> Is floatation important?
Flotation has always seemed marginal to me. Your first line of defense should be the lanyard. If your mirror is tied to your life vest or body, you're good. If it isn't, the mirror can be left behind, or float away.
However, lanyards can break (though they are typically nylon), and I have had the square knot in a mil-spec lanyard come undone on me. Flotation provides a second chance if the mirror fails in deep water. It's not a sure thing, though - retrieving your mirror in rapid or choppy water is iffy at best, and who's to say you'll notice that you dropped it in the first place - in an emergency, you are likely to have a lot on your mind.
Most US Coast Guard approved life raft mirrors don't float, though the USCG standards seem to predate floating mirrors. The mirrors currently issued to US Coast Guard personnel do float, I believe. The U.S. Military buys both glass and plastic buoyant signal mirrors, so they aren't hard over on flotation. Malcolm Murray, who is probably the most dedicated signal mirror maker I know, makes both floating and non-floating mirrors.
> What about the aiming devices?
Hands down, you want a retroreflective aimer - you'll put far more flashes on the target than with other methods. This is backed up by rigorous test data. The U.S. military uses retroreflective aimers nearly exclusively.
Just make sure your mirror has a real retroreflective aimer, not a non-functional picture of one - see Doug Ritter's article here:
http://www.equipped.org/phony_signal_mirrors.htm[Disclosure: I provided two diagrams, and the patent and MilSpec for that article.]
Since retroreflective aimers don't work when the sun-mirror-target angle is more than about 135 degrees, you should also learn a backup method, like the "finger-vee" ( I have deep reservations about "finger-vee", but this post is going to be way too long as it is.)
In WWII, the US Bureau of Standards, in conjunction with the US Coast Guard, after testing many mirror aiming approaches, selected four for a rigorous scientific test. Six novices received brief training, then were put in a liferaft in choppy water, and asked to signal to a circling scout plane by each method. An observer on the scout plane counted the flashes they saw. The average results over the six subjects, in flashes seen per minute:
(1) Improvised foresight: 0.3
(2) British heliograph-style" mirror with paddle foresight: 8
(3) American GE "cross-in-glass" rearsight mirror: 14
(4) Early retroreflector tab: 35
Bottom line: the retroreflective aimer was seen 2.5 times more often than the runner-up.
The U.S. reaction was to switch production from (3) to (4), even though they had hundreds of thousands of (3) in the field.
An independent British test of (2) and (4), using two samples of each type of mirror, from a dinghy to a circling plane, similarly concluded that the U.S. retroreflective tab aimer produced visible flashes at a rate four times that of the British and Australian paddle foresight aimers.
While neither test included the "finger-vee" method, which is a "foresight" method, I would expect the "finger-vee" to be significantly worse than method (2): more than four times less effective than a retroreflective aimer. Lining up the 0.52 deg wide sunbeam shadow spot with the paddle foresight hole seems infinitely more reliable to me than using two fingertips to locate the center of a rectangular beam to that accuracy. However, a rigorous comparison test would be welcome.
Similarly, one can question the applicability of this test to the current mesh / solid / perforated retroreflective aimers, since the actual retroreflective aimer tested was a "canted tab" device. In U.S. service, the solid "bullseye" retroreflector replaced the retroreflective "tab" aimer, and was in turn replaced by the retroreflective "mesh" aimer.
You can see the three types on my site, in the first photo here:
http://www.richard-fowell.fotopic.net/c1663439.html Since both innovations were invented by the same scientist who conducted the U.S. test, the inference is that he thought the current mesh aimer was even better than the test results above would indicate. However, a rigorous new test would be welcome.
Another thing that could be argued is that in these tests, the unstable platforms used (U.S. liferaft, British dinghy) tended to overemphasize the importance of an aimer compared to a land emergency with solid ground. That seems valid to me, and a strictly terrestrial test would be of interest. On the other hand, a real-life survival situation is much more stressing than the experiments above - adrenaline makes your hands shaky, as does hunger and pain from your injuries.
I had to pay to get the full U.S. and British reports, but a condensed version of the U.S. report (which omits the British foresight data) is freely available here: "Signaling with Mirrors: Reflex-Button Type of Mirror Adopted for Navy Survival", Naval Aviation News, 15 Sept 1944, pp. 32-33, which can be downloaded from the official government site here:
http://www.history.navy.mil/nan/backissues/1940s/1944/15sep44.pdf> The retro reflective mesh-type aiming devices seem to
> vary from mirror to mirror - lots of people who have
> used mine find them a bit difficult to use and
> difficult to find the fireball.
The retroreflective aimers do require training, and are a bit non-intuitive. However, the training need not take long, done properly, and a few minutes of practice should lock it in.
A good training aid is a patch of retroreflective material 100 yards away (the license plate of a (parked, unoccupied) car is good), and they should practice flashing in various directions relative to the sun - flashing towards the sun is easiest, and the retroreflector will only work out to about 135 deg from the line to the sun. I've made up portable retroreflective targets for my mirror testing and training using automotive reflective tape. Practicing with each hand is also a good idea - in an emergency, one arm may be pinned or broken.
