Thread: Building Wegner's "The Chair" .

Originally Posted by derekcohen

I reached some of the coping earlier than I expected. Here is how it went ..

Hi Derek,

Wonderful work and great progress.

You mention that you've removed a bit more waste along the cheek than that at the coped ends. I can't work out from your pictures, but is there enough of the 'coped ends' to accommodate the later rounding of the sides without venturing into the cheek areas that have been recessed more?

Or am I thinking too much into it and it won't be a problem?

Cheers,
Justin

H iJustin

The rounding over takes place on the other edges. The shoulders are left untouched.

Regards from Perth

Derek

Originally Posted by pmcgee

...What would you end up with if this chair was made from green wood - say oak? .......

A twisted, ugly, mess, perhaps?

Chair-making using wood at two different moisture levels is a time-honoured technique for making 'stick' chairs. I've had a go at it & it takes some fine judgement to get it just right - a round hole in a green chair leg doesn't shrink so much as distort. You probably need to choose your species wisely, too - many of our woods are a lot more fissile than Hickory & Ash, so it would be a lottery if you didn't know what you were doing...

Cheers,

Originally Posted by derekcohen

TT, I'd like to hear more about hide glue and Jarrah as a combination. Your comments earlier were the first I had heard of hide glue breaking down in the presence of Jarrah. Of course, I would like to hear the comments of others as well.

My intension was to use hide glue. I must admit that I am a fairly recent convert to this, with only a few years under my belt. Until now I had relied on either yellow or epoxy.

I have been thinking increasingly about using epoxy as it is better with flex. However the need to repair a joint at some stage (witness the loose joints of my original) is a warning to allow for this - hence the prefeence for hide glue.

Thoughts?......

Derek - going on my hazy memory of Chemistry 101 & Biochem, I think hide glue is at risk from any acidic wood, since low pH has the capacity to denature proteins. However, that should only be a problem if the glue is moist, since chemical reactions of this nature can only occur in solution. There are, as you know, several reasons why hide glue fails, & determining just which one is operating in a given situation would require some fancy analysis, I think.

I've been musing about which glue I'd reach for, for this chair of yours, over the last day or two. Frankly, I don't think any glue is going to keep those rail joints intact in the medium to long haul. The fact that you don't see too many of these chairs with sound joints reinforces my opinion that it is an engineering problem, not a glue problem. The force per unit area applied to the joints of this chair when someone of reasonable bulk leans back on it, is likely to exceed the tensile strength of both wood and glue, so something is bound to give, sooner or later.

Hide glue is very strong stuff in a well-made joint, but over time it does become brittle, so I initially thought I would not use it in this instance. Epoxy has a bit more give, but would cause more problems if repairs are needed. But the only glue that isn't a problem in that regard is hide glue, so p'raps it could be the best choice after all.

Hard call......

Cheers,

For TT,

Don't go to Dereks house. You will have uncontrollable tool envy and it will cost you a fortune. Take this on experience.

Cheers
Yowie

Sorry I missed your question about Hide glue Derek.

Other have nailed it - for whatever reason (age, biological breakdown, acidic attack from sap in the Jarrah timber) hide glue in jarrah chair joints always seem to go brittle and crumble...and the joints come loose.

It was for this reason that mechanically engineered sound joints are handy.

After trialling several glues over the years, (PVA, Urea Formaldehyde, & epoxy) we ended up settling on the epoxy.

Epoxy seems inert to acidic attack, from the sap in the wood.

It also seems to form a bond stronger than the parent material surrounding it.

I've long been a fan of both a mechanically engineered strong joint (aka the blind stop haunched M & T with blind pinned & pelleted dowel) & the use of Epoxy resin.

Its movement within the joint once the glue lets go - rocking back and forth that compresses the tenons usually and make the joint "work loose"... and anything that can prevent that movement for the glue to fail - has to be worth the effort in my book. when I machine joints - it not by hand as you have done... its off tungsten saws, and mortice chiseled. I usually test cut and hand fit "extra" tenons when setting up the machine....so that joints are a tight hand fit (movement free)....

Then I epoxy the joint at final fit up.

By stop pin doweling them I try to prevent the tenon being able to be pulled out or worked loose.

My preference is to create something that - if broken - it had to be by a truck backing over it and its then time to throw it out... rather than something your re guing and cramping every 5 or 10 years and each subsequent failure and restoration compresses the timber in the tenons from all the rocking / racking within the joint before it fails.... and needs extra glue to fill the increasing sized voids on the joint each successive time...

