MF 605 - 8mm mooring lines ??

[Deleted]

The manual of my 605 says the anchor points can have mooring lines with a maximum breaking strength of 1000kg/9,7kN
In practice this means (polyester) mooring lines of 8mm thickness

8mm mooring lines seem VERY thin to me.... !?

Any thoughts ?

THANKS,
V.

[rene460]

Hi vronsky,

I tend to agree that 8mm seems thin, but your wording seems to imply that the mooring weak point is actually the cleats.  So the suggestion is to have ropes which break first.

However, 8 mm does not allow much margin for a bit of wear and tear, or degradation in sunlight.  Using 10 or 12 mm lines will not increase the mooring forces, will give a bit more margin for wear and tear, but risks tearing the cleats out of the deck if higher loads are experienced.  If your mooring system fails in a storm, tearing out the cleats will be the least of your issues.

The mooring loads are determined mostly by the snatch loads due to waves, not by the size of the ropes, and are best reduced, if you have these conditions, by installing Spring snubbers or similar devices in your mooring lines.  Waves are not usually a problem in a sheltered marina, but if your pen is exposed to waves with a bit of fetch, the snatch loading can be quite extreme.  In that case, springs on the mooring lines are essential.

If you live near your mooring and can inspect it often, particularly in bad weather, I suggest the recommended mooring lines would be fine, just keep a close eye on wear and tear.  If, like me, you are several hours away, I would use the larger lines, in case of fraying during a storm.  And instal those springs to minimise the snatch loading.

With all that, I would be quite confident that the cleats are adequate for your size of boat.

Rene460

[Deleted]

Hi Rene,
Thanks for your reply.

Yes its true: the manual explicitly specifies for the cleats a maximum load of 12.1 kN, and recommends a max breaking strength for attached mooring lines of 9.7kN/1000kg... so 8mm

In consequence, any warranty compensation will be void for all damages to cleat & deck/hull when using a stronger line .... 
Not a trivial matter actually.

I have indeed rubber snubbers on my current (apparently too strong) lines now: these work great to soften the shocks on the cleat

Best Regards,
V.