Correct size of anchor chain

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Close hauled

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I have a 37 cat which is currently fitted with 8mm anchor chain. I have to replace both my anchor winch and chain and so have been givivng a bit of thought to what size would be right. ?

I can't find any recommendations on choosing the correct bsize - can anyone point me in the right direction.
 
Pedro.

Before you spend all your folding stuff on 10mm chain, send Snowleopard a PM. He's a smart bloke with loads of catamaran experience and I suspect that he may advise 8mm because of the weight saving and therefore, you could have a longer chain.

EDIT: I should have replied to perdo...
 
Hello, here I am!

First consideration is the size of chain your windlass is capable of using. For up to 1000w windlasses you'll probably get an 8mm gypsy.

I did a lot of research before fitting out my cat (40 ft, 6 tons) and settled on a Lofrans vertical windlass with rope/chain gypsy and a rode of 20m of 8mm chain spliced to 90m of 12mm 3-strand nylon. That is the only size combination acceptable to the gypsy.

I always deploy all the chain even in shallow water, I have a bridle permanently attached to the bows with a short rope tail which I tie to the rope part of the rode with a rolling hitch.

I cut off the splice and re-make it every couple of years to get rid of the worn part.

I'm a little more weight-sensitive than a Prout but you probably have a fair bit less windage than me.

I currently have a 16 kg Delta on the end of that but am considering going to 20kg spade or similar though I have never yet dragged once set.
 
A little addition - I've looked up the breaking strains of my setup: chain 3.2 tonnes, rope 3.0 tonnes. The weakest link is of course the splice. It has to be a back-splice to go through the windlass.
 
[ QUOTE ]
A little addition - I've looked up the breaking strains of my setup: chain 3.2 tonnes, rope 3.0 tonnes. The weakest link is of course the splice. It has to be a back-splice to go through the windlass.

[/ QUOTE ]

less 15% for the splice.

Lofrans 8mm gypsies easily run a 14mm as well.
 
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The RNLI Safety Equipment Advisers will recommend 8mm chain up to 43 feet (13m) yachts

[/ QUOTE ]

They must be very brave sometimes then and/or think 15kts is a hurricane /forums/images/graemlins/smile.gif
 
Exactly how strong is 8mm chain?
Would you rely on one anchor and 8mm chain in a hurricane?
Bit of a silly statement,

"They must be very brave sometimes then and/or think 15kts is a hurricane "

I'd want two or three anchors out in a hurricane, or preferably, be tied up in a bunch of mangroves, either that or be out of the hurricane belt.

I personally think 8mm up to 36', then 10mm up to 45-47 depending on displacement, then 12mm up to 65'. above that dunno. Big probably!
 
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I personally think 8mm up to 36', then 10mm up to 45-47 depending on displacement, then 12mm up to 65'. above that dunno.

[/ QUOTE ] For any size category, displacement matters less, I think, than windage (or whatever the yacht's inherent wind resistance is called). According to Fraysse, the windage on a 40ft cat tends to be around 50% higher than on the same length mono.
 
I'm going to use 10mm chain and 16mm rode. There is some very interesting research in the text 'Oceanography and Seamanship' which points towards using a rope chain combination for giving the best performance. We use a 20kg Spade which is superb and I'm also very pleased with our Fortress.

IMHO I find that anchoring in shallow water - as is normal in a cat - it is good idea to have a scope of 5 or 6:1 of chain down in order to get the anchor to bite.
 
[ QUOTE ]
I'm going to use 10mm chain and 16mm rode. There is some very interesting research in the text 'Oceanography and Seamanship' which points towards using a rope chain combination for giving the best performance. We use a 20kg Spade which is superb and I'm also very pleased with our Fortress.

IMHO I find that anchoring in shallow water - as is normal in a cat - it is good idea to have a scope of 5 or 6:1 of chain down in order to get the anchor to bite.

[/ QUOTE ]

Interesting checking Nicholsons Boat Data Book .... gives 11mm chain and heavy warp combination .... so even heavier than suggestions here !

Personally ... I wouldn't go that heavy - but depends on intended cruising grounds etc.
 
[ QUOTE ]
I'm going to use 10mm chain and 16mm rode. There is some very interesting research in the text 'Oceanography and Seamanship' which points towards using a rope chain combination for giving the best performance. We use a 20kg Spade which is superb and I'm also very pleased with our Fortress.

[/ QUOTE ]

Makes the 68ft Cat I was on yesterday seem very dangerous only on 12mm and a 25kg Spade. Better pop down and tell the 60 something year old single hander that he has it very wrong. He had better stop now and not finish the last few miles of the circumnavigation.

Go 9mm if you don't go 8. Picking 10 is just killing me /forums/images/graemlins/smile.gif Big waste of time and boat performance/safety. We have 50ft multi-story powercats happily on 10mm anchored at the 3 Kings. The 3 Kings is a rock in the middle of no-where with next to no cover.
 
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