The problem was in getting materials. The B-29 wasn't designed until May 1940 and the first aircraft was completed in Aug 1941, the problems with its engines was due to its fitment to the B-29, it went through a lot of testing and changes due to its requirements mainly having to be pressurized and its high-altitude requirement. Besides the fact that it never was planned to be used in Europe. On the other hand, the Spruce Goose was constantly at a snail's pace because of all the restrictions place upon it and the withholding of aluminum and other materials. Causing Kaiser to become so frustrated that he withdrew from his own idea. It was still designed in just 16 months. But it also didn't have the requirement of having to fly at high altitude or require pressurization. The engines originally planned for it was the R-3300 which was designed in 1937. Two different engines. As to the ground effect, all aircraft take advantage of that to take off, less so for high winged aircraft but it helps with sea planes just as much as those on land, but not so much after it rises past some 20% of its wingspan. The aircraft also never was planned to take off in Long Beach harbor and fly out to sea when it became airborne. But the whole point of my statement was that had the plane been given the go ahead early and the rush through of other projects, and the material to build it of aluminum, with the R-3300 engines, it could have been finished in quantity by late '44. Instead of or in conjunction with the beach invasion. As to air superiority, we already had that.
As to feasibility, all you have to look at is the Boeing/Pan Am 314 Clippers which had an outstanding history from 1939 to well into the '50's with only 4 - 1,600 hp engines instead of 8 - 3,700 hp engines.
Phil
