Round Bottom Plane question

[theoldfart]

I didn't get the side to side need. I think a coopers plane might work. if the curve only runs side to side and not top to bottom wooden Hollows and Rounds would also do the trick.

[TGW]

I am pretty sure the English term for the plane you want to make is SPAR PLANE.
They were concave side to side. Used by patternmakers for planingg convex shapes and by boatbuilders for planing spars and oars.

I have made one for myself. First I made the appropriate convex cooper's plane and then I used it to make the concave spar plane.
Both planes have old irons found at flea markets. Ordinary bench plane irons of the old thick sort that were purpose made for wooden planes. I ground the irons myself to the desired curvature.

If my memory serves me correct the retired boatbuilder Bob Smalser has a tutorial published somewhere on the net explaining how to make a spar plane without the use of a convex cooper's plane.

I made mine in two halves from quartersawn birch. Up here in this part of Finland we don't have any beech at all nor any mapple of good enough quality for a plane body due to the cold climate but our birches are pretty hard thanks to the same climate and have been used for planemaking since ancient times.
I fitted two dovels to align the both halves in relation to each others. Then I cut out the mortise that holds the wedge and the blade but I left the mouth very small. Little more than a saw kerf for the first 10 or 12 mm. Then I glued the two halves together.
After that I planed the concave sole to shape. With a concave sole the mouth tendsto become wider in the sides than in the middle so I chiseded the forward side of the mouth to shape only after hollowing out the sole.
If you make your plane from a solid block of wood I think you should leave the mouth very narrow almost nonexistant until you have hollowed out the sole.

Good luck!!!!