Darryl Keil Last Activity 2025-09-09 11:09 AM
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David Perata

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Joined: 2010-01-09
Location: Ruthven, Iowa

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Subject : Flat, Thin Substrate Questions
Posted : 2010-01-09 11:28 AM
Post #35842
I've been working on a project for some time now and one of the biggest problems I've been having is achieving a flat substrate with no warpage on a thin (3/1l) substrate with no warpage.

First the pieces themsleves: basically 5" X 4 1/2" "squares" with a leading edge radius. After veneering both sides with bird's eye maple the total thickness of the pieces are 1/4".

The above pieces are the sides of small CD drawers. The backs are the same thickness material but are a little over ten inches long. The base is about 3/8" thick with plastic laminate on both sides top and bottom.

I've been making my own substrate with straight grained pine then gluing the BEM both sides in the vacuum press with Unibond 800.

No real problems except the stability issue. I make longer pieces of course and then cut the "squares" down to size. I've made a jig to route the radius.

Some pieces of wood warp and others not. But assuming for a moment that none of them warped, I want to glue and nail all the parts together. What will happen to the movement problem? Are the parts too small to matter?

Cross banding is not really too possble the way I need to mill the pine and place the BEM on top of it for grain effects.

The specs are set. Stainless steel U-channel trim pieces have been made for me that fit snugly over the top edge of the side pieces, running over the radius and down the front. Ditto along the back piece from one end to the other.

I laminate the base with plastic laminate top and bottom and it has stayed perfectly straight.

I guess my problem is this: Can I glue all the pieces together and have them stay put once they leave my shop?

As for the substrate. Plywood if I could get 3/16" is rarely flat. MDF I doubt I can get that size anyway. Remember, with the veneer both sides it has to be 1/4" thick.

What about plastic? I've seen some posts on here about veneering onto plastic, although pvc doesn't seem like the best choice from what I've read. Somebody suggested phenolic. Why not abs?

Plastic could be veneered and shaped like wood. No movement problems. Perfectly flat. Can be glued together with no movement. Nice. Right?

I've had some of the veneered pine in my shop for a couple of years and some have stayed straight while others warp. They have not been sealed with anything.

Any thoughts or recommendation?


 
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Don Stephan

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Subject : RE: Flat, Thin Substrate Questions
Posted : 2010-01-09 6:31 PM
Post #35843 - In reply to #35842
Pine probably should be quartersawn to be stable enough for you, and doubt you can purchase in any quantity. Can you inspect your aged pieces to see which might have been QS and which flatsawn?
You can always run MDF through a planer or thickness sander to take to the thickness you need, and that should be very stable if you remove from both sides. Dusty, but an option.


 
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Enrico Konig

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Subject : RE: Flat, Thin Substrate Questions
Posted : 2010-01-09 6:41 PM
Post #35844 - In reply to #35842
Here in western Canada, both 1/8" & 1/4" mdf is widely available and very affordable - $6 or $7 for 1/8", twice that for 1/4". Often the 1/4" is undersize (as it's actually 5mm) and often ends up very close to 1/4" once veneered both sides with commercial veneers. I have also sent mdf through a drum sander when I needed it to be a bit thinner and that works very well too.


 
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David Perata

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Subject : RE: Flat, Thin Substrate Questions
Posted : 2010-01-09 6:45 PM
Post #35845 - In reply to #35842
I've been looking at past posts (to page 40 so far) and I see that others have had similar problems with warpage, thin substrates, veneering on aluminum, etc. So the problems I am having are fairly common.

I recall reading that even for a major company like Heywood-Wakefield, for their line of steam-bent drawer front furniture, they had a certain failure rate where the wood broke while bending. Naturally they only used the ones that made it.

It's quite possible that for those of us who are attempting new designs and are encountering old problems, that maybe every part is not going to be a sure-fire hit. Maybe to get twenty good pieces we have to make twenty-five or even thirty. I don't know.

I always try to eliminate as much much "chance" as possible. Not just for time and money but also the stress factor of not knowing if something is going to come out perfectly.

I guess I never knew that wood was so tempermental. But then again, I also remember reading about the railroads when they were applying sheet metal to passenger car sides. They had to contend with "oil canning" which is basically the same thing as wood warpage.

I also read about a railroad that was building their own dome cars. They broke dozens of glass panels in their domes before figuring out that they needed to relieve the stress in the frames. Their solution? Bump the car with a freight car at both ends. That did it.

