Question re changing anchor

[Deleted User YDKXO]

Being a raggie I may be barking up the wrong tree ...

Wouldn't the top pin/roller stop the anchor from jumping about when you're bouncing along at 25+knots ?
If so - whatever you do, you need a method to prevent new anchor from jumping about ...

Yup thats certainly one reason its there IMHO. The anchor will be held in place by the lower roller as long as there's tension in the chain plus we do use a wire strop as a safety tie but that wont stop the anchor bouncing up and down if the chain gets loose. I would much prefer to keep the upper roller or at least a pin in that position if I can

 

[Deleted User YDKXO]

While buying a new anchor you could also think about upgrade the stainless D shackle to a larger galvanised steel one.
Stainless ground tackle isnt allowed in many harbour authorities (Ive not seen so many boats broken free but the ones I have seen have all been stainless) and a small stainless shackle is very difficult to keep closed.

The D shackle was the largest I could fit that would go smoothly through the bow roller. Agree its probably preferable to have a galvanised shackle but the breaking strain of the s/s shackle is something like 4t (from memory) so I'm confident its got plenty in hand

 

[mjf]

The D shackle was the largest I could fit that would go smoothly through the bow roller. Agree its probably preferable to have a galvanised shackle but the breaking strain of the s/s shackle is something like 4t (from memory) so I'm confident its got plenty in hand

i fitted a S/S exactly like yours by the looks (allen key torqued up with lock-tight) but never need the swivel - the issue was the galvanized ones fitted previously all rusted and looked horrible

 

[benjenbav]

My boat has a 30kg Bruce anchor which doesn't work well in many Croatian anchorages, particularly those with weedy stony seabeds. It seems to me that the Bruce is not good at cutting through weed to get a bite in the seabed. On my last boat, I had the same problem and I changed the standard fit Bruce anchor for a Delta which worked excellently in the Balearics where I was then. I want to upgrade the 30kg Bruce on my current boat to a Delta too, in the hope that it works as well in Croatia as it did in the Balearics.
I have tried to get a 32kg Delta in Croatia but it seems that the delivery time would be weeks but I have been offered a 40kg Delta from stock. The problem is that the shank of the 40kg Delta is appreciably deeper than the existing shank of the 30kg Bruce, by about 50mm, and I'm concerned about it getting wedged in the existing closed bow roller

Changing or modifying the bow roller is not an option in Croatia because its an original Ferretti part and I dont think they have stainless steel fabrication facilities locally. One option is to remove the top roller of the closed bow roller assembly. What does the panel think about doing this? I guess the top roller is there to ensure the anchor doesn't jump out when it is stored and to feed the chain through when using the anchor.
One thing is for sure. I've lost confidence in the Bruce and since I plan to do a fair bit of overnight anchoring this season so I want an anchor which works!

Mike, this mite just be stating the blimmin obvious but why not get a new bow roller in the UK to fit the new anchor and replace the whole part that pivots.

Following jfm's comments about the point of the delta being too adjacent to the strike plate, I think I am going to do that - for that reason. I hadn't ever really thought about it until I read this thread so thx Deleted User and jfm for the inspiration.

 

[DAKA]

The D shackle was the largest I could fit that would go smoothly through the bow roller. Agree its probably preferable to have a galvanised shackle but the breaking strain of the s/s shackle is something like 4t (from memory) so I'm confident its got plenty in hand

I just realized, its most likely the size of your boat that makes the shackle appear small

Stainless 316 is incredibly strong but it is also very rigid compared to mild steel/galvanised steel.

Anyone who has over tightened a screw/bolt knows that the stainless will easily just snap off.
As such it is incredibly difficult to apply the correct torque to your shackle, tighten it too much and it will be very weak.
dont get it tight enough and it will come undone as there is less elasticity than galvanised steel.
The anchor is very close to your gooseneck which will cause thousands of friction impacts during a night at anchor , imho you have a potential issue that is easily eradicated by upgrading to a galvanised shackle .

The nest time you are at anchor you are going to be laid awake listening to the chain thinking you wish you had put DAKA on ignore , at 0300 you will raise the chain just to check your new Delta is still attached ........






















chink.................................chink




















chink..................................chink




















chink......................chink





Best keep your old spade or an old 135 ah battery handy

 

[jfm]

Stainless 316 is incredibly strong but it is also very rigid compared to mild steel/galvanised steel.

Anyone who has over tightened a screw/bolt knows that the stainless will easily just snap off.
As such it is incredibly difficult to apply the correct torque to your shackle, tighten it too much and it will be very weak.
dont get it tight enough and it will come undone as there is less elasticity than galvanised steel.
The anchor is very close to your gooseneck which will cause thousands of friction impacts during a night at anchor , imho you have a potential issue that is easily eradicated by upgrading to a galvanised shackle .

