Salamander advertises that their tow ropes float, and are highly visible. In a recent workshop, a student made a presentation on towing with a tow rope that sinks to the bottom, leaving only the storage bag floating. So, here is the question. Is it really an advantage that the length of a tow rope floats? I can see one disadvantage. If the thing is floating all over the surface, the chances of getting entangled with it are a lot higher. opinions? - Julio *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
I don't know what Salamander makes their ropes out of, but many floating ropes (e.g., water ski ropes) are made out of polypropylene (sp?), which has very little stretch. Stretch is undesirable in many ropes, but something I would definitely want in a tow rope. It would make the tow experience less jarring, and easier on the attachment points, I think. I believe that polypropylene also has less strength at a given diameter, and relatively poor wear characteristics. But maybe they use another material? Chris On Mon, 25 Jan 1999, Julio MacWilliams wrote: > Salamander advertises that their tow ropes float, and are highly > visible. > > In a recent workshop, a student made a presentation on towing with > a tow rope that sinks to the bottom, leaving only the storage bag > floating. > > So, here is the question. Is it really an advantage that the length > of a tow rope floats? > > I can see one disadvantage. If the thing is floating all over the > surface, the chances of getting entangled with it are a lot higher. > > opinions? > > - Julio > *************************************************************************** > PaddleWise Paddling Mailing List > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.gasp-seakayak.net/paddlewise/ > *************************************************************************** > *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Yes, you are right. That is why good tow systems have a shock cord. The advantage of polypropylene versus climing nylon ropes, is the resistance to UV light and salt. A mountaineering rope should be disposed of (manufacturer recomendation) after if falls into salt water. However, I would like to stick to the initial topic: would it be better that the length of the two line stayed underwater, instead of floating all around? cheers, - Julio > > > I don't know what Salamander makes their ropes out of, but many floating > ropes (e.g., water ski ropes) are made out of polypropylene (sp?), which > has very little stretch. Stretch is undesirable in many ropes, but > something I would definitely want in a tow rope. It would make the tow > experience less jarring, and easier on the attachment points, I think. > > I believe that polypropylene also has less strength at a given diameter, > and relatively poor wear characteristics. > > But maybe they use another material? > > Chris > > On Mon, 25 Jan 1999, Julio MacWilliams wrote: > > > Salamander advertises that their tow ropes float, and are highly > > visible. > > > > In a recent workshop, a student made a presentation on towing with > > a tow rope that sinks to the bottom, leaving only the storage bag > > floating. > > > > So, here is the question. Is it really an advantage that the length > > of a tow rope floats? > > > > I can see one disadvantage. If the thing is floating all over the > > surface, the chances of getting entangled with it are a lot higher. > > > > opinions? > > > > - Julio > > *************************************************************************** > > PaddleWise Paddling Mailing List > > Submissions: paddlewise_at_lists.intelenet.net > > Subscriptions: paddlewise-request_at_lists.intelenet.net > > Website: http://www.gasp-seakayak.net/paddlewise/ > > *************************************************************************** > > > > *************************************************************************** > PaddleWise Paddling Mailing List > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.gasp-seakayak.net/paddlewise/ > *************************************************************************** > > *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Julio MacWilliams wrote: > So, here is the question. Is it really an advantage that the length > of a tow rope floats? > > I can see one disadvantage. If the thing is floating all over the > surface, the chances of getting entangled with it are a lot higher. If it sinks, it could get entangled on stuff you can't see and you'll lose your tow rope. Or the snag will result in two boats in trouble. WW paddlers always prefer floating rope for these reasons. One thing - a little off topic - that I've been thinking about the past couple of days is: how strong should the tow rope be? New rules in Canada require "buoyany heaving lines" at least 15 metres long on all kayaks. I've checked the web site Philip has pointed us to and can't find anything on how sustantial the heaving line should be. WW paddlers usually use 450 kg (1000 lb) static load for rescue ropes and most tow ropes I've seen are about 225 - 300 kg (500-650 lb approx). On the other hand, I don't think I want to handle more than 100 kg* tension unless I'm on land with a solid object to attach to. Light line is murder on the hands, heavy line is easier to pull, but won't break until after it's damaged you. I've thought of, say, 250 kg line with a weak point on the tow system of 100 kg capacity. That way under tow it will limit its effect on me but the basic line strength is there when I need it. *100 kg allows for some reserve for impact loading. When paddling a kayak that's still a _lot_ of force. Mike *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
