Steam bending (again)

[Arron]

This is a follow up to a previous post of mine about problems steam bending. I have been trying to put a bend in a rather large lump of Sydney blue gum - 1200 x 200 x 21mm. After a bit more experimentation, I finally got usable output. It was still difficult. The curve is not perfect but in the finished job that isnt apparent. The one reference I can find to steam bending Sydney blue gum suggests that any shortcomings are to do with the fact that s.b.g. is unsuitable to bending, rather then to my technique.

This time round I beefed up the steam-power a lot. First I tried various gas burners, all of which were pretty wimpy and none produced anywhere close to the required amount of steam. Then I tried open fires - messy and probably illegal in this district. Next, I rescued a kettle barbecue from the council hard waste collection. I tried heat beads and other barbecue fuels in this - but they didnt generate enough heat - it seems they are designed to burn long but not really hot. Finally, success came with a pure wood fire. I used hardwood and cyprus offcuts, which burn hot and quick. Cutting away some of the wire grill on the barbecue meant I could keep the amount of heat up throughout by adding wood.

For those interested, this is how to bend large lumps of really ignorant woods, if you must:
First, you need lots of heat. References on the internet stated that the steam should be 'billowing out' - it takes a lot of heat to get steam billowing out the top of a steambox. If you can stand comfortably near your barbecue, forget it.
Second, take whatever you read on the internet about required steaming times and multiply by 50%, or just double it. They are probably right for easy bending woods like oak or beech (easy-peesy).
Keep the steam box small - my first box had too much airspace around the item.
Doing a big piece of timber as a one person job, you probably wont have enough strength to bend and clamp it. I used a hydraulic ram (actually trolley jack and a lump of ironbark) and bent between male and female moulds. This is quick and easy for one person and there is no need to fiddle with clamps.
Five litres of water in this setup lasts about 90 mins.
Finally, the vertical steambox worked better for me. I found a horizontal box problematic - I had difficulties getting good balance and flow through.

This is my latest setup:

[ozwinner]

Ya should have chucked a couple of snags on the BBQ while you were waiting.

:D :D :D

[gatiep]

Arron

Multiplying the steaming time by 50% halves it ??????????

[RETIRED]

It would also be nice to know if the articles from the net helped:rolleyes:

[seriph1]

bloody brilliant!

Love the idea and have several applications now for the method.

To get ideas about how to bend the curved panels in a sleighbed I am making, I visited a guy in Moama (NSW, near Echuca) who has a steam bending business - a nice bloke, but I came away believing these panels were just too big to steam bendc - your project has given me an idea!

Thanks heaps Arron

[Arron]

Steve, they sound like pretty big panels. Just how big are they ? I think I would be laminating those - especially if you cant see the edges - I steam bent my chair back because the edges would be the first thing you would see from above so I thought it would have to be one piece. Panels, I would still laminate.

Arron

[Ian Runge]

A good post! My attempts at steam bending (recently, with blackwood, and silver ash) have not proved successful, but have hit some fo the same issues.

1) I too used my Weber having found my gas BBQ and regular fires didn't give enough heat - though for me the head beads gave out much more heat than a regular fire
2) Also time in steam box was much more than the "received wisdom" suggests. (at the "requisite" time I pulled the timber out and it had NO bendability)

Before I try again, I want to solve a couple of puzzles:

1) It seems (according to the book - if the timber is properly steamed?) that it should bend relatively easily (i.e. by hand pressure ... wearing gloves, of course) yet I have never got close to this degree of flexibility.

2) Do you have to use "green" timber? -- my attempts have all been with air dried or kiln dried timber and I'm thinking this might be a reason why bending was so hard and shape retained only a low percentage of shape bent.

3) I read an article where pressure applied longitudinally along the wood during bending is the trick (v. hard to do in a small shop set-up).

Any additional help appreciated.

