OK what if the gasket had a nice coating of adhesive on both sides....sounds like butyl tape to me. :>)
If the stanchion base is through bolted with four bolts it should not be doing much moving. This is a very long cantilever beam and modelling it I would assume the deck is a rigid structure and the bending will be along the length of the cantilever beam. If the base is moving something is wrong with the installation. Also I'd suggest preventive maintenance, maybe rebed them every ten years as a good practice, but I still wouldn't rule out a gasket as an unacceptable means of sealing. All you are trying to seal is the screw holes anywayso the clamping force right at the screw hole would have to be almost completely loose for the gasket not to be compressed enough to seal. I guess you could build the same case for old sealant that is all hardened or exposed to the sun, I'm sure plenty of boats have wet core around stanchions that were from sealant leaks, it really comes down to inspections and preventive maintenance.
On my O'Day the bases have gaskets but the actual stanchions are separate pieces than mount in the bases and then have screws that hold them in. Keep in mind Pearson and O'Day were affiliated at one point in time. The bases are very rigid structures but I'll take your advice and start rebedding all of them, after 25 years I'm sure they're due for it. Very hard to get at the bolts :>(
Jibes,
Nearly every vessel I have seen that used gaskets for stanchion bases has seen leaks and wet decks. The problem is that the gasket thickness, on some Pearson's was that it was over 1/8" thick, which allows movement, and also over time compresses under the stanchion base thus allowing more movement. With a sealant or butyl the material is squished to a level so thin that movement is virtually non-existent and this is why a flexible sealant and counter sunk hole is a beneficial practice. The counter sunk hole creates gasket thickness, to allow for slight movement, without creating a flexible junction between the deck and the hardware. You can't do this even with a relatively hard gasket when you have a 24" lever connected to it and 200+ pound individuals grabbing it..
The toughest part for a gasket to seal is around the bolts and with the movement allowed by the thickness of the gasket this makes it even harder to seal this interface. Head gaskets on cars are not sealing bolt holes from the top down, they seal from the perimeter. On boats they need to seal from both top down and the perimeter.
Take a look at any hydronic boiler with an internal coil for domestic HW or a blank coil cover plate. There is no loading or strain applied to these coils yet these gaskets will always and eventually leak. I have tried every trick in the book to prevent it but it still happens.
The same problems are true for the "tighten twice" Don Casey method of allowing a "gasket" to form out of sealant before final tightening. This is and was perhaps the worst advice foisted upon unsuspecting DIY's and perhaps why we have hundreds of thousands of vessels with wet decks.
A dried Sika 291, 3M 4200, 5200, or.. gasp
, silicone, would be a much lower durometer rated hardness than a good quality neoprene gasket with a durometer rating of say 50D-60D. Even a 60D gasket will allow the stanchion base to move while also being sufficiently tight around the bolt holes. I can almost guarantee when I look at a boat with a Don Casey sealant gasket or a Pearson style gasket that when I put my meter to the deck it will be wet. Have I seen dry ones, yes plenty, but the failure rate is very, very high when compared to other methods..
Gaskets have proven over time to not be worthy when used to seal deck hardware. The "Pearson Problem" is widely know and understood. I have yet to see a reputable yard replace the gaskets after a 20k deck job with gaskets... I have seen my friends at the boat yard do many of these jobs, Pearson 303's, 31's, 36-2 and many others that used gaskets. The pictures below are from one they did a short time ago.
Reputable builders like Hinckley & Morris knew long ago that a slight countersink around the bolt hole stops deck leaks with a very high rate of success. Production builders, even to this day, are too damn lazy and cheap to take the extra 30 seconds to build and bed the boat correctly and this is why we have so many boats worth virtually nothing due to structurally compromised wet decks.
My 2005 C-310 had multiple deck leaks by the end of the 2005 season. She was completely re-bedded over that winter. Was the sealant bad, no, it was the installation and the lack of a countersunk hole that led to so many failures, over 5 leaks in less than one year from new. I actually re-bedded that boat using the countersink method, with 3M 101 and some butyl, and no more leaks.
Even this DIY band-aid of extra goop between the gasket and the hull and stanchion did not help. It still leaked and the deck was soaked!
This is a section of the deck taken from under the bow pulpit. The big hole was the core sample where they found nothing coffee ground like MUSH.
And the deck side. Note the rust right around the bolt holes and the rust under the entire gasket from the leak causing the bolts to rust.
Builders like this should be strung up by their toes.:cussing: These stanchion bases are a complete and utter joke. On top of the piss poor nature of this stanchion base the builder embeds aluminum than taps the stainless bolts into it. What happens when stainless and aluminum get wet with salt water? Yep they corrode and freeze solid, might as well be welded. Vessels like this will be MUCH harder to repair in the future because the stanchions go right into the toe rail with NO access for a nut on the inside. When the bolt breaks off due to leaking and corrosion between the stainless and aluminum the stanchion will need to be moved or an attempt at drilling the broken machine screw out of the toe rail will have to be successful. If they had at least countersunk around the bolt they MIGHT have enough elasticity to survive the piss poor construction of the stanchions that allows the movement. Even this marine sealant could not withstand the poor construction of the stanchion bases that lead to this much flexing. Every stanchion base on this boat was bent.
