When you release the handle the bent material will spring back to 90 not 85.
How to bend 4mm aluminium sheet.
The idea of adding an angle 5 degrees past 90 is so that you can bend past 90 to allow for the spring back.
The two m10 bolts in the top are to clamp the sheet between the backstop and the base.
If you are set on trying to bend it you could try bending it 90 deg.
And then cutting it so you have one piece that looks like an upsidedown l the long leg of the l would go down either side of the transom and the short leg across the thickness of the transom.
Set a fire extinguisher in the area you will work in.
Insert your aluminum sheet into the brake beneath the removable clamp bar.
How to bend sheet metal without a brake.
How to bend sheet metal without a brake in 4 different methods with minimal or homemade tools.
Softening the aluminium sheet reduces the amount of force required to make a clean bend.
Pull the sheet until the bend area extends 6 inches past the edge of the table.
Lift the clamp bar away from the rear of the brake frame and slide the sheet in perpendicularly to the direction you want to bend it.
Bending sheet metal by hand is a manageable task if the piece of sheet metal is small and thin enough to handle.
Place the aluminium sheet on a work table.