Slitherine

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3 Fire engulfs all the compartments on the second and main decks in the fore of the ship following the direct hits scored in this area. It will continue to burn fiercely for 48 hours.

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ORIGINAL: Rob Brennan UK

Gret article .. thanks .

Wild Willie .. maybe they did a sort of shallow glide bombing that might have clipped props, although i am completely unaware that they ever did such a manouvre.

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Second, the wooden fins on the torpedoes were not for buoyancy. As they were only installed at the rear of the torpedo, they would tend to make the torp angle downwards if buoyancy was the issue. The fins were angled upwards to allow the torp a shallower water entry, dive and run

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It is interesting to note that a Japanese factory engaged in war work prior to PH could have a "No overtime policy" when the authorities were contemplating taking on the whole world in just a few months (regarding the production of the modified torpedos).

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ORIGINAL: Nikademus

No.

French workers at New Caledonia (Nomeau)

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ORIGINAL: rtrapasso

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ORIGINAL: Nikademus

No.

French workers at New Caledonia (Nomeau)

i think there was some problem with the Australian dockworkers as well, but maybe not at the time of Coral Sea...

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ORIGINAL: rtrapasso

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ORIGINAL: Nikademus

No.

French workers at New Caledonia (Nomeau)

i think there was some problem with the Australian dockworkers as well, but maybe not at the time of Coral Sea...

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The wooden fins on the torps did not change the entry angle. They increased the drag after the torp hit the water, in effect increasing it's buoyancy. The idea was to prevent the torps from plunging to their normal plunge depth (how deep it goes into the water before the depth mechanisms could bring it to normal operating depth). Had they been less effectively buoyant they may have had problems sticking into the mud in the relatively shallow harbor.

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Actually they did help change the water entry angle to a shallower one.

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It was the flow of the water over the angled fins that brought the torp back towards the surface faster than it normally could.

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Adding buoyancy to the stern of a torpedo will make it angle down, not up.

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Pretty much a law of physics there.

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To assure acceptable water-entry angles, aircraft torpedoes were were equipped with box-like auxiliary tail fins made from plywood, which broke away on impact.

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ORIGINAL: spence

I have a picture (not very clear) of a PV-1 making a torpedo drop at Whidbey Island. The caption reads:

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To assure acceptable water-entry angles, aircraft torpedoes were were equipped with box-like auxiliary tail fins made from plywood, which broke away on impact.

On the facing page there's another photo showing "a plywood nose cap which improved the torpedo's flight ATTITUDE during free fall and cushioned water entry as it broke away."

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Every source that I have seen indicates that the wooden fins were intended to do the following:

1. increase drag and buoyancy in the water to slow the torpedo down so that its depth control mechanisms could use its usual guidance vanes and gyro settings to get the torp to the desired shallow op depth.
2. detach/break off as the torpedo pitched up to operating depth

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You must not have seen many sources.

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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.

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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.

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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.

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"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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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.