I'd like to make 2-off of the shape shown in the following sketch...

    http://audio.yachtsea.com/Spiral.jpg

Sizes haven't been finalised, but are of the following order, in mm...

Height: 600
Width: 500
Depth: 250

The smallest radius (in the centre of the spiral) is about 12mm, and I'm
thinking of a material thickness around 8mm. The idea is to form the thing
in a jig, such that the spiral holds its shape reasonably well when
removed - the whole thing will be enclosed within wooden boxes made of 18mm
birch ply, so pre-shaped sprials would make assembly easier.

I'm thinking of making the shape by building up a laminate of overlapping
sheets of thin ply, but I've never done any bendy wood stuff before. What
would be a good thickness to use? Is my minimum radius too small?

Any suggestions for alternative materials? I've been wondering if some sort
of thermoplastic could be used - something that could be softened with a hot
air gun and eased into shape.


-- 
Wally
www.artbywally.com
www.wally.myby.co.uk

In article <ZfgSe.23363$Jd.18381@fe11.news.easynews.com>, 
atdot@dotat.atdot says...

> I'd like to make 2-off of the shape shown in the following sketch...
> 
>     http://audio.yachtsea.com/Spiral.jpg
> 
> Sizes haven't been finalised, but are of the following order, in mm...
> 
> Height: 600
> Width: 500
> Depth: 250
> 
> The smallest radius (in the centre of the spiral) is about 12mm, and I'm
> thinking of a material thickness around 8mm. The idea is to form the thing
> in a jig, such that the spiral holds its shape reasonably well when
> removed - the whole thing will be enclosed within wooden boxes made of 18mm
> birch ply, so pre-shaped sprials would make assembly easier.
> 
> I'm thinking of making the shape by building up a laminate of overlapping
> sheets of thin ply, but I've never done any bendy wood stuff before. What
> would be a good thickness to use? Is my minimum radius too small?


I think you'd have to use something like birch veneer (which might not 
be easy to source) rather than ready-laminated ply, and steam it to get 
the small radius.

> 
> Any suggestions for alternative materials?


Sheet steel or aluminium?  Probably not suitable, as judging from the 
URL the acoustic properties will be significant.  Would be the easiest 
to form though, I think.  Maybe if you covered it with some deadening 
material.

On Sat, 03 Sep 2005 12:00:57 GMT, "Wally" <atdot@dotat.atdot> wrote:


>I'm thinking of making the shape by building up a laminate of overlapping
>sheets of thin ply, but I've never done any bendy wood stuff before. 


Ply is no use for this, as it's alredy laminated. Make your own instead,
from single veneers.

I've found Vale Veneers to be a good supplier
http://stores.ebay.co.uk/Vale-Veneers-co-uk_W0QQcolZ2QQdirZQ2d1QQdptZ0QQftidZ2QQsclZ0QQtZkm
There's also Shadbolts in NE London or Robbins in Bristol.

Glulam structures like this are great fun, so get some veneer and some
glue and just go to it. You can make all sorts of stuff.  Personally I
like hot hide glue, but cold PVA works fine. Vacuum bagging is a very
useful way of clamping laminations in situ, but your piece might be done
by a tensioned caul just as easily (piece of hefty Cordura nylon with
straps to tension it.

Rob Morley wrote:


> I think you'd have to use something like birch veneer (which might not
> be easy to source) rather than ready-laminated ply, and steam it to
> get the small radius.


Does it have to be birch, or would a.n.other wood veneer be okay?



> Sheet steel or aluminium?  Probably not suitable, as judging from the
> URL the acoustic properties will be significant.  Would be the easiest
> to form though, I think.  Maybe if you covered it with some deadening
> material.


I'm not sure it would be so easy to form, unless it was being done in short
strips. The length of the coil is about 3m, and the idea was to put short
pieces of wood in, building up the length and layers as I go. As you might
have guessed, it's for the inside of speakers (bass speakers), so I suspect
something a bit less acoustcally live than metal would be the way to go.


