If you are towing an empty boat with paddler inside, you are, really, experiencing only water resistance. That is, on the order 10lbf - SeaKayaker mag typically publishes their drag number for sea kayaks never seen over 20lbf. WW boat is much smaller In other words, if you get snagged, that is only 20lbf jerk. Not pleasant, but not horrible.
If the boat is submerged - whole different ball game.
Force goes F=.5* Cd*A*u^2*rho, here Cd coefficient of drag, A area perpendicular to flow, u - speed of water, rho - density
Cd can be taken as 1, almost the worst case scenario
Let's assume kayak to be L ft long, W ft wide, simplifies to 2.6*L*W*U^2 for expression in lbf, here L and W are in feet, U is in knots, thinking kayak max area is totally perpendicular to flow - aiming for worst case, again.
Typical current, say 4kt, kayak being 6ftx2ft will give you ~ 500lbf, which is guaranteed not to be pleasant.
Making your own The 1/4 line should work just fine.
One addition might be to add a short piece of shock cord (bungie) on one end. This almost eliminated the normal jerkiness of towing someone and that makes a lot of difference on a long tow.
The other thing is the configuration. You want the tow line tied into the front of his kayak – prefereable with a knot that he can release. The other end should be tied to you or just behind your coaming with a quick release. This is especially good if you have a long tow line.
My philosophy is to use the weakest rope that will do the job, preferably 3/8 inch or larger which makes it easier on the hands, easier to tie/untie and makes it less likely to slice into anyone if it manages to attache to a powerboat or PWC.
Paracord is great until it gets wrapped around some body part you’d like to keep and then gets a big yank…
...... the real world I spoke of was a range of lbs. force req. to achieve the breaking point of a new condition 1/4" single braid polypropylene rope . I offered the range between the lowest and the highest , respectively 310 lb. to 775 lb. depending on condition of occurance .
You may insinuate , make an alligation , imply or profess that my motive was something other than what I stated , but that does not make it so .
Further , I clearly stated that I believe it is reasonably possible to exceed the breaking point of the ref. rope if being used as a tow line from kayak to kayak ... you do not have to agree or disagree w/me , you may chose to do either or neither . In any case I will still believe it is a reasonable possibilty unless it can be shown otherwise .
Further , your scope of discussion is speculative as to the scenarios and circunstances as you have presented them , as you have experienced them . I have not disagreed nor agreed w/you about any of that .
As well , mine are speculative as to the scenarios and conditions as I have presented them .
Regardless of any of that , the specs. for the rope are aprox. what I have stated .
Under the scenario I offered , can the rope experience a 310 lb. force (pull , stress , resistence , whatever term is appropriate) , or not ??
I simply envision the gross weight (mass) of the towing vessel x whatever increase is apropriate for the forward momentum (inertia ??) , being applied to the rope in lbs. force should the towed vessel get abruptly stopped .
Also , polypropylene rope has very little stretch characteristic , and does not absorb shock loads very well at all . It is a notoriously brittle rope I beleive .
Ooops I suppose maybe I replied too quickly. While I am still confident that you won’t break 1/4" rope of any kind while towing, to be on the safe side, I suppose we should recommend 1" Plasma 12. It is also torque free, so that solves a problem you never would have known you had! Also, with the breaking strength, it ought to avoid having to do any math, as it will hold the combined weight of your kayak, your son’s, your truck, the dock, and a camper trailer.
You say "You may insinuate , make an alligation , imply or profess that my motive was something other than what I stated , but that does not make it so."
What allegation did I make? What did I insinuate? Everything I said was stated very directly, not in the way you describe here.
What did I say about your motives? I thought the only thing I talked about was how much force can be generated by a moving boat, or to get a boat into motion.
I said one thing which was based on experience: I said the tension in the tow line, even during the worst jerks in choppy condition, is very minor. It's very easy to tolerate and is nothing like the 300+ pounds you think is possible. It's the sort of thing that would allow you to easily hold the rope in one hand and not lose your grip. I also gave some easy-to-understand examples to shed some light on why that is so. Where you read all that other stuff is beyond me.
