composite chainplates

[asdf777]

I see. Yes, it's a good point. If there is air or some sort of impurity in the hull, it may be an issue with a composite chainplate. At the same time, from what I can find online, polyester is only 20% weaker than epoxy, so if there are no structural problems in the area where the chainplates are attached, the bond should still be stronger than a bolt.

It's more theoretical than practical discussion at this point, but I'd be curious to know if there are any other caveats.

Does a hybrid composite chainplate make sense? - both bolted and glassed in?

Thanks,
Gleb

[Stumble]

Asdf,

There are a lot of advantages in a new build to carbon plates, there are also some issues. For instance carbon and stainless need to be electrically isolated from each other to prevent galvanic corrosion issues. A better option would be a carbon/titanium structure.

One of the big issues with a retrofit laminate chainplate is that the entire load has to be carried by a single laminate bond, between the top layer of glass and the first layer of carbon. When done in a new build the chainplate carbon and the hull laminates are interwoven which greatly increases the bond area. There is no good way to replicate this after the hull laminate is finished.

[asdf777]

Hi,

Yes, I read about conductivity of CF and the article also mentioned titanium as pretty much the only metal not susceptible to corrosion in connection with carbon fiber.

In fact, I have a lot of respect for titanium from my childhood days and not averse to using it at all. It's just expensive, but otherwise is great! I grew up in the Soviet Union in a small town with a research center and my father worked with titanium for space projects. We had titanium pots and pans for camping, flasks, shish kabob skewers and I remember people were also making titanium car transmission protectors. No problems whatsoever. Light, strong and corrosion free. Also, completely bio-compatible, so it's really good as kitchenware, water bottles, etc. (cost aside).

Anyway, I understand the argument about the top layer being the weak link in replacing existing chainplates.

What do you think about hybrid composite chainplates (bonded and bolted)? This article seems advocate it for automotive applications saying that the resulted joint is stronger.

http://www.diva-portal.org/smash/get...FULLTEXT01.pdf

Thanks,
Gleb

[Stumble]

I don't think mixing the two designs adds much to be honest. If designed properly there is no need for the bolts, and if designed poorly I doubt anything will hold it together. The only reason to use multiple attachment methods would be if they each add something the other can't. In this case either alone can be designed to be ok. At least for chainplates this is true, other structures have different issues.

For a chainplate it is possible to bury the carbon over a large area, first by embedding it inside the layers of hull glass, but also by spreading it out fore and aft. So the chainplate roving looks like a fan coming down the side of the hull. This provides a huge contact area, that is integral to the hull.

Auto parts have different issues. Bonding area may be restricted, high volume production requirements have to be met, and cost effectiveness is a bigger driving concern. Not that the two areas can't look to each other for ideas, but they really are different worlds. The auto industry for instance has pretty much rejected prepeg carbon for a number of reasons, where the marine and aircraft industry has adopted it as the best option. But then the marine industry won't need to build thousands of units a day, and the aerospace industry is much less price sensitive than any other.

[Mudita]

Hey all you smart people.

I've tried to find other places where this thread picks up, but cannot, so please forgive me if I've missed where this is covered elsewhere. I also don't think this is a thread hi-jack, because we never quite answered the original question, and this is a practical application of the concept.

I'm replacing the chainplates on my 1979 Pearson 10M, which are 316 SS through-deck, bolted to a bulkhead below. They have significant crevice corrosion where they go through the deck, as might be expected after 35 years.

I'm considering a replacement with shop made fiberglass chainplates similar to the one this thread's first photo. I would bolt them in exactly as the old SS were done. They'd be hefty.

There seem to be wonderful advantages to new construction and composite chainplates because they can be integrated into the hull and all that. I have no interest in that discussion at the moment because it is a moot point for me. I'm all about a simple retrofit. The advantages I see for this SS to fiberglass retrofit are:

1) Never a worry about crevice corrosion again.
2) I can permanently fillet around them where they go through the hull, probably using West's G-Flex Epoxy, and never worry about leaks either.
3) They're cheap.

A few answers before the comments go off in unintended directions:

A) I don't intend to use the strength of an epoxy to wood/fiberglass bulkhead bond - this would be a through-bolted bulkhead installation, just like the original.

B) I know that bronze would solve the corrosion worries, but I'd like this to be about the potential of fiberglass, not the benefits of bronze.

C) I'm not concerned about resale value or insurance.

D) I am concerned about rig integrity, quality control, leak proofing, and good data on the cycle fatigue / bolt holding / crack resisting properties of such a chainplate.

That said, I can't find any photos of this having been done, and I really don't understand why. What am I missing? Can anyone point me to a good source of information on this concept? It's gotta be out there.

[benz]

Of course it can be done, if you use enough material. But to get the same strength as SS or bronze, you'd have to make the chainplate a lot thicker. I work with fiberglass a lot (in fact, I just made a set of chainplates pretty much like you've described). You'd want to make it mostly of unidirectional fibers, with an occasional layer of biaxial cloth to tie them all together. I don't think there's fatigue or load-cycle issues with fiberglass or carbon fiber, but you'd want to check with the engineer who also will tell you how thick and what sort of glass schedule to use. A look at G-10 specifications might give you an idea of glass compared to steel or bronze.
Ben

[Mudita]

Thank you, Ben.

You wouldn't happen to have any photos of the fabrication or installation, would you? Did you glass/fillet it all in at the deck?

Scott