Saw this interesting plane.  For smaller boats, the back of the hull planking
(skin) might need to be hollowed out a touch to match where the frames (ribs)
curve the most.  A shipwright would make his own plane to do this.  Here is one
with a blade made from a wide chisel

https://www.classicboat.co.uk/articles/boatbuilders-notes-backing-out-plane/

Ed Minch