rod rigging failure!!!

[Stuart Meyers]

Can someone please refer me to a article or explain to my owner / client nicely in laymens terms why you can not weld together sections or 316L stainless steel to make rod rigging. Apparently there is some joker located in Brazil that has been doing this for a hand full of yachts that have ended up in the caribbean. On this particular yacht when they got into a squall of aprox. 40 knots the upper streached out almost 4 " I can`t believe they did not loose the rig. and the amazing thing is that they want to replace it doing the same welding etc!!! Please help me convince them that that is crazy!!!!!!

 

[SvenH]

During manufacturing of rod, the atoms that make up the rod get aligned in a uniform way, so the same in every part of the rod.

When you weld two ends together this alignment islocally changed to a completely chaotic structure. There is no way whatsoever to make the atoms in the welded area realign so that they are as uniform as the rest of the rod. As a result the welded area is very, very weak compared to the rest.

Besides this, welding SS will include impurities that will weaken the weld even more, especially in a marine environment as salt water is one of the most difficult materials to protect metals from.

Welding SS for a marine environment can be done very well for tubing and such but in a high strength application like rigging, welding is foolishly dangerous!

Also, besides the welding issues, rod rigging had a much shorter life span due to less flexibility than wire. I'd say that unless you are a regatta sailor (and a good one), the extra expense (it is twice as expensive per year as wire) is totally pointless.

The lack of flexibility also shortens the life of a weld even further. So just stay away from welded rod rigging!

 

[Searush]

If it's a cost issue, would s/s wire rigging be cheaper? It may not be as good as all rod rigging, but it would sure be better than welded rod rigging!

 

[30boat]

Welding rod rigging is asking for trouble for the reasons stated above.There is a place for welding in rigging like in tangs,toggles and some mast and bow fittings where the welded are is large for the load.Some rigging screws have welded bits and never fail.

 

[vyv_cox]

316L in rod form is not quite as-cast but probably hot rolled and normalised. The Yield Strength (YS) of as-cast 316 is about 200 MPa. For the sake of argument you could call the YS of small section rod 250 MPa.

Wire for rigging purposes is cold drawn to increase its strength. Its YS is going to be 850 - 1000 MPa or so, it's quite difficult to find precise figures.

If you were to weld either of these you would effectively be turning them back to the as-cast condition, so the YS would again be 200 MPa.

A very quick calculation of rod rigging minimum breaking strength on this site gives me about 100 kg/mm2, which converts to 990 MPa. With material as strong as this the YS will not be enormously different from the UTS, maybe 80% or so.

 

[savageseadog]

Rod rigging isn't normal stainless either, it's Nitronic or at least Navtec's version is.

I'm not sure the life span is so bad either, it's possible to re-head the rods and I've heard of rods being used for considerable times.

 

[Searush]

Rod rigging isn't normal stainless either, it's Nitronic or at least Navtec's version is.

I'm not sure the life span is so bad either, it's possible to re-head the rods and I've heard of rods being used for considerable times.

You mean longer than the 38 years my wire rigging has lasted?

 

[30boat]

You mean longer than the 38 years my wire rigging has lasted?

Hope you wear a helmet when you go sailing

 

[Searush]

Hope you wear a helmet when you go sailing

Naturally.