"and you are talking as if one boat and it's load is getting a high speed running start or something"
"if there ever were such an enormous jerk on the line as you describe"
understand that I have not ranked the lbs. breaking force for the 1/4" poly rope as great , greater , or less/lesser ... only stated what they are , you are the one who has ranked them
oh, here's one more way of explaining it since you do alot of fishing"
and the likes of such with you defending (for whatever reasons you felt nessasary) your premise by speaking of how you have towed boats in extreme conditions and do not feel by your experience such stresses could possibly result ... perhaps not in the situations you have spoken of , but then again , if you consider the simple scenario I presented with me towing you down a river and your boat gets abruptly stopped maybe that situation could apply the req. lbs. force to break the rope if attached boat to boat , or jerk someone out of the boat if attached to a person , or give you bruises etc. ... I think it could but you may not .
Regardless of that , it is your implication , insinuation etc. that I feel the min. req. lbs. force of 310 lbs. to break the 1/4" poly rope is a great force , an enormous force , etc. ... actually I do not feel that the 310 lbs. is very much at all and could easily be achieved ... from my perspective you seem to want to animate that 310 lbs. as great , enormous ,etc. .
A few suggestions -Spend the money for a good waist-mounted tow belt with a quick-release buckle. It makes a huge difference in comfort & safety if you’re towing for a longer distance.
-A long enough line (30-45 feet) will accomodate sudden changes in speed/force.
-Good tow belts have the beginning 10 feet of the line coiled around a strong thick bungee about a foot long, which further cushions shock.
-Always carry something to cut the line with in case of entanglement. The trend is away from pointy river knives, toward rescue hooks (like for cutting seatbelts) or EMT shears, which will cut line but not appendages.
-Don’t use thin line. Think about what would happen to an entangled hand or neck. Good towbelts have 1/4" to 3/8" line. Bright-colored floating line is an additional safety feature.
-If possible get some training on safe towing with a kayak. There’s more to it than meets the eye. If you can’t get it in person, there are some good videos on YouTube, such as this one by Fergus Coffey of Zoar Outdoor: http://www.youtube.com/watch?v=iOH19kjb4Xc
......but I thought those statements were an accurate interpretation of how much force you think might be generated in a tow rope pulling a kayak. I don't think anything I said can be called an insinuation or allegation if it is said in a clear-and-direct way that is even in agreement with your final statement above.
I'm nearly done, but as long as you make this a major point, I DO think a 300-pound force is enormous in the context of lightweight boats and paddle power. I can't imagine a situation where I couldn't pull a kayak through the water by holding the tow rope with one hand. I can NOT resist a 300-pound horizontal pull on a rope, even with all my strength and especially not when sitting in a boat (I'd tip over in the blink of an eye), and certainly not with a light one-handed grip, but I am certain a light, one-handed grip is all it would ever take to keep a kayak in tow, no matter what the waves might do. After all, I've done it. I still think you need to try it yourself. Lining a gear-laden canoe upstream through swift rapids requires a rather light, one-handed pull as well, even when the boat gets sideways to the current (and yes, in THAT case you are holding one rope in each hand).
Originally I thought it was enough to say I've pulled kayaks in rough waves and never felt more than a light tension in the rope, but since that isn't a good enough example, before I quit, I'll tell you two other true stories.
#1. A couple summers ago, a group of us needed to take a guy with a cut hand upriver a few miles to the hospital. We were partway into the trip and met two game wardens, whom we asked to tow us. They towed our tandem canoe with three people onboard at at a speed many times faster than any tandem canoe could ever go under paddle power, yet one warden in the power boat simply held the tow rope out to the side with one hand. After 20 minutes or so he was getting tired of resisting the rope tension and switched hands, but his one-handed grip and awkward arm position made it look like the tension wasn't more than 35 pounds or so.
