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Catalina/Capri 25/250 Sailor's Forums

Catalina 250 Specific Forum

Dock Lines

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Steve Raffel
Captain

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262 Posts

Initially Posted - 05/11/2005 : 17:15:53

My C 250 WK is in a very well protected marina. It is in a slip where I have 2 bow lines, 2 spring lines and a stern line. I want to replace some of the older lines. The West Marine box indicates that 3/8" line is good for boats up to 27'. I have always used 1/2" line. Any thoughts?

Steve Raffel
C 250 WK #408

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Bay Tripper
1st Mate

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USA
56 Posts

Response Posted - 05/11/2005 : 20:24:34

I use the 3/8" line on my boat. I keep the boat at a marina in Rock Hall, Maryland. I feel that the 3/8" line fits better on the cleats.

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Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 05/11/2005 : 20:59:32

I have always used Golden Braid regardless of the size. I really like it. It does snag on splinters and things but it is so nice to handle.

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frog0911
Master Marine Consultant

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USA
1349 Posts

Response Posted - 05/12/2005 : 07:51:21

In my home port I use half inch lines, even though its in my back yard. There are times when away the boat will not be visited for a couple of weeks and therein lies the reason for half inch. During the last hurricane season I had 11 half in lines on the boat when under threat of a storm. While crusing I use 3/8 inch, since I will be on or around the boat continuously. I carry 4 docks and two springs all 3/8 on the boat at all times.

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Ben
Master Marine Consultant

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USA
1234 Posts

Response Posted - 05/12/2005 : 14:28:31

Somewhere in Chapmans is a chart that illustrates which diameter dock lines are appropriate for what size boat; the underlying issue being that too small a diameter will be insufficient, and too large a diameter may cause damaging shock forces to the cleats they're tied to.

I loaned my copy of Chapmans out to a fellow sailor, but I could call her and have her look it up for me if you're interested. I think 3/8' is what it says for our size boats, but I'm not 100% positive.

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Bubba
Admiral

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USA
542 Posts

Response Posted - 05/12/2005 : 20:29:04

I didn't find a chart, but Chapman's says, "Typically, a 20- to 40-foot craft will use 1/2-inch-diameter nylon lines, with larger yachts using 5/8- or 3/4-inch lines. Smaller boats can use 3/8-inch nylon." (64th Edition p. 195)

It goes on to say what Ben said about the problem of a lighter boat coming up hard against an oversized line with less elasticity.

I've been using 3/8" because it fits the cleats well. I also figure 1/2" is probably stronger than the cleat.

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Bay Tripper
1st Mate

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USA
56 Posts

Response Posted - 05/13/2005 : 08:27:35

West Marine has a dock lines chart on page 730 for their catalogue. This chart list using 3/8" line for a boat up to 27'.

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Steve Milby
Past Commodore

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USA
5902 Posts

Response Posted - 05/16/2005 : 18:58:14

Most 3/8" nylon dockline has a breaking strength of over 4000 lbs. Don Dodds, in <u>Modern Seamanship</u> pg. 28, says "a recreational boat rarely exerts more than 500 lbs. of static load on a docking line," and it would take a wind of 35-40 kts. to produce that much of a load. He supports these statements with charts and calculations that are beyond the understanding of the mathmatically challenged. He also points out that, at no time is a properly secured boat held by only one line. Depending on the conditions, anywhere from two to four or even five lines are active. His conclusion is that, when you compare the working loads with the breaking strength of the line, "the possibility of line failure becomes ridiculously small." He says docking lines "do not fail" when used with the size and type of boat recommended, because the loads are just too small, even in severe conditions. He says that, if docking lines fail, the culprit will be abrasion, and that providing chafe protection will be of greater value in securing the boat than increasing the size of docklines. He also emphasizes that stretching of the correctly sized docklines reduces static loading at the attachment points.

He offers an example of a 65 foot Swan sailboat weighing 60,000 lbs. The recommended docklines are 1", and four of them have a breaking strength (conservatively) of about 100,000 lbs. Thus, the four recommended lines would be capable of suspending the boat in the air with a safety factor of about 1.5

I used 3/8" nylon docklines on my C25 since 1981, and never had a line break, even when they were showing visible signs of deterioration.

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.