Question on sandblasting HDU foam

[signgirl]

I've always used cedar or redwood for my sandblasted signs. My question is what thickness would be correct for a double sided hdu foam? 1.5" or 2" thickness? This will be a 4x8 or 3 x8 mounted between 2 poles. Is that enough support for that size?

Thanks in advance!

 

[Cross Signs]

I would make two out of 1'' foam. And then sandwich a 1/2'' of bigger sheet of PVC between them...Use Gorilla glue .

 

[tbullo]

I have blasted 2" double sided, but used a metal frame around the sign. I have also done as mentioned and laminated 2 1'' panels onto 1/8'' aluminium.

 

[Billct2]

Yep, if you use 2" you will need a frame, or do two faces laminated to stiffener core.

 

[Kottwitz-Graphics]

I would make 2 signs out of 1.5" HDU and route a channel in the back of each and build a square tube steel frame, and sandwich it. I use 2 part west systems epoxy to mount together.

 

[bowtievega]

The HDU boards are pretty expensive, using two single sided panels for a double sided sign adds alot of cost to a project. We don't get a lot of requests for this type of sign out here in Arizona thankfully but we have done a few at a customers expense. As long as you are leaving a couple in wide border around the edge of your panel and not blasting more than 1/2" deep on each side the 2" HDU is stiff enough to support itself. Not excited about doing it but we have because a customer insisted on it. We have since convinced them to allow us to create the same look out of 100% aluminum moving forward but have had an HDU sign up for a couple years without any issues. One thing we have done is bond a piece of 1/8" aluminum strap to the top and bottom edges with gorilla glue. Stiffens that panel up nicely and is thin enough to not be noticed.

 

[Sandman]

The difference between two 1" thick HDU 4x8 panels and and one 2" thick 4x8 (from my supplier) is a whopping $40.00 When your typical 4x8 2 sided 3D sign should be starting at over $4,000, is $40 enough to worry about? That's less than 1% of the sign cost to be able to sandwich some steel inside. I would consider that cheap insurance. I also would not risk putting PVC between HDU panels. Expansion and contraction rates are too different. Some people sandwich MDO between HDU. Really? Add something that can rot to a rot resistant sign? My favorite way for installing 2 sided HDU between posts is to embed (with epoxy) 1 inch square steel tube running the length of the sign near the top and bottom. I take steel flats and weld them to some 3/4" round rod, 8" long is plenty. The rod slides into the tube. Just make sure your posts are a little further apart than the steel flats are apart when pushed all the way in on both sides. This way your posts don't have to be dead nuts on. The brackets slide in and out for a perfect fit every time. The frame in the second pic is not for an HDU sign. I use this for two sided ACP signs as well when they are to go between posts. For HDU running the square steel tube in a channel routed on both panels is plenty for stiffness and strength.

 

[signgirl]

Thanks so much for taking time to give me your input!