All the stanchions need re-bedding as some are leaking or loose or both! they are mounted on 3/4 inch hardwood pads, then bolted thru the deck, presume teak but could be iroko. I'm replacing these pads, probably a silly question but, i'm replacing with iroko so do I need to coat it in anything or does it just fit under the base as is? the reason I ask is if I teak oil them the sealant will not bond with them, funnily enough I have the same dilemma with blakes Seacocks, they state they should be mounted on a wooden pad, (I dont understand why) but i'm wondering wether these need coating too? If they do require coating any ideas what would be the best, cheers Max
Caveat: I'm no expert. And I'm stumped on the deck hardware. If you don't seal the wood in something it will rot away. ?!?!
However, the wood pads for seacocks are shaped on the bottom to conform to hull, the top is a flat surface for the seacock to 'seat' on.
I would seal all pads. IMHO, the sealant is not bonding as much as it is 'sealing' to prevent leaks. It seems to me that 'bonding' is not the issue/purpose.
FWIW, and my advice is worth what you paid for it :)... Mainesail has an excellent discussion and how to on installing seacocks. In a nutshell though he recommends against using a wood plate backer for through hulls. It's not if they're going to get wet and deteriorate, but when. As for the stanchions, I agree with sailorbum. What I'd do, but I don't like varnishing etc. is maybe consider either eliminating the pads, or making new ones out of starboard. When you bed the plates, make sure you chamfer (sp) the hole just a bid so when you bed the plates, a bit of sealant forms a gasket in the chamferd part to keep out water intrusion.
I wouldn't recommend using starboard, as it can split under pressure and isn't really designed for use as a structural material. Wood should be at least sealed with a coating of epoxy and then varnished or painted to protect the epoxy.
If you don't want to use wood, go with a fiberglass base and backing plate. Fiberglass backing plates should be bedded in thickened epoxy to allow them to sit firmly against the hull with no voids.
Maine Sail's article on bedding through-hulls is an excellent one.
As for sealants to use, I'd recommend using butyl tape for the sealant. It really is one of the best sealants to use for any hardware on a boat that is through-bolted.
I second, or third, the recommendation of Maine Sail's articles. I couldn't think of who it was and a quick google from out here on the road wasn't fruitful.
Here is the seacock article:
http://www.pbase.com/mainecruising/replacing_thruhulls (http://www.pbase.com/mainecruising/replacing_thruhulls)
Here is the index page for all his articles:
http://www.pbase.com/mainecruising/boat_projects (http://www.pbase.com/mainecruising/boat_projects)
What kind of caulk/sealant would you use on something like a hatch hinge?
I generally recommend butyl tape as the proper sealant for all deck hardware that is through-bolted, unless it will be exposed to fuel on a regular basis... since butyl rubber tape dissolves in gasoline and diesel. For those, a polyurethane or polysulfide is usually a better choice.
I don't think silicone sealants have much real utility on a boat. Their use can often contaminate the fiberglass with residual silicone and make it almost impossible for getting later sealants to stick properly. Other than bedding ports with a structural silicone like Dow Corning 795, the only real use for silicone is covering the ends of cotter pins.
I'd also point out that 3M 5200 also has very little real use on a boat. The hull-keel join and the hull-deck join are the two main ones.
Quote from: AdriftAtSea on May 10, 2010, 10:03:44 PM....I don't think silicone sealants have much real utility on a boat. Their use can often contaminate the fiberglass with residual silicone and make it almost impossible for getting later sealants to stick properly....
Yup.
Take a look at this thread (http://sailfar.net/forum/index.php/topic,85.0.html) for more discussion of the evils of silicone and the merits of real sealants.