Mooring bridle size

[pessimist]

Having had a reasonable survey we expect to complete the purchase shortly. We have acquired a swinging mooring. The boat is a 36' cat displacing 5-6 tons and we are somewhat confused by rope size for the bridle for a cat of this size. A very experienced multihuller of my acquaintance used 20mm polyprop (regularly replaced) on his cat of similar displacement but larger size but I think that splicing polyprop of that size is perhaps a challenge too far. Which brings me to 3 strand polyester, but what size? Googling comes up with anything between 12 and 24mm. Has anyone here personal experience of anything similar and what size would you recommend?

 

[jwilson]

I would not let standard polypropylene anywhere near a critical part of mooring gear. I hear the new "polysteel" ropes are good, but I have never used them. When I had a similar weight monohull on a rope bridle I used 2 x 25mm nylon, changed two yearly. Then switched to chain after coming once back to mooring and finding ropes chewed up - think someone got prop round it, even though the nylon sinks.

 

[lw395]

What's the biggest which will work with the cleats and fairleads etc?
(the splice may sit in a fairlead or roller?)
Why use anything smaller?
Maybe it makes sense to use chain for some of it, as the bit near the buoy can't scrape on the bow?
For a similar weight mono, we use 30mm polyester. It looks pretty good after two years but we change it anyway. But the length we need is so short, cost is not an issue.

 

[Praxinoscope]

Certainly would agree with jwilson, no way would I use polyprop'. I always use 'Anchorplait' it has a degrée of elasticity and is nice to handle. For size it depends a lot on how sheltered your mooring is, but I would think 22-25mm anchorplait if if you cleats will take it would do the trick.

 

[alahol2]

On a 32ft cat, but lighter displacement, we used 30mm nylon octoplait. It's fairly easy to hand splice. If doing it again I might look at the polysteel but I never had a problem with nylon.

 

[oldmanofthehills]

Not that heavy a boat. On my 4 ton boat I use twin 22mm anchor plait. Someone spliced it for us. Rope will never snap but can chaff through so put rubber sleeve on or run it over rubber or just check it a lot. I wish chain risers lasted as well.

Nothing wrong with nylon, but avoid ordinary poly

For my 6 ton boat on trot I use two (one either end) 18mm polysteel. I just made a loop with bowline. Much greater strain than swinging as the boat cant weather cock so sits beam on to F7 at times. We use polysteel for our groundlines which last over 40 years or more, but they are not vulnerable to chafe

Nothing magic about splicing it uses less rope and is prettier but wastes an evening, also if you get length too short its unchangeable.

 

[andsarkit]

New rope is usually OK to splice up to about 25mm or larger with octoplait. Depending on the distance from the fairlead/roller to the cleat you might find a small rope will continually stretch and soon fray at the fairlead. I had a 20mm octoplait through a fairlead which nearly parted after 2 weeks when I temporarily removed the chain when the bow roller was being repaired.
If you can't use chain then polysteel sounds like a good option with good UV and abrasion resistance.

 

[Catalina36]

Anchor rode for overnight, rope is fine. Mooring bridle, drive away and still sleep at night for weeks, use chain. See how long it takes to chafe through a piece of 20mm rope with a blunt knife. Half an hour? Now try it with chain.

 

[sarabande]

I moved from octoplait to polysteel last year mainly because polysteel for Ropes Direct floats and has v high UV resistance.

They often have remnant lengths at very good prices. Not difficult to splice but needs 5 tucks instead of 3. to be sure.

Strong, Durable & UV-Resistant Polysteel Rope | Ropes Direct

 

[Rappey]

I have a rope mooring strop. Same as rnsa use (I think) it's around 40mm and 3 strand .
Sorry but don't know what type of rope it is, a proper normal piece of traditional looking rope.
It's used on a light 16ft bowriders. Always in the water.
10 years later and this rope strop still looks to have plenty of life left.
Stretchy ropes are surely not needed as the weight of the moorings riser chain deals with snatching.

 

[Mudisox]

On my 32' cat of 6 tons, I use 10mm chain covered in plastic pipe in the middle, with two ropes to the side cleats of 12mm nylon octoplait, again with plastic piping as chafe protection as it comes over the hard edge.

This keeps the buoy in between the hulls [ avoiding the buoy hitting the hulls] with the maximum load taken on the chain.
Chafe is the problem.
10mm chain is the same as my Anchor chain rode. small stuff spliced into the side ropes enable them to be secured to a separate pick up buoy to the main chain one.

For anchoring I use 12m of 10mm octoplait, middled and rolling hitched on the anchor rode. Any excess chain [ if there is any] is also veered to act as a chum.

 

[pessimist]

Thanks everyone. I like the idea of the largest the cleats will take. I'm also minded to give polysteel a try. I like the idea of a central chain, but with no bow roller (the anchor disappears down a hole in the foredeck) it could be difficult to accommodate.

 

[KREW2]

CCSC which is in Portland Harbour all our boats lie to chain. Some owners put a rope bridle on, but it must be backed up with a suitable size chain bought on board. I have seen several boats come adrift and wrecked. Going to look at them at low water it is always a chaffed through rope bridle that has been the cause of failure.
Two years ago a boats came adrift and did £3000. 00 worth of damage to my boat. His brand new rope bridle didn't last a week in blowy conditions. The boats was 39ft and the backup was a rusty 6 mm chain.