#2 Years ago when my dad and I were fishing, the anchor got stuck on the bottom, and we couldn't pull it up by any normal means. Finally my dad decided to try pulling it loose with the outboard motor. The anchor line was 1/4-inch nylon, and the motor was 5 horsepower. He pulled and pulled, eventually reving the motor all the way to full throttle. The jet of water shooting out behind the boat was pretty huge, and it was terribly difficult to keep the boat lined up for a proper pull since the rope was attached to one side of the front, rather than the back, and the motor pushing from the rear tended to make the boat want to veer suddenly and let the rope guide it into a curving path instead of remaining dead in the water and pulling. So every time the boat tried to veer off and lessen the rope tension, my dad would counter-steer the motor creating a jolt that would re-tighten the rope and make the old wood-canvas boat creak, but the rope never broke. I don't think it was remotely close to breaking, but of course I don't know for sure. What I do know (okay, I'll concede that you won't believe I actually "know" this - you've already told me so), is that you can't create that kind of tension in a rope that connects two paddle-powered kayaks.
My example of a possible shock load being applied to the rope is my reasoning for belief that the min. breaking lb. force could be reached or exceeded .
You have spoken of the forced required to achieve an acceleration of a mass (weight) . I have spoken of the forces attained at an abrupt decceleration of a mass , such as an abrupt stop of the towed vessel could create .
In the story where the Warden held the rope in his hand , my guess is did so for safty purposes knowing that if he had attached the rope to boat directly it was possible for the rope to break or cause a capsize or injury should you all being towed have gotten snagged on something . The highest possible loading that could of been placed on the rope in his hand was only whatever lbs. force he could hold on to , not the weight of his gross boat load as might have been applied in the snag scenario .
In the story of you and your Dad the lb. force applied was most likely a uniform graduation of lbs. force and not a shock load . If your Dad would have allowed a running slack and then accelerated until the anchor rode stretched tight , it may have snapped the line as it realized the full weight of the pulling vessel combined with it's forward momentum . My guess is he did not want to break the line or have something else break instead and therefore applied a gradual uniform stress to the anchor rode as opposed to jerking it out .
I agree that you or I could not resist a 300 lb. sudden force applied to a rope in our hand , perhaps a gradual force applied to 300 lbs. is possible though certainly not req. to accelerate a kayak on the water ... but I do believe that a towing boat could resist a 300 lb. (or greater) force if the same rope attached directly from kayak to kayak in motion such as being towed , were to experience the towed vessel suddenly and abruptly being halted such as in a snag or hang scenario as I suggested prior .
Lots of interesting "math" on this thread. The posters who say you will never see more than around a 20 pound load are correct. When one kayaker is towing another, the actual mass of the load is NOT a significant factor. You will NEVER get even close to a 100 pound load when towing any kayak. If you did with a typical tow belt around your waist, it would literally kill you, your internal organs would be crushed. Some of you math whizzes are thinking about this all wrong. The towed boat’s weight is not a significant factor. While you do need a 200 pound force to LIFT UP a 200 pound kayak, you do not need a 200 pound force to tow a 200 pound kayak. More like a 2 pound force. If you can’t simply “see” the difference in your head, all the math skills in the world will not help.
Let's just agree that we are talking about dry boat - on top of water, and there are no breaking waves involved.
The OP was not dealing with any sea states, so this observation is valid.
In WW, submerged boat, or SK, similar, breakers or anything involving sudden release of energy, most of the bets are off. Make sure you have, at least some, idea what you are facing. Being jerked by a dumper while towing out is NOT fun.
Just some final remarks I thought I was done, but it’s raining and that changes my schedule at the moment, so I’ll write a little more.
“You have spoken of the forced required to achieve an acceleration of a mass (weight) . I have spoken of the forces attained at an abrupt decceleration of a mass , such as an abrupt stop of the towed vessel could create.” There is no difference between the two situation. In physics, there is no such thing as deceleration, only acceleration. Deceleration is a lay term that describes the direction of acceleration. The force applied to the object is the same in either case. Even driving a car at constant speed around a curve requires an input of force and is defined as acceleration and the force is defined the same was as for all forms of acceleration.
