"Steve" wrote in message
I measured the void on one window to see what size of wood I would need.
Upon doing so, I found out the distance between the window and edge of the
sill (the depth measurement) varies significantly as you go from one end
of
the window to the other so that one piece of wood with the same
cross-sectional area would not fit well.

Solving this is a head scratcher for me. The space seems too big to fill
it
all with wood putty or bondo (the size of the void on each window is
roughly
35" wide, 1" high, and 0.25" deep so it would be a lot of wood putty or
bondo).

Bondo or putty is a hack job. Don't even think about it



You have a couple of choices. If I could see it in person or a photo I may
have a better ideal, but here is a couple of suggestions. If I'm reading
this right there is a gap between the sill and window not the sill edge
toward the room.

Replace the sill entirely using a wider piece of wood. If you want to dress
it up, use marble or Corian instead of wood.

Shape the wood to fit. This requires some tools, such as s aw to cut it as
close to the dimension as possible, then use a plane to get the perfect fit.
A small block plane is ideal for that sort of thing.

Another possibility is to fill the void with caulk to seal it, then put a
thin piece of trim over it.
--
Ed
http://pages.cthome.net/edhome/