I've got to join some 1x8 mahogany to "make them longer" for
converting a full size bed into a queen size. (That's a different
issue.)

I know how to make a scarf joint but am not sure on the angle other
than the more surface the better. From a realistic point it must be
some where between 45 degrees and 10 degrees or so. There must be a
point ofdiminishing returns where little strength is gained for a
shallower angle.

There are lots of sites from Google, but I have not foune one that
gives an idea of the angle strength relationship.

Thanks