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ChezDaJez -> RE: An article I found. Not for JFB's. (6/28/2006 12:32:28 AM)
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quote:
ORIGINAL: mdiehl
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You must not have seen many sources.
You are, as usual, incorrect. The basic flaw in your logic is in assuming that the sources I've listed are the only ones I've seen. These were listed because they are widely accessible. The NTM-Japan documents are not widely accessible.
quote:
The two sources you listed hardly discuss the subject. They contain a total of ONE sentence between them that mentions the function of the fins.
Indeed they do not. The illustration however provides a very accurate rendition of the attachment on the torpedoes. Your claim that the wooden devices leveled out the flight of the torpedo in the air is unsubstantiated. Certainly they were not angled in any way to function other than as mere fins. They're not aerodynamic (that is, they're not shaped to produced lift or thrust, like a wing or a propellor). And they're on the wrong end of the torpedo to lift the nose: the increased drag aft would point the torpedo down, not up. Your assertion that they "leveled the torpedo in the air" is not supported by the evidence to hand. To believe your claim requires that basic laws of physics and aerodynamics be ignored.
Since there are many sources that claim that the purpose of the wooden fins was to slow the torpedo after it entered the water (thereby limiting the depth to which it would fall underwater) one would suppose that, for example, that you have a unique understanding of their purpose. Apparently the author contracted by Osprey, and Ballantine (Barker), and the guys at combinedfleet.com (who are collectively quite knowledgeable) have all been fooled.
Well, then how about listing the other sources you have... if any. Doing a simple internet search and finding ONE sentence that refers to their function is hardly the way to present your erroneous point of view.
You listed combinedfleet.com as a source. I will quote what they said about the fins for your edification and education:
quote:
"The Japanese managed to deploy them in some pretty interesting places, most notably in Pearl Harbor, where the shallow depth of the water necessitated the modification of the existing torps with wooden fins so as to as make them dive less deeply upon entry into the water.
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Nowhere in this sentence does it mention when the fins detach or how they provide for a reduced dive after water entry.
The other source you listed (j-aircraft-com) is a modeling site dedicated to accurately modeling Japanese aircraft. It mentions nothing as to the purpose of the fins. It only shows an artist conception of the top and side view of them.
This is hardly a definitive discussion of their design, purpose or performance.
So, let me provide that for you.
O-01-2 "Article 2- Japanese Aerial Torpedoes" page 25 and 26:
quote:
O. Anti-Roll Stabilizers
With the exception of the Type 91 mod 1, all Japanese aircraft torpedoes are fitted with small, gyro-controlled anti-roll flippers. This method was adopted in 1940 on the Type 91 Mod 2 torpedo and has been a permanent feature in all the later designs of aircraft torpedoes.
Before 1940, it was necessary to lower the torpedoe's center of gravity as much as possible to minimize rolling. This resulted in partial filling of the warheads with explosive charge in order to concentrate the weight below the axis of the torpedo. The introduction of anti-roll flippers, however made complete filling of warheads possible and gave this torpedo greater destructive capacity.
The torpedo is kept from rolling during air travel with the aid of wooden frames attached to the anti-roll flippers (see figure 7). If rolling occurs, the horizontal rudders, which have an "up rudder", act as steering rudders and cause the torpedo to "hook" sharply when it enters the water. The use of roll-stabilizers eliminated the "hook" and gave the torpedo excellent launching characteristics.
P. Air Stabilization
Japanese aircraft torpedoes are stabilized during air travel by means of wooden frames attached to the tail and to the anti-roll flippers on the sides of the afterbody. These frames break off when the torpedo enters the water.
Two types of aerial tail frames were used:
1. Box-Type Tail Frame: (See figure 5): This type was similar to the wooden stabilizers used on U.S. aircraft torpedoes. It was very large and could not be used when the torpedo was carried in the bomb bay of an aircraft. For this reason, and also because of the scarcity of large sheets of plywood, the Japanese planned to use the X-Type tail frames in the future. The box-type frame, however, gave better performance and was used occasionally on torpedoes which were slung under the fuselage of the aircraft.
The frame was tilted diagonally and slid over the tail fins then righted and slid back until the fins fitted into the grooves on the frame. Air pressure held the frame firmly against the fins during air travel.
2. X-Type Tail Frame (See figure 6): This type was slightly less efffective but cheaper and easier to produce. It was held in place by small wooden blocks which were bolted on after the frame was placed over the tail fins. The main advantage was in its adap[tability to all types of torpedo planes.
There were also two sizes of wooden frames for the anti-roll flippers (see figure 7). They were wing-shaped and consisted of two half sections bolted around the flippers. The larger size was used originally but a smaller type was finally adopted because of the restricted openings in bomb bays.
Bolded, underlined and italicized sections are mine.
BTW, these documents are available online and their links have been posted on many occasions by many forum members. They are an excellent source of information concerning Japanese equipment and form the basis for much of the latter day writings concerning Japanese capabilities. Anyone who wishes to intelligently discuss Japanese weapons needs to be familiar with them. I am.
Do a search on the forum or search the internet for the link. Beware that several sites list the available titles for ordering but only one (that I know of) that contains the actual documents.
Chez
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