Bedding stanchions

[JetStream]

My 1989 Pearson was supplied with stanchions that used a 1/8" thick rubber (or plastic?) pad of probably 70-80 durometer, mounted between the stanchion and the deck. On the underside, they used a fiberglass backing plate, washers, lockwashers and nuts. Over the course of time, every stanchion became loose (before I owned the boat) and leaked through the deck. My question is this: Does anyone think these rubber backing pads are a good idea? I would prefer to just mount the stanchions straight to the deck, using bedding compound and no rubber. Then on the bottom, I'll still use the backers and washers, but use nylock nuts to prevent loosening. I already overdrilled the holes and epoxied them so I could drill new smaller holes and get the fasteners to seal better. Fortunately, the stanchions were installed over non-cored areas of the deck, so wet core from the leaks does not appear to be a problem.

[Tallystick]

I just attached all my stanchions last week. Don't really see an advantage to the rubber pads. Bedding compound (polysulfide) is a type of rubber and it should help distribute the load. I tapped the holes in the deck for the machine screws, and used plywood backer plates and tightened the machine screws sufficiently to begin to deform the plywood. Use a #7 drill and a tapered tap. Doesn't really take much extra time. I think that will provide some spring similar to the way lockwasher work to press against the nuts. Also had polysulfide on the threads which should hold the nuts in place. You could also use jam nuts. I think jam nuts would be better than nylon lock nuts. Just use screws that are long enough that you can use two nuts. Jam nuts are thinner so use those if you don't have much space.

[triton318]

Check this out: http://www.pbase.com/mainecruising/rebedding_hardware. I'm reinstalling deck hardware on my Pearson Triton and am using butyl tape. So far I can say that while it is a bit more labor intensive, it's much nicer than working with a polysulfide sealant. I guess only time will tell if it results in as good a seal as he claims. But...everything he says makes sense to me.

[Tallystick]

Cleanup of difficulty of polysulfide might vary depending on the deck paint, not sure on that one. I've found it easy to cleanup when uncured using a nylon bristle brush dipped in mineral spirits. That takes away the stickiness of the polysulfide, and allows the loose material to be wiped up with a rag, or vacuumed. Vacuum works best on non-slip surface. A bamboo skewer like they sell at the grocery store for kabobs works well for removing cured material without scratching the deck.

[mitiempo]

Rubber pads should not be used - never should have really. Butyl or another good bedding compound is the best choice. When hardware moves, and stanchions move more than most hardware, the sealant should stretch and follow, maintaining a seal. Rubber pads just let water in.

[CharlieJ]

A really neat way of removing caulk, excess epoxy,etc, is a plastic soda straw. One of the large ones from DQ works really well. Just push it into the corner, it forms itself to the shape, and push it along. Scoops the excess up into the straw. Later, you can just clip off the part with the "stuff" and have the rest left for next time.

[Carl-A259]

With my very limited experience, I think plywood is a very poor choice for backing plates for anything. Other than being cheap and easy to make there is no other benefit. I bought some 1/4" fiberglass flat stock from McMaster Carr and plan on using that. It won't compress or rot like plywood will. You can also tighten a fastener with out compressing the backing plate and actually get it tight. Butyl tape is what I'm using for a sealer. Cheers!

[Tallystick]

Carl you bring up an interesting point. I agree with the concern of plywood rotting, although with epoxy sealed marine plywood and properly bedded hardware I think that is easily mitigated. On the structural aspect, that is something I thought about considerably, and had a difficult time selecting the material. I had considered fiberglass plate, stainless plate, and plywood. I ultimately settled on plywood thinking that the purpose of the backing plate is to spread the load on the deck, but that the backing plate shouldn't be stronger than the deck itself so that the backing plate yields when hardware experiences excessive strain, providing energy dissipation, before the deck is damaged. That was my thought process anyways, would be interested in hearing others experiences.

[danielguiod]

I am in the process of rebedding everything on HOKAHEY with butyl tape. For backing plates the best material are the shims used in heavy construction to shim up precast concrete. They are plastic/ nylon and come in thicknesses up to 3/4". They are easily machined and cut and are indestructible. On large jobs they are tossed out by the boxload if unused at the end of the job.

[mitiempo]

In my opinion the best solution is backing plates made of fiberglass offcuts or G10 epoxied to the deck. They should be larger than the stanchion base and tapered to a lesser thickness at the edges to avoid point loading. This not only spreads the load but strengthens the deck. They are also not compressible.

Second choice would be either stainless or aluminum plates also larger than the stanchion base.

[Zach]

I make a sandwich of plywood and aluminum and tap the holes for the hardware to bolt on.

It's extra handy for places you can't get to hold the backing plate in place. I've installed backing plates this way 4+ feet past where a human can crawl with a stick with a rag taped to it covered in acetone, a stick with sandpaper... and a stick with backing plate slathered in epoxy, duct taped to it Hold it in place and have someone run a screw through the deck to catch the plywood.

I like to use 5200 to glue a piece of aluminum to a piece of 3/4 marine plywood, then epoxying the plywood to the underside of the deck. A skill saw will cut the sandwich to size.

Once it has kicked, you can then drill a hole through the deck, and through the aluminum of the proper tap size for the fastener required.

Then I take an oversized drill, and overbore the deck and plywood for epoxy. Clean out the chips, and then tap the aluminum plate.

Install the bolts dry with the hardware and make sure it fits. Then take it loose. Fill the hole with epoxy, and turn the fastener into the thickened epoxy making sure there are no voids. Let it kick, back out the screws (May need a torch, or a soldering iron to release them.) sand, and install the hardware with butyl rudder or dolphinite... or 5200 for cleats and such.

I use a larger drill bit to make a chamfer around the hole so that an "o-ring" seal of sealant is made once the hardware is in place.

Then you can add nuts and washers to the underside if you so desire... I use 3/8ths or thicker aluminum so you get a good thread.

Don't use nylon, as a spacer as it absorbs water. Lots of steel boats try to use it for electrolysis protection and end up fubar'd, but its not that great at keeping a good seal or keeping crevice corrosion from happening on the underside of the stainless hardware.