Laminating cabinets

[Cal Weldon]

I wish to make a compound curved cabinet and would like to do it by stacking cutouts. I had planned on using 3/4" (19mm) spruce plywood. Plywood because I like working with it better than mdf and it puts up with our climate better.

I would like to know what your thoughts are about using a combo of ply and mdf. I will need to stack about 11 pieces. Is there an advantage to inter-plying the two?

The cost per sheet is the same.

[pinkmouse]

I'd stick with ply. Depending on how it comes out and the quality of the wood, you could just oil or wax it for a really funky finish.

[bostonswoop]

my experiance with plywood is it isnt as dense as MDF and chips alot easier. mostly because of the way its glued together. So to me it is not as user friendly.
Most of my experinace tho has been with furniture making so that material just makes up Expense and grain and coloring and durability.... so once again what do i know....

[Taperwood]

Cal,

You probably know that the quality of MDF-priced plywood is not very high. You will have lots of voids, cracks, knots, etc. This is very hard to shape without tearing out big chunks. Soundwise, I would choose plywood, but I think at that quality level, it will be more work.

Re climate, it can't be that much wetter where you live than me?

Doug

[AudialDelta]

If you use plywood for enclosures, use only certified void free. Baltic Birch and marine grade are both available in a void free variety.

Most upper end speakers that use wood as an enclosure material laminate Baltic Birch (BB) on the exterior and MDF on the interior. The greater density of MDF lowers cabinet resonance frequency. The stiffness of BB yeilds a higher enclosure resonant frequency. MDF will hold on to acoustical energy longer than BB. It is a balancing act.

Why do you need to stack so many pieces? If you have a complex curve it would be more sensable to use thin material. Once it is curved, braced & secured it will be significantly stronger than a flat piece of equal thickness.

- James

[Cal Weldon]

Thanks for the answers so far. I am thinking it might be best to stick with the ply throughout. I have changed from a compound curve to an "double S" shape

Originally posted by Taperwood
You probably know that the quality of MDF-priced plywood is not very high. You will have lots of voids, cracks, knots, etc. This is very hard to shape without tearing out big chunks. Soundwise, I would choose plywood, but I think at that quality level, it will be more work.

Doug,
I am cutting out pieces approximately 1 1/2" wide in the shape of the cabinet. All voids can be filled once assembled.

As far as shaping, I'm not, I'm stacking cutouts.

[i]Re climate, it can't be that much wetter where you live than me?[/B]

You're right. I think the climate part referred to the unheated garage I work in which happens to be where the wood is stored.

James,

Originally posted by AudialDelta
If you use plywood for enclosures, use only certified void free. Baltic Birch and marine grade are both available in a void free variety.

I agree but I can't justify it for this set. I often use 1" multi-lam (16 lam) poplar. but again these are small so a 1 1/2" thick wall all around I think will suffice. (two layers, flat stacked 3/4") baffle and back.

[i]Most upper end speakers that use wood as an enclosure material laminate Baltic Birch (BB) on the exterior and MDF on the interior. The greater density of MDF lowers cabinet resonance frequency. The stiffness of BB yeilds a higher enclosure resonant frequency. MDF will hold on to acoustical energy longer than BB. It is a balancing act. [/B]

That's interesting to know. These cabinets are small and will show little resonance due to their shape and thickness.

[i]Why do you need to stack so many pieces? If you have a complex curve it would be more sensable to use thin material. Once it is curved, braced & secured it will be significantly stronger than a flat piece of equal thickness. [/B]

As I have changed from a compound curve (which I wouldn't be able to shape by flat stacking panels) to a double "s" curve (which I can) I now have that option but I think it would take too long adding layer after layer of 1/4" to get to 1 1/2" Also the curve might be a bit tight and cause undo stresses on the wood.

I'll need a minimum of 11 pieces to achieve the internal volume.

I am able to get all the cutouts for one cabinet from a 4X8 sheet so in all it's only 50 bucks Cdn.

Thanks again for all the answers thus far.

[pinkmouse]

Are you cutting the sections yourself with a router ang jig or similar? If so, you might want to put a couple of indexed holes in each section so you can assemble them on dowel rods. It makes it a lot easier for alignment. You could even use threaded rod, then you can use it to clamp them together as you assemble.

[Cal Weldon]

Excellent idea Al. I was just going to use a jig with the posts on the outside to keep it aligned and then screw each lam together. That rod idea might just be the trick.

[AudialDelta]

I'm not "seeing" your curve. Thinner material is still the way to go in order to make it curve without the potential of cracking the material. How many sides of the enclosure will have this "S-curve"? I also doubt that you will be successful in filling the voids. Maybe visually, but not under close inspection. I also still think you will be better off with something other than ply wood for the inner - unseen layers. Use a 1/8 inch BB for the outer-most layer.

[Cal Weldon]

Hi, to make this easy:

Picture a fish. Now lay it out on a piece of plywood. Cut out fish shape and also cut out the centre of the fish so the walls are about 1 1/2". Do this 11 times and stack all 11 fish together, add a top and bottom and you have a hollow cabinet. The outside will be coated to fill in the grain, then painted.

EDIT: On second thought, I'm not making a double S curve, I am making two S curves, sorry for the confusion.