S boats and Mark 10 Torpedos

[ColonelSandersLite]

Hey, first post here with a few questions

Been playing an s-boat campaign (full switch)

I've been informed that the S-boats did not ever have TDCs fitted to them. Is this information accurate?

If S-boats did not have TDCs, was there a means of setting a torpedo gyro angle manually or where they strictly straight run?

Supposing that you're in a newer sub, say a tambor equipped with mark 10 torpedoes, would they work with the TDC there?

I've hunted around for information on this, but frankly trying to find information on the mark 10 is much harder than finding information on a mark 14.

Strangely, it seems it's also easier to find information on German s-boots than it is to find information on the s class submarine.


Anyways, been having fun restricting myself to 0 bearing shots without the tdc. Seriously useful skill to have.

[SteamWake]

First time Ive heard this it may be true.

I dont know how you would hit anything without a TDC.

It is true though that most early torpedoes had to have their gyros set BEFORE they were put in the tube. The game kind of glosses over that fact.

[ColonelSandersLite]

A 0 bearing shot without the tdc isn't that difficult to do really, and even has a hidden advantage or 2.

Basically:

Run your plot normally, and pick the point along the target path that you will kill him (hopefully!).

Point the submarine at that point. Your 0 (or 180 bearing for stern tubes on later model subs) has to intersect his track at the desired impact point.

Determine torpedo run time in seconds, which means you need the distance between your sub and the impact point in addition to torpedo speed. The formula (imperial not metric) is:


Run time = range to impact point / (torpedo speed * 0.5625)


Determine the distance the target will go in that time. Formula (again imperial not metric):


Target Travel = Target Speed * 0.5626 * Run time


On your plot, the aiming point is where your target will be when you fire. Simply use the circlular distance tool centered on the impact point measured out to the target travel distance above, and that's the right spot.


Measure the angle between the impact point and the aiming point.

Point the periscope at the aiming point. (don't forget to send a 0 bearing if you've been using the stadimeter or your torpedoes will go every which way!)

Finally, when the target is in your periscope, fire. If you did everything perfectly and the target does not change speed or course, your torpedo will impact at exactly the part of the ship in the center of your periscope when you fired.


Basically, with respect to rockin robins and crew, what's been named the O'Kane method a way of doing the same thing with the assistance of the tdc.



The limitations of this method are basically:
More workload, the tdc usually takes care of this stuff.
Tactical inflexibility as with the position keeper, you can fire whenever you want to so long as he's in range and you have a good solution. Here, you're limited to firing at a specific bearing.







Even when you have a tdc, there's a hidden advantage to using this method.

It sounds strange if you've never really thought about it before, but with a projectile (whether it's an rock or a torpedo) traveling on a constant speed and course, distance is not part of your firing solution. As weird as it may sound, your lead angle is exactly the same whether shooting at a target 50 feet away or 50 miles away, so long as the projectiles course/speed and target course/speed is unchanging. Diagram it out if you don't believe me .


The obvious advantage of this is that it removes 1 of the 3 questionable elements for your firing solution (range, AOB, speed, ).

The less obvious comes with practice just using dead reckoning. With familiarity, you realize that a target in a certain speed range within a certain AOB has roughly a certain lead angle. For example, a 10 knot target on a perpendicular course has to be lead 13 degrees with a mark 14 on fast. Being able to use dead reckoning on a target that's squirreling around is a nice tool to have in your bag.

[Hitman]

I've been informed that the S-boats did not ever have TDCs fitted to them. Is this information accurate?

Yes. The TDC didn't fit into their conning towers, nor had they space enough in the control room for it.

If S-boats did not have TDCs, was there a means of setting a torpedo gyro angle manually or where they strictly straight run?

They did both. Shooting with zero Gyro Angle is how it was done mainly in WW1, as as such the S-Boats -whose design dates to that era- kept it and worked without TDC. But they had means of calculating Gyro Angles in case the ideal firing position (At right angles to the target course) couldn't be achieved. The Gyro Angles could then be set on the torpedoes while in the torpedo tubes.

