Excerpt from "THE DEVELOPMENT OF THE SEAMASTER", a speech given by Werner F. Hess of the Martin Company to the Society of Automotive Engineers, Washington Chapter, on 19 February 1957:
The mine door is another interesting feature of the SeaMaster and presented, as you will see, some rather tricky problems. You will recall that the door is quite long and compares generally in sise with the bomb bay of any other aircraft of a similar dimension. The operation of the door is quite simple. When it is time to drop the stores, the mine door is rotated 180 degrees and held in that position. All the stores, which are carried on the inside bottom of the door can then be dropped by conventional techniques.
This arrangement has a very great advantage in that we do not expose the entire inside of the aircraft to severe air turbulence like that experienced with the conventional bomb bay with clam shell doors. In configurations of the latter type, the stores are often buffeted about and leave the aircraft with some erratic motions. However, tests with the P6M rotary door show that stores leave the aircraft very smoothly without any tendency to tumble or gyrate in any way. Actual drops were recorded by high speed slow motion cameras installed in the wing tip floats, but we could not show this film because of security.
The sealing problem on the mine door was difficult to solve. When the airplane lands, water pressures built up on the bottom of the hull are, as you might expect, quite high. Considerable effort went into designing or, you might say, inventing a seal system. The seal that was devised was a series of collapsible pneumatic tubes that inflate or deflate to seal the door or to release it to rotate. Even with a loss of air pressure in the tubes, the seal will remain tight under water pressure. This seal has proved to be satisfactory in every way and does not leak during landing, takeoff, or any time the aircraft is on the water.
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FOIA Memo found in NHC Files
DEPARTMENT OF THE NAVY
NAVAL AIR SYSTEMS COMMAND
NAVAL AIR SYSTEMS COMMAND HEADQUARTERS
WASHINGTON, DC 20361
IN REPLY REFER TO
AIR- 07D3
July 1983
MEMORANDUM
From: AIR-07D3 To: AIR-02E2
Subj : FOIA request, concerning seabased minelaying ASW aircraft (P6M Seamaster)
1. Subject request raised a question about the number of manufacturers involved in the. design competition for subject aircraft. By Bureau of Aeronautics letter AC-56, 09916 of 30 July 1951, the Navy invited twelve manufacturers to submit design proposals for subject aircraft. The twelve were:
Martin
CONVAIR
Bellanca
Chance Vought
Douglas
Edo
Fairchild
Grumman
McDonnell
Ryan
Sikorsky
Boeing
Only Martin and CONVAIR submitted proposals. The other ten manufacturers declined the Navy's invitation.
2. During the time that the competition for subject aircraft was in progress, there was a competition for a landbased minelaying ASW aircraft also in progress. Several more manufacturers were competing for the landbased design than for the seabased design. It is important not to confuse these two when reviewing their histories. Only Martin and CONVAIR submitted proposals for subject competition.
OR AS-04506 High performance seaplane minelayer
See: BUAER ltr AER-EV-1
11 Apr 1952
Evaluation Division file folder "Proposals 1951-1953"
/s/
Wm. J. ARMSTRONG
By Direction
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6M-1s_NAN6-74.jpg
6M-1_from_below_NAN11-55.jpg
