Steam bending Large timber
- Thread starter JDGreen
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Jacob
What goes around comes around.
No don't be put off, go for it!custard":1nskdagt said:
But I think you are probably over thinking it. Get stuck in, head down brain in neutral!
One of the first things I made (in a previous existence as a toymaker, age about 22 working in a little flat), was a rocking horse with laminated rockers. Bought 1/4" x 1 1/2" softwood cramped around a former made of ply. Worked really well first time. Nothing ventured nothing gained, even if all you gain is knowing not to do it the same way next time!
Useful tips
1 reserve the straight grained knot free stuff for the inner and outer faces, any old carp including cross grain can go in the middle.
2 PVA glue best for almost everything
3 consider hardwood for the outer strips and just softwood for the inner pieces. Looks better, wears better, often available in nice straight grain pieces.
I would laminate. At 3" thick presuming relatively thin laminates you should have minimal spring back unlike steam bending where there are so many variables. Also for acoustic use laminations should be more "dead" due to negating any defects in the wood. I may have missed it but how tight is radius you are needing?
I cant see any insurmountable problems either. My dad built a 26' foot boat with minimal woodwork experience and involved loads of laminating so as said dont be put off.
I cant see any insurmountable problems either. My dad built a 26' foot boat with minimal woodwork experience and involved loads of laminating so as said dont be put off.
profchris
Established Member
JDGreen":24tj31df said:
That's a pretty tight radius for bending wood! Very similar to bending the waist of a guitar, where even 3mm (1/8) is considered very challenging.
Have you considered cutting the bulk of the thickness from solid on a bandsaw, and then adding laminations on the inner and outer curves to strengthen it? This is effectively what instrument repairers do when a guitar is knocked over and the peghead snaps off, and is reckoned to be a pretty strong method.
Perhaps 3 x 1/8 laminations each side, so you'd have 2 1/4 width in solid and 3/8 either side in laminations.
Ash bends fairly easily at 1/8 just with heat, as does walnut. For this I'd use my solid part as a form, clamp a single lamination to it with a metal strip on the outside to help stop any runout separating (but use very straight-grained wood, with the straightness running along the 1/8 dimension, it doesn't matter much how the grain runs along the width of the plate) and heat it with a heat gun until the wood is uncomfortably hand-hot all the way through the lamination. But stop before it scorches
! It's probably safest to clamp loosely when the wood is cold, and increase clamping pressure once it's hot. Then let it cool. The lamination will spring back somewhat, but should be close enough to be glued and clamped. Repeat for each individual lamination (you probably won't want to glue up until all are bent because most glues you might use will release with heat).The obvious downside is that there will be a very visible difference between the solid part and the laminated facings. But you might make a feature of that - ash core and walnut/ash/walnut laminations, or vice versa.
If you want something other than ash or walnut, I'd go much thinner, 2mm or less.
profchris
Established Member
And thinking about this more, what's wrong with a plywood core and 1/16 facings of your chosen pretty wood all round? At 1/16 you probably wouldn't need much, if any, heat to bend ash or walnut.
I've also just remembered that straight-grained oak (or at least, my piece of oak) bends very easily at just over 1/16, though it does need heat.
I've also just remembered that straight-grained oak (or at least, my piece of oak) bends very easily at just over 1/16, though it does need heat.
Ther is a third way of achieving your desired result. I make arched door frames, and windows doors using this method.
Split you arch in half, you cut out using a Bandsaw the two curves that will meet in the middle. You will need 4 such sections each being 1” thick. Now split the curve into three, with the two angles being 60 degrees. Again cut out using the Bandsaw from 1” thick stock. The parts are now laminated together such that the two outer surfaces have the parts meeting at the top. The centre section is solid over the joint and ensures that there are no areas of the curve that is particularly week / relying on a joint. When gluing up I do it in stages. First I use screws initially from the centre sections into one of the outside sections and wait for it to dry. I then remove the screws and glue on the remaining outside laminate clamping it up. I would use Cascamite (or any of the derivatuves) for gluing. The finished item looks the same from both sides.
