Titanium Chain Plates

[a64pilot]

I'm having a new set made for my IP 38 by Allied Titanium. They are to be made from 6/4 AKA Grade 5 Ti, most common aerospace alloy and strongest and hardest to machine Ti alloy that is common too. The IP chain plates are made from separate pieces of metal and welded together, they are more complex than usual.
I have had a couple of people ask me the cost, with shipping etc., it right at $3500 for all eight chainplates, ones made out of 316L are I'm told about $2,000.

[goat]

Thanks a64, I'm looking at replacing chain plates soon and deciding between forged bronze plate, ss and titanium. They're simpler in the PSCs, just straps on the outside, so probably a little cheaper. Let us know how they turn out.

[travellerw]

While I don't think those quotes are completely crazy, I would suggest people checkout oilfield/rig manufacture companies. They routinely build stuff in 316, inconel and titanium. They often have scrap lying around and may quote quite a bit cheaper than companies that specialize in it.

For welded chainplates, inconel might actually be a better choice. It would certainly outlast the boat, and probably everyone reading this forum. However I'm not sure if it would be cheaper.

[kentobin]

Hello,

I am planning on going with some titanium chainplates but one of the issues is what size should I make them? Titanium is stronger than stainless so there is no reason to make the new chainplates the same size as the old ones especially since I could also reduce the cost. I'm currently not sure how to determine what size I need without hiring an engineer or naval architect.

Did you go through this design process and if so what are your words of wisdom?

Thanks in advance.

Ken

[seandepagnier]

I replaced all of my chainplates 7 years ago with bronze. The replacement chainplates were twice the thickness and also wider than the original stainless making them a bit stronger.

It cost me $10 per chainplate for the bronze ordered from mcmaster.com . I drilled the holes myself using a manual (not electric) drill.

I have met some sailors who make chainplates from carbon fiber with good results. I think titanium is a waste for this application.

[Suijin]

Just finished pulling all of my chainplates today as part of my deck refit. After 31 years a few of them had some very minor pitting so they are condemned. Fabricator had quoted me $800 for the set of eight on casual inspection, but they are 3/8" and two of them are dog-legged so I'm assuming that will change the cost.

What's interesting is that they were not polished, and the rust on them was extremely minimal. They must have been really well passivated.

I'm going with polished stainless for the new ones, and I'll passivate them myself. As far as I'm concerned, the key to long life from your chainplates is making sure that the caulking is well maintained, something the previous owner of my boat did not do. So I expect the boat will be long out of my hands by the time it needs yet another set.

[Pauls]

Duplex stainless is a very good replacement for chainplates and any other highly stressed metal parts. 2205 is the most common alloy. About twice as strong as 316 and about twice as corrosion resistant as well. Available in round and flat bar, plates, etc.

[Jim Cate]

Originally Posted by Pauls

Duplex stainless is a very good replacement for chainplates and any other highly stressed metal parts. 2205 is the most common alloy. About twice as strong as 316 and about twice as corrosion resistant as well. Available in round and flat bar, plates, etc.

Agreed! While Ti is kinda sexy, and surely can make excellent chain plates, unless one is an extremely weight conscious racer type, 2205 gives far more performance per dollar invested. Machining and welding, while not trivial, are more straight forward than Ti.

As I've posted before, my 2205 CPs were inspected two years ago when they were 25 years and around 120,000 miles of age and were in perfect condition. Needless to say, I reinstalled them.

Jim

[44'cruisingcat]

Wonder why more boats don't have fibreglass or carbon fibre chainplates?

[seandepagnier]

Carbon can be bonded to the hull during construction, so you don't need bolts, I've seen this.

I think it's superior to titanium in all possible ways, so why would anyone consider titanium I don't know. Titanium anchor chain might be interesting.

My aluminum bronze chainplates aren't polished and they don't need to be despite lack of calking.

[a64pilot]

6/4 Ti is not significantly stronger than 300 series Stainless by size, it is by weight of course.
I had one of our Aerospace Engineers look that up for me, assuming 316 in the half hard condition and the Ti not hardened, it's a wash on strength. If you use Grade 5 Ti, the other grades are not as strong as 316 half hard Stainless. That surprised me too, always heard Ti was magic
Weight savings on Ti is not all that much, it's only about 1/3 over steel, so if you have a 9 lb steel chain plate, it's going to weigh about 6 in Ti.
Only real disadvantage I see with glass or carbon fiber plates is wear and impact resistance, clearly it will never "rust" and can easily be made strange enough.
I think steel is just too easy, is the established practice and why not if your a boat manufacturer?

I went Ti for several reasons, mostly because it's turn key, I send chainplates that were removed from another IP 38 to Allied Ti and ask how much? Then a well established manufacturer makes and send them to me.
I could have made them myself at work, bought the Ti, had it water jet cut, I'd have to have the welding outsourced though. But it would have been a lot of work and time I don't have, and I'm Retiring, so I use work assets rarely.

One day my boat will be sold. If you were looking to buy, would you trust homemade chainplates that are glassed into the hull and cannot be inspected, or ones made by Allied Titanium?

