Composite Chainplates or External Stainless Chainplates?

[Chotu]

Important factors:

Speed/ease of assembly
Longevity
Cost
Value
Weight/Performance


Important Considerations:

Composite - Have to hire a helper for complex composite lamination requiring 3 types of glass. Must hand laminate dozens of layers with epoxy that is painted over with polyester so I can go near the boat. Requires 2 employees. Have to buy epoxy and 3 types of glass. Chance employees could botch the lamination or leave bubbles. I can’t supervise (micro manage) that part.


Stainless - these are approximately 24” x 12” pieces of 316L Stainless 3/4” thick.
VERY pricey. Still some outside work to be done with epoxy. To mount them.


I’m leaning toward stainless since I think it’ll be cheaper and easier, but wanted to see if I’m missing anything via public input before I go for it.

[Chotu]

Hmmm. Surprises there are no strong opinions. This is similar to cat vs mono. Diesel vs electric. Ha ha.

I’ll add a poll for the shy types.

[Mike OReilly]

My boat uses exterior ss chainplates. I like them very much. Easy to monitor and maintain. I know nothing about your other option, so can't compare.

[Chotu]

Originally Posted by Mike OReilly

My boat uses exterior ss chainplates. I like them very much. Easy to monitor and maintain. I know nothing about your other option, so can't compare.

Ah! Thank you!

Maybe it’s not clear what a composite chain plate is.

This picture should clear that up.

It’s glass both inside and outside the hull, passing through a hole in the deck that is epoxied closed so there is no chain plate movement or leaking possible. Lighter and stronger than stainless. But seems to be a hell of a lot of work and problems that can go wrong if the employees make a mistake on them. Cheaper than stainless too, but not if I need to pay a 2 man team to do it.

No maintenance, no monitoring. They are a part of the boat itself.

[Sailmonkey]

With your boat, I’d find a glass guy to come camp out for a few days while laminating. I know thats easier said than done given your location, but not impossible.

[Bellinghamster]

Why 3/4" thick stainless? That seems excessive for a 50ft boat. Most are ~3/8". I'd go for SS - much easier to fabricate to reliable (i.e. engineered/calculated) strength with nearly no risk of screw-up. 316L, while having doubled in price this year, still isn't that outrageous if you go with mill finish from an industrial steel supplier and polish it yourself. Waterjet cutting is cheap and doesn't change the properties of the stainless.

12" x24" x 3/4" is ~63lbs of 316 plate, should be ~$200 in material, plus less than $100 to have it waterjet cut to whatever size/shape and all the holes you need (waterject to ream-able size). 3/8" thick would be half the material cost and about 60% of the cut cost.

[Thumbs Up]

I paid $250 including the materials for a shop to waterjet cut, bend and drill my 3/8", 316L chainplates. I polished them myself. You may need to bond reinforcement to the insides of the hull or at least will need substantial backing. You see some cats with smallish round or triangle external chainplates with the bolts arranged in a circle. You don't need to shy away from a complex or rounded shape plate because a good fabricator will just program the machine to do the cutting. The important thing is to have design specs correct for the load distribution. Is the placement (distance aft) already determined? If you go with the SS strap design it needs to be installed so that the bolts align with the load from the aft swept shroud. Visualizing this angle could be difficult. You could step the mast with temporary shrouds (halyards fore and aft with tied on bridle for side to side. With this method you will be able to eyeball the correct angles and measure exact distances for ordering the shrouds. If you go the composite route maybe there is a way to do it with prepreg to minimize the mess.

[Cheechako]

Why not Titanium chainplates inside like the originals? (just a thought)

What I dont understand about "external SS chainplates" is: They still have about 1/2 of the chainplate at risk for Crack Crevice Corrosion right? The side that is sealed to the hull. Why is that different than sealed inside the hull? Both have risk of trapped water subject to sealant failure.... ?

