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Anchor Rope Size Rules?

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  • Anchor Rope Size Rules?

    Just out of curiosity, are there any charts about what strength of rope is needed for an anchor for various size boats? Mine is a 17' Grumman 5.0 that weighs in with the motor, boat hull and accessories at around 1200 lbs. The anchor is probably around 12 lbs with about three feet of chain on it. Maybe the question is silly but in my area the river can get might strong (Cape Fear River in NC) and I had a motor go out before on me and when I dropped anchor I thought the items in the water were moving fast (crab pot markers) only to find out it was me and the dragging anchor. What a nightmare. So I don't want a rope that is too big and I don't want one that is too small ... and just like the baby bear, I want it just right.


  • #2
    Re: Anchor Rope Size Rules?

    I have a 15,000lb boat, and I have maybe a 5/8" line (maybe a little bigger, came with the boat and i've never put much thought into it) on what I'm guessing is a 16lb dansforth.

    The line is easier to figure out, they all have a working load thats easy to look up, but its amazing how much a little piece of line is able to handle.

    The anchor, the reason you were dragging, is another story. Anchor style and size depends on what you're trying to grip into. Some anchors work better with some bottom materials, others better with other materials. You'll have to make the call on that yourself.
    I like the dansforth, but it fouls easily on a weedy bottom, which usually isn't a problem for me, as Im usually anchored in 30-50ft of water, but occasionally, depending on where I am, it might take me a few tries to get it to grab.

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    • #3
      Re: Anchor Rope Size Rules?

      With your boat, a 1/2", 3 strand twisted anchor line is more than enough. Go with the twisted because it has the stretch that the braided line doesn't have. I would also suggest another 7 or so feet of chain on your rode. 3' really isn't sufficient. The more chain you have lying on the bottom, the better holding power the anchor has. With 3', the movement of the boat can easily lift up that short chain and that's what pulls the anchor loose.
      2001 Carver Voyager 374 'Stick's Competition'

      Something tells me I should be on the water....

      If I answer your upholstery questions, it's only because I've been doing it 20+ years...

      Comment



      • #4
        Re: Anchor Rope Size Rules?

        Like fireman said, 1/2" is plenty for your boat. Realistically, you could get away with 3/8" or even 1/4" ; 1200lbs is a light boat. My beast is 4800lbs dry and empty, and I use 1/2". You won't want to use the 3/8" though, it's tough on your hands. 1/2" is much easier to work with.
        1994 Bayliner Capri 1604 w/94 70 Force (sold)
        1984 SportCraft 222 OFF w/84 Mercruiser 488 & Alpha 1
        1979 Sears Gamefisher 13'6" Aluminum w/1959 Johnson 10HP
        1969 Smokin' Hot Wife

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        • #5
          Re: Anchor Rope Size Rules?

          Here, a quick Google search came up with this from the BoatUS website:

          Rope
          You can attach the boat to the anchor with rope, chain, or a combination of the two. Rope is the overwhelming favorite, usually with a length of chain at the anchor end. Use nylon rope only. Nylon rope is strong, light, easy to handle, and elastic, the latter a most desirable characteristic in an anchor rode. Three-strand offers the dual advantages of greater elasticity and lower cost, but where the anchor line will be fed through a deck pipe for stowage, the added flexibility of braided nylon can make it a better choice.

          Determining how long your anchor rode should be is as simple as multiplying the deepest water you expect to anchor in by 8. As for rope size, the rule of thumb is 1/8" of rope diameter for every 9' of boat length. So if you expect to anchor your 26' boat in 30' of water, you need 240' of 3/8" nylon rope. Unlike oversizing the anchor, oversizing the line is not recommended because that reduces its beneficial elasticity. As a practical matter, however, rope with a diameter smaller than 3/8" is difficult to grip.

          In an emergency the line can be tied to the chain or the anchor using an anchor bend, but for regular use give the end of the line an eye splice around a thimble, and shackle the line to the chain.
          1994 Bayliner Capri 1604 w/94 70 Force (sold)
          1984 SportCraft 222 OFF w/84 Mercruiser 488 & Alpha 1
          1979 Sears Gamefisher 13'6" Aluminum w/1959 Johnson 10HP
          1969 Smokin' Hot Wife

          Comment



          • #6
            Re: Anchor Rope Size Rules?

            also, most people don't put out nearly enough rope.... strong current + 30' deep = at least 150' of rope
            Kevin

            But, where are the reevets?
            1981 Wellcraft V-20 CC Fisherman (FREE BOAT)
            1989 Wellcraft Monte Carlo 28(Build thread here)
            1992 Hotsports Jet'n'Cat Yam 701 WR3 drivetrain "SS George Washington"
            90's Yamaha WRIII and a pair of 95 Kawasaki ZXI-900's
            Fresh clean cheap oil is better then old dirty expensive oil any day
            sigpic

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            • #7
              Re: Anchor Rope Size Rules?

