Voge Speed Spread Diagram

[virtualpender]

I'm reading a book about Fearless Freddie Warder and the SEAWOLF SS-197. During one of the attacks the author mentioned that Warder used something called a Voge Speed Spread Diagram. It involved an attack that they didn't have time to set up on with a ship at close range. I Googled to learn more but haven't come up with anything except a passing reference in USF-25A. Does anyone have any additional info? Has anyone created something like this for SH4?

Thanks in advance!

[Gino]

I posted your question on a subvet forum, maybe they know what it's all about...

groetjes,

[virtualpender]

Excellent. Thanks, Gino! Hoping to make it up to see the COD in '09.

[Gino]

Here I've got the first answer sofar:

USF-25(A), February 1944 - COMSUBPAC Current Doctrine Submarines

This pub does not specifically mention the Speed/Spread Diagram; however, it was created by LCDR Voge while he was in command of USS SAILFISH in early 1942. He took command of SAILFISH after his boat, USS SEALION was sunk at Cavite Navy Yard (Manila) on 10 DEC 1941.

The diagram was in graph format and was based upon 200% target length coverage with a divergent spread. Note the last sentence in para 4624a. (quoted below) regarding the importance of a spread.

The curves LCDR Voge developed were parametric based upon operational speeds of then-current WWII torpedoes, including those with two speed settings (e.g. MK-14).

As the war progressed, skippers maneuvered for closer shots with torpedo runs under 1000 yards, certainly they attempted to get in position for a run that was less than 2500 yards - anything outside that run distance was pretty much considered to be a "Hail Mary" shot that would still invite a counterattack without really making the firing worth a torpedo plus the ensuing risk.

I have actually seen the curves you ask about - in the mid 60s, RADM Eller was the head of the Navy Historical Branch. While I was in NavShips, I used to spend a lot of time poking through the WWII artifacts and records he and his staff were still unboxing, sorting, and indexing. They must have had 20 clerk-typists doing nothing but microfilming the material.

LCDR Voge was promoted to CDR and became VADM Lockwood's Operations Officer at SUBPAC. His curves were widely distributed with "Uncle Charlie's" seal of approval.

The MK-III TDC was in the fleet by 1940 (the MK-I in the late 30s!) but separate tactical devices were also used. The "Is-Was" assisted in determining the best approach course and the "Banjo" accounted for the difference in actual versus "pseudo" torpedo run when setting gyro angles with the MK-I and MK-II TDCs. The MK-III TDC computed and set gyro angles continuously up to the actual point of hitting the firing plunger in the Conn.

Instead of having to point the bow or stern nest on the intended torpedo running course, the torpedo actually left the tube, ran a preset distance and enabled, then under its own gyro control, turned to its running course. It proceeded on that course until it either hit the target or ran out of fuel and sank.

Thus, the "actual" run consisted of two straight segments connected by an arc formed by the turning radius of the torpedo. This path was actually longer by a distance sufficient to cause a miss if it was not accounted for. The Banjo accounted for that difference. The MK-III TDC succeeded this unwieldy contraption but many skippers reportedly continued to use it early in the war until they gained experience with (and confidence in) the MK-III TDC.

Back to the specific issue of a spread, following are some excerpts from USF-25(A). Other sections discuss how many torpedoes should be fired at a given target under various attack conditions, but:

"4621 Spreads are always used."

"4622 The minimum spread should cover at least 80% of the target length. Even this is considered to be small spread, where the range and track are most favorable and the target speed, course, and range are accurately known. This would insure a high percentage of hits under these conditions. Normally these data are not too accurately known and spreads to cover as much as 200% of the target length should be fired, depending upon how well the problem is solved. When using any spread, sufficient torpedoes should be fired to ensure the number of torpedo hits necessary to sink the target."

"4623 Parallel spreads can be fired only from submarines having both bow and stern tubes."

"4624 Various spreads are fired using the following procedures:

a. Divergent spread is obtained by using spread angle or by swinging the submarine. The use of the latter method is less desirable than the former because of the lack of control and the possibility of missing shots. The divergent spread is simple to accomplish with modern gyro setting mechanisms. It is more difficult to evade than the longitudinal spread. Divergent spreads require rapid calculation of spread angles which are subject to error unless torpedo run is accurately known. [italics added]

b. Longitudinal spread is obtained by firing all shots in succession with parallel tracks with the same gyro angle, using different points of aim on the target. Longitudinal spread is the simplest to apply of all spreads and is used principally with periscope firing. An advantage of the longitudinal spread is that spread density is not dependent upon torpedo run.

c. Parallel spreads consist of simultaneous fire from each nest with supplementary and opposite gyro angles. The torpedoes from each nest are separated by the distance between nests plus the sum of torpedo advances. This type of spread is undesirable because of the large gap between the torpedoes from bow and stern nests. A special circumstance might make it useful against two ships of the same formation. Parallel spreads and the reasons for not using them under other than exceptional circumstances, are not to be confused with simultaneous fire from each tube nest with high angle gyros, wherein the torpedoes do not follow parallel courses."

groetjes,

[virtualpender]

Gino, thank you very much for the follow up. All very interesting. So it sounds like the Voge Speed Spread Diagram is a "cheat sheet" of spread angles based on target length?

Again, thank you for looking into this.

[Nisgeis]

I think I know what this is, but I haven't been able to get any decent pictures of it. If it's what I am thinking of, then it's a diagram with a set of concentric circles on the left hand side, with a series of 's' shaped curves on it and then another table. It is shown on some pictures of the TDC Mark 4, attached to the fuse cover above the gyro angle solver. As is always the way, when I want to find it, I can't. I haven't been able to get a picture clear enought to read any of the figures on it, or even get a clear picture of what it's for. It would be good to know what information you had to 'put in' in order to get a spread back. I'm struggling to see how the speed of the torpedo makes a difference in calculating a spread angle.

[virtualpender]

Nisgeis, if you are ever able to track down a legible version, please post it here. I'd be very interested in seeing how it works in the game. I've been following your TSAC thread closely and have printed off the new 2.1 PDF's. As soon as I have the time, I plan to really sit down and play with those tables. I'm to the point where I really want to master divergent spreads and am looking for all of the resources I can find.

Thanks for the post.

[Urge]

I came across this-The Fleet Submarine Torpedo Data Computer- on Amazon.

http://www.amazon.com/Fleet-Submarine-Torpedo-Data-Computer/dp/0974304530/ref=si3_rdr_bb_product

I don't own it and can't say if it has the Voge Speed Spread Diagram in it but it seems like a possibility. Does anyone have a copy of this? I am intrigued.

Urge

[starbird]

I came across this-The Fleet Submarine Torpedo Data Computer- on Amazon.

http://www.amazon.com/Fleet-Submarine-Torpedo-Data-Computer/dp/0974304530/ref=si3_rdr_bb_product

I don't own it and can't say if it has the Voge Speed Spread Diagram in it but it seems like a possibility. Does anyone have a copy of this? I am intrigued.

Urge
I have that book, its interesting if you like ot know how the TDC works, along with the TDC manual on hnsa.org . It does have a picture of the spread diagram.

This I believe is what you are looking for.

http://www.subsim.com/radioroom/showthread.php?p=984655