How to seal a 1/2" bronze bolt and washer through a hull below the WL?

[endoftheroad]

I need to install a 1/2" bronze bolt and washer through my hull below the waterline.
I'd rather not explain why as my intended use for the bolt is a topic with many opinions.
Where would I use the Sikiflex and should I use some sort of backing plate?
Or is a large bronze washer on each side of the hull sufficient (and 2 nuts on the inside)?
Thanks

[sailvayu]

Use a counter sink to bevel the edge of the hole and use a O ring with some polysulfide sealant. I won't ask why lol.

[roverhi]

Polysulfide like Lifecaulk and polyurethane like 4200/5200 both actually require water to cure so will work fine if you are doing this in the water. Out of the water that get the moisture needed for cure from the air. Don't know what you are using this for but a flat washer on each side and a lock washer and nut on the inside should do the trick. A countersunk hole would be cleaner on the outside and should be fine but a little difficult to do in the water. The sealant alone would probably hold the bolt in place after it's cured all by itself.

[endoftheroad]

Yes, I'm in the boatyard now.
It was the countersinking that I was missing.
I'm happy I asked here. And I wasn't sure if a large washer was good enough backing. I'll use a 1/2"id washer with a larger than normal outer dimension, closer to a fender washer (bronze on both sides of the hull). I'll be sure to use a lock washer and 2 nuts.
Thanks.

[endoftheroad]

Roverhi,
What did you do for lightning protection with your Westsail 32?

I bought my W32 two years ago, the boat was grounded solely to a Dynaplate with heavy cables from the chainplates.
I removed the Dynaplate at this haulout, filled the 1/4" holes and am considering installing this 1/2" bronze bolt for attaching the cables that are lying in the bilge near the mast compression block where the Dynaplate was located.

I'd rather not make this thread into a lightning protection debate but I can't see why the lightning wouldn't find it's way to the water jumping the 3 or 4 inches from the bobstay fitting?????

Okay....now everyone knows...

[FlyingCloud1937]

I for one, want to know what you think you are doing?

Countersinking and 2 fender washers, one on each side makes no sense.

Drilling a countersink in a washer is completely suspect.

How thick is your hull?

Is it wood, or cored?

Do pray-tell.

Lloyd

Originally Posted by endoftheroad

Yes, I'm in the boatyard now.
It was the countersinking that I was missing.
I'm happy I asked here. And I wasn't sure if a large washer was good enough backing. I'll use a 1/2"id washer with a larger than normal outer dimension, closer to a fender washer (bronze on both sides of the hull). I'll be sure to use a lock washer and 2 nuts.
Thanks.

[FlyingCloud1937]

Or just blow a hole in the bottom of your boat about 3 X's the size:bangh ead:

Originally Posted by endoftheroad

Roverhi,
What did you do for lightning protection with your Westsail 32?

I bought my W32 two years ago, the boat was grounded solely to a Dynaplate with heavy cables from the chainplates.
I removed the Dynaplate at this haulout, filled the 1/4" holes and am considering installing this 1/2" bronze bolt for attaching the cables that are lying in the bilge near the mast compression block where the Dynaplate was located.

I'd rather not make this thread into a lightning protection debate but I can't see why the lightning wouldn't find it's way to the water jumping the 3 or 4 inches from the bobstay fitting?????

Okay....now everyone knows...

[minaret]

Doesn't your boat have external chain plates? You just make up a length of battery cable which you can clip to the lee shrouds dragging in the water whenever there is lightning about. This way the charge is theoretically routed over the side instead of through the boat right past all the electronics and through the hull. It's the simple solution. Be sure to make it long enough to reach the water when on the hook.

[roverhi]

I'd be leary about running a lightning ground to a single bolt. Lightning has a habit of blowing large holes in things when it's concentrated.

I just had jumper cables and a largish zinc that I intended to use when lightning was about. Fortunately, never ran into any lightning. The jumper cables eventually ended up in my truck when we got back after living in a locker for our entire cruise. Probably a bit more chance of encountering lightning in the Gulf and Atlantic off Fla.

You don't need washer on the outside if you countersink the bolt. Assuming you are talking a flat head fastener. The hull will probably be 1/2" plus thick once you get much below the water line. Westsail used the same layup schedule for the 42 as they did for the 32.

[endoftheroad]

I have decided against using the bolt.
Thanks as I'm on the hard and needed to resolve this issue.