BBB vs High-Test Chain

[Adelie]

Stretch is an indicator that a previous storm has loaded the chain to near its limit. If during a periodic inspection of the chain you note that the links have been stretched you know it is time for replacement or at least switching it to use as a backup. During a storm you will not have the opportunity to check if the chain is stretching, nor any likelyhood that you could do anything about it other than setting another anchor to lighten the load.

[kiltym]

Originally Posted by craigsmith

If you look at this C-link testing here, 8 mm G40 is tested to a break of 4,900 kgf.

Unfortunately they don't tell us the brand of the chain they use, so it doesn't necessarily mean its the same as the Maggi G40.

Originally Posted by craigsmith

The Maggi figures usually exceed the standard, although in the case of 8 mm EN-818, the 4030 kgf figure is the same for both. In any case my suggestion is that Maggi's figures are conservative.

The catalog I have states the following for their 8mm EN 818-3 chain:

Maggi BLL 40.2 kN which is 4100kg or 9038#.

Originally Posted by craigsmith

The other factor is that the ACCO chain tends to be a 430 grade, not actually 400. Together, that explains the discrepancy.

According to this page:

Chain Grading

Gr43 and Gr40 are the same, so something still seems off to me, call me crazy.

Still a big enough discrepancy between the Acco 5/16HT at 11600# and the Maggi 8mm at 9000# that makes me wonder. Two G40 chains of the same size should be equal, or, one is simply a stronger chain.....?

[malbert73]

I was re-reading this thread.

With regards to BBB, since it is heavier per foot that G4, can't you anchor with less rod length?
My reasoning is that all nylon rode would be lightest, but would need the highest scope to set.
G4 is lighter, so in general you need more length for same conditions as BBB, right?

[Adelie]

The second you get to wind strengths high enough to eliminate the catenary, it doesn't matter if you have BBB or G4, the only important thing anymore is scope. The difference in windspeed BBB and G4 to eliminate all sag will be on the order of 5kt or so. The difference in length to make them loose all sag at the same time would be like 10' or so. The difference is not worth quibling about.

[GMac]

Agree the difference is that small you won't be able to notice it nor will the anchor.

Originally Posted by craigsmith

Of course not, G4 is approximately 33% stronger than G3 as the grade numbers would imply.

G30 plus 25% = G40, in round figures. In actual load numbers it looks like this -
A G30 8mm busts at 3200kg, add 25% to that, being 800kg, and that adds up to 4000kg, which coincidently is the same number as a G40 8mm.

No idea where the 33% comes from but it is wrong.

Note those are metric 8mm not imperial 5/16" numbers, but the same applies. Grades are universal even if sizings or the way chains are measured aren't. There is also a small wobble in the numbers due to how they actually report their products loads. Some use the bestest ever number they see in testing, some use the 'average bestest', some use the minimum bestest and some just use numbers from a good chain maker they find on the interweb. Most reputable outfits tend to use the 2nd to later, china tends to use the later later.

Due to the many differences between the way the US works their numbers and it still being imperial, it does make it hard to make a direct comparison at times to a EU made chain for example. Just watch for that as there are a few traps for the average boater to fall into if they aren't careful, especially when talking sizing.

As a quick and funny aside. I was talking to a very long standing (150 years they have been making chain) Chinese manufacturer a couple of weeks ago about some huge special stuff for a special project. While chatting I mentioned the quality issue many see with china made chain. The dude said 'Oh yeah we totally agree. Many manufacturers here are that dodgy even the chinese people don't trust the numbers and that's reflecting badly on our business, they are buying chain in from offshore'. I did have to laugh at that. Note the chinese dudes words have been westernised for easier consumption and understanding of

[Play Actor]

A really interesting thread, with some good information. I have two comments.

First, it's a physical impossibility to pull so hard that you eliminate the catenary curve, unless you are in a zero gravity environment. Don't trust your instincts or your eye on that. Look it up.