-- 
Wally
www.artbywally.com
www.wally.myby.co.uk

Andy Dingley wrote:


> Ply is no use for this, as it's alredy laminated. Make your own
> instead, from single veneers.
>
> I've found Vale Veneers to be a good supplier
>

http://stores.ebay.co.uk/Vale-Veneers-co-uk_W0QQcolZ2QQdirZQ2d1QQdptZ0QQftidZ2QQsclZ0QQtZkm

> There's also Shadbolts in NE London or Robbins in Bristol.


Cheers for those, and duly noted. Had a look at the offerings from the eBay
seller, and some of that stuff looks very interesting (long bits of
sapelle).



> Glulam structures like this are great fun, so get some veneer and some
> glue and just go to it. You can make all sorts of stuff.  Personally I
> like hot hide glue, ...


Is that the same stuff that really keen artists use for sealing canvases?
The stuff that reeks to high heaven? If it is, I'll stick (ho-ho) with the
PVA...


> ... but cold PVA works fine. Vacuum bagging is a very
> useful way of clamping laminations in situ, but your piece might be
> done by a tensioned caul just as easily (piece of hefty Cordura nylon
> with straps to tension it.


I have a vision of a sort of star style arrangement of vertical boards, each
with slots cut in them at the proper distances. The strips of veneer are put
in from above and the whole lot takes on the spiral shape. Supplemented with
spring clamps as needed. I'll see if I can put a picture on the web
sometime, to show what I have in mind.


-- 
Wally
www.artbywally.com
www.wally.myby.co.uk

In article <%L_Ue.11873$L04.11526@fe06.news.easynews.com>, 
atdot@dotat.atdot says...

> Rob Morley wrote:
> 
> > I think you'd have to use something like birch veneer (which might not
> > be easy to source) rather than ready-laminated ply, and steam it to
> > get the small radius.
> 
> Does it have to be birch, or would a.n.other wood veneer be okay?


Any you could get hold of would do - it's just that birch seems popular 
for ply so I thought it might be more readily available and cheaper than 
some of the more exotic woods.

> 
> > Sheet steel or aluminium?  Probably not suitable, as judging from the
> > URL the acoustic properties will be significant.  Would be the easiest
> > to form though, I think.  Maybe if you covered it with some deadening
> > material.
> 
> I'm not sure it would be so easy to form, unless it was being done in short
> strips. The length of the coil is about 3m, and the idea was to put short
> pieces of wood in, building up the length and layers as I go. As you might
> have guessed, it's for the inside of speakers (bass speakers), so I suspect
> something a bit less acoustcally live than metal would be the way to go.
> 

To form the sheet metal you just need to clamp one end between a couple 
of bars (or maybe weld it to a bit of pipe) and wrap the rest around it 
- it will spring out to about the right sort of shape.  But, as you say, 
not really acoustically suited, and covering it with something to deaden 
it would make the whole process more complicated.

On Sat, 03 Sep 2005 12:00:57 +0000, Wally wrote:


> I'd like to make 2-off of the shape shown in the following sketch...
> 
>     http://audio.yachtsea.com/Spiral.jpg
> 
> Sizes haven't been finalised, but are of the following order, in mm...
> 
> Height: 600
> Width: 500
> Depth: 250
> 
> The smallest radius (in the centre of the spiral) is about 12mm, and I'm
> thinking of a material thickness around 8mm. The idea is to form the thing
> in a jig, such that the spiral holds its shape reasonably well when
> removed - the whole thing will be enclosed within wooden boxes made of 18mm
> birch ply, so pre-shaped sprials would make assembly easier.
> 
> I'm thinking of making the shape by building up a laminate of overlapping
> sheets of thin ply, but I've never done any bendy wood stuff before. What
> would be a good thickness to use? Is my minimum radius too small?
> 
> Any suggestions for alternative materials? I've been wondering if some sort
> of thermoplastic could be used - something that could be softened with a hot
> air gun and eased into shape.



http://www.bpindex.co.uk/manf.html?id=865

These people have a shop at the bottom of the road. They specialise in
supply of very flexible ply woods. 


-- 
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk 
Gas fitting FAQ  http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html