I'm missing something from the initial calculation which is that the solar escape velocity from the current position of Voyager 1 is about 3km/s, so Voyager's velocity at escape would be 14km/s, not 17, which is very close to the 13km/s of plumbob without any earth assist. So basically anything in the direction of orbit beats voyager, and anything the other way loses.
Looking down on the north pole, the earth rotates and orbits counter clockwise. This means that anything from midnight to noon will be aligned with the orbital vector and anything noon to midnight will be offset. 930PM will be about halfway between sunset and midnight, so losing 11 km/s from orbital velocity sounds about right.
Looking down on the north pole, the earth rotates and orbits counter clockwise. This means that anything from midnight to noon will be aligned with the orbital vector and anything noon to midnight will be offset. 930PM will be about halfway between sunset and midnight, so losing 11 km/s from orbital velocity sounds about right.