Slitherine

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ORIGINAL: spence

     A significant point made in the article, perhaps buried in the text in a way that it escaped many people's notice, was that the Ryujo repeatedly launched ineffective high level bombing attacks against Doorman's fleet rather than torpedo attacks and that it was because the Ryujo pilots were not practiced in that type of attack (plus their torpedos were poorly maintained).  I had noted in some other threads that torpedo attacks were not nearly as common IRL as they are in WitP (the article does seem to indicate that the Betty/Nells would have attacked Doorman with torpedos if they could have lifted off their airfields (soggy) with that loading though).  

I pretty sure that the TROM of Ryujo at Combined Fleet shows not one real torpedo attack launched by that ship in its lifetime.  Perhaps that explains its "bait" status at the Battle of the Eastern Solomons as opposed to operating in conjunction with the "real carriers", Shokaku and Zuikaku (as would almost assuredly happen in the game).     

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ORIGINAL: ChezDaJez

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ORIGINAL: spence

A significant point made in the article, perhaps buried in the text in a way that it escaped many people's notice, was that the Ryujo repeatedly launched ineffective high level bombing attacks against Doorman's fleet rather than torpedo attacks and that it was because the Ryujo pilots were not practiced in that type of attack (plus their torpedos were poorly maintained). I had noted in some other threads that torpedo attacks were not nearly as common IRL as they are in WitP (the article does seem to indicate that the Betty/Nells would have attacked Doorman with torpedos if they could have lifted off their airfields (soggy) with that loading though).

I pretty sure that the TROM of Ryujo at Combined Fleet shows not one real torpedo attack launched by that ship in its lifetime. Perhaps that explains its "bait" status at the Battle of the Eastern Solomons as opposed to operating in conjunction with the "real carriers", Shokaku and Zuikaku (as would almost assuredly happen in the game).

I agree with you, Spence. Aerial torpedo attacks by all types of torpedo aircraft are too numerous. That's one of the reasons I support having torps as a tracked production item. I would also want the ability to select between torps or bombs for the weapon loadout.

It's not just an issue with the Betty/Nell/Kate/etc either. The problem extends to the Allied side as well. With a few exceptions, the Avengers were primarily used as bombers during the latter half of the war and Beauforts also primarily carried bombs.

Chez

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It seems that they were recommending their employment in the torpedo attack role was to be restricted to favorable circumstances - with more reliance on dive bombing for future CV vs CV action.

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I pretty sure that the TROM of Ryujo at Combined Fleet shows not one real torpedo attack launched by that ship in its lifetime.

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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

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A carrier's physical construction, in regards to the layout of the spaces, size of deck hatches (where ammo and such passes up from the mags), size, location, and capacity of aircraft elevators, and so on, limit that carriers ability to carry a usefull number of aircraft, as much, if not more, than the size of the hangarbay and flight deck. (How's that for a run-on sentence?)

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Chez, the illustrations used on that modeling web page are from a Japanese ordnance manual, IIRC. They're not "artist renditions" unless by that you mean a "scale drawing made by a Japanese engineer to illustrate the assembly and configuration of the torpedo."

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Your argument that the torpedo is kept level while falling through the air is something that you seem to have read (erroneously) from the information to hand.

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

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Once water entry was made, the torp did not dive as deep due to the shallower anlge during water entry.

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The wooden fins kept the torpedo from assuming too great a down angle and helped stabilize in the air.

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I never said they were to keep the torp level in the air and certainly not to give it a nose-up attitude. What I said was they were designed to stabilize it in the air and to reduce the angle at which the torp hit the water. The ideal entry angle when a shallow run was desired was around 10-15 degrees down angle. Anything less and the torp could skip on the surface, anything greater and it would stick in the shallow bottom.

Keep dancing but I think you need some new taps on those shoes.

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Chez you know it isn't worth arguing. Save your energy and fingers

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This is much the same as that discussion over explosive decompression where you cited ONE document, and in which the actual document did not claim that explosive decompression caused the incident that you mentioned. As in that prior case, the elementary physics of the situation prevents the phenomena that you describe. In a word, you don't have the first clue about what those wooden fins on the Japanese torpedoes did, just as you don't have the first clue about what happens to airflow in a punctured, pressurized compartment, just as you don't have the first clue as to how many ships were in Port Darwin when the Japanese did not "sink everything in sight" (as you have alleged). You're 0 for 3 now.

