I need to make some instrument cases (mandolin, mandola, etcetera) and
want to make curved ends - best visual analogy I can think is that the
plan view shows a shape like a belt going around a small and large
pulley. The problem is what to use for the curved ends.
I'm expecting to have to laminate some strips of something around a
former but all I can think of to use is aero ply, and that's too expensive.
The tightest radius of curvature is going to be about 100mm and the
width is going to be about 150mm; I need to be able to attach the curved
ends to the (rigid) long sides.
What material can the team suggest?

On Saturday, November 8, 2014 6:36:15 PM UTC, wrote:
What material can the team suggest?

Steamed hardboard.

Several layers of it well glued up should be fairly strong once it's all set.

Owain

On Saturday, November 8, 2014 6:36:15 PM UTC, wrote:
I need to make some instrument cases (mandolin, mandola, etcetera) and
want to make curved ends - best visual analogy I can think is that the
plan view shows a shape like a belt going around a small and large
pulley. The problem is what to use for the curved ends.
I'm expecting to have to laminate some strips of something around a
former but all I can think of to use is aero ply, and that's too expensive.
The tightest radius of curvature is going to be about 100mm and the
width is going to be about 150mm; I need to be able to attach the curved
ends to the (rigid) long sides.
What material can the team suggest?

Have you looked at bendy ply from a timber merchant like Arnold Laver? It's not that expensive in small quantities and pretty easy to work with.

http://www.laver.co.uk/files/mydocs/...ffice_copy.pdf

wrote:

The tightest radius of curvature is going to be about 100mm and the
width is going to be about 150mm;

Doesn't that make for a bend radius of 75mm, unless you mean depth?

On 08/11/14 19:32, mike wrote:
On Saturday, November 8, 2014 6:36:15 PM UTC, wrote:
I need to make some instrument cases (mandolin, mandola, etcetera) and
want to make curved ends - best visual analogy I can think is that the
plan view shows a shape like a belt going around a small and large
pulley. The problem is what to use for the curved ends.
I'm expecting to have to laminate some strips of something around a
former but all I can think of to use is aero ply, and that's too expensive.
The tightest radius of curvature is going to be about 100mm and the
width is going to be about 150mm; I need to be able to attach the curved
ends to the (rigid) long sides.
What material can the team suggest?

Have you looked at bendy ply from a timber merchant like Arnold Laver? It's not that expensive in small quantities and pretty easy to work with.

http://www.laver.co.uk/files/mydocs/...ffice_copy.pdf


Bloke next door steams wood and bends it. His steamer is a box fed by a
pipe from a small simple water boiler.

IIRC he leaves it for quite some time (hours at least).

On 08/11/2014 19:56, Tim Watts wrote:
Bloke next door steams wood and bends it. His steamer is a box fed by a
pipe from a small simple water boiler.

IIRC he leaves it for quite some time (hours at least).

That's the way to do it.

I've actually straightened a bent walking stick with a heat gun, but
steam is far more controlled.

A wallpaper steamer might be a good steam source.

Andy

On 08/11/14 21:47, Vir Campestris wrote:
On 08/11/2014 19:56, Tim Watts wrote:
Bloke next door steams wood and bends it. His steamer is a box fed by a
pipe from a small simple water boiler.

IIRC he leaves it for quite some time (hours at least).

That's the way to do it.

I've actually straightened a bent walking stick with a heat gun, but
steam is far more controlled.

A wallpaper steamer might be a good steam source.

Andy

Yes - I think it would be a good source. You don't need huge volumes if
the box is reasonably small (couple of foot long) and not too leaky.

This is a wooden box BTW - bit of WBP ply would probably do a few
steamings before it died. Or use wide planks screwed edge to edge and
both ends blanked. Top plank unscrews to be the way into the box.

On Sat, 08 Nov 2014 18:36:11 +0000, wrote:

What material can the team suggest?

Google for "rec.woodworking Steambending wood Frequently asked Questions".

And there's a "bendy wood" at the lumber merchants. AFAIK it's beech that's been
steamed and dried.

Also availabel "bendy MDF", MDF with many parallel cuts, like a comb. It needs
two layers glued together (with the "teeth facing", as it were) and will
probably be too thick for an instrument case.


Thomas Prufer

In message , Vir
Campestris writes
On 08/11/2014 19:56, Tim Watts wrote:
Bloke next door steams wood and bends it. His steamer is a box fed by a
pipe from a small simple water boiler.

IIRC he leaves it for quite some time (hours at least).

