Curved Carved HDU

[Billct2]

Quoting a 4'x8' carved HDU sign and it has to be curved to mount on curved fence on top of a curved wall.
I did a smaller one years ago on a curved stone wall. Carved a 1" thick panel. Mounted a blank
1" HDU panel to the wall first, then screwed and glued the carved panel to it, bending as it went.
That worked well, but I'm thinking a 4'x8" won't be as easy.
Any other ways to do this?

Thanks

 

[Z SIGNS]

How about putting kerf cuts on the back of the panel. That's how cabinet makers bend plywood.

 

[boardboy330]

I did one a few years ago, we had 3 sheets of HDU glued together and routed the curve. The sign is still installed on the brick wall without issue. It was a VERY expensive project though even that long ago.

 

[Billct2]

I would worry that kerf cuts would compromise the carved letters when it was bent.
I thought about stacking sheets and cutting to the curve but it sounds difficult and expensive.
Also how do you cnc the letters after the sheet is built? I guess I could sharpen my chisels but I'd rather not go that route.

 

[Zendavor Signs]

I don't know how much you have to bend it, but bending HDU is very risky. I would be concerned it would snap. I think you need to use a wood substrate and do kerf cuts like Z suggested.

 

[boardboy330]

I thought about stacking sheets and cutting to the curve but it sounds difficult and expensive.
Also how do you cnc the letters after the sheet is built? I guess I could sharpen my chisels but I'd rather not go that route.

If this was directed at me, the front was routed/CNCd and then the back was cut after - by sitting in a jig to hold it. The whole job was sketchy to be honest but it worked.

 

[John_Smith]

Bill - how deep will the carving be ?
I've done shallow sandblasted signs with 1/2" HDU and shallow hand-carved with 3/4" HDU.
Made a plywood form and laminated the top carved panel over two sheets of 1/2" HDU (using the foaming Gorilla Glue) to make one solid panel that will never loose its shape.
(Just an option to consider).

 

[Billct2]

Still working on this project proposal. The fence is being made by a railing company
that will fabricate if from aluminum. They are able to make a curved aluminum backer plate that matches
the shape of the sign. So now I'm thinking that I can make this from a 1" carved panel with a 1" blank backer
and bond them together on the backer panel. After it's all sandwiched together we can patch the edge as needed and paint.
They may even be able to calculate the exact size each layer needs to be.
But I am still thinking about the flex/stress in a 4'x8 sheet. The curve is about 1.5"-2" in 8'.
I don't have any sheets hanging around to test and then there's the added issue of the carved letters.
Like I mentioned I did a smaller one, about 1'x4' which worked fine.
Anyone ever flexed a carved HDU this big?
Any thoughts on the construction method with the backer and two layers?

 

[Billct2]

Bump

 

[GB2]

We can sandwich some .080 aluminum or steel between the two layers of 1" HDU and weld studs that would protrude out the back and be attached to the metal plate....or insert rivnuts on the internal .080 aluminum and screw bolts through the fence plate into the sign. I forgot this was going on a fence I thought it was going on the concrete wall, the fence makes it much easier. If you wanted to make it thicker then some heavier metal could be imbedded internally.

 

[Evan Gillette]

Personally, I would be concerned about the aluminum backer expanding and contracting more than the hdu than the bonded layers of hdu. I think the thinner the better but 1" should bend that much reliably. If possible I would keep the panel as equal as possible in thickness and then if you have large text (like prismatic letters) cut them separate and add them into pockets in the panel. Maybe it wouldn't make a difference but I would think that would create more "flex" and less high-stress areas in the panel. There was a neat article about this in a trade magazine a few years back (I beleive it was signcraft RIP) but they did like mentioned above and laminated to a sturdy wood structure to keep the shape.

 

[Evan Gillette]

Amazing that I actually found it... I think the original had more photos of construction or maybe a different article featuring the same craftsman.

Adding A Visual Kick To Your Signage | Sign Africa

www.signafrica.com

 

[Evan Gillette]

IIRC There was an article on Keene Sign System or something similar, He used mutiple substrates like pvc hdu aluminum and plywood to build shapes. Maybe give his shop a call to see what his experience with curved HDU is?