The best way to analyze the problem is to use the Intersect command to find the intersection between objects you are trying to trim. Its best to work in parallel view mode so that you can zoom in to see what is going on.
There are 2 problems that are preventing you from doing what you are trying to do.
1) After you remodeled your wing is no longer closed. On the trailing edge the top and bottom halves do not match. I used ShrinkTrimmedSrf on the top and bottom of the wing and then MatchSrf (set to position) to fix that.
2) The parting split on the leading edge of the wing doesn't match the parting split of the center object. That the main reason trim isn't working. I modified the nose of the center and
split it do that the parting matches the wing on both ends. (see file.)
hydrofoilx.3dm (393.4 KB)
The magenta curve is the interestection of the center piece and the wing.
The green surfaces are the flat parting surfaces at the leading and trailing edge of the wing at the z level where the intersection curve meets the parting. The green curve is the parting split for the center piece.
With every thing lined up properly you can trim and join and mirror the parts to get what you want.
Note: you still don't have draft on the center piece and that may be a problem for drawing the part from the mould. Also, you might consider modeling something this big with a looser file tolerance. A .001mm tolerance for something this big is unnecessary. It would be a lot easier if you work with a tolerance of .01mm.