Most of my 20–year career in the Navy was in propulsion engineering…and it doesn’t take much to see that the H45 would not only have been a gigantic waste of resources, but even as big as it was, it could not have survived a battle against even a single aircraft carrier.
Why? The biggest fear of every experienced sailor is an out-of-control fire, for such eventually reaches munition magazines or fuel stores or paint lockers. In WWII, anti-aircraft guns weren’t that effective, and the H45 would have presented a beautiful and (relatively) easy-to-hit target for dive bombers (remember, at Midway the Japanese AA weapons were ineffective, so their carriers were almost defenseless when they didn’t have an effective combat air patrol when the American bombers and torpedo planes showed up). Once a few bombs penetrated the deck, unless the H45 had wonderful interior watertight integrity and fire boundaries, it would only be a matter of time before it became a burning hulk.
Yes, the interior decks and bulkheads would have been made of metal, but as with all modern naval vessels, almost every inch of those metal surfaces would have been painted (and painted again and again and again — it’s a Navy thing)…and all that dried paint is flammable. Thus the fire would have spread from compartment to compartment, and in those days, they didn’t have much in the way of effective breathing apparatuses.
Lastly, the ability of such fires to spread would mean that the very size of the H45 would have worked against it, for on board a ship, a fire has to be fought in three dimensions…and once such a fire got well-established, it would require damage-control efforts all around it. This would have required men, equipment, and (perhaps most of all) fire-fighting water pressure available to cover all points.
The H45 would have been a deathtrap.