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

[Captain Krunch]

Over at the Historic Naval Ships Association Board, a gentleman by the name of Mike posted pictures of a Submarine Attack Course Finder (Is-Was) from 1943. The story goes that a family member picked it up for him at a gun show for $5. If you look at his photos, you'll see that it looks like it was made yesterday, so I'm betting that Mike has a very rare find.

Being without an Is-Was myself, but wanting one very badly, I did the next best thing and made my own! Using Mike's high-quality photos, I was able to make what I think is a pretty fair recreation of the main side of his Is-Was, using MS PowerPoint as the drawing program. After creating it in Powerpoint, I converted it to Adobe PDF, and am making the file available for download here.

Mike said his Is-Was was 7 1/4 inches in diameter, so I made this one that size as well. The first two sheets (The A and B rings) should be printed on heavier card stock, while the second two sheets (The C and Periscope ring) should be printed on transparancies.

I'm halfway done with the second side of the Is-Was, but I'm having problems in figuring out the middle "Bearing in Degrees" ring. The line spacing does not appear to match up with any other standard circular slide rule markings, so I'm not sure if I'll ever be able to complete it. If anyone has any ideas, let me know.

Having played with the Is-Was for a few days now, I think I've figured out how to use it, although there are still a few things about it that bug me. This is what I assume the rings are used for:

A Ring - Represents the submarine, and shows relative bearings
B Ring - Represents the sub's true course/bearing
Periscope Ring - Represents target bearing
C Ring - Represents course and angle on the bow of the enemy vessel

This works for the most part, but there are a few design issues that bother me:

a) I feel that the protrusions on the A Ring are backwards. I always think that the pointy end represents the bow of the sub, and the half-cirlce represents the stern - but if the A Ring is used to represent the sub, then the half-circle is located at the 0-degree marker. This seems counter-intuitive to me.

b) The Periscope Ring should have a more obvious marker to show where AoB is. I know it is 180 degrees from the actual "Periscope" marker, but in the heat of battle, it's easy to forget. I may add a marker to clearly show the AoB.

Despite that, it's going to be a pretty cool toy to use once SH4 arrives. So, please enjoy the Is-Was!

Krunch

[fire-fox]

Very nice find! ill D/L it when i get home from work, any idea if there is a rivers side to the real one and if there is are there any plans for you/any one else to make it?

EDIT: sorry just read the secound half of your post and feal prity thike as you already answerd this Q.

Very Cool Krunch - thnx a mill for the work

As for materials - tranperencys wont cut it as you wrote on HNSA (can't answer there as i have no account), but if you make the layer in transparent paper and then laminate it with the thikest lamination you can get (paperstors usualy can do that for you pretty cheep) then i think that will work.

Would it be hard for you to make a version where all the pages (wheels) are all white? I would like to make the colorisation by the use of colored paper (off white etc.)

Hmmm in construction it pretty much resembles a Nasmith Director witch was allso a Target Course Finder.

[Captain Krunch]

I agree that transparencies are not the best solution, but at least they're readily available to most people. My mock-up was made out of card stock and transparencies, and it seems to be holding up fairly well. But I like your idea of using clear lamination to give it strength; that's a lot simpler than what I was going to do (Which was make decals and put them on clear styrene sheets).

It's no problem to make a complete black and white one; it'll be a day or two at most.

I used the lamination method on all the transparent of Kim's Tools some time back, and it holds out really good, and they are pretty stiff as well.

Im not in a hurry here, so whenever you see fit - im just glad you take the time to make it

[Dustyboats]

Originally Posted by Captain Krunch

I agree that transparencies are not the best solution, but at least they're readily available to most people. My mock-up was made out of card stock and transparencies, and it seems to be holding up fairly well. But I like your idea of using clear lamination to give it strength; that's a lot simpler than what I was going to do (Which was make decals and put them on clear styrene sheets).

It's no problem to make a complete black and white one; it'll be a day or two at most.

I bought three different sized, circular plastic, school boys protractors. Cost UK £2.

[Rykaird]

Originally Posted by Captain Krunch

Over at the Historic Naval Ships Association Board, a gentleman by the name of Mike posted pictures of a Submarine Attack Course Finder (Is-Was) from 1943. The story goes that a family member picked it up for him at a gun show for $5.

I have seriously got to go to my first gun show. I thought they only had guns - not cool historical sub stuff.

[Captain Krunch]

I've posted an all B&W version of the Is-Was here. Let me know if there are any problems with it.

Originally Posted by Captain Krunch

I've posted an all B&W version of the Is-Was here. Let me know if there are any problems with it.

File was deleted.
Reason: Deleted by uploader.

