[waynek]

I am in the process of re-bedding my chainplate and I have a little unusual set up and am looking for some advice. Our deck plate is integrated into the chainplate and bolts to an interior bulkhead. The damage to the woodwork was noted in the pre-purchase survey but the listing broker may have exaggerated the level of work done to address.

The factory install was nylon washers around the 4 thru bolts to provide a 1/16th inch riser for a thicker mat of sealant (5200) with butyl on the bolts. The bolts did leak a little but the deck seal really failed, and water intruded down the plate and into/off the bulkhead regularly. There is about 1/8-1/4 of an inch of space between the outer diameter of the chainplate and the inner diameter of hole in the deck. (All residual 5200 will be removed to get surface pristine and as much as is possible in the thru-deck)

As I re-bed, I am reluctant to remove the washers because the bulkhead bolt/bolt holes will be off by 1/16th. I would like to use a mix of 3m 4000uv and bed-it butyl. I do want to increase the inner diameter of the washers to allow more butyl there, but use 4000 for the bulk of the sealant and butyl in critical locations.

My concern is that if the innermost area adjacent to the chainplate is thick butyl without any restrictions, will it creep in hot weather and fall into the interior making a big mess? the chainplate vertical edge to the edge of the flange is 3/4 inch at the narrowest spot.

thoughts or recommendations?
wayne

 

[capttb]

I don't think you need worry about the butyl getting soft enough to creep due to heat.
The washers were probably used in the theory they would prevent all the butyl getting squeezed out, most applications do not try to create that space but bed the whole surface area of the plate. Just a thought.

 

[Jeff_H]

There are several items to unwrap there, I have used Bed-it butyl and it does not seem to creep and run in warm weather, Maine Sail has published some excellent how-to's on his webpage and on SailNet that explain how to use butyl properly. I followed those when I rebed all of the hardware on my own boat. The broad generality in those tutorials suggest creating a bevel at the point where the bolts and the chainplates enter the deck. so there is a bigger volume and more contact area for the butyl. I found that a simple countersink drill bit quickly cuts that bevel.

I will note that I have similar chainplates to yours with the deck escutcheon plate welded to the chainplate. There is a lot of benefits and some liabilities to that approach. On one hand, the welded escutcheon prevents water from running down the chainplate straight into the joint between the chainplate and the deck. That is a big deal since that is where leaks are most likely to occur and are hardest to prevent. But welding risks weaking the chainplate at that critical point, and the welded escutcheon means that its very hard to rebed that fitting and you cannot use the escutcheon to compress the caulk. I have not decided whether I will keep the welded escutcheon if and when I replace my chainplates.

Looking at your chainplate design, I would suggest that you consider using a stainless steel washer rather than the nylon washers since the nylon washers allow more flexure and that takes a toll on the sealants. It is hard to tell what the deck layout is from the picture. It looks like the chainplate is in a slight detent. If so alternatively, I might consider building up the height of the deck with glass and resin at that point to the height of the washers and footprint of the chainplate so that the deck to escutcheon joint is raised above the deck surface and so not subjected to the water flowing across the deck. That is especially helpful in areas where freeze thaw cycles occur, and probably less critical in warmer climates.

Lastly, it does not sound like you are replacing the chainplate or escutcheon plate so this may not apply. Those chainplates have two offset bends in the metal. When you bend stainless steel, you potentially weaken it at the bends, That was probably considered during the engineering of those chainplates. But those bends potentially continue to weaken through fatigue over time due to flexure that results from the loads trying to straighten the chainplates under high loads and springing back when the loads are eased. If you replace those chainplates, I would consider either adding gussets that cross the bends to stiffen those spots or else adding a tightly fit, minimally compressible bearing block between the offset portion of the chainplate and the bulkhead to minimize flexure.

Those are only suggestions to consider, but otherwise your general plan (mixing butyl and another sealant) should work okay.

Jeff

 

[colemj]

What about milling a small shallow groove around both the escutcheon plate and deck boss? This groove would fill with sealant and provide a seal similar to an o-ring.

Mark

 

[waynek]

@Mark – I see your point about the groove but I don’t think that would have helped. The previous failure was in the metal to sealant bond. The sealant to gelcoat bond was 100%. The underside of the escutcheon stainless is not polished and I may scratch it up more to add surface for adhesion. I want to add butyl to the equation because it would protect against the sealant-metal bond failing again.

@Jeff – I have tried my best to take any and all Maine Sail advice whenever possible. I think I am deviating from his example in that I will need thicker sealant layer than his direct bedding onto the deck and that is what is giving me pause. The deck is built up so that the escutcheon plate is above grade (in second pic). It is also extended below deck (in pic 3 but less visibly). So the interior and exterior faces are parallel and 2 inches of solid fiberglass (no core to worry about). I do not intend to replace the chainplates and what may appear to be a bend in the first pic is a flair in the shape as it approaches the escutcheon plate and an unpolished section (if I am interpreting your comment correctly). I had considered metal washers but discounted as I was afraid of galvanic interactions, but you bring up a worthy point.

 

[Skipper Jer]

I wonder when these chain plates were installed last time if the sealant was allowed to cure before the bolts were torqued to the final position.

 

[danvon]

I use MaineSail's butyl - it creeps a little but I cant see it being enough to get all the way down to the inside.

 

[Quickstep192]

I think I’d use bed-it or 4000, but not both.

If it t’were me, I think I’d glue plugs into the holes in the bulkhead and re-drill so they align with the chainplate holes when the deck plate is pulled tight to the deck. Then bevel the holes and use bed-it between the plate and the deck.

Another option might be a 1/16” plate of stainless or Garolite that could be well bedded in bed-it. You could also build up the deck by 1/16” but that sounds like a lot of work.

Otherwise, I think I’d stick with the original design, using 4000 or Life Caulk and use larger washers so the holes can be beveled.

 

[eherlihy]

Pot all the holes (including the chainplate hole), re-drill/re-cut the holes through the deck, chamfer the edges, cut a piece of 1/16" G-10 to fit the underside of the chainplate and evenly spread any point load on the deck, then bed the chainplate and both sides of the G-10 plate in butyl.