10mm chain or 8mm chain?

[NPMR]

Still pondering the point as to whether to add chain or not to the existing set up, I looked at weights of different size chain.

Comparing one suppliers product, it seems I can buy 35m of 10mm chain, which will weigh 80.5kg.
Or I can also buy 40m of 8mm chain that will weigh 58.1kg.

Or pro rata.

Leaving the question whether it would be better to have a longer chain but weighing less, or a shorter one weighing more? Or is there an ideal weight, at whatever length?

Our typical anchoring is in relatively shallow waters, behind islands, or in estuaries, or off beaches. 'Overnights' we have enjoyed have been in all of these places. The boat is a 33' Jeanneau sailboat. Lewmar delta anchor.

We once held very well in a big 'blow' off the island of Houat, in Brittany but the chain seemed to be pulled quite taut at the bow causing me to wonder at the amount we had actually lying on the seabed, and I wonder, if we had more weight, the anchor would be even less inclined to move than it did! (Was not a peaceful night, hence my thinking about 'up-speccing' the chain on board, despite feeling in the end, that we had been actually quite secure).

 

[RupertW]

If you look at the krypton thread then all possible answers are there

 

[Yellow Ballad]

50m of 8mm would be my choice...

 

[vyv_cox]

You need to read the interminable threads on catenary to answer some of your questions. In a good blow all the chain will be off the bottom, almost regardless of scope. I trust you also know about snubbers.

Anchoring in Brittany you presumably encounter quite a big range of tides - 10 metres maybe? In that sort of rise and fall you are going to need a good length of chain, assuming you are not going to add rope to it. In my boat of similar size, and in similar tides at one time, I carry 65 metres of 8 mm and sometimes have all of it out.

 

[lw395]

I assume you have a windlass?
Either of those options sounds heavy for a 33ft boat.

 

[Boathook]

I would go for the 8mm and have more of it.

 

[RupertW]

I would go for 6mm if you look at the breaking strains compared to the forces you would encounter. Or 20m of 8mm and a long rope rode

 

[RichardS]

I have 100m of 10mm as I extended the 50m which came with the boat ..... a 40 foot cat. Although a cat has more windage than a monohull, my instinct is that 10mm chain is a bit OTT unless I was determined to anchor out in hurricanes or something. I don't know what the engineering calculations would say but I think that good quality 8mm would be fine for my boat and would save quite a bit of weight.

For yours I would even consider 6mm.

Richard

 

[Neeves]

Your 10mm option is like having a fit healthy, not too overweight, man standing on you bow - would you want such a crew member on your bow as you sail to windward? The alternative seems much better, the 8mm option, as that is the same as having a sylph like young lady on the bow - now which sounds the better option?

But it would be better to have both back in the cockpit and send that rowdy infant to the bow - and I think the 6mm option is the one I would favour - particularly if you can get it in a G40 grade. I have not checked if they supply 6mm G40 - but CMPs Titan chain is good quality.

You have not mentioned a windlass - if you have one and you consider changing link size you need to very quickly check on gypsy prices - they are very expensive. But don't let that deter you moving down in size - 10mm still leaves you with that man standing on the bow as you beat to windward.

If you deploy and retrieve by hand - your back will thanks you for the 6mm chain.

But as Viv mentions - look at snubbers - and use one of nylon, 10mm, of hull length.

So search for threads on snubbers, then look at the current Kryptonite thread - then re-post here with further queries.

Jonathan

 

[LadyInBed]

If your windlass fails, are you strong enough to heave up say 30 mtrs of 10mm from say 10 mtrs (plus anchor)?
I carry 50 mtrs of 8mm plus 30 mtrs of anchorplat.

 

[Trop Cher]

I changed from 10mm to 8mm G40 chain and was then able to increase the length from 35m to 80m, 40ft beneteau.

 

[doug748]

If your windlass fails, are you strong enough to heave up say 30 mtrs of 10mm from say 10 mtrs (plus anchor)?
I carry 50 mtrs of 8mm plus 30 mtrs of anchorplat.

I have similar and it sounds about right for the OP, I also have a length of rope to add to it, come judgement day.

10mm is over the top but the weight of the 8mm serves to hold the boat steady in light conditions and is a handy diameter to haul if you do have to come to grips with it.

 

[doris]

On a 30 footer unless there is a going to be a lots of deep anchoring in rocky places 30m of 8mm plus 30-50 m of warp should be fine.

