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What Size Dock Lines do I Need ?

4K views 21 replies 17 participants last post by  Barquito 
#1 ·
I don't have a perment slip, so the lines go with the boat...

27' 6800# shoal keel....working lengths I pretty well set with, but diameter and braid has me spooked...

I have 7" cleats on the boat and have been using a mix of 1/2" double braid, 1/2" three strand, and 5/8" 3 strand (stern,bow and midship respectivly) and while they are well weathered, they have for the most part held me secure.

However on one particularly breezy day tied off on the downwind side of a pier in an unprotected part of the bay, the waves really pounded pulled and yanked my boat to the point the lines started breaking...

I usualy tie on with three lines when one broke and then the three strand poped into a two strand...fortunatly I was on deck when it happened and was able to double up all three lines (6 total) until we were able to cut lose and pull away from the pier compleatly...

So I'm in the marke to replace/upgrade my lines...I'm thinking 5/8" all around, maybe 3/4" if that's not overkill and question if I should get 3 strand for strech or double braid for strength..?

What say ye...
 
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#4 ·
Personally I don't use double braid - not enough stretch. I'd use 3-strand.

Given the fact your ropes parted, I think that is a clue that 1/2" was not sufficient, so 5/8 or 3/4. If in doubt, why not overkill? That way you can feel confident.

Also old and frayed ropes are more likely to break. Consider a chafe guard - mine has heavy-duty canvas at the chocks. Avoid tight corners - my port bowline if tied off at the starboard cleat. And if a rope begins to fray - especially a double braid - it is suspect, and can be used as a backup, but not a primary.

My 2 cents... ;-)
 
#19 ·
Personally I don't use double braid - not enough stretch. I'd use 3-strand.
Agreed.

Given the fact your ropes parted, I think that is a clue that 1/2" was not sufficient, so 5/8 or 3/4. If in doubt, why not overkill? That way you can feel confident.
Don't agree. The issue as described is age and wear. Lines are consumable items. They need to be inspected and replaced. My fixed dock lines (5/8" on a 22,000 lb boat) get replaced every three or four years.

I like double braid. I think it is easier to splice, and has a better feel. It also coils easier and doesn't stiffen like three strand does.
Greg - I'm shipping you a box of lines. Splicing an eye in 3-strand takes me about eight minutes. Double braid takes me 20 minutes or more. How do you figure double braid is easier to splice?
 
#5 ·
Newhaul,

I would expect 5/8th all around should be OK for that size boat. I have a heavy 31 and personally I also have two spring lines on each side (total of 10) but I am paranoid. OK a couple of them are 3/4 but no one else I have seen does that around here. Almost all boats your size here have all 1/2 inch with only two lines on each side. (San Pedro CA).

Are you sure that the problem was not chafe that was already there before the wind got strong? Of course thicker lines give you more time to discover chafe but the lines you have should handle wind if they are in good shape.

John
Watermark
 
#6 ·
The lighter lines would be enough however on my islander 24 5200 lb boat I have 3/4 and with the expected 50 kt winds tonight and tomorrow I sleep better. I see it as if replacing spend a little more and sleep better IMO
 
#10 ·
The issue here is the "well weathered". Dock lines don't last for ever and nylon looses a lot of strength over time. For you boat I would go with 1/2. If it's too big the boat won't generate enough force to cause the line to stretch.

For comparison I use

3/8 - 26' powerboat (hauled out for storms)
5/8 - 38' Beneteau
7/8 - 58' powerboat
I agree - 1/2" is all that is needed or they line will not stretch, putting more load on cleats. I have a CS27 of about the same displacement and have always used 1/2" double braid nylon. I also have a small snubber in the bow and stern line. I have had no issues in the 5 years I have had the boat. It does blow here - the wind hit 40 knots in the harbour last night and was measured at 52 knots a few miles away. It is blowing as I type - speed 28 knots with gusts of 38 knots.
 
#11 ·
Thank you Stumble until you mentioned enough force to stretch I would have said big is good bigger is better, I was wrong. However the stretch is what limits damage to the boat. Now I must do more research and I understand mooring with multiple lines that come under stress as the seas become more insistent.
 
#12 ·
Using oversized lines for any purpose on a boat is a bad practice. Oversized lines don't fit the hardware such as cleats, they weigh too much, they don't run freely through blocks, and they don't have the appropriate amount of stretch.

Good charts are available that recommend appropriate sizes for dock lines. There's a good chart in Chapman's Guide to Piloting: Seamanship & Small Boat Handling. The West Adviser also has a good chart. The West Advisor: Dock Lines Don Casey wrote an article for Boat US that includes line size recommendations. Docklines by Don Casey - BoatTECH - BoatUS

I replace my docklines about every 3-4 years, or sooner if one shows signs of chafe. Old lines might look ok, but they become unreliable in a severe storm.
 
#13 ·
I agree - 1/2" is all that is needed or they line will not stretch, putting more load on cleats. I have a CS27 of about the same displacement and have always used 1/2" double braid nylon. I also have a small snubber in the bow and stern line. I have had no issues in the 5 years I have had the boat. It does blow here - the wind hit 40 knots in the harbor last night and was measured at 52 knots a few miles away. It is blowing as I type - speed 28 knots with gusts of 38 knots.
YES, YES. No stretch is bad.

Bigger is not better. 1/2" with LENGTH is better. They always recommend your lines be 1 1/2 times the length of your boat. Obviously, all of your lines probably wouldn't need to be 45' long. I do recommend your spring lines being long with snubbers on your short lines. Don't forget chafe gear.

I replace my docklines about every 3-4 years, or sooner if one shows signs of chafe. Old lines might look ok, but they become unreliable in a severe storm.
Cheap insurance. Looking for new gear 2 hours before a storm is not good. In addition; if tied to a dock, throughly TEST all dock cleats. I have seen numerous docks cleats rip out. It's happened to me and a friend of mines boat almost got sunk because of a bad dock cleat.
 
#18 ·
Take your pick on the line style. I use braided, for the above mentioned reasons. Altho I do have some 3/8" 3 strand made specifically for going thru the local locks. for my 28 LOD 6500 lbs boat, a bit light for stronger winds, but for the going thru locks application, works fine.

OTher wise I believe I have 9/16 might be 1/2" for normal mooring lines. Mine are 15' long, plenty for "MY" slips application. I do have some extra 25' ones along with the 50' ones ready on the boat when at other slips/marinas where a longer rope comes in handy.

marty
 
#20 ·
Chafe protection, particularly where the dockline will go through chocks or rub against rails is the best take away here. Buy some generic lengths, cut them to size and tack them on the lines with a few stitches. Since you'll be at random slips, all your dock lines need to be a bit longer, so you'll be flexible. However, you will probably want to set them up to go on the same cleat each time, as the chafe protection requirement is likely different at each. Just put a small mark on the chafe sleeve, such as A for aft or B for bow, etc.
 
#22 ·
So, one final thought: after replacing crispy lines, and adding some chafe gear, the last consideration may be where to tie off. There may be some locations that are just untenable in certain conditions. I think if I was in a transient slip that was too bumpy, I would ask if there are any other options that have more protection. If not, then it might be safer for the boat to be anchored.
 
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