That's the way to do it.

I've actually straightened a bent walking stick with a heat gun, but
steam is far more controlled.

A wallpaper steamer might be a good steam source.

Andy
The steam box is the traditional way, but I'll repeat my method that I
used where we needed to steam in situ.
I got some polythene layflat tubing and tied it around the rim of the
place where the lid fits on an old kettle. We threaded the tubing over
the 25foot long timbers of the boat and covered the tubing with old
pyjamas for insulation. The kettle could be refilled as necessary via
the spout, but the tube was angled to drain condensate back into the
kettle.

The only problem was the heady pine vapour and the condensate which
tended to froth when back in the kettle.

I also used this for parts eg the tiller, which were strips steamed and
bent round a mould, then laminated with epoxy.
--
Bill

On Saturday, 8 November 2014 18:36:15 UTC, wrote:
I need to make some instrument cases (mandolin, mandola, etcetera) and
want to make curved ends

Don't steam anything.

These cases need to be light (it's horribly easy to end up overweight), so the materials will be thin. That means you can cold bend them. 1/8" birch ply is expensive, but affordable (price/strength/weight ratio is worth it). It's cheaper if you can find a grade with only one (or no) perfect surfaces.. You can use a single layer of this, curved around a former and glued. Buttress the inside corner with either lots of blocks, almost touching, a steam bent strip of hardwood (beech or slow-grown ash) or a machined groove in some solid.

To make a compound curve (which is hard), make it from glulam. This is home-made plywood, made from single veneers laid over a former and then laminated. Vacuum bagging is a good way to clamp it all up. Beech or ash are again some of the cheaper and easier veneers to find. This veneered glulam technique, with diagonal veneers, is a strong and light way to make a single-curvature case too. If you're making a number of identical cases and make a good plug mould with a vacuum bag, this is a really good way to make them.

When constructed, I find Wickes Wet Rot Hardener (bit under a tenner for 500ml) is a great surface hardener for wood and easier than diluting epoxy.

On 08/11/2014 19:06, wrote:
On Saturday, November 8, 2014 6:36:15 PM UTC, wrote:
What material can the team suggest?

Steamed hardboard.

Several layers of it well glued up should be fairly strong once it's all set.

Owain


Interesting idea - I'm happy with bending instrument ribs but hadn't
thouht of hardboard - a couple of layers may be too heavy but I'll
investigate.

On 08/11/2014 19:32, mike wrote:
On Saturday, November 8, 2014 6:36:15 PM UTC, wrote:
I need to make some instrument cases (mandolin, mandola, etcetera) and
want to make curved ends - best visual analogy I can think is that the
plan view shows a shape like a belt going around a small and large
pulley. The problem is what to use for the curved ends.
I'm expecting to have to laminate some strips of something around a
former but all I can think of to use is aero ply, and that's too expensive.
The tightest radius of curvature is going to be about 100mm and the
width is going to be about 150mm; I need to be able to attach the curved
ends to the (rigid) long sides.
What material can the team suggest?

Have you looked at bendy ply from a timber merchant like Arnold Laver? It's not that expensive in small quantities and pretty easy to work with.

http://www.laver.co.uk/files/mydocs/...ffice_copy.pdf


I'd seen bendy MDF (too heavy) but not bendy ply - I'll see what price I
can get locally. Also, I'll try slotting one side of some standard ply
to different depths and see if it will go round a former without breaking

On 08/11/2014 19:56, Tim Watts wrote:
On 08/11/14 19:32, mike wrote:
On Saturday, November 8, 2014 6:36:15 PM UTC, wrote:
I need to make some instrument cases (mandolin, mandola, etcetera) and
want to make curved ends - best visual analogy I can think is that the
plan view shows a shape like a belt going around a small and large
pulley. The problem is what to use for the curved ends.
I'm expecting to have to laminate some strips of something around a
former but all I can think of to use is aero ply, and that's too
expensive.
The tightest radius of curvature is going to be about 100mm and the
width is going to be about 150mm; I need to be able to attach the curved
ends to the (rigid) long sides.
What material can the team suggest?

Have you looked at bendy ply from a timber merchant like Arnold
Laver? It's not that expensive in small quantities and pretty easy to
work with.

http://www.laver.co.uk/files/mydocs/...ffice_copy.pdf



Bloke next door steams wood and bends it. His steamer is a box fed by a
pipe from a small simple water boiler.

IIRC he leaves it for quite some time (hours at least).