Make it once and make it right is I guess my design and manufacture ethos.

Others may well have evolved a different ethos or even different methods of attaining the same thing.

Jarrah pretty much only occurs naturally between Yanchep National Park - down to Albany way east about as far as Narrogin (12 odd km's east of there out the Harrismisth road) and it disappears where the Wandoo starts.

These soils are generally the Darling Scarp granits and also the bauxite gravels - as wellas much of the swan coastal plain, etc.

Jarrah trees are a rather unique eucalypt - in that they thrive despite the poor soils and rainfall - they are highly adapted to their environment compared to a lot of other forests and forest species around the world. A lot of other species wouldn't do at all well in the conditions that Jarrahh seems to thrive (including frequent fires).

One of the unique conditions is that these soils tend to be deep leached gutless grey sandy soils, once under the sea... (think white beach sands).

One major characteristic is that they are on the acidic side of the neutral Ph scale. As a result the sap in the tree is slightly acidic.

When you season the timber and remove the free moisture (sap) as well as the inter-cellular moisture and intra - cellular moisture, down to EMC (Equilibrium Moisture Content) ~ 12% for Swan Coastal plain - the remaining 12% moisture is the same acidity as the soil in which the tree was grown.

Thats 12% acidic sap does over time react with various glues in various ways.

The hide glues seem to go brittle and crumble.

Likewise my experience with U/F 62 (Urea Formadehyde)

My results from epoxy resin, which is seemingly inert to weak acid attack that Jarrah sap represents - seems to produce joints where the glue is stronger than the parent material surrounding it.

Failures seem invariably to be of the timber surroundingthe joint rather than the joint and glue itself.

It's the system I prefer.

The "problem" with this "philosophy" is that it doesn't at all compare well with costs/time of mass production methods that on the surface appear to be identical...

So finger jointed cabinet doors joints off the machine for example, cured in 5 minutes with electrically cured glues - allow mas produced doors to be glued cramped and released ready for sanding in say an hour...

Compared to 72 hour epoxy joints that I would cramp for 3 days!

It's impossible to be cost competitive with such mass production methods when most potential customers cannot discern any difference and aren't often prepared to pay any more for a better constructed product, in which they can't see any visible difference unless they were physically there when it was assembled to see the engineered joints & quality glues.

Eventually I worked out that to be cost competitive in cabinet making, with sold timber doors - (most people replace their kitchen cabinets about every 6-7 years now) - that I would buy in mass priduced solid timber cabinet doors for kitchens, and only make my blind haunch-ed M&T stop pinned and pelleted fielded panel timber doors for heirloom type furniture (and solid timber chairs).

In essence I got "picky" about which projects I went to that length of trouble on. No point on something that the owner will get tired of it like a kitchen and toss it out for a new Ikea Flat pack one in 6 or 7 years!





I'd make my own doors for this type of furniture and go to the extremes.

Whereas for Kitchen work like this



I'd do everything bar the doors - which I'd buy in from mass producers.

The mass produced cabinet doors were about half my cost of production of a solid timber furniture door.

You just work out what works for you at the end of the day when your tryoing to survive in business.

It seems cost of production is frequently the arbiter of how things get done often...when trying to make a living as opposed to enjoying a hobby whgere time and materials costs might be immaterial.

Agencies like western power don't seem to have a "hobby philosophy" when your 3.5K power bill for 3 months kiln drying timber is due!. LOL

You do what you have too.

I could make a reasonable wage making kitchen cabinets, vanities and robes etc... whereas my return on labor for fine solid timber furniture I once worked out at $3 an hour!

I far preferred making solid timber furniture...thats what I loved to do - making kicthen cabinets was what I HAD to do to keep the doors open.

In a small town popn 500 - you tend to get asked to do everything Milling, Timber, Carpentry, Joinery, Cabinets and Furniture.

Sorry I wandered off topic there!.

Cheers.

Here is the next instalment in building The Chair:

http://www.inthewoodshop.com/Furnitu...8Part1%29.html

As always, comments are welcomed.

Regards from Perth

Derek

Derek

I have only just come upon this thread, so forgive me for any repeats as I have not read all posts.