I need to gain inspiration from the trials of others because my project has been so long in the works. Sometimes it seems that there is no tunnel let alone light at the end of it. But I look to Walt Disney, for example, and all of his trial & error in developing his early cartoons. He couldn't get the colored ink to stay on the cels. It was flaking off from heat. He finally had to invent his own.

I'm off on a tangent here, but I know I can solve this problem with the thin substrate.

I suppose that even if I had to stay with a solid wood substrate, that even if I glued all the parts together, that if they were situated so the grain could move together I might be okay.

Anyway, I see that some have looked on this thread but no solutions yet. Hope some of you have already solved this problem. Thanks.


 
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David Perata

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Subject : RE: Flat, Thin Substrate Questions
Posted : 2010-01-09 6:57 PM
Post #35846 - In reply to #35845
You guys must have just posted. Thanks.

I saw an old post where somebody tried veneering onto 1/8" mdf and one out of two panels warped. 1/4" mdf may be a better prospect than 1/8" but remember, even if I sanded it down, I'd only have slightly over 3/16 of material to glue onto. Still not a lot.

My pine was very fine straight grain. That would be quarter sawn, right? Now, I must say that the grain that was the straightest when viewed at an end (as opposed to grain that was slightly angled) did better.

I've looked on a plastics web site and see some interesting things. But I doubt that plastic thickness is like mdf or plywood, where it is slightly undersized. 1/4" is 1/4". Right?

Plastic might solve the problem if I could get it the right thickness. Aluminum might be easier to find the right thickness but a bit more difficult to machine. I wonder if after the veneer was applied to the aluminum, if the veneer would crack or splinter as the aluminum is cut to shape?

That Appleply stuff seems very nice but hard to get around here in Iowa. Anyway, it's been my experience that any sheet good that thin in a 4 & 8 panel is going to be warped to some degree. And, the sample 1/4" Appleply I have is exactly 1/4". Good for them!

So right now I'm thinkling it's either make the solid wood work, try plastic or aluminum. I doubt mdf will be any better with regard to warping.


 
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Darryl Keil

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Subject : RE: Flat, Thin Substrate Questions
Posted : 2010-01-10 10:34 AM
Post #35847 - In reply to #35846
David,

Two suggestions. First, commercially sliced veneer has a "pulled" and "compressed" side. When veneer thin parts it can lower the stability if you put the veneer onto to substrate with one pulled side out and the other compressed side out. You want either both pulled sides out or compressed sides out. This is absolute balance, and I believe will make a difference in your application.

There are two common ways to identify which side is which. First, bend the veneer with the grain almost to the point where you would break it. In one direction you will find the veneer will make a tighter radius than when you bend it the other way. You will get a tighter radius with the pulled side out. The other way is to feel both sides of the veneer with your hands. One side is always a bit smoother than the other. The compressed side is always a little bit rougher.

The other thing to do is make your own plywood substrate. At least a three ply or a five ply for just the substrate before you put the veneer on. Make sure its an odd number of ply's for the best balance. The more glue lines the better the stability.

Between these to things I think you will get the stability you want. You may get away with just doing the first suggestion, give it a try.

Darryl Keil


 
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David Perata

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Subject : RE: Flat, Thin Substrate Questions
Posted : 2010-01-10 12:18 PM
Post #35848 - In reply to #35847
Thanks Darryl. I always put the rough (hilly) side of my bird's eye maple out per your video that I have.

But the idea of making my own plywood is something I also thought about last night. So I'd glue up plys until I reached my desired thickness. Then for the final glue-up apply the BEM.

What would you suggest I use for the plys?


 
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David Perata

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Subject : RE: Flat, Thin Substrate Questions
Posted : 2010-01-10 1:21 PM
Post #35849 - In reply to #35848
Okay Darryl, kicking this around in my head a bit . . .

Making the plywood. If, for example, I need a 3/16" substrate before the veneering, then I could laminate three layers of 1/16" pine(?) together and veneer onto that?

Now, do the layers have to be even numbered in the cross hatching of the custom plywood grains? In other words, would four layers of 1/16" pine cross-hatched be better balanced than three? I have a feeling your answer might be "yes."

I want to use what I have on hand if I can for the custom plywood. I have a block of tiger maple that I did cut into a long 1/4" piece for testing. It seemed to stay straight for a number of weeks. Then I veneered it on both sides with the BEM. Again, not a bad result. It seems to be pretty stable stuff.

Could I use that for the custom ply?

On another note.