You don’t need to be experienced or competent to achieve really good results. Firstly if the when trying to get the joints to meet properly (before gluing) you can simply clamp the two pieces so that the joint is touching and using a hand saw Resaw down the joint. This will close the joint up to a good fit.
Secondly don’t get too worried about getting a perfect curve with the Bandsaw if you have a router (or better still a spindle moulder). Make all parts using patterns made from 9mm MDF or similar. I make the patterns for the parts larger than they need to be as this ensures I have something to cut off when it fully glued up. Use a full size pattern of the curve to either use a bearing guided router bit and a router or spindle moulder to cut the laminated glued up part to the correct curve.
You can use any species of wood that you can get in wide enough sections. It’s far easier tpand usually cheaper to get thinner stuff that is knot free than it is larger sections. The lamination will also virtually prevent any twisting or movement in the finished piece.
Split you arch in half, you cut out using a Bandsaw the two curves that will meet in the middle. You will need 4 such sections each being 1” thick. Now split the curve into three, with the two angles being 60 degrees. Again cut out using the Bandsaw from 1” thick stock. The parts are now laminated together such that the two outer surfaces have the parts meeting at the top. The centre section is solid over the joint and ensures that there are no areas of the curve that is particularly week / relying on a joint. When gluing up I do it in stages. First I use screws initially from the centre sections into one of the outside sections and wait for it to dry. I then remove the screws and glue on the remaining outside laminate clamping it up. I would use Cascamite (or any of the derivatuves) for gluing. The finished item looks the same from both sides.
You don’t need to be experienced or competent to achieve really good results. Firstly if the when trying to get the joints to meet properly (before gluing) you can simply clamp the two pieces so that the joint is touching and using a hand saw Resaw down the joint. This will close the joint up to a good fit.
Secondly don’t get too worried about getting a perfect curve with the Bandsaw if you have a router (or better still a spindle moulder). Make all parts using patterns made from 9mm MDF or similar. I make the patterns for the parts larger than they need to be as this ensures I have something to cut off when it fully glued up. Use a full size pattern of the curve to either use a bearing guided router bit and a router or spindle moulder to cut the laminated glued up part to the correct curve.
You can use any species of wood that you can get in wide enough sections. It’s far easier tpand usually cheaper to get thinner stuff that is knot free than it is larger sections. The lamination will also virtually prevent any twisting or movement in the finished piece.
profchris":2popw688 said:JDGreen":2popw688 said:
That's a pretty tight radius for bending wood! Very similar to bending the waist of a guitar, where even 3mm (1/8) is considered very challenging.
Have you considered cutting the bulk of the thickness from solid on a bandsaw, and then adding laminations on the inner and outer curves to strengthen it? This is effectively what instrument repairers do when a guitar is knocked over and the peghead snaps off, and is reckoned to be a pretty strong method.
Perhaps 3 x 1/8 laminations each side, so you'd have 2 1/4 width in solid and 3/8 either side in laminations.
Ash bends fairly easily at 1/8 just with heat, as does walnut. For this I'd use my solid part as a form, clamp a single lamination to it with a metal strip on the outside to help stop any runout separating (but use very straight-grained wood, with the straightness running along the 1/8 dimension, it doesn't matter much how the grain runs along the width of the plate) and heat it with a heat gun until the wood is uncomfortably hand-hot all the way through the lamination. But stop before it scorches
The obvious downside is that there will be a very visible difference between the solid part and the laminated facings. But you might make a feature of that - ash core and walnut/ash/walnut laminations, or vice versa.
If you want something other than ash or walnut, I'd go much thinner, 2mm or less.
Thanks for the advice! That's why I can to a forum as to me looking at it it doesn't look much of a deviation. Perhaps I should've stated that it's not going to be a simple curve bend but rather go from a straight to curve out towards the top of the structure. Not sure if that makes it worse or better, but as I state that's why I'm on here! I like the idea of different laminations being used to create a feature though, hadn't thought of that! Thanks again!
