No sealant between chainplates and inside of hull?

[redpointist]

I've taken my backstay's chainplates out to inspect and clean them up. They bolt to the INSIDE of the transom, and then pass through the deck (not sure why they didnt make them bolt to the outside of the transom, but thats another issue...at least theres no core in the deck where they go through).

Theres sealant where the plate passes through the deck and where the bolts go into the transom from the outside, but theres no sealant or bedding between the chainplate and the hull itself. The chainplates fell right off when I removed the bolts. I guess one advantage is that maybe having no bedding there increases the amount of oxygen available to the stainless surface against the hull (inside of hull is not perfectly smooth)? But Ive also heard that the friction of the chainplate against the surface its bolted to relieves some of the shear strain on the bolts. Would having bedding between the hull and the chainplate be beneficial by increasing this friction?

Should I bed them with butyl putty or something, or just put them back in like they were and stop overthinking this? Im not sure what the standard practice is for this kind of installation.

[SV DestinyAscen]

Have you had a leak? If not - why change the install.

[Shrew]

Why would you put sealant on the inside? If the chainplates are on the inside of hull, then you would only need sealant on the nuthead and washer on exterior of the hull.

Sealant is to protect from water entering. Sealing the interior would assume water has already gotten in.

[Dennis.G]

Recently replaced my chainplates, which are interior to the hull. No bedding between plates and hull when they were removed, and none used when I installed the new ones. Not needed.

Sealing the penetrations through the deck, while seemingly a simple process, has been a real headache however.

[Cheechako]

Any sealant will not prevent shear in an appreciable amount. It's flexible, if they are going to move they are going to move with or without it.

[redpointist]

I was thinking a bedding compound would increase the coefficient of friction between the plate to the surface its bolted to, reducing the load on the bolts, but its probably negligible and the extra sealant could encourage crevice corrosion.

Sounds like the standard practice is to forego any bedding there, which means less work for me!

[Exile]

I recently encountered this exact same scenario when pulling chainplates for inspection. No bedding btwn. plate and knees below decks, some evidence of leakage & external corrosion, but apparently any water that may have gotten behind the plates drained off because also no evidence of crevice corrosion.

Wound up replacing fasteners, washers & nuts but reinstalling same plates after a thorough, professional inspection. Had same quandary about using sealant this time but wound up opting to use a generous application of butyl tape. Only did so because the deck sealing plates are notorious for leakage, and even though I resealed all of them I figured it couldn't hurt to also seal behind the plates. Unlike conventional sealants which can dry out and fail over time, the nice thing about butyl is that if you get a sufficient "squeeze-out" all around as you tighten the fasteners you are pretty well assured that water will have no chance of penetrating for a long, long time. The stuff seems to stay flexible & pliant for decades.

Just my approach, for better or worse . . . .

[Crew of Turning]

Butyl Tape can be your friend in any compression connection that you make,toe rail to deck chain plates etc. Timeless commodity. Check out Compass Marine website .