My galvanised anchor chain is crusty and rusty and will not run through the windlass smoothly because the links stick together in a kink. So, I need a replacement, but would like to confirm the size. The Whitworths website has 6mm and 8mm and larger chain. I suspect mine is 6mm short link, but the links are actually 6.9mm. The increase in diameter could be the additional zinc galvanised layer.
Here are the dimensions, as measured by vernier callipers ...
Link diameter = 6.9mm
Link outside length = 31.2mm
Link outside width = 20.3mm
* Pitch (inside length) = 18.1 mm
Be careful as there is a slight difference between metric and imperial chain. If you get the wrong one it will not play ball with the gypsy even though they look very similar. So make sure you check if the gypsy is imperial or metric. I learnt the expensive way.
Before you go buying new chain have you pulled the old chain out on the dock and assessed if it is worth pickling and regalvanizing??
If in doubt, take your gypsy with you to a chain and lifting supplier like Bulivants and get them to size it. Price wil probably be cheaper than whitworths as well.
Thanks for all your advice. So, I removed the Gypsy (I now know what a Gypsy is, and how to get it out) and took it to RV Boating And Marine, who tried some chains for size, and confirmed that it is a 6mm short link chain. So I got a replacement galvanised chain, see photo below - new chain on left, old chain on right, Gypsy in the middle.
On reflection, the biggest risk with the old chain is not that it would break at anchor. Although it is possible that the chain would break, there is a bigger risk that it would not run through the windlass when you need to drop anchor in an emergency. It would jam because the crud and rust could fuse a couple of links together and they would get stuck in the hawse pipes (which is what happened when I was removing the chain in the berth). Because I'm mostly day-sailing in benign waters (Moreton Bay), a broken chain probably means a lost anchor and some inconvenience to your schedule. Not being able to drop anchor because, say, you've lost your rudder (been there, done that), would be a bigger problem because you might end up with a grounding or a collision (thankfully, avoided in my case, but that's a different story).
I suppose I am justifying the new chain on the basis that it will run smoothly through the windlass. The old chain could carry considerable load for many years to come, but it will jam in the hawse pipes when I might need it most.
i'd definitely be replacing that chain...
however if you need to save a few bucks, have you looked at end for ending the chain ? what is the inboard end looking like ?
cheers,
There should be a code under the Gypsy indicating the chain dimensions required. Suppliers can work off that.
New chain fitted. Took the boat out for a day-sail yesterday, dropped the anchor had a sandwich, and weighed it (the anchor, that is). The chain ran out and in smoothly, as it should. Very easy conditions and a nice day on the bay.
It might not sound like a giant leap, but the wife is now much less nervous about mooring, which is another positive step forward.
Select to expand quoteAchernar said..
New chain fitted. Took the boat out for a day-sail yesterday, dropped the anchor had a sandwich, and weighed it (the anchor, that is). The chain ran out and in smoothly, as it should. Very easy conditions and a nice day on the bay.
It might not sound like a giant leap, but the wife is now much less nervous about mooring, which is another positive step forward.
super !
it's all about keeping the girls happy isn't it ! 
cheers,
