1/2 or 5/8 inch dock lines for GB 36

I'm looking to replace the dock and spring lines for a new-to-me GB 36. 1/2 inch is advised for boats up to 36 feet, but I'm inclined to upsize to 5/8 for ease of handling and security, and because 36 feet is the upper end of what is recommended for 1/2 inch. But 5/8 would likely have less stretch and shock absorbtion than the 1/2 inch. For anyone using 5/8 for a GB 36 or similar, any issues and thoughts on whether 1/2 or 5/8 inch lines are preferable? Thanks.

Certainly 5/8.

Moersea said:

Certainly 5/8.

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Thanks! And after 50 years as a sailor, really enjoying the GB 36.

Depends:

I would certainly go heavier for storms and if you're going to be an absentee owner who can't get back to add storm lines.

I would prefer 1/2" in a very protected boat basin for shock absorption. Also depends on tie configuration.

If in a slip with 2 bow lines, 2 crossing stern lines, and 2 long spring lines, I could go either way.

Side tied to a bulkhead or finger pier, it's often difficult to get enough length in a bow line and sometimes a stern line for adequate stretch with heavier lines.

My concern with heavier dock lines is adequate stretch to avoid shock loading of the line, boat cleats and dock hardware.

Ted

5/8

My boat is a little larger than a GB36 (but similar in weight or slightly lighter). I use a mix of 5/8" and 1/2" double braid lines. Most of my lines are 5/8", but I keep a few 1/2" 25 footers around for times where a line will be tied fairly short and I want more stretch. Realistically, if the boat is tied up well and in a decently protected slip, either should be strong enough assuming there are no chafe concerns with how the lines are routed.

Never occurred to me to use 1/2" on a boat larger than 30 feet.

I find I have a better grip with 5/8 and 3/4 lines over 1/2 and 1”.

I would lean towards the 5/8”. But the lower stretch would be a concern. I have 2 dock lines for short line situations where I want stretch and shock load absorbing. I have mooring compensators on them and it gives me stretch and stops the lines from drawing up hard and jerking the boat in windy conditions.

Falcon Safety Mooring Line-Master Snubber/Compensator​

5/8 for all the reasons mentioned.

When needing more stretch you can also use a combo of a thin line and a thick one. Set the lengths so the thin line will only stretch so far before the thick one takes the load. That will prevent the thin line from snapping due to load or fatiguing and failing quickly due to being stretched too far on a regular basis.

rslifkin said:

My boat is a little larger than a GB36 (but similar in weight or slightly lighter). I use a mix of 5/8" and 1/2" double braid lines. Most of my lines are 5/8", but I keep a few 1/2" 25 footers around for times where a line will be tied fairly short and I want more stretch. Realistically, if the boat is tied up well and in a decently protected slip, either should be strong enough assuming there are no chafe concerns with how the lines are routed.

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Thanks for the good advice

Than

Comodave said:

I would lean towards the 5/8”. But the lower stretch would be a concern. I have 2 dock lines for short line situations where I want stretch and shock load absorbing. I have mooring compensators on them and it gives me stretch and stops the lines from drawing up hard and jerking the boat in windy conditions.

Falcon Safety Mooring Line-Master Snubber/Compensator​

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Thanks for the good advice

I’ve been using the snubbers for many years. They do a fantastic job of eliminating shock loads.
It does make the line a little bulky and awkward for stowing, but I find the trade off is worth it.

Bmarler said:

I’ve been using the snubbers for many years. They do a fantastic job of eliminating shock loads.
It does make the line a little bulky and awkward for stowing, but I find the trade off is worth it.

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Agree. I keep waiting for someone to invent a "quick attach" snubber. I only have them on my permanent dock lines, as they are awkward to handle otherwise.

OP: I would also base my line size on what type of cleat you are attaching your line to (weak cleat=equals more shock absorption). I would also base my decision on what line company you purchase from. I just bought some Samson line, which has superior strength and abrasion resistance compared to other line companies, but I'm guessing this strength would make it less shock absorbing. Going down to 1/2 inch would make sense in this case, otherwise I would go with 5/8.

Thanks for the advice. I did use snubbers on my sailboat and they worked well. The only issue,as you mention,is that coiling and stowing them can be more difficult, but I may decide the trade-off is worth it.

I had a cleat mid-ship on my Krogen Manatee that was screwed into the teak caprail. It was always stressed and I had to re-varnish every year due to the forces causing the varnish to lift around the cleat. I wasn't using snubbers at the time.

I am not an expert on docking lines. However, let me add my two cents. Looking at tables of various manufacturers, it seems that tensile strength for 1/2" docking lines ranges from 5000 lbs to 7500 lbs. For 5/8 lines, tensile strength ranges from 9000 lbs to 15000 lbs. The gain in tensile strength is quite significant from just an 1/8" difference.

If I am not mistaken, tensile strength is the force needed to degrade or break a previously unaltered line. It is probably different from working strength i.e. the lower value of maximum strength applied to the line that wouldn't affect its physical properties over an extended period.

My boat is 34' long and weighs 16000 lbs and I use 5/8 lines at a minimum with a tensile strength of +/- 15000 lbs. Your boat, according to her specs, weighs 26000 lbs. If it was me, I would stay away from 1/2" line.

My two cents.

Definitely 5/8. Look around at local marinas. You'll be hard pressed to find a boat that size and weight with 1/2" lines.

