Darryl Keil Last Activity 2025-02-12 2:48 PM
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Kelby Van Patten

Posts: 3

Joined: 2006-12-30

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Subject : Warped panel question
Posted : 2007-07-02 10:38 PM
Post #33914
Here's my boneheaded mistake of the week.

I am gluing two small panels for use as cabinet doors --- each 14" x 22".

I made the panels using 1/2" baltic birch plywood, and glued 1/28" crotch mahogany on both sides of each panel. The plywood was a little warped to start with, but I figured the glued-up veneers would hold it in place. (Doh!) I used "Pro-Glue" brand plastic resin glue. (I usually use Unibond, but my stash of Unibond is too old, and I wanted to get the glue-up done this weekend. Stupid me.)

The panels came out of the vacuum press last night just fine. They were still perfectly flat this morning. But when I got home from work today, one of the panels had warped along the long dimension --- about a 1/8" warp. Since they are cabinet doors, such a warp would definitely be noticeable.

Now, here's my proposed fix, and I'm hoping like heck you all will tell me it will work, or else I'm ordering more veneer and starting over. I was planning to put a 1/4" solid mahogany band around each cabinet door. On the dimension across the edge of each door, the band will be a little wider than the 1/2" plywood (probably about 5/8" ), so that I can put a bead on the front edge of the band. Originally, this band was going to be purely decorative, but now it will also have to straighten the slightly warped door. Will a 1/4" x 5/8" band along each edge of the door be strong enough to counteract the warp? How about if I bumped it up to 1/4" x 3/4"?

Also, I know just a flat edge-joint between the banding and panel would have been adequate if it were just decorative, but do I now need to do something stronger to keep everything in line?

Thanks, everyone. And if anyone ever reads this, here's the main thing I learned from this mistake: Unibond is good! Creep is bad!


 
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Enrico Konig

Posts: 74

Joined: 2006-01-06
Location: Vancouver, BC

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Subject : RE: Warped panel question
Posted : 2007-07-02 11:23 PM
Post #33915 - In reply to #33914
The thing to do is take a 1/4 x 3/4 piece of wood and see how easy it is to bend. Pretty easy I bet. Thus I'm sorry to say it's probably unlikely to work.

Even with urea resin, I find it nearly impossible to take the bend out of a substrate, even a mild bend, unless it's part of a multi-ply package. Substrates need to be straight & true!

Good luck
Enrico


 
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Brian Gray

Posts: 339

Joined: 2004-01-21
Location: Sandusky, OH

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Subject : RE: Warped panel question
Posted : 2007-07-03 8:07 AM
Post #33916 - In reply to #33914
//The plywood was a little warped to start with//

I think that this was your problem, not the glue.

I think that I understand your solution. You want to glue hardwood strips onto the edges of the panel in hopes that the strips themselves will hold the panel flat, right?

I don't think that this will work. Even if you added splines to the joint, I still think that the panel will warp. 1/2" is pretty thick.

If this were a raised panel that were going into a frame, then maybe I could see allowing the frame to take the stress of the warp, but not simple hardwood strips glued into place.

My 2 cents. Probably time to start over.


 
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Bruce Berman

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Joined: 2005-06-01
Location: Pittsburgh, Pa., USA

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Subject : RE: Warped panel question
Posted : 2007-07-03 11:51 AM
Post #33917 - In reply to #33914
Kelby,
As Enrico and Brian have concluded it is time to start over. Brian's analysis is especially on point. Let me add that Baltic birch is notoriously unstable and not a good core for unrestrained doors. Note that it is sometimes twisted rather than just bent. You should spend as much time choosing and preping your core as in the face. One can't succeed without the other.

Bruce Berman
Miracle Veneer Trimmer


 
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craig tufankjian

Posts: 308

Joined: 2004-02-01
Location: syracuse ny 13208

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Subject : RE: Warped panel question
Posted : 2007-07-03 12:13 PM
Post #33918 - In reply to #33914
before you toss it in the garbage try this. elevate the warped panel over two blocks of wood about 3 inches high. warped side down. take a sponge and liberally wet the area below the panel that you elevated. this will re-introduce moisture back into the panel and possibly warp it back into shape.


however, you may encounter another problem, if the grain of the crotch mahogany is going in the same direction as the birch ply the feather portion of the crotch with start to crack over time. if you insist on using a plywood substrate use a lumber core plywood. all crotch species should be two plied prior to a final lay up.

craig


 
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Kelby Van Patten

Posts: 3

Joined: 2006-12-30

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Subject : RE: Warped panel question
Posted : 2007-07-03 2:33 PM
Post #33919 - In reply to #33914
Thank you, everyone!

I have definitely learned (1) to use a flat substrate, and (2) to stick with an MDF core for a panel like this.

Here's something that I still don't understand, though. When I removed the panel from the vacuum bag, it was flat, and it remained flat the next morning. It wasn't until I got home from work the next day that it was warped.

