Chain plate questions:

[Chotu]

So I am going with the stainless steel chain plates. It’s what’s practical right now.

I’m going to put them on the outside.

Questions:

1) What holds the chain plate in place? Is it the friction and the structural bog? Or is it the bolts?

2) Because my chain plate design has plywood in it, yuck, I need to drill out oversize holes, then fill in with Epoxy, then drill into the Epoxy. I don’t think I can “remove the core” with an Allen wrench since the core is fiberglass, plywood and epoxy. Nothing is tearing into that the way an Allen wrench removes foam or balsa from a correctly sized hole. So I have to drill oversize, right?

If I do drill oversized, that means I lose the outer layers of fiberglass that would usually be there.

What’s the best way to keep that plywood in the chain plate lamination from getting wet and rotting?

How do I deal with these holes?

[Bill O]

Do the oversized drilling, wet out the ply w/epoxy (maybe add 1-2% acetone to help it wick in), then use high strength gap filler w/some fumed silica to make a good epoxy fill.

Obviously the "epoxy guy" will do this work.


Can you drill from the backside to selectively remove the ply (w/ a hole saw) and leave the outer f/g skin?

[rslifkin]

If possible, do the over-drill from the inside as Bill mentioned. And only drill up to the outer skin, but not through it. That way you'll cover up the over-drill with the backing plate which should be strongly bonded to the hull. You drill the normal size holes all the way through, so the hole in the backing plate and outer skin are proper size, but the hole through the inner skin and core are over-sized, filled and then drilled through the epoxy at the proper size.

[GRIT]

I would drill and fill. Overdrill by 10mm ( 3/8" ) so you have about 5mm of solid epoxy around the bolts after redrilling. That'll be enough for the foam and the wood. I would pre-treat the hole with unthickened epoxy, before filling.

I would recommend West 404 structural filler for this project.

Friction is primarily what will hold the chainplate in place. But if it moves, due to the bolts coming loose, or the core crushing, then the bolts and holes will be all you've got.

Cheers, and good luck.
Paul.

[Chotu]

Originally Posted by Bill O

Do the oversized drilling, wet out the ply w/epoxy (maybe add 1-2% acetone to help it wick in), then use high strength gap filler w/some fumed silica to make a good epoxy fill.

Obviously the "epoxy guy" will do this work.


Can you drill from the backside to selectively remove the ply (w/ a hole saw) and leave the outer f/g skin?

Still makes me just a little bit nervous. Because that’s not as good of a core close out as I normally do.

Typically I drill a hole the right size, maybe just a 16th of an inch too big because the drill went crooked. Then I remove the core with an Allen wrench. Then I tape the underside of the deck, and a fill that entire void with neat epoxy which completely seals off everything. I pour in like 1/4 or 1/2 cup of epoxy or more straight in. It penetrates like crazy and seals incredibly well. Absolutely watertight.

Doing this on a horizontal surface with thickened epoxy just doesn’t sound like it’s going to provide the same type of watertight barrier that I am used to. Am I over thinking this?

And yes. Definitely. It’s Epoxy time on the boat. Meaning, I can’t go anywhere near the boat for a while. Trying to get all of these Epoxy jobs done at one time.

[thinwater]

I'd probably remove a large area of plywood from the inside, taper, and lay up solid glass. It is the bolts, and this will better transfer the shear load.



Sealing holes is fine, but for this solid glass is better.


If that sounds too much, drill from the inside, using a ~ 1" holes saw, fill with thickened epoxy and some chopped up glass cloth (for crack prevention), then cover the whole area with a big, thick GRP backing plate that is bonded to the hull. The backing plates replaces the inside skin and then some, and the plugs are big enough and have enough bond area to the outer skin and backing plate that they will not move or crack. (IF the plywood plugs won't pop out, drill them out with a Forstner bit with the point and edge teeth ground down--the hole will guide it.)

[Benz]

I drill big enough to slip a piece of G10 tube into the hole, the ID of the tube being the same as the bolt diameter. The G10 gets buttered up with thickened goo as it slips in (the hole also gets pre-wetted), then sanded/ground flush when everything cures. Now I have G10-lined bolt holes, which prevent core crushing and spread the load nicely.

[rslifkin]

Originally Posted by Benz

I drill big enough to slip a piece of G10 tube into the hole, the ID of the tube being the same as the bolt diameter. The G10 gets buttered up with thickened goo as it slips in (the hole also gets pre-wetted), then sanded/ground flush when everything cures. Now I have G10-lined bolt holes, which prevent core crushing and spread the load nicely.

That's a great idea!

[team karst]

rather a major change from earlier thread. Buying or fabricating the CP? using the Lagoon design of 3/4" or thinner? The forestay is composite, correct?

[Chotu]

Originally Posted by team karst

rather a major change from earlier thread. Buying or fabricating the CP? using the Lagoon design of 3/4" or thinner? The forestay is composite, correct?

Is it a major change? Before it was stainless versus composite chainplates.

I’m using the chain plates from the plans.

For practical reasons, I’m going with the stainless chainplates. There was also a bit of a mixup at the fabricator. I had asked for information on the chainplates, and they made them. They are doing a lot of other work, so I want to keep in good graces with them.

Chainplate straps are 1/2 inch, but the big load spreading part is 1/4 inch.

I have all stainless shrouds. That’s what came with the mast. They will need extending however. So the forestay is not composite.

[Chotu]

Originally Posted by Benz

I drill big enough to slip a piece of G10 tube into the hole, the ID of the tube being the same as the bolt diameter. The G10 gets buttered up with thickened goo as it slips in (the hole also gets pre-wetted), then sanded/ground flush when everything cures. Now I have G10-lined bolt holes, which prevent core crushing and spread the load nicely.

Question about this one. It’s a nice idea. I like the sound of it

But I already have local core in the boat that’s the right density for the chainplates. It was put in during the hull infusion process.

It won’t crush anyway. It’s straight from the plans.

Still a good idea?

It seems like things may crush a tiny tiny bit when the large part of the chain plate is tightened down, but then these G10 tubes will create hard spots instead of evenly distributing the crush load. This would cause less friction and an uneven pressure across the area the chainplates press on .

So, our chain plates working by friction?

[rslifkin]

Backfilling with epoxy will give a hard spot as well. The hard spots shouldn't be an issue, as while you're applying a crush load between the chainplate and the backing plate, if everything has enough surface area to handle the force of tightening the bolts, you won't actually crush the hull any measurable amount.

[team karst]

It takes very little movement for the chainplate to touch the bolt shanks when loaded. So, based on that, and the slippery nature of stainless, that the bolts, will have shear loads from the plate. 1/4" thick and how wide? how is the transition made from 1/2 to 1/4?

[MicHughV]

lots of ideas here...
https://www.google.com/search?q=cata...Ie08A-uk93IAOM

[Chotu]

Originally Posted by team karst

It takes very little movement for the chainplate to touch the bolt shanks when loaded. So, based on that, and the slippery nature of stainless, that the bolts, will have shear loads from the plate. 1/4" thick and how wide? how is the transition made from 1/2 to 1/4?

Its bolted on. But It’s way too complicated for me to explain here. It’s just how the plans are. I can’t give away the designers design. That wouldn’t be right.

As much as the designer is a jerk, I have to respect his intellectual property.