Matrix Games Forums

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

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.

Whose dancing but you. OK you did not say "nose up" neither did I suggest that you said they'd enter the water nose up. Once again, you have fabricated a straw man argument and attributed to me something I never said.

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.

They'd have to be *large* because they would have to overcome the drag that they themselves add to the back of the torpedo (which would pitch the front of the torpedo downward). The same set of constraints on the shape of the fins and their position on the torpedo is true in the air or in the water. (But in the water you could do some other things, owing to the increased drag, like using asymmetrical drag or asymmetrical shear, which might cause the torpedo to pitch up a little as the fins broke off).

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.

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.

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

Contribute a fact to the argument and you would find it worth arguing. If you don't know any facts or they don't support your claims it is indeed not worth your time.

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.

Yeah, okay. [&o][&o][&o] Hail to the all knowing mdiehl. [8|][8|][>:][>:][>:]

Chez

Not all knowing.** I just take the time to find out wtf before I respond to one of your petit barbs. In any case, you and I have gone ftf three times now, and in each case your claims have been proven directly incorrect. If you don't like me seeming like a know it all, don't make substantially incorrect claims. You and I would not have these issues if you'd do your homework.

I suspect, thinking more on the physics, and some decidedly unauthoritative things I've seen on the i-net, which do not warrant citation (cause I don't think they're really good sources) that the Japanese solution was asymmetrical drag after entering the water. Some of the unauthoritative sources indicate that part of the wooden attachment was designed to break off and part of it designed to stay attached. Flotation might also have been a contributor to the more general drag of slowing the torp down in the water, since plywood has a specific gravity around .70-.88.

And keep the sleepy icons to yourself. You're not foolin' anyone. Yer still awake or else you'd not continue to reply. [:'(]

** 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.

Interesting disucssion. I am not an aeronautical engineer..but I play one on the web. [8D]

Perhaps not a good idea to step into the middle of a duel..but I have to say mdiehl seems to be right on the aerodynamic argument. I don't see anything in the design that would cause the nose of the torpedo to pitch up appreciably from it's "natural" attitude while in the air. Perhaps all the representations are simplified? None of the fins appear to have an airfoil cross section..and even if they did, they would have to be "uspide down" to pull the tail down as it is clearly aft of the center of mass. If the big aft horizontal fin were angled upward say 15-20 degrees, it would tend to push the nose up..but it would be a hell of a lot of drag to carry on a combat mission. In fact, in the absence of a big fixed deviation or "active" movement of the horizontal fin in freefall..it seems to me the plywood fins would actually cause the torpedo to strike the water with a greater nose down attitude. The big drag effect would more quickly scrub off the big, intitial forward velocity vector..like a little drogue chute..and the torpedo would pitch downward as it accelerated toward the water.

Back later.

OK..back.

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.

Thanks Cap'n.

Sounds like the thing works about as I originally described. The wooden contraptions slow the descent in the water by increasing drag and contributing a little extra float (maybe only marginally, they're not very big after all) long enough for the gyro equipment inside the torp to bring the thing to operating depth. For sure those wooden fins aft aren't going to be very effective in the air, and they're not much use in the water if they instantly detach as ahem has claimed.

'Course they'd work better if the big fins aft were angled. Again, not much help in the air because they're quite small, but effective if they'd stay on for a little while in the water.

The antiroll flippers are interesting. Won't do a diddly thing for the torpedo's pitch but might provide enough thrust to rotate the torpedo, even in the air. They would of course be far more effective once the torp was in the water.

Edit: On further thought, if you could really scramble with the internal mech of the torp you could *make* those big aft fins gyroscopically controlled as well, which would make them very useful once the torp hits the water. But my sense of the matter is that the wooden things were more expedient than that. And anyhow if one went to the trouble to gyro them, might as well leave them on the torp rather than make them detachable.

If you had read my entire post detailing the design and purpose of the fins a little closer, maybe you would have caught this part:

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.

These also broke off on water entry. As they are wing-shaped, what would you conclude? Just window dressing maybe?

I also said:

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...

The only part I forgot to add was that the launch speed and height mentioned above were the optimum seetings for shallow water runs for the Type 91..

Now let's go back to your main argument. You said:

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.

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

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.

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

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.

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?

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. They broke off on water entry. The added benefit is that they also helped change the angle of the torpedo at water entry. 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. 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.

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

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.

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.

Again, who said anything about keeping the nose of the torpedo up? The object was to keep it from dropping too much. 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. 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.

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.

Those are your words. Again, no one said anyone was trying to keep it level in the air. They were simply trying to keep it from assuming the normal down angle. Doesn't really take a lot to do that.

You also said:

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.

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. 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.

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.

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.

Third, we have the aircraft’s reduced airspeed and altitude which helps reduce the amount of time available for the torpedo to attain a normal water entry angle.

