Helix are great but you need special gear
to install them and remove them. Actually we have a growing problem here with used helixs not being removed. Once the top has rusted/worn away they are near impossible to get out.
blocks are just too small.
Disc shaped concrete block of at least 4000lb. If you can, a concaved bottom will dramatically increase the suction, this is good. Use rebar in the block and try to find some monstrous 2" plus steel
for the mooring lug. Put 2 lugs in so when the 1st is worn you have a spare, not just a big lump of useless concrete. Don't piss around with 3/4" or anything like that BIG is best. Either that or cast a 6" hole right through the block for putting the chain through (shackle back on itself.
Block to 4 times high water depth
1 1/2" chain (ex ships stud link is fantastic but similar is fine. Doesn't need to be galvanised) to 1 or 1 1/4" steel ungalvanised swivel to length of 1" minimum, 1 1/4" better POLYESTER rope
(3 strand is fine, 8 braid better) which is twice high water depth plus waterline to the bollard. Use anti-chafe hose. Splice nice loop boat end. From loop a high water depth length of 1/2" rope
to a pick-up buoy.
Assemble on beach on the low water mark. Weld all connections if at all possible. Tie a couple of 44 gallon drums to the weight and wait for the tide to come in. Float block into position and then USING A KINFE ON A LONG STICK cut the ropes between the drums and weight. DO USE A LONG STICK WITH A KNIFE, the drums will pop up fast with power.
Simple and easy yet strong mooring. Check swivel as it is usually the 1st thing to go. How long depends on local conditions. The big chain should last years, like 10-20 maybe more especially lying in mud. Headrope many years unless chafe gets it.
If decent wave action can happen add concrete and make head
rope 3 times high water depth plus w/l to bollard in length.
Mooring laid, open cold beers, done.
When you are not on the mooring it just lies dead in the mud so no wear and very little O2 so no rust. The only moving bits is the buoy rope and the buoy.
That's a simple mooring like we use down here and we anchor
on the edge of oceans as in land one side and 7000 miles of open ocean all the way to Chile
on the other. We generally would have a length of smaller 3/4" or 5/6" chain between the stud link and the head
rope though but then we moor more in 30-40ft than 5. We have a less than 1% failure rate.