Motion Alarms on Deck

[gmnord]

We are returning to sail ST Vincent & The Grenadines this spring. We are considering bringing along a battery powered (9v, with remote arming dongle that uses AAs) motion alarm. We have found a well reviewed unit for about $25 that has a very loud (120Db) audible alarm and a bright strobe. It covers about 120 degrees and we are thinking to place it in the cockpit to detect overnight intruders (or, even daytime...given the alarm is quite loud and will draw attention).

The alarm i am looking at is from UniqueExceptional for $25.

I have read one reviewer of the device that has used it successfully internal to the cabin. But I prefer to place it on deck to catch an intruder before they get to the point of opening a cabin hatch

Does anyone have experience with using these above decks? Would sea or dinghy motion possibly trigger it (this I believe uses visual motion, but may use infrared, i need to check on that...)?

Preferably I think I'd mount it at the companionway hatch, or base of the mast, facing the aft end of the cockpit. Alternatively it could be placed in a corner of the port or stbd cockpit quarter. Has anyone had experience placing these?

[skipmac]

If you place a motion detector on deck just be aware that it will detect any kind of motion. If the boom isn't in a crutch or in some other way secured against any motion then when the boat rocks in a wave or wake the boom swinging back and forth will set off the detector.

Likewise any flapping canvas, loose lines (if they are close enough to the sensor) and don't forget passing seagulls.

If the sensor high enough or set at an angle that includes the water around the boat then waves or even the boat rocking can also set it off. Careful settings for range and angle can deal with this.

So on deck careful placement and settings are the key to minimizing false alarms.

[Lizzy Belle]

Originally Posted by gmnord

given the alarm is quite loud and will draw attention

It's always nice to wake up due to a loud alarm when a bird lands on a neighboring boat

As skipmac said: very, very careful placing and please just enough loud for you to hear, not for the whole anchorage to enjoy the alarm.

[Bill4]

Originally Posted by Lizzy Belle

It's always nice to wake up due to a loud alarm when a bird lands on a neighboring boat

To the OP: Why not spend a little more and fit an alarm system with pressure sensors that fix underneath the deck / cockpit?

[skipmac]

Pressure switch under a mat or grate in the cockpit is good. Also you can buy cheap alarms that use a trip wire.

Regarding loud. I really, really do appreciate the concern about waking the neighbors. Used to be a guy down the block whose house alarm would go off every month or so, inevitably in the middle of the night, and wake everyone (everyone meaning me) in the area and I have little patience for this.

However, one of the deterrents of an alarm is the noise. First so the intruder knows that all the neighbors will be alerted and with sirens that put out 120 dB, loud enough so the noise can be painful to the intruder and just the sound make him/her want to leave.

So, how to balance being nice to the neighbors vs security? Mainly I say to eliminate false alarms. Personally if one of my neighbors boat was being broken into I would want to know about it. If was a false alarm, then three strikes you're out and I would have a serious discussion with the neighbor. If that didn't work the wiring might spontaneously become defective.

[David M]

Don't become the boat that cries wolf. Nobody will like you or your boat.

[Lizzy Belle]

As a single gal afloat, I have given security some thought too.

This is what I have opted for:



Nice and quiet, and should be enough to not be the easiest boat to break into.
Also kinda counting on being the smallest boat, moored close enough to more expensive boats which look like better prey

[gmnord]

Thanks for all the great advice everyone!

Unfortunately, we are chartering, not sailing our own boat, so I can't take any option that involves modifying the boat. But your suggestions still were helpful in clarifying some of my expectations.

We had chartered SVG last year, and generally were not too worried about boardings then, nor are too much now. Watching CSSN postings from the past year, it does not appear that there is high threat level (maybe not much different, really, from risk of a break-in at our land home, though we do live in a pretty quiet, small town). We also do watch for where problems have been persistent (e.g., Canouan) and generally have been able to anchor last year (and plan this year) in places that have had little to no reported problems.

