Flanged seacock installation on the curve of the hull

[saurav16]

Hello I saw this page from a previous thread

Replacing Thru-Hulls and Seacocks Photo Gallery by Maine Sailing at pbase.com

But I was wondering how it would be possible to install a flanged seacock on the very curved portion of the bow? Worse yet the through hull nipple male portion comes into the boat at an angle. So it would make it very difficult to use a fiberglass backing plate. Any ideas?

[sailingdog]

You could build up a base of thickened epoxy and fiberglass for the flanged base, that was perpendicular to the through-hull.

Originally Posted by saurav16

Hello I saw this page from a previous thread

Replacing Thru-Hulls and Seacocks Photo Gallery by Maine Sailing at pbase.com

But I was wondering how it would be possible to install a flanged seacock on the very curved portion of the bow? Worse yet the through hull nipple male portion comes into the boat at an angle. So it would make it very difficult to use a fiberglass backing plate. Any ideas?

[sailaway21]

In implementing Dog's solution, here's what I'd recommend.

You want the outside of the thru-hull flush with the exterior of the hull so your adjustments for a square fit will necessarily be inside the hull. Laying up fiberglas and ending up with the correct angle is going to be difficult unless you lay up quite a thick structure and then sand to fit. That'd be a pain and any errors result in almost a complete do over. I'd get a plastic container, round might be nice but not essential, and make a hockey puck of epoxy and an additive like colloidal silica. Mix it fairly thick and let it cure in the container. Flip the container over and then tap it out of the container with light taps with a hammer. Then drill the hole size you need for the thru-hull. Slightly over-sized would be my inclination so that sealant will later be able to fill between the thru-hull and your new epoxy shim. Then take the shim and sand the angle you need to it on a bench sander. You can then attach it to the hull using either epoxy or the same sealant you're going to use for the thru-hull. If necessary, you can do the same as needed on the exterior.

This method will allow you to make all kinds of mistakes of little consequence until you get just the right fit. I mix my epoxy in the containers that Scotch 88 electrical tape comes in, I have a plethora of them from work, and one of them would probably make you just about the size hockey puck that you need. You'll only need a couple of rolls as you can reuse the containers-the dried epoxy will pop right out with a little flexing and tapping. And you can use the Scotch 88 elsewhere no doubt-it's the best electrical tape I've found-I use it under water on submersible well pumps.

I hope this will at least give you some ideas.

[Rockter]

What happens if the backing plate rots? What then? Will you see it if it does rot? What if you don't get the curvature just right?

The is nothing wrong with the first installation if the threads are compatible. The vast majority of sailboats have the first installation method.

There are two issues here. Security of the through-hull, and compatibility of the threads.

Am I missing something here?

[sailingdog]

I'd use a mixing bowl instead... the silicone mixing bowls that you can get at the home goods store come to mind as being particularly useful for this. They will leave you with a curved bottom and you can angle it and bed it much more easily than a hockey puck. Otherwise, sway's advice is pretty good and much what I would have said.

Rockter-

Fiberglass doesn't rot. If the curvature is off slightly, the sealant should make up the difference. However, the thread compatibility is a serious issue and you really do need to use a flange. The major difference is that most seacock valves are threaded for NPT, and the through-hulls are threaded for NPS. That means only a few threads will actually engage in the seacock, and that becomes a weakpoint before the valve, so if it fails, closing the valve does nothing.

[sailaway21]

Here's another idea I just thought of-it's an outgrowth of my dinghy building project. Mix the epoxy and additive up and then dump it into a zip-lock bag. Place the zip-lock bag inside the hull right in the area the thru-hull is to mount. Then compress it in position with a piece of flat steel or a small sheet of plywood at the appropriate angle from the back side. Let cure, remove, and sand where necessary. You might not get the back side quite perfect but you should have a real nice fit at the hull.

[sailingdog]

Not a bad idea...and a belt sander would fix the back side pretty quickly anyways.

Originally Posted by sailaway21

Here's another idea I just thought of-it's an outgrowth of my dinghy building project. Mix the epoxy and additive up and then dump it into a zip-lock bag. Place the zip-lock bag inside the hull right in the area the thru-hull is to mount. Then compress it in position with a piece of flat steel or a small sheet of plywood at the appropriate angle from the back side. Let cure, remove, and sand where necessary. You might not get the back side quite perfect but you should have a real nice fit at the hull.