I've bent wet wood on a bending iron but haven't tried steaming - I
wonder if that's likely to work on some cheap non-quarter sawn 4mm deal... ?

On 09/11/14 21:55, wrote:

I've bent wet wood on a bending iron but haven't tried steaming - I
wonder if that's likely to work on some cheap non-quarter sawn 4mm
deal... ?

Seem to recall guitar sides are bent on a large diameter steam pipe, ie
hot dry bent.

On 09/11/2014 22:03, Tim Watts wrote:
On 09/11/14 21:55, wrote:

I've bent wet wood on a bending iron but haven't tried steaming - I
wonder if that's likely to work on some cheap non-quarter sawn 4mm
deal... ?

Seem to recall guitar sides are bent on a large diameter steam pipe, ie
hot dry bent.

The ribs (sides) are frequently wetted during the bending, and it can
make things easier to soak them for a while beforehand. Ribs will be
around 2mm thick.

A bending iron is a curved (aerofoil'ish, viewed from the top) block of
aluminium with an electrical heater inside, although I've seen pictures
of people bending around a pipe with a blowlamp playing on the inside of
the pipe.

On Sun, 09 Nov 2014 22:58:24 +0000, wrote:

On 09/11/2014 22:03, Tim Watts wrote:
On 09/11/14 21:55, wrote:

I've bent wet wood on a bending iron but haven't tried steaming - I
wonder if that's likely to work on some cheap non-quarter sawn 4mm
deal... ?

Seem to recall guitar sides are bent on a large diameter steam pipe, ie
hot dry bent.

The ribs (sides) are frequently wetted during the bending, and it can
make things easier to soak them for a while beforehand. Ribs will be
around 2mm thick.

A bending iron is a curved (aerofoil'ish, viewed from the top) block of
aluminium with an electrical heater inside, although I've seen pictures
of people bending around a pipe with a blowlamp playing on the inside of
the pipe.

That's how I started out: a blowlamp and a stainless steel tube in a
vice in my mum's garage. But I've been using the aerofoilish type for
the past fifty years or so. The same bending iron too: it's had a
couple of replacement simmerstats and half-a-dozen cartridge heating
elements in its lifetime, though. A bit like the famous yard broom.

Incidentally, I'm reading this thread with interest because I've never
made cases: I suspect an entirely different skillset is probably
required.

Nick

On 16/11/2014 12:32, Nick Odell wrote:
On Sun, 09 Nov 2014 22:58:24 +0000, wrote:

On 09/11/2014 22:03, Tim Watts wrote:
On 09/11/14 21:55, wrote:

I've bent wet wood on a bending iron but haven't tried steaming - I
wonder if that's likely to work on some cheap non-quarter sawn 4mm
deal... ?

Seem to recall guitar sides are bent on a large diameter steam pipe, ie
hot dry bent.

The ribs (sides) are frequently wetted during the bending, and it can
make things easier to soak them for a while beforehand. Ribs will be
around 2mm thick.

A bending iron is a curved (aerofoil'ish, viewed from the top) block of
aluminium with an electrical heater inside, although I've seen pictures
of people bending around a pipe with a blowlamp playing on the inside of
the pipe.

That's how I started out: a blowlamp and a stainless steel tube in a
vice in my mum's garage. But I've been using the aerofoilish type for
the past fifty years or so. The same bending iron too: it's had a
couple of replacement simmerstats and half-a-dozen cartridge heating
elements in its lifetime, though. A bit like the famous yard broom.

Incidentally, I'm reading this thread with interest because I've never
made cases: I suspect an entirely different skillset is probably
required.

Nick


Nick, what simmerstat did you use? I've got a home-made bending iron but
I haven't got-around to fitting any form of temperature control yet.

Back to case building: I'm planning to use thin ply, joined with kerfed
linings (like moldless guitar making - is the board called a solara?)
and reinforced at load points with another layer of ply. This will be
covered with a honeycomb cardboard layer and then expanding foam to take
the shape of the instrument, and finally a fur fabric covering. I'll
probably stain and varnish the outside. Hopefully this will give good
protection and be fairly light.
Several years ago I built a flight case for a stage piano - it worked
well but was as heavy as the keyboard!

On Mon, 17 Nov 2014 12:19:08 +0000, wrote:



Nick, what simmerstat did you use? I've got a home-made bending iron but
I haven't got-around to fitting any form of temperature control yet.