If you're worried about shock loads (and you should be) just be sure to use long enough lines. Don't snug up tight to the nearest cleat. For example, run from your outside stern cleat to the dock cleat nearest the stern. Or if there's room, run it back to the next cleat. Obviously spring lines should be as long as practical, too.

5/8”.

Agree with others on 5/8 and also snubbers for any short-ish line run (we use the "swedish" type which are expensive but long lasting).

Another advantage of 5/8 is better grip/feel in the hands, and less tangling.

sjisailor said:

Agree with others on 5/8 and also snubbers for any short-ish line run (we use the "swedish" type which are expensive but long lasting).

Another advantage of 5/8 is better grip/feel in the hands, and less tangling.

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Ok. You got me. What is the “swedish” type?

Ah! This kind:

Unimer Line Snubbers Made In Sweden

They are similar to all the others except that they can (in theory) be added or removed from a line without having to rethread or remove it. In practice I find personally that feature doesn't work very well but also doesn't matter much. I like them for sturdy construction otherwise.

The cleats of the GB 36 are built for 5/8 and 1/2 looks puny on 'em.

1/2" 3 strand when reducing a shock load is needed on a shorter term basis and 5/8" braided when stretch is not needed. Sometimes you may only need 4' of line to reach from the stern cleat to dock. 5/8" braided won't have much give at all. If you are dock where you'll get waked or exposed to chop consider something with some give will help reduce shock loads on the cleats. If you are concerned with 1/2" breaking just add a second line as back up with some slack so line 1 does all the work.

We left our boat in a well-protected marina during a hurricane a few years ago. They required all boats to have four 100' x 1" dock lines. One for each corner and the free end ran back to the boat as spring lines fore and aft. We already had 17" cleats installed everywhere.

I confess that I rarely feel like I have my boat tied up properly in a slip - in surge conditions, being too elastic creates a 'boing-boing' effect where the boat just bounces from one elastic line to another building momentum with each catapult of an elastic line.

Pretty sure 3-strand is more elastic than double braid. I'd go 5/8" at a minimum. As to the "Swedish" snubbers (new term to me too), I used them on 3/4" 3-braid for years on my home slip in San Francisco. They were fine but extremely bulky so they stayed on the dock. As an aside, no way in hell they were removable from the line without a utility knife.

I wish I had better guidance. But I have never been totally sure which direction to go in situations where surge or similar conditions need mitigation - high elastic or low elastic. Loose lines or tight lines. Fenders have been my go-to for uncertainty.

Peter

RedRascal said:

1/2" 3 strand when reducing a shock load is needed on a shorter term basis and 5/8" braided when stretch is not needed. Sometimes you may only need 4' of line to reach from the stern cleat to dock. 5/8" braided won't have much give at all.

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I see your point. I agree that lines need some give. But I chafe a bit (pun intended) at the idea 1/2" is "needed."

I have plenty of 1/2" line on board, but I have never run into a situation where I needed to use it the way you describe. If the cleat was too close, I'd use a different cleat. I'm not saying it can't happen, just that, over the decades, it has never happened to me.

mvweebles said:

I confess that I rarely feel like I have my boat tied up properly in a slip - in surge conditions, being too elastic creates a 'boing-boing' effect where the boat just bounces from one elastic line to another building momentum with each catapult of an elastic line.

Pretty sure 3-strand is more elastic than double braid. I'd go 5/8" at a minimum. As to the "Swedish" snubbers (new term to me too), I used them on 3/4" 3-braid for years on my home slip in San Francisco. They were fine but extremely bulky so they stayed on the dock. As an aside, no way in hell they were removable from the line without a utility knife.

I wish I had better guidance. But I have never been totally sure which direction to go in situations where surge or similar conditions need mitigation - high elastic or low elastic. Loose lines or tight lines. Fenders have been my go-to for uncertainty.

Peter

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Good point on line construction. 3 and 8 strand lines are somewhere around twice as stretchy as double braid.

As far as method of tie-up, what works best depends on the boat and what you have available to tie to. If there's too much vertical drop from the boat cleats to the dock cleats, you have no choice but to leave things a bit looser. If you can get good lead angles, long enough lines to have some stretch, and don't have to accommodate tides (or are on a floating dock) then I typically prefer to tie the boat pretty tightly.

In our home slip, I have things laid out such that I can adjust our general looseness / tightness by adjusting 2 of the 7 lines securing the boat. It's a fixed dock, but in the Great Lakes, so no tide, only a slow change in water level across the season. Most of the time I keep the boat tied fairly tightly, but the lines tend to develop more slack after rain (not sure why double braid does this). In some conditions (mostly surge without much wind) I'll leave the boat a bit looser as it moves more naturally. But if there's much wind, things need to be fairly tight. Otherwise the boat tries to play ping-pong in the slip as you described. Depending on the wind direction this may be a simple forward/aft bouncing, or it can be bouncing around tugging at the lines in every possible direction.

sjisailor said:

Ah! This kind:

Unimer Line Snubbers Made In Sweden

They are similar to all the others except that they can (in theory) be added or removed from a line without having to rethread or remove it. In practice I find personally that feature doesn't work very well but also doesn't matter much. I like them for sturdy construction otherwise.

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I use snubbers like those, and there’s no way you could remove them without rethreading them. In fact, like Peter said, they’re tough to remove in any circumstance.
They work great though, and with double braid line, they provide the stretch I need.