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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.

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Upon water entry and the fins breaking off, the Type 91 torpedo's own control surfaces were designed to give an immediate up order on motor start up. This coupled with their superb antiroll fins allowed the torp to reach run depth and maintain direction much faster than comparable US torps...

The best launch speed and height for the Type 91 was 140 knots and 15-20 meters. The wooden fins kept the torpedo from assuming too great a down angle and helped stabilize in the air. At this launch speed and height, with the wooden fins detaching on water entry, the torpedo would reach a maximum depth of 30-35 feet...

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Specifically and glaringly does not state that the torpedo is kept level in the air by the attachment of the fins, as you have claimed they do.

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They *will* provide additional drag once the torpedo hits the water, at least for however long they remain attached. And that is what keeps them from plunging as deeply.

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In all cases, the drag from the fins will tend to result in the torpedo pitching downward, either in the air or in the water.

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It is the torpedo's steering and depth setting mechanisms that level out the torpedo, once it has entered the water.

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If you wanted to keep the nose of a torpedo UP while in the air you would have to put a very large horizontal stabilizer on the ass end and it would have to be subtantialy canted to the angle of attack of the torpedo in the air. Or, alternatively, if keeping the nose up while in the air is desired you could use a smaller canard like feature somewhere near the nose of the torpedo.

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Your argument that the torpedo is kept level while falling through the air is something that you seem to have read (erroneously) from the information to hand.

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Here's where the physics, of which you continue to demonstrate a studied ignorance, rears its (inconveniently for your semantic sidestep) ugly head. For the torpedo to enter the water at a "shallo," "shallower than usual," "lesser," "reduced" (or any other cheap semantic revision you wish to use to avoid confronting the facts) angle of entry the wooden fins have to act to push the back of the torpedo down (because they're in the wrong place to push the front of the torpedo up). To do this they have to be either (a) aerodynamically shaped (which they are not... they do not provide lift, the chord is the same and symmetrical along the axis of the fin) or (b) very large and canted at an angle with respect to the long axis of the torpedo. The fins are neither of these things.

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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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You have read a function into their design that none of the documents you quote stipulate and that none of the sources that I have mentioned (I've mentioned FOUR now, and provided links for two, which is more than you have done), actually attribute to the wooden attachment.

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In any case, a strange accusation since you're the one claiming that Osprey's author, and pretty much everyone else, have got it wrong, and that you, alone, have "got it right" even though the one document you cite does not say that which you claim it says.

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The antiroll flippers are also interesting. The National Park Service (Arizona Memorial) Website (as I recall) states the anti-roll flippers were gyroscopically controlled..(ie..when the torpedo began to roll right the right flipper would presumably would deflect upward and the left downward correcting the roll). It is possible they could be deflected upward in concert during the free fall..causing a small nose-up force.

Taken together..even if completely passive..the larger and aerodynamically less elegant fins would lower the KE of the torp. during freefall (because of increased drag). This, in itself would be a good thing (unless you were on a US BB).

When the thing hit the water it would be a bit like a dog running out of chain while charging the mailman. I bet there would be quite a bit of cavitation scrubbing off energy and there would be the additional effect of the energy required to destroy the fins scrubbing off more energy (like a crumple zone on a Volvo). The assymmetric collapse idea is a good one too. If the bottom of the fins came off first, the extra drag on the top portion would act to pull the nose up.

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Again, nobody said it kept the torp level in the air. I said they reduced the angle at water entry.

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Given the fact that they are designed to break off at water impact, I don't see how any additional drag is created.

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But let's say for moment that you are correct and they did create additional drag. This would cause the torpedo to angle downwards after water entry... the exact opposite of what is needed.

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Your statements are contradictory. First you say that they were intended to create additional drag then you say that the additional drag would be detrimental and cause the torpedo to pitch downward. Which is it?

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These fins (the wooden anti-roll and tail fins) were designed to minimize the drag in the air and simply act as a stabilizing mechanism.

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If nothing more, just the additional weight from the fins at the rear of the torpedo will change the center of gravity and produce a flatter entry angle.

