What size Hardboard

If you can find a sheet of 1/8th or 3/16th inch hardboard, it is much more bendable and works nicely.  Heck even 0.60 sheet styrene works nicely.  Find a product that curves easily and don't "overthink" the problem.

hardboard curves

How tight are you trying to bend the hardboard into the corners?  You can get pretty small radius curves using 1/8" thick board.  I managed to get these to about a foot radius, maybe a little less:

You could also try soaking the hardboard first, you should be able to get tighter radii that way.

1/8" can get pretty tight if you're careful

I've made curves (without wetting) as tight as 6" radius, maybe a smidge less, though the surface does just barely begin to wrinkle at that point.  The trick is to securely fasten one end and then push the other end into the curve.  You also have to have something to fasten the hardboard to once you get it where you want it.  In my case, I used the excessively sturdy framework of my layout since I was doing fascia rather than backdrops.

my hardboard is 1/8

my hardboard is 1/8.

My becnhwork is open grip and i want to mount the backdrop around all the back and sides...

i will try soaking it first.

Radius Flare Caution

1/8" hardboard in a tight radius will require framework to hold the radius else the top radius will flare out wider than the bottom fixed radius (assumes bottom is fastened to your layout).

Experienced this effect while mounting my lighting valance. The 2x4's you see are there to prevent the flaring out of the radius on the unsupported end (bottom in my case). Hardboard is fastened very close to the end of of the 2x4's.

I didn't bend mine

I didn't bend mine very much at all, it isn't as good looking as a nice smooth curve but I've found I can live with my sharp curves, I used hardboard: [I intend to put taller structures in the corners to hide the lack of curves, I've tried this out already and it works quite well]

Curved Backdrop

If you can help reduce the stress in the board by making some light kerf cuts on the back side of the board.  You don't want to go any deeper than 1/3 to 1/2 the thickness of your hardboard.

Rockler has pre-kerfed MDF

http://www.rockler.com/product.cfm?page=11206&site=ROCKLER

Bending hardboard

Be careful with soaking

I have read on other forums that "soaking" hardboard will cause it to swell and deteriorate.  I light spraying on the rough side was recommended.  Hate to see you ruin a bunch of hardboard and have to do it all over again.