That is a good argument in favor of braided polypropilene lines. They are light and bulky, float, and are easy on the hands. The initial 300+lb shock, should be absorbed by a shock cord, not the paddler nor the boat. Actually, the 300lb number sounds low to me. The UIAA tests climbing ropes by letting a 80kg mass fall with 1 meter of rope. That produces the 2000kg that the rope is expected to withstand. A rope would brake for two reasons. Either is does not take 2000Kg, or it does not stretch enough, which would create a force way over the 2000Kg pull. Let us see (boring discussion ahead). 3 knots = 1.5 meter/second (+or-). 50lb kayak + 180lb paddler = 230lb = 104Kg equivalent Energy = 1/2 * m * v^2 = 0.5 * 104 * 1.5^2 = 117 Joules to dissipate ^^^^^^^^^^^^^^^^^^^^^^^ Energy = Force * distance; therefore; Force = Energy / distance Hence, For 25 cm stretch, (if the rope stretched with constant force, which does not; at some intant, therefore, there are even higher forces) Force = 117 / .25 = 468 Newtons, equivalent to 103lb of shock. ^^^^^ not too bad. For 4 cm stretch (no shock cord) Force = 117 / .04 = 2925 Newtons, equivalent to 644lb of shock. ^^^^^ not me!, thanks :-{ For 0 stretch, Force = 117 / 0 = infinity If my physics are too rusty, please let me know ASAP. ;-) - Julio > > One thing - a little off topic - that I've been thinking about the past > couple of days is: how strong should the tow rope be? New rules > in Canada require "buoyany heaving lines" at least 15 metres long > on all kayaks. I've checked the web site Philip has pointed us to > and can't find anything on how sustantial the heaving line should > be. WW paddlers usually use 450 kg (1000 lb) static load for > rescue ropes and most tow ropes I've seen are about 225 - 300 > kg (500-650 lb approx). On the other hand, I don't think I want to > handle more than 100 kg* tension unless I'm on land with a > solid object to attach to. Light line is murder on the hands, heavy > line is easier to pull, but won't break until after it's damaged you. > I've thought of, say, 250 kg line with a weak point on the tow > system of 100 kg capacity. That way under tow it will limit > its effect on me but the basic line strength is there when I need > it. > > *100 kg allows for some reserve for impact loading. When paddling > a kayak that's still a _lot_ of force. > > Mike > > > > *************************************************************************** > PaddleWise Paddling Mailing List > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.gasp-seakayak.net/paddlewise/ > *************************************************************************** > > *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Julio MacWilliams wrote: > > That is a good argument in favor of braided polypropilene lines. > They are light and bulky, float, and are easy on the hands. > > The initial 300+lb shock, should be absorbed by a shock cord, not > the paddler nor the boat. [snip] > > Let us see (boring discussion ahead). > > 3 knots = 1.5 meter/second (+or-). > 50lb kayak + 180lb paddler = 230lb = 104Kg equivalent > > Energy = 1/2 * m * v^2 = 0.5 * 104 * 1.5^2 = 117 Joules to dissipate > ^^^^^^^^^^^^^^^^^^^^^^^ > Energy = Force * distance; therefore; Force = Energy / distance > > Hence, > > For 25 cm stretch, (if the rope stretched with constant force, which > does not; at some intant, therefore, there are even higher forces) > > Force = 117 / .25 = 468 Newtons, equivalent to 103lb of shock. > ^^^^^ not too bad. > > For 4 cm stretch (no shock cord) > > Force = 117 / .04 = 2925 Newtons, equivalent to 644lb of shock. > ^^^^^ not me!, thanks :-{ [snip] > > If my physics are too rusty, please let me know ASAP. ;-) Well, the physics is OK in terms of energy transfer, but I think you have assumed a stationary boater (the towee?) attached to another moving at 3 knots (the tower?). Probably not realistic unless the tower gets up to full speed just as the rope gets tight. Another thing which you might consider is that part of the shock transferred to the tower goes into accelerating the tower (in the reverse direction). This diminishes the average force somewhat, but your analysis is not affected much. I suspect that peak forces anywhere near the 103 lbs in the bungie version will do damage to the tower's torso, if the tow rope is attached at his/her midriff. Oww! -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
RE: >Salamander advertises that their tow ropes float, and are highly >visible. > >In a recent workshop, a student made a presentation on towing with >a tow rope that sinks to the bottom, leaving only the storage bag >floating. > >So, here is the question. Is it really an advantage that the length >of a tow rope floats? > >I can see one disadvantage. If the thing is floating all over the >surface, the chances of getting entangled with it are a lot higher. > >opinions? > >- Julio >*************************************************************************** >PaddleWise Paddling Mailing List >Submissions: paddlewise_at_lists.intelenet.net >Subscriptions: paddlewise-request_at_lists.intelenet.net >Website: http://www.gasp-seakayak.net/paddlewise/ >*************************************************************************** ----------------------- Pete Cresswell *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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