In article ,
BackToNormal writes
"In the Spring of 1941, he (Barnes Wallis) was ready to unveil a bomb
which was as unique as it was powerful, the 10 ton earthquake bomb. An
aerodynamic masterpiece, it would break the sound barrier on its
descent, while its offset tailfins would make it spin like a giant
dart".

According to Brickhill in The Dam Busters, the offset fins were added
after the test Tallboy went supersonic, wobbling off target as it did
so. Barnes offset the fins to stabilise it (the original reason for the
back spin on the 'bouncing bomb').

The Tallboy and Grand Slam were extremely aerodynamic and built to very
tight tolerances. Tirpitz received three direct hits and at least a
dozen very near misses, from bombs dropped from 16,000ft.

--
John