Anchor - Sealine

[vyv_cox]

Hmm, a bit sad that you did not check your gear till it got that bad.

20 Meters of chain out. Why bother. Why do folk scrimp so much on chain. It costs so little to let a bit more out. Are folk hooked on RYA minimum depths

I'm afraid your metallurgy isn't good enough. Stress corrosion is an instantaneous brittle fracture that occurs due to excessive hardness of the metal in corrosive conditions. I check my anchoring equipment on a regular basis but I could have checked it half a second before it broke and it still would have looked OK. Here's a photo of the fracture. The fracture face is bright and clearly instantaneous. No evidence of a progressive fatigue fracture, e.g. partial corrosion, it happened in one hit.

I was in a crowded anchorage in 2.5 metres of water and benign conditions. Some would argue that 20 metres was too much.

 

[MapisM]

That your anemometer is measuring 20 or 30 knots at the top of your flybridge or wherever it is says little about the wind speed on the hull; your own comments about the sea surface seem to support this.

Nope, what I meant is that the sea stays calm just because there's not enough fetch to build up waves.
But in these situations, the wind typically "falls down" immediately from the land to the sea surface: once I had a problem with the outboard of my tender while returning to the boat, and just by sheer luck the wind pushed us near enough to the boat to jump in the water with a line, swim to the boat and attach it to a cleat. There was simply no way to contrast the wind by rowing.
Anyway, whatever, good luck to the OP with the upgrade of his ground tackle.

 

[MapisM]

The fracture face is bright and clearly instantaneous. No evidence of a progressive fatigue fracture, e.g. partial corrosion, it happened in one hit.

Precisely what can be expected after regularly reversing at 2k rpm and insisting for half a minute upon each and every anchorage...
...I'll get my coat!

 

[vyv_cox]

Precisely what can be expected after regularly reversing at 2k rpm and insisting for half a minute upon each and every anchorage...
...I'll get my coat!

I realise that my 27 HP can't compete with the thousands that you people use but for me the load generated by 2000 revs, a little over 50% of my available maximum, equates to that generated by a wind of force 7.

 

[Deleted User YDKXO]

But while snorkeling around in those conditions, I never saw the chain completely lifted off the seabed, as per your assumption.
I did see the chain swinging sideways on the sand, sometimes (albeit rarely) for its whole length, but I can't remember of one single time where I've seen the chain lifted from the bottom in the last 6 to 8 metres.
Therefore, either the wind for some reason always stops blowing while I'm swimming, or the assumptions of your calculations don't match the reality.

Me neither. Since I've been in the Med (about 8 yrs now), I make a point of snorkelling out to look at the anchor most times we anchor and like you, I have never seen the whole chain lift off the seabed. As you say I have seen it swing a little from side to side sometimes. OK we've never anchored in a gale but certainly upto F6
Personally I dont understand how any anchor can be said to have a certain holding power because surely it must depend on the seabed itself. The same anchor will develop a much higher holding force in say, stiff clay, compared to say, soft sand.

 

[craigsmith]

Nope, what I meant is that the sea stays calm just because there's not enough fetch to build up waves.
But in these situations, the wind typically "falls down" immediately from the land to the sea surface: once I had a problem with the outboard of my tender while returning to the boat, and just by sheer luck the wind pushed us near enough to the boat to jump in the water with a line, swim to the boat and attach it to a cleat. There was simply no way to contrast the wind by rowing.
Anyway, whatever, good luck to the OP with the upgrade of his ground tackle.

We can calculate that 50 m of 10 mm chain with a height of 7 m requires ~350 kgf to lift off the seabed (angle above zero), assuming the seabed is horizontal. So, if the chain is not being lifted entirely, you know you're seeing less than that much tension.

With your 53'er, absent obviously any sophisticated idea of windage, we can still estimate that about 20 knots of wind with fetch/surge will create that tension in peaks. In dead flat water with consistent weather (not gusty) I'd guess it would take roughly 30-35 knots.

Not that the point at which the chain lifts is very important; the anchor doesn't care much and it's under the horizontal loading regardless, but it does offer a unique visual reference point that can benchmark almost exactly the tension as above.

 

[Elessar]

Our boat is a Sealine F44 and in common with lots of Sealines has an anchor storage arrangement where the anchor is stored hidden under the bow (sprit).

I think the anchor is light at 10kg (Delta) and would like to upgrade to a heavier version.

It looks as if it isn't possible given the storage arrangement and was wondering if anyone else has managed to upgrade their anchor.

Do others think that the factory fitted 10kg is sufficient? Do Sealine know best?

I am going to upgrade the current 30m of chain to about 60m. If it's an 8mm chain, then maybe go to 10mm, assuming the windlass will work with it okay. I realise a change in the gypsy will probably be required.

Thanks.