Going for more might be great for anchoring but all that weight in the bow will be awful! On my last boat, a Dehler 39, the improvement in a chop/swell when we were in 'race' mode ie. just an aluminium fortress and warp in the stem was huge. Even in nice weather taking that load out of the bows made her a much nicer boat to sail. At 8.25 tons weighed empty she wasn't a lightweight flier but the anchor gear in the bows made a big difference. My cruising mode was 30m of 8mm plus 50m of warp.

 

[NPMR]

We currently have, as I said, 20m of 10mm. We also have about 30m of rope rode attached to this. No windlass.

From looking at all your thoughts, I'm minded to shift to 35metres of 8mm and keep the rope rode we have.

My hope is that this will give us not too much extra weight to now (51.1kg for longer 8mm chain compared to 46kg for the shorter 10mm) and also it should be easier to haul in by hand/back. The catenary sounds not too different and there's plenty of chain on the bottom to take the abrasion, with enough rope as well, to allow a lot of 'spring' if it blows up.

 

[peter gibbs]

Even in a blow, the wind load from a 33 ft boat is well within the capacity of 8mm chain in good condition. 40m is a good length, 50m covers all eventualitities, providing the anchor is robust and suited to the terrain. Lightweight alu jobs are much overrated and cannot be relied on when digging in is required. With a good catenary of chain you should be fine.

PWG

 

[RupertW]

Even in a blow, the wind load from a 33 ft boat is well within the capacity of 8mm chain in good condition. 40m is a good length, 50m covers all eventualitities, providing the anchor is robust and suited to the terrain. Lightweight alu jobs are much overrated and cannot be relied on when digging in is required. With a good catenary of chain you should be fine.

PWG

There is no noticeable catenery in a blow nor does an anchor need one if snubbed against snatch loads - hence the discussions about lighter chain

 

[Neeves]

Even in a blow, the wind load from a 33 ft boat is well within the capacity of 8mm chain in good condition. 40m is a good length, 50m covers all eventualitities, providing the anchor is robust and suited to the terrain. Lightweight alu jobs are much overrated and cannot be relied on when digging in is required. With a good catenary of chain you should be fine.



PWG

We have been using aluminium anchors, the same physical size as their steel brothers, for a number of years now (with lightweight chain). The steel anchors are sitting dusty and forlorn in my workshop. Frankly I cannot tell the performance difference.

We only do about 2,000nm miles a year and anchor every night for 2-3 months - so accept we might not have 'time on the water'.

Fortress have sold over 600,000 units, that's 20,000 a year, not a bad record for an anchor you condemn.

Jonathan

 

[vyv_cox]

We have been using aluminium anchors, the same physical size as their steel brothers, for a number of years now (with lightweight chain). The steel anchors are sitting dusty and forlorn in my workshop. Frankly I cannot tell the performance difference.

We only do about 2,000nm miles a year and anchor every night for 2-3 months - so accept we might not have 'time on the water'.

Fortress have sold over 600,000 units, that's 20,000 a year, not a bad record for an anchor you condemn.

Jonathan

Two seasons ago I fork moored in a five-day gale at Andros. The Rocna was on a scope of about 5:1 but due to the difficulty of estimating exactly where it was laid I dropped the Fortress with Anchorplait rode to give a scope of only 3:1 or maybe even less. Despite this the Fortress held perfectly well for three days and was very difficult to recover, having dug itself in so deeply.

A friend had an aluminium Spade anchor. He tells me that he could tell the difference between its holding and that of the steel one that replaced it due to corrosion.

 

[Neeves]

A friend had an aluminium Spade anchor. He tells me that he could tell the difference between its holding and that of the steel one that replaced it due to corrosion.

We have had our alloy Spade for over 10 years now, maybe 12 or 13 years. No sign of corrosion. I do understand it was a serious issue, more than 10 years ago?, and Spade, somehow solved the issue - by isolating the lead from the alloy - resin coated lead insert?? Don't know. We have had our alloy Excel for, maybe 8 years now, has sat on the bow rollers for 2-3 years, day in day out - no sign of any corrosion, yet.

We did have corrosion from the stainless bolts on our Fortress, but not so much they were immovable. I recently replace all the stainless with alloy nuts and bolts. I intend to do the same with the Spade and Excel, both of which use bolts to hold the shank - but I need to get longer ones, they are on order.

Not one of our alloy anchors are showing signs of rust yet.

All anchors are a compromise - you just need to pay attention, to them

Jonathan

 

[vyv_cox]

Sorry, should have said he could NOT tell the difference. He had two replacement anchors, one with resin isolator. Both corroded. There is a pic of the second one on my website.