They used this for that calculation: http://www.hnsa.org/doc/banjo/index.htm

And this (And also the fleet boats) for computing target data: http://www.hnsa.org/doc/attackfinder/index.htm

You can construct yourself this last tool in cardboard with the templates available in the forum (Look in the sticky for resources), and you can also use a desktop version in your computer done by Gutted, here: http://www.subsim.com/radioroom/showthread.php?t=156698 It has many functions, including the proper attack course for a zero degree Gyro Angle (GA) shot.

I myself do always all my calculations and attacks without TDC when playing with an S-Boat in RFB , and you can bet that I do hit the enemy ships! The enjoyment is proportionally even bigger than simply doing manual targetting (Which is already a good one over the auto TDC)

Good hunting

[Hitman]

It sounds strange if you've never really thought about it before, but with a projectile (whether it's an rock or a torpedo) traveling on a constant speed and course, distance is not part of your firing solution. As weird as it may sound, your lead angle is exactly the same whether shooting at a target 50 feet away or 50 miles away, so long as the projectiles course/speed and target course/speed is unchanging. Diagram it out if you don't believe me .

Not always!!!!


See this thread for further info: http://www.subsim.com/radioroom/showthread.php?t=121744

[ColonelSandersLite]

What I find to be most informative (without even reading the full text even) about the links you provided in your first post is the dates. The mark 8 angle solver is dated 41, so surely the mark 1 was considerably older. At 2 years per major revision, that would place the mark 1 in 1925. More information on when this technology found its way into the boats would be nice if anyone knows.

Originally Posted by Hitman

Not always!!!!


See this thread for further info: http://www.subsim.com/radioroom/showthread.php?t=121744

Actually, yeah always.

Note the above stated caveat that the projectile has to have a constant speed and course *it's very very important*. Firing with a non-zero gyro angle, such as is depicted in that link is no longer a constant speed and course . The torpedo turns at the begining of the run, which obviously alters course, and lese obviously effects acceleration of the torpedo at the outset. You are exactly right in thinking that on a higher gyro angle shot, distance to target becomes more and more important as it takes time for the torpedo to get on course. I'll come up with an in game diagram and post it here.

[tale]

Originally Posted by ColonelSandersLite

A 0 bearing shot without the tdc isn't that difficult to do really, and even has a hidden advantage or 2.
...
Run time = range to impact point / (torpedo speed * 0.5625)


Determine the distance the target will go in that time. Formula (again imperial not metric):


Target Travel = Target Speed * 0.5626 * Run time
...

I was curious about one thing here. Where do you get that constant (0.5625) from? What does it mean?

As you already stated in your last post you can make the constant any value higher than zero you like; in your example 36.569217. So you can make the constant value equal to 1 and the result is a simplified equation:

Run time = range to impact point / torpedo speed

Target Travel = Target Speed * Run time

[ColonelSandersLite]

That constant converts knots to yards per second. I apoligize for not noting the units earlier.

Technically knots to yards per second is really
Yards per second = knots X 0.56260333333333333333333333333333333333333

So a 36 knot torpedo goes 20.25372 yards per second.

Truncation to 4 decimal places provides more than enough accuracy since the measuring tools are only so accurate anyways.


To summarize the hard drawn out method above (note using vector analysis which is *much* easier and faster).

To get torpedo run time in seconds from the distance to the impact point in yards:
Run time in seconds = range to impact point in yards / (torpedo speed in knots* 0.5625)

To get the number of yards the target will travel during the torpedo run in seconds:
Target Travel in yards = Target Speed in knots * 0.5626 * Run time in seconds

If you're inclined to use metric instead (being an american, I'm not) substitute all occurrences of 0.5626 with 0.5144 to get meters per second.


I do however strongly recommend vector analysis, just because it's much much easier, there being no need to do any real math. The only advantage of using the formulas, besides proving them to yourself, is that you know how long the torpedo run time will take.