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Thread: Dock Line Size ...

  1. #1
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    Dock Line Size ...

    It's time to order new dock lines and I can't tell if mine are 1/2" or 5/8". I have the ones that Donzi sent me after I filled out a survey. They are so soft that I can't measure them with a caliper or anything. I think they are 5/8". Which size should I get for a 22C? This site has the best deal on them: http://www.maddogproducts.com/cordage.html

    Pic in post 3. Is it 1/2"?
    Lake St. Clair, Lake Huron, Lake Erie, Lake Oakland

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    5/8 is serious overkill for a 22, and much less friendly for storing. I have 3/8 for the Criterion.
    “Oh right, because you walked into strippers discount warehouse and said ‘Help me showcase my intellect.’” - Archer

    Bill
    Grand Rapids, Michigan
    1985 Donzi Criterion SS
    1967 Donzi 16 Ski Sporter, C16-409, Has a new home!
    38' Carver Aft Cabin
    1968 Sea Ray SRV 180 w/1975 70 hp Evinrude
    10" RIB w/15 hp 1984 Evinrude

  3. #3
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    Quote Originally Posted by Just Say N20 View Post
    5/8 is serious overkill for a 22, and much less friendly for storing. I have 3/8 for the Criterion.
    Does this look like 1/2" line?
    Attached Images Attached Images
    Lake St. Clair, Lake Huron, Lake Erie, Lake Oakland

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    Quote Originally Posted by Just Say N20 View Post
    5/8 is serious overkill for a 22, and much less friendly for storing. I have 3/8 for the Criterion.
    Ditto that. 3/8" is plenty. And smaller line is easier to store. And it's cheaper. And it leaves room on cleats for spring lines and fenders. And it stretches more easily, providing far better cushioning for fittings. Dries much faster too.

    And 3-strand nylon stretches much more than double-braid. And anyone can splice it.

    And the cheap stuff is softer, more pliable, and stretches even more easily. If one looks at the breaking strength, it's MORE THAN PLENTY for any dock lines. 3/8" is 3800 lbs. Hell, that's more than the weight of the boat.

    Dock lines: economy 3/8" 3-strand nylon: http://www.westmarine.com/buy/seafit...05_151_001_004

    Anchor rode: premium 3/8" or even 5/16" 3-strand nylon. http://www.westmarine.com/buy/new-en...ot--P000122606

    And white 3-strand nylon is as classic as classic gets. Whip the ends. Soak it in a fabric softener and water mix every season or two and it stays very pliable.

    The vast majority of boats have lines that are waaaay too thick. It's wrong in nearly every possible engineering and cost aspect. In many ways, it'd actually make sense to go smaller than 3/8" for most Donzis. Only drawbacks are that any smaller can get uncomfortable to handle, and it's harder to spot as anchor rode, especially in the dark.

    Virtually no reason to buy larger diameter rope for boats our size. Buying other specialty lines makes sense, and it can be worth buying double braid in other colors for some of those. Where the different colors and texture make it easy to know quickly what one is looking at.

    And use shock cord for standard fender hangers, not rope. Do it right and you'll never go back.

    Solid braid polypropylene (as in the link earlier in the thread) doesn't stretch hardly at all. Thick solid braid polypropylene is worth avoiding for dock lines, springs and hanging fenders. Wrong in every way. It's a natural reflex to want beefy lines, but instinct is usually backwards on this one. Sailboat rigging is on a never-ending quest for the lowest-stretch possible. On a powerboat, nearly ever use of rope likes lots of stretch.
    "I don't have time to get into it, but he went through a lot." -Pulp Fiction

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    I have 1/2" on the 18' which is PLENTY!

    Stretchy is good.
    1967 Ski Sporter (sold)
    2004 40th Anniversary Edition 18

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    I'll order 1/2" lines. I snapped one like the one in my pic while tied up in an unsheltered slip at Put-in-Bay. Thanks.
    Everyone on OSO has been buying the lines from maddog and have been happy with them. http://www.offshoreonly.com/forums/g...ock-lines.html
    Lake St. Clair, Lake Huron, Lake Erie, Lake Oakland

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    Those are polypropylene, not nylon...


    Frank
    Triple Hatch.
    It's a classic Donzi, not a Donzi Classic.

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    You broke a dock line?! What diameter and material? How long was the run, from your cleat to where the line was made fast on the other end? Where did it give? Where was each end fastened? And thus was the likely breaking motion of the boat due to horizontal pull, or rise/fall that exceeded the actual travel afforded by the line when taut?

    If it broke, it was likely because of shock-loads on rope with very little stretch to it. Breaking strength specs are not measured by shock loading, but rather by gradual loading. Breaking strengths are far lower when under shock loads.

    Shock loads are greatly increased by using rope with low stretch. Stretch is important for reducing loads on the cleat as well as on the line itself. If you've had one break, aside from a defect or prior compromise, or cut/chafe scenario, one would expect the line was heavily shock-loaded, with low-stretch rope, on a very short run, or all of the above. Or worse, and this is an easy thing to do with a Donzi, the line could be set up so that rise/fall from wave action at some point exceeded the slack, such that the weight or lift of the boat itself was on the line, with the needed travel exceeding the slack in the line.

    FWIW, if one broke due to loading, I'd be even more cognizant about choosing a good 3-strand nylon in a suitable size rather than an oversized single-braid polypropylene. The shock loading is painful for the deck hardware and glass as well as the line. The material and the size are both exacerbating this with single braid poly. Picture rubber bands versus chain.

    For people who never really challenge their lines, anything will be fine even if it's the wrong material. Given you broke one, I'd take a closer look at the engineering.

