I installed the underbracing for the table top today, I had the work on hold whilst the table underwent some stress changes over the last couple of weeks.
I had it stored away near where I was working and heard on numerous occasions a sharp crack from it.
I was sitting quietly near it when I heard it again and observed over the week a shrinkage crack appearing on one of the sets of edge jointed boards, at first it only barely visible but eventually grew to about 4mm wide.
I didnt do to much untill it settled and stopped the “cracking” noise and the gap widening.
I didnt even bother to take any pictures at the time as it was not entierly unexpected.
However once it settled down I brought it out to see what I could do.
There was no other effect on the Table so it was definately shrinkage, what surprised me was it was only in one section as well.
As it occured completely along the glue line it made it reasonably easy to repair.
First of all I cut the glue away with a trimming Knife and then cleaned the entire length out with a small rasp.
Then cut a “shrinkage strip to repair the gap. This strip consists of a length of timber cut and trimmed to size and then spot glued in place resting on the top of the biscuits, no attempt was made to close the underside.
If any more movement occurs its simply a matter of knocking the strip out from underneath and replace it.
The Under Bracing
Upon discussion with my Son and the metal fabricator the center frames will sit on 600mm centers
So a half lap jointed frame was constructed under the table in the center and extending from each side was a support frame and support blocks in each of the corners.
I used my box cutter blade to fabricate the half lap joints.
This is the bracing in progress
And now all complete.
The corner pads? they are here simply if required otherwise they can be removed later.
All the timber near the edges was chamfered to avoid any injury to hands / knees under the table.
Every lap joints on the bracing is free to move if the table experiences any more movement.
Weights: A couple of LJs comment on the Mass or weights I posted being a bit Hefferish , so a re-weigh was conducted.
Each Board weighs approx 4.5 Kgs at 1500 mm and there are ten of them so we are looking at 45 Kgs for the boards plus the edging. I cannot physically check the completed top.
So my revised esimate is about 55 to 65 Kgs not 100Kgs as previously reported.
Here is a section of dressed board about 1M in length on the scales.
Now that should do it for the time being,... stand by for the completed Project possibly in the New Year as its due for delivery Dec 2016.
-- Regards Robert