Porthole mirror as a functional port hole

I have this port hole brass mirror which needs a new mirror, broke decades ago.
It seems robust enough to me to use as a port hole. It also has a rubber seal ring.

I am planning to put a new mirror in this.
In the head, used to have a rectangular mirror, and the mirror desilverd. I am going to mount this there and maybe cut open a hole so it can function as a window. Would also put a screen in the opening. And I can seal the back of the mirror in a rubber goo. The head gets warm in the summer and would be nice to have an open window for air.

Now since the cabin side is 1" mahogany, I don't see why it wont work ok.
This will be up maybe 6 feet above the waterline and above the deck, so it wont have a lot of water hitting it. I was thinking, on the cut hole, seal the wood edge with some epoxy. I have no outer ring to use.

Do porthole mirrors all come with rubber seal rings?

Would you mount it so it opens up, or to the side? either way, will need something to hold it open.

Don't ports usually have a through hull spout?

Well, if you actually do make it so it operates as a opening port, how thick of a mirror glass can you fit in the port. If you're worried about breakage, you might want to look at acrylic or fiberglass mirror material. You'd still need to seal the silver behind it, but there's no danger of breakage and even at 1/4" thickness, is really strong. In that small of a square area, there shouldn't be any warp issues either. The material does scratch, but you could get a 12 X 12 or 12 X 24 sheet and cut a couple of extras for replacement. Another option might be to use 1/8" and back it with a layer of something else you'd rather have exposed outside. I used a full 4 X 8 sheet of 1/4" and cut myself a 36 X 80 wall mirror to replace a piece of damaged veneer in a busy companionway three years ago, no issues so far.

Acrylic mirror is available up to 24 X 48 through Amazon, by the way.

I'd suggest glazing it with black tempered or safety glass. Then glue the mirror to the inside surface of the glass. Other glazing materials would work as well: Alucobond, other black anodized aluminum, fiberglass painted black. Easy enough to make a bronze or painted fiberglass exterior trim ring; the harder part is making up the exterior metal/glass cylinder to extend between the exterior trim ring and the interior parts. You could make the exterior parts of Teak, painted or varnished; epoxy-coated cheaper stuff painted. Our bronze ports do not have drains.

This is now starting to sound like too much work. Buy a proper port and install it. Add the mirror.

I would use that on a coffee table, wall mount or bulkhead mount. It is certainly NOT a marine porthole. At least in so far as being watertight is concerned.

cappy208 said:

I would use that on a coffee table, wall mount or bulkhead mount. It is certainly NOT a marine porthole. At least in so far as being watertight is concerned.

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X2
It is a decorative piece and should be used as such. Proper ports have sealing flanges on the outside and sleeves through the hull. Nice looking piece, I just wouldn't make it functional IMHO.

New Found Metals, Inc.

Best on the market, Port Townsend.

I was planning on reinforcing the backside of the mirror, glue on maybe a piece of metal, I have 1/8 inch aluminum here, and coat over top with a polyurethane. The rubber gasket that cushions the glass is made to hold a 1/8 thick piece of glass, but you could go 1/4 and leave the rubber out. Those small screw holes, all it has is brass tabs. A circular piece of aluminum sheet I could cut and drill holes and screw it on, if that is worth doing, I do not know. Most likely just bond it on with a polyurethane.

This is up high on the hull, I just don't see how it could be a problem. If that seal leaks, I could do something to fix that.

About a trim ring on the outside, this is already attaching to 1" thick mahogany. Not that it needs a sandwich design like for a thin FG hull. The outer edge of the wood hole, I could grind a bevel around the lower edge so it would more easily drain water. Is that what the reference to a spout is about?

Ideally, you don't want water catching behind the door.

Draining is only part of the problem. Hull penetrations usually have something to protect the hole.
IMO if you want a port mirror buy a complete port and replace the glass.

Have a 0.080" aluminum plate bolted into the mirror frame on the backside.

The machine screws are #5-40 stainless. I will paint the aluminum plate white.

I used flat head screws and getting the aluminum plate countersunk to fit well to the screws was a pain. The countersink is dull and wanted to wander. I got the plate free at a sign shop. So far my total cost is $5 for the oddball screws. Mirror on other side was free at the glass shop.

$5 was for
25 #5-40 1/2" screws flat head SS, and
18 #4-40 1/2 inch round head SS and
18 $4-40 1/2 inch flat head SS and
1 socket head hardened 1" #5-40 bolt.
She gave me a goodly price. Bought these at York Bolt.

I used a dremel to create my own tap equivalent #5-40 since I had to reposition one screw hole and I had earlier tapped it to #4-40. So now all screws are #5-40 1/4 "long.

Nice work but just add salt water and that thing will disintegrate, especially if it is brass. The only place for brass on a boat is for decorative purposes (you have to keep it polished).

Best of luck to you.

Xsbank said:

Nice work but just add salt water and that thing will disintegrate, especially if it is brass. The only place for brass on a boat is for decorative purposes (you have to keep it polished).

Best of luck to you.

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I coated it with Aerospace 303 protectant. Plan to recoat every few months. I put that 303 on the finished transom wood and it is doing well.

This porthole mirror is not in an area that usually gets wet with the seas. It is above the hull side above the deck. Under the plat, i slathered on a layer of Loctite Black PL S30 polyurethane. The plate simply adds a little security to the mirror.

A man after my own predilections! Delightfully stubborn!

Still think you should have sprung for a real port. (Another of my predilections is, "Lazy is Good". That is, do however it is easiest to do something perfectly.