They are different sizes -the probably could be moded to fit, but you would really have to kit bash them together. If mine weren't in storage I would take some pictures of the size difference.
The vertical and horizontal fan parts for the Whale are really fragile, and feel as if looking at them funny they might break.
Yep, they are completely different items--I, too, considered the Water Moccasin for cannibalization but it was a no-go. I've been trying to complete my WHALE for about 2 years now, and the vane assemblies are the hardest part of this--as the parts are VERY FRAGILE (as said). I've pretty much given up on finding enough intact parts and I'm shifting my hunt to finding a complete WHALE instead. I figure the cost of completing the one I have will be MORE ( for just those vane parts!) than finding a intact one. Crazy.
That all said, the WHALE with just the shroud rings and the prop blades looks okay for display, without the vane assemblies. Just be mindful that the waxy plastic the shroud rings are made of DOES deteriorate over time, and the small tabs that slot into the WHALE hull can shear off ( mine mostly have).
I tellya, if a secondary caster made a restoration set of those parts for the fans, I'd buy a set to complete this thing--but that's certainly a pipe-dream itself.