[Arron]

Hi Ian,
My understanding is that kiln dried timber of any sort is just about impossible to steam bend. Its so dry to start with that there is no moisture to carry the heat through, so even after a good steaming it is more likely to crack. I think that would almost definitely be the source of your troubles. Air dried is better. Green wood is best - much better - but what use is bending green wood if you are then going to use it for joinery - no use at all unless you are then going to season it for a year or two before using it. I think the fact that you and I both had over-dry timber was the reason we needed such long steaming times.

My understanding is that spotted gum is one of the easiest bending timbers. This is due to its very long grain, apparently. I think my next step will be to get some spotted gum (air dried) and experiment with that. Once I am bending it easily, I'll go back to the harder woods that interest me more. I believe jarrah is not bad for bending.

I am interested in your comment about heat beads being hotter though - what brand did you use ? I would like to use something a bit less smokey as I am probably on thin ice with the neighbours already.

cheers
Arron

[Phil Jennings]

Hi Arron and Ian,
this post is of immense value to me. I have a pice of silky oak 2400 x 200 x 35mm thick that I am going to bend. Note the positive thinking. Putting it through the thicknesser I had quite a bit of tear out due to its dryness. My woodwork teacher told me to soak it for a couple of hours in water with a little bleach, to prevent later mould, and then thickness it.

It suddenly occurred to me that this might be a good way to start the steaming process - with an already saturated piece of wood.

What do think?

Phil:confused:
ps Arron whereabouts in Sydney are you - do you need a stoker?

[seriph1]

gday again all

yeah, the panels are big - what I have resolved to do is: use cherry veneered super-bend ply(rest of the bed is 200+yr old European Pine)......I will be laminating several thinner pieces (with an ash veneer core - FAR cheaper than Cherry) together to get the thickness. This stuff dry-bends beautifully so I'll make formers and glue the panels up.


.... the finished product will look good I feel, though I havent made a sleighbed before and it is proving to be a BIG challenge to get the proportions "perfect".

The very-general style is similar to the attached stunning pics, though mine has far more pronounced curves - very "swan-neck-like" posts, and more 18th century country in feel ...... bloody hard to explain.

But either way, fun fun fun.... and a great project/learning process. So far I have made the four corner "posts" and the front top-rail, which required lamination in 3 pieces and a LOT of hand shaping/sanding

:)

[jacko]

I recently posted this in the "Timber " forum, but clearly the wrong spot. Also there must be a lot of published infomation out there, so any direction would help.
Can anyone out there help me with either a good reference to the bending properties of Ausssie timbers, or offer any advice? I am planning a small desk as shown in the attached images and the legs will need to be laminated/bent. I anticipate 4 plies of 6 mm being the base structure. Bend radius circa 100 mm. Second image follows

[jacko]

This is the front elevation, this time dwg is to scale.

[seriph1]

very funky - is that the writing surface at the front?


If you think its worth it, it may be worthwhile to call Period Home Renovator magazine and ask for the name and number of the "bending guy" in Echuca/Moama - give him a call and ask which timber would be best for steam bending. (They did an article on him in the last 2 years)

[Rocker]

Jacko,

For general information on bending wood, there is a Fine Woodworking book published by Taunton Press "Bending wood". For data on Australian wood properties, consult "Wood in Australia" by Keith Bootle. There is also an excellent article by Lon Scheinling in the August 2003 issue (#164) of Fine Woodworking on bent laminations.

I would say that you would have no hope of bending 6 mm plies to a radius of 100mm. To achieve that tight a curve you either need to use steam bending, or else use much thinner plies for a glued lamination. The Fine Woodworking article suggests a trial-and-error method for determining the appropriate thickness of the plies. The method is as follows: Cut a piece of wood to the same lenth and width as the lamination, and plane one face flat.
With the planed face against the bandsaw fence, resaw a test piece about 4 mm thick. Use double-sided tape to secure the slice, smooth-side down, to a piece of melamine. Then run it through a thicknesser to produce a lamination about 3 mm thick. remove from the melamine and test whether you can bend it with finger pressure around the convex side of your form without the lamination cracking. If not, re-attach to the melamine and plane away more wood until you can bend it satisfactorily.

Note also that PVA glue is not satisfactory for gluing bent laminations, because of its tendency to creep; you need to use urea formaldehyde glue with a liquid hardener, obtainable from Timbecon, or else epoxy.

