Composite Chainplates or External Stainless Chainplates?

[Chotu]

I Janis for the pictures of the stainless ones. They look simple compared to my plans for stainless.

One more question for the stainless crowd.

I don’t seem to have a bulkhead right where the stainless ones would go. My plans say you have to pick up a bulkhead with the stainless ones.

The composite ones spread the load far enough out you don’t need to pick up a bulkhead.

Do you all have a bulkhead attached to your stainless chain plates via the fiberglass involved with them?

[Thumbs Up]

No bulkhead near mine. A large enough piece of ply or composite sheet bonded to the inside of the hull should spread the load just fine.

[team karst]

Originally Posted by Chotu

I Janis for the pictures of the stainless ones. They look simple compared to my plans for stainless.

One more question for the stainless crowd.

I don’t seem to have a bulkhead right where the stainless ones would go. My plans say you have to pick up a bulkhead with the stainless ones.

The composite ones spread the load far enough out you don’t need to pick up a bulkhead.

Do you all have a bulkhead attached to your stainless chain plates via the fiberglass involved with them?

Pretty significant horizontal glass structure ABOVE the chainplates on mine. Bulkheads not very close. In fact, inside access is gained when one removes the head “medicine cabinet” liner.

[Chotu]

Interesting!!!

If the stainless install can be simplified from my plans, it’s making a lot of sense.

[Chotu]

Originally Posted by Thumbs Up

No bulkhead near mine. A large enough piece of ply or composite sheet bonded to the inside of the hull should spread the load just fine.

Very interesting!!

This could potentially be done without epoxy. I think. With a large enough bonding area, and strong enough additional composite sheet, other adhesives could be used.

It’s mostly a matter of filling the curvature.

I have some incredibly strong composite sheets that could be used for this purpose. Some 1/2” and 1/4”. Basically a polyester g10

[rslifkin]

Originally Posted by Chotu

Very interesting!!

This could potentially be done without epoxy. I think. With a large enough bonding area, and strong enough additional composite sheet, other adhesives could be used.

It’s mostly a matter of filling the curvature.

I have some incredibly strong composite sheets that could be used for this purpose. Some 1/2” and 1/4”. Basically a polyester g10

I agree, if you can spread the load enough, you should have no issues with bolting on stainless chainplates. If you don't worry about minimizing weight for the chainplate install, I'd just go for the "this is definitely stronger than it needs to be" option and not worry about whether it's the most optimized install possible.

[smj]

Originally Posted by rslifkin

I agree, if you can spread the load enough, you should have no issues with bolting on stainless chainplates. If you don't worry about minimizing weight for the chainplate install, I'd just go for the "this is definitely stronger than it needs to be" option and not worry about whether it's the most optimized install possible.

But if he goes with the “stronger than needs to be” option on everything he will no longer have a lightweight performance cat?
I questioned the small size of our chainplates and the “inadequate” fender washers as backing plates until I realized the rig has very low stress as we reef early due to being a lightweight performance cat.
Im guessing the Lagoon 400 has about the same sail area as we do but when they are considering their first reef we are considering our third. Which cat needs a stronger rig and beefier chainplates?

[Chotu]

If I am going off plan here, on such a crucial element, the question now becomes what are the specs?

[DeValency]

Originally Posted by Chotu

I Janis for the pictures of the stainless ones. They look simple compared to my plans for stainless.

One more question for the stainless crowd.

Do you all have a bulkhead attached to your stainless chain plates via the fiberglass involved with them?

Have three 8mm each ss chainplates at each side (supporting 4 shrouds at each side), none mounted to a bulkhead but to structural, fully integrated with the hull glass/composite ribs (~50mm thick).

[DeValency]

Originally Posted by smj

But if he goes with the “stronger than needs to be” option on everything he will no longer have a lightweight performance cat?
I questioned the small size of our chainplates and the “inadequate” fender washers as backing plates until I realized the rig has very low stress as we reef early due to being a lightweight performance cat.
Im guessing the Lagoon 400 has about the same sail area as we do but when they are considering their first reef we are considering our third. Which cat needs a stronger rig and beefier chainplates?

While the simple expected answer would be the Lagoon, there are additional factors, such as the design for the expected/intended use, rig and sail plan. For example, certain sharp stress levels on the shrouds are generated in rough seas - especially with cats…

[Chotu]

Originally Posted by DeValency

While the simple expected answer would be the Lagoon, there are additional factors, such as the design for the expected/intended use, rig and sail plan. For example, certain sharp stress levels on the shrouds are generated in rough seas - especially with cats…

Yeah. It starts getting weird here.

