wet rot in corner of outside window

[DrGonzo]

I have cut out some wet rot in the corner of an outside window (chisel and hammer job).
I plan to replace this with some pine cut to the correct size, treat it, and paint it.

Should I be using anothe type of wood?
Secondly, there is a pattern on the current window frame, which basically sees the corner of the wood rounded off and a small line stepped inward. Anyway to get this shape made into the wood - sand it maybe?

 

[oilman]

To do this properly, you should really take the heroic approach and remove the frame from the opening, then repair it in the workshop. That way you will have an "as good as new" (possibly better than some "new") window. While it's out, you can strip the old paint and start from scratch. May lat over 100 years that way.