Crown Calculator

Enter your boat's maximum beam and the deck's crown height at its centreline in mm. This fixes the deck's curvature for all points along the decks lenght. Now enter the beam's width at the point of interest e.g. frame 1.
The calculator will give you the crown height at that point. It also gives three additional points at quarter, half and three quarters the distance between the centreline and the deck's edge.
The resulting five point are sufficient for you to construct the crown curve at that point.

Only use mm Max beam=4000 Crown=80 beam at P=3000.

The deck's curvature at the maximum beam is shown by the blue and green areas. The blue shows the part of the deck curvature for your specified point "P" on the sheer line.
The new crown height is the crown height at maximum beam less the height at P. The heights are calculated using trigonometry. (Now you know why we teach it).

The curvature where a coachroof/hatch meets the deck can be calculated.

All decks are built with a crown (camber) to allow water to run off. (Google "deck crown"). The Crown Height is the height of the deck above the Sheer (deck edge) at the boat centreline. The crown is not an arc as this would give an angled deck edge.
The crown is geometrically constructed as shown above. See Lackey Sailing for a full size example.

Howard Chapelle in "Yacht Designing and Planning" (1936) suggests that the crown height should be between 40 and 80mm per metre run measured at the boats point of maximun beam.
"This crown shape is then kept the same for the whole lenght of the boat. The amount of crown depends on the hull size, use more crown in small boats. The Transom should have the same or greater crown."