If the flange distance of the lens is longer than the camera's flange distance, then isn't it possible? Isn't it the other way around that would require an adapter with an optic? The flange distance of the lens is shorter than the flange distance of the camera?
A quick ebay search shows adapters from Hasselblad to EF mount (some with Focus confirmation).
Hasselblad V mount to Canon EOS adapters are very common...plenty of choices. I looked earlier today for Hasselblad screw-fit to Hassy V...no luck finding that. I thought if there were a Hassy thread to Hassy bayonet adapter, that two adapters could be used, and everything would be cool. As in Hassy thread-to-Hassy-bayonet, then Hassy bayonet to Canon EF. I'm not exactly sure when Hasselblad abandoned their original mount, but I thought it was like 1948 after the 1600F was ended that they went to the "modern" Hassy mount. And prior to the 1950's, Hasselblad cameras were pretty niche-market...nowhere NEAR the popularity of Leica thread mount, so the demand for an old-style Hasselblad adapter is going to be very,very small.
Alright, I've been doing some digging (hence the thread necromancy) and I came across this thread. Anyone have any new information on an adapter like this? I really want to try my Ektar 80 f2.8 on my 7D and see what happens, but I can't find a screwonet (yes, I made it up) to EF adapter. Or screwonet to bayonet. Or anything, really.
EDIT: I may have stumbled upon the answer. The Russian clones (Kiev 88, 80, and Salyut) used a similar enough mount. Adapters DO exist for those lenses to EF. It IS possible. Sweet!