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.

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.

and

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.

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.

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.

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.

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.

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?

The authors of the NTM Japan article are Lt R. Morin, USN, CDR E. Edwards, RN, and Lt H. Delacy, RN. They were assisted by CDR K. Fukuba who was the Chief Aerial Torpedo Designer at the First Naval Technical Arsenal, Aerial Torpedo Section, at Kanazawa, Japan from 1933 until 1945. RADMs Naruse and Oyagi, both former commanding officers of the First Naval Technical Arsenal and who both had extensive experience in the design and development of torpedoes since 1919, also provided additional information.

So against these experts, who do you line up? An author and European airwar game designer and a Combined Fleet website that provides no detail beyond a stated purpose. This is not a slam on the Combined Fleet website. They do have a wealth of material concerning the Japanese Navy, just not on this particular subject.

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.

Chez

Hi Cap Mandrake:

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.

Let me offer a few points from the NTM.

First, the drag created by these fins would be minimal. Why? The tail frame barely extends beyond the body of the torpedo and so would not create any noticeable drag unless the torp was tumbling. There are several nomographs contained in the NTM and they show that for an aircraft speed of 140 knots and altitude of 20 meters, torpedo speed at water impact would be 133 knts, a 7 knot loss of speed. So air drag wasn't a major consideration.

Secondly, the anti-roll stablizers did extend beyond the body of the torpedo about 6.7 inches (170mm) on either side and were wing-shaped. The engineering drawing in the NTM clearly shows the aerodynamic shape of them and states that they were controlled by a separate but similar gyro as the primary one. They were independently commanded but simultaneously controlled, meaning that they could operate opposite or inconjunction with one another.

As for what happens to the wooden fins, they were designed and built to breakaway on impact. They were not destroyed on impact. In fact, several fins were found floating in the basin at Pearl Harbor though no one initially knew what they were. I believe the NPS museum at Pearl has one on display but I could be wrong.

They were constructed of softwood .4 inches (10mm) thick. The tailframes were not bolted to the torpedo, they were constructed so that air pressure (box type) or small mounting tabs (X type) kept them in place until impact. They were of of fairly flimsy construction so as to not damage the control planes upon breaking away. The same with the anti-roll stabilizer fins.

The KE would be lost during and in the moments following water entry as the torp dove and then began its upward plane. As you said, the cavitational moment created during impact would go along way towards reducing speed. By the time the torp reached its run depth its speed would be pretty close to its nominal 42 kt speed.

The whole point was to prevent the torpedo from entering the water at its normal angle. Allowing it to do so would cause it to bury itself. The water depth at Pearl is only a little more than twice the length of the Type 91 Mod 2 torpedo so a shallower water entry angle was mandatory.

Chez

Chez

Dont waste your time. Mdiehl has proven many times, that he is incapable for even the slightest change of his illusions. No matter how hard you argue, no matter whom you quote, no matter how rude you are. It his HOLY Mission to get rid of the AXIS propaganda which has 'infected these forums'. You can't argue with fanatics. The only way is to use force against them (not viable option on the internet -unfortunately-), or completely avoid them. He is continously abusing the freedom of anonimity and of virtual presence (ie not physical). C'est le vie.

Oh yes and Ad hominum, priori, coito ergo sum, in vino veritas and stuff.

And finally my favourite. Wish it had effect. Noli te pertubari circulus meus!

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

Ursa. You should write bad comedy. Then you could write for a sitcom and have it canceled after the premiere.

Chez -

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

All of which is to say that you claim that the attachments reduce the angle in the air as well. In effect it keeps it more level.

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

That is your claim. It is not something that you have substantiated. It is clear that they break off some time during or after entering the water. Well, at least part of them break off.

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.

It would have that effect unless of course their more important function was to reduce the speed of the torpedo when it entered the water. Reducing the speed reduces the momentum and KE, and prevents it from plunging as deeply. If the depth control settings kick in as they should, and if the wooden attachments are otherwise "attitude neutral" the depth control settings will bring the torp to operating depth faster than they would if the wooden fins were not attached.

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?

They're only contradictory of one is so uninformed as to imagine that angle of entry is the *only* consideration. As I have noted several times in several ways (and as Mandrake has observed) there are other considerations.

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.

No kidding. ALL FINS STABILIZE WEAPONS IN THE AIR. Even the unguided dumb HE bombs dropped by B17s had fins. If you put a fin on the back end of the weapon the weapon is pitched downward.

Ironically, were there even a little bit of angle on the fins, they'd be far more effective in the water than in the air. Because water is a much denser medium. If you attached said fins such that a little bit of angular stress on their attachment would shear them off, then even a slight pitch on the fins would cause the torp to pitch up and the angular stress would then shear the fins off.

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.

