Is my chain too thin?

[Eren]

Question.

Obviously the weight of a 12mm chain will make for safer anchoring. However in using a 10mm chain the minimum break load is (give or take from manufacturer) 7 ton
https://jimmygreen.com/lofrans-grade-40/77392-10mm-lofrans-grade-40-calibrated-anchor-chain
Whereas 12mm is give or take 10 ton
https://jimmygreen.com/lofrans-grade-40/77962-12mm-iso-lofrans-grade-40-calibrated-anchor-chain.

Q1 -Given my boat is only 8 ton and equipped this 10mm chain, as are most others in her class of 8- 10 ton, and still capable of swinging on the chain and pulling it taut wouldn't both be too light for you?
Q2- Is the chain stronger than the holding power of your anchor (i.e. apart from weight of the chain helping anchor would the anchor drag before it developed enough holding power to break the chain?)
Q3- Would the windlass / chain lock etc mounting point be able to support loads greater than ~10 ton especially in any sort of snatch event (wave face etc)

All very sensible questions, thanks.

Q1 is the original reason why I raised up this thread.

As for Q2, as per Ultra Anchor specs, 10 or 12 mm chain is in line with the 60 kg anchor that I am using.

Q3: I think the fitment of windlass/chain lock is quite sturdy, without any signs of cracks, etc.

My feeling is that, I am OK with the tackle gear, with chain size being the weak member of the equipment set.

 

[Hurricane]

We had a V4 with 10mm chain and a Delta anchor (40 kg IIRC)
We upgraded to 12mm and a 55kg Rocna.
The V4 windlass is the same as the V5 but with a smaller motor so we upgraded the motor.
There is a gipsy that takes a 12mm chain for the V4/V5. That means that we have 12mm chain (150 metres), effectively a V5 and a 55Kg Rocna.
This was a huge change over the old 10mm and Delta and well worth the upgrade IMO

 

[Plum]

My boat came with 10 mm chain on it. The boat is 73 feet Sunseeker with flybridge, and above 45 tons. She is equipped with Lewmar V5 windlass. I suspect that the chain is too weak for this size and weight. My search on the internet tells the same. The only thing is, on internet it is difficult to find accurate info for specific type of mobos (GRP, with flybridge, etc). I will be glad to hear your comments/information.

It does depend on what grade of chain you have. Grade 30 has a ultimate tensile strength of 5tonnes and at the other extreme Grade 70 has a uts of 11 tonnes (both 10mm) so if you currently have grade 70 and you replace it with grade 30 12mm which has a uts of 7 tonnes you will be worse off. Do you know what grade of chain Sunseeker supplied?

Www.solocoastalsailing.co.uk

 

[MapisM]

Afaik, anything above grade 30 is as rare as hen's teeth, in OEM anchor chains of pleasure boats.
Besides, I would expect that if the first owner of the boat would have specced any upgrade to the OEM setup, he would have also fitted also a 12mm chain, on a 73 footer...
That said, also assuming that Eren has a plain vanilla 5T UTS chain, it takes horrendous conditions to go anywhere near that load, with a 45T boat.
I even suspect that a 5T pull would be enough to destroy the windlass clutch, or possibly rip a stopper off the deck, if fitted...! :ambivalence:

 

[MapisM]

This was a huge change over the old 10mm and Delta and well worth the upgrade IMO

Correct me if I'm wrong M, but didn't you replace the old chain because you wanted a longer one, to start with?
In principle, I agree that I'd rather have 12mm on a boat like yours or larger when upgrading, but did you notice any stress signs on your previous 10mm chain when you replaced it? I'd be surprised if you did.
As I understand, this is what Eren is fearing - nothing to see with having not enough chain or a too light anchor.

 

[Eren]

It does depend on what grade of chain you have. Grade 30 has a ultimate tensile strength of 5tonnes and at the other extreme Grade 70 has a uts of 11 tonnes (both 10mm) so if you currently have grade 70 and you replace it with grade 30 12mm which has a uts of 7 tonnes you will be worse off. Do you know what grade of chain Sunseeker supplied?

Www.solocoastalsailing.co.uk

Very important input! Thanks.

I have no idea about grading of the existing chain, but it is not that costy to get G70 grade chain and close the case.

 

[Eren]

As I understand, this is what Eren is fearing - nothing to see with having not enough chain or a too light anchor.

True. I don't have holding problems. I always leave lots of chain out and Ultra anchor does its job well. This is all about fearing that the chain may break under heavy load. Looks like I can overcome this by getting a G70 grade chain, as per Plum's input, which is fine.

 

[Hurricane]

Correct me if I'm wrong M, but didn't you replace the old chain because you wanted a longer one, to start with?
In principle, I agree that I'd rather have 12mm on a boat like yours or larger when upgrading, but did you notice any stress signs on your previous 10mm chain when you replaced it? I'd be surprised if you did.
As I understand, this is what Eren is fearing - nothing to see with having not enough chain or a too light anchor.

