Torsion box

[dodgeram99]

I am building a assembly table. And following Marc video to the letter. It has taken me a couple weeks to get the top and bottom skins on. Due to cold weather.

The problem I have is after putting the top skin on and letting it dry.The top is bowed. At least 1/4 inch on the ends. Today I put the bottom on. Will doing this solve the bow issue? Can cold weather effect mdf? I am also using 1/2 inch mdf.

[ColinF]

Mdf should be stable in any weather, as long as it's kept dry. I doubt putting another skin on will fix the bow, more than likely some of your cuts weren't 100% straight or your work surface you referenced off of sagged in the middle. I'd guess you got a sag in your work surface, based on the fact it's a 1/4" off on both ends, do you have anything you can move it to that's flat?

[dodgeram99]

The floor. But I put the other skin on. I'll use it as an out feed table. And try another one this summer. Building in the winter sucks

[wdwerker]

I would make sure the frame/ core is very flat and put both faces on at the same time. A vaccum bag might be handy to get everything to pull up tight, but don't use too strong of a vaccum or you could crush it. Check with a good straightedge diagonally as well as length & width.

A track saw might give you straighter cuts than your tablesaw. Any time you even slightly drift off the fence the cut varies. MDF isn't bad for the faces but it doesn't glue to edges very well.