For your claim to be correct, you would have to be able to assert that the added weight of a couple of small plywood fins on the back of a (1.5-2 ton?) torpedo substantially shifted the center of mass well aft of the normal mass center of the torpedo. If you have documentation of this claim I'd like to see it. Said shift of center of mass would have to be sufficient to overcome the designed center of the torpedo as well as the additional drag (which would force the torp downward) caused by the plywood fins of themselves.

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.

No. They're antiroll devices. That means they control ROLL not PITCH. All they can do is increase drag a bit (they have to, because drag is what provides the force to make the torp roll). Increasing drag aft would pitch the torp downward a hair. Note please, before you start splitting imaginary hares again (beep beep), that I said *control* pitch not *affect* pitch. The antiroll fins cause a problem for the pitch that they do not solve of themselves.

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.

You have not substantiated that the stabilizers aft reduced the angle at water entry. Moreover, reducing the speed of the torpedo at impact will reduce the plunge depth of the torpedo, giving the usual control mechanisms more time to correct the torpedo's depth when dropped in shallow water.

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

If you want to assert that the wooden attachments reduced the angle of entry at the water, you must assert that the pitch of the torpedo is affected. That can be phrased in many ways. You push the stern down or you push the nose up, relative to the "normal" (sans wooden attachments) attitude of the torpedo that enters the water. The effect is to keep the nose of the torpedo's nose up.

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.

They'd influence the roll. Possibly in the air. Definitely in the water because water being denser would impart more force interacting with the control surfaces. Preventing the torp from rolling much in the water would likewise allow the gyros to bring the torp to operating depth faster, I suspect. I wonder if the antiroll devices broke off too?

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.

OK. But why insist that they accomplished this in the, uh, 1-2 seconds the torp was in the air with such tiny surfaces, when they could do it that much more effectively when the torp enters the water?

You can get all the effects you want much better if you don't assume that everyone else is wrong and instead assume that the attachments had their main effect (however briefly) after they were underwater. They'd still break off with a not-at-all sophisticated bit of engineering. (Shear pins on the things would have to be sufficiently robust that a low density medium like air would not affect them, but force imparted by the water pushing on these things to alter the pitch of the torpedo underwater could shear the pins.)

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

Take a level. Place it on a wooden board inclined at 45 degrees. Now change the inclination of the board to 15 degrees. Is the board (a) more level, (b) less level, or (c) just as level, as it was at 45 degrees? If you imagine that the board is a torpedo and the downward end of the torpedo represents its nose as it falls through the air, changing the pitch of the "torpedo" by pushing down on its back end pushes the nose up. That is what "pitch" is all about. You're keeping it more level.

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

Oh really? How much directional force is imparted by those stabilizing wooden fins aft? Remember, you're trying to alter the pitch of an object that weighs... what... 1500 Kg? And you have to have sufficient force to overcome the drag that these fins add to the back of the torp.

If you are correct ,those Kates probably really disliked lugging torpedoes around in this way, because to compensate for the highly effective planes on the back of the torpedo that you posit substantially lifting the nose of the torp, the Kates would have to add a lot of downward trim. Both the torp's fins' effect and the planes added trim would substantially increase drag. Their fuel consumption would have been an ugly thing.

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.

I'm just going by what everyone else I've read (they don't go into a heck of a lot of technical detail there) said. I will agree that their main effect probably was not flotation. For the same reason that I can't see them doing alot to the pitch of the airborn torp. There's not enough stuff there. Maybe it was just energy lost from the torp as it plunged into the water, through drag or as Cap'n said, through cavitation.

The thing is, there would, one way or the other, have been a slight increase in buoyancy. It could not be otherwise if you attach a device to the thing and the material from which it is constructed -- plywood -- has a specific gravity of around .70-.85. I can see why the previous authors on this have subsumed it all as "flotation." Wood being the sort of thing that floats (well, most woods).

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.

That is actually very helpful. It would seem to me to put the nail in the coffin of the "flotation" argument. I'd bet a dollar to a doughnut that they stayed on a bit after the torp entered the water.

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.

I'd put my money on that hinge plate rather than on the antiroll stabilizers if for only this reason. For them to work to pitch the nose up (or the aft down), they'd interfere with the antiroll property. They'd both be, uh, "pushing" or imparting force in the same direction; where if you wanted them to be effective as antiroll devices, they'd have to push in opposite directions.

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.

How much can they weigh, though, relative to the mass of the torp and how do they compensate for their own added drag?

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.

We can't rule that out I supposed but I suspect that their main effect occurred during the first few seconds after the torpedo entered the water.

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.

You know, I think you're just ebing way too literal. The fins broke away on water entry seems to mean to you "instantaneously without in any way affecting the torp in the water." I don't think that the NTM document necessarily means to say that which you think it means to say. As I said, if they just "hung on there" a second in the water they'd be waaaay more effective at pitching the torp up than they would while dropping through the air. And this could be easily controlled by simply having the right kind of shear pins holding them on.