Rocker

[jacko]

Seriph, yes that is a (narrow) writing surface, about 280 mm wide, just for writing cheques and small note etc. I will give echuca/moama a try, thanks
Rocker, thanks for the input. I was assuming that I would need to steam the laminations at the curved zone, put in form, then use the form plus laminations as the new form etc. When dry, glue up using AV 201.
Is this doable in your opinion?
Jacko

[Rocker]

Jacko,
I have not had any experience of steam-bending, so will not attept to advise you about it. However, I have never heard of steaming laminations. As far as I know, you should either steam solid wood or glue (unsteamed) laminations. I have serious doubts as to whether combining the techniques would work, but don't let me stop you experimenting.

My personal view is that you will find it very difficult to execute your design, because of the difficulty of ensuring that the bends that you hope to produce will be exactly 90 degrees. Unless you can achieve that with some accuracy, your desk is going to look lop-sided. My advice would be to follow a published plan, at least until you have some experience of bending wood under your belt.
There is a good book ("Desks", published by Taunton press), giving plans for seven different desks.

Rocker

[seriph1]

learning how to perfect this will render great satisfaction - I say GO FOR IT! After all, it has been done plenty of times elsewhere, so why can't you do it now?


:)

[Arron]

Jacko, Rocker is right. I really dont have much experience of steam bending, but I can tell you that those legs on your desk is not a suitable application. When steam bending, you always get spring back. You try to compensate for this by bending more then needed and hope it springs back to something pretty close to what you want, but still its a pretty hit-and-miss affair even with experience. As Rocker says, if you have 3 legs at 90deg and one at 87deg then your table is going to look pretty disappointing.

Because of this slight inaccuracy, steam bending works best where the design has some tolerance over the exact bend, or the bent component is secured at either end in such a way that a little pressure is used to force it into the exact angle, or the design is such that you cannot easily spot differences between bent components by eye.

Phil, I dont think soaking a piece of timber for a few hours before bending it is going to make much difference. I think the moisture is not going to penetrate far. I also dont know whether it is really possible to rehydrate. In other words, is a component that has been dried and then rehydrated going to perform the same as one that has never been dried out? I have done a fair bit of reading on this and have not encountered any advice to soak difficult or dry woods, which indicates to me it probably wont make much difference.

regards
Arron

[jacko]

So I'll add a stretcher at the bottom, this will correct for any mismatch.Rocker, I get half my enjoyment from designing then building and having the final product look mostly like the original design. PFE (proudly Found Elsewhere) doesn't do it for me i'm afraid. So it looks like a pretty steep- learning curve, if you will pardon the pun. What I am hoping is that the stiffness from 4 plies will more than compensate for springback once laminated. I have suffered from springback on a straight laminated peice, so am at least aware of the pitfalls. Thank you for the very helpful comments and tips. Greatly appreciated.
jacko

[DPB]

At the cost of timber, I admire your courage, Jacko. I'm going the other way, if I don't have a good plan to work from - forget it. I've wasted too much time (and money) experimenting.

I'm not an artist - but I am trying to become a reasonably good woodworker. I get no end of satisfaction from sitting back and looking at something that I made by hand when it turns out right.

In my retirement, this is a great change from 40 years of brain work which one never seems to complete. Before you get one challenge resolved the next challenge has raised its ugly head leaving no time to gloat over the resolution of the previous.
:)

[Rocker]

Jacko,

I wish you all success in your endeavour. I look forward to your posting a photo of the completed desk in due course, and to hearing how you succeeded in executing a very challenging design.

I was a bit misleading when I said I had no experience of steam bending. I have had a little, but it was an abject failure, so I have avoided the technique ever since, and used glued laminations instead.

Rocker

[AlexS]

Jacko,
I've had no experience of steam bending, but I really like your design, and I reckon you could do it with laminations, as long as they were fairly thin.

Whichever way you choose to go, good luck - looking forward to some pics.

