The problem with all the battery-powered burglar alarms we have found at hardware stores is that the alarms were neither louder nor more frightening than a chirping canary. We needed something that would scare the jeans off an intruder, be easy to set up on a sailboat and, we hoped, keep us from a physical confrontation. I finally found the plans for just what we needed by going to YouTube and using the search terms “awesome alarm idea.” I followed the general concept but made some powerful modifications.
Here’s everything you need: a Piezo 110-decibel DC 6- to 12-volt alarm, 9-volt battery holder, small hot glue gun, soldering gun, flux, solder and jumbo plastic clothespins. All these items can be bought on eBay. At extra cost, the 9-volt battery holder comes with a shutoff switch, but I saw that as just one more thing to corrode. The clothespin could be replaced with a sturdier outrigger clip used for fishing. I cut up an old plastic ID card for the slip trigger, but an old credit card or popsicle stick would also work.
The stainless-steel contacts and wires hot-glued to the jumbo plastic clothespin.
The YouTube guide was great because it showed the proper soldering technique needed for making the connections. I hot-glued in place the holder for the 9-volt battery and the largest, loudest Piezo alarm we could find. Small stainless-steel pan-head bolts served as the opposing electrical contacts and the positive electrical wires were soldered to them. Hot glue was used to cover all electrical connections and help seal them from moisture.
We put the mobile alarm in a plastic bag for weather protection, then held it down with dive weights; you could also tie it from the metal spring clip in the clothespin to the coach roof or cockpit coaming. The trip line is thin sail thread that is more difficult to work with than twine but certainly less likely to be seen by an intruder. The free end of the trip line can be tied to a lifeline, companionway slat, jerry jug or anywhere an intruder might pass. When the trip wire is snagged, the slip trigger pops free, closing the contacts and setting off the alarm.
This alarm is so loud that demonstrating it to fellow cruisers makes them jump at least out of their sandals.
Patrick Childress voyages with his wife Rebecca aboard their Valiant 40, Brick House.