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As the anti-roll stabilizers were pitchable and had wing-shaped wooden fins attached while in the air, seems reasonable to me that they would exert some type aerodynamic force on the rear half of the torpedo.

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That is true during a normal run. But for a shallow water run, the torpedo needs a little help. The decreased angle at water entry provides that by keeping the torpedo from plunging as deep as it would otherwise.

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Again, who said anything about keeping the nose of the torpedo up?

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It does seem to me like the wooden fins on the anti-roll stabilizers are acting as canards and would have some influence of the flight of the torpedo.

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The main point to remember here is that the Japanese were not trying to stop the torpedo's assumption of a down angle once launched; they were simply trying to limit it to less than the standard water entry angle of 17 to 20 degrees when deployed under normal circumstances.

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Those are your words. Again, no one said anyone was trying to keep it level in the air.

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They were simply trying to keep it from assuming the normal down angle. Doesn't really take a lot to do that.

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I will admit that the plane of the wooden tail frame is flat, that it has no chord, does not provide lift in the way an airfoil would and that its primary purpose is air stabilization. But certainly not for additional buoyancy as you had earlier claimed.

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However, reviewing the engineering plans contained in the Nav Tech Intell document (figures 5 and 6) shows that the horizontal fin is hinged and contains what they call an “angle plate.” While it doesn’t say so, there does appear to be a way to adjust the angle of it. This may be so as to produce a downward movement of the rear of the torpedo. Regardless, I can’t prove the purpose of the hinge and the angle plate so I’ll just say it’s not germane to the discussion at hand.

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But we do have “wing-shaped” fins added to the anti-roll stabilizers. These are aerodynamically shaped. It would be rational to assume that they function to influence the flight of the torpedo in the air and quite probably provide a downward force on the rear of the torpedo.

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Second, we have the added weight of the fins themselves which moves the center of gravity towards the rear of the torpedo. This alone will slow the rate at which the nose of the torpedo drops.

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It sounds to me as though every modification was done in an attempt to influence the torp’s flight through the air until water impact.

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As the NTM documents prove, the fins broke away upon water entry…they had to… otherwise the control surfaces would be locked in place by the wooden fins. So they are incapable of providing any drag whatsoever in the water.

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The Combined Fleet source you quoted only mentions that the purpose of the fins were to keep the torpedo from diving as deeply as it normally would. Hardly a definitive source or description.

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Likewise, the Osprey article. The author states that the fins were for added buoyancy, a fact that is neither supported nor even mentioned by any other source I have seen, including the NTMs and the one other one you listed. Indeed, if added buoyancy were the purpose, it would seem logical to place them at the front of the torpedo to lift the nose. Certainly not at the rear where the added buoyancy would actually force the nose down thereby increasing the running depth.

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I, unlike you, do not claim to have got it right. What I do claim is that the authors of the NTM I cited are far more knowledgeable about the subject than either you or I. Even you dismissed many of Osprey author’s claims as suspect in your first posting on the subject. Are you now saying that isn’t so?

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So against these experts, who do you line up?

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And as it seems you haven’t bothered to read the NTM article, it seems a bit presumptuous of you to dismiss it out of hand in favor of one article written by someone you initially regarded as presenting suspect data and with no stated experience in aerial torpedoes.

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ORIGINAL: Mynok


Easy solution. Click the little green button next to the "buddy" button on one of his posts. You won't see them again.

Art by the amazing Dixie

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I'm saying that when I reject someone's argument I require a good reason for it.

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I'm saying that the document does not say that which you have inferred.

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Physics. I do wonder what the expertise was of the good lt, and whether or not the translation is rendered correctly, and I strongly suspect that you are reading far more into the NTM document than it actually states.

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Sheesh. I'm taking bets on how many pages this extends to. Anyone? Do I hear £10 for 4 pages? Anyone £10?

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Regarding your "physics", you fail to mention the physics involved in changing the underwater trajectory of an 18 foot torpedo weighing 1840 lbs (not the 1500kg you stipulated) that entered the water at a minimum speed of 133 knots (launched at 140kts) with a normal water entry angle of 17-20 degrees. Must be some pretty magical "physics" to do that within 40 feet of water.

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You apparently believe your expert (who you yourself questioned his data) is more knowledgeable than the true experts.

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As far as any past discussions go, I didn't realize there was a score to be kept.