Which sealant?

[SVJOCO]

Hello,

I’m looking for specific product recommendations for sealing around the base of this plate.

Thank you,

Jeff

[Spot]

Is that a mast step? Are you going to be able to take the weight off it and raise it up and clean underneath it before adding the sealant? I would not recommend a silicone goober around the edges with it still in place. Perhaps butyl mastic or something with a little flex. Probably not 5200 either.

[tkeithlu]

3M 5200 would preclude disassembly later.

If you use silicone, get the "30 year" stuff - it has less water in it and shrinks less.

Can you get a spatula blade under the plate? If so, the first task is getting the sand out of the gap. The second task is getting the goo into the crack. As Spot points out, a superficial application of goo will soon peal off. Your goal is to fill that gap, with the goo sandwiched between the two surfaces.

[Thumbs Up]

If you are just trying to place a bead around it (not under it) 5200 is actually not a bad choice (you can knife it off in the future). Are you rebedding this fitting or just trying to keep dirty water from seeping out onto the deck? If it is the latter, you might want to think about where this water would end up if you seal it. Into the deck core? Careful...

[Oldwheels]

The 3m 4200 will allow disassembly and has a quicker cure time. 5200 can be disassembled with difficulty.
In my opinion these two sealants are best on the market with least hype and great tech support. They will answer your question.
Every thing else is a compromise or gamble.

[pcmm]

If it's leaking through the bolts, Then the real fix is to remove the step and check for any real water damage. If you've dodged the bullet I would overdrill the holes, fill with epoxy and redrill to the correct size. Add a bit of a chamfer to the hole so that you can get sealant to form a good seal.

there is no reason at all to use an adhesive type sealant here. Nothing will seal better than good quality butyl. but sikaflex will work well here to. 4200 works well

DO NOT use 5200.

[SVJOCO]

Originally Posted by Spot

Is that a mast step? Are you going to be able to take the weight off it and raise it up and clean underneath it before adding the sealant? I would not recommend a silicone goober around the edges with it still in place. Perhaps butyl mastic or something with a little flex. Probably not 5200 either.

Yes, it is a mast step. I am not going to take the weight off of the mast step because the boat was recently re-rigged. Thanks for reply.

[SVJOCO]

Originally Posted by tkeithlu

3M 5200 would preclude disassembly later.

If you use silicone, get the "30 year" stuff - it has less water in it and shrinks less.

Can you get a spatula blade under the plate? If so, the first task is getting the sand out of the gap. The second task is getting the goo into the crack. As Spot points out, a superficial application of goo will soon peal off. Your goal is to fill that gap, with the goo sandwiched between the two surfaces.

The gap varies around the edges from spatula sized to almost nothing. I can thus likely clean some portion but not others. Thanks for the reply.

[SVJOCO]

Originally Posted by pcmm

If it's leaking through the bolts, Then the real fix is to remove the step and check for any real water damage. If you've dodged the bullet I would overdrill the holes, fill with epoxy and redrill to the correct size. Add a bit of a chamfer to the hole so that you can get sealant to form a good seal.

there is no reason at all to use an adhesive type sealant here. Nothing will seal better than good quality butyl. but sikaflex will work well here to. 4200 works well

DO NOT use 5200.

There aren’t any leaks that I’m aware of, but if I was taking up this plate I would do as you describe. Hallberg-rassy may have done that at install time too, I have no idea. It’s an HR352 with Selden mast.

Any water finding its way to this gap is coming from above in/on the mast, on to this step, and then out to the side edges.

Thanks for the reply.

[Thumbs Up]

Originally Posted by SVJOCO

There aren’t any leaks that I’m aware of, but if I was taking up this plate I would do as you describe. Hallberg-rassy may have done that at install time too, I have no idea. It’s an HR352 with Selden mast.

Any water finding its way to this gap is coming from above in/on the mast, on to this step, and then out to the side edges.

Thanks for the reply.

If you seal it, leave a weep hole.

[tkeithlu]

OK, you're not going to lift the mast. You can pull the bolts and rebed them in 3M4200. You can also force 4200 into the crack with a putty knife. Put a bead beside the crack and hold the knife vertically, pushing goo into the crack by moving the knife sideways. That should do it.

BTW, toss your partial tube of 4200/5200 into the freezer. I'm using a tube at present that is more than two years old. It only takes a few minutes to thaw it out when you next need some. That stuff is expensive.

[team karst]

My aluminum deck mast plate has slots on all 4 sides. For drying i guess. I see zero reason to seal a plate to the deck, but huge reason to seal the screw holes in coring.

[Bowdrie]

Originally Posted by team karst

My aluminum deck mast plate has slots on all 4 sides. For drying i guess. I see zero reason to seal a plate to the deck, but huge reason to seal the screw holes in coring.

Yes, and those "pockets" in the OPs pic that the flat-head machine screws are in are just perfect places to hold water that will eventually weep down into the deck unless properly sealed.
Putting a bead of something around the perimeter of the plate?
That's a good way to just trap any moisture/water that works its way down the fasteners.
With the rig on it's too late for the step plate, now just make sure the bolts are sealed, you can take them out one at a time to do that.
If you have to "beat" the bolts in or out the holes are too tight and have no room for sealant.
Polysulfide is a good choice, better than 4200/5200.

[team karst]

I would tend to think (or hope) that this load bearing member would not be cored in this area. But in any case, something below prolly doesn’t want to get wet.
And, doesnt the mast itself need a way to drain??

[Cheechako]

Disassemble and clean.
Use any good quality sealant, 5200, 4200, Boat Life, Sikaflex.
(5200 being semi-permanent but rarely fails. It can be removed with heat or a knife.)

When reassembling, tighten the bolts lightly by hand.
Let the sealant set up for a few hours or overnight, then snug up the bolts.