It’s interesting to come up with the idea that stainless would be better and easier. It sounds great! But going off plan is going to get pretty confusing.

What I can safely say is that each chainplate should be able to hold close to 20,000lbs.

The righting moment is what dictates all of this. And with at 25ft beam, I have a pretty good righting moment.

[smj]

Originally Posted by DeValency

While the simple expected answer would be the Lagoon, there are additional factors, such as the design for the expected/intended use, rig and sail plan. For example, certain sharp stress levels on the shrouds are generated in rough seas - especially with cats…

Maybe in this case over sizing of the chainplates would be a good thing.

[Thumbs Up]

Originally Posted by Chotu

Very interesting!!

This could potentially be done without epoxy. I think. With a large enough bonding area, and strong enough additional composite sheet, other adhesives could be used.

It’s mostly a matter of filling the curvature.

I have some incredibly strong composite sheets that could be used for this purpose. Some 1/2” and 1/4”. Basically a polyester g10

Perfect! You can do a "dry fit" and tighten the bolts to provide most of the clamping force to glue these in place (with the adhesive of your choice). Or install it as one and done (my favorite method) using 3M 5200 as both the bedding for the chain plate and adhesive for the composite sheet. I wouldn't worry about the extra weight at this point. You are not racing in the America's Cup. Compared to a production condomaran you are way ahead of the curve. This is no place to skimp. While 3/4" SS might seem like overkill, the extra thickness is nice to keep the toggle pin more centered. Thumbs Up's are 3/8" I also have a 25' beam but am 41' LOA and have a fairly small rig.

[Chotu]

Originally Posted by Thumbs Up

Perfect! You can do a "dry fit" and tighten the bolts to provide most of the clamping force to glue these in place (with the adhesive of your choice). Or install it as one and done (my favorite method) using 3M 5200 as both the bedding for the chain plate and adhesive for the composite sheet. I wouldn't worry about the extra weight at this point. You are not racing in the America's Cup. Compared to a production condomaran you are way ahead of the curve. This is no place to skimp. While 3/4" SS might seem like overkill, the extra thickness is nice to keep the toggle pin more centered. Thumbs Up's are 3/8" I also have a 25' beam but am 41' LOA and have a fairly small rig.

Going off plan like this sounds really easy, but also it’s pretty confusing.

I would like to see several examples of these being used on boats my size so I could get a good feeling for how to do the specifications on them.

I don’t really want to do more than is necessary weight wise either.

How do I know these could stand up to a 20,000 pound tug?

Where did the design for yours come from? You built them I take it? Where did you find the information to come up with how to do yours?

If clamping pressure is what holds them, it would stand to reason that a very large, but not very thick piece would work pretty well for the backing plate. As long as it could stand up to the torque of the bolts. That could save some weight.

[Chotu]

Thin water:

After a lot more reading, I noticed Stumble actually disagrees with you. Didn’t you quote him earlier in this thread?

These are copy/paste quotes from that thread discussing how chain plates work. A good read. But he prefers composite. LOL

Here are the direct quotes:


Eigen ,

Thanks for the explanation. I think I have mentioned this before but I am not an engineer though I have worked with them over the years.

Frankly I think any new boat that uses metal chainplates is missing out on a huge opportunity. Carbon or fiberglass chainplates woven into thehull laminate eliminate one of the most common causes of rig failure, and aren't that much more expensive to build or design. It really is a better mousetrap.


You do polish the whole thing, but that's because stainless is a stupid metal to make chainplates out of. The reason they are polished is to try and reduce the likelyhood of tensile stress crack corrosion... this on a metal that is know to suffer from stress crack corrosion, then put in service in a place where the likelyhood of salt water intrusion just has to be assumed.

Frankly after hocking titanium chainplates for a while it amazes me that we put up with it at all. Stainless chainplates are about the stupidest metal selection for the job you could have chosen.

For not much more than the cost of the stainless used boats could switch to composite plates tied into the hull during layup, or titanium plates. Composites would be my preference, but titanium is a direct replacement, costs about double, but will outlive the rest of the boat. Because it's completely non-corrosive you donthave to design a way to replace them. Heck you could use titanium chainplates as the core of the hull where they are pretty easily.