But wow, those are huge chainplates you are considering...? You using 1" diameter wire? :>)

[Jim Cate]

A couple of thoughts:

Why are you not considering carbon fiber for the chainplates? That seems appropriate for your application, although they do involve epoxy. They seem fairly simple to lay up, but of course, very careful layup is needed to ensure the outcome... just like with much of your boat!

Secondly, if you go stainless, why not use 2205 duplex? It is roughly twice as strong as 316L, has far better corrosion properties and isn't all that much more in price. You could go down in thickness quite a bit. And BTW, I agree that 3/4 inch seems kinda beyond normal practice for boats like yours. Are you sure of your scantling calculations?

Jim

[Matt Johnson]

Our stainless are a bit shorter, a bit narrower and 1/2" thick. Just to save you some leg work, I checked with Allied Titanium about having them done in Ti and it was around $2500.

I'd go composite if I could, but like you, I have enough compelling reasons to go the easier route of metal.... We're actually going aluminum now and upsized to 3/4" to compensate.

Matt

[Chotu]

Great responses. Thank you!

I’m going off the top of my head for the chain plate thickness. Not looking right at the plans. I figured a size up would have less people giving me a hard time than if I said a size down. Ha ha ha.

I think this is decided. I was already looking at stainless because it’s a lot easier.

Now, I have to research that 2205 stainless. Sounds like a great alternative.

Note: the composite chain plates are precisely engineered. As are the stainless. Just choosing between them. And yes, composite could be carbon, but I don’t have that lamination schedule and this is an area where I’m not making anything up as I go. So carbon is out only because I don’t have plans for that type of chainplate.

Yes, these angles will be supremely tricky. I will be starting a great thread soon with lots of pics called, “let’s rig my boat.” Already took a lot of pics of the mast. I was able to determine its a Francespar brand mast so getting a section to splice May be a go after all. That will have its own thread soon.

[Chotu]

Originally Posted by Cheechako

Why not Titanium chainplates inside like the originals? (just a thought)

What I dont understand about "external SS chainplates" is: They still have about 1/2 of the chainplate at risk for Crack Crevice Corrosion right? The side that is sealed to the hull. Why is that different than sealed inside the hull? Both have risk of trapped water subject to sealant failure.... ?

But wow, those are huge chainplates you are considering...? You using 1" diameter wire? :>)

Maybe titanium. Just have to see the cost.

[rslifkin]

You know either one can be made to work adequately in your application. So I'd start talking to some people about getting the stainless ones cut as far as availability, cost, etc. and maybe investigate what the cost and availability is of getting the composite ones made and installed. That will probably point you to which option is more viable in the end.

[Chotu]

Originally Posted by rslifkin

You know either one can be made to work adequately in your application. So I'd start talking to some people about getting the stainless ones cut as far as availability, cost, etc. and maybe investigate what the cost and availability is of getting the composite ones made and installed. That will probably point you to which option is more viable in the end.

That’s probably a good way to start.

However, the composite ones aren’t made and installed. They are hand laminated onto the hull. They are part of the hull.

[catsketcher]

The thing about composite chainplates is that they are no worry. Stainless chainplates will eventually need looking at -sometimes necessitating a nasty interior smash up. Stainless chainplates makes holes somewhere, where water can get in. For a light cat, it is never good to have water near a core.

You don't need two people to do a composite chainplate - my mate did his Schionning 1320 chainplates on his own. I have done all mine on my own. Use a slow epoxy. Composite ones take the loads and then spread them out over the bulkheads in a gentle fashion, rather than the point loads from a stainless chainplate. My stainless chainplates have welded on bolts that are tied on with carbon uni tow.

I have both types on my big cat, and only composite on my little cats. All are good, but for me composite is the way to go, cheaper, less stress concentration, no need to pull out and inspect after 10-20 years, no maintenance, no leaks and faster looking!

I think you could also make composite chainplate ends better able to receive lashed rigging if you want although a big shackle would do the same in stainless. I don't have your health issues though.