While building a toy box for a client, I made a bit of a mistake on how I constructed the lid. I could have easily scraped the whole thing and started from scratch, but I decided to use it as a learning experience. After all the best way to improve is to fail. This quote is so true.
“I have not failed. I've just found 10,000 ways that won't work.” - Thomas A. Edison.
So what went wrong?
To build a lid with extra strength I added an MDF core. MDF stands for Medium-density fiberboard.
This type of wood is great to work with and has a lot excellent structural features.
When putting the lid together I used 1\2" MDF for the core, 1\2" birch plywood for the top, and 1\4" birch plywood for the bottom. After all you're rarely going to see the bottom anyway, so in my mind it made sense. It would also give the lid a nice look when it's in the open position.
So here is what I didn't think of while doing this, adding 1\2 plywood to the top is all good, however what you do to the top should also be done to the bottom. So adding the 1\4 plywood to the bottom made it uneven. When glue is drying it will shrink, so on a large surface like this lid it will affect the final result once dried. To make matters worse I cut the 1/4" plywood into strips, to give a panel type look.
As you can see the lid has cupped. So I decided to just carry on with project. I'd think of a way to solve it while building the rest of the toy box. Sometimes problems fix themselves.
You will notice I finished the lid without fixing the problem of it being cupped. Lets just say, the problem wasn't solved by my doing nothing at all.
I'm sure there are many ways to fix this problem, but after doing a bit of research on the internet, and trying to use materials I had on hand, I decided to use 1" black pipe as it is very strong and has little to no flex, for the length I was going to be using.
The idea behind this is to use the strength of the black pipe to pull the two ends down, by using a bolt on either side that will attach the lid to the black pipe, forcing the end flat.
The total thickness of the lid is an inch and one quarter, so I obliviously didn't have enough material to recess it all the way and maintain structural integrity. I routered in a 1/2" groove for the black pipe to sit in. I could have left it without the groove, but I figured this was the best way to fix the problem and make it look professional as if it was meant to be there.
I drilled two holes through the top of the lid, and two through the pipe to bolt the pipe to the lid.
I lacquered the pipe white to make it look a bit nicer.
To pull the two end down I used 2" thick oak, as it is less likely to bend past the point needed. I added a block in the middle, underneath the oak, and clamped the two ends down, using a level to see when the lid was flat.
Once it was clamped in place, I bolted down the two ends to hold the lid in place.
I ended up adding a 5" shim in the middle underneath the pipe because after I bolted it down, it wasn't enough to pull the lid flat. I used a big washer on the bolts for the top side, to ensure they wouldn't pull through the top of the lid.
This technique worked very well to fix this problem. Next time I use MDF as the core I'll remember this. What ever you do to the top, you do to the bottom.
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