Bearing Rate Computer slide rule - Page 2

sharky02 · 11-23-10, 01:07 AM

Dear all,
I have a bearing rate computer slide rule, but I do not know how to use it. Please anyone tell me how can I use this rule and what is the goal of using it?

Pisces · 11-23-10, 10:57 AM

Multiplication and division of numbers, with nautical meaning in this particular case. There isn't one way to use it. It depends on the formula you need to use. And what you know, and which variable you are after. It's very flexible.

Look at PusterBill's top image. On the top you see 15 knots aligned with 7.2 degrees (ish) of bearing rate. If you want to know how many knots would be needed (or are sufficient)for a 1 degree bearing rate then you keep the disks aligned as they are, and follow the numbers back to 1 on the bearing rate scale. Opposite of it you will find the number 2.08 (ish). Now you did a division by 7.2 (15/7.2=2.08333...)

Basically going around the scales you multiply or divide. For example, on the knots scale a halve lap clockwise is a multiplication of 10, or counterclockwise a division by 10. A full lap is multiplication/ division by 100. A quarter lap is a little more than 3 times bigger or a third smaller (depends on the direction) Though the actuall number might show less or more zeros at the end. You need to keep an eye yourself on where the decimal mark ends up in the resulting number. That is an easy mistake to make.

Another example, if you want to know how wide an angle of 10 degrees is at 4050 yards (bottom image of PusterBill) then you need to multiply 4050 yards by the sine of 10 degrees. (the angle scale is a sine scale) See that 90 degrees is opposite 4050 yards. The sine of 90 degrees is equal to 1 on the left side of the 90 mark. (But about 0.57 degrees at the right side of the mark. Why? sin(0.57)=0.01) Now go over looking at 10 degrees and you'll find about 700 yards on the adjacent scale. Or 4050 x sin(10 degrees) is 4050 x 0.1736. Grab your scientific calculator and compare with other numbers.

If you want to learn more I suggest you learn more about sliderulers that are based on a logarithmic scale.

BTW here is a better quality image of how it should look like.

For those that want to make a DIY version of it. The Range in yards should be visible through the top disk, that contains only the bearing rate and angle scale. The bottom disk contains only the Speed/knots scale and the range/yards scake. Using the Pusterbill's images on the other page (with the 2 most outer scales seperated from the 2 most inner scales) might be difficult to recreate this.

kgsuarez · 11-23-10, 12:47 PM

That looks really nice. I am going to have to give this a try. This would make a great addition to my slide rule collection.

I wonder if I could take care of most of the project by going to a Kinko's. I'm sure they have most of what I would need.

micky wannop · 01-13-11, 04:35 AM

i can send it to anyone who want with instructions on use i used it for real for 23 years yes they still use them in the royal navy submarine service although its a dying art

naseem6611 · 06-05-12, 04:56 AM

am serving on conventional submarine, i want to know the complete procedure on use of bearing rate computer brother above me can help

11-23-10, 01:07 AM	#16
sharky02 Nub Join Date: Nov 2010 Posts: 2 Downloads: 2 Uploads: 0	How to use the bearing rate cumputer slide rule Dear all, I have a bearing rate computer slide rule, but I do not know how to use it. Please anyone tell me how can I use this rule and what is the goal of using it?

11-23-10, 10:57 AM	#17
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,904 Downloads: 304 Uploads: 0	Multiplication and division of numbers, with nautical meaning in this particular case. There isn't one way to use it. It depends on the formula you need to use. And what you know, and which variable you are after. It's very flexible. Look at PusterBill's top image. On the top you see 15 knots aligned with 7.2 degrees (ish) of bearing rate. If you want to know how many knots would be needed (or are sufficient)for a 1 degree bearing rate then you keep the disks aligned as they are, and follow the numbers back to 1 on the bearing rate scale. Opposite of it you will find the number 2.08 (ish). Now you did a division by 7.2 (15/7.2=2.08333...) Basically going around the scales you multiply or divide. For example, on the knots scale a halve lap clockwise is a multiplication of 10, or counterclockwise a division by 10. A full lap is multiplication/ division by 100. A quarter lap is a little more than 3 times bigger or a third smaller (depends on the direction) Though the actuall number might show less or more zeros at the end. You need to keep an eye yourself on where the decimal mark ends up in the resulting number. That is an easy mistake to make. Another example, if you want to know how wide an angle of 10 degrees is at 4050 yards (bottom image of PusterBill) then you need to multiply 4050 yards by the sine of 10 degrees. (the angle scale is a sine scale) See that 90 degrees is opposite 4050 yards. The sine of 90 degrees is equal to 1 on the left side of the 90 mark. (But about 0.57 degrees at the right side of the mark. Why? sin(0.57)=0.01) Now go over looking at 10 degrees and you'll find about 700 yards on the adjacent scale. Or 4050 x sin(10 degrees) is 4050 x 0.1736. Grab your scientific calculator and compare with other numbers. If you want to learn more I suggest you learn more about sliderulers that are based on a logarithmic scale. BTW here is a better quality image of how it should look like. For those that want to make a DIY version of it. The Range in yards should be visible through the top disk, that contains only the bearing rate and angle scale. The bottom disk contains only the Speed/knots scale and the range/yards scake. Using the Pusterbill's images on the other page (with the 2 most outer scales seperated from the 2 most inner scales) might be difficult to recreate this. __________________ My site downloads: https://ricojansen.nl/downloads

01-13-11, 04:35 AM	#19
micky wannop Nub Join Date: Dec 2001 Location: helensburgh Posts: 3 Downloads: 8 Uploads: 0	i have one i can send it to anyone who want with instructions on use i used it for real for 23 years yes they still use them in the royal navy submarine service although its a dying art

06-05-12, 04:56 AM	#20
naseem6611 Bilge Rat Join Date: Jun 2012 Posts: 1 Downloads: 6 Uploads: 0	bearing rate computer am serving on conventional submarine, i want to know the complete procedure on use of bearing rate computer brother above me can help

11-23-10, 12:47 PM	#18
kgsuarez Planesman Join Date: Oct 2004 Location: USA Posts: 181 Downloads: 28 Uploads: 0	That looks really nice. I am going to have to give this a try. This would make a great addition to my slide rule collection. I wonder if I could take care of most of the project by going to a Kinko's. I'm sure they have most of what I would need.