I don't think that's a fully correct description of the science, and I for one haven't had bolts screws snapping off as i tighten them. The statement "tighten it too much and it will be very weak" just isn't correct. The nut holding your props on is tighterned onto a stainless steel shaft, just for starters, and Mirabella V's mast is held up by tensioned s/s rod rigging

The issues with s/s are (a) oxygen starved crevice corrosion but I don't think that's under discussion here, and (b) the fact is it is more susceptible to fatigue cracking than mild steel.

Susceptibility to fatigue cracking is an entirely different thing from strength. A failure due to fatigue cracking requires inter alia a combination of a large number of stress cycles and a high enough stess amplitude. I agree that during many nights at anchor you could have many thousands of stress cycles, but the stess amplitude is just tiny and so this is not a case where you'd expect a fatigue crack during the life/duty cycle of the set up. Furthermore, the pre loading of the compnents (by "over tightening") actually reduces the stress amplitude, AOTBE, so reduces fatigue failure. That's why you torque up the cylinder head bolts on a reciprocating engine way way more than is needed to seal the gasket.

Incidentally, you can never really tighten a shackle like that because of the flex in the "U" part

I have s/s anchor, shackle, chain, winch, bolts holding winch to deck, the whole nine yards, and i sleep ok. The chink chink is just the gin glasses in the dishwasher Daka

 

[Deleted User YDKXO]

dont get it tight enough and it will come undone as there is less elasticity than galvanised steel.
The anchor is very close to your gooseneck which will cause thousands of friction impacts during a night at anchor , imho you have a potential issue that is easily eradicated by upgrading to a galvanised shackle .

Actually the d shackle I bought had a nyloc thread so I'd be very pissed off if it came undone and in any case, I check the tightness of the shackle and the swivel pins regularly.
I sort of accept your points about stainless steel but you have to ask why reputable companies offer anchors, chains and swivels made out of the stuff if there was known to be an issue with the material. Not that I'm going to be buying a s/s anchor anyway as I was quoted a cool £3400 for the 40kg Delta in s/s compared to £500 in galvanised

 

[longjohnsilver]

Mike I have a 40kg Delta, great anchor, never had any issues with it.

 

[Deleted User YDKXO]

Mike I have a 40kg Delta, great anchor, never had any issues with it.

Stainless I presume!

 

[longjohnsilver]

Stainless - pah! Gold plated of course

 

[DAKA]

I don't think that's a fully correct description of the science, and I for one haven't had bolts screws snapping off as i tighten them. The statement "tighten it too much and it will be very weak" just isn't correct. The nut holding your props on is tighterned onto a stainless steel shaft, just for starters, and Mirabella V's mast is held up by tensioned s/s rod rigging

The issues with s/s are (a) oxygen starved crevice corrosion but I don't think that's under discussion here, and (b) the fact is it is more susceptible to fatigue cracking than mild steel.

Susceptibility to fatigue cracking is an entirely different thing from strength. A failure due to fatigue cracking requires inter alia a combination of a large number of stress cycles and a high enough stess amplitude. I agree that during many nights at anchor you could have many thousands of stress cycles, but the stess amplitude is just tiny and so this is not a case where you'd expect a fatigue crack during the life/duty cycle of the set up. Furthermore, the pre loading of the compnents (by "over tightening") actually reduces the stress amplitude, AOTBE, so reduces fatigue failure. That's why you torque up the cylinder head bolts on a reciprocating engine way way more than is needed to seal the gasket.

Incidentally, you can never really tighten a shackle like that because of the flex in the "U" part

I have s/s anchor, shackle, chain, winch, bolts holding winch to deck, the whole nine yards, and i sleep ok. The chink chink is just the gin glasses in the dishwasher Daka

Its just about irrelevant now as Mike has obviously identified the potential issue and has a nylon locking thread which gets rid of 90% of my concern.

I continue in the interests of completeness for the benefit of anyone else who just relies on a stainless steel shackle.

You have correctly identified several issues however managed to skirt around my prime concern so I shall attempt to elaborate.........

99% of our anchoring is going to be in calm conditions where stainless steel is fine (subject to nylon locking or wired).

Harbour authorities widely do not allow stainless ground tackle, reason being boats are left in more severe / choppy conditions and the stainless does fail.

I view my anchor also as a bit of safety kit, if I wrap a net around my props 1mile off a headland in an afternoon seabreeze F5,6-7 I want to be able to drop my anchor and i expect it to hold me in a race until the lifeboat can tow me to safety.

