The chain link size has to be very close to the gypsy size other wise the chain will jump....mine is labelled HT 3/8 P30, which means 3/8" or 10mm wire size and 30mm link length (inside measurement) , even a 29mm chain would jump off the gypsy.
This what my chain supplier in NZ told me :
Basically there are 4 chains in use around the world when you are
talking 'strength' and ignore the physical size. The 'grade' is basically a
strength thing, there are some other inputs but they are to do with technical
stuff we don't need to know. It doesn't matter what physical size the link
maybe as that has no input into the Grade. Some Standards are Grade specific
but these days it's gettinga little wild west with China and knowledge free
marketing departments getting too much in on the act. For example the
DIN766/A Standard, a common one, is a Grade 30. The ISO4565 Standard is a Grade
40. But Maggi use the same metal in all their anchor chains so their chains do
tend to be a lot stronger than some grades require i.e. their DIN766 is a Grade
40 just as their ISO Standard is.
Talking 10mm metric chains here
Grade 70 - Break load 11,000 kilos minimum. Some calling themselves G70 in the
US are more G60 so still bloody strong.
Grade 40 - Break 6,400kg. Common in the US, their G4 HT and becoming more
common outside of the US due to the Maggi AQUA4
Grade 30 - Break 5,000kg. By far the most common in use around the world. Also
known as Grade L, BBB, Proof Coil
China - Break 3,600kg and upward. Becoming very common as people buy on price
or fall for marketing. Some chinese made are just crap, some is OK though even
if it tends to rust fast. It's not often people selling this publish numbers so
who knows what your getting and as they often all look the same it can be a
lucky dip for the unknowing.
The CMP/Titan chain being sold in NZ and Aussie as 'Canadian' is actually
chinese made, hence the marketing comment.
In the industry the standard design (safety) margin from working load to break
load is 4 to 1 so we get the below -
Grade 40 (the AQUA4) - Break 6400 - WLL is a 1/4 so that's 1600kg.
Grade 30 (the PWB) - Break 5000 - WLL 1250kg
So the chances are very high your existing chain is a Grade 30, maybe a G40 but
unlikely to be higher.
And to talk me out of a sale even more, at the moment to regalvanise your 10mm
would cost approx $7 per metre ($3 per kg and 10mm is 2.3kg per mt) so about
1/2 the cost of a good replacement, even a bad replacement strangely. As we do
lean green here we think regalvanising is a good idea as it reduces waste over
time. So if your chain is only running short on galv we would suggest regalving
is the smarter idea.
The only thing you need to do is to check for wear. Look in the seats of the
link wherre they touch each other and look for wear. If you were a commercial
boat more than 10% reduction in the link size would mean you'd be told to
replace it. As you arn't commercial you can do what you like but as there isn't
any hard and fast rule for recreational and so many variations in what
recreational do with their chains we mention that commercial requirement just
as a idea at where to start.
Cheers
Alan
SV Elyse SM437