It doesn’t make any difference depending on how complex is the shape. The only thing to consider is an aesthetic perspective, that is, the joints I’ll be seen. So, as it’s decorative, you could book match on the face side and be careful where you place the joints. You don’t have to keep to just 3 laminations, but odd numbers work best.
Hornbeam
Established Member
]No don't be put off, go for it!
But I think you are probably over thinking it. Get stuck in, head down brain in neutral!
One of the first things I made (in a previous existence as a toymaker, age about 22 working in a little flat), was a rocking horse with laminated rockers. Bought 1/4" x 1 1/2" softwood cramped around a former made of ply. Worked really well first time. Nothing ventured nothing gained, even if all you gain is knowing not to do it the same way next time!
Useful tips
1 reserve the straight grained knot free stuff for the inner and outer faces, any old carp including cross grain can go in the middle.
2 PVA glue best for almost everything
3 consider hardwood for the outer strips and just softwood for the inner pieces. Looks better, wears better, often available in nice straight grain pieces.[/quote]
This is a recipe for firewood.
If you are not prepared to compromise your design, them laminating is definitely the way to go.
Laminates will expand/contract like normal wood so all laminates should have the grain in the same direction.
PVA glue is not the best for laminating as it does not produce as stiff a laminate and often has short open times which mean you would have to work very fast.
Nothing wrong with a softwood core, but if it is going to be visible you will have to veneer over it.
I dont mean to be too negative but you have to balance your skills and whether you want a complex design with execution issues or a simpler design with betterexecution
Ian
But I think you are probably over thinking it. Get stuck in, head down brain in neutral!
One of the first things I made (in a previous existence as a toymaker, age about 22 working in a little flat), was a rocking horse with laminated rockers. Bought 1/4" x 1 1/2" softwood cramped around a former made of ply. Worked really well first time. Nothing ventured nothing gained, even if all you gain is knowing not to do it the same way next time!
Useful tips
1 reserve the straight grained knot free stuff for the inner and outer faces, any old carp including cross grain can go in the middle.
2 PVA glue best for almost everything
3 consider hardwood for the outer strips and just softwood for the inner pieces. Looks better, wears better, often available in nice straight grain pieces.[/quote]
This is a recipe for firewood.
If you are not prepared to compromise your design, them laminating is definitely the way to go.
Laminates will expand/contract like normal wood so all laminates should have the grain in the same direction.
PVA glue is not the best for laminating as it does not produce as stiff a laminate and often has short open times which mean you would have to work very fast.
Nothing wrong with a softwood core, but if it is going to be visible you will have to veneer over it.
I dont mean to be too negative but you have to balance your skills and whether you want a complex design with execution issues or a simpler design with betterexecution
Ian
custard
Established Member
Hornbeam's starting to flush out some of the "unknown unknowns" that will almost certainly scupper this plan.
A 3"x 3" lamination is an absolute whopper for a novice working alone in their shed. The thicker the individual lamina the greater the springback and the greater the force needed to bend the lamination around the former. So let's make an assumption that you go for about 3mm thick, so that's around 25 individual lamina. How long will it take you to glue up 25 1200mm x 75mm lamina? Well, I can guarantee it's longer than the open time of PVA! So you'll need a Urea Formaldehyde glue, you could use Cascamite, but Bordens or another liquid UF glue would be better. A UF glue will dry glass hard, so you won't suffer the "creep" that you'd get with PVA. But you'll have a much bigger problem cleaning off the squeeze out. As well as squeeze out the lamina will likely slip by a fraction and need trimming, so you need to decide how much wider to make your lamina to allow for this, and also decide how you'll trim to final dimensions?