    EDIT: took a look at the OSO thread. No offense intended to any of those guys, but a quick sample suggests most reviewers were interested in the appearance or the price. Yikes, one guy even bought an "anchor line." A FLOATING "anchor line." Seriously. Someone should PM him before that gets cut AND fouls someone's prop.

    http://www.maddogproducts.com/anchor_lines.html

    Anyone who sells floating "anchor lines" is not your friend.

    Not saying people are stupid, not at all. But I am saying they haven't thought it through.

    If yellow is actually important, definitely spring for some snubbers.
    "I don't have time to get into it, but he went through a lot." -Pulp Fiction

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    There hasn't been a single complaint about the mad dog dock lines and some of those guys are using them on large and very expensive boats. I think the fact that they look good and come in all colors is just a bonus. Yes, I snapped what I now know is a 1/2" dock line. Boat was tied in the middle of a slip with two lines on each side. Lake Erie was kicking up. The boat was not in a sheltered slip and was getting rocked pretty hard and one line snapped. 3/8" is definitely not sufficient for Lake Erie! I am ordering a set of the 1/2" yellow dock lines.
    Lake St. Clair, Lake Huron, Lake Erie, Lake Oakland

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    Setting all my rationale and discussion of materials and failure modes aside...

    You are considering line diameter alone to gauge what is sufficient. You snapped a 1/2" line, and your thinking is to replace it with a 1/2" line?
    "I don't have time to get into it, but he went through a lot." -Pulp Fiction

  11. #11
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    Quote Originally Posted by Carl C View Post
    Does this look like 1/2" line?
    Yes.

    I use 5/8" on our Carver, which weighs 23,000 lbs. It has seen some pretty big wave action. I would have thought a cleat would have ripped out of the deck before a 1/2" rope would have snapped on our boats.
    “Oh right, because you walked into strippers discount warehouse and said ‘Help me showcase my intellect.’” - Archer

    Bill
    Grand Rapids, Michigan
    1985 Donzi Criterion SS
    1967 Donzi 16 Ski Sporter, C16-409, Has a new home!
    38' Carver Aft Cabin
    1968 Sea Ray SRV 180 w/1975 70 hp Evinrude
    10" RIB w/15 hp 1984 Evinrude

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    Quote Originally Posted by Just Say N20 View Post
    Yes.

    I use 5/8" on our Carver, which weighs 23,000 lbs. It has seen some pretty big wave action. I would have thought a cleat would have ripped out of the deck before a 1/2" rope would have snapped on our boats.
    Agreed 100% (which is why I was so focused on shock loading, which might account for how the line might have failed less predictably). Also, I didn't see where Carl had said where the break occurred in the line itself. At the cleat on the deck, at the cleat on the pier, splice giving out, at a worn spot in the line, whatever. Nor what the failed line was made of.

    Anything where the line turns a sharp corner (knot, cleating, etc) can significantly weaken it. Another place where stretch should help mitigate the weakness I think. Most people don't know that most knots cut breaking strength about in half of worse. A few specialized knots retain 80-90% of breaking strength (double or triple fisherman is very high on the list). Hence the use of spliced-in eyes.

    One other side note: not sure what kind of "splices" are being used in the Mad Dog single braid polypropylene lines. I'm used to splicing 3-strand (nylon and polypropylene), and used to the proper splices in double-braided nylon. Those single-braid "splices" wrapped in black look really odd to my eye. Could also be a weak link, not sure. Are they sewing the end back onto the line, and covering in black fabric?
    "I don't have time to get into it, but he went through a lot." -Pulp Fiction

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    It snapped right in the middle of the line. These are the lines Donzi sent me when I bought the boat new. It probably failed because they are 10 years old even though it looked perfect. I just ordered 6 new yellow ones. 1/2 inch.
    Lake St. Clair, Lake Huron, Lake Erie, Lake Oakland

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    I like all the information on this thread. I use 3/8" lines on my 22 Classic and feel they are sufficient. They work well with the size of the cleats and I boat in mostly secluded areas.

    My question: What length lines work best for everyone? Normally I only use two lines on my boat. One is 15' long and the other is 20' long. The longer of the two stays attached to my bow eye. The other is used at the stern for tying up at the dock/ramp. Depending on the tide, I feel my bow line could be a little longer for ease of getting back onto the trailer.

    I have a red/white Classic and black dock lines.

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    I have (4) nice black 1/2" lines for the ol' woody 2x15' and 2x25'. I usually only use two but the others are for setting spring lines when needed. The black looks nice with the wood and they coil nicely on the dock when she's at a show.

    Now, my buddy does not like wooden boats. he says they require too much $ in upkeep and repairs. Last July 1st, I had to tow his 2007 26' Cobalt about 10 miles when he had a boat load of people (12) and his engine quit. I had five people in the 1972 18' Greavette and pulled him with a little 4.3 . Fortunately, I had two brand new 1/2" lines that were 25' in length. just linked the eyes together and tied off to his bow eye and my transom eye at a workable distance... the rest is history. I always replace 2 lines every 3-4 years (or sooner if they are fraying).

    Funny thing, even though his boat was repaired (just a faulty switch) he traded it in at Christmas for a brand spankin' new Cobalt . I think he was embarrassed my old wood boat had to pull his luxury Cobalt. Lol. I wonder who spends more on boats... him or me. (it ain't me).
    Sean Conroy,
    1964 Formula Jr. (hull #2) project

    1972 Greavette Sunflash III
    1981 Kavalk Mistral project

    "A man can accomplish anything... as long as he doesn't care who gets the credit."

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