to cut into the line where the lines cross - when a line goes around a corner, most of the load is carried by the fibers on the outside of the turn so you have to stretch those fibers a bit before the inner fibers notice the load. You are only working with half the rope. - the knot may pinch the fibers and prevent them from slipping past each other and compensating for the load thus increasing the load on some fibers, perhaps to the breaking point. Mike Daly -- MikeDa@microsoft.com -- Microsoft Corp. -- 206.936.2202 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Wed, 2 Nov 1994 10:39:51 -1000 From: mark@murder.demon.co.uk (Mark de Roussier) Message-Id: <783833991snx@murder.demon.co.uk> Organization: damage Subject: Re: Knots and line strength (again) In article andrew@tug.com (Andrew Beattie) writes: > raymiller@aol.com (RayMiller) writes: > >Since knots, hitches, and bends are used to secure or tie > >together rope, all rope is tested with and without knots. > > Prey tell, If one wishes to test the breaking strain of a line > without knots, just how do you attatch it to the measuring device? > Clamp it over a fairly long length - i.e. friction ? Glue it to something using a glue you know ( or suspect !:) is stronger than the string ? -- Mark de Roussier ************************************ A nice man is a man of nasty ideas. Jonathon Swift. ************************************ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sat, 5 Nov 1994 15:45:11 -1000 From: Thom Shanken Message-Id: Organization: Delphi (info@delphi.com email, 800-695-4005 voice) Subject: Re: Knots and line strength (again) Hayden1009 writes: >So, what about splicing the line (you know where you weave the end back >into itself 3 or so times to get that chinese finger cuff effect). Would >that put less stress on the line? Is that strong enough to hold the kites >requiring 150# or 200# test? As you probably already know Alice, I am the unwavering advocate of the "No-knot" system. Although this usually requires braided line, it is possible to use the line splicing techniques found in most books on knots to create loops and such at the ends of non-braided lines (though it is, admittedly more difficult). I carry a "No-knot" tool with me at all times in my wallet, but a small length of piano wire would work just as well. It takes but a moment to either splice a broken line or make a loop at the line's end. By using a "No-knot" loop when making bridles, you not only get a nicer looking finished product (in my opinion), but, you may also use a "lighter" line. This, I find, is an advantage, not only in the area of weight and aerodynamic drag (the drag difference is probably minor), but, when it comes to bridles for large fighting kites, the thinner bridle line is a superior weapon against those evil adversaries who would try to cut your bridle with their flying lines. Thom :) (thomshanken@delphi.com) = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sun, 6 Nov 1994 16:49:07 -1000 From: raymiller@aol.com (RayMiller) Message-Id: <39k4j3$np8@newsbf01.news.aol.com> Organization: America Online, Inc. (1-800-827-6364) Subject: Re: Knots and line strength (again) In article , andrew@tug.com (Andrew Beattie) writes: ...Prey tell, If one wishes to test the breaking strain of a line ...without knots, just how do you attatch it to the measuring device? So glad you asked! The rope, line, twine, etc. is wrapped around a drum of sufficient size to NOT cause the same kind of strain as the sharp bends of a knot. Still other testing devices use a clamping mechanism that will clamp along a measured length of the object rope. The rope is clamped at both ends then pulled by one of the clamps which is metered to collect data re:tension on the rope at the time of failure. Pretty smart those engineer-types, eh?!? = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Mon, 7 Nov 1994 12:05:11 -1000 From: hayden1009@aol.com (Hayden1009) Message-Id: <39m8an$p33@newsbf01.news.aol.com> Organization: America Online, Inc. (1-800-827-6364) Subject: Re: Knots and line strength (again) In article , Thom Shanken writes: >by splicing you can user lighter lines for the bridles....an advantage on big kites >in fighting. So you are saying that the spliced line is infact stronger than a knotted line? The act of weaving the end through itself doesn't then weaken the line? And why are thinner bridle lines an advantage in a fight? Don't they get cut even faster? By the way, a few pieces of tape on my unevenly cut spreaders did the trick, the thing is not Rok solid. Thanks. Alice :-) | If you lives are what we make them, mine is now real solid. | Yeah, right! So what did Horatio know. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =