Advice on dimensions for standing rigging?

[gregorius]

I am going to replace the standing rigging on my Colvic Victor 40. At present it is set up with 8mm x 19 ss for backstay and spans and 7mm for lowers on main mast, while all are 6 mm on mizzen. Would it be adviceable to go up one dimension on the wires? I plan extended offshore cruising in the near future.

 

[[2574]]

I'm just having my Nauticat 39 done this very week. I asked a similar question of Nauticat in Finland (because the latest reincarnation of a 39, the 385, has heavier standing rigging) and was told that on no account should I increase the wire size as it will put more weight aloft for no good reason. The righting moment is (apparently) the key factor in rigging sizing and it is the size it is for good engineering reasons. Increasing the weight aloft unbalances the naval architects sums of keel size and weight etc. I was told to replace with identically sized wire which is what my rigger is doing.

rob

 

[Poignard]

Another drawback is that the larger diameter rigging may come with clevis pins that are too large for the holes in the chainplates and mast tangs. The temptation then is to fit undersize pins, or enlarge the holes; neither of which is "best practice"

 

[Gargleblaster]

I had a problem where I thought my rigging was stretching and was going to increase teh size ona some what smaller boat. One of the things I looked at was Dyform rigging which is 50% stronger for the same size and 50%dearer as well.

 

[alandee]

I am no expert in the matter and was contemplating doing the same thing to my yacht. However from reading a number of books on the subject and talking with riggers I have decided not to. Apart from the problems noted above by other forum members, stronger standing rigging can put more stress on the chain plates and in turn on the structure of the boat around the chain plates. Rigging failure is one thing ( ARC blogs this year give a couple of examples) but hull structural failure could be a whole bigger problem. Having said that, I wouldn't want either!

 

[KellysEye]

>Increasing the weight aloft unbalances the naval architects sums

True but I'd suggest it's academic. If Gregorius is going offshore cruising he'll probably add some two tons or more of kit to the boat. A little more wire weight won't be noticeable, so I'd increase the size. As the previous owners of our boat did.

On the subject of strengthening rigs - if anybody has tubular spreaders welded to smallish plates, bolted to the mast, the welds can break. So run an appropriate length/diameter of old propshaft from one spreader through the mast and into the other spreader. Hold in place with split pins.

On reflection, if you look at most dismastings it's not usually wire failure that causes the problem it's fitting failures. Moral of that story is use Sta-loks rather than swaged fittings and get rid of any ball fittings.