# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: A Diy E6-B?
From: Paul Hirose
Date: 2021 Apr 13, 17:00 -0700

```On 2021-04-13 8:45, Tony Oz wrote:
> I can't figure out how to label the concentric arcs on the slide, - what
> radius step to use? I suppose it is NOT arbitrary.

Actually, radius step of the speed arcs *is* arbitrary. If the radius
scale is linear the device will work, regardless of the numbers you
choose. Sometimes the slide has a different set of numbers on each side.
Mine is 30 - 260 on one side, 150 - 700 on the other. The latter grid is
shorter to make space at the bottom for the rectangular grid Dave
mentioned. But a double wind grid is not universal, as you can see in
the selection of E-6B computers at this site:

https://www.mypilotstore.com/MyPilotStore/secp/22

The speed range can be extended by mentally multiplying or dividing by a
factor such as 10. For example, the 30 - 260 grid can be used to solve
set and drift problems for 3 - 26 knots.

The Jeppesen CR computers have a completely different wind solution.
They resolve the wind into tailwind and crosswind components. The
tailwind component is mentally added to true airspeed to obtain ground
speed. The crosswind component is converted to wind correction angle via
a sine scale.

This method eliminates the wind slide and permits a much smaller
computer. However, the mental workload is greater. These computers can
be recognized by their perfectly circular shape.

--
Paul Hirose
http://sofajpl.com/
```
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