Second, based on thousands of nights at anchor and most of it on various types of chain rode, I think too many people undersize their chain by going to stronger, lighter chain. Strength of the chain is rarely the issue in anchoring. The weight of the chain, however, does nave a serious impact on holding, especially in everyday conditions, regardless of the type of anchor. Of course, nobody wants that weight in the bow, but nobody wants to drag, either. It's one more trade off. The difference in weight between bbb and standard chain of the same size isn't too significant, but the difference in weight (and holding) between 5/16" HT and 3/8' bbb is tremendous. That extra half a pound per foot makes a big difference. We've had years of experience with both on the same boat, same anchor.

[lancelot9898]

Originally Posted by GordMay

I understand that a heavier boat will carry more dynamic momentum, when in motion.
But, I wonder how much momentum, that heavier boat, can generate AFTER the catenary has been (mostly) straightened. Not much, I would think.

.

I haven't read through all the postings, but I can tell you first hand having stayed on the boat during a Cat 1 hurricane that momentum plays a very big role in that wind shifts causes the boat to almost sail at anchor. Not a very pleasant feeling and you just hope that the anchor remains attached to the sea floor as you introduce the shock loading on the rode. Another factor that adds momentum in that the stretch that is introduced during a gust will propel the boat like being at the end of a rubberband when that gust dies. Wave action is the final and could be the most important contributor to momentum.

I'm probably in the minority in that I prefer BBB due to the shorter link, heavier weight and it will distort prior to failure whereas the high test will show little distortion.

[motion30]

just a fyi Lowes home stores had american made chain in many different flavors at a decent price but the buckets are only 50' They even have a marine chain that is both gal and powder coated

[malbert73]

Originally Posted by Adelie

The second you get to wind strengths high enough to eliminate the catenary, it doesn't matter if you have BBB or G4, the only important thing anymore is scope. The difference in windspeed BBB and G4 to eliminate all sag will be on the order of 5kt or so. The difference in length to make them loose all sag at the same time would be like 10' or so. The difference is not worth quibling about.

I have to question this reasoning. I am skeptical about the sea of the pants estimates, and I really doubt any of us have survived anchoring conditions in which the wind speed eliminated the catenary of chain.

If we routinely anchored in conditions in which the catenary could be eliminated- ie the rode is straight- we'd all anchor with line or steel cable wire and save weight. Clearly in subhurricane conditions, weight of rode is a large determinant of scope needed.

So again, I maintain that BBB chain should require less length of rode (ie less scope) for the same holding power in ALL conditions, up until some otherworldly conditions that can stretch a 100 foot length of chain that weights 300lbs bar tight. Can someone refute this? If I were to brush up on my physics i could calculate the tension on each end of the length of chain required to stretch it straight, but I suspect that this tension is impossible in real world conditions.

[conachair]

Originally Posted by malbert73

I have to question this reasoning. I am skeptical about the sea of the pants estimates, and I really doubt any of us have survived anchoring conditions in which the wind speed eliminated the catenary of chain.

If we routinely anchored in conditions in which the catenary could be eliminated- ie the rode is straight- we'd all anchor with line or steel cable wire and save weight. Clearly in subhurricane conditions, weight of rode is a large determinant of scope needed.

So again, I maintain that BBB chain should require less length of rode (ie less scope) for the same holding power in ALL conditions, up until some otherworldly conditions that can stretch a 100 foot length of chain that weights 300lbs bar tight. Can someone refute this? If I were to brush up on my physics i could calculate the tension on each end of the length of chain required to stretch it straight, but I suspect that this tension is impossible in real world conditions.

Someone has done the figures already. With dynamics in the equation it might take a lot less than you think to lift the catinery off the sea bed.
It will never be straight.
Rode - Dynamic Behavior

[Adelie]

Originally Posted by malbert73

I have to question this reasoning. I am skeptical about the sea of the pants estimates, and I really doubt any of us have survived anchoring conditions in which the wind speed eliminated the catenary of chain.

It wasn't so much seat of the pants as recalling without looking up all the details as Earl Hinz discussed in 'the Complete Book of Anchoring and Mooring'

If we routinely anchored in conditions in which the catenary could be eliminated- ie the rode is straight- we'd all anchor with line or steel cable wire and save weight.

No we wouldn't, there are other reasons than catenary to anchor on chain (chafe resistance, less sailing about at anchor in light conditions, ...)