But we may sleep a bit more relaxed having some form of warning system.

Taking it all in, I'm going to proceed with the unit I had in mind -- very portable, and easily adapter to mount pretty much anywhere on the boat. From comments everyone has made, I suspect placing it in the aft quarter of the cockpit, low in the cockpit (really need only to detect feet) and facing the companionway, may work just fine and minimize chances of false alarms. Hopefully, that would avoid any objects that might swing from the boom or lifelines, seagulls (so long as they don't invade right to the cockpit floor), etc.

While this unit reportedly has a VERY loud siren, it also has a chime mode, which we could use to test it. Possibly, the chime and the bright strobe might be enough to ward off a boarder. I completely understand and respect the concern for a loud siren waking everyone in the anchorage -- i've always hated car alarms for that same reason. But a genuine boarding probably should wake the anchorage, or there may be some risk that the boarder might try another boat being scared off ours.

Thanks again! We sail second half of February into early March. I'll report back here with results at that time.

[tomfl]

Bought one from Harbor Freight, guess it is in the same class as the one you mentioned. I have a Seawind cat and put it in the saloon facing aft. I had to basically be on the boat in the cockpit for it to sound. I moved it so it was facing down one of the sugar scoops and when I got on the sugar scoop it sounded, so I would have to buy two for the boat to be protected. I also noticed that when I tied my inflatable so it floated behind the sugar scoop it would sound if there was any wind or current, but this was sorta what I wanted and it would warn me if a strange boat approached. Mine had an alarm that could be located next to my bunk below and did not really make that much noise. For the $US30 I paid for it I was happy with it. The thing is I was never really in a place where it seemed dangerous for me to need it.

[bobw100ton]

I would not recommend a motion alarm but rather an infrared sensor type. If you have an unobstructed view between two points in the cockpit it would work fine with out being sensitive to other motion. They are available for under $50 and reasonably portable.

[bsurvey]

thumb tax are cheaper, laid around the cockpit and the deck coamings pick up easy with a magnet.


if its that bad their why go

[skipmac]

Quick, easy, cheap and 99.9% false alarm proof. Buy an alarm that activates by pulling a small pin attached to a trip wire. Will not sound unless something kicks the line and pulls the pin.

Make the trip line from a piece of small, thin monofilament fishing line which is almost invisible even in daylight. Set that across the path a boarder would take to the companionway. Get two or three to cover several areas.

[Symphony]

Gmnord ,
your $25 battery motion sensor sounds like a great item to test. Freedom from wiring, wired power, or tripwire attachment points means you can move it around to find a good spot, especially since you are chartering. $25 wont break the bank if it is a failure or corrodes in 90 days. Cost matches the amount of the perceived threat with the recent CSSN reports.

[reed1v]

Agree that infrared motion detectors are the way to go. But a good system will cost you more that $50. Any security shop can rig you up a fairly foolproof system that will not give a lot of false alarms. We rigged ours up to the spreader lights so anyone coming on board triggered the spot lights and an internal alarm. Lights are enough to scare most if not all bad guys away. False alarms thus did not wake up the entire city.

As in a previous post on another subject, two ratty dinghies tied to the rails will make any boat look like a lot of folks aboard. In Cape Town we used three old row boats(little dinky things) that made the boat look like an army was aboard. Never a problem even as our neighbor Oyster got broken into time and time again.

[Looking4Neptune]

I agree, the trip-wire is the least likely to have false alarms and still do a good job. And inexpensive.

There are tons of more fancy options. Here is a recent review of security cams that hook up to your wifi network. Most have alarms, night-vision and can even stream video to your mobile phone. This could allow you to monitor from on-shore, even across the globe (assuming your boat has good internet access, maybe in a marina or anchored close). If I was going to leave my boat somewhere for a while, I'd feel better having a setup like this and some local friends I could call if there was a problem. But these are more $ ($180 - $300) and some can take a while to get familiar with.

Pat