Question How tough is HDU board?

[okeesignguy]

I have a 3x6 HDU board 1 inch thick that has been engraved throughout 80% surface 1/2 inch deep...
It seems very flimsy...almost fragile...
I am very afraid of it breaking when I handle it...

Just how breakable is this stuff...?
I feel like I should stiffen it with something on the back like a full sheet of something or maybe some stringers of some sort...

I don't have any pictures at this moment but will post a couple when I get to the shop this morning...

Thank you

 

[FatCat]

By itself, HDU is pretty strong, but on 1" material, where you've remove 1/2 of the depth, yes, it's going to be pretty flimsy. The biggest factor will be how it is to be mounted. Would probably be OK to do a wall mount or something with a completely solid surface behind it, but if you intend to hang or support it between posts you need to attach a backer to it. (Typically we use MDO, polymetal or aluminum cut to the same size and shape.)

 

[okeesignguy]

By itself, HDU is pretty strong, but on 1" material, where you've remove 1/2 of the depth, yes, it's going to be pretty flimsy. The biggest factor will be how it is to be mounted. Would probably be OK to do a wall mount or something with a completely solid surface behind it, but if you intend to hang or support it between posts you need to attach a backer to it. (Typically we use MDO, polymetal or aluminum cut to the same size and shape.)

I was considering backing it with a full size piece of signabond (because we have plenty laying around)
However it is to be mounted on two posts so I am thinking is needs something stronger...something that can be screwed into like maybe three 1x4 boards across the back before painting...

But I like the MDO idea and feel like that would add enough strength to actually bolt through...

I have never worked with this stuff before but it sure seems as tho screws would strip out of it pretty easily so I would have to use some kind of adhesive like 3M 5200...?

 

[Billct2]

I use backer panel on HDU a lot. It the case you have described I would bond it to a backer panel and if it still feels a little wobbly use stringers to install.

 

[Gino]

Don't use it all that much, but when we do, it's usually 2" stock. With your situation, I'd definitely back it with 3/4" MDO and make sure you seal the edges real-ly good. Fill the voids and putty the whole edge all the way around. Give it at least two top coats and give the edges a coat every time you do the faces, which should give them at least 4 coats. Do this before you fasten it to the main sign. Once you have it glued and screwed fast, give the edges another coat.