| Wow Nathan! What a lot of work. My surveyor checked all around with hammer and moisture meter and said he thinks there’s no rotten areas so 🤞. I have an oscillating tool - are you saying use it to bevel the edges of the deck under the chain plates? I’m pretty good with detail work using it but want to make sure I understand what you are saying. Thanks again. Janet Sent from my iPhone Janet and Joel,
The main thing for success is making sure there is sufficient counter sink relief for a gasket of bed-it around the fastener and then tighten the hardware down gradually so the "tape" can flow, ideally over the course of several days or weeks. For bolts make sure the bolt doesn't spin when tightening - only the nut should be allowed to spin. For self tapping screws (e.g. on the chain plate covers) this isn't an option and the seal definitely isn't as good - the key is to not spin it any more than absolutely required.
For fasteners I make a little "snake" of tape (roll it in your fingers like when making pasta by hand) and then wrap that around the fastener head before I insert it in the hardware. Then I also put another roll around the fastener after inserting it through the hardware at the bottom of the hardware surface. Also put tape flat on the bottom of the hardware as continuously as possible but try not to build up to much thickness (not more than a layer or two of tape). Then install the hardware and all fasteners at once with the fasteners already sticking all the way out of the part you are installing. Make sure you don't let the fastener turn / only turn the nut when tightening! For the chain plates, likewise, make little rolls and jam them down around the chaine plates in the gap with the deck as far as you can with a little screwdriver, etc. Then keep building it up until you have a bead of bed-it that is maybe 3-5 mm or 1/4 inch proud of the deck around the chain plate. After installing the hardware and tightening you can trim off the excess easily with a sharp utility or exacto knife and roll it away. Cutting first is important since otherwise you can end up pulling the seal right back out again. When you tighten again the next day or next week or next season a little more will squeeze out and need to be trimmed again. A bit more effort than 3M products for sure but well worth it in the end.
As others suggested, a counter sink bit is perfect for the holes that screws and bolts go in. Don't be shy - you want a nice 3/16-1/4" counter sink here as long as there is sufficient material. If there isn't and or you are into the core, then the best thing is to drill out a much larger (e.g. 1/2 inch) hole through the top skin and core (don't worry if you go all the way through) - put some unthickened epoxy in and spread it around the surfaces of the core, then fill the hole with thickened epoxy. After the epoxy cures, drill the new hole for the fastener and counter sink the top of it before installing the hardware.
I suggest using a utility knife and or isolating multi-tool to cut a bevel relief around the chain plates. Also, as Jack said, correct any rotten core first if you can. Of course, simply resealing it will be an option for a little while but likely will not hold up as long and the core will need to be replaced eventually if it is rotten. I chose to put thickened epoxy around the chain plate instead of core material and replaced core with 1/2 inch G10 fiberglass boards where the tabs for the bulkheads come through when I did my refit in 2020 - see photos here: https://photos.app.goo.gl/8W4AdgmKqKxARvsY7 Unfortunately, I didn't get any photos of the actual process of sealing and installing the plates around the chain plates. Sorry! Nathan S/V Wisper Portland ME 1981 C&C 34 CB Any tricks with butyl tape I didn’t use bed it I sealed the screw hole with epoxy and butyl tape and still leaked I put 4200 instead it stop for a bit than it restarted again Does have a video how to do this properly
On Mon, Nov 10, 2025 at 11:02 PM John Christopher via CnC-List < [email protected]> wrote: You can use a chamfer drill bit. On Nov 10, 2025, at 10:15 PM, Janet Schilling via CnC-List <[email protected]> wrote:
Great advice gentlemen! Thank you. I ordered some Bed-it. To bevel under the chain plates what did you use? Some kind of wood rasp or file? Can I use one of my countersinks I use on wood to countersink the bolt or screw holes on the deck to rebed them with a little of the butyl tape?
Thanks again. Janet Sent from my iPhone Janet. Agree with Nathan's process. In my case tried various sealers without success mostly because would not stick to stainless chainplates. Over 10 years ago I pulled the chainplates, cleaned them, ensured no degraded balsa in deck or plywood, beveled the deck top side, installed chainplates, put in butyl so filled bevel and proud of deck, installed trim on top of butyl. No leaks since John Read Legacy Ill 1982 C&C 34 Noank, CT Janet,
I used bed-it butyl tape https://bed-it.com/ on my chain plates when I did a refit in 2000. So far no leaks! If your boat is set up like my 1981 C&C 34 it is best if you can remove the stays entirely so the plate comes all the way up. Should be able to use a halyard to the toe rail as a temporary stay. I cut a quarter inch angle into the fiberglass around the chain plate to ensure that the bed-it would have room to make a seal. Put a nice rolled bead in there and then put tape on the bottom of the plate before screwing it back down.
I generally use bed-it for everything above the waterline by the way. Seems to work pretty well even around self tapping screws and is much easier to both use and to replace than 3M products or other sealants. Does take a bit more time to seep out so you have to tighten screws progressively and cut away the excess a few times over successive weeks.
Nathan
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Nathan Post
+1 (781) 605-8671
On Mon, Nov 10, 2025 at 8:58 PM Janet Schilling via CnC-List < [email protected]> wrote: What kind of sealant/caulk is recommended? It was suggested that the horizontal deck plate could be unscrewed and lifted enough off the deck to add sealant of some kind underneath, then screw back down.
Thanks.
BTW, we removed the old caulk around all the port lites and redid with Dow 795 and tightened all the screws. It was a success! Not perfect, but no leaks.
Janet
Sent from my iPhone
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