The closing design example asks how a flying boat could keep the hull geometry needed for takeoff without carrying all of its aerodynamic drag in flight. Blackburn's B.20 used high-mounted engines and wings while allowing the central hull to retract upward after leaving the water. Side stabilizing floats and their supporting structures also folded into the wing edges. The arrangement sought to reconcile water handling, propeller clearance, and efficient long-range flight rather than accepting the usual fixed-hull compromise. Although it remained a what-if rather than a wartime success, the B.20 shows Blackburn still pursuing unconventional solutions to maritime-aircraft design.
Notable Point · 1:50:52-1:52:04
The B.20 retractable hull rethinks the flying boat
Blackburn's B.20 tried to combine a seaworthy flying-boat hull with cleaner aerodynamics by retracting the hull and stabilizing floats after takeoff.