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.

OK fair enough. But look, it's not like the guys at Combinedfleet.com are a bunch of allied fanbois, or have a record of getting things manifestly WRONG. They seem pretty informed to me. And Parshall and Tulley warrant alot of respect in my book for getting published a peer-reviewed book on Midway.

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.

Yeah. But if you wanted to change the pitch of the torp in the air you'd likewise put something on the front. Like a canard. That's one reason why guided A2A missiles have canards (well, fins forward), not rudders.

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?

I'm saying that when I reject someone's argument I require a good reason for it. I've seen lots of publications that claim that the device on the torps prevented the torp from plunging as deeply when they entered the water. Some like the Osprey guy invoke flotation. Some imply some sort of submerged effect on pitch. None stipulate that the wooden thingies broke off instantaneously on hitting the water. None stipulate that they were intended to affect the torp's pitch or angle of entry in the water. And the devices, to the best that one can tell by looking at them, if they had any effect on pitch at all, would have been far more effective underwater even if they'd stayed attached for merely a second, than they would in the air.

So against these experts, who do you line up?

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.

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.

I'm not dismissing it out of hand. I'm saying that the document does not say that which you have inferred. I think you've read it too literally, in your desire to one up the Osprey guy, or win a round vs me, or just to seem like you know whereof you speak. I think you've attached yourself, like a limpet, to a very narrow view of these things as aerodynamic devices, when they are I suspect hyrdodynamic devices.

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. [:)]

I did it. A long time ago. I still wonder why it turned red from green? [:D]

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

I certainly would like to know the reason. It sure doesn't appear to be an objective search for the truth.

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

Pretty bold statement for someone who hasn't read the document. But we are used to you casting baseless dispersions on anything you don't agree with, just because you can. "I haven't read what you read but I know you didn't read it right!" Typical mdiehl once again.

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.

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.

If you had read the document or any of the NTMs for that matter, you would know that (1) they contain detailed findings based upon physical examination of the device, (2) they are written in English, (3) they are written by expert allied engineers intimately familiar with the subject at hand and (4) they were aided by key Japanese personnel who were directly involved in the design, manufacture, testing and performance of the device in question.

So I'll stand by the NTM document. Its funny that you question the expertise of the authors considering the sources you quoted have no expertise in torpedo design, production or performance. But that is typical mdiehl once again. You lined up someone without any direct knowledge or expertise of the device as your "expert." I used a document written by experts in the field. You apparently believe your expert (who you yourself questioned his data) is more knowledgeable than the true experts.

What this "debate" boils down to is that you believe the fins affected the torpedo angle only after water entry. I believe they influenced it prior. Let's leave it at that.

As far as any past discussions go, I didn't realize there was a score to be kept. Reminds me of something my psychology professor said. He said that people who feel a need to keep a scorecard generally have an inferiority complex or feelings or persecution. Just so you know, your score is wrong.

Chez

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

You know Speedy the sad thing is, that much more serious men than I am, are still lured into endless and pointless """"discussions"""" with someone who completely lack the basic skills of listening to someone else, except himself. There is a very visual saying in hungarian. It is as useless as throwing peas against a wall (in hope of bringing it down).

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

Don't waste the money, Speedy. I'm done. I don't know why I waste my time rebutting his "strawman" arguments. I must have a masochistic streak in me or something.

Chez

Skipping over much Cheznoise a bit.

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.

I did not "fail" to mention anything. Only a dishonest person could assert that I did. Hey, DUMMY, water is much more dense than air. So you are saying that the WATER could not change the pitch the torp over a vertical distance of 40 feet, but the AIR could change the pitch of the torp over a vertical distance of 30 feet. Hnh.

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

I did not question his data. I questioned his methodology. For assessing bombing accuracy at Pearl Harbor. That doesn't mean that I reject everything he has said or might say about WW2. Were I to write off everything the man said simply because I think he made a logical error, I certainly wouldn't waste my time reading anything YOU write, because your claims have been consistently incorrect.

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

It speaks to your credibility that you consistently misrepresent the facts, as you did in the B-29/depress thing, and as you did in your assertions about the Japanese sinking everything in sight at Darwin.

If you were less of a jerk, (your 'if one wants to debate intelligently,' your consistent attacks on my motive and other ad hominem discourse, your consistent deliberate attribution to me of claims I've never made, your consistent effort to pretend you did not say something that you said by trying to find some semantic wiggle room), I'd cut you some slack.

Edited the rest. It felt good to write but wtf would be the point?

My, my, my. Temper, temper!! [:-] I think someone's upset! What was the meaning of ad hominem again?