Plywood sink. Sealing the corners

hoffy · May 15, 2017

This may seem like a daft question, but what would I use to seal the corners of a plywood sink, where the different pieces of plywood meet ( the pieces are being held together with screws and construction adhesive)? Something as simple as roof silicone? Or do I slop in a whole bunch of epoxy when I coat the ply?

If I do use silicone, do I seal the corners before or after I coat?

Cheers.

removed account4 · May 15, 2017

hey hoffy ..

i had a plywood sink years ago and the way i sealed it
was with fiberglass cloth and epoxy. especially the corners. the sink
was probably 25 years by the time i rented the studio and i had to repair it
every year or 2 ... i wish i still had a plywood sink ! they are the best.
i'm currently using a plastic sink, real piece of junk, but the price was right ...

AgX · May 15, 2017

I guess you mean edges.

If you use silicone rubber, forget about any successive coating. The transient between coating and rubber at the plywood will not stay tight.

So, coat the plywood before the assembly or use a coating that will remain flexible enough to withstand any wobbling of the boards or even them varying in dimension.

Wayne · May 15, 2017

I used some sort of caulk but don't remember exactly what (its been 20 years and has never leaked) and painted the whole thing in swimming pool paint.

AgX · May 15, 2017

Even if you use a caulk that would allow successive coating, technically seen pre-coating the boards would still be the better option.

Kino · May 15, 2017

I just used a good grade of carpenter's glue and then put about 5 coats of epoxy paint on the sink. You might have to touch up the paint every 2 or 3 years, but it's held-up remarkably well...

mike c · May 15, 2017

I used small quarter round wood doling glued in with fiberglass resin and nails .

AgX · May 15, 2017

What would be their effect sealing-wise? You substitute one 90° edge by two 90° edges.

jeffreyg · May 15, 2017

Check with products available in a marine supply company. I made a fiberglass re-enforced polyester coated plywood darkroom sink forty-one years ago and used a putty material that may also be available in auto supply shops. The sink is still in use and has never leaked.

http://www.jeffreyglasser.com/

adelorenzo · May 15, 2017

I used 3M Premium Marine Filler in the joints. Once it had cured I painted the sink with a couple of coats of boat paint.

AgX · May 15, 2017

If one decides to build a wooden sink anyway, the step to build it as a negative used as form for fiber-reinforced-resin is not that big.

Doremus Scudder · May 15, 2017

I used MarineTex (or a similar epoxy-putty product, not sure which) to fair the inside corners, then sanded and painted with marine paint. My old sink lasted for years and years, so I've just made a new one with the same materials.

Best,

Doremus

Bob Carnie · May 15, 2017

West Systems can be found at a boat store or google them I have used this stuff for all my sinks.

Jim Noel · May 15, 2017

A strong second for West Systems epoxy. I built my sink in 1989, and it is still waterproof.

mike c · May 15, 2017

AgX said:
What would be their effect sealing-wise? You substitute one 90° edge by two 90° edges.

Yes there are 2 90 deg angles there but with the resin filler between the quarter round and the side and bottom there is a stronger and better seal, it also helps with keeping the corners eraser too clean. West Systems also make a thicker epoxy made for sealing those joints really easier and better than the quarter round or any other joint compound and is compatible with the final epoxy coating, I have used this also and it works great, a little expensive but saves a lot of time and work.

AgX · May 15, 2017

So, is there any benefit by using fiber-reinforced-resin?

At least you could make the the nicest edges you can imagine.

Rick A · May 15, 2017

Have you already assembled it? If not, the time to seal is during construction. I recommend Gorilla Glue Polyurethane adhesive, it is water activated, and foams when curing sealing joints. It's totally waterproof on drying, any excess can be sliced away with a sharp knife or chisel. After that, it can be painted with any good quality enamel porch paint.

Hilo · May 15, 2017

I used a two components epoxy glue while assembling, a two component epoxy filler to make disappear the screws, and two components epoxy ground and final coats.

A carpenter friend helped me put it together. The smartest thing he came up with was about something in the construction inside the sink where bottom and sides meet: we bought square beams of 4 to 5 cm (1.5 to 1.9) with the same lengths as the two long and the two short sides. He sawed those the whole length from corner to corner, creating triangular beams. Those we glewed and screwed into the corners using the same materials as mentioned before. Sorry, English is not my language !

This sink I had for about 25 years, printing almost daily throughout the years . . .

wiltw · May 15, 2017

Yet another vote for West Systems epoxy, available from marine supply stores.

paul ron · May 15, 2017

BTW the best and most stable plywood for this project would be MDO. Its a waterproof to begin with, resin bonded, and very dimensionally stable. It holds dry wall hi lo screws very well.

https://www.hunker.com/12316947/what-is-mdo-plywood

.

hoffy · May 15, 2017

Thanks for the replies folks.

What I have taken away from these responses is that there is no one answer!

The sink I am making is rather small (1200mm x 600mm) and is to be removed from the darkroom (laundry) after every printing session.

In regards to the West system, I am actually not sure how readily available it is for me. I know a local paint supplier sells their own epoxy range for wood boat builders, so I was going to try with that first. I probably should ask them what their recommendations are for sealing the corners.

Cheers

AgX · May 15, 2017

I never heard of the term MDO. If it is what I think of, then only the surfaces of the planes are waterproof, not the cut edges.

Oxleyroad · May 15, 2017

Hoffy, I'd go with what ever two part marine epoxy your boat builder recomends. I know the West Systems epoxy is available in WA but I have no idea about the rest of Oz. The freight to SA may make it rediculously expensive.

I've made a few items out of wood and sealed with fibre glass and resin for the dark room. Can't remember the brand I used in Melbourne but I got it from a boat building supplies shop.

Oxleyroad · May 15, 2017

MDO (meduim density overlay) is a plywood. Not to be confused with MDF (medium density fibreboard). MDO is not used in construction or roads in Oz and to the best of my knowledge not available.

Large road signs over the freeway here in the US seem to frequently be made of this material whereas in Oz the huge signs are all Aluminium.

hoffy · May 15, 2017

Cheers Andy! How's life treating you in MI?

I am just using standard garden variety Ply. When I spoke to the timber supplier, they suggested that regardless of what I buy, I would have to coat it properly anyway (Marine grade Ply is not necessarily waterproof....). I should also add that in general, I would not be running a lot of water through it anyway (laundry tub is available for washing), but I thought I might as well build it with the ability to do so. I also want to be able to contain spills, which my current setup doesn't allow.

Plywood sink. Sealing the corners

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