Bigger the better. 2 tonnes isn't large in either size or weight.
Concrete is fine as long as you spud the air out of it. As mentioned above if you just pour it into a mold
it'll retain a lot of air so lose that and it goes from OK to damn good.
A 'spud' is like a vibrator, yes probably the vibrator you are thinking of, a ladies personal friend one might say. The concrete ones buzz away as you pour the concrete and it makes the air rise and come out. You can usually rent one for a couple of hours quite cheaply. I doubt diving
into the girlfriends drawer when she isn't looking would have the power for concrete. Did I say that all nicely enough?
is also good especially in deeper waters or when there is a soft bottom. That will often sink into the mud and increase the holding hugely. Rust shouldn't be an issue as you want a stinking solid lump of something. Train wheels are very good but you'll probably need a few of them. Some old huge flywheeel is a goodie as is a forklift counterweight. If you go with a counterweight make sure there is enough water
over it at low tide, you'd look pretty stupid running aground on your own weight.
If going concrete and making your own, which is easy to do, try to make it flat or do-nut shaped and with a concaved bottom if you are on a soft bottom as that will create a vacuum and increase the holding. Use some reinforcing stell in it and into that tie a coule of the biggest sized mooring
lugs you can, 2" is good. Use big as they last longer and put in more than one so when one wears out, assuming it does, the block is reuseable and not becoming seabed clutter.
Also don't muck around with bottom chains less then 1", get some old ships studlink and use that. It'll last so much longer and I've seen bottom chains last over 20 years comfortably. Less than 1" and you'll probably have to replace it a lot more often.
From the bottom chain (length being the same as water depth
at high tide long) chuck in a length (again water depth
long) of 5/8" or 3/4", if you have a bigger boat
, of a good open link chain and then to a good sized headrope, nothing less than 3/4", with chafe protection on it. Rope
to be another water depth length plus waterline to your bollard. Small rope
off that to a pick-up buoy. All done, clean simple and very very effective. Adjust lengths to suit water (mostly waves) conditions i.e. if it often ugly go long, if flat water and only wind
you can shorten a bit.
Put a good swivel at the top of the chains between them and the rope, that will eliminate any twisting issues. Use a big swivel, anything under 1" is probably a little small.
And use black or sometimes called 'self-colour' chains, not galvanised. They last longer.
The idea of using a the staged chains is to soften the boats ride in crap weather
. If it's set up right the studlink on the bottom will only come into play in nasty weather
and the block will have no load on them except in horrendous extreme weather. As the weather gets worse the boat
leans back on the mooring
so it has to lift
an increasing amount of weight so staging the chains allows it do to this without suddenly going fro some load to a huge load, hence the softer and safer ride for the boat.
The idea behind the lengths is you effectively end up with a 3:1 scope
, again a softer ride for the boat and better holding.
That does exclude local regulations
and swing room constraints if any apply. Check those out 1st, there maybe (usually is) some silly rules somewhere to trap the unwary.
I was a mooring contractor looking after 6000 odd moorings and the above is common as muck here. They last 3 years easily and next to none ever wonder off, those that do usually do so as the owner didn't check his head
rope now and again i.e chafe. Many of those moorings are just off the beach and beyond them the only wave break is Chile
, 6000 naughtycal miles away. I now supply the mooring dudes, which isn't as much fun but a lot drier and warmer in winter