IN PRAISE OF THE LOWLY MEGAPHONE
by David N. Goodchild

In our modern-day, microchip, fibreglass and satalite-driven cruising habits, we seem too quick to forget some old devices and ideas which are still highly serviceable after many centuries. The lead line is one of these. It will never fail you while your solid-state, electrically driven depth finder may well do just that. The lead line is not dependent on battery condition, satellite availability or highly skilled maintenance technicians. It works as well today as ever and should be on every cruising boat that ever ventures away from its moorings.

The megaphone is another such device.

A very ancient construct, it is as good today for bellowing commands to the foredeck crew as it is for issuing a pleading and gently persuasive request to the idlers on the dock to "take my lines, please?". It does not rely on batteries, maintenance or anything other than the human voice and simple physics. While it is not an amplifier per se, (it primarily focuses and directs the sound waves of the voice when used), this focus and direction does in fact achieve a surprising amount of "amplification" when used.

I made mine from some old copper flashing that was removed from the roof when it was re-covered about 20 years ago; I never throw anything away that could even remotely be used again, and this habit has never failed me!

To make the megaphone, (basically a simple cone with a mouthpiece) I first turned to my library and The Master Handbook of Sheetmetalwork with Projects, by Percy W. Blandford, published in 1981 by Tab Books, Inc., of Blue Ridge Summit, PA 17214.

These were the instructions I followed in order to lay out the cone, and I quote:

ROUND CONES

"A cone with a round base is easier to develop than one with a square or other straight-line base. A side view will already show the length to be used as radius (Fig. 6-11A), so there is no need to find the equivalent of the true length of a side of a square cone. A line drawn with a compass having its point on the apex of the cone will give the developed shape of the base, but what is not so easy is getting the length around the base.

Draw a semicircle below the side view [drawn in scale to the size you wish for the finished megaphone]. Divide its edge into any number of equal parts such as six (Fig. 6-11B). Set dividers to the width of a part and step this off around the developed bottom line 12 times (to represent a full circle). This gives a very close approximation to the developed length around the circumference (Fig. 6-11C). In effect, the dividers are stepping off chords across a small circle on a larger one. With only a small number of steps, the difference would be enough to make a noticeable error in the developed length. But with 12 or more divisions, accuracy is sufficient for practical purposes. Looked at another way, the dividers are stepping off the equivalent of a 12-sided cone instead of a round one.

A truncated cone [which is what the megaphone is] is dealt with in a similar way by drawing another arc to mark the top edge (Fig 6-11D)."

I followed these directions in laying out the shape of the megaphone on a paper pattern. This I closed up to check the size. My megaphone measures 12 1/2" from mouthpiece to bell, with the bell diameter being 8" and the mouthpiece with it's mahogany cover (see below); 2". When I had it the way I wanted it I used the pattern to lay out the cone on the copper flashing. I then cut it out on the bandsaw.

I found that I could not just overlap one side of the cone on to the other and fasten it; it distorts the cone, so I cut a narrow piece of copper from the same piece of old flashing and riveted the two halves together. These were pop rivets, and yes, you can get copper pop rivets from any decent hardware store! No deadly electrolysis in MY megaphone! I ran a bead of solder along both sides of the overlapping piece just to tidy it up and because I like to solder.

The handle was formed from a piece of 3/8" ID soft copper tubing. I bent it into a semicircle (carefully, so as not to crimp it) and then flattened each end with a hammer. These I riveted to the megaphone over the overlapping strip.

I wanted a smooth edge to the business end of the megaphone because the copper was sharp so what I did was to simply form a another piece of soft copper tubing, (3/16" ID this time), into a circle to fit around the mouth of the megaphone. This I soldered on to the edge. After it was all cooled, I gently hammered the edge round and put a little more solder in.

For the mouthpiece, I used two hole saws of mildly differing diameters and cut out a mouthpiece from scrap mahogany. The two hole saws used in succession made a neat little cylinder. Some epoxy on the small end of the megaphone and a little varnish and the megaphone was done.

What's the best part of this wonderful old device?

I can't wait to hail some passing ship with "Halloo the steamer! Will you report me sir!"

Wow!