Submarine Attack Course Finder (a.k.a. Is-Was / Banjo)

[jmr]

Originally Posted by Meridian

Looking forward to printing and making one of these up, nice job.

I assume Parts "P" & "C" are printed on transparent media?

I think it's just the periscope one that needs to be transparent but it would be nice if someone else can confirm this.

[Hitman]

I only made the scope transparent, the other one can also be made transparent -and in the original it seems to be- but doesn't make any difference at all

[sqk7744]

Very neat! ~ would someone be so kind as to post another step by step example.

Thanks much!

I've got these wheels down (I think):

-A (relative bearing)

-B (true course / compass heading)

-Periscope Transparency ( if the Periscope marked end with view window goes on the Subs bearing to target) then the 180 (reciprocal) arrow points to AOB right?

[now for the wheel that came off the bus...]

-D The AOB wheel is where I'm getting confused ( I'm pretty good at judging AOB manually into the TDC, but want to use the Neat Wheel.

[sqk7744]

thanks much

[WernerSobe]

btw ive seen pictures of a wiz wheel as it was used in german submarines. They have used the known or guessed length of the target to find its AOB. Basicly its the same method as you find the range by mast high.

[panthercules]

Originally Posted by WernerSobe

btw ive seen pictures of a wiz wheel as it was used in german submarines. They have used the known or guessed length of the target to find its AOB. Basicly its the same method as you find the range by mast high.

Hmmm - now this sounded like a very cool (and relatively easy) idea at first - if you have a decent range estimate, and you can measure the observed/apparent length (presumably by reference to the markings along the horizontal/x-axis of the scope/TBT), it would seem to be a relatively simple matter of math/formulas to compute the AOB based on the relationship of the apparent length to the actual length (available from the recognition manual). However, I wonder if a wiz-wheel to do this would really be any easier to deal with than the Is-Was thing described in this thread, and this one seems to let you calculate either AOB or target course, depending on which data you already know, which is probably more useful than the above sort of special-purpose AOB calculator would be. Will have to see if I can put one of these Is-Was things together - sounds very cool.

[sqk7744]

Thanks CC!

That did the trick!

Cheers

[WernerSobe]

im not sure if i get it right...

You can find the course of your target with that? Why anyway? the more interestning thing to find out would be the AOB.

[simple nuke]

I spoke to a retired Submarine C.O. on Saturday, who originally qualified on an S Boat. He told me that the Is-Was was a circular slide rule that was used to calculate the rate of change of the target's bearing from the submarine, in order to determine the course of the torpedo. On the S Boats, the periscope was normally used in the Control Room, next to the Tracking Party. The target's AOB, Range and Speed (Is) was compared to what those values where (Was) after some measured time. The Bearing Rate Change was used by the Tracking Party, along with the boat's course and speed, to calculate the Target's course and speed, and then calculate the torpedo's course and when to fire, based on a known torpedo speed.

After the adoption of the TDC, the Is-Was was used as a means to check the TDC solution and for use incase of TDC failure.

[Hitman]

Yes that's right, this is how the rear part of the wheel works, I found it out recently and I'm already working in the graphics. It is more or less like this:

1.- You detect the target, identify it, take bearing and range and make a guess of the AOB, then plug the values into the part of the wheel we have already. Now you have an idea of the course and can plot an intercept

2.- You make a second observation some time later (Note bearing, range and time between observations) and then turn around the wheel and use the rear part: You start by fiddling around with the medium wheel until the difference in bearing matches and find the AOB with that. You guess of the AOB in the first observation helps you start already with an aproximate solution. Now you read across the wheel and know also the distance travelled. It's time then to use the inner wheel and adjust the "time" between observations to that distance travelled -read in the outer wheel- and bingo! you can directly read target's speed at the outside ring Wondeful tool, isn't it?

Stay tuned, I will post a downloadable template ASAP for the rear part of the wheel with a tutorial

[sqk7744]

Originally Posted by Hitman

Yes that's right, this is how the rear part of the wheel works, I found it out recently and I'm already working in the graphics. It is more or less like this:

1.- You detect the target, identify it, take bearing and range and make a guess of the AOB, then plug the values into the part of the wheel we have already. Now you have an idea of the course and can plot an intercept

2.- You make a second observation some time later (Note bearing, range and time between observations) and then turn around the wheel and use the rear part: You start by fiddling around with the medium wheel until the difference in bearing matches and find the AOB with that. You guess of the AOB in the first observation helps you start already with an aproximate solution. Now you read across the wheel and know also the distance travelled. It's time then to use the inner wheel and adjust the "time" between observations to that distance travelled -read in the outer wheel- and bingo! you can directly read target's speed at the outside ring Wondeful tool, isn't it?

Stay tuned, I will post a downloadable template ASAP for the rear part of the wheel with a tutorial

---
Thanks Hitman! Can't wait- I've been having great fun using Cap'n Cox's Is-Was (AOB side) hope my tutorial was helpful!

Cheers M8

[Captain Krunch]

Everyone, the good folks over at the Historic Naval Ships Association have posted "Submarine Attack Course Finder Mark 1 Model 3 Manual, O.D. 453", so we no longer have to guess how the heck to use the Is-Was! In addition, this manual has some fairly clear images of the back side of the Is-Was, so I might eventually be able to complete what I've already put together - but I probably won't be able to get to it for a while, so anyone else can feel free to step up and create the back side of this thing.