This bending iron was a commercial product and when I needed a
replacement simmerstat I just took the old one into a domestic
appliance repair shop and they gave me the nearest equivalent. My
current one had to be fitted upside down in the base but electrically
it works fine. I'll try and remember to open it up and check the spec
tomorrow.

Incidentally, with the mass of aluminium acting as a heat sink it's
possible to set a constant steady temperature pretty easily and using
a small tin on top of it I cook up quantities of hide glue without the
need to use a water bath.

Nick

On 18/11/2014 00:29, Nick Odell wrote:
On Mon, 17 Nov 2014 12:19:08 +0000, wrote:



Nick, what simmerstat did you use? I've got a home-made bending iron but
I haven't got-around to fitting any form of temperature control yet.

This bending iron was a commercial product and when I needed a
replacement simmerstat I just took the old one into a domestic
appliance repair shop and they gave me the nearest equivalent. My
current one had to be fitted upside down in the base but electrically
it works fine. I'll try and remember to open it up and check the spec
tomorrow.

Incidentally, with the mass of aluminium acting as a heat sink it's
possible to set a constant steady temperature pretty easily and using
a small tin on top of it I cook up quantities of hide glue without the
need to use a water bath.

Nick

It would be useful to know how the simmerstat senses the temperature
(thermocouple, bourdon tube, internal bimetal strip, etcetera).

I've used a modified baby milk heater as a water bath - OK but not
brilliant.

On Tue, 18 Nov 2014 12:25:49 +0000, wrote:

On 18/11/2014 00:29, Nick Odell wrote:
On Mon, 17 Nov 2014 12:19:08 +0000, wrote:



Nick, what simmerstat did you use? I've got a home-made bending iron but
I haven't got-around to fitting any form of temperature control yet.

This bending iron was a commercial product and when I needed a
replacement simmerstat I just took the old one into a domestic
appliance repair shop and they gave me the nearest equivalent. My
current one had to be fitted upside down in the base but electrically
it works fine. I'll try and remember to open it up and check the spec
tomorrow.

Incidentally, with the mass of aluminium acting as a heat sink it's
possible to set a constant steady temperature pretty easily and using
a small tin on top of it I cook up quantities of hide glue without the
need to use a water bath.

Nick

It would be useful to know how the simmerstat senses the temperature
(thermocouple, bourdon tube, internal bimetal strip, etcetera).

If you mean, how does it sense the temperature of the main heating
element, the short answer is that it doesn't. The internal bi-metal
strip senses the temperature of the internal miniature heating element
so what you have going on is an analogue of the main situation.
There's more he http://en.wikipedia.org/wiki/Energy_regulator

Hysteresis is quite marked on a cooker hob but as I said before, with
the thermal mass of the aluminium casting, you can maintain a pretty
even temperature with the bending iron.


I've used a modified baby milk heater as a water bath - OK but not
brilliant.

The one I'm using at the moment simply says Diamond H Controls and it
was just a replacement part intended for a cooker hob.

Nick

On 19/11/2014 00:42, Nick Odell wrote:
On Tue, 18 Nov 2014 12:25:49 +0000, wrote:

On 18/11/2014 00:29, Nick Odell wrote:
On Mon, 17 Nov 2014 12:19:08 +0000, wrote:



Nick, what simmerstat did you use? I've got a home-made bending iron but
I haven't got-around to fitting any form of temperature control yet.

This bending iron was a commercial product and when I needed a
replacement simmerstat I just took the old one into a domestic
appliance repair shop and they gave me the nearest equivalent. My
current one had to be fitted upside down in the base but electrically
it works fine. I'll try and remember to open it up and check the spec
tomorrow.

Incidentally, with the mass of aluminium acting as a heat sink it's
possible to set a constant steady temperature pretty easily and using
a small tin on top of it I cook up quantities of hide glue without the
need to use a water bath.

Nick

It would be useful to know how the simmerstat senses the temperature
(thermocouple, bourdon tube, internal bimetal strip, etcetera).

If you mean, how does it sense the temperature of the main heating
element, the short answer is that it doesn't. The internal bi-metal
strip senses the temperature of the internal miniature heating element
so what you have going on is an analogue of the main situation.
There's more he http://en.wikipedia.org/wiki/Energy_regulator

Hysteresis is quite marked on a cooker hob but as I said before, with
the thermal mass of the aluminium casting, you can maintain a pretty
even temperature with the bending iron.


I've used a modified baby milk heater as a water bath - OK but not
brilliant.

The one I'm using at the moment simply says Diamond H Controls and it
was just a replacement part intended for a cooker hob.

Nick


Thanks!