[Ian Runge]

Arron and Phil,

I understand that the physics (or is it chemistry?) of steam bending is about changing the nature of the water molecules at a cellular level - the steam gets them all oriented in the same direction and thus easier to bend. Hence I guess the importance of your long-grained cells? in spotted gum. This suggests that air-dried timber (pre-soaked??) would be OK, but the KD process itself has these water molecules already removed and/or altered. So I think soaking the timber won't necessarily do any good if it has been kiln dried, but I suppose it can't hurt and may help if it has been air-dried.

As for the heat beads - I can't remember what brand. The tricks are: 1) don't use the easy start ones (except to get the fire started) because they don't last any time, and 2) the hard-to-start ones don't get to full heat until the fire has been going for at least 45 minutes ..... and about 15 minutes into this 45-minute start period you'll think that the fire has gone out! You also need lots of air flow from underneath of course.

Ian R.

[Ian Runge]

After my lack-of-success (better words than "failure") at steam bending I reverted to bent laminations. 1) you can use contrasting colour timbers if you wish, 2) spring-back is about nil, 3) I usually use 32mm MDF mould that can be cut to about any shape, and, as a bonus, 4) they are much stronger. I just finished a couple of bar stools - one in silver ash, one in blackwood - with bent legs each 28mm square section and with un-laminated timber a 28mm section would have been a big ask for a tall chair that people rock back on. For the silver ash, being a lighter timber, you can see the laminations, but on the blackwood a casual observer can not notice the laminations.

BUT there are undoubtedly important applications for steam bending thick pieces. I was at the Steinway factory in USA about 8 years ago .... did you know that the fancy curved back on those Steinway grand pianos is steam bent ... the timber being at least 300 mmm x 30 mm section! (perhaps laminated timber on a grand piano makes a different sound!)

Ian R.

[seriph1]

lucky bugger, getting to see Steinies being made!

Got any pics of either the factory or your chairs?

[Ian Runge]

I don't have any pics of the Steinway factory. Here is a pic of the silver ash chair [assuming it works .... I havn't posted any pics before]. The blackwood chair looks a little better than the silver ash chair, but the *photo* of the blackwood chair doesn't look as good as the *photo* of the silver ash chair.

The 4 legs and the chair back are bent laminations. Almost all joints are M&T. The arm rests are joined to the tops of the legs using a loose wedged tenon installed after the armrest had been glued to the flat top of the front legs. The backrest was similarly glued to the tops of the back legs, and the four round (loose) tenons installed afterwards.



Ian R.

[Ian Runge]

oops .... next time I'll post a smaller image

[seriph1]

very funky - this obviously wasn't your first attempt at making a chair


:)

[Wild Dingo]

Great thread!

Im about to steam bend two peices of Tuart {Bloody hard as buggary West Aussie Eucalypt of some sort whose latin name is just so unpronouncible Ive forgotten it and a damned site harder than Jarrah} for the stem and stern of a boat Im about to start building {and as Im heading bush for awhile Im taking them out with me to work on along with a seatainer full of timber and me tools!!!} as I understand it Tuart is pretty easy to bend and as this timber has been air drying for just on a year it should still contain enough moisture to make the moves it needs to without too much strain... one hopes :rolleyes:

The peices involved are keel {no bend} 9x6 x 20ft and the stem and stern peices will taper from 9x6 for the first {scarf end} 24inches down to 3 x 4 at the sheer overall length is stem 9ft6in stern post 7ft 6in... all final shaping done after the bend is in... question is at those sizes what quantity of water would be needed and the time frame? guesstimates are good here!

