5-Fold Rib

Strip is blanked to rib length and straightened. A rib that starts bowed gives a canopy that sags between ribs no matter how well it is tensioned.

The U-channel section is roll formed or pressed. Channel depth sets rib stiffness: too shallow and the rib buckles under wind load, too deep and the rib will not nest when folded.

Hinge holes are punched and the rib ends are formed to take the stretcher and the tip cap. Hole pitch is what sets how symmetric the canopy sits.

Formed ribs are stress relieved where the bend radius is tight, so the rib keeps its set instead of springing back over the first weeks of use.

Ribs are plated or coated by the supply chain. Corrosion on a folding rib starts at the punched holes, because that is where the coating is thinnest.

On a 5-fold frame the rib folds three times; the shortest section is only a few centimetres long, which makes hole pitch the tightest tolerance on the frame. The fibreglass tail is formed and bonded to the steel section; the joint between steel and FRP is the weak point of every folding rib.