The sides of my cabinet that comprise the "tower" of my piece of furniture consist of 1/2" baltic birch plywood veneered on one side with BEM and the other with black dyed veneer. All from Certainly wood. I get all my veneer from them. Great people.

Okay. I thought it might be silly to have to finish the black dyed veneer on the inside of the cabinet with gloss lacquer and polish it all out. So I sent the panel through my planer and shaved off the black veneer.

Up to that time the panel had stayed pretty stable with regard to warping. But after the shaving the panel has warped along the length only which is okay cause it gets glued to the back panel anyway.

But now. . . I am going to apply gloss plastic laminate to the opposite side of the BEM veneered panel. Over the old black dyed venered side.

I did see on an old posting that you said to use the same glue when doing something like this that I used for the BEM opposite side. Fine. I'll put the panel in the press with Unibond.

Right now the panel is warped concave into the side that is to be covered in laminate. Obviously the panel was rendered unbalanced when I shaved off the dyed veneer.

I think this is a good thing more or less, as the laminate will have a tendency to warp the panel in the other direction. If it doesn't even things out then it will be darn close. I think.

At any rate, as I said, the panel does get screwed and glued to the back panel.

I probebly answered my own question there, I guess. And as I have no choice now in the matter and am committed to the laminate on the opposite side of the panel, it will just have to work.

Some ask why plywood for the panel and not mdf? Well, the 1/2" thickness of the panel is mandatory. Then, I have to cut a rabbet into the back edge of the side panels for the back.

Then, screw holding power and even glue holding power. The plywood seemed to be the best bet.

My idea is to spray the BEM side first with Zinnser Sealcoat tinted with TransTint for the base coat sealer and to get the color I want.

Then, Ultima Gloss WB lacquer about six coats over that for film thickness and then polishing out.

Then, I would apply the laminate to the other side. Why? I thought that it would be better protected with all the spraying and polishing if I put it on last after the BEM was finished completely.

I assume that applying the sealer and WB lacquer will act to unbalance the panels temporarily? Am I right in assuming this as a general rule?

Which brings me to another point about the thin substrate drawer componets.

Will sealing these components entirely on all sides right after they are made . . . will that retard the tendency to warp?

I know I have a lot of information here for you to digest, but if I can get all my ducks in a row now I can plot my course with all this new info.

Thanks Darryl.


 
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David Perata

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Subject : RE: Flat, Thin Substrate Questions
Posted : 2010-01-10 2:15 PM
Post #35850 - In reply to #35849
Darryl, I was looking at a small sample square of Appleply that they sent me, which by the way has a small warp in it. I guess anything wood will warp eventually if left lying around.

Anyway, in looking at the layers of ply I can see a thicker layer in the center and thin layers at the outside.

For my custom plywood, I guess the BEM veneer could serve as the outer layers of the ply, but this might defeat the purpose.

So what should the sequence be for the layers in terms of thickness?


 
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David Perata

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Subject : RE: Flat, Thin Substrate Questions
Posted : 2010-01-10 3:30 PM
Post #35851 - In reply to #35850
Okay, here we go! I happened upon this article by an aircraft modeler who makes his own plywood for the very same reasons we have been discussing. Seems to me to be exactly what we have been talking about.

The only question I have is the ply choice. Balsa seems rather light.

http://www.airfieldmodels.com/information_source/how_to_articles_for_model_builders/construction/make_balsa_wood_plywood/index.htm


 
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Darryl Keil

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Subject : RE: Flat, Thin Substrate Questions
Posted : 2010-01-10 7:40 PM
Post #35853 - In reply to #35851
David,

Youve got a lot of questions here and I only have time for a few so I'll say this.

Make your plywood core with an odd number of layers not even. Although a four ply has more glue lines than a three ply the outside faces of the four ply will not be going in the same direction.

If it were me and absolute stability was the most important thing I would put a 1/16" in the middle with two layers of 1/32" on each side, making it a five ply. If that's too much work then go with the three layers of 1/16"

When you shave off one side on a plywood sheet and then attempt to put something else back on there is no guarantee that it will return to balance. You'll have to experiment to find out. Maybe it will, maybe it wont. My guess is, it wont, but maybe enough for your application.

Darryl Keil


 
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David Perata

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Joined: 2010-01-09
Location: Ruthven, Iowa

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Subject : RE: Flat, Thin Substrate Questions
Posted : 2010-01-10 7:56 PM
Post #35854 - In reply to #35853
Thanks Darryl. That's just what I wanted to know.
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