Which goop?

[Roger Long]

The chainplate design on my boat is a bit unusual but quite robust since the load is primarily taken by a large flange that is under the structural layup of the hull deck joint flange. The bolts primarily just keep the chainplates in position. The rig would probably stay up even with all bolts removed.

As I'm starting to prepare for re-installing them, I've discovered that they were bedded in an impressive thickness of compound, up to 3/8" in places. There is absolutely no sign of movement or breakdown of the compound after 30 years, 5 of which included my hard driving. I'm inclined to stick with what works and just re-bed using the old compound as a guide but there are areas where I will need to fill back to the original thickness and I will want a thin film of new stuff under the parts I'm leaving. I have no idea what was used in 1980 but it is still slightly resilient.

Anyway, what material would you use in this situation?

 

[Maine Sail]

The chainplate design on my boat is a bit unusual but quite robust since the load is primarily taken by a large flange that is under the structural layup of the hull deck joint flange. The bolts primarily just keep the chainplates in position. The rig would probably stay up even with all bolts removed.

As I'm starting to prepare for re-installing them, I've discovered that they were bedded in an impressive thickness of compound, up to 3/8" in places. There is absolutely no sign of movement or breakdown of the compound after 30 years, 5 of which included my hard driving. I'm inclined to stick with what works and just re-bed using the old compound as a guide but there are areas where I will need to fill back to the original thickness and I will want a thin film of new stuff under the parts I'm leaving. I have no idea what was used in 1980 but it is still slightly resilient.

Anyway, what material would you use in this situation?

Roger,

I would clean the underside of the deck very well then mix up some thickened epoxy, wax the chain plate and bolt it up against the underside of the deck and let it cure creating a beautiful load spreading surface. I call it "butter matching" the parts because you thicken up the epoxy to a peanut butter consistency. This is often done in keel re-sets too. Butter matching will give you a proper solid surface to distribute the load across instead of a few high points and some soft goop to fill in the voids..

I do not like sealant on the inside of the boat as if there is a leak it traps the water between the inside and outside and can eventually lead to crevice corrosion. Your overlapping hull deck joint is likely over 1/2" thick so that is the potential for 1/2" of trapped & stagnant salt water.

If I have a leak I;
1) want to know about it .
2) Want it to drain away from the stainless chain plate.

By sealing the inside you will often not know if the outside seal has been compromised.

 

[Bill Roosa]

if it is just a weather proofing job then polysulfide is what you want. Stays resilient (and does not leak) forever. Polysulfide can be used in compression/tension type arrangements to fill voids as long as the tension is taken by some other member. It can withstand the compression forces between, say a deck and the chain plate plate. Not entirely sure this is the arrangement you have though. It was intended to bed thru-hull bases and is rated below the waterline. It does take a few days to set up though so factor that in.

 

[Roger Long]

Butter matching will give you a proper solid surface to distribute the load across instead of a few high points and some soft goop to fill in the voids..

That was my first plan. However, the flange pressure at the moment the upper shroud wire breaks would only be 820 psi. Maximum pressure at knockdown would only be about 150 psi. Those generous flanges are a nice feature and get the pressures down to where nothing very fancy needs to be done. It's the jerking, flexing, and load cycling that make me think that something which remains flexible is the way to go. I would do final take up on the vertical bolts after the bedding sets up which I have plenty of time for.

The leak thing is a conundrum. The way my hull is lined and joinered, I would probably never see a chainplate leak. I have your tape and we discussed opening up the deck penetrations to a "V". I think that is going to be my line of defense and I will lift the chainplate covers more frequently than I have in the past. I will however, break the bond between the chainplate flanges and bedding with wax or Saran wrap so that any water gets worked out. There was, and will be, a complete filling of the space between hull/deck and angle flange so no significant amount of water could collect.

Solid bedding as you describe is still a Plan B. I'm going to take a closer look at everything today and could reconsider.

 

[Maine Sail]

That was my first plan. However, the flange pressure at the moment the upper shroud wire breaks would only be 820 psi. Maximum pressure at knockdown would only be about 150 psi. Those generous flanges are a nice feature and get the pressures down to where nothing very fancy needs to be done. It's the jerking, flexing, and load cycling that make me think that something which remains flexible is the way to go. I would do final take up on the vertical bolts after the bedding sets up which I have plenty of time for.

The leak thing is a conundrum. The way my hull is lined and joinered, I would probably never see a chainplate leak. I have your tape and we discussed opening up the deck penetrations to a "V". I think that is going to be my line of defense and I will lift the chainplate covers more frequently than I have in the past. I will however, break the bond between the chainplate flanges and bedding with wax or Saran wrap so that any water gets worked out. There was, and will be, a complete filling of the space between hull/deck and angle flange so no significant amount of water could collect.

Solid bedding as you describe is still a Plan B. I'm going to take a closer look at everything today and could reconsider.

