Warped HDU Panel

[joe]

Greetings troops,


Here's a 10' sign panel Ron and I completed a couple of weeks ago. They we so impressed they placed an order for another one. But there's trouble! Last Friday I made a trip over to take some photo's and to my horror, the sign was warping! The sides had curled up a good two inches and the top was well on it's way for the same distortion. That spoiled my weekend.


Here's the problem. We installed this sign panel two weeks ago. It's made from 15lb Signfoam, which is extremely good, but I made the mistake of epoxying a sheet of DiBond to the back. That was down right stupid. The aluminum is expanding much quicker than the HDU. The result is a panel that's curving tword the front by three inches. I'm sure in a month it will be even worse


Here's my plan of correction. With the panel back in the shop I'll see if I can flatten her out and buzz off the aluminum back. Then I'll apply some 2"X6" cleates. What a mess.

Here's also a little double sided hanging sign. I'm making it from Cypress. That wood sands better than any wood I've used and holds detail almost as well as HDU.

[burchbot]

Not only do you do some of the most beautiful work I have seen. You also stand behind the work you do. You are a blessing to anybody you come in contact with.
Dan

[Big-Tex]

Joe here is the problem. Its caused by unbalanced panel.
What does that mean, if you look at section of plywood you gor odd number of layers each layer at 90 deg to next (grain) that balances panel.And forces equalize.
If you apply laminate to one side of particle board you need to glue backer on other side other wise will warp just as your sign. glue upSame principle applies to wood glue up, what I tell new born wood workers you need to glue up heart to heart, bark to bark.
I hope that explains balancing.

This is common practice in woodworking.

[steve fedor]

One possible solution you may try is put the sign on your machine and cut pockets in the Dibond to create a frame or skeleton effect. This may help lessen the tension or grip on the panel.

[Brady Watson]

The problem isn't the Dibond, but the adhesive between it & the HDU. If you lay down strips of adhesive (like 1/4" beads) instead of slathering epoxy all over the sheet, you will give things some room to expand. I just talked to an HDU manufacturer yesterday about this very issue. He recommended laying the adhesive in strips.

I'm not a big fan of silicones for adhesives, but if you have a brand that you know & trust, it's elastic properties can be exploited to give the lamination some room for expansion.

-B

[curtiss]

Joe,

What is your source for the cypress ?? What sizes are typical ?


Thomas,

Would a mdf countertop with laminate/ warp if was mounted vertical rather than flat ?? How would you prevent that ?

[joe]

Curtis,

I have several wholesalers to purchase from. My local favorite is Phoenix but most of them want you to purchase a volume. My last order was for 12 quarter, which I've stickered for a year. It's rough cut and cost $7.00 a bd foot. I think you can beat that price.

I've drifted away from Poplar and want to give it another try. Has anyone been routing this material?

Brady,

NO, silicone in strips won't work. As you know silicone is air dry and sandwiching it between two non breathing surfaces is asking for trouble. I'd like to see some examples.

As you know I show samples of just about everything I do and don't ever give recommendations without a first hand knowledge. I've been led down too many dead end trails to listen to sales people.

[kevin]

Joe I,ve router poplar very nice wood I have some out side .With that said its classifed as a hardwood I'am not shure about exterior sign work

One of the easiest woods to work with in terms of holding detail

Your sign I have no clue why it twisted just a guess but I suspect rough lumber not dried has a mind of its own bad luck

[blackhawk]

Joe - I would not recommend poplar for exterior signs. It is one of the least rot resistant hardwoods. I used some 1X6 boards to dress up a post on my porch. Within about 5 years, I had to replace them because of rot. I had even primed all sides. After about 2 years, I had one poplar board that had started growing a mushroom, no joke.

[joe]

Brad,

I certainly appreciate your savy experience and advice.

Do you think it would last better if it was treated, to cut down on the micro organisms that turn the wood to pulp? I believe this serious ailment is known as dry rot. I was concerned about this with my use of yellow pine but I found a good solution. A google search brought me to the Univ. of Michigan, Forestry Dept. They suggested there wasn't anysuch thing as Dry Rot. The deterioration of the wood from inside was micro organisms, muching away. One of their recommendation was a wash down with Boric Acid. I've been using that on my Yellow Pine signs for two years. So far so good.

All that said, it seems I remember a poplar outside sign or two and it had a tendancy to crack and split not to mention warp. I gotta give this wood a try.

Thanks again for the good advice and I'll tread slowly.

Joe Crumley
www.normansign.com (http://www.normansign.com)

[blackhawk]

Joe - I am just a little familiar with Borax. I know that it is used to treat for powder post beetles. I'm not sure how long the Borax protection would last. Try checking out www.woodweb.com (http://www.woodweb.com), they have a lot of good info on there. The "sawing and drying" forum would be a good place to post a question about Borax. The moderator for that section of the forum answers a lot of the posts and he is excellent.

Brad

[marysvillesign]

Joe,
I came back to this post reviewing some other sign mounting posts.
Did you have a final outcome of this problem? I have used 6mm Dibond
as a backer without this warping. Heat in your area vs. cooler temperatures here?

[joe]

Ron,

Thanks for your interest.

We removed the sign and was luck to be able to pry the Dibond of the back with little damage to the original panel. A new 1/2" sheet of Duna 18lb was epoxied to the back. I made sure the sign was laying flat during the glue up.

I then glued attached the 2"X3" stringers to the back are re-installed. She's flat to the world now and I'll not glue up materials with different expansion rates.

Joe

[marysvillesign]

Joe,
Good to hear of the success. That Duna is great stuff.