[Dominic]

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I finally got two DIY projects kicked-off this weekend.

By good research and planning I got hold of the components necessary to build an interface between my dive computer and my nice new Palm PDA.

By pure luck, I got hold of the stuff necessary to test some ideas about reflective materials...

So I'd just like to ask a few questions about the stuff.

1) Who's got reflective patches on their kit? Drysuit, BCD, SMB, wherever..

2) What do you think about them? Great idea, not worth bothering about, prefer not to have them, or what?

3) If it were possible to get your cylinders coated with the stuff, would you do it or not? Why?

In case of any doubts, I'm not talking about a mirror-finish or anything: It's the grey tape stuff you get on those bright yellow jackets that policemen and construction workers all seem to wear these days, that just shine at you from the darkness when you're driving.

I have them on the cuffs of my Otter drysuit, Buddy jackets have them on the pockets IIRC, some SMBs have them stuck around the top... they appear in a fair number of places. So what are people's thoughts about them?

 

[Dominic]

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I know you're out there. I can hear you breathing.

 

[Lou]

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Hi Dom

Got them on the Otters, as you say, and on the shoulders of my Seamann Sub BC.  I would get it put on the hood for surface viz, but the stuff is so bright in torchlight that I wouldn't want it all over the tank.  Maybe a stripe for buddy finding from the rear, but not so much as it is annoyingly dazzling (like the folks with strobes on in 10m viz at Stoney - what's all that about?).

HTH

Lou

 

[John Gulliver]

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I have it on my hood, ordered it after reading Diver's tests. I would also have it put on the inside of my forearms if I bought a new drysuit (again after reading Diver's test). Like Lou, I'm dubious about having it put on the whole surface of my cylinders but can see good reasons for putting a strip on each cylinder. I'm all for anything that will improve my chances of getting picked up alive and well after a dive.

 

[John Gulliver]

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I have it on my hood, ordered it after reading Diver's tests. I would also have it put on the inside of my forearms if I bought a new drysuit (again after reading Diver's test). Like Lou, I'm dubious about having it put on the whole surface of my cylinders but can see good reasons for putting a strip on each cylinder. I'm all for anything that will improve my chances of getting picked up alive and well after a dive.

 

[Dr Stevil]

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I think it's a good idea, I've got a yellow reflective Sam Brown (bought if for my bike test never worn it since), thought I might adapt it for my hood (glue and stitch) and put a stripe or two on my dSMB (glue only)
Chee-az
Steve

 

[Dominic]

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Why is dazzle perceived as such a worry?

After all, this is the same material used in roadsigns to make them visible at night - if twin car headlights at full beam in the middle of the night don't dazzle you, why are torches going to? Has everyone bought a 50w HID while I wasn't looking?

Just as a point of interest, by the way, you might like to look at some of the results of my prototype experiments - basically I've just used different types of media to get the reflection going.

This is them with no light being reflected back (Indirect lighting)
Link

This is them with the camera flash being reflected back:
Link

As expected, the best results are from the most bloody awkward method. The most interesting part (for me) is the white disk: If you study both pix, you'll notice that the reflective portions are actually darker than the non-reflective portions when the light isn't being reflected.

The square bit, btw, is a bit of proper reflective tape bought from a shop, just as a comparison.

 

[Dr Stevil]

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</span>

Quote[/b] ]Quote: from Dominic on 8:39 pm on Jan. 13, 2003
Why is dazzle perceived as such a worry?

<span =''>

Dazzled in British waters? Chance would be a fine thing!
Personally I like to be (and like my buddies to be) as visible as possible, there nothing worse (well, there is actually) than the last glimmer of light as your buddy disappears into the murk. I was thinking that I could use some of that stuff to make removable bands that could be clipped onto cylinders as desired
Chee-az
steve

 

[Lou]

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The problem with it is that the larger the area (and therefore the amount of light reflected back at you) compared to the area of your torch beam, the less detail you make out other than the reflection.

A small patch is as easy to see when it catches the beam as a large patch, but doesn't wipe out all your "peripheral" vision.

Just my perceptions of the situation

 

[Dominic]

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</span>

Quote[/b] ]I was thinking that I could use some of that stuff to make removable bands that could be clipped onto cylinders as desired

<span =''>

My current aim is to get some magnetic sheeting that I can cover in a reflective coating, and put on my cylinders as and when I want to - I'm currently tempted by the idea of blue and red diagonal stripes

Lou - I can see where you're coming from. But bear in mind, reflective material only reflects when you shine your light onto it - it doesn't reflect light from other sources. That's the way it works - all light is reflected back towards its source.

I don't often get into a postion where I shine my torch at my buddy; he's usually next to me while torch beams are out in front.

The time when I WOULD be aiming to get my buddy in a torch beam would be when I'd lost sight of him and was shining my torch all around looking for him. At that point, the bigger the reflective surface, the better my chances of seeing him, is my basic line of thinking.

PS I fully agree with your comment about those numpties at Stoney with those poxy strobes that are visible from half  a mile away

 

[Lou]

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aaah, see, now the situation you are thinking of is slightly different to me.  Times when I have been more than aware of reflective coatings are following buddy into dark place, hence getting an eyeful of reflection from my torch (and thanks Dom, I do know what reflection is, even mechanical engineers take their physics that far ).  

Just have to be careful you don't wipe your lovely magnetic strip off on some wreck.....

 

[Dominic]

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Ahh.. I THOUGHT we must be considering different scenarios.

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Quote[/b] ]and thanks Dom, I do know what reflection is

<span =''>
Ahh, but DO you? I only mentioned the way the panels reflect light in case you were thinking that reflected sunlight, for instance, might be a dazzle problem. - evidently, this wasn't your worry tho.

But technically we're not talking about true reflection: Reflective panels use a specific sub-type known as retroreflection.

Reflected light only goes back the way it came if it hit at 90 degrees to the surface - otherwise it goes in an equal and opposite direction. The reflective panels we're on about actually use retroreflection, which always goes back the way it came.

Score one for the biochemist

(Edited by Dominic at 4:38 pm on Jan. 14, 2003)

 

[Lou]

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But isn't that due to "micropanels" (like faceted strcutures) within the larger panel which *do* use true reflection?

 

[Dominic]

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Interestingly, no.

That's how the solid plastic ones you get on bikes and cars etc work, and apparently it's also the best method, reflecting the highest quantity of light back at the source.

But it only works on rigid structures - so for the panels we get on drysuits and SMBs, it's not possible to use.

Instead, tiny high-refractive-index glass spheres are embedded in a reflective media. If you examine a roadsign or reflective tape or even a car numberplate, you'll just about be able to see that it has a grainy-looking surface due to the tiny, measured-in-microns beads.

And the way it works is:
Light enters glass bead, is refracted to a different angle.
Light hits reflected surface bead is embedded in at 90 degrees
Light is reflected back the way it came
Light is refracted again as it passes back out of the bead

So it's actually a combination of reflection and refraction that makes the whole thing work. Refraction makes sure that no matter where the light comes from, it hits the surface at 90 degrees, and reflection then sends it right back the way it came. This is the opposite of normal reflection, which will send light in the opposite direction to which it came.

Pretty cunning, huh?

(And yes, I DO have a life :tongue2: )

 

[Lou]

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Ah, very interesting.  I had noticed the beads but assumed that they were faceted and reflected, rather than spherical and refracted.