bending ply

[steamboat]

Hello all. I have a woodworking predicament I need advice with.
I am making a pair of loudspeakers and want curved sides. I am using 4m plywood eventually laminated together over a former to get the shape I need. Unfortunately as you can see from the pictures the wood is not conforming to the shape evenly over the entire length and the edges are wavy, which is obviously no good as the sides need to be very accurate. Has anyone got any suggestions from their own experiences?
Any help welcome
sorry cant work out how to add pictures [/img]

 

[CNC Paul]

Hi Steamboat,

As I cannot see you picture I can only guess, For a complete even pressure you will need either a vacuum bag press or a male/female mould to press the parts.... going down the 2 part mould method they need to be very accurate. I would not use PVA glue.......try laminating resin.


Paul

 

[steamboat]

here are some pictures I hope
[C:\Documents and Settings\stevenbromley.GROUNDWORKWALES\Desktop\Tressordy0003][C:\Documents and Settings\stevenbromley.GROUNDWORKWALES\Desktop\Tressordy0004][C:\Documents and Settings\stevenbromley.GROUNDWORKWALES\Desktop\Tressordy0005]

 

[DaveL]

Hi Steamboat,

You will find some instructions for posting pictures here.

 

[wizer]

Steve you need to upload your pics to a photo hosting site. This forum does not let you upload pics directly to it.

 

[steamboat]

Hope this works this time and I hope everyone hasn’t lost interest.
Technology – it works sometimes?

it worked, mostly,
What you cant see is that I have six formers with the work clamped down onto it, and the length is around 1200mm long

 

[p111dom]

It's very simple. Your idea is sound but the formers aren't good enough. I'll send you a PM about it.

 

[CNC Paul]

Steamboat,

You really need a continous former like the one below, if you made it wider than the pieces you need and had a scrap plywood the same width over the top of the pieces you want to bond, you can screw through the scrap ply into the former every couple of inches. Don't foget newspaper between the layers.

I am lucky to have a vacuum bag press and I can machine rigid foam formers to laminate my panels. The picture below is the former I used for the doors in my avatar.

If you need any further help just let me know.


Paul

 

[Mr T]

Hi

Are you using bendi ply?This is a very flexible plywood, useful for laminating. Even using bendi ply the members of your former need to be more closely spaced, about 50-75mm. They should be fixed to back boards to give rigidity. The curvature of the male and female formers needs to be very accurate and allow for the thickness of the laminations. I would use cascamite/extramite, or whatever it is called at the moment, for laminating.

Chris

 

[steamboat]

Thanks everyone, I have started working on making more formers (male and female), unfortunately I have run out of ply so the project will have to wait.
I have got some bendy ply but it isn’t dense enough for the speakers as they need to be rigid and dead to knock on.
Thanks P111dom, I haven’t looked through the email yet but will tonight.
Although this has been a bugger of a project I don’t mind as it will put me in good stead for any further projects.
All the best

 

[Jake]

I wouldn't use bendy ply for speakers, it is very light and very porous.

Going down to an 2mm aircraft-type ply would help, but others have given you the real juice.

 

[jasonB]

As Jake says the aero ply will give a much more solid panel, I tend to use 1.5mm but anything around that size will be OK.

Jason