These are laminated components for a chair I regularly make,
These are UF glue lines. I'd like to get them just a whisker cleaner, but this is as good as I can get. These lamina are about 1.5mm thick, by having thin lamina like these I get almost zero springback and very high dimensional stability. It's also very manageable with normal workshop cramps.
You also need to think hard about the former. You could try using just a single male former, but that won't deliver the best glue lines. Given that your glue lines will already look less attractive with UF than with PVA you need to do everything you can to keep them as clean as possible. Personally I'd definitely be using both a male and female former. Here's what this looks like,
Here are the glued up lamina being stacked into this former,
Couple of critical points here that are visible in these photos. Firstly, note the interlaced wooden guides that ensure the two halves of the former comes together accurately and that also keep the lamina neatly stacked and prevent them skewing out as cramp pressure is applied. Secondly, making these formers isn't as straightforward as just bandsawing a curve in a glued up block of MDF or ply. For a 35mm thick component that curve needs to be 35mm wide. That's the only way you'll get a gap free joint with tight glue lines. Achieving a precise 35mm wide curve that exactly conforms to your required radius (plus whatever is your springback allowance) takes a bit of doing. You need a fully thought through plan for achieving that with the tools and machinery at your disposal.
A 3" thick lamination is much, much harder than say a 1" thick lamination. So until you've successfully completed a few 1" thick lamination, you'll have almost no chance of doing an accurate, clean, and professional looking job on a 3" thick lamination. I appreciate no-one wants to hear this, but after forty years of doing this stuff I can assure you that's just the way it is.
A 3"x 3" lamination is an absolute whopper for a novice working alone in their shed. The thicker the individual lamina the greater the springback and the greater the force needed to bend the lamination around the former. So let's make an assumption that you go for about 3mm thick, so that's around 25 individual lamina. How long will it take you to glue up 25 1200mm x 75mm lamina? Well, I can guarantee it's longer than the open time of PVA! So you'll need a Urea Formaldehyde glue, you could use Cascamite, but Bordens or another liquid UF glue would be better. A UF glue will dry glass hard, so you won't suffer the "creep" that you'd get with PVA. But you'll have a much bigger problem cleaning off the squeeze out. As well as squeeze out the lamina will likely slip by a fraction and need trimming, so you need to decide how much wider to make your lamina to allow for this, and also decide how you'll trim to final dimensions?
These are laminated components for a chair I regularly make,
These are UF glue lines. I'd like to get them just a whisker cleaner, but this is as good as I can get. These lamina are about 1.5mm thick, by having thin lamina like these I get almost zero springback and very high dimensional stability. It's also very manageable with normal workshop cramps.
You also need to think hard about the former. You could try using just a single male former, but that won't deliver the best glue lines. Given that your glue lines will already look less attractive with UF than with PVA you need to do everything you can to keep them as clean as possible. Personally I'd definitely be using both a male and female former. Here's what this looks like,
Here are the glued up lamina being stacked into this former,
Couple of critical points here that are visible in these photos. Firstly, note the interlaced wooden guides that ensure the two halves of the former comes together accurately and that also keep the lamina neatly stacked and prevent them skewing out as cramp pressure is applied. Secondly, making these formers isn't as straightforward as just bandsawing a curve in a glued up block of MDF or ply. For a 35mm thick component that curve needs to be 35mm wide. That's the only way you'll get a gap free joint with tight glue lines. Achieving a precise 35mm wide curve that exactly conforms to your required radius (plus whatever is your springback allowance) takes a bit of doing. You need a fully thought through plan for achieving that with the tools and machinery at your disposal.
A 3" thick lamination is much, much harder than say a 1" thick lamination. So until you've successfully completed a few 1" thick lamination, you'll have almost no chance of doing an accurate, clean, and professional looking job on a 3" thick lamination. I appreciate no-one wants to hear this, but after forty years of doing this stuff I can assure you that's just the way it is.
Attachments
MikeG.