“In the story where the Warden held the rope in his hand , my guess is did so for safty purposes knowing that if he had attached the rope to boat directly it was possible for the rope to break or cause a capsize or injury should you all being towed have gotten snagged on something . The highest possible loading that could of been placed on the rope in his hand was only whatever lbs. force he could hold on to , not the weight of his gross boat load as might have been applied in the snag scenario.” He held the rope in case our boat got out of control. Here again, if you had ever towed a canoe behind a motor boat, you would know that the real danger is the boat taking off at a cockeyed direction and suddenly flipping and swamping. It’s not the rope you are worrying about in that situation, as the rope has plenty of strength to destroy the canoe in that scenario. just as sometimes happens when freeing a pinned boat in swift current but typing the rope to a convenient place instead of a location that causes the boat to lift up before being pulled in. We actually told the warden this quick-release option was necessary because keeping the canoe pointed the right way at that speed was a pretty sketchy and nerve-racking affair. Had the boat turned sideways and and flipped but not been allowed to release, it would have been seriously damaged. The correct way to tow a canoe at high speed is with a harness (which puts the anchor point right on the keel line, a few feet behind the bow), just like what whitewater paddlers used in the old days for lining through rapids. That would have been perfectly safe, and no quick-release would have been needed.
“In the story of you and your Dad the lb. force applied was most likely a uniform graduation of lbs. force and not a shock load . If your Dad would have allowed a running slack and then accelerated until the anchor rode stretched tight , it may have snapped the line as it realized the full weight of the pulling vessel combined with it’s forward momentum . My guess is he did not want to break the line or have something else break instead and therefore applied a gradual uniform stress to the anchor rode as opposed to jerking it out.” When you read it again you will see that there were some pretty strong jerks during those crazy corrections to the steering that were needed. You are right that a really strong jerk on the line would have broken something on the boat. The rope was wrapped over the gunwale a few feet behind the bow, putting a sideways force on that gunwale, and that’s what was creaking. But how could you duplicate such forces when towing one kayak with another? That was a much stronger force than any towing situation, even one motorboat towing another. With two kayaks, even if the towed boat stopped dead, the pulling boat is so light, the speed so small, the rope has a bit if give, and it would be no big deal. No worse than bumping into a log when paddling alone.
“I agree that you or I could not resist a 300 lb. sudden force applied to a rope in our hand , perhaps a gradual force applied to 300 lbs. is possible though certainly not req. to accelerate a kayak on the water … but I do believe that a towing boat could resist a 300 lb. (or greater) force if the same rope attached directly from kayak to kayak in motion such as being towed , were to experience the towed vessel suddenly and abruptly being halted such as in a snag or hang scenario as I suggested prior.” You just need to do this yourself a few times to see what (to you) will be an amazingly small amount of tension in the rope, even during the “worst” jerks. Maybe reply to the other posters in this thread who are saying the rope tension will never exceed 20 pounds and see if they can explain it better than I can. Those are people who have towed boats too, it seems.
suriam , I agree as well … … no contest as to the amount of energy (lbs. force ??) required to pull or get a boat into motion on the water (overcome it’s inertia on water) , kayak or 4 ton vessel … never was , nor needed to be , it’s always been more than obvious to me that the required force is very minimal , dah . (here’s a capitol L to wear on the foreheads of those who think it nessasary to argue the point w/me)
I offered examples of the breaking point of 1/4" poly rope (lbs. weight ??) . I also suggested the 1/4" poly line could break under a shock load situation if connected directly from boat to boat .
As a side note I haven’t noticed anyone else expressing any understanding of how a line’s breaking point is deternined . Seems one might want to know that for various reasons .
I offered a scenario of the towed vessel becoming stopped abruptly at a speed of 3 mph. , and suggested that the tow boat’s weight (plus the potential energy of that weight at 3 mph velocity) , could be transfered to the tow line and result in exceeding the 1/4" poly ropes breaking point at a knot or attach point .
I think it’s a reasonable thought the possibilty exist that the towed vessel could become snagged (or severly interfered with) abruptly … but it seems a number of responders can only grasp the minimal force of what it takes to overcome the inertia of the towed vessel to get it moving on the water , and are not capable of (or ingnorantly refusing to) acknowledge that such a snag could happen and the resultant shock forces may be capable of breaking the line .
Because I do not feel capable of formulating the proper physics equation to express the amount of energy that could be transfered to the tow line in that snag scenario situation , I had ask you if you could do it … I still would like to know how much energy (preferably in relationship to the way lbs. are used to determine a ropes service ability) , could be transfered to the 1/4" poly line
Safety From the safety side of things you want to ocnsider the worst case scenario which is that some powerboater thinks it would be cool to zip in between two kayaks and doesn’t see the tow line.
