Now, we'll look a bit at the layout or scribing and marking of the cuts. Not the only way to do this work, certainly, and as most one off home builders don't use software to develop surfaces; I'm showing here some rudimentary methods of marking so that cuts with hand power tools could result in clean lines and finely edged welds.

By holding a plate/sheet piece to the cut arc on the top of the cabin, the edge of the brow can be marked reaching behind or below the intersection of the two pieces when held in this position. I've drawn the top edge cut, but in previous views you can see that any material thin enough to bend without rolling and extending above and below the cabin top will work as a blank.
A means to get the angle or rake correct is to put a set of temporary 'sticks of aluminum' tacked to the top- where one stick is at the angle in Profile View the other holding it up like a leg. Or; cut ply wedges and hold them to the brow blank while its in place. All work related techniques depend on the 'crews' size 1 set to lots of sets hands means different methods make sense.

Once the blank is cut and tacked up... if the cabin is built on the shop floor, which may not be the case, its possible to strike the lower brow curve using a straight edge and several ares shown here. The image illustrates the method of striking the lower line by holding the aluminum bar extrusion at differing distances (width of the brow vertically) and when this is held in place the bar may be vertical or raked slightly and again these intersecting cylinder will create a VAST , large number, huge amount of different curves of intersections.
If the reader wanted to correlate this very unassuming image to the work done to build the boats in the photos above, then click back and forth and the relational geometry will hopefully start to emerge? Some of the brows we've seen have nearly horizontal lower edges, but others have a echoing curve upward in the transverse sweep. This is where some of the beauty of this shape becomes a subtle set of interrelated intersecting curves.
Regardless how refined the shape- these ideas shown are the basic building blocks for laying out and building your own version of an attractive (to you) cabin brow.

While not an exhaustive exploration of this windscreen covers' shapes, we've explored the three main contributions to the brow and cabin top shape. First is the camber of the cabin top as it could contribute to the brow's shape. Next is the combinations of the Plan View radius of the brow and the Profile View rake so the brow. These elements are the main influences on this functional but aesthetically pleasing piece of metal that shades the windscreen, sheds water and stylizes your cabin.
but what about some corners and hand rails?
Cheers,
Kevin Morin
Kenai, AK