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