Labor to R&R chainplates on an IP is excessive, about $8,000 to have it done by a Pro. So I never want to have to worry about them again.
Chainplates that can be accessed without too much work, I don't think warrant Ti in my opinion.
I guess point of my post is that turn key Ti plates are a little more than half again what SS ones cost, not five times as much or so.

[UNCIVILIZED]

Originally Posted by 44'cruisingcat

Wonder why more boats don't have fibreglass or carbon fibre chainplates?

Carbon fiber chainplates are essentially integral to the hull, & are built as a part of the hull, when the hull is being built. Many are made of long, long tows of carbon "draped" over a pin, & back into the hull's layup. With this being done many, many times until the required thickness/strength is achieved.

There are of course drawbacks. Fixing them being a primary one. Given that they're integral to the hull. So break one, & I think you damned near have to rebuild the hull in order to fix it. Plus they're a lot more sensitive to knocks, & dings than metal ones. This, along with little real advantage. As there are a lot of other ways to save a few pounds of weight in a boat. And the weight loss on an average sized boat is negligable really.

From what I understand of them, they make for good marketing ad copy. But other than that...
Given the option, I'd surely choose metal.

[Pauls]

Good thread, A64. Having your chainplates made by a company specialized in titanium is a good choice. They will know what they are doing.

As a general note to others that are considering titanium parts that require welding, under no circumstances allow a welder to weld Ti for you with a TIG or MIG. There are welders out there who will claim that they can do this successfully, and it is true that they can make nice looking welds. But Ti absorbs oxygen very aggressively at welding temperatures and the absorbed oxygen makes a brittle and weak weld. The only safe way to make welds that can be trusted with Ti is to have the welding done in a glovebox, ie the welding is done inside a box which has been purged of oxygen and filled with an inert gas. The flow of inert gas from a TIG or MIG is inadequate to ensure oxygen exclusion from titanium welds.

[Stumble]

Originally Posted by kentobin

Hello,

I am planning on going with some titanium chainplates but one of the issues is what size should I make them? Titanium is stronger than stainless so there is no reason to make the new chainplates the same size as the old ones especially since I could also reduce the cost. I'm currently not sure how to determine what size I need without hiring an engineer or naval architect.

Did you go through this design process and if so what are your words of wisdom?

Thanks in advance.

Ken

How small can you make them? Pretty small if you really want to but I wouldn't. The problem is that to really know how small you can get away with requires some real engineering, and the size difference is enough that attachment becomes an issue.

Determining how strong a chainplate should be is actually a little tricky, it isn't as straitforward as you would think. Brion Toss recommends chainplates that are 3 times the MBL of the wire because the excess amount is intended as the corrosion allowance. So litterly 2/3 of a chainplates strength is dedicated to corrosion.

So a 316 chainplate needs three times the working metal of a G5 chainplate since G5 is non-corrosive in the marine environment.

So how does this work in real life... the NA determines the ideal wire size with a mbl of 10,000lbs and wants to use Toss' Formula so the chainplates will need about a 30,000lbs UTS

316 stainless has a UTS of 84.100psi , so we need 30,000/80,000=.375 inches^2 of cross sectional area.

G5 titanium has a UTS of 138,000psi. But we can discard the corrosion allowances and only need a chainplate rated to 10,000psi. So the chainplate needs 10,000lbs/138,000psi=.0724in^2..

So you could get away with a chainplate that is about 1/5 the size of the stainless one and be perfectly safe. Even if the rig was stressed to beyond the maximum load the wire wouldn't deform long before the titanium would. So you may have very loose and stretched out wire, but the chainplates would be fine.

The downside to doing this is the entire rigging industry is premised on certain sizes of gear. Turnbuckles and clevis pins are sized around appropriate sized stainless components so there isn't off the shelf hardware the right size for our newer miniscule chainplates, and fabricating all new gear to fit... well that should going to cost you a lot. It also looks seriously scary to see a chainplate that small.

A second method I should to make the titanium plates the same strength as the stainless ones you replaced. Which means the titanium is only 63% the size of the stainless ones. This adds a little cost, but looks better.

Finally there is just size for replacement. This is often the cheapest retrofit option since everything else still works the same, reducing the cost of ancillary equipment and changes you will have to make and eliminating custom fabrication.

[44'cruisingcat]

Originally Posted by UNCIVILIZED

Carbon fiber chainplates are essentially integral to the hull, & are built as a part of the hull, when the hull is being built. Many are made of long, long tows of carbon "draped" over a pin, & back into the hull's layup. With this being done many, many times until the required thickness/strength is achieved.

There are of course drawbacks. Fixing them being a primary one. Given that they're integral to the hull. So break one, & I think you damned near have to rebuild the hull in order to fix it. Plus they're a lot more sensitive to knocks, & dings than metal ones. This, along with little real advantage. As there are a lot of other ways to save a few pounds of weight in a boat. And the weight loss on an average sized boat is negligable really.

From what I understand of them, they make for good marketing ad copy. But other than that...
Given the option, I'd surely choose metal.

It depends on how they are done, but they can certainly be fixed. Although I'm not sure how you'd break them.

No advantages? Unless you consider no corrosion ever, no leaks, no rust streaks, and that they'll last the life of the boat to be advantageous...

I'd never willingly have metal ones again.