Stainless rigging.

[moondancer]

I am replacing all of the rigging in my Hurley 20. I understood that the original spec for the Hurley 20 was for 4mm stainless rigging, which I ordered. When I removed the old rigging from the boat I realised it was 5mm, possibly upgraded by a previous owner.

Does anyone see any issues with replacing the 5mm rigging on the boat with new 4mm rigging? I saw 4 mm rigging on much larger boats at the London boat show.

Brian

 

[ccscott49]

I reckon if it was meant to be 4 mil, then it is adequate for the job, as long as the threaded and fork ends are the same etc. Do the builders still exist, or is there an owners club? they should know.

 

[AndrewB]

4 mil is pretty light, even for a Hurley 20. If I were planning on taking it offshore, I'd be happier with 5 mil. It used not to be unusual to go above builders spec on rigging. The cost hardly comes into it.

 

[PeterGibbs]

You can't judge the guage needed by just looking at other boats. What holds their rigs up is a mixture of tensions, angles and compression, upper and lower shroud load spreads etc. For the small difference in price I would stick with the previous spec - after all someone made the decision to upgrade for a reason in the past?eh?

PWG

 

[ccscott49]

Or maybe he got 5 mil, cheap? Do you really want extra weight aloft?

 

[PeterGibbs]

Re: Stainless rigging- extra weight aloft..

Would you like to calculate the effect of installing 1mm heavier shrouds on performance? How many decimal points would you have to use?

PWG

 

[ccscott49]

Re: Stainless rigging- extra weight aloft..

I dont give two tinkers damns about weight aloft, it was an obsevation, thats all. What would the average owner know about the strength to weight ratios of stainless wire anyway. I still say if the vesselk was fitted with 4 mil in the first place maybe thats right, I would not assume anything until its checked, like I said the owners club or manufacturers. Was the last owner right, that is the question you should be asking!

 

[Guest]

Re: Stainless rigging- extra weight aloft..

I havent got the figures here to check (you need to do it), but calculate the approx tensile strength of 4mm wire at 4 tonnes. I would be very surprised if the structure of your deck would stand that sort of load in a 20ft boat. Most likely a previous owner has upgraded because 5mm was stronger and therefore "better". Apparently, this is a problem also with home built boats which are constructed way too heavy - the amateur builder knowing better than the designer!
If you are abs sure that the designers spec is 4mm, I wouldnt worry about it. But carefully check first.

 

[moondancer]

Re: Stainless rigging- extra weight aloft..

Thanks Howard. I will double check the figures.

Brian

 

[Guest]

It might be that the previous owner was aiming to improve the safety factor and thus reliability of the wire bu going up one size, a recomendation I have seen in many books and articles but usually related to long offsore passages whith constant cycling loads such as experienced in trade wind sailing! For any boat however it could be argued that it would increase the life of the rig. Also increase role inertia/capsize resistance. Whether any of this is significant for you boat is up to you and the sort of sailing intended plus the design of the boat. I find the maths fun on a winters evening but then I'm sad!

Roly, Voya Con Dios, Glasson, Lancaster