wood movement

[steamboat]

Hello all. Please can someone advise me.

I have been building myself a new work bench, one that will hopefully last for at least my lifetime. The top is constructed out of two layers of 25mm Beech, the first layer is made up of 5’ boards and the top layer are around 7’ so they over lap, the two layers are then glued together. Unfortunately the moisture content of the two layers where different and the top has started curling up at the sides so there is about a 5mm difference between the middle and the sides, and the joints between the boards is opening up, around 1mm.
Should I make do with what I have, cut the top through the joints re surface them and glue it back together, glue another layer to make three layers and then flatten the top again or a combination of the above?
Any comments gratefully received
Steve B

 

[big soft moose]

i know it aint what you want to hear , but imo you'd be best to take the whole lot apart and cut the beech insto strips theb laminate them together , end grain upwards - like a giant chopping board.

olly -opj- built a nice beech bench last year - if you search his threads you should find a wip

 

[SammyP64]

i would have allowed the timber to rest for quite a while in your work shop if i was you, so im with moose on pulling it apart,
but then i would either laminate it like the core of lamin board (after a fair amound of drying and re surfcaing inad shaping) or i would do what you have done,

Its always best to let wood dry out for a while in its new surroundings,


Sammy

 

[ondablade]

Beech really is frisky stuff it seems Steve. The kiln dried and very clean 50mm stuff i bought for my bench has been in the workshop since January now, and while it has pretty much stayed put since after a few weeks it would have won a gymnastics medal prior to that. It's split a little off the ends in one or two places too. Heaven knows what a more characterful/native grade would be like.

The boards are about 10 in wide, and have cupped about 1/4 in in the centre - so the time to equilibriate is definitely important.

I'll be ripping them down to make about 1 1/2in boards to stand on edge to laminate my top (that delivers what amounts to a quarter grain), but plan on taking no chances with that either. I'm thinking in terms of rough sizing on the saw, then leaving them to sit for a while to see if they stay stable/until they stop moving.

The smaller sections should presumably settle much more quickly.

Thicknessing will be arranged to take fairly equal amounts off both sides, and they will then be glued and clamped up (using a good slow glue to avoid issues) before there is enough time for any friskiness to set in again.

I don't have a lot of experience, but that seems to be more or less what the bench books advise. I'm hoping that once it's glued up that it'll stay straight..

 

[OPJ]

olly -opj- built a nice beech bench last year - if you search his threads you should find a wip

It's actually on my old blog (the one on this site, not WordPress), which has been inaccessible since the last forum revamp, a few months ago. One day, I might bother to re-write it all...

I'm also in favour of stack-laminating the boards on edge; face to face. You can get a top that's effectively "quarter-sawn" (greater stability) and it should work out cheaper than buying thicker timber.

With the two layers you have, glued to each other with individual boards glues to its neighbour(s), I wonder whether there's enough room or allowance for the boards to expand and contract? That could be why the joints have opened up, possibly?

I'd tray to save what you can and make the new top as thick as possible - 75mm or thereabouts is often good, if you intend to do a lot of work with hand tools, chopping mortises, etc. I would just run a circular down the length cutting off strips 5-10mm wider than your finished size/top thickness, cutting through both layers at the same time. Unless the face-to-face joints have also failed, I don't think you're going to have much success getting those apart, without a lot of suffering!

 

[steamboat]

Thanks every one.
I was never the most patient of people though I did store the wood for a couple of months before starting the project though the timber on the bottom had been seasoning for around 3 years and the stuff on top only 12 months. I don’t thing pulling it all apart is an option as the bond between layers is still good. Ripping the boards to the required thickness could work but the stuff on the bottom is slightly spelted so a bit softer. Doing it this way would certainly help with the sides as I have dovetailed them and cut loose tongs which I was concerned about as the movement on the sides would be going up and down where as the table top would be moving side to side.
I will certainly leave the top for a couple more months and reassess the movement