I expect the chink chink action to loosen the stainless shackle pin .

Thats just what happens to stainless steel shackles.

stainless is too hard to make a lasting hold under continuous vibrations/impacts.

Thats my concern, thats my opinion ( appears shared by many if not most harbour authorities ).

I understand your arguments but we probably arnt going to agree entirely on this (its an anchor thread so no surprise there) so best do as you like on your own boat, and I will do as I like on my boat, you are in the med and perhaps dont have the concern of afternoon sea breezes combined with tidal races anyway so no real risk to you

 

[DAKA]

Just one side issue Mike, if you are upgrading to a delta you can expect a lot more holding power, also upgrading to a larger delta and you can expect a huge amount of extra holding power, you might need to upgrade your windlass or risk clatting around breaking free with your engines which can be embarrassing in a crowded anchorage.

 

[mjf]

chink chink action to loosen the stainless shackle pin

Daka - i'm not sure I like the sound of this; in the past when I have anchored and sometimes its blown much harder that envisaged when I have scuba gear and looked at my anchor and cable I always seem to ride to the cable - the anchor sets as I always give a kick astern once stopped and making no way through the water and the cable piles out behind it. As the boat moves about its the chain that lifts off the ocean floor and moves to and fro with no wt. on the anchor nor its shackle

 

[DAKA]

chink chink action to loosen the stainless shackle pin

Daka - i'm not sure I like the sound of this; in the past when I have anchored and sometimes its blown much harder that envisaged when I have scuba gear and looked at my anchor and cable I always seem to ride to the cable - the anchor sets as I always give a kick astern once stopped and making no way through the water and the cable piles out behind it. As the boat moves about its the chain that lifts off the ocean floor and moves to and fro with no wt. on the anchor nor its shackle

I am happy to accept that most days when we anchor the chain alone would hold us, the anchor isnt really needed at all, which is backed up by your observation.

If anyone considers their anchor is also a bit of safety kit then it also needs to hold in conditions that you wouldnt be safe to dive in where the stainless shackle is more likely to fail, as they do in harbours !

I will try to look out some old photos I have but its a bit irrelevant, you can look up any harbours regulations on ground tackle.

 

[jfm]

Harbour authorities widely do not allow stainless ground tackle, reason being boats are left in more severe / choppy conditions and the stainless does fail.

Yeah but harbour tackle needs to last 10 years. Fatigue cracking is all about number of stress cycles ie duty total period. The total duty of a mobo anchor is nothing like 10 years. 10 weeks more like. If I were anchoring for 10 years then yes I'd set up my kit differently.

 

[MapisM]

Fatigue cracking is all about number of stress cycles ie duty total period.

It''s always interesting to read your engineering evaluations J.
I agree with all what you said re.fatigue, but I'm not sure that's actually the potential problem here.
In fact, I tend to agree with Daka when he says tighten it too much and it will be very weak.
I mean, it's true as you said that the pre loading of the compnents (by "over tightening") actually reduces the stress amplitude, AOTBE, so reduces fatigue failure. But the point is, there's a load level X at which s/steel just breaks. If by over tightening it you get very close to that level, aside from the fatigue effect of the subsequent stresses, the situation is critical because just one of these stresses could reach the X level very easily, because the pre load is just X minus epsilon.
Actually, if you assume that this epsilon is REALLY small, you could be in a situation where you just finish (over)tightening the shackle, and upon the very first slight pull of the chain, it gives up.

 

[DAKA]

Yeah but harbour tackle needs to last 10 years. Fatigue cracking is all about number of stress cycles ie duty total period. The total duty of a mobo anchor is nothing like 10 years. 10 weeks more like. If I were anchoring for 10 years then yes I'd set up my kit differently.

I really dont have an issue with your argument, its fine for you to take a calculated risk which you perceive as been very small even obscure.

Several years ago I posted a report on stainless ground tackle, Ive had a look but cant find it, possibly I posted it on a sailing forum being more relevant as they swing more.
I drafted the report after I witnessed 4 sunk, beached boats total losses for sure.

I took photos including stainless steel ground tackle.
I walked about a mile along the beach to find one owner still in shock as he gazed at his pride and joy.

He claimed the tackle was new a few months ago, the photo I took was of the remnants of stainless steel ground tackle.

Unfortunately the photos were on gludys photo site that he abandoned to sail round the world or I would post them here.

Personally I dont see the difference between using decorative cake ribbon to hold a life jacket on which will work fine most of the time and using a stainless steel shackle to hold your anchor on, both will look very pretty and work most of the time.