The aiming methods that may seem more intuitive, as shown above, produce woefully worse results.
The way to mitigate the training issue is to provide better training material and methods, which I'll try to do below.
While most such mirrors come with written instructions on the back, the US Air Force does not regard those as sufficient - every pilot is explicitly trained to use a signal mirror.
Consumers don't get that training as a matter of course, but there are some pretty decent supplementary instructions available in printed, diagram, Web and video form. Here are some links:
Web links:
(1) Doug Ritter's instructions
http://www.equipped.org/psp/psp_rescueflash.htm(2) My instructions
http://www.equipped.org/pp/pic2042.htm(3) Cody Lundin's instructions from "98.6 Degrees, The
art of keeping your ass alive!" (pp. 187-190 and
C12-C13 cover retroreflective mesh signal mirrors -
the best coverage I've seen in a commercial survival book)
http://tinyurl.com/signal-mirror-drawing(4) Gregory Davenport's instructions
http://books.google.com/books?id=7ZJjaNNgHhgC&pg=PA210Video:
(1) Air Force Academy retired survival training director
and operator of outdoorsafe.com Peter Kummerfeldt
lectures/demonstrates signal mirrors for 4:34 of this
5:28 long video clip online:
Raw video: Signaling : News : KXRM FOX 21
http://www.coloradoconnection.com/news/video.aspx?id=374547(2) Publicity video of May 2008 NASA signal mirror training
(short, note cap reversal to avoid shadow)
http://www.nasa.gov/centers/dryden/mov/228106main_mirror_640x360.mov(3) (A) "Be Safe with Ed Viesturs - Survival Essentials"
Go to:
http://www.adventuremedicalkits.com/ On the center of the page, click on:
"Be Safe with Ed Viesturs - Survival Essentials"
While the runtime on my machine is not strictly repeatable:
Signal mirrors are discussed at 00:35-01:50 and 03:40-04:08
The main tutorial is from about 00:45-01:50, and is reviewed
after Ed's farewell, from about 03:40-04:08
Notes:
(1) If you see a "slider bar" across the bottom of
the video, click on the vertical bar at the right
that says "AMK Video" to remove the slider bar.
(2) The video (probably unintentionally) illustrates
a common problem using signal mirrors - shading
the mirror with one's hat brim or cap. When the
subject wearing the baseball cap illustrates
finding the reflected light on his free hand,
you can see that the reflection on his palm is
not a complete rectangle - the upper right
quadrant is clipped off by the shadow of his
cap bill. In contrast, in the NASA training
video, the subject with the cap has his cap
reversed, with the bill over his neck, so that
the cap cannot shade the mirror.
> The one unusual one seems to be the StarFlash, which
> has some kind of lens element in there. It gives a
> bright fireball, but visibility through the device
> is really bad.
> What do people think about the aiming devices
> in their mirrors?
My favorite is the original 3M stainless steel mesh retroreflective aimer used in the old 3"x5" MIL-M-18371E glass mirrors - that's what is in my glove compartment, but 3M ceased production of that mesh in the 1970s. The "fireball" brightness was neither too dim nor too bright, and the apparent diameter of the "fireball" was just about exactly the 0.52 deg diameter of the sun.
The three issues I find with modern retroreflective aimers are:
(1) The brightness of the "fireball". Some are too bright in full sunlight (which I address by using sunglasses), and some are too dim in dim sunlight. This is a long recognized problem ( see this patent:
http://www.google.com/patents?id=ys1DAAAAEBAJ ). Of the modern mirrors, I find the Starflash too bright, Rescue Flash, Coghlan's and Vector I brighter than I favor, the one Rescue Reflector I have a bit brighter, the 3"x5" S.I. Howard mirror aimer is "just right" and the 2"x3" S.I. Howard mirror on the dim side.
(2) The diameter of the "fireball" is about 3x the sunbeam diameter (1.5 degrees) in every modern mirror I've checked, unlike the old 3M mesh with the 0.5 diameter. This is also a long-recognized issue: it is mentioned in the cited patent above, and the USCG standard for "reflex type" (retroreflective) aimers calls out a maximum allowable diameter of 2 degrees:
http://www.uscg.mil/hq/cg5/cg5214/survivalequip.asp#160.020 Basically this means that it does not suffice to get the "fireball" on target - you want the
center of the fireball on the target.
(3) Clarity of the window - scattered light can be a problem -
another reason to keep the mirror clean and protect plastic mirrors from scratches. The USCG requires that cleaning cloths be provided with lifeboat mirrors. Another thing to check with the Rescue Flash mirror - make sure you peel back the transparent protective membrane when you use it (and sometimes it is on the back, for some reason) - the viewing is muddy with the membrane in place. It would seem that the size of the clear hole in the mesh would play into this, but I haven't done a careful study to determine my position on that.
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