Titanium bolts in marine environment?

[lustyd]

So a shock load = more likely to snap

+1 the cycling world stopped using Ti bolts anywhere it matters a long while ago due to sudden catastrophic failures being common. Lots of reports of Ti frames breaking too. Having a 40KG windvane hanging off the transom I'd stick to stainless. The weight saving might appear good to a human holding a bolt, but remember you're on several tons of boat so it will make almost no difference whatsoever in the grand scheme of things

 

[Rappey]

Many powerfull outboards are bolted on with 4 bolts. m10 possibly. imagine the shearing forces on full lock with 200hp yet never heard of ones falling off due to bolts snapping.
Vendee globe yachts have plenty of titanium fittings.. Satellites are also held together with titanium and have to endure temps around minus 270c and up to 460c.
Would guess the only reason titanium fittings are not mainstream is due to the high cost.

 

[lustyd]

Vendee boats are renowned for falling apart so possibly not a great example of reliability! Have a Google, there are plenty of sources for info on Ti bolt failure, and many in aerospace have been well documented.

 

[burgundyben]

Why not use 316? No problem with compatibility with the brackets and provided you seal well where the bolts go through the hull, should be no issue with crevice corrosion. Wise to use new bolts though.

The clue is here
Crevice corrosion

Having once found a bolt like that on my boat I became wary of 316.

 

[Slowboat35]

Why???
Has a Hydovane ever fallen off due to sheared bolts?
Specifying high-end aerospace fastenings at ruinous cost for agricultural applications like that is a sensible as goldplating your hull instead of using coppercoat or using uranium instead of lead in a keel.
Sorry, I'm quite sure this is totally unnecessary and a vast and inappropriate over-specification for a completely imaginary problem.

 

[Gary Fox]

My Aries is held on with normal 316 bolts and screws. The windvane main casting was smashed (into 2 pieces) by a Norwegian trawler, but the screws didn't break...

 

[Oily Rag]

You are about to embark on an experiment in the selection of new material. At least new to this application. Even if you get strength, hardness, ductility and corrosion right as a "designer", you propose in post #1 to use the internet to procure.

From my point of view, the quality control of such bolts would be my biggest worry. What will you specify? Can you be sure you will get it?

Perhaps easier just to follow the designer and use stainless. If in doubt, get their agreement to open up the holes to take 12mm?

 

[Tranona]

The clue is here
Crevice corrosion

Having once found a bolt like that on my boat I became wary of 316.

I am fully aware of the potential of crevice corrosion. It occurs when the stainless is in damp airless surroundings. Once you know that it is not difficult to avoid that condition in either wood or GRP. Simply exclude the potential source of water by doing as I suggested and use plenty of sealing in the hole as well as between the fitting and the hull. Not difficult.

 

[penfold]

Many powerfull outboards are bolted on with 4 bolts. m10 possibly. imagine the shearing forces on full lock with 200hp yet never heard of ones falling off due to bolts snapping.
Vendee globe yachts have plenty of titanium fittings.. Satellites are also held together with titanium and have to endure temps around minus 270c and up to 460c.
Would guess the only reason titanium fittings are not mainstream is due to the high cost.

Satellites are subject to fairly predictable loads during launch and weight saving is literally the most important thing about designing them; yachts belonging to YBW posters are (mostly)subject to the vagaries of british weather, late reefing decisions and price leads weight-saving by some margin for priority.

 

[Laminar Flow]

All due respect, but I think this is all getting a bit silly. The bracket is most likely loaded in shear which in this case happens at the interface between the bracket and the transom; the length of the bolt is quite irrelevant.
A 9.53mm stainless bolt will hold 2253kg, unthreaded. Unthreaded means that at the shear interface the bolt is solid, i.e. not threaded.
The two bolts holding on the bracket will therefore collectively support a load of 5 metric tons and you are worrying about a measly 40kg? By the time they break, your Hydrovane will either be horribly bent out of shape or you have already kissed your transom good bye.