It seems to me that, if the problem was that the slightly warped substrate couldn't be straighted by the veenering, why didn't it "spring back" shortly after coming out of the press? Is it possible that the warp I'm seeing now is not due to the original warping of the substrate, but rather due to uneven moisture loss after it was veneered? I admit that after I took the panels out of the vacuum bag, I lied them down flat on my bench, so I suppose it is possible that the moisture left the "up" side faster than the "down" side.

I'll try the suggestion above to re-introduce a little moisture and see if I can warp it back to flat. But I really appreciate all the suggestions, and I'm resigned to the likelihood that I'll be re-doing these panels.


 
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Scott

Posts: 31

Joined: 2006-08-23
Location: New Hampshire

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Subject : RE: Warped panel question
Posted : 2007-07-03 2:43 PM
Post #33920 - In reply to #33919
It will continue to warp until the glue is absolutely ridgid. You must clamp the panel flat after it comes out of the bag for a few days until the glue is ridgid and you can get cut by the scraps. Here is a trick to fix it that works for me . Score the panel on the tablesaw every 1/2" or so on the back most of the way through. Now it will easily bend back straight. Fill the voids and re veneer the back. Works perfect every time. No need to throw away the expensive veeneer. Sometimes I dont even fill the voids. No need to use crotch on the back
Scott


 
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Bruce Berman

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Joined: 2005-06-01
Location: Pittsburgh, Pa., USA

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Subject : RE: Warped panel question
Posted : 2007-07-03 7:41 PM
Post #33921 - In reply to #33920
Kelby,
Until the veneer and core have completely dried out your panel has not stabilized and reached its final shape. You shouldn't sand the panel until it is truly dry, usually about 24 hrs. Wetting the panel is only a temporary solution. When it dries out you will be back to where you started. Unfortunately clamping usually doesn't work with a plywood core although it can be very successful with a MDF core.
Good luck with your new panels.

Bruce Berman
The Miracle Veneer Trimmer



 
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Earl

Posts: 75

Joined: 2003-12-04
Location: Pensacola FL

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Subject : RE: Warped panel question
Posted : 2007-07-03 8:04 PM
Post #33922 - In reply to #33919
If the concave side of the panel was face up on your bench, open to the air, that is your problem. You cannot just place your veneered panels on a bench top with out equalizing the sides. In other words, if air can get to one side, the other side should be equal in the exposure to air. I always sticker my panels for at least 1-2 days after pressing to relieve any extra moisture accumulated during glueup. I also put some extra ply or weight on top as insurance. I do this whether using MDF or ply as a substrate.

There is not a 100% guarantee against warping when using ply. And 1/2" seems awful thin for a door.


 
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Don Stephan

Posts: 825

Joined: 2003-07-18
Location: Cincinnati, Ohio

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Subject : RE: Warped panel question
Posted : 2007-07-03 8:05 PM
Post #33923 - In reply to #33919
Kelby:

I think you've found at least part of the cause of the warp - allowing the panel to lie flat on a surface rather than standing on an edge to allow even evaporation of moisture and curing.

It's certainly worth trying the suggestion to wet the side that was exposed, and then standing the panel on edge. I wouldn't expect however the panel to be any flatter than the substrate was before pressing.

Good luck with it.


 
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Darryl Keil

Posts: 1454

Joined: 2003-05-22
Location: Maine

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Subject : RE: Warped panel question
Posted : 2007-07-03 9:25 PM
Post #33924 - In reply to #33914
Kelby,

Ah, the slippery slope of trying to repair a panel gone bad. I remember a conference table this happened to me on that I just wouldn't give up trying to fix the warp. I even went so far as to rout grooves in the underside and put in threaded rod trying to flatten it out. I finally gave up way too late into the project, cost me a bundle. In general I find warped panels are very rarely fixable and Ive learned to start over almost immediately, as much as it hurts to do so. I'll try a few simple things, like what Craig suggested, but then move on.

Everything of importance has already been said but I will say that I make a habit of standing all my panels on edge until the glue is fully cured. Something to consider.

Sincerely
Darryl Keil


 
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Kelby Van Patten

Posts: 3

Joined: 2006-12-30

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Subject : Update on warped panel problem
Posted : 2007-07-04 7:57 PM
Post #33925 - In reply to #33924
Well, last night, I decided to take drastic measures in a desparate attempt to deal with the warped panel. I took a damp paper towel and wiped it all over the concave side of the warped panel. (One of them newfangled hi-tech fixes.) About an hour later, it was flat. Tonight, it's still flat.

I'll let it sit a couple days more to see if it holds up, but for now, everything seems to be hunky-dory.

Thanks for all your suggestions!


 
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Brian Gray

Posts: 339

Joined: 2004-01-21
Location: Sandusky, OH

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Subject : RE: Update on warped panel problem
Posted : 2007-07-05 11:26 AM
Post #33926 - In reply to #33925
Wow. Im surprised to hear the it's flat.

However, make sure to give it time. Over the next 4-5 days, the panel might just return to where it was.

I don't want to discourage you, I'm just kindly saying don't celebrate yet! Let it stabilize over some days and see what it's going to do.

Please report back. We can all learn from what happens.
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