Then theres the bending for the frames and such but theyre no where near the size of these two peices small comparitively at 3x1 1/2inch

Finally I gotta say thanks for the idea with the webber! Brilliant!:cool:

Sorry about the inch thing but I have never been able to abide that metric stuff just doesnt compute with this ol mush packet :(

Oooh edited to add some info on the boat... its from the lines and offsets of a Swedish Koster double ender design named "Elly" who is 130 years old and still sailing in Nova Scotia... drawings by one Michael Mason of Mason Marine Nova Scotia :cool:

[Wild Dingo]

Okay heres a pic of said Elly just for clarification purposes ;)

[Wild Dingo]

Okay one more... but thats it okay?!!
This particular pic is what started the whole love affair with this boat and caused Michael Mason of Mason Marine in Nova Scotia to go and do the lines and offsets of her... stunning or what!!!
:cool:

Now imagine that flag getting a colorful Aussie change!! :cool:

mmmm will sorry cut it?? :rolleyes: I couldnt help meself honest!!:p

[Ian Runge]

You're out of my league with this. There is a steambending discussion at:

http://www.woodweb.com/knowledge_base/Steambending.html

or if you go to their search area:

http://www.woodweb.com/cgi-bin/search/search.cgi

and type in steam bending you'll get lots more info.

Ian R.

[seriph1]

"There is no lack of skill or talent that can't be compensated by a jig or machine"


Man I hope youre kidding

:)

[Andraax]

This is really interesting and I plan to start bending this weekend - I want to make a 'teddy bear' scale rocking chair for my sister and want to bend the rockers and the back rest.

How does Pine go in a steamer? :confused:

I want to use a panel for the back rest, should I bend it with the grain vertical and horizontal?

I only recently started wood working but so far have built a 4 poster bed and a book case with trimmings. Next is a solid coffee table. :D

[Bodgy]

Okay one more... but thats it okay?!!
This particular pic is what started the whole love affair with this boat and caused Michael Mason of Mason Marine in Nova Scotia to go and do the lines and offsets of her... stunning or what!!!
:cool:



Shane

She looks like a derivative of Slocum's 'Spray' reputed the first round the world single hander. She has the same lines and Spray was not a double ender either. If you're interested google on Joshua Slocum. His books OK too, (Saliing Alone Around the World) however he skips the less heroic bits, like his little spot of bother with the law and ages of consent.

Sorry, back to the benders....

[AlexS]

...his little spot of bother with the law and ages of consent.

....
Hmmmmm:rolleyes:

[Arron]

Yeah, back to bending. I have a copy of the 'Encyclopedia of Wood' which says Pinus radiata is 'not suitable for steam bending'. I havent tried it, but that sounds about right. I think laminating is the better technique for what you are wanting to make.

Arron

[mickp]

I reaslise that this is an old thread, but here is another link for steam bending solid timber

http://www.diynetwork.com/diy/ww_decorative_furnishings/article/0,2049,DIY_14441_2277640,00.html

I used this method to bend the backs of the chairs I made. pics of the chairs are posted (dining table & chairs)

[PatrickFrancis]

I have spent the last month trying to perfect this art. After trying every method I would recommend the following:
1. Do not use a PVC pipe for your steamer as it will melt. The best setup is either a metal pipe or timber box with a high power gas burner (cost $30), 5 gallon drum and connected with a radiator hose.
2. I found Silver Ash the best timber to use. Semi-dried is marginally better. Make sure the wood has a nice straight grain where you want to bend as any imperfections in the wood will definitely split.
3. Steam a little longer than 1 hour per inch with a good flow but no longer than 2 hours as the wood over cooks and tears.
4. Instead of trying to bend say a 30mm thick piece, I would highly recommend bending 3 x 10mm thick pieces and gluing them later. If you have to bend a thicker piece use a metal strap on the outer edge fastened at both ends as this prevents it coming apart i.e. only the inner edge compresses.
5. A bending radius of 10 times the thickness is achievable but I would recommend more like 12 - 15 times thickness if you want to get it right i.e. don't try anything less than a 150mm radius.
6. After trying various jigs it was well worth creating a simple press consisting of the two sides of the shape held together with metal brackets (spaced the width of your timber), with two threaded rods on top to screw down. Clamps don't have enough thread.
7. A drying rack consisting of a thick piece of mdf with a grid of dowell holes will be useful if you're doing several pieces.

Ok good luck and stick with it. The results are worth it.
4.

[rustynail]

The best way to bend radiata is to attach alabel saing, "Please stay straight" and then leave it in the sun. I'd rather steam bend a length of RSJ.

[Greg Ward]

Try coachwood.
Greg