Tips for Divers

The DIY blog for DIR divers

How to replace the compass arm band with a rubber line


A special DIR mount for the Suunto SK7 compass

A special DIR mount for the Suunto SK7 compass

With the supplied standard straps, which are provided when you buy a compass, the disadvantage is that they are usually awkward to use with gloves, and they are – if needed – not easy to be tighten underwater.

Here is an easy way to replace the standard strap with two rubber lines (known as bungee line). There are two ways that you can precede with this. Both of which I would like to introduce to you today.

The Compass

Compass capsule and setting

Compass capsule and dial

A good compass for diving consists of a capsule and a setting for the number of degree for navigation. The compass is mounted in an oil capsule, which can also handle a few degrees in the horizontal skew. The advantage is the compass does not tile by a slight angle and gets stuck. The second part is the dial for the number of degrees. This dial is used for navigation. This can be easily adjusted and maintained to a given course.

Option 1: The DIR-mount for the compass

The possibility to equip the compass with a rubber line is a so-called DIR-mount (see picture at the top of this post). A SK 7 Compass by Sunnto is an example of the following.
The DIR-mount is a plastic housing on two rubber lines which can be attached by several holes. These rubber lines can be then brought over the wrist and secured so that the compass sits securely on your arm.

The DIR-mount has six holes on each side. This allows you to attach the rubber lines optimally. It is also possible to arrange the compass so that it can be worn on the arm at an angle. As a result, you must not completely straighten your arm in front of your face to be able to read the compass. The modification is quite simple:

Step 1: Modifying the DIR-mount – place the compass capsule

Step 1: Modifying the DIR-mount - place the compass capsule

Step 1: Modifying the DIR-mount – place the compass capsule

After removing the compass capsule and the dial from the standard mount, first press the compass capsule into the DIR-mount. North should be shown as upwards! The DIR-mount has a small notch where it can be orientated. With the connection still, attach the dial to the number of degrees and you’re ready!

Note: When attaching the control dial you have to be careful! The wheel is fastened on by four pins in the housing. The pins are very thin and can break easily when the wheel is pressed into the DIR-mount incorrectly.

Step 2: Modifying the DIR-mount – length of rubber lines

Step 2: Modifying the DIR-mount - length of rubber lines

Step 2: Modifying the DIR-mount – length of rubber lines

When your capsule and dial have been integrated into the mount, attach the rubber lines to the DIR-mount. As seen in the picture on the right, there are multiple holes on the side of the DIR-mounts.

From below, thread your rubber lines through one of the holes. The simplest way now is to tie a knot in the two ends of the rubber lines, so that they are secure and you can place the DIR-mount on your arm.

The elegant variant is, where after you have threaded it up through the hole, to put it down through one of the other holes. If a node is now at the end of the line, that node should disappear below the DIR-mount.

For function, it does not matter which option you choose. For appearance, method number 2 is the more elegant way.

If you previously set the length of rubber line and it was too long, even underwater you can simply just put another knot in the line that sits close to the arm of the compass. Even when diving suits have different thicknesses, the rubber lines can be shortened or lengthened according to the looseness of the knot.

Option 2: Thread the line through the standard rubber casing

The second option, used to replace the standard rubber line with two lines, optimises the use of the housing that was originally supplied with the compass. You only need to remove the straps and put the rubber line through the housing of the compass.

Instructions about that way, I have already posted in the article How to replace computer watch straps with rubber lines.

Advantages of the rubber lines are:

  • The advantages of the rubber lines, in contrast to the standard straps are quite obvious:
  • Easy install / uninstall of the compass, through the flexible rubber casing
  • More security with two rubber lines as opposed to the standard strap
  • Easily adjust the rubber lines if they are too long; e.g. for different diving suits.


Result: SK 7 compass (Suunto) with a DIR mount

Result: SK 7 compass (Suunto) with a DIR mount

You can see the  result here in the picture.

The compass is sitting in a DIR-mount. On the left and right of it you can see the two loops of the rubber line that are pulled over the arm. The compass is therefore fixed securely to the arm by very simple means and can easily be called upon when needed, by the arm.

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