FAQ Friday #53 – What measurements are needed to make an elephant trunk / transom drainage sock?

All of our elephant trunks / transom drainage socks are made to order. This means you can choose not only the colour, but the size too. We therefore need some measurements...

Length
Length is usually the easiest to measure and is how long would you like the trunk to be. Length can be easily measured with a ruler or tape measure. If you’re wanting the Hypalon fabric trunk joined onto the moulding then the length includes the length of the flange on the elephant trunk moulding as shown below.

We then need either a measurement of either the circumference or diameter...

Diameter
If you have callipers then the diameter of a solid circular moulding can be straight forwards to measure. However, if you have a rubber moulding, then the moulding might already be slightly distorted and the measurement you take might not be that accurate.

Circumference
My preference would be to use a tailors tape measure (a fabric or ‘soft’ tape measure) and provide a measurement of the circumference rather than diameter. If you don’t have a tailors tape measure then using a strip of paper to measure around the fitting can work. I wouldn’t recommend using string, wool or anything else that is stretchy as it’s easy to end up with a measurement that isn’t accurate. Don't forget to start and finish measuring in the same place too! Personally I like to butt the end of my tape measure into the seam of the trunk so I know exactly where I started measuring.

The diagram below illustrates both circumference and diameter:

Note
Squashing your old trunk flat and measuring the width is not the diameter… And it’s only approximately half the circumference. We strongly recommend NOT measuring the circumference in this way as it’s not accurate enough.

What unit should I measure in?
We happily receive measurements in imperial (feet and inches) or metric (meters, centimetres or millimetres), or even a combination of both. We’ve made many trunks where the diameter or circumference is provided in cm/mm, but the length is an easy round number of inches, for example 70mm diameter and 18inches long.

Hopefully this FAQ Friday post helps you order a new elephant trunk for your boat with confidence.