Clearly in subhurricane conditions, weight of rode is a large determinant of scope needed.

Not really so clear or there wouldn't be this discussion. I would agree that in subgale conditions that is the case.

So again, I maintain that BBB chain should require less length of rode (ie less scope) for the same holding power in ALL conditions, up until some otherworldly conditions that can stretch a 100 foot length of chain that weights 300lbs bar tight. Can someone refute this? If I were to brush up on my physics i could calculate the tension on each end of the length of chain required to stretch it straight, but I suspect that this tension is impossible in real world conditions.

The tension required to stretch a line of ANY unit weight perfectly flat is infinite. So you are right, that tension is impossible in the real world.

However, effectively flat can be acheived. When the sag gets small enough, it becomes easy to calculate the amount of give left in the chain. Give is how much further back the boat can move if the loads became infinite and the chain did go perfectly flat. A wave hitting the boat would be one means suddenly increasing the load a lot and needing give in order to avoid shock loading the anchor or deck hardware.

See attached screenshot of the spreadsheet I did with various sized chains in various wind strengths. The formula I used to calc sag is given at the bottom as is the URL where I got it. I calc'd give using the straight line distance from high to low to high again (length of chain) vs the straight line from high to high which was calc'd trigonometrically.

When the difference in give between various sized chain gets down to about 3 or 4 inches I figure that is close enough to being the same give. Sort of like falling and hitting your head on the floor, there is more give in a wood floor than a concrete floor, but not really enough to prevent a concussion.

From inspection of the spreadsheet you can see that by 30kt there is almost no give left in 100ft of BBB and marginally less in the same length of G4.

So if you consider 30kt or so to be otherworldly conditions then you are right you could use a somewhat shorter length of BBB than G4 and expect it to hold about as well or use the same length and expect it to hold a bit better. I think I have refuted your position.

The weaknesses of my method are that I assumed both ends of the chain were the same height, I assumed that all of the chain was immersed in water and the trigonometric method of calc'ing give slightly underestimates the correct value.

[GMac]

Originally Posted by conachair

Someone has done the figures already. With dynamics in the equation it might take a lot less than you think to lift the catinery off the sea bed.
It will never be straight.
Rode - Dynamic Behavior

Someone has in a real life non-spreadsheet used way. The loads are higher than many would expect to straighten a chain out (or as close as) and are often calculated.

Add that to current research that is strongly indicating the loads on the rodes are less than are usually calculated and we get to the conclusion if you use calculations with the numbers being commonly bantered around on the interweb, you are all good to go and have more reserve than you think, in some cases a lot more.

Have yet to see any calculations that take into account real life anchoring like drag coefficients, drag thru the water coloume and stuff like that, that does happen when you deploy gear off a boat and it does have a big impact on the outcome.

More news on this soon, still data collecting at the moment and as it's happening in real time on real boats it's not that fast. But it is damn interesting that's for sure.

Hey Adelie, In your SS, you have 'area', one being 310 and the other 470. What units are those in and from where? It's a nice work up but I can't quite work out what would have such area and still be using what looks to be tiny sized chain.

Oh and everyone don't forget commercial tolerances. By that I mean Batch A of say a 5/16" BBB chain could weigh 5 to 6% different than Batch B of the same chain. Usually more in the 2-3% area but can sometimes be more. The weights published tend to be the average rather than a spot on definitive as chain is bulk purchased and made by weight and the lb/ft number is there just for the end consumer. You may order 10, 30 153.5ft but I and the factory work in tonnes of XX" chain. In a 500kg drum (a common unit used i.e 6 drums of XXmm please meaning 3000kg) with 10mm in it can vary in measured length by over 10mts (33ft) sometimes. Today I ordered another 3000kg of 8mm shortie link so in 3 months I can expect we will have somewhere between 2225 and 2110 lineal meters arrive, which we will then sell by the metre.

I can fine tune those numbers if anyone what's to get jiggy with calculators. Will all be in metric though.

