How do You shape in a single concave??

Hi all of You! I spent my day today trying to shape in a single concave going basically all the way through to the tail of the board I’m making.

How do You put in a concave like this into the bottom? I used a planer and tried fading it with the depth adjustment knob while planing down from nose towards the tail.

The concave I tried to put in is about 4mm (1/6th" approximately) deep at the deepest point and then fading out towards the ends, well at least that’s how it’s meant to look.

I found it to be trickier than shaping in double concaves because of the stringer being in the way in the middle of the concave.

Checked the archives and couldn’t really find that much on the actual shaping technique… so any help would be appreciated

Greetings from (today) sunny southern Sweden. Shaping outdoors is nice!

This might not be the right way, mark out where you want the concave /s. then plane near to the depth in the middle tapering out to the marks near the rail. true up with surform clean up with sanding block and paper ,check wth a ruler/ straight edge, repeat the sanding step, when concave is true and correct, smile , nod in agreement and have a beer.

Lots of different ways, but I used to plane the center out one nice deep cut, or more if needed, taper out a couple cuts only, then lay your planer for a rest…

Get a plywood sanding block, bend it, tape it bent, then put sandpaper starting at 60 on, sand away with the right curve, changing paper as you fair the planer cuts in.

Your bent ply is supposed to match the curve you are putting in, obviously.