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Why did my 3/4" plywood bend??

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Forum topic by JTWoodworks posted 04-19-2018 08:14 PM 889 views 0 times favorited 19 replies Add to Favorites Watch
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JTWoodworks

8 posts in 396 days


04-19-2018 08:14 PM

Topic tags/keywords: walnut plywood bent plywood why did my 34 plywood bend how to unbend plywood furniture grade plywood refurbishing

I recently made a cabinet using 3/4” furniture grade walnut veneered plywood. I bought the plywood pre-finished from a local plywood distributor. The cabinet is mounted in a corner of an office and holds a computer router, wifi box, and things like that. The door to the cabinet is 18” x 58” and is mounted with a piano hinge on the left side. The issue is that the bottom right corner of the door has warped out, away from cabinet, about 3/4” – 1”. The door is solid plywood with pvc trim covering the edges.

Why would the plywood bend like this? And more importantly, how can I fix it? This cabinet isn’t in direct sunlight, close to a heater or anything like that. The computers in the cabinet get a little warm but the entire top of the cabinet is open. I thought about routing a groove on the back of the door and gluing in some steel c-channel. It would be 1/2” x 1 1/2” channel. Would this work and what other ideas do you have? Thank you/ I need some help figuring this one out!

Here are links to the photos of the cabinet:
Photo 1
Photo 2:
Photo 3:


19 replies so far

View John Smith's profile

John Smith

1354 posts in 303 days


#1 posted 04-19-2018 08:20 PM

is that a baseboard heater against the wall ???
if it is, I would start the investigation there.

.

-- I started out with nothing in life ~ and still have most of it left.

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jbay

2657 posts in 1040 days


#2 posted 04-19-2018 08:22 PM



is that a baseboard heater against the wall ???
I would start the investigation there.

.

- John Smith

I had thought so too, but zoom in on it and it looks like a cardboard file box.

I can only think it’s crappy plywood.
Was it pre finished on both sides?

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JTWoodworks

8 posts in 396 days


#3 posted 04-19-2018 08:29 PM

I think that’s a cardboard box. The closest heater is across the room. I also don’t think its a quality issue. The place I got it from specializes in sheet goods. Yes, it’s pre-finished on both sides

View jbay's profile

jbay

2657 posts in 1040 days


#4 posted 04-19-2018 08:33 PM

Is it an imported or a domestic product?
Companies that specialize in sheet goods can still sell both.
I have used imported pre-finished maple before that twisted like a wet towel getting ready to flick the wife.

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JTWoodworks

8 posts in 396 days


#5 posted 04-19-2018 08:36 PM

I don’t know if it’s imported or not. I’ve bought the same plywood from them before and it stayed flat

View builtinbkyn's profile

builtinbkyn

2636 posts in 1081 days


#6 posted 04-19-2018 08:40 PM

You can probably straighten it by by veneering the opposite side. The tension from the adhesive will pull it back.

-- Bill, Yo!......in Brooklyn & Steel City :)

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JTWoodworks

8 posts in 396 days


#7 posted 04-19-2018 08:42 PM

It’s already veneered on both sides. I wouldn’t want to risk the adhesive pulling it too much. Especially since it’s only the corner that’s warped

View Loren's profile

Loren

10477 posts in 3789 days


#8 posted 04-19-2018 09:28 PM

Put a latch at the corner.

You could attach a flat frame to the back.
With a wood frame (bridle joints maybe)
it could be tuned with a hand plane. A welded
steel frame would work too.

Hafele sells a trust rod system for warped doors.
It’s probably larger than what you need but the
truss rod concept could be adapted.

View splintergroup's profile

splintergroup

2299 posts in 1363 days


#9 posted 04-19-2018 09:29 PM

So, the door was flat before and after cutting the plywood sheet?

Many ways to force-flatten a door like that, you mention one which is basically add stiff ribs.

Can you put another latch at the bottom? Since apparently this cabinet isn’t accessed that often, having it super easy to open isn’t really a big deal.

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JTWoodworks

8 posts in 396 days


#10 posted 04-19-2018 10:02 PM

That truss rod is a pretty cool concept. I didn’t know about that.

Yea the plywood was flat before and after cutting it. I don’t think I can put a latch. I doubt the client would want it.

Do you guys think adding stiff ribs would work? I was thinking to use 1/2” x 1 1/2” c-channel and inlay in the back of the door panel.

View Richard Lee's profile

Richard Lee

165 posts in 916 days


#11 posted 04-20-2018 01:05 AM

Does the cabinet get direct sunlight during the day ?

View woodbutcherbynight's profile

woodbutcherbynight

5558 posts in 2550 days


#12 posted 04-20-2018 01:14 AM

The c channel will work. I just installed some as stiffener and extra support for a cabinet top that had a 9 1/2 inch overhang. Brings it right back in.

As to what caused it, that I have no idea.

-- Live to tell the stories, they sound better that way.

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JTWoodworks

8 posts in 396 days


#13 posted 04-20-2018 01:16 AM

Good to hear it works I’m a bit unsure about it.

No the cabinet doesn’t get direct sunlight

View Redoak49's profile

Redoak49

3516 posts in 2129 days


#14 posted 04-20-2018 01:24 AM

How much heat does the computer equipment generate and is the cabinet vented. I am guessing it gets a little warm.

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JTWoodworks

8 posts in 396 days


#15 posted 04-20-2018 01:26 AM

I does get a little warm but nothing to crazy. There isn’t a top on the cabinet so I’d say it has good enough ventilation

showing 1 through 15 of 19 replies

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