Oh and how's this as well as a FYI as to how it all works in the background with a companion product. Last week I ordered 1500kg of Polyprop, 4200kg of Nylon and 3900kg of Polyester ropes. The invoice has 3 lines on it as again we buy it by weight of the materials used. But the container will arrive with 107,930 metres (a tad over 67 miles, what a cool number) of ropes in it which we will be sell 'per metre' as very very few of you, none I'd expect, will ring and order 20.7lbs of 1/2" rope please, you will ask for 300ft instead.

And if you start talking china made the variations will be often considerably larger. All depends on how many Mazda and Toymotor dashboards/backseats are left in the steel While that is a giggle and probably not due to left over motorcar parts the weight variances out of there can be huge. As another FYI, a chinese company sent us some samples and with verniers their 20mm measured exactly the same as our Italian made 20mm but weigh 1mt and there was a 1030gram difference, which is massive. Oh the chinese was the lighter one of the 2, surprise NOT!

Sorry about the unit swapping, we are a metric country and I know many of you still use that old school and hard work British Imperial system

[Adelie]

Originally Posted by GMac

Someone has in a real life non-spreadsheet used way. The loads are higher than many would expect to straighten a chain out (or as close as) and are often calculated.

Where can I read about this?

Add that to current research that is strongly indicating the loads on the rodes are less than are usually calculated and we get to the conclusion if you use calculations with the numbers being commonly bantered around on the interweb, you are all good to go and have more reserve than you think, in some cases a lot more.

More reserve is good.

Have yet to see any calculations that take into account real life anchoring like drag coefficients, drag thru the water coloume and stuff like that, that does happen when you deploy gear off a boat and it does have a big impact on the outcome.

More news on this soon, still data collecting at the moment and as it's happening in real time on real boats it's not that fast. But it is damn interesting that's for sure.

Where's this happening? Are there any preliminary results published yet?

Hey Adelie, In your SS, you have 'area', one being 310 and the other 470. What units are those in and from where? It's a nice work up but I can't quite work out what would have such area and still be using what looks to be tiny sized chain.

Area is frontal area in square feet (sf), used with the lookup table on the right showing wind pressure per sf to calc total horizontal wind pressure on the boat based on wind speed in kt. I presume it has bow height, beam, yaw, rigging and a factor of safety worked into it. I used the number Hinz had in his book, and picked 2/3 of that for the second set of results.
0.869 is the conversion factor wt in air to wt in water that I calc'd using basic principles from density of steel(490) and water (64). Sag, which is in ft, is the bulk of the results table, while give is in inches, sorry for not specifying that earlier. Values for chain weights and air pressure came out of Hinz's book.

Oh and everyone don't forget commercial tolerances. By that I mean Batch A of say a 5/16" BBB chain could weigh 5 to 6% different than Batch B of the same chain. Usually more in the 2-3% area but can sometimes be more.

Given that 20% or so weight difference between different sizes of chain don't make much difference, I don't see worrying much about the 2-6% variation batch to batch weight difference.

Sorry about the unit swapping, we are a metric country and I know many of you still use that old school and hard work British Imperial system

I'm an engineer so metric doesn't bother me. Not as comfortable in metric, but only because of lack of practice. Would happily convert.

Something that just occured to me is that the wind load is horizontal, whicl the rode load has a significant vertical component in it that increases as the scope decreases. So for a given horz wind load the chain load will be significantly higher and the sag will be even less than expected.

[allanpeda]

Why not jump in here. I'd tend to stick with the 5/16 for anchoring.

From what I read, I'd have no problem swapping out *new* 3B 5/16 chain for *new* 1/4 inch grade 40. But, I'd bet the rate of wear on the 1/4 will be a bit greater due to the smaller link diameter (circular area).

McMaster Carr has galvanized 5/16 chain for $3.00 per foot (3588T23), rated at 3900 lbs WLL. The 1/2 inch nylon rope is rated at 3200 lbs, though I'm not sure of the factor of safety methods and how they compare. Point is you would match the rope strength to the chain.

All this talk of the catenary strike me as over analysis. Dynamic systems are tough to model. Toss out at least a boat length of chain, wear gloves and go sailing.

[Shanaly]

your 1/2 in nylon bridle would appear to have a 2T breaking strain, has that been adequate in extreme conditions, may I ask?