Thread: bending timber? help me anyone,please

Steve,

Do a search on steam bending, I seem to recall that somebody built a really good steam box recently and posted the details.

Himzo.

How you go about bending timber is largely dependent on the way the curve is to be viewed. Some options are:

1. Steam.
For thinner pieces of wood, you can hold them over steam and then gradually work it over a jig to attain the desired shape. You generally would need to repeat this process often on the one piece of timber. Don't expect this to work on the first run

2. Lamination
You can glue several strips of thinner timber together over a curved jig. Lots of clamps need for this one. Don't use too much glue - it just means a lot more glue needs to be squeezed out.

3. Kerfing
Make saw cuts at regular intervals across the grain on the back of the timber over the length of the required curve. Then pull the wood into the curve you require & put glue in the saw cuts to hold it together. There is a bit of a science to kerfing and I suggest you look it up on the Internet before attempting it. It does tend to give a segmented look though and isn't my favourite option.

4. Cheating
Cut a big piece of wood or even MDF into the shape you need - and then cover it with veneer. Yuk!

There are various books on the subject that I have seen around, a trip to the local library may turn a few up.
If you ask here you can get a feel for which are the good ones and ask the library to get them in for you.

Hi Steve,

Here is some legs for a table I'm making. They had to be laminated because the stock timber was only 55mm X 25mm. If I had thicker timber I'd have steam bent them.

Major, how about telling us what timber? I assume cold bent. Glue was?
I'm in the middle of a major (pardon!) bending exercise myself. By the time I'm finished there will be 16 bent peices, 6mm thick, 112 mm radius, steam bent.
Has anyone out there used the Garret Wade "gap filling" PVA that is supposed to be good for laminations, no creep and short clamp times? Sounds too good to be true, so I'm going to try it and see.
Steve the Jack --take a look in the archives for bending, there has been lots of communication including reccomended books
Jacko

big thanks to your reply's and instructions, really appreciated! if ya's ever need help with locks or related hardware, or just need a thought from a different mind to see the forrest the trees, feel free to give me a yell!

Cheers jacko! many thanks

On a somewhat related note: medieval shields were apparently, generally, made from plyed wood. The simple "heater" shield shape that most folk are aware of has a shallow curve horizontally. I can see how to do that, by bending sheets over a pipe or barrel or tree or whatever. Other 15th century shields get a little bit funkier though, and usually have a curved section in the middle, giving it a "W" profile. Something like this one.

Anyone like to offer clues on how I could tackle something like that?

Originally Posted by jacko

Major, how about telling us what timber? I assume cold bent. Glue was?
I'm in the middle of a major (pardon!) bending exercise myself. By the time I'm finished there will be 16 bent peices, 6mm thick, 112 mm radius, steam bent.
Has anyone out there used the Garret Wade "gap filling" PVA that is supposed to be good for laminations, no creep and short clamp times? Sounds too good to be true, so I'm going to try it and see.
Steve the Jack --take a look in the archives for bending, there has been lots of communication including reccomended books
Jacko

Hi ya jacko!

I was given aprox 1.3 m³ of New Guniea Rosewood that were all 50mm or less in width & up to 40mm thick although 85% is 50 X 25mm. For this lamination I used Garrett Wade Slow set glue as it afforded me enough time to get it all together.
I have been using the Garrett Wade 202 gap filling glue for about 5 or 6 years & it's excellent , just remember open time is quite short with the 202 glue. Another hint if you are going to use the 202 glue is DO NOT OVER-TIGHTEN your clamps, so make sure your bending forms are almost perfect & you don't need to over-tighten your clamps to draw everything together otherwise you end up with glue starved laminations :eek:

Well here goes nothing! This is am image of my gluing jig (seperate from the bending jig) \. Bends went well with some 15 degrees of spring back, hopefully somewhat less after lamination. Only three more to go (if this works!)

Well some good suggestions here... Its rare that I would stick my beak in and offer a comment since I find most of you blokes have way more furniture building knowhow than I do {Note here: That is changin! }... but with steam bending TIMBER and here Im thinking steve the jack up there means TIMBER not laminations or thin strips of timber theres definantly a method to the madness and since Im about the maddest buggar I know I will give me two bobs worth.

So lets say Steves got some 1in x 1in Jarrah or other hardwood for an example...

You will need a steam box this is a wooden box pine generally nailed together one end closed the other open... the open end you will stuff with rags or such so some steam and water will escape... the other is closed but with access for a tube that is led from a sealed copper or some such water holding thingy that you will have over a fire or hotplate

Okay lets say you want to do 4 peices of that 1in x 1in and theyre 10ft long... so you will make your box say 4in High x 10in Wide by 12ft Long... why? so the steam has room to move flow around that timber and get it good and steamed up!

anyway inside the box you will have made some form of rack for the timber to lay on while its being steamed... some fellas use rebar or steel bars some use timber sticks tacked to the box so the timber to be steamed lays on it so its touching a stick say every couple of feet or so so it has gaps throughout its length for the steam to flow around it... note here you can make the box as big as you like and make racks to suit the number and sizes of timber your going to steam... you can layer the timber inside the box... this isnt usually advised simply cause most blokes have only got two hands and two feets and so can only carry and run so many times before the timber in the box is cool... dont over do it!