No - it was mainly because I wanted heavier chain.

 

[Hurricane]

True. I don't have holding problems. I always leave lots of chain out and Ultra anchor does its job well. This is all about fearing that the chain may break under heavy load. Looks like I can overcome this by getting a G70 grade chain, as per Plum's input, which is fine.

IMO, the Ultra is good.
But I would change the chain to 12mm
You will definitely feel the difference.
For me, it isn't the breaking risk - it is the extra weight that makes the difference.

 

[Portofino]

IMO, the Ultra is good.
But I would change the chain to 12mm
You will definitely feel the difference.
For me, it isn't the breaking risk - it is the extra weight that makes the difference.

Out of interest H , do you know the weight increase now ,with the new set up from the out of the box OEM set up ?

Have you detected any effect on the boats performance ? Thinking ride in a headsea

Just trying to understand why OEM is lighter — wearing rose tinted specs that Priny / SUNY are not penny pinchers.

I,ll read up on bow weight , moments , by adding kg,s away from the the CoG ,pitching etc in the meantime and report back .

 

[BartW]

IMO, the Ultra is good.
But I would change the chain to 12mm
You will definitely feel the difference.
For me, it isn't the breaking risk - it is the extra weight that makes the difference.

+1

Hi Eren,
if the 10mm chain is long enough (+120m in Adriatic, re enough play for stern to shore anchoring...) there is no real urge to upgrade,
I alway's had 12mm on BA, so can't compare,
but I have "light" chain on our Karnic, and I perfectly understand Hurricane's experience...

 

[MapisM]

Just trying to understand why OEM is lighter — wearing rose tinted specs that Priny / SUNY are not penny pinchers.

I think that has more to see with the wish to declare the highest possible WOT speed, which always has some appeal, on brochures.
IIRC, MYAG mentioned that his 80 footer, which was specced with an OTT ground tackle, was more than one knot slower because of that - not that he cared one bit, mind...

 

[MapisM]

it is not that costy to get G70 grade chain and close the case.

Actually, I believe that the cost difference of higher grade steel ain't trivial - probably higher than putting a 12mm chain of the same grade and replace the gipsy.
Anyway, cost considerations aside, if you really don't feel comfy with your 10mm chain (I would, fwiw), I'd rather replace it with the 12mm than with a higher grade 10mm.
Chain weight is in fact relevant, because AOTBE, when swinging, increases the elasticity and reduces the snatch load.

 

[Portofino]

Hi Guys
Long answer

Anchors and fast planing hulls - 3 points
From the book “ Navel architecture of planing hulls “

1- I think there’s been a bit of barking up the wrong tree guys .
I say this because the problem of suitable weights for planing boat anchors is more one that is largely related to windage than displacement.
Hence 5 or 7 ton breaking strain or whatever fitted to a 45 ton Hatt 73 .
The greatest wind resistance of a boat occurs off full beam.
The heaviest pull on an anchor is a function of mainly topside windage of Sq M of boat profile - not the displacement.

2- chain size
Naval architects use the formula for anchors 10x the pull of the anchors own weight ,a notional break free figure , then add a safety factor of x4
Strength / size / weight beyond this point becomes clumsy to handle - requires unnecessary larger and basically useless gear .
Which I think is why the OEM stuff is what it is .
So in old units ( you may need to convert metric back )
A 50lb anchor ,should hold a 500 lb pull, with a safety factor of 4 = 2000 lbs .

So you need to do the maths based on windage and anchor pull strength of the chain .Not the 45 ton displacement.

3- Adding weight to the bow

The centre of net lift (CL ) - when planing is just behind where the point where the boat lifts out ,ideally as near the centre of gravity as possible to maintain the most stable ride interns of maintaining the ideal angle attack or planing angle .
How ever in reality with variable weights like fuel / water / stores etc this is not always possible .
The further divert the CL and CoG the more likely or the boat to increase its pitching motion when planing through waves .
If you put too much weight on the bow - you can end up with a higher longitudinal moment of inertia , resulting in decreasing the ability to climb over waves , increasing the method of travel to go through rather than over .
This may flatten out the ride in rough seas and be seen to be beneficial , but at the expense of increased wetted area and more drag , slower speed or increased fuel burn if you set your speed for the cruise .
More likely to get wet from spray forming earlier Fwds and higher .
Depending on how fine the bow sections are in front of the centre of lift you may find in bigger seas the boat gets knocked off the plane sooner , ie at say 20 knots as opposed to 18 knots when pressing on in a big head sea , with more weight on the bow from the proposed new heavier gear

How ever if you have also (unwittingly)done the reverse by adding weight on the stern bathing platform say in Hurricanes example then adding weight to the bow could be beneficial in terms of rebalancing the CL , but increased overall wetted area so a slower boat than a stock OEM without the extra weights at each end .
Excess weight aft in a planing boat in a following sea is a cause of broaching so adding or rebalancing weight Fwds .The more plastic underwater that presents to the following waves running downwind the greater the potential yawing forces .

