You can calculate the groove distance required on the basis of the desired radius: Radius = board thickness × distance between grooves / groove width, where distance between grooves = radius × (groove width / groove thickness). (Note! The formula is approximate.) The boards can be grooved laterally or lengthwise.
Make saw marks in the boards according to your calculations. (Note! The distance is from groove edge to groove edge.)
Saw the grooves in the boards using a hand-held circular saw or a table saw with a guide strip.
The groove depth is correct when approximately 15 to 20 mm of the board is left intact, leaving the board strong enough to prevent fracture.
Saw grooves at regular intervals over the distance on which you want to bend the board. You can also saw grooves at smaller intervals at points where you want the radius to be smaller.
After sawing the grooves, bend the sheet so that the edges of the grooves meet.
Cut a piece of glass-fibre mesh of a suitable size and attach it to the inner surface of the curve using mortar. The board must be kept in the desired radius until the mortar has dried. It is easiest to do this using a sling strap.
Finnfoam Oy Satamakatu 5 24100 Salo, Finland Phone +358 2 777 300