Established Member
custard":2chv9in6 said:
This needs re-iterating, and illustrating it will really help make the point. This is what you are going to need to achieve:
Note that the two curves do not have the same radius:
Sgian Dubh
Established Member
Another adhesive choice would be a slow set epoxy resin, which gives about an hour to apply the adhesive, get the laminates into a former, and apply the pressure.custard":2eje0ygi said:
Neither sophisticated laminating or steam bending are an easy challenge for someone with either very limited experience, or no knowledge at all.
Anyway, below is some laminating I did in cherry, just for an example. Slainte.
These laminated cherry bits …
… were made with these constructional veneers …
which were slathered in epoxy resin and bent over a former in a bag press, thus …
Epoxy or slow set PU work fine for large glue ups. If you use epoxy just clean off the squeeze out when green to make life easier. If 3" is too daunting to do in on I cant see why you cant build it up in stages 2 or 3 stages. I helped next doors 16year old make a laminated CD rack that was 4x1 and about 70cm long. No issues
Hornbeam
Established Member
Laminations can be built up in sections but you need to have enough initial laminations to get no significant springback and this can only really be done with a single male mould approach. David Charlesworth did a fantastic oak table with laminated legs in this manner years ago in Furniture and cabinet making. Laminations can be thicker but have to bend easily. You would probably be OK with 8 or 10 laminates around 7-8mm thick (look at the thickness on structural glulam beams) but changes in grain seem to be more noticable.
Agree with earlier comments regarding try a thinner simpler lamination project first
Ian
Agree with earlier comments regarding try a thinner simpler lamination project first
Ian
MikeG.
Established Member
Hornbeam":ay6bmm9u said:
I'm confused by this a little. Glulams are usually straight, and made of segments of wood substantially larger than 7 or 8mm thick. Mine, for instance, are made up of pieces of 50x25. Given the differences I'm not sure what point you are trying to illustrate with this suggestion. I'm not for a second saying you are wrong, just that I don't understand your use of the example.
Hornbeam
Established Member
The point I am making is that laminations dont have to be 2mm constructional veneer thickness. Glu lam beams come in all sizes and large curved beams are fairly common (google curved glulam beams images) but the laminate thicknesses might be 25mm. On that basis you can select a laminate thickness to suit your specific job but I would say you should have at least 8 laminates
Ian
Ian
Wow guys and gals! Honestly blown away at the lengths you are going to to help me with this! As I fully expected there is so much more that I need to know hence the reason for broaching the subject in a forum, where there is a wealth of knowledge and varying techniques that have worked for various people in various projects. I've certainly learned a lot! Despite always knowing that this would be the hardest project I've done to date, it's still something I aspire to do. The client is a good friend of mine so whilst the fear of ruining a piece for a high paying client isn't necessarily there, there is still the desire to produce the perfect piece! I am taking on board everything everyone is saying and whilst there is a lot of contrasting information I think I'm getting the picture of what I need to focus on and where I need to focus more research.
Thanks again everyone for your input, it's most appreciated.
Joe
Thanks again everyone for your input, it's most appreciated.
Joe
worn thumbs
Established Member
Is there a problem if there is a 1.5mm springback on the project?Without seeing what the proposal is for its a bit difficult to either praise or condemn any of the proposals.Laminating in stages is quite easy and even gives the benefit that you can rout a groove up the middle laminates to run the cables through.It does help to use a reasonably thick pressure batten at each stage and you don't have to used matched inner and outer formers if you don't want tne other point to keep in mind is that you would need to cover the surface of the laminating former with parcel tape to avoid leaving the laminate attached.I have seen a fellow lay a couple of sheets of newspaper down and it went a bit wrong when the paper wrinkled and a fold went into the glue line.Not a success.
ne other point to keep in mind is that you would need to cover the surface of the laminating former with parcel tape to avoid leaving the laminate attached.I have seen a fellow lay a couple of sheets of newspaper down and it went a bit wrong when the paper wrinkled and a fold went into the glue line.Not a success.Similar threads
