how to straighten bowed MDF???

[rchadd]

had a shock today.

haven't been working on my cab for a few weeks.

i had cut out the side panels for my cocktail. they are made out of oar veneered mdf. i simply left them in the garage.

today i see that the sides are slightly bowed

anyone living in the UK will know that weather has been terrible for last 3 weeks - there has been a lot of rain. although the garage is dry (no damp or leaks etc) i assume the mdf has absorbed some moisture from the air and has expanded against the veneer to cause the bowing effect.

any ideas on best way to straight the sides?

how about - lay them on the floor and put heavy weight on them? will it really have any effect?

i think i'll move them into the house so it doesn't get any worse!

[bwest]

At this point you need to find a place you can store it perfectly flat and with some sort of physical restraint. It may come back when the humidity changes.

If the bow is only in one direction, then you should be able to use without exception.

Goodluck

[whammoed]

I have some experience straightening plywood but the same principles should apply:
1: given ample time you can place on flat surface with bow side up and place weight on it.  (with plywood it helps to moisten with water but this may not be a good idea with mdf)  It can take days for it to straighten out though.
OR
2: get a couple lengths of wood (2x4 for example) and place the bowed piece on them with the strips of wood under the ends of the board with the bow/curve facing up.  Place a weight on the center just heavy enough to bow the wood in the opposite direction.  Check periodically (every half hour to hour)  I have straightened out wood in a couple hours this way.

[danny_galaga]

if they are the side panels and its not severe then it should be ok to use as they are. when they are screwed to the supports theyll be straight. you should see how bent some pieces of wood are when they build houses!! but once theyre in the structure everything squares everything else

[whammoed]

if they are the side panels and its not severe then it should be ok to use as they are. when they are screwed to the supports theyll be straight. you should see how bent some pieces of wood are when they build houses!! but once theyre in the structure everything squares everything else

True, but the top of a cocktail is generally open with nothing to totally square it back up, some slight bowing could remain.  May not be noticeable but better safe than sorry.

[danny_galaga]

hehe. i really oughta read the questions more carefully! being a cocktail man myself i would agree. better to straighten them out. i was thinking of uprights for some reason. it would definitely be fine in an upright.
actually, if it happened to me id be inclined to live with the cost of cutting some new panels rather than risk it in a cocktail.

[neuromancer]

if they are the side panels and its not severe then it should be ok to use as they are. when they are screwed to the supports theyll be straight. you should see how bent some pieces of wood are when they build houses!! but once theyre in the structure everything squares everything else

True, but the top of a cocktail is generally open with nothing to totally square it back up, some slight bowing could remain.  May not be noticeable but better safe than sorry.

But the original post specifies that they are the side panels of the coctail cabinet.

If the panels are just bent (like when you take a piece of paper and bend it) then they will straighten out when you fasten them to their neighbors.

If the piece is actually bowed in the  middle, but not on the edges (like bubble gum) then the design needs to incorporate structure that you can screw to across the middle of the panel, like a 1x4.

Is the veneer wood veneer that is only glued to one side? If that's the case, that's the cause of the warp, and if you press the boards flat, it's just going to come back. The *only* solutions (imo) are to either laminate both sides at the same time, or to accept the additional structure.

Bob