2205 Duplex Stainless Steel chainplate fabrication

[Wind River]

Does anyone here have experience in fabricating with 2205 Stainless steel?
Specifically, experience in bending 1/2" thick 2205 plate.

I have been reading a lot about it, but it seems that there are many caveats that make me think twice about trying it myself. If this were just mild steel, I would either heat it up and bend it or put it in my press and bend it.

In reading about 2205, there is a very specific temperature range it needs to be in for hot bending and cold bending requires a much bigger bending radius than I have room for. It is said the minimum radius is twice the thickness of the piece being bent. I suppose I could modify the support the chain plate attaches too to allow for a bigger radius if need be.

Hot bending would allow me a tighter and much more controlled bend, as the spring back of this alloy is huge when bending cold. The graphs show a 45 degree bend will require about 60 degrees of bending to allow for spring back but is this the same for any thickness of material?

If hot bending, I would just heat the immediate area of the bend and not the entire plate. If I understand correctly, I would have to send out the entire piece to have it anneald afterwards for it to retain its strength and anti corrosive properties, adding to the cost.

The pictures show what I am trying to duplicate. I really want to improve upon the original material and the quote I got for these fabricated with titanium was way out of my budget.

Any experience here would be much appreciated.

[Adelie]

Why is there a double curve on these? Did they go out and around a gunnel? Do you have phots?

I would modify the substrate to allow the cold bending at the higher radius.

[Wind River]

Originally Posted by Adelie

Why is there a double curve on these? Did they go out and around a gunnel? Do you have phots?

I would modify the substrate to allow the cold bending at the higher radius.

That is the direction I am leaning also. It shouldn't pose too much difficulty.

[Adelie]

Very old time shippy looking. Not the greatest design.

Make sure the top bolt on the lower portion has a HUGE metal backing plate, it’s going to try pulling the bolt out thru the hull. By huge I mean equal to the total load of both shrouds combined.

[Wind River]

Originally Posted by Adelie

Very old time shippy looking. Not the greatest design.

Make sure the top bolt on the lower portion has a HUGE metal backing plate, it’s going to try pulling the bolt out thru the hull. By huge I mean equal to the total load of both shrouds combined.

Yes, I never really liked the look of it, but every Force 50 I have seen has their aft chain plates this way. I have never heard of anyone having a problem like that. Maybe the backing plates are adequate. You can bet though, that I will be the first when it does happen!

[darrelweb]

Whats wrong with 316SS and go a bit thicker, say 1/16 or 3/32?

The higher grade of SS is not warranted. My 2 cents worth.

Find a good sheet metal shop that does SS fabrication.

[Adelie]

2205 is a lot more corrosion resistant.

[Cheechako]

Often the bend radius can be larger than you think you want and not really be an issue, especially in non 90 degree bends. Conversely, although 2T or larger radius may be recommended, you may get by fine with a tighter radius in non severe bends.
With a shallower bends I have used 1T or even less in bending SS. Not done that alloy though. There really is little "bent portion" in a shallow bend. Also, the larger the radius, the less stress and likelihood of failure.

[Jim Cate]

Originally Posted by darrelweb

Whats wrong with 316SS and go a bit thicker, say 1/16 or 3/32?

The higher grade of SS is not warranted. My 2 cents worth.

Find a good sheet metal shop that does SS fabrication.

Depends on your point of view. Look at the number of threads here on 300 series chainplate failures, both 304 and 316... often in fairly young vessels.

I pulled our 2205 plates a few years ago for inspection: flawless, no pitting, no cracks, no elongated holes, no surface corrosion. At the time, the boat was 25 years old and had done well over 100 K miles at sea.

I think it quite worth the small extra cost of the duplex stainless.

In the OP's case, I'd be thinking of redesigning the area no matter which alloy I chose, for those complicated bends compromise the function of the plates. A simpler design would both strengthen the rig and reduce cost of replacement.

Jim

[stainless guy]

Find a fab shop and have them bend em for ya, x2T bend radius is not significant especially on an obtuse angle such as that most shops will have dies to bend and if they dont they are easy to make

Thats a "case o beer job"

[fabricator-ken]

Unless your chain plates are sealed from the air , there is know reason to use 2205. 316 ss is fantastic providing it is not deprived of oxygen. Eg : under water prop and rudder shafts. That is when you use 2205.

[Wind River]

Thank you all for the feedback.