 

[Mr Cassandra]

My Farr 45 performance rig had titanium blocks and sheaves

 

[burgundyben]

I am fully aware of the potential of crevice corrosion. It occurs when the stainless is in damp airless surroundings. Once you know that it is not difficult to avoid that condition in either wood or GRP. Simply exclude the potential source of water by doing as I suggested and use plenty of sealing in the hole as well as between the fitting and the hull. Not difficult.

I agree, but...

In the case of my shaft A brackets, once its all installed I have no way of knowing if crevice corrosion is happening unless I periodically disassemble it. That was the case with the bolt and washer on coxeng, it looked perfect until I dismantled it.

I'm condidering the use of titanium bolts to remove the risk of unknown crevice corrosion.

 

[Halo]

As always things are complicated .Nuts and bolts work as a system. When you torque them up the bolt is stretched slightly and the resulting tension holds the assembly together. You would need to know the correct torque and whether the likely higher crushing force is ok for the boat when usin

 

[Halo]

As always things are complicated .Nuts and bolts work as a system. When you torque them up the bolt is stretched slightly and the resulting tension holds the assembly together. You would need to know the correct torque and whether the likely higher crushing force is ok for the boat when using Titanium. If the system needs nylock nuts are these available.
In some applications titanium is anodised. Not sure if this is needed for marine ones
As others have said it seems an unnecessary experiment

 

[vyv_cox]

I had crevice corrosion in ss (don't know what though) bolts going through the ply hull securing the rudder stocks on mine. Replaced them with ss, should check again, but I'd probably try bronze next time...
titanium is impressive, but also as someone mentioned v.brittle and doesn't take bending (iirc)

Stainless steel bolts in wet wood are just about the perfect recipe for crevice corrosion. A copper based alloy, tin or silicon bronze, would be a far better choice.

 

[Daverw]

I bought some titanium bolts last year to see what they were like, the cost was not much more than stainless, assume that they are becoming more commonly used for custom cars and bikes etc, could not believe how light they are

 

[lustyd]

Bikes use Ti bolts because of the bright white sparks against the road surface, generally not because they are better bolts

 

[Zing]

+1 the cycling world stopped using Ti bolts anywhere it matters a long while ago due to sudden catastrophic failures being common. Lots of reports of Ti frames breaking too. Having a 40KG windvane hanging off the transom I'd stick to stainless. The weight saving might appear good to a human holding a bolt, but remember you're on several tons of boat so it will make almost no difference whatsoever in the grand scheme of things

Possibly the wrong grade, bought on ebay from a Chinese supplier who doesn't give a damn. Made from grade 2 instead of 5. Easy to machine and as useless as cheese.

 

[Tranona]

I agree, but...

In the case of my shaft A brackets, once its all installed I have no way of knowing if crevice corrosion is happening unless I periodically disassemble it. That was the case with the bolt and washer on coxeng, it looked perfect until I dismantled it.

I'm condidering the use of titanium bolts to remove the risk of unknown crevice corrosion.

The main lesson from looking at horror pics is to understand the causes of the problem and take steps to eliminate them. Remove the source of damp and crevice corrosion does not happen. There is no reason why your bolts should move, so sealing the holes in the hull and the bolts eliminates the source of damp. Perhaps more challenging in a wooden hull, so need to make sure it is completely dry around the holes then line them with epoxy. I did that with all the bolt holes below water in my plywood hull. Also worth doing with GRP hulls. Bed in a sealant/adhesive then no chance of any leaks and bolt is isolated from any damp.

 

[lustyd]

Possibly the wrong grade, bought on ebay from a Chinese supplier who doesn't give a damn. Made from grade 2 instead of 5. Easy to machine and as useless as cheese.

No cyclists generally use top tier stuff. As a hobby it’s relatively cheap and has no ongoing costs so extravagant components are everywhere. I have carbon fibre bottle cages as a good example, and they make boats look cheap!!