1 draw lines straight ... polyline with large fillet ... curves etc ... rebuild them

project on the surface and trim ( boat + lines ) and copy paste the 3 lines

2 draw profile for the sweep ... scale it

3 rotate and adjust carefully the position of the profile ( not inside the hull ;)

save before sweep

sweep one on one

4 the third line is not trimmed it turn around the hull so the swwep produce a crap

cut the third line ... mirror it along the boat axe

when you have 2 sweep ... build a round piece with loft and boolean union

each sweeped piece is solid and can be boolean diff with cut line ( the end of the second sweep is bad ... need a cut with an arc placed on top view for example )

I can't replace the third piece on the hull ( scaling manipulation error ... doomdoom )

file joined

( il faut vraiment que j'achete un dico anglais ;) comment avoir plus de 200 mots de vocable dans le parlé de Shak'spire ;)