so okay youve got your timber in there on sticks waiting so go ahead block and the other end up with rags why rags? you want that steam as it turns into water to escape firstly and by having some air movemnt through the box the steam will completely go around the timber inside... it will also act like a valve releasing pent up steam... nothing worse than openin up a steam box thats got a tight seal and getting a face full of burning hot steam!!! not a good look!... now get all kids and others out of harms way cause steam is ruddy hot and can burn and get the copper/kettle or whatever is holding your water to boilin... now you want a steady boil not boil out then refil with cold water but a steady boil

Some fellas get real technical and make up whizgang whoopty do steaming rigs with vents and valves and such and thats fine but the above works well... an added thing you may like to think about if your doing a fair bit of steaming is to lay the steam box on an incline with one side lower so you get a v at the lower edge of the box and when your stuffing your rags in stuff a tube into that v directing the tube back to the copper or whatever your waters boilin away in or just to one side out of the way so that when your taking the rags and timber out you dont get your tootsies burnt by the scalding water!

1in thick timber should take around 20mins to become pliable enough to bend to almost any shape... its dependant on thickness of the timber not length... so the 1in x 1in peice above would be ready to take out in around 20min of solid steam going through the box... now while that timbers been broilin away in the steam box you have been busy getting your mould made right? cause now that suckers good and steamed you grab your welding gloves yank out the rags and slide out the timber run to the mould and quick as slick bend it around clamping as you go... now let dry... there will be a certain amount of spring back but its minimal if your measurements have been right on the money with the mould and the timber has been held tight to the mould till dry

Oh and only do enough that you have prepared enough for! Dont steam more timber than you can handle at one time.. a couple of practice runs will show you how much

This method has been used for donkeys years by boat builders...

On another note... Scooby? A gentle safety nudge here mate ... That steam process you describe Id not suggest anyone use simply because its unsafe mate steam BURNS! and moving a hot and getting hotter peice of timber over a hot and getting hotter pot of boilin water WILL BURN... Ive watched people do that and end up with seared fingers and hands... you must have boiling water to make the steam thus burns are more than possible using the method suggested. :eek:

Think SAFETY!!.

Here's a couple of ideas on bending as I do both steam and lamination bending.

Bending, mostly I use 1/8" x 1" strips of Ash for chair pieces I make that turn 180 degrees (makes a complete U). I use 8 strips, gluing between each strip then clamp it down to a form I have. I put a laquer finish on the form to help keep it from sticking and use waxed paper around my part before clamping. Starting on the center, I work around to each end, clamping every 2" - 3". Force the pieces to stay aligned while gluing. Once dry, trim up the edges even and cut to length.

As far as steaming goes, I made a steamer out of 4" PVC sewer pipe. I've got some 2', 3', & 4' sections, a Tee fitting and 2 end caps. I screwed it together so I can change the length at any time to handle different wood lengths. I made a cradle it sits in, and I place that across some sawhorses for a stand. I bored some holes in the bottom for draining condensed water and a row on each side to slide some bronze rods through (for the wood to sit on). I tried to use things that wouldn't rust. I use a propane burner from a lobster cooker, a 2 gallon metal gas can to hold the water and some flexible vent pipe to carry the steam from the gas can to the steamer. Seems like air dried Ash with about 15-20 percent moisture content steams best. You have little time once it comes out of the steamer, so have good gloves and your form and clamps ready and work fast getting it clamped down. You want to use air dried wood to steam bend (again, based on experience), as kiln dried lumber has already taken a set and won't steam bend well. Either will work for laminate bending.

Around here, the best wood to bend is Ash (based on my experience) followed by elm. Other wood will bend but not as well or consistently as these.

Hope this helps.

hi i am in year 12 and new to this site as well. I am doing design and technology as one of my projects and researched methads of bending wood. Here is a useful link http://www.megspace.com/lifestyles/njmarine/Steam.html

I have played around with steam bending but I am definitely not an expert. I was inspired by a video on the building of the (replica) ship "Enterprize", which was the ship that founded Melbourne. I don't know how you'd get a copy of the video, but they do tours of Port Phillip Bay on the boat so maybe if you phone the Enterprize office and ask about the video they can sell you one. It shows long strips of Jarrah being steam bent to build the boat. http://www.enterprize.com.au/index.htm

When it comes to steam bending, it's important to clarify what is happening-

Because water is involved, it's easy to assume that the wood becomes flexible because it is becoming soggy, or slippery, or moist, etc. In the same way that carboard turns mushy when it's wet, it's easy to assume that that is what is happening with wood.

In actualy fact it's more complicated that that, and it's important to understand that to steam-bend timber you need water and heat. Wood is a natural plastic, and when heated over 100 degrees with water a chemical reaction takes place allowing the wood to become more flexible. For the wood to bend properly, enough time has to be allowed for the water to soak into the full depth of the timber, and for the inside of the timber to reach over 100 degrees.

It's also important to consider bracing your timber. The inside of a curve is shorter than the outside, so when you bend a piece of straight timber the 2 sides which were the same length will then be slightly different lengths. It is important to acheive this by squeezing the inside and not by stretching the outside. If the wood fibres are stretched too much they will tear and your wood will break in half. Many people who steam bend timber will use a brace which keeps the outside length of the timber a constant length and forces the inside to be compressed, which allows the timber to be bent much more tightly without breaking.

Good luck.