This is a problem with the dolphin nosed sealines. It is impossible to fit a larger anchor without major Grp work. A real problem for coded boats that have a minimum weight specified. The deltas have a weighted tip, and you can add some lead to the bottom of the anchor to up the weight of it to make the coding standard. As the anchor was designed by professionals, one presumes adding weight in the "wrong" place will make matters worse, but it does tick the legality box.

And craigsmith doesn't pop up in the mobo forum often but I suggest looking at scuttlebut before listening to a word he says.

 

[PaulGooch]

<snip>

And craigsmith doesn't pop up in the mobo forum often <snip>.

Thank **** for that

 

[asteven221]

Wow just popped back as I had thought this thread had run it's course after a few posts. Thanks everyone for your comments.

So given that we Sealine owners can't add a heavier anchor, what do you think Sealines reasoning was to fit that size of anchor. Do they know something we don't? Do they think it's perfectly adequate? One would like to think a major manufacturer would not on purpose, fit an underspecified safety device like an anchor.

 

[Deleted User YDKXO]

So given that we Sealine owners can't add a heavier anchor, what do you think Sealines reasoning was to fit that size of anchor. Do they know something we don't? Do they think it's perfectly adequate? One would like to think a major manufacturer would not on purpose, fit an underspecified safety device like an anchor.

If you go to the Lewmar website http://www.lewmar.com/products.asp?id=8743&type=3&channel=1 and download the product datasheet for the Delta anchor, you will find an anchor selection guide. For the 10kg Delta the boat loa range is from about 28ft to 43ft so I guess Sealine would say that since the loa of your F44 is near enough 43ft, the 10kg Delta is adequate according to the manufacturer.
However, there's several things to say about that. First, obviously, a mobo carries more windage than a yacht so it would have been more prudent to go for an anchor where 43ft is at the lower end of the range, say the 16kg or 20kg model. Second, the anchor manufacturers are hardly likely to be cautious about their stated loa range for each anchor size otherwise they'd price themselves out of the market; say, for example, one manufacturer says a 43 footer needs his 20kg model and another manufacturer says a 43 footer needs his 15kg model. Which one is the boat builder going to buy? The cheaper lighter one of course. Lewmar used to state in their catalogue that their selection guide was only valid upto a certain wind speed; that qualification seems to have disappeared. The fact is that boat builders cut costs where they can; a heavier anchor means a heavier chain which means a bigger windlass and bow roller and that means a heavier grp lay up in those areas and thicker backing pads. Altogether it would probably cost a boat builder several hundred squids to go up one or two anchor sizes and Sealine decided they wanted to minimise their cost in this area. Is the anchor on your boat undersized? Not according to Lewmar's catalogue (just). Would it have been prudent to specify a larger anchor and chain? No question

 

[vyv_cox]

My boat (sail) is just under 35 ft and was originally supplied (1984) with a 25 lb (= about 10 kg) CQR. Time moved on and most owners realised that this was seriously undersized, so went to the next one up, 35 lb CQR or 16 kg Delta. It would be very unusual to see a 35 ft sail boat nowadays that was supplied with an anchor as light as 10 kg. The realisation that a 44 ft boat has ever been supplied as new with one is astonishing.

 

[Elessar]

My boat (sail) is just under 35 ft and was originally supplied (1984) with a 25 lb (= about 10 kg) CQR. Time moved on and most owners realised that this was seriously undersized, so went to the next one up, 35 lb CQR or 16 kg Delta. It would be very unusual to see a 35 ft sail boat nowadays that was supplied with an anchor as light as 10 kg. The realisation that a 44 ft boat has ever been supplied as new with one is astonishing.

A 44ft, beamy and very tall boat at that. These boats have volumous accommodation and windage to match.

 

[DavidJ]

Just thumbing through a 2002 Sealine brochure (the year I bought my S37) and the following is interesting:

F43 10 Kg Delta anchor
F42/5 (obviously new 'cos its CAD drawings only) 16 Kg Delta

S41 and S43 (Sports) 16 KG Delta

So I think Sealine did see the error of their ways and upgraded

 

[Deleted User YDKXO]

Just thumbing through a 2002 Sealine brochure (the year I bought my S37) and the following is interesting:

F43 10 Kg Delta anchor
F42/5 (obviously new 'cos its CAD drawings only) 16 Kg Delta

S41 and S43 (Sports) 16 KG Delta

So I think Sealine did see the error of their ways and upgraded

If I remember correctly, some charter companies were refusing to accept some Sealine models as charter boats around about that time because of the light anchors fitted which may have bounced them into upgrading their anchors on later models.
To be fair, Sealine are not the only powerboat builder who skimp on anchors. Most power boats in the 40-50ft range would only have 15-20kg anchors fitted as standard and that sort of size of anchor is really only suitable for day anchoring in relatively calm weather. To put some perspective on this, I was looking at a Nordhavn 55 last Saturday and that had a 70kg eek anchor fitted with monster sized chain to match. Thats what I call an anchor!