Thats what pops up when i click the link 8th march 2200 GMT

BUHUUHUUUuuuuuuuu

[Captain Krunch]

Wow, that's weird, sorry about that. Try this link; it seems to be working for me:

B&W Is-Was

That one worked like a charm - much appreciated

[Captain Krunch]

First off, I'm glad to see interest in the Is-Was I made; I hope it helps people enjoy SH 4 even more.

Regarding transparency, the original had both the C and Periscope dials clear, but after your comments, I don't see why the C dial couldn't be printed on paper. But the Periscope dial must be clear so that you can see the values underneath.

The way I believe the wheel works is like this. Prior to a ship sighting, the A and B dials can be pre-set together to your heading, with the "0" degrees mark of the A dial representing the front of the ship, and the B dial showing true heading of the ship, by placing the heading value at the A dial "0" degrees mark. So if you're heading due east (90 degrees), then the A dial "0" degrees mark = the B dial "90" degrees mark.

So let's say you're traveling due east, 90 degrees. Then suddenly, you get a ship contact (Via sonar, periscope, etc. It doesn't matter). "Sir, new contact, 300 degrees relative!" What I do is I move the Periscope dial so that the triangle is over the A dial "300" degree mark. This is also equal to a B dial value of "30" degrees. The B dial can now tell you what true heading to take if you want to head straight for the contact. "Helm, make new course 30 degrees".

But let's pretend you don't change course. Ok, now the last bit of the puzzle is Angle on the Bow. You have two ways to use this. First, if you can determine the true course of the contact via plotting, you can input the contact's heading to determine AoB. "Sir, contact heading is plotted out to be 330 degrees!" You do not move the A, B, and Periscope dials; you move the C dial until the "0" degrees mark of the C dial is pointing to the "300" degrees mark of the B dial. When you do this, you look at the Periscope dial marker 180 degrees opposite the Periscope triangle. This marker points at "120", on the left side of the C dial ship, so this tells you that the contact AoB is 120 degrees port.

On the other hand, let's say you visually estimate the AoB, and decide it to be 100 degrees port. You move the C dial "100" port value so that it matches up with the Periscope dial marker that is 180 degrees opposite the triangle. When this is done, you can then determine via the B dial that the contact's heading is 310 degrees true.

Once this is done, you decide to make a direction change, and head straight for him. You do not move the B, C, or Periscope dial; instead, you just move the A dial so that the "0" value matches up with the Periscope marker that you had already preset above.

That's probably a way-too-verbose answer, but I hope it helps. I suggest playing around with it for a while, and eventually you'll get the hang of it. Good luck!

[Miimike]

The back side is the run time calculator.

[Hitman]

Sorry sqk7744 but I think you got it wrong Though I might be wrong, of course, but see if this example seems more correct:



1.- Our own ship true course is 90, as highlighted in the red circle or our own ship BOW. The target's true course is 300º.

2.- We need to turn the scope left 60º, to our relative 300º, to see the target. The A ring scale is inverted exactly for that. When we turn the upper part of the scope left (Yellow arrow) we can correctly read in the opposite part of the scope ring that we have gone to the "300" mark of the A ring (yellow triangle marker in the handle), i.e. of our relative bearing. We also can see now in the middle ring (B ring of true course) that the relative course to our target would be 210º for us.

3.- Finally the AOB of the target can be read in the other scope ring marker (Highlighted with a green triangle). In this case it is 90º, not 120º as you had indicated. You got the wrong result because you reversed the own ship. This can be seen clearly in this edited picture of your setup:




Hope that helps

EDITED to add:

The tool is in fact, as the name says, a "course finder" so in real life the inputs of the tool would be: 1) Own true course, 2) Target bearing and 3) Target AOB. With that input the tool would give you as output the true course of the enemy.
But in SH4 as in SH3 people tend to do the opposite, i.e. determine first true course of target and use the tool to get the AOB. Probably as someone highlighted in another thread, this is due to the AOB being more difficult to determine in a flat screen as opposed to real (3Dimensional) world, but anyway the real use of this wiz-wheel comes to be very clear when you play at 100% realism, i.e. with no map contact update and view limited to your bridge/scope/TBT.

Also, another problem with this wheel is that in SH4 we are used to see in the upper part of the scope the graded reticle for the target bearing, so we tend intuitively to look for the bearing in the upper part of the scope. But when doing so in this wheel, the AOB would be reversed! This is the main reason why the scale is reversed in the A ring: That you can have in the same marker (Scope ring handle) both target bearing and AOB. If you put one of them in the opposite side, you get a wrong reading, and if you put both in the other extreme, you have a reversed result.