So for me I would leave it as is OEM considering more point 1+2
Is
Point 3 depends and difficulty working out the net effect - so call that a score draw

Conclusion your chain is NOT too thin , just put plenty out.

 

[MapisM]

The heaviest pull on an anchor is a function of mainly topside windage of Sq M of boat profile - not the displacement.

You must be joking.
This principle is utterly BS, and I'd be curious to hear who wrote the book you mention, just to steer clear of anything else he/she might have written.

It can agree that +/- windage translates in +/- swinging, but the swinging per se has very little to see with the pulling force.
What makes all the difference of the world is the snatch load when the boat reaches the extremes of the swinging arc, and that load depends entirely on the boat inertia, i.e. sheer weight.
Just think if instead of a 45T boat you would have an identical maquette made in balsa wood and weighing a few hundreds kg.
It would rebound like a yoyo when it reaches the arc extremes, without even lifting the chain from the seabed - as opposed to a 45T or whatever mass, which wants to keep going together with its own inertia.

Feel free to argue that I'm only relying on plain vanilla common sense rather than naval architecture books if you wish, also because that is exactly what I'm doing now.
But among other occasions, a night spent anchored in Anse de la Garoupe in a F9 westerly blow onboard BA was very enlightening for appreciating exactly what happens in those conditions.

All that said, interestingly I agree with your conclusion, anyway.
Indeed, also that night, when the boat (which is in the 60T ballpark, IIRC) was constantly wrenched every time she reached the extremes of her swinging arc, I don't think the pulling force reached anywhere neat 5T.
I mean, BA is indeed VERY solid, and her bow roller is no exception, but I doubt that it wouldn't have been bent sideways, if it should have withstood 5T pulls either sides, all night long.

 

[Portofino]

You must be joking.
This principle is utterly BS, and I'd be curious to hear who wrote the book you mention, just to steer clear of anything else he/she might have written.

It can agree that +/- windage translates in +/- swinging, but the swinging per se has very little to see with the pulling force.
What makes all the difference of the world is the snatch load when the boat reaches the extremes of the swinging arc, and that load depends entirely on the boat inertia, i.e. sheer weight.
Just think if instead of a 45T boat you would have an identical maquette made in balsa wood and weighing a few hundreds kg.
It would rebound like a yoyo when it reaches the arc extremes, without even lifting the chain from the seabed - as opposed to a 45T or whatever mass, which wants to keep going together with its own inertia.

Feel free to argue that I'm only relying on plain vanilla common sense rather than naval architecture books if you wish, also because that is exactly what I'm doing now.
But among other occasions, a night spent anchored in Anse de la Garoupe in a F9 westerly blow onboard BA was very enlightening for appreciating exactly what happens in those conditions.

All that said, interestingly I agree with your conclusion, anyway.
Indeed, also that night, when the boat (which is in the 60T ballpark, IIRC) was constantly wrenched every time she reached the extremes of her swinging arc, I don't think the pulling force reached anywhere neat 5T.
I mean, BA is indeed VERY solid, and her bow roller is no exception, but I doubt that it wouldn't have been bent sideways, if it should have withstood 5T pulls either sides, all night long.

Lindsay Lord (LL)
Up to pre WW 2 years planing boat s were just built on gut feeling and cos by “dad did that way “
LL was a graduate from MIT in naval architecture in the ealty 30.s - went on post war to be proff of the dept as well as set up a consultancy .
During prohibition 30s he designed for the mafia in the states “ rum runners “ to beat the US coast guard cutters bringing rum in from Cuba to tge southern states .
Applied science from hundreds of hours of tank testing at MIT .
They were un catch able in the big seas of the 100 mile run .
Outbreak of WW 2 in EU he was drafted into the US navy .
Ever resourceful yanks put him to work on motor torpedo boats Rarther than lock him up for his work on “ rum runners “

He was in Peal Harbour when it was attacked btw .
Because of his work he designed a very successful MTB that’s considered to have contributed to saving many lives .
In terms of range a function of hull efficiency * In teens of load carrying ability = torpoedos and anti aircraft guns and fuel , speed in a big sea. Wave crushing ability .#

After the war he published his 1 st edition after returning to the dept at MIT .
It’s the final 1954 edition that’s tge one to find .

