Deck hardware screw sealer ?

Hello. New to posting. I'm installing a stern pulpt, stancheons, cleats, etc., on my sailboat. The silicon sealing and bedding of the hardware itself seems straight forward, but the actual sealing of the screws and through holes doesn't sound so easy. I've been looking for some "industry standard" techniques for this proceedure. It seems that if you drilled the screw holes oversized that you would be able to apply enough sealant between the hull and screws to pruduce a good seal. Of course this would compromise the secruity of the hardware. There is just no way to apply sealer (even if only between the threads) to the screw itself to keep water from wicking down (through caplary action) inbetween the fastener and the raw fiberglass cross section of the hull. When I wash my deck or even just morning dew, the water will; even if only slightly, drip into the cabin. Is it uncommon to place a washer (of maybe the grainy composite type) under each fastener to provide a gasket type surface? I'd like to store my sails and equipment inside the cabin but I don't want everything to stay wet constantly.

 

You have to use epoxy first instead of sealant. That means drilling oversize, filling that hole with epoxy, and then redrilling the fastener hole, creating a donut shape. If you want to hide the epoxy ring you can enlarge the original hole only in the core itself using a bent nail on the end of a drill.
Once the jacketed holes are ready use sealant like #5200 to seal the fasteners and the hardware's undetrside. It is sometimes recommended that the sealant is first compressed lightly, allowed to cure, and then compressed (like a rubber gasket would be) with a final tightening.

 

Hi Jimmy, also do a small countersink in the deck to the fastening holes under where the fitting goes, this allows a small grommet of sealant to surround the fastening & this will seal better. Regards from Jeff

 

Thanks for your replies guys. I assume that the epoxy core or donut teqnique provides a more uniform and mechanically tighter mating surface between the fastener and hull (instead of just drilled fiberglass). I also like the idea of a small chamfer or countersink to provide more of a sealing surface.

 

Wait! Don't use 5200 unless you never want it off again. And if a 5200 screw begins to leak its next to impossible to fix. Instead use 4200 or 4000. Both work great as sealers and you can take the bolts/equipment out/off later if you want.

-jim lee

 

The epoxy 'plug' surrounding the fastener hole serves to reinforce the laminate against the compression from the fastener, as well as keeping water from migrating into the core. (If that happens, things get very, very bad.)

3M 5200 sticks like the devil; use it for things you'll never need to remove. (Some people have reported removing their keel bolts during repairs on the hard, and having several tonnes of lead keel stay attached by 5200 alone until it's cut off.) The less aggressive, but equally waterproof, 3M 4200 is often a better choice for bedding hardware. (If you're a traditionalist, you can always use something like Dolphinite, or if you're really cheap, you might try roofing tar- which can get messy.) Skip the silicones; these are by far the best for glass, concrete and other landlubber building materials, but unless you know exactly the combination of mechanical and chemical properties you need, you'll probably end up with the wrong one if you try to use them for a boat. I'm not aware of any "indoor" sealants, or any acrylic or latex ones, that work in the marine environment. 3M 4200/5200 are designed specifically for bedding and sealing stuff aboard ship.

The sealant should never be forced too far down the fastener hole, and the underside of the fastener should never be sealed- only the top. This way, if it ever does start to leak, you'll see the drips and know it's time to fix it- instead of having that water pool in there, silently corroding your bolt away, until one day you go to lean on the stanchion and the bolts break.

 

Thanks for the correction. I should have said #4200.