Congratulations for your attempt at a first chair I am myself a bit of a fan of Hans Wegners designs. If this was my work I may not have done a simple reproduction but made efforts to improve the chair, Particularly in strengthening the joints and probably changes to reduce the amount of wood used. However there is nothing wrong in a pure reproduction for the sake of experience.

My suggestions for the joints would be to consider differential moisture content of the two elements, and the use of modified hide glue. This would permit a very strong joint once the moisture content has equalised, but I suggest a trial first, as it is easy to overdo this and split the leg if there is a large difference in moisture content, this should not present any real problem if you are using wood at a low moisture content.
The modified hide glue ( such as Titebonds Traditional ) is very useful as it has a long open time and its lubrication qualities permit a tighter joint as it does not tend to seize up on assembly like using PVA. Assembly can also be improved by sizing the joint first with a 10% strength hide glue in the mortice.

Sam Maloof used this technique using lamps as a heat source on tenons and hot sand has also been used to lower the tenon moisture content

I have only converted to using hide glue in the last couple of years, and now use PVA much less than previously. I would like to find out more regarding the use of Hide glue with Jarrah and perhaps other species with low ph, but I guess the saving grace is that it should be a lot simpler to repair than other glues. Geoff Hannah I believe went back to using hide glue exclusively many years ago after using PVA for years early in his career.

Other, and perhaps more courageous, options are : blind mortises with fox wedges, or some of the traditional Chinese joints using blind dovetails.

Have you considered using a fishtail carving chisel ( say 8mm around a # 5 or #7 sweep ) for coping the tenon shoulders, I think this would provide a tighter shoulder ( therefore stronger joint ) than a straight chisel

Regards

.... for whatever reason (age, biological breakdown, acidic attack from sap in the Jarrah timber) hide glue in jarrah chair joints always seem to go brittle and crumble...and the joints come loose.

It was for this reason that mechanically engineered sound joints are handy.

After trialling several glues over the years, (PVA, Urea Formaldehyde, & epoxy) we ended up settling on the epoxy.

Epoxy seems inert to acidic attack, from the sap in the wood.

It also seems to form a bond stronger than the parent material surrounding it....

Hi TT

Thanks again for such a detailed reply. (And I enjoy the side excursions as well .... nice pieces!)

The choice of glue is always on my mind, although there is quite a way to go before I get to use this. It sounds like epoxy is the way to go as (1) it is less likely to break down, and (2) it has some flex, and this is needed in a leg join.

My only concern is repair - which is inevitable down the track. Even sitting quietly on the seat will create some flex. My experience is with two-pack West Systems epoxy. The good thing is that one can add new epoxy over old epoxy, which you can also do with hide glue but not with yellow/white glues. Epoxy is also removable with heat, however this is not really practical with a failing joint. I suppose one can soak it in acetone (although how this will affect the finish I shudder to think). What other methods are there?

Regards from Perth

Derek

You can pare it off in thin shavings with a super sharp chisel, or sand it off on a linisher if you can get access to the tenon for e.g. - a little bit harder inside a mortice tho.

TT, I meant to ask whether your experience with hide includes, as Basil mentioned, Titebond hide glue?

And of course to all, is Titebond hide glue (which I use) a different composition to the hide glue one might mix in the workshop?

Regards from Perth

Derek

Originally Posted by derekcohen

.....And of course to all, is Titebond hide glue (which I use) a different composition to the hide glue one might mix in the workshop? ...

Yes.
Unless you are in the habit of adding urea to your 'pearls'. See here

But I suspect they add more than just urea to the liquid stuff. It must contain an anti-bacteria/lfungal agent, too, or it would become a festering culture of micro-organisms soon after the first time it was opened. Try watering down some home-brewed H.G. and letting it sit in a bottle for a few days....

Cheers,

Originally Posted by IanW

Yes.
Unless you are in the habit of adding urea to your 'pearls'. See here

But I suspect they add more than just urea to the liquid stuff. It must contain an anti-bacteria/lfungal agent, too, or it would become a festering culture of micro-organisms soon after the first time it was opened. Try watering down some home-brewed H.G. and letting it sit in a bottle for a few days....

Cheers,

Another source of info is the book " Hide Glue by Stephen A Shepherd " which has all sorts of tips on the use of hide glue and its modification to suit differing applications.

Regards

Thanks Basil. I have been in touch with Stephen (Shepherd).

I think that epoxy remains the best choice.

Regards from Perth

Derek