G30 vs G43

[Djbangi]

Its not a big issue for trawlers but has anyone changed from G30 chain, or BBB, to G43 and also downsized (necessitating a change in gypsy, wildcat(?)). If so what was the motivation to change, at all, and why down size.

 

[bayview]

I don't know G43 but do know that BBB was designed to resist kinking. Any new links should be chosen with that in mind.

 

[C lectric]

I'll bite.
Last spring I changed from 100' of 3/8" chain + 250' of 1/2" nylon double braid

to

275' 1/4" G4 chain + 150' of 1/2" double braid nylon.

I wanted to keep the total chain weight approx. the same.
Back trouble drove the change.
The 1/4 G4 chain has the same or slightly greater strength as my old chain.
I am aware that the lighter per foot chain will not keep me as tightly located as the old 3/8 but it was a trade off I was willing to make.

I had an old Vetus Cayman windlass that was UP only and could not be converted. I needed a power UP & Down or I could no longer handle the rode.

I kept some nylon for the odd chance that i might have to anchor deep. It happens and if not prepared to go for 70' spots then anchoring can be limited. Of course if an emergency appears I can cut the nylon fast and attach a marker.

I figure I can manage once in a blue moon, the switch over between the nylon and the chain ,but not on a regular basis which I was required to do.
I have my helper/snubber line which can be used to hold the chain while I change from line to chain if I do anchor deep.

The new windlass has worked very well for me and so far have been on all chain and no where near the full length.

 

[Djbangi]

Hi E Lectric,

Now that I have a comment, obviously not a very popular topic I'll confess to the motivation and see how you respond (and whether it provokes any sort of reaction.

The numbers for chain designation refer basically to minimum breaking strength, MBS. So a G40 is 40/30 of the strength of G30. G43 is the same calculation (and G70 also - but that's confusing the issue). BBB, I think is an old designation, but is a G30 strength, different link size. (Though G30 and G43 are also different link sizes. G40 is a metric designation thug some imperial chain is G43 but sometimes described as G40.

Now everyone is really confused.

But to return to buying G43 as a replacement for G30 and reducing link size.

G43 has that minimum higher break strength than G30 with that simple relationship of 43/30

But when G43 is quoted for strength it is often sold with the Working Load Limit, WLL, prioritised (and sometimes the MBS does not merit a mention). The WLL is a simple calculation based on agreed safety factors. The safety factor for G43 is 3 that for G30, G40 (metric) and G70 is 4.

The use of a safety factor of 3 artificially 'lifts' the WLL for G43 over G30 - though there is no evidence at all that G30 is any more unsafe (or safe) than G43. I have questioned chain makers who sell marine chain in America and the reasons appear to have been lost in the mists of time but it might be because G43 was originally a Transport Chain (which had a safety factor of 3).

To sell G43 with a safety factor of 3 is quite accepted, its an industry standard for America, but there if one looks at the MBS then downgrading might size and upgrading quality might not result in the same MBS.

There is a trend in Australia to G43 to save weight - I simply wondered if the same might be true elsewhere and if anyone appreciated the implications.

I might add - failure of correctly sized brand name G30 is almost non-existent (so it seems perfectly strong enough - and possible 'over' strength, do not know). Maybe using G43 with a MBS less than the recommended MBS of the G30 does not matter - but I wonder if people realise.

 

[C lectric]

You have clearly dug into this more than I.

I was aware that the load factors appeared to be different.
When I made my decision I figured I would need to be more carefull with the chain, G4, when rust started to appear as that will affect strength more than with the bbb 3/8 that I had.

I think [hope] though that even so the chain is more than up to the task.

I had to keep the weight down. Yes it was important, to me. I simply could not increase chain length, get a heavier and more powerfull full function windlass and keep the same chain. My boat will not handle it without effects I was trying to avoid, weighing the bow down too much.

As it is there is a change in the trim and in the manner the boat handles rough seas. Not concerning, YET, but I am aware.

So no I was not fully aware of the implications of the WLL and the different Breaking load limits rating.

As you noted in Australia I was concerned with weight but also the overriding concern was I spent almost 8 mo. half crippled with back trouble and using a cane. So it had to change to as much push button as I could. I'm doing fine again.

My old setup required me to pay out 100' 3/8 bbb by hand and I could no longer expect to do it and use the boat.
I have copied your post for future reading/study as I like to learn stuff like this.

 

[Djbangi]

C lectric,

I'm glad you are back to better health, canes are for the future, long way off.

Unfortunately chain is low down on the interest list (which fortunately means most people are happy - nice to have products around that are safe!) so its difficult to get background info.

If you need help, send me a PM (if you start a thread, let me know, I might miss it) - If I have any knowledge its available to you. If I do not know, I'll tell you.

But best wishes, stay healthy.

Jonathan