composite chainplates

[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

[Stumble]

Scott,

The only composite chainplates I have seen are built integral to the hull. Where the carbon uno was interlaced with the carbon that makes up the hull itself. I have never seen anyone try to replace stainless chainplates with fiberglass like G-10.

[Mudita]

Stumble - fair enough. It does surprise me that we're not seeing it more, though.

Ben - thank you for the response. Another question, if you have the patience:

You mentioned "a lot thicker" for the fiberglass than stainless steel. This rapidly gets outside of my comfort zone for calculations but here goes:
[list=1][*]The G10 (or FR4) is a continuous fiber sheet with a tensile strength of ~35k psi.[*]E-Glass Tensile strength is often shown at ~500k psi. I'm guessing the difference between this and the G10 spec is that the G10 is when the glass is actually laid up? Like a real world application?[*]316 Stainless Steel is also in the 500k psi range


But of course, the actual strength is all about the layup schedule and quality control. Can you give a idea of how much thicker I should go than the original chainplate? I'm guessing somewhere between 2x and 10x. But I'd like to get within an order of magnitude!

[Brion Toss]

Hi,
I do like this thread, in particular that paper, with its information on hybrid joints. Chainplates are a transition point for rig loads, having to accommodate the needs of both the standing rigging and the hull (as well as the requirements for humans living in the hull), so it is not surprising that, since the dawn of rigging, so many chainplate configurations and materials have been tried. But basically there is a concentrated load where the piece of rigging attaches, shifting to a distributed load into the relatively tender, fragile hull. Built-in carbon fiber "fan" chainplates take this to an extreme, but glassed-in steel chainplates approximate the same thing. And both suffer from difficulty of examination, and of difficulty of maintenance and repair. Bolted-in chainplates can achieve acceptable levels of load distribution and accessibility, along with minimal intrusion into crew space. Tie rod chainplates can be at least as good at all these considerations, plus they feature a modular construction, plus they offer an opportunity to bring HM materials into the mix; picture a rope chainplate, readily inspectable and replaceable, wedded to deck hardware that carries the load to a strong point on the hull, via a metal or HM tie rod. This type of thing is already being done, with varying degrees of success.
While waiting for designs to improve, it is still most practicable to optimize existing configurations, polishing and sealing stainless better than we did in the past, or using titanium or bronze, etc.
Fair leads,
Brion Toss