I consider 80m chain the minimum (which is unfortunately also the maximum for our boats unless you have your spouse playing chain rat and guiding the chain inside the locker when it is coming in) for mooring stern to with bow anchor.
If you go for 100m (which in all other aspects would be better) you should also install a radio controlled remote for your windlass, so that you can play chain rat yourself (at least as long there is no other traffic around). If I am alone and have to look out for other traffic, I pull in the chain except for the last 15-20m, hurry down to the chain locker (which I opened before), give the chain pile a kick and hurry back on deck to pull in the remaining chain. This way I can avoid a blocking most of the time. It is a pity that the chain locker is not accessible from deck.
Using less than 80m can be so embarassing if you still have 3m to the quay at the end of the chain ;). I even managed to do that with my full 100m in a wide basin where I misguessed the distance. I observed a guy once doing this mistake thrice in a row.
You normally want to use as much chain as possible in the harbour for a few reasons:
- You have to be absolutely sure that the anchor holds because between your stern and the concrete of the wall are less than 2 m. And some ferries can do a lot of surge.
- Most charter guys use less chain (probably because they don't have more on their boats). So your own anchor is out of the danger zone of their anchors.
- Some harbours have derelict mooring chains on the ground. You need to drop your anchor far beyond it unless you want to make the local diver happy (though there ARE some ways to get your anchor free again without diving).
Michael, SY Sioned, Maramu #148