If I’m in either kayak and see this about to play out, I want that quick release or a knot that can be released. Second, I want to know that the rope is weak enough that it will break well before it jerks my kayak apart or does bodily damage if it is on a tow belt.
If you have static line rated at 4000 lbs tied into your boat the jerk is going to be bad and the rope will not fail before parts of you or your boat start coming apart. A stretchly, weak line diminishes the jerk and breaks more quickly.
And imagine if you have that line get wrapped around your wrist when the jerk occurs. Would you rather have a weak 3/8 inch rope or smaller diameter and much stronger paracord? The small, strong rope creates a lof of pressure on a small area and tends to slice into flechy things when enough force is appled.
Do all the math you like, but use medium to large, weak rope that floats and have a quick release on each end – even if it’s just a simple knot that unties quickly.
I seriously doubt there is any commercial rope 1/4 inch or larger that is too weak for towing.
if a boat w/a gross weight of 250 lbs. … is traveling at 3 mph. pulling a vessel behind it , and the vessel behind gets stopped abruptly … how much energy will be transfered to the tow line at the moment the line becomes fully stressed , or shock loaded (in lbs. please) ??
I think the tow line will realize quite a bit more stress in the shock load situation than what’s required to simply get the towed vessel moving on the water (gradually overcome it’s inertia ??) .
If I understood you correctly gbg , you think the two forces would be equal .
I’ve towed small vessels as well as larger vessels before gbg , and I’ve even seen a good quality tow line break once in the tow operation . The towed vessel simply bounced on a wave , the line became momentarily slacked just a little , and at the point of retightening , snap it went . The towed vessel only weighed about a 1000 lbs. , the towing vessel weighed about 3000 lbs. , the line’s breaking point was rated at more than weight of the two boats combined .
No, at no point have I said that a quick snap applied by the rope is the same as gradually changing the speed of a boat by pulling on the rope. Please read more carefully and stop saying that. All I have said is that you won't experience such a violent, quick snap as that when towing someone. You need to get real. Next time you are out, tie 40 or 50 feet of rope to your canoe and tie the other end to the another canoe and paddle away slowly (remember, when towing another boat you'll be doing good if you can reach 3 mph. More likely you'll go 2 mph). I predict that you won't observe the kind of force you imagine. Try it at 5 mph if you want and you still won't see anything remotely violent. Try it when tied to a tree on shore and paddle 3 mph and still no big deal, but try it at 5 mph and maybe then you'll break something, but most likely it'll be the thwart on your canoe. It sure won't be the rope. Let us know what you find.
I say you should try this yourself, because I already know that you CAN get a running start against the tow line while the other boat is stationary. It happens a lot, and nothing violent happens as a result. There are too many options for "give" in the system (a couple inches of stretch in the rope, boat that pivots slightly from an off-center pull, boat rolls slightly due to the attachment point being higher than the center of gravity, and only ONE boat needs to act as a cushion to affect both). And don't come back and say it makes a difference which boat initiates the shock.
Oh, yeah, and probably the biggest cushioning effect is due to the fact that the heaviest thing in the boat is a live person, not a solid, inanimate object that is structurally connected to the boat. If the boat instantly stops, the person's upper body will simply rock forward a few inches, and that's all it takes to eliminate nearly all of the shock that would be due to his proportion of the total weight. After all, if a person were to jump off a two-foot-high step they'd land at a higher speed than a boat will travel, and if they landed with locked knees and a straight back, they'd do serious harm to their body. Instead, just a few inches of "give" in the knees is all it takes to make stopping at the bottom of that two-foot drop require a negligible force and no severe strain to the body results. The cargo in the boat isn't structurally part of the boat either. Even if tied in, it would shift a tiny bit if the boat somehow stopped instantaneously. Would you expect the ropes that lash your gear packs to the floor to break too?
If you don't try this for yourself, take it up with any of the other people here who are saying that 20 pounds of tension is all you will ever experience, and mostly much less. Maybe they will have another way of explaining it.