 

[BruceK]

baulked at the price!

https://www.amazon.co.uk/Naval-architecture-planing-hulls-Lindsay/dp/B0007DRCCE

 

[Eren]

In my personal case, I think that we reach to the highest tension on the chain when we are moored in Med style, with 90 degrees angle to the side wind. Then the full side profile of the boat, which I guess would be around 100 sqm, is exposed to wind. However in such a case the tension is shared between the chain and mooring line. Of course I take the necessary precautions to avoid such an exposure, but I should make my calculations with such non-ideal conditions.

 

[Portofino]

The bow rise in an anchored swell of say 1-2 M acts on the catenary lifting - let’s say in 10 M with 60 M out
The 10 mm chain does not know if it’s attached to a 45 ton boat or a 17 ton ( mine )
If the wind s not veering to extremis the pull is as said the windage surface area related .
Any veering to swing both hulls to the “ end “ before returning on the arc to the other side ( if I understand you example ^^^ ? ) is actuall damped towards the final position , ie the boat decelerates before what feels like what you call a snatch , all we within the formula in my post .
That’s how a chain of 5/7 tones breaking strain never see that .
The heavier boat EREN s will lift more chain that all and it’s pull will be a bit more than mine , but waaay inside the breaking strain .

Re surface area
Think paprchute or windage on a sail - the bigger sq M the greater the force the wind exherts .
Does not matter of the weight of the parachute or cloth density of the sail .
It’s all surface area related the F

Anchor pull is topside windage mostly with a bit of vertical movement if waves lift the bow and drop it .

I,am not arguing P ,just passing on info .

I mean according to your “ momentum “ theory at max arc and snatch loads , then the breaking strain needs to be greater than the displacement as you infer all the 45 tons +any snatch addition will be applied at max arc ?

But why is the 5 or 7 ton chain not snapping then ?

If the wind is more or less not veering about then it’s the force from the frontal aspect even lower as the calcs are done on worst case full beam on as explained above then x4 for good measure .

* Lurrsen built the German MTB ,s called E boats they were 106 ft long but only 16 ft beam ,with a deep 5 1/2 foot draft , knack all lift they did not understand load and lift .
So they needed 3 x 2500 Hp MB supercharged diesels to achieve a max speed of 42 knots ,
There 17 tons of fuel was gone so fast they were operationally limed to a range of 600 miles
How ever LL calculated and was proved correct with a wider beam from 16 ft to 25 ft , improving the aspect ratio they would have achieved the same speed more/ less for 1/2 the Hp or fuel usage and doubled the range and load ( weapons ) carrying capacity .

How ever tge Japanese MTB we’re actually designed in Italy about 60 ft ,with beams varying from 13 to 16 ft ,flat hulled with 900 Hp twins - not good seaboats - little concept of deadrise pre war , could make 37 knots in flat seas only .
The Japanese fitted heavy anti aircraft guns and there Vs only made 15 knots - no concept of Kg,s and drag .

All the above fruition’s were largely from guess work .

The Brits were a passed down design from WW 1 ,and in every situation basically unmanagable and the all time most uncomfortable and slammed , we developed the double chine from racing boats and the sharp chine angle to lift and reduce drag and go faster in calm water only .We also developed the air step .
In a chop the air was prevented by waves entering the recess because the waves blacked it off from out side ventilation building up enormous amounts of suction at the stern , increasing the wetted area slowing it down .

It’s was so bad a sea boat that they used to attach extra bits of ply on returning to fix the cracked beams and ribs inside
Bit like Vas reinforcement of his plywood hull for stabs - imagine doing that after a trip in a moderate sea .
Thorneycroft had no idea as well .Just passing down “ my dad did it “ and adopting lake racing boats ,like air steps .

Mean while in the states LL applied his maths to the US vs using reasearch from MIT test tank following a scientific approach , delving into lift , suction ( which I understand you are still bemused by P ? ) aspect ratios , changes in moments of inertia , wetted surface area , planing angles , under rough water conditions, adapting the above and ending up with a boat surpassing all others .
Being able to increase speed , increase load carrying ability ,inc range safely in bigger seas .
He was the first to understand positive banked turns .
From tank to 15 ft hull to the real thing
77 ft 44 knot MTB , with the CoG adjusting to carry two torpedo s ahead of the centre of lift and still pull
44 knots
Japanese had no chance in the ensuring Pacific battles
They copied the Italian gov version given to them and by the time they modded it 15 knots in a flat sea !

Because of this LL ,s book is considered the bible for marine architecture of planing hulls - stress planing !

 

[Portofino]

baulked at the price!

https://www.amazon.co.uk/Naval-architecture-planing-hulls-Lindsay/dp/B0007DRCCE

Xmas present but they are sought after - supply demand etc

MapisM - ck out the customer reviews on this “Lord “ guy

Calling his work “BS “is a bit harsh I think .