I am going to continue to look into the 2205 duplex stainless. Cold bending seems to be the way to go and I should be able to find someone locally to do it.

I just sent out another email to a recommended source for titanium chainplate fabrication that may be much more reasonable than my last inquiry.

Regarding the re-design of the aft chainplates I would love to hear some suggestions there as I just don't see any practical way of doing it due to the design of the toe rail around the aft deck.

As far as the argument of using 316 stainless again, I really want to make these the last chainplates this boat sees. I believe the chainplates I have now are the original ones, and if so, they have been in service since 1982. I don't know how much sailing this boat has really seen so I don't know how hard they have been worked but they haven't failed yet. BUT.......

When I removed these chainplates they had no visible cracks or pits but they were not polished so maybe it would have been hard to detect with the naked eye. I sent them out to be polished and when the returned they looked beautiful, still with no pits or cracks.

I wrapped them up in foam and plastic wrap for one year and they sat on the V-berth waiting for me to paint my hull. One day I opened up one of the aft chainplates to look at them and this is what I found (see picture)

There were no cracks or any outward signs of a problem when I wrapped them up but it is painfully obvious now there was a crevice corrosion problem that could not be seem inside of them. This started my research on these kinds of problems and the more you look the more you find of similar problems. I guess you just don't believe it until you see it for yourself.

Some may argue that 36 years is beyond the serviceable life of a chainplate anyway, and they should have been replaced long ago. True, but It is hard for some (like me) to just look at something that looks perfect an replace it especially with the effort it takes to do on a job like this. I understand all the arguments for preventive replacement but in reality, it just does not get done in most cases. So for a reasonable amount money over the cost of 316 stainless, I could have a chainplate that will never need to be replaced again.

Sounds like a worthwhile effort to me.

[a64pilot]

Give allied titanium a call.
Having mine made from titanium wasn’t as much as I thought it would be, but my case is different, mine are encapsulated and not possible to inspect without removal, and removal is a very painful process, so much so that your crazy not to replace once removed.
With Ti plates, removal and inspection shouldn’t be necessary.

I do think they need redesigning, to simplify and straighten load paths, what you have is unnecessarily complex and looks like one day after building the boat someone said, you know we forgot the chainplates, and went about fitting some to an existing build.

[Wind River]

Originally Posted by a64pilot

Give allied titanium a call.
Having mine made from titanium wasn’t as much as I thought it would be, but my case is different, mine are encapsulated and not possible to inspect without removal, and removal is a very painful process, so much so that your crazy not to replace once removed.
With Ti plates, removal and inspection shouldn’t be necessary.

I do think they need redesigning, to simplify and straighten load paths, what you have is unnecessarily complex and looks like one day after building the boat someone said, you know we forgot the chainplates, and went about fitting some to an existing build.

I did give Allied Titanium a chance at the quote. They quoted $**** for only the 4 aft chain plates which is well out out of my budget. I will give the actual number to anyone who PM's me, but I don't think it fair to give the actual number as someone else's chainplate may be simpler and much less to produce. I wouldn't want to be responsible for scaring them away from getting their own quote. I will be trying another company tomorrow to see if they are in the same ball park.

As far as the redesign, I just cant see a way to straighten out those aft chainplates without loosing the wood trim. Like I said before, every Force 50 seems to have the aft chainplates like this and I have not heard of any failures or even concerns about them until now.

In case you cant see it in the picture there are long bolts that go all the way through the wood toe rail just above the upper bend. Maybe that helps enough with the potential movement higher up on the plate. They are only 1/4" bolts though.

[groundtackle]

Wind River. That is unfortunate and after polishing all of them, surprised someone didn't spot it on the first one?.
It's a material quality control issue consistent with vessels from Taiwan and the area during that period. Kept me employed over the last 40 yrs replacing that metal. Using documented 304 / 316 above the waterline, polished, and properly installed is perfectly acceptable. Go 2205 if you like but strength or corrosion is not the issue. As fab ken say's.. when underwater and or additional strength required without without increasing dimension, like in your stainless Excel anchor shank. You also need some thickness for a good turnbuckle toggle fit.
Except... the main mast backstays if they split back at the mizzen outboard. Those fwd angles and loads were never taken into consideration on many Force 50 and Formosas etc small mizzen shared chainplates. I can't tell from pics if yours are done right. You also can't eliminate the bends on without taffrail interference.
Chris