Sign info on material and "sandwiching"

[keith]

Hello All,

I am building a double sided sign that is 50 inches x 24 inches. It’s a simple v-carved sign, green background with White or Tan letters. It will be mounted between 2 4x4’s (already installed at site.) I do a lot of these on a smaller scale for interior applications using MDF because it is the cheapest……but now that it’s outdoors I want to make sure I do it right. I’ve looked through the forums and got a lot of info as to different methods to create and mount the sign (especially one that is double sided). It appears that there are hundreds of different methods, all with their own pros and cons. Here are my questions.

1. If I use Signfoam, many folk suggest sandwiching something between both pieces to make it stronger.
a. Would Extira work as a supporting piece in the middle? If so, I’m assuming gluing would be the best method if I don’t want to see any screws/bolts in the sign. Should I be concerned with swelling with Extira? Should, and how, do I seal the edges?
b. I’ve seen some people suggest Dibond as a middle piece to give it rigidity. Is this something that you guys can cut to shape on the Shopbot? Are there any concerns with expansion/contraction during hot and cold weather? Do I need to seal the edges?
2. I’ve used Extira for an outdoor sign recently, but I have not had a chance to see how it holds up to the elements. I was hoping that two pieces of Extira glued together (one for the front, one for the back) might be all I need. I’m thinking that 2 pieces glued together (1 ½ inch thick total) would be pretty rigid for a 50 inch by 24 inch sign. Anyone care to comment? Would this be enough? I’m thinking the simpler, the better.
a. If I go this route…there have been discussions on “sealing” it. Would this mean just using I couple coats of high quality primer all over it, including the edges? Or, does this mean coating the finished sign with an clear coat of something?
3. As far as Extira goes, I’ve seen threads on methods for painting it. My last Extira job (also my first one!) proved to be problematic because when I pulled off my paint masking some of the paint came off with it. I used water-based paint (I just learned on the forum that I should have used oil based on Extira.) If I go with Extira, here would be my steps:
a. Clean it with soap and water.
b. Prime it with a oil-based exterior primer.
c. Paint it with a oil-based exterior paint.
d. Seal it?

Thanks for all your help!

-Keith

[JohnG]

I've used dibond in the past with good results. I have signs that have been up for about 5 years using this product, with no expansion or contraction issues. I have also used duraply for many years with great results.

I will mention, I've had people tell me the signfoam & an aluminum product are not a good match, being the alum will expand more than signfoam (&duraply). I have not had the least bit of problems with either. Perhaps the aluminum is well insulated inside the signfoam???

As for glueing together, I've had good results with gorilla glue on both the alum & wood (and signfoam). Make sure to rough up the surfaces. To finish the edge, I've used bondo.

You didn't mention how you will attach hardware. If this is a hanging sign, I would suggest routering a matching groove in each of the materials. You can use threaded rod, about half way thru the sign, and gorilla glue that in when you assemble all the pieces.

ps. I've never used extira, so no help there.

[knight_toolworks]

silicone would eliminate any movement issues between the two.

[steve_g]

The aluminum face of Die bond is only .020 thick. It is bonded to the poly core and likely has the expansion coefficient of the plastic rather than the aluminum.

Steve

[JohnG]

I have exterior signs that have been up since Dibond first made its debut. I have never seen the aluminum separate from the plastic core. Not even slightly. I have however, seen the corrugated core products separate.

[joe]

Signs 101

Some free information and suggestions are suspect. So you should be choosey.

Why don't you consider using double sided MDO? It's been around for years. If you would like to double the thickness, use two panels.

I'm glad you posted your problems with Extira. I've posted, posted, poste, and posted about the potential problems. It's a wonderful product when used correctly.

Never, use Gorilla glue to attach large panels together. It expands and will cause problems. Good old epoxy will work every time.

DiBond and HDU: I haven't found the expansion co-effecient between these materials to be much of a problem. However I'm sure if you tried gluing forty feet of it together there would probably be a problem.

Keep in mind, if you glue two large panels together it's necessary to use a catalized adhesive. Adhesives that rely on air to set up don't work very well. In the center of your panels, Silicones, will remain damp and liquid for a long time because without any air to cure.

Joe Crumley
www.normansignco.com

[keith]

Thanks everyone.

Joe, I was thinking about MDO but since I will be carving the letters into the MDO, I assumed I'd have to seal the heck out of it. Is that true? Also, this sign is going to be installed about 3 hours away from me (a paid sign job, but for a friend) so I won't have the convenience of checking in on the sign from time to time.

I've used Signfoam before and frankly love the stuff. I was just hoping Extira could be used as a cheaper replacement when the need arises.

You did give me an idea however, that I think I verified on one of the other posts here. I could sandwich a sheet of MDO for strength in between two sheets of Signfoam, or Extira for that matter. Do you guys think that would work? I'm assuming I'd have to seal the edges of the MDO, but I could also use that as a mounting mechanism to mount to the posts.

Am I barking up the wrong tree?

In the end,

Do I need to reinforce/sandwich something between sheets of Extira to strengthen it? (Sign is 50" x 24" double sided)

What about Signfoam? Do I need to reinforce/sandwich something between sheets of SignFoam to strengthen it?

Thanks again!!!!!

[joe]

Keith,

Like you I like HDU but you could pocket textured MDO and inset some letters. This is one of my favorite methods and doesn't cost very much.

I'll take a photo of a sign in progress and post it tomorrow.

Sometimes simple solutions are the best.

[JohnG]

Signs 101

Never, use Gorilla glue to attach large panels together. It expands and will cause problems. Good old epoxy will work every time.


Joe Crumley
www.normansignco.com

Joe, what types of problems would you see with gorilla glue? I've had good luck with it myself....except for one instance. I was bonding an oval sign that consisted of 4 layers.... 2 pieces of 3/4" MDO, and a half inch signfoam on either side (this was a sandblasted sign). I made the mistake of placing 5 cement blocks on top till the glue cured, without clamping or putting in a few screws. About an hour later I returned to find the gorilla glue had caused the mdo panels to slide apart (approx 1/3 the size of the sign), kinda like a wet glass on the counter top. Luckily, I was able to pry them apart and redo.

What I learned is, the bond is actually stronger than the bond between the multi layers of the mdo itself. While prying the layers apart, the mdo actually splintered, rather than break apart at the seam.

The largest I've ever bonded together with gorilla glue was a 48 x 36. What brand of epoxy would you use for this type of application? I've only ever use GG on mdo & signfoam....weld-on for acrylic, and lord for aluminum. (The lord products are some amazing stuff).

Thanks

[knight_toolworks]

gorilla glue works ok with wood to wood joints. but it does not stick much to plastic or metal. it needs moisture to cure well and there is no moisture in those. I have tested it on wood to metal joints and it did not hold up well.