Roger,

Our hull deck joint is identical construction but my chain plate is different allowing an easier view of any "leaks". Ours were bedded in butyl tape, from above only, and all six were still bone dry at year 31. The chain plates had zero corrosion between the decks. Our deck to hull joint of solid glass is nearly 7/8" thick. The nice thing about butyl is that it never "sets up" or needs time to. The stuff I pulled off our chain plates at 31 years old was just as flexible and gooey as new stuff...

 

[Roger Long]

I'm just back to pick up some tools after discovering that the other side of the boat wasn't done nearly as well. Very little actual contact between bedding and chainplate on the hull side yet little strain evident. There's nothing like spreading loads around. Still, I'm going to add some reinforcement in this area since the chain plate slots on one side are actually at the edge of the hull flange.

"Peanut Butter" is looking more attractive. Have you got a favorite recipe?

 

[kloudie1]

I had great results with West G-Flex, thickened with 404 high density filler.. Used that peanut butter to bed my new mast compression block.. Really strong and really good adhesion.

 

[Roger Long]

, thickened with 404 high density filler.

I inherited a bag of stuff from a boatbuilder who gave it up to go back to the real world. It's a fluffy white power that likes to blow away in a breeze. I think it might have been called something like "Cabosil". I know he used it to thicken up epoxy for fillets and such. Does that sound like it would be equivalent stuff? It's probably a West product because everything else in the box was.

 

[Maine Sail]

I inherited a bag of stuff from a boatbuilder who gave it up to go back to the real world. It's a fluffy white power that likes to blow away in a breeze. I think it might have been called something like "Cabosil". I know he used it to thicken up epoxy for fillets and such. Does that sound like it would be equivalent stuff? It's probably a West product because everything else in the box was.

My mix for that would be Aerosil/Cabosil and milled fibers. Sorry I can never remember West Systems secret code names for this stuff. You can also thrown in some chop but probably not necessary for this. What you have sounds like Cabosil/Aerosil..

Milled fibers are basically pulverized fiberglass that resembles flour, this & cabosil make a nice butter.

 

[Roger Long]

I went with "Peanut Butter" because I realize, looking at the fitting, the any slight movement would mean sheering of the bedding bond around the chainplate penetration and seal. The lower chainplates which I'm doing now were also put in with the flanges flat to the deck so that they were not aligned with the shrouds. I was able to move them closer to the right angle by letting the epoxy mix take on a wedge shape.

However, what a mess. I really fell off the learning curve on this one. What kind of wax works for this kind of thing? Who knew that partially cured epoxy sticks to steel coated with car wax as well as it sticks to anything else? I did try to take them off too soon but it was late and I was afraid I wouldn't be able to remove them in the morning because of the complex shape and epoxy that had run into the bolt holes.

No great harm done. I have a good base for doing it again with about 3/4 of the space filled. First, I've got to figure out what wax works.

 

[Maine Sail]

I went with "Peanut Butter" because I realize, looking at the fitting, the any slight movement would mean sheering of the bedding bond around the chainplate penetration and seal. The lower chainplates which I'm doing now were also put in with the flanges flat to the deck so that they were not aligned with the shrouds. I was able to move them closer to the right angle by letting the epoxy mix take on a wedge shape.

However, what a mess. I really fell off the learning curve on this one. What kind of wax works for this kind of thing? Who knew that partially cured epoxy sticks to steel coated with car wax as well as it sticks to anything else? I did try to take them off too soon but it was late and I was afraid I wouldn't be able to remove them in the morning because of the complex shape and epoxy that had run into the bolt holes.

No great harm done. I have a good base for doing it again with about 3/4 of the space filled. First, I've got to figure out what wax works.

Roger,

Collinite carnuba wax #885 or a "mold release" wax, which is also carnuba based, will work well. You also need to wax the bolts if using them to hold the piece in place. Alternatively you can use wax paper, mylar or, some "Saran wraps" work but then some don't so Saran is a crap shoot.

Do not "wipe" the wax off like you are shining something just coat it good and press it up into the butter and let cure fully. Be sure to coat ALL surfaces as the "butter" can be messy and can and will stick to anything not waxed. If it was waxed the epoxy will easily chip off when cured.

 

[Roger Long]

I was in Home Depot today and I saw a bench grinder for under 45 bucks. That made me realize that my wrists have improved enough that it's just been mental inertia that's had me wanting someone else to do the polishing. They didn't have the pads and compound so I drove three different places until I found those (at the hardware store I can walk to, wouldn't you know it). I was headed back to buy the grinder when I realized that they look a lot like the bench sander in my basement with the no longer available strange belt length on one end.

I took all the useless stuff off the sander, put on the arbor adapter I found with the pads, and I'm in business. My local store even had special, one step, compound for stainless steel which seems to be doing a great job following on Phil's taking off the worst with Scotch Brite disks.

The chainplates are all buttered in, a good solution. Any idea on a pourable, tenacious, flexible, substance to pour into the area around the chainplate up to the deck? I'm sure the Butyl tape under the covers will do a good job but it would be nice to know that area was filled in so no water could collect even though I'm leaving the faying surface between the epoxy and stainless steel dry. B tape and covers would then be a nice belt and suspenders set up.