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post #1 of 36 Old 02-26-2013 Thread Starter
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Chain Plate Replacement

Planning on replacing my chain plates in next few months.

Current are 316 Stainless. Considering Silicon Bronze but material is almost impossible to find, and all I find is made overseas with questionable quality control.

Also considering Titanium. Apparently can get either overseas made or US (with added cost).

The only company I can find that can sell the material and fabricate to my dimensioins is Allied Titanium. Being able to have one company responsible for all seems to be a big plus.

Internet searches finds no company able to do this-
Do you know of others?
Thoughts?
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post #2 of 36 Old 02-26-2013
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Re: Chain Plate Replacement

Casey,

I work for Allied Titanium, so my advice is going to be prejudiced. But we make very affordable parts. Every now and then I have been underbid, but generally only if someone else is using remnants they just need to use up where we are using virgin metal.

You could look at a local machine shop, and there are a number of places on line that will do custom fabrication as well. But none of those shops deal with the volume of titanium that we do, or carry everything from the plates, to the nuts and bolts (unless they buy the fasteners from either us or Tico titanium).

The one thing I will mention is that depending on the size and cost of your plates it very well may be worth having a NA redesign titanium plates to meet the actual loads your boat experiences. Stainless plates are typically massively overbuilt to give a corrosion allowance, meaning a titanium chainplate can be a fraction the size. This results in lighter, stronger, and in some cases cheaper parts than going stainless.

For example, if you are using 1/2 wire, we could probably get away with a titanium bar 1/4" x 3/4 x leingth. Where a typical stainless plate may be 1/2x 1". I don't recommend this without a NA making the changes though. Which typically costs $100-$200.

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Re: Chain Plate Replacement

Do you have any knowledge of titanium being used for chain plates? I wouldn't think you could use the same dimensions as steel and get equal strengths and then there is the problem of titanium "work hardening", which could result in catastrophic failure. Work hardening could be minimized if everthing was very precise and no stress risers introduced by any of the components - clevis pins, bolts, etc.
I would certainly want an engineer experienced in titanium applications to design and specify your new chain plates.
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Re: Chain Plate Replacement

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Do you have any knowledge of titanium being used for chain plates? I wouldn't think you could use the same dimensions as steel and get equal strengths and then there is the problem of titanium "work hardening", which could result in catastrophic failure. Work hardening could be minimized if everthing was very precise and no stress risers introduced by any of the components - clevis pins, bolts, etc.
I would certainly want an engineer experienced in titanium applications to design and specify your new chain plates.
Check out this site:

Free Account - Allied Titanium

I would just stick with my stainless chain plate dimension then I would get extra factor of safety with titanium.
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Re: Chain Plate Replacement

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post #6 of 36 Old 02-26-2013
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Re: Chain Plate Replacement

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Originally Posted by casey1999 View Post
Check out this site:

Free Account - Allied Titanium

I would just stick with my stainless chain plate dimension then I would get extra factor of safety with titanium.
regards
This could be done but the cost would be about 2.5 times the same chainplate in 316 ss and not really any stronger depending the type of titanium you use. Grade 3 is about the same strength or maybe a bit less. grade 5 is a lot stronger but about 6 times the price of 316 ss. yes it will weigh less and it will not corrode but the 316 ss will last another 25 years and most will not keep their all ready 25 year old boat that long. the advantage of using the higher strength Ti alloys is you can engineer it to be the required strength with less material. therefore saving both weight and cost. the problem with that is the total cost will not be less due to the extra cost of re-engineering.
the chainplates are sized based on the hole size and width that is needed for the clevis. and if you choose a smaller size it may not support the clevis pin and it will wear excessively (point loading)
are you ready to tell your insurance company that you guess the engineer must have gotten it wrong and you think they should pay for a new mast.

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Re: Chain Plate Replacement

CC,

We make a lot of chainplates, and I have a good deal of experience with them. But as I frequently mention I am not a designer, and have no engineering degree, so the best I can do is point people to the answers, and help them find the right experts.

316 stainless is so much weaker than titanium, there really is an issue of overbuilding. While we do our best to drive the prices down, the raw material cost still adds up, and so if a NA can redesign (this is normally just a resizing issue) a chainplate and shave more than half the material from the part, well that is often worth more than his bill.

As an example:

The yield strength of 316 stainless is 32,000psi. While the yield for G5 titanium is 128,000psi. What this means is that a 1" cross section stainless bar will distort at the same point that a 32/128= 1/4" sectional area titanium bar will distort. So you build in a massive amount of additional strength. Combine this with the fact that most chainplates are so overbuild in the first place and you can realistically see titanium chainplates that are 20 times stronger than they need to be.

So how strong should a chainplate be? Well ONLY a NA can tell you, but a good place to start is with the size of your shrouds, since they transmit the load the chainplates need to carry. If we said someone has 1/2" shrouds with a breaking strength of 19,000 pounds, then chainplates any stronger than this are redundant because the wire will break first. Which would put us in the range of a 1/8" sectional area titanium plate. Of course this makes the rest of the system hard to work with, so in reality you have to upsize the titanium a little to fit tangs and bolt holes.

So why do designers overbuild chainplates in the first place? The simple answer is that they know that localized corrosion is the single biggest cause of chainplate failure, and the only way to delay it is by making the plates much larger than need be. This is called corrosion allowance, and is a good engineering tool. However, since titanium doesn't need a corrosion allowance when used for chainplates, there is no need to maintain these massive corrosion allowances.

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Re: Chain Plate Replacement

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Re: Chain Plate Replacement

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This could be done but the cost would be about 2.5 times the same chainplate in 316 ss and not really any stronger depending the type of titanium you use. Grade 3 is about the same strength or maybe a bit less. grade 5 is a lot stronger but about 6 times the price of 316 ss. yes it will weigh less and it will not corrode but the 316 ss will last another 25 years and most will not keep their all ready 25 year old boat that long. the advantage of using the higher strength Ti alloys is you can engineer it to be the required strength with less material. therefore saving both weight and cost. the problem with that is the total cost will not be less due to the extra cost of re-engineering.
The cost premium for size to size replacement is no where near six times. It really depends on the size we are talking about, but G5 typically runs less than 50% more than 316L. If we are doing a whole boat with say six chainplates, spending the $100 or so to have a NA reengineer the chainplates is commonly more than saved by the reduced cost of the parts.

Of course the idea would be for boat builders to make the switch to titanium from the beginning, so no one would ever have to replace them in the future. For an Island Packet 38 the cost difference would run about $400 on a new boat if IP were to choose to make the switch.

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Re: Chain Plate Replacement

I love the idea of using Titanium but I just can't see how to justify the cost for material. about a year ago I helped an friend change some chain plates. I bought 6' of 1.5" x 3/16" 316L stainless steel flat bar for less then a $100 . I priced G5 Titanium 6' of 1.5" by 1/8" with several suppliers and the best price I was given was $ 596 about 6 times as much. boat is sailing just fine on the 316L chainplates and $500 of beer and steaks.

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