Date: Wed, 27 Oct 1993 11:41:39 -1000 From: salanne@convex.csc.FI (Simo Salanne) Message-Id: <1993Oct27.214139.20294@funet.fi> Organization: Finnish University and Research Network FUNET Subject: MPS-bridle MPS-BRIDLE In August 1993 rec.kites had some discussion about the ways to make long trains of kites. One suggested technique was to use Prusik knot... ******** Begin excerpt ********************************************** ~To: kites@das.harvard.edu ~Date: Thu, 19 Aug 1993 04:25:51 -1000 ~From: reich@cod.nosc.mil (Ronald S. Reich) ~Subject: Prusik knot Sorry for butting in but I thought this could help in the discussion. 1. Make closed loop 2. Lay knot of closed and lay under line loop over line. ___________________ ___________________ | | | | | | | \ / | | | | & | Line | | | / \ | ===========================================|=|================ | | | / \ | | | | / \ | \ / \__/ \__/ \ / \ / \ / \ / & / \ \ / Wrap knot around line & inside of loop. / \ ___________________ | | | | | | | | _____________________ | __ __ | | _ _ | | _ _ | Line | / \ / \ | | | | | | | | | | | | | ==============|=========|==========|===|===|=|===|===|================== \__/ | | \__/ |_| |_| |_| |_| |_| |_| \ / & Go around 2 or 3 times / \ and then tighten all wraps. P.S. This knot is proposed for use in training Flexifoil kites when you want the strong line to run the full distance to the top kite. Still Learning and Sharing, Ron Reich ******** end excerpt ********************************************* I am not making long Flexi trains from my one and only Flexi, but I started to experiment with the Prusik knot in a delta stunt kite bridle. I have been using a bridle, which consists of three or four separate legs, each having a sliding-non-sliding knot for adjusting the lenght. I learned the idea and knot from Pierre Marzin, but don't know any name for the knot. The knot usually worked very well, but in light winds, when there was no continous tension, it slided on jerks when it shouldn't. The same could happen in heavy winds. I have now replaced the knot with U-Prusik and reversed the leg. I use Prusik knot in two modes: sliding and locking. Sliding mode is the normal Prusik, as explained by Ron. It locks when the 'line' is bent to U-shape 'inside' of the knot -> U-Prusik. I apply the loads on the one end of the line and on the loop - the other line end is hanging free (or tied loosely around the loaded line to make it tidy). One bridle leg looks like this: Prusik / / ==========&----------------------------------&&&~~~~~~~~~~~~~~& &&&~~~~~~~~~~~~~~ \ / overhand / overhand knot | knot The loop which is used to make the Prusik knot, is lark's headed to the frame in the conventional way. After the legs are connected to the frame, the other ends of legs are collected with a loop and lark's headed together. The overhand knot on the loop serves as stopper for flying line, lark's headed behind it. To make a three-leg bridle (both sides) you need: - 6 leg lines, with overhand knot on one end - 8 loops (about 12-15 cm long), made using overhand knot - 6 Prusik knots connecting a leg line and a loop - 2 of the loops lark's headed to collect legs together Use some harsh textured line, strong and thin enough. To make the bridle will easily take more than an hour, but it's worth the effort; you can adjust the tow point up/down and in/out 'independently'; unlock the Prusik, pull line, lock again. In 'normal' 3-leg bridle up/down ajustment results also in/out or out/in movement, depending which leg has fixed length. Let's call it MPS-Bridle (it's on your intellingence to figure out the "MPS":-), unless there are others, who have invented the same wheel. You may freely use MPS-Bridle, also in commercial products, but please, don't apply for a patent! Smooth Winds Simo.Salanne@csc.fi P.S. Similar legs can be used e.g. in Rokkaku tensioning lines. -- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 28 Oct 1993 01:01:13 -1000 From: swann_m@filton.enet.dec.com Message-Id: <9310281100.AA13310@vbormc.vbo.dec.com> Organization: Division of Applied Sciences, Harvard University Subject: re:MPS-bridle Simo described the MPS-bridle using a Prusik knot. I've been happily calling the same knot a Catspaw. I've devised two bridles based around this knot, one for development and one for final use. I've been calling the final use type the "Swann bridle", so I guess I'm just not as modest as Simo :>). Just a thought. This is not intended as a "counter-claim", but simply to continue the discussion Simo started. Sorry if the following reads a bit awkwardly, I've just pulled in the article I did for the club magazine. When you make a new kite, it can be pretty frustrating fiddling around tuning the bridle. I made the development bridle to overcome some of the problems, but you still have to do some preliminary guessing about general dimensions. After finalising the bridle dimensions, I like to have a bridle with no hardware, minimum knots, and some limited adjustment. With both of these bridles, I use a catspaw. This is like a larkshead, but taken around twice or three times instead of just once. I have used both bridles made from 200lb spectra/dyneema, and see no reason for them not to work with other materials. I've had no slip problems even in strong winds. Development bridle. Take a line the length of main bridle, plus twice the outhaul. This is the "bridle". Tie a loop in a separate piece of line about 6 inches long. This is the "lower attachment loop". Tie a loop in another separate line about 6 inches long. This is the "point loop". Larkshead the lower attachment loop to the lower leading edge attachment point. Put the bridle through the lower attachment loop and larkshead one end to the top leading edge attachment point and the other to the spine. Catspaw the point loop to the doubled bridle coming from the lower attachment. Et voila. Adjustments can be made be popping the catspaw and sliding whichever part of the bridle necessary to get what you want. Swann bridle I use the standard configuration of main bridle from low spine to top of leading edge, with an outhaul from low on the leading edge to join the main bridle. Tie a loop 3" long in the end of the outhaul. Select a point on the main bridle to attach the outhaul. Form a loop in the main bridle at this point, but don't tie it. Make a catspaw with this loop and the one on the end of the outhaul. When you pull on the outhaul loop, it forms the catspaw into a it's "locked" form, and grips firmly onto the main bridle. To adjust the position on the main bridle, pull on the main bridle on each side of the join. This pulls the main bridle straight, and pulls the catspaw into it's "unlocked" form allowing the outhaul to slide up and down. Pull on the loop, and it pops back to locked. Mike = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 28 Oct 1993 04:53:59 -1000 From: salanne@convex.csc.FI (Simo Salanne) Message-Id: <1993Oct28.145359.5836@funet.fi> Organization: Finnish University and Research Network FUNET Subject: Re: MPS-bridle In <9310281100.AA13310@vbormc.vbo.dec.com> swann_m@filton.enet.dec.com writes: > Simo described the MPS-bridle using a Prusik knot. I've been > happily calling the same knot a Catspaw. I've devised two bridles > based around this knot, one for development and one for final use. > I've been calling the final use type the "Swann bridle", so I > guess I'm just not as modest as Simo :>). > > Just a thought. This is not intended as a "counter-claim", but > simply to continue the discussion Simo started. > Did I understand right? Your development bridle has CONSTANT total lenght and Swann bridle has adjustable outhaul lenght but the main bridle is of fixed lenght? If you change the lenght of tow point to upper LE, you also change the lenght of tow point to spine leg which affects to relative in/out position? You can compensate it by changing the lenght of outhaul, but you must slide two knots, when I can manage by sliding one. Changing two things at the same time makes more difficult to to understand their effect. MPS-bridle has all legs, three or four or..., with adjustable lenght. I can change e.g. tow point to upper LE leg, without changing the other two. Because all legs are separate, it's very easy to attach the legs to frame, there is no need to disassemble the frame first. I have no need to have separate development and final bridle. MPS-bridle works fine in competition finals, too:-) Smooth Winds Simo -- = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =