woodbending-msg

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wood-bending-msg - 2/6/11

Period and modern techniques for bending wood.

KEYWORDS: wood woodbending bending steambending steaming period rattan warp tools curving

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NOTICE -

This file is a collection of various messages having a common theme that I have collected from my reading of the various computer networks. Some messages date back to 1989, some may be as recent as yesterday.

This file is part of a collection of files called Stefan's Florilegium. These files are available on the Internet at: http://www.florilegium.org

I have done a limited amount of editing. Messages having to do with separate topics were sometimes split into different files and sometimes extraneous information was removed. For instance, the message IDs were removed to save space and remove clutter.

The comments made in these messages are not necessarily my viewpoints. I make no claims as to the accuracy of the information given by the individual authors.

Please respect the time and efforts of those who have written these messages. The copyright status of these messages is unclear at this time. If information is published from these messages, please give credit to the originator(s).

Thank you,

Mark S. Harris AKA: THLord Stefan li Rous

Stefan at florilegium.org

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From: powers at colon.cis.ohio-state.edu (william thomas powers)

Newsgroups: rec.org.sca

Subject: Re: steam bending (was Re: Making Portable SCA Furniture)

Date: 12 Aug 1997 19:00:21 -0400

Organization: The Ohio State University, Department of Computer and Information Science

>I had a couple of questions on steam bending...

>For smallish projects (such as in this book) how much room does a steam

>box (?) take up? What is a good source for information on how to

>construct such a thing?

The steam box will probably be 4-6" square and 6' long---it can be made

from wood, plywood, pvc pipe, thinwall metal pipe. since it is never

under pressure and doesn't exceed 212 degree F all it has to do is

hold the piece of wood and allow steam to circulate. When not in use

you can stand it in a corner or up in the rafters.

The Woodwrights series covers steaming. There was an extensive article in

Fine Woodworking magazine back in the '70s which is sure to be in

reprint in one of their compilations. The US Department of Agriculture

Wood Handbook has a section on steambending. Many traditional woodworking

books will cover it. Look under "bending" and "steam bending" in the index.

(I prefer the Fine Woodworking article myself)

>When did it start being used (in England and Northern Europe)?

I don't know. My sources are basically to look at a piece of furniture

and see if it was constructed using bent rather than hewn or sawn wood.

Not as hard as you may think in person by following the grain, in pictures

it is a guess based on construction and design details---you usually

design for the techniques you are familiar with. Note Oak is one of the

better steam bending woods with beech close behind---both well represented

in nothern Europe/england. One might also check when barrels were

constructed with heat bent staves.

>My understanding is that Henry the VIII's fleet was made using

>steam boxes, but I am told that the Viking ships were not, each

>plank being hewn to shape. Any thoughts or knowledge out there

>about either of these alledged facts?

Not my area of research.

>Thanks for any information you can give me.

>Robert

>Real Men change diapers

Been there, done that, ruined several shirts....

wilelm the smith who works wood as an adjunct to smithing and as a means

of providing objects for a more period existance.

Subject: [Fwd: Re: *WH* War cross]

Date: Tue, 07 Apr 1998 14:59:35 -0400

From: rmhowe <magnusm at ncsu.edu>

Organization: Windmaster's Hill, Atlantia, and the GDH

To: stefan at texas.net

Dan Mackison & Hilda Jarvis wrote:

> Poster: Dan Mackison & Hilda Jarvis <g7f3h7gv at coastalnet.com>

> Reading the latest Oak has brought back a polearm design idea I once

> had. The idea also springs from once hearing that rattan can be bent

> with loving application of steam.

> Before I spend a lot on money I don't have building a rig to steam

> rattan I thought I would check to see if anyone else out there had such

> a rig or had otherwise attempted to warp rattan.

> Obviously, alternative methods to steam would also be gladly tried.

> What I am trying to do is take two pieces of rattan, 54" and 18". I

> split the shorter piece and steam/bend/warp it around the longer piece

> 18" from one end and secure it in place to form something like a cross.

> Thomas

Well, here in the library I have a book called Rattan Furniture

A Home Craftsman's Guide by Max and Charlotte Alth, 1979

ISBN 0-8015-4788-1

It says you can get an 18" diameter bend out of 1 1/4 or a 26"

diameter bend out of 1 1/2".

But:

It sounds like you are trying to make a short U bend in two

halves of the 18" piece at their center, while leaving them relatively

straight to be joined back together.

Commercially they would employ a steambox and perhaps hydraulic presses.

However, thick rattan can be bent by wetting it, clamping it in a vise

and heating it with a propane torch while repeatedly rewetting it with

a wet paint brush. You have to overbend. For furniture they build

bending fixtures to fit it into first out of wood blocks and panels.

In this case you might want to try binding the ends of the two halfs

with wire while putting the whole one between them. Then as you heat

them and they bend applying clamps, a rope twisted with a stick (spanish

windlass), clamps, etc. until you get it as near as you can.

The book suggests repeated heating and rewetting. Expect the outside

with silicon to fall off when it is bent. Charring can be sanded off.

A good steambox may be built out of a large plastic drain pipe 4-6"

with a hole in the middle and a cap on one end, a rag in the other.

One mounts this on an x trestle high enough to run a heater hose

down to a spout on a metal gasoline can filled with water sitting on

a gas cooker (like the kind you boil seafood on at campsites). Fine

Woodworking has plans for them. Norm baby also has had one on the New

Yankee Workshop. The heater hose fits in the hole in the middle of the

pipe. One steams about 1 hour per inch of thickness in most hardwoods.

Generally the fixtures overbend the wood a bit. It will spring back

a little when cooled and dried.

Magnus, repository of obscure materials and processes

Subject: Re: [Fwd: Re: *WH* War cross]

Date: Wed, 08 Apr 1998 14:46:55 -0400

From: rmhowe <magnusm at ncsu.edu>

Organization: Windmaster's Hill, Atlantia, and the GDH

To: stefan at texas.net

> Greetings Magnus,

> I have some wood projects that look like steam bending will be

> needed. Many medieval wheelbarrow handles appear to be smooth

> curves, not straight for instance. Your example steamer is only

> 4 to 6 in diameter though. This seems to imply that you steam

> the wood first and then bend it and hold it as it dries. What

> if you have to steam it again to bend it some more afterwards?

> You are out of luck?

> Stefan li Rous

(Put a heavy enough weight in the middle and steel will flex. ;) )

But:

In bygone times wood was often selected for the shapes it was

in right on the tree, split in two halves and shaped accordingly.

One example would be cruck framed buildings, another would be

whiteoaking where the curves of the oak trees are used for ship

framing. Another would be the selection of various pieces of

trees for items like pieces in viking wagons or ship framing.

The World of the Vikings CD shows this use in the wagon

reproductions it depicts in process. Green wood could also be

shaped by tying as it grows in the tree or by bending into

forms before it dries. Remove the bark first. It is easy

when it is green - difficult later. Topiary would be a good

example of bending living wood. Many cultures like the

Europeans have a long tradition of copicing in which trimming

is continuously done to produce both hedges and usable wood

for withes for hurdling (fencemaking), basketry, the woven

wood sticks for wattle and daub between the framing in timber

framed buildings, etc. Mongols harvest the wood for their yurts

at regulated periods for the same reason.

Yesterday we discussed bending rattan with a propane torch -

alternately heating it and reapplying moisture with a wet

brush. I have also seen some ash bent that way - sheperd's

crooks for example. They splintered at the outside some and had

the outside of the bend flattened where they had been trimmed.

Of course these would have been bent wet / and or green.

Bending is basicly done in two ways with seasoned wood - either by

steaming or by laminating (lamininating can also be done in vacuum

bags on forms - particularly good for curved laminations out of

veneer for example. Very thin pieces can be heated in very hot

water and bent in a form - chair slats for example. Boiling too

long can reduce the properties of the lignin.

Mostly people use a wood like ash to steam bend. It has excellent

bending properties. Some woods don't bend at all well. Wood is

composed of cellulose fibers and lignin which is the glue that

holds it together. Wood cells are rather like long square

honeycombs. When steamed the lignin softens and the cells can move

a little. The outside must stretch, the inside compress, the center

remains pretty much the same. Some woods can't take the strain and

compression. Woods like ash and oak have very open grain and this

helps the steaming. Ash is also very tough - baseball bats and

tool handles for example.

In the case of hardwood bent for furniture both fixtures and jigs

are generally made for bending. A fixture is something that

does not move - like a frame, or a plywood board with curved

shapes/blocks screwed and glued to it. A jig usually has movable

parts and sometimes the two are used together. Below is a

common jig to bend fairly thick pieces. It would probably be

placed in a frame upon being bent.

Handle attached Wood piece to be bent End cap attached

to steel strap between handle and end with screws.

with screws cap with steel strap to Bears against end

\/ outside of bend of wood piece.

---------------|----------------------------|---|

__|_________|__|____________________________|_|_|

Steel strap is used to control the outside splintering of wood.

Very little space between the wood and the endcap.

Expect some failures. Split (riven) wood works best. Trying to

bend wood with poor grain not running lengthwise is most likely

going to fail.

Orientals sometime bend unseasoned fresh wood by placing it

in beds of hot ashes/coals and then bending it with jigs made of

poles with pairs of large dowels and / or forked trunks and then

tying it off once it is bent with twisted bark off the same pole.

Yurt roof wheels for example might be formed this way and then

cross lapped and bound where the semicircles join. I have an

example of a one piece yurt ring bent in a circle unjoined as yet

in a picture. Drilled for the roof poles later. I also have

a picture of a Mongol using a steam box to bend side poles for

a yurt.

Bending poles / forks for wood or metal often look like this:

________________________________________________

________________________________________________|

| | | |

|_| |_| wood or metal dowels.