              Originally posted by smokeonthewater View Post
              also, most people don't put out nearly enough rope.... strong current + 30' deep = 150' of rope
              With a strong current, I'd go to as much as 7x, or 210' of rode. My rule of thumb is; calm - 3-5x; strong current or wind - 5-7x; strong current and wind 7 - 10x. Wave height will also play into this as well.
              1994 Bayliner Capri 1604 w/94 70 Force (sold)
              1984 SportCraft 222 OFF w/84 Mercruiser 488 & Alpha 1
              1979 Sears Gamefisher 13'6" Aluminum w/1959 Johnson 10HP
              1969 Smokin' Hot Wife

              Comment



              • #8
                Re: Anchor Rope Size Rules?

                agreed.... edited my post
                Kevin

                But, where are the reevets?
                1981 Wellcraft V-20 CC Fisherman (FREE BOAT)
                1989 Wellcraft Monte Carlo 28(Build thread here)
                1992 Hotsports Jet'n'Cat Yam 701 WR3 drivetrain "SS George Washington"
                90's Yamaha WRIII and a pair of 95 Kawasaki ZXI-900's
                Fresh clean cheap oil is better then old dirty expensive oil any day
                sigpic

                Comment



                • #9
                  Re: Anchor Rope Size Rules?

                  Wow ... I feel better educated and yet a little lacking in the rope length. And I thought 75-100' was enough. So do you use guys use a complete line only on these 150' + runs or do you keep anchor line of different lengths that can attach to each other if need be?

                  Comment



                  • #10
                    Re: Anchor Rope Size Rules?

                    Any point of attachment is a weak point. You can buy a 300' spool of 1/2" rope, complete with a stainless steel thimble, for around $60. Add 10' of SS or galvanized chain (and your anchor) and you're set. Only play out what you need depending on conditions. If you find you need more, it's easiest to just uncleat it and send more overboard.

                    When your pulling all that line up, bumping the boat in to gear a little at a time so that the boat is slightly moving foreward makes it easy to drag in the rode. Even better if you have help.
                    2001 Carver Voyager 374 'Stick's Competition'

                    Something tells me I should be on the water....

                    If I answer your upholstery questions, it's only because I've been doing it 20+ years...

                    Comment



                    • #11
                      Re: Anchor Rope Size Rules?

                      two things about the "rules":

                      I like to have a line that is thicker than necessary b/c it is easier on my hands. The compromise is extra weight and space.

                      The 7:1 ratio is for overnight anchoring a big boat in windy conditions; you seldom if ever need that for casual use. And the more chain, the less rope you need.
                      A man of constant boat tinkering.

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                      • #12
                        Re: Anchor Rope Size Rules?

                        Fireman431, its been so long since I had a boat in the water I almost forgot about running up to the anchor a little to help save the old arm muscles. Thanks for the 7:1 ratio Home Cookin'

                        Comment



                        • #13
                          Re: Anchor Rope Size Rules?

                          also, most people don't put out nearly enough rope.... strong current + 30' deep = at least 150' of rope
                          if i anchor out on lake michigan i will use about 50-60 foot of rope in 10 foot of water if i am anchoring for fireworks in a calm lake i will add maybe 2-3 extra feet with anchor straight down.
                          i also use 1/2 inch line for both my regular anchors on a 23 foot boat, my spare has 5/8 inch rope. the 5/8 is nicer but storing it takes up a lot of room since its bigger line
                          repair shops are for the rich and lazy, want something done right? do it yourself.
                          with knowledge grants perfection

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                          • #14
                            Re: Anchor Rope Size Rules?

                            If you have the room for the storage or use a lot of anchor rode, it's always much easier to use an anchor ball to retrieve your iron.

                            http://www.youtube.com/watch?v=_nxM7VPOC4M
                            2001 Carver Voyager 374 'Stick's Competition'

                            Something tells me I should be on the water....

                            If I answer your upholstery questions, it's only because I've been doing it 20+ years...

                            Comment

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