attaching hdu to steel

[jsmithconstruct]

Can I directly epoxy an HDU sign to a backing plate made of steel?

[Brady Watson]

You can, but something elastomeric like polyurethane or 3M marine adhesive would be better suited to handle expansion & contraction.

-B

[joe]

Jonithan,

In this case less might be more.

With the advantage of time, we are seeing lots of HDU failures due to improper instalatio. It's a wonderful material but has been oversold for general use. It's one of the best substrates for detailed carvings but you should be careful when spanning large distances. With time you may see failure.

I'd suggest you consider using a French Clip for attachment. This will allow for plenty of expansion and contraction of dis-similar materials. If you use a bracket at the bottom of your sign for the sign to rest on, and the French clip in upper center area the HDU can breath freely.

If you use hard glue, of any kind, these two substrates will be in a constant fight. There is NO glue that will allow for the necessary movement you need.

The attached photo is a good example of HDU failure. I'm sure the City of Roswell did their best on installation but this material becomes brittle with age and heat. It will eventually show stress cracks which leads to a shortened life.

Joe Crumley
www.normansignco.com (http://www.normansignco.com)

[Brady Watson]

Now you know somebody is going to ask what a 'French Clip' is...

-B

[dakers]

question is:
Can I directly epoxy an HDU sign to a backing plate made of steel?

studying the expansion contraction rate of hdu and steel made my brain hurt.

So for me rather then trying to gamble on the sign cracking due to the expansion contraction rate i would not glue directly unless the steel can float on what the steel is attached to, you can glue the steel to half of the french cleat and the other half of french cleat to the sign using proper glue and technique for the weight and size of sign and the size of the steel you have to work with so it is well supported for the life of the sign in all the conditions it will encounter.

i assume it is exterior and vertical and not protected.


hard for anyone to give specific advice not knowing alot more but general advice can give you options to think about that you may not have thought about.
so general advice it not meant to be the 100% accurate answer not knowing more about the install.

[magic]

How about putting it in a metal frame, with a loose piece of 3'4 plywood between layers. (3 layers) everything can move at their own rate and it also has some strength for anyone trying to kick it.

[joe]

Good for you guys. You boys now understand the problem. There are lots of ways to solve the expansion and contraction delima but if you don't know it's a factor it's doubtful you will get it right.

The last project we worked on, a 4'X6' X4" panel, was HDU with a hollow center. I made sure it had plenty of room to move. I feel sorry for most clients and signmakers who have little experience with foam. You fellows are way ahead of the general sign trade on this topic. We all want to know your successes and failures.

Keep up the good work.

Joe Crumley
www.normansignco.com (http://www.normansignco.com)