Or make a 1 1/2" thick plywood form with holes you can insert large

dowels in for example. Kinda like a pegboard, and adjustable and

reusable.

If you look in National Geographic June 1929 page 684 you will see

a picture of: "Little Trees are Wrought into Cart Wheels -

These wheelwrights at a village near Aksu heat poplar saplings in

ashes, bend them into semicircles by twisting bark ropes attached

to the ends like bowstrings, and lash them into pairs. Though the

hoops thus made tend to be more elliptical than round and are not

tired with metal, they serve excellently for traffic on roads of

earth. More expensive seasoned wood, studded with nails, is used

for vehicles intended for use on long journeys."

You might make a larger steam bending box by building a box

out of ordinary 1 x lumber.

________________________________________________________

||------------------------------------------------------| //

|| dowels to place wood on go through sides //

|| o o o o o o o //

||______ ______________________________________________//

|------| |--------------------------------------------|

Hole for steam hose. Hinged door - not tight.

Or you can make the steamer out of a piece of heavy drain

pipe plastic with a cap on one end and a rag in the other,

with a hole to take a radiator hose with a steel gas can

attached to it. The gas can is filled with water and sits

on a propane burner such as you might use outside to cook

seafood. The pipe sits high on a sawbuck-like or trestle

frame.

To answer your question. Bending is generally done in one

operation, not multiples. Usually starting with seasoned

wood. In the case of fixtures it is also often held in

place with wedges between pairs of blocks or dowels until

it dries. Wedges are usually used in oppositely pointed

pairs to get a parallel surface. You bang the opposite fat

ends toward each other. Generally when the wood dries, the

wedges become loose. Allow about 1 hour per inch of wood

thickness for your steaming time.

Alternately - one can rip wood into strips and with glue

and clamps bend it in multiple layers around premade forms

of various shapes. Spiral staircases would be an example.

Complex twisting shapes, compound bends (bends in more than

one direction) are all possible. By laminating up sheets of

veneer you can make drum cases around round forms. Piano

cases are made in a similar fashion.

There are many excellent articles in woodworking magazines

and books - particulary those put out by Taunton Press who

publish Fine Woodworking. In fact they have a couple of

books on wood bending. One is by Tage Frid.

TAGE FRID TEACHES WOODWORKING: BOOK 2 SHAPING, VENEERING,

FINISHING. ISBN 0-918804-11-6

Another is FINE WOODWORKING ON BENDING WOOD

ISBN 0-918804-29-9 A compilation of many articles.

Fine Woodworking has been published for more than 20 years

now and they offer an index. Some of us have complete sets.

Unfortunately in all that time they have paid very little

attention to Medieval Furniture - most woodworking magazines

haven't.

http://www.taunton.com/index.html

You might also look at books on Green Woodworking - which

generally cover chairs (bodgering) and the lathes used

(and built) in the woods.

Exellent examples would be books by Drew Langsner like

Country Woodcraft, Handmade, and Green Woodworking,

Make A Chair from a Tree by John D. Alexander, Jr.,

and Woodland Crafts in Britain by H. L. Edlin.

Langsner is an outstanding primitive woodworker. Drew

predates Roy Underhill and still teaches and writes.

For books on Windsor and Welsh chairs which have bent

forms you might try Windsor Chairmaking by Moser and

How to Make a Windsor Chair by Michael Dunbar. They

cover bending.

Magnus

Date: Fri, 25 Feb 2000 19:52:26 -0800 (PST)

From: Christopher Douglas Buckley <cbuckley at gladstone.uoregon.edu>

To: sca-arts at raven.cc.ukans.edu

Subject: Re: steam bending wood

The most basic way to do it is to put the *thin* strips of wood to

be laminated into a bath of boiling water, over heat. (My father, a

luthier, used a coleman stove) Make sure the wood is NOT touching the

bottom of the bath, as this will scorch and discolor the wood. (One can

come up with a jerry-rigged system of holding it suspended in the water...

I think Dad used thin, smooth chain, hung from something.) After that's

been boiling for about ten minutes, take the wood out (carefully, it's

really hot... duh.) and test its flexibility... it should be able to bend

about twice as far as the final product is to bend. If it doesn't, set it

in the bath for longer.

If it does, you now put it into the mold. The mold is usually a

block of wood which has been cut in two, the cut being the shape of the

bend. (In the case of lutherie, it looks like the bust, waist, and hips

of the guitar... yes, those are actually what they call them.)

The contact surfaces of the blocks (where the newly-boiled wood is

going to fit) ought to have sheet metal nailed to them, so that the grain

of the blocks doesn't damage the grain of the product. There ought to be

holes drilled through the two sides of the mold, for the purpose of

clamping. (It should make sense where holes and clamps go, depending on

the shape you're trying to get.)

This has been long, but that's the basic gist of it. If you have

any further questions, I may be able to help, but maybe not.

Fr. Nathan O'Ceile

Prior, Our Lady of the Cross

Adiantum, An Tir