Thread: Layered plywood boxes. Should I consider marine ply?

Jonesy, yes you can buy some crap ply from Bunnings, Marine ply from memory is more to do with the adhesive used ie waterproof. but in all honesty Bunnings is the last place i'd go for plywood, if you need to knock something up quickly ie board up a window or a door cavity, knock your socks off, but for quality I'd go to Mr Ply or a plywood sheet supplier similar to Bruynzeel in Brookvale, not sure whats down your way. These guys deal with all manner of ply from 2.7 through to 30mm beech and maybe higher.

Fumbler is spot on.

Can anyone suggest a business in Adelaide? I've come across quite a few old posts on various forums of South Australians struggling to find reputable ply.

Actually Marine grade ply is more about limiting the voids - exterior grade also has waterproof glue but can be full of interior gaps.
The big stores like Bunnings or Mitre 10 will order ply in for you if you can find a good source. The problem is that you don't see it until it is at the store, but it's still an option.
Southern timber and building supplies on O'Sullivan Beach road has some Hoop Marine and other grades.
You could also give Duck Flat Wooden Boats a ring and see what they have.

Originally Posted by Jonesy_SA

Hi

I'm considering building some small speaker boxes (less than 300mm square) out of layered ply. The plywood would be CNC cut and stuck together to form a box then sanded smooth and a finish applied to retain the natural look.
I.e.:
http://www.audiocircle.com/image.php?id=20231

I've read that standard plywood from Bunnings delaminates easy, has voids and that their marine ply is much better.

Is this true for all plywood or is theirs especially bad?

Use formply

My suggestion would be Baltic Birch. I've used a lot of the stuff and never encountered an interior void.

There's plywood and there's plywood.

Formply is an option but make sure it's structural grade formply.

Marine ply is more refering to the adhesive used and often has a hardwood for the outside plies.

Head to a dedicated timber yard/building supplies and they should be able to help you out.

Also keep an eye on the grading of the faces, usually expressed as two letters ie. "bd". It follows the same grading as dressed timber.

Yes, 'marine' ply is defined as limiting voids (good quality marine ply eliminates them) and having a blemish-free (knot free) outer surface as well as the waterproof/resistant adhesive. Definitely the way to go if using plywood. I dislike mdf but that seems to be the usual choice for speaker boxes. I have been told that it is better acoustically, but have never checked that - definitely no voids though!

I have purchased some good marine ply, with hardwood laminations, from Bunnings. Like every timber product (and maybe other products too) at Bunnings you need to carefully select from their stock. Some sheets of their marine ply have voids, others are void-free. Some will have cracks in the outer laminations, some will not. I'm sure that you get the idea. When you check the edges you get a very good idea of the quality. There is no guarantee there will not be voids inside but they will be limited in size and extent.

I have found that the other trick with Bunnings is to buy a bit extra - so you can use the dud bits for something less critical.

David

Re-reading the post I see you want an aesthetic and a certain performance, so yeah go for the birch

https://plyco.com.au/collections/quadro

Originally Posted by 44Ronin

Re-reading the post I see you want an aesthetic and a certain performance, so yeah go for the birch

https://plyco.com.au/collections/quadro

I'm told there is sonic differences between woods but I haven't read into it. It usually ends up an unqualified debate on audio forums.
I'm mainly thinking of using ply for the aesthetics. That is, to get all the layers visible on the sides of the box by creating slices from front to back. Effectively the only full face you would have is the front and rear.
A 1200 X 600 X 16mm birch ply on the linked site is $50 (without postage).
My main concern is pockets and delaminated areas. Is there a cheaper grade or is good ply simply expensive?

Originally Posted by Jonesy_SA

is good ply simply expensive?

Yes.

Marine ply and structural ply both have the same glue. The difference is in the veneers - Marine ply is made from marine borer resistant timber.

For indoor applications I think your fear of delamination is bordering upon paranoia.

Control the moisture and even on cheap plywood delamination is rare.

I think you will find that most discussion of delamination will be the boat and marine applications

Originally Posted by 44Ronin

For indoor applications I think your fear of delamination is bordering upon paranoia.

Control the moisture and even on cheap plywood delamination is rare.

I think you will find that most discussion of delamination will be the boat and marine applications

Perhaps wrong terminology. I went to Bunnings and found some of the ply was already seperating in sections as if never glued properly. Was concerned it might occur to other pieces.
It might be worth trying before purchasing expensive ply.

Birch looks much nicer on Google but haven't seen any in Adelaide to compare.