Thread: Wood Movement in Table Top

Nothing?

It's hard to say, without some pix showing the fault and parts of the construction.

How large is the border? I'd typically expect the end-joints of the border pieces to fail before the table top rippled due to 'constraint'... although this depends on your construction.

So I suspect this 'ripple' is more likely independent boards cupping & bowing slightly. (Makes you wish true rift-sawn timber was a lot more affordable, eh?)

But your plans - and reasons - for replacing it seem sound.

The only suggestion I'd make would be to use buttons to fasten it to the rails rather than screws through slots, as they allow for larger degrees of movement in both directions (length x width) whereas screws in slots are pretty much restricted to the one direction of movement.

Hi John
If the timber is all matched, ie from the same log and the same cut, then it should not be such a problem, the expansion/movement rates will all be the same. But if one triangle decides to move more than the ones adjacent the joint will crack and any highly polished finish shows up things like that.
However if i was doing it......i would veneer it, even if you cut some "real" veneer yourself, not the hopelessly thin stuff you buy today. Use a hardwood ply for the substrate and a not too thick edge. The thicker you go the higher the chance of telegraphing. The best thing to do is solid timber edge in the profile so any movement of the edge doesn't effect the flat top. That does take some serious planning though.

Skew and Ewan,

Rift sawn? Its been many years since I heard that term, let alone saw any rift sawn timber. Mind you, the quarter sawn Vic Ash I get is very good quality. The timbers are straight and true in all directions. Usually I can dress a 25 mm sawn board to 22-23 mm and get a good finish on all sides. Also, the grain stands at, or very close to, right angles to the face of the board. I get it from Lazarides ... a bit more expensive per cube than others, but because it is such good quality, the yield is very high.

It is entirely possible Skew is right; that the very slight rippling is a function of the boards cupping or bowing ever so slightly. That part is no big deal, I am the only person who has noticed it. Can't send you a photo ... in Saudi Arabia right now.

The border is about 90 mm wide and the top is about 22 mm thick. There is no cracking at all in the triangles, or where they join each other. The cracking in the lacquer along the seam between the border and the remainder of the top is non existent in the centre of the sides, and begins about 3-400 mm from the centre. Then it gets continually worse as one moves towards the corners. All the seams around the breadboard ends are heavily cracked. There is no doubt the problem is caused by timber movement.

I guessed that all would be well without the border, but because I am still something of a novice wondered if someone out there had any experience or knowledge I lacked. Seems to me that the top is expanding from the centre of the top outwards in all four directions. This is only as we might expect, so a top without a border should be Ok so long as the top is fastened so it can grow and shrink a bit.

Ewan, I have veneered a few small pieces like cabinet doors, with a little difficulty. The mere thought of personally veneering a surface that big causes me to curl up in the foetal position and make sobbing noises. However, I have found a Brisbane supplier who will veneer your selected substrate with 2 mm veneers. So, I may consider than, but would prefer to make it from solid timber.

Thanks fellas!

There are several things working against you here:
1 Moisture content of timber vs changing atmospheric moisture content.
2 Timber movement properties of selected specie.
3 Suitability of design.

The moisture content will always be changing particularly if air conditioning or room heater are present.
Vic Ash would not rate as one of the more stable timbers.
This design would require an inherently more stable timber ie Aust Cedar or Huon Pine.

Rustynail,

Yes ... Vic Ash was a bad choice. I used it because it was tough, inexpensive, had a very straight grain when quarter cut and looked good stained mahogany. Now that I know a little about wood movement, I know it was not a good choice.

I use Red Cedar or Surian Cedar a fair bit and part of its attraction is very low movement, but it is soft.

Based on the available data (see extract from Jugo Ilic's AWR article below, which notes movement due to a 10% moisture change) Celery Top Pine looks likes it gives the best balance of low movement and reasonably high density/toughness. I recall it from my childhood when my father and grandfather used it for boat building ... but can I get it quarter sawn? The Banksias can be spectacular timber, but I have been unable to source it.

Timber	Density	Tangential	Radial
River Banksia	476	3.1	1
Aust Red Cedar	439	2	1.1
White Cedar	473	2.3	1.1
Silver Quandong	466	2.4	1.1
Red Banksia	618	4	1.1
Celery Top Pine	644	1.9	1.2
White Cheesewood	396	1.9	1.3
Northern Silky Oak	522	3.1	1.3
Kauri	461	1.7	1.4

So, now to discover if I can get quarter sawn celery top pine.