On Tuesday, February 14, 2017 at 10:52:28 AM UTC-5, dpb wrote:
On 02/14/2017 6:04 AM, DerbyDad03 wrote:
...

I did not use fiberglass. I slightly overfilled the voids with the
DuraGlas, just like you would with Bondo or dry wall mud and then
sanded it smooth. Primed with exterior primer, painted with exterior
paint.

...


What was the form of the voids? I used both Bondo and a
fiberglass-enhanced version to repair areas on the barn siding when did
the refurb on it. Most did _NOT_ hold up to the temperature cycling and
wind-induced movement of the wood substrate more than 5 yr or so(*). I
can imagine if were larger, deeper voids it _might_ be more successful,
but for surface damage I can't recommend bondo as being very permanent
based on the results I've had...not sure _any_ inflexible material will
stand up.



I'll wager that barn siding subjected to KS winds moves a lot more than a first floor
window sill on a 2 story colonial in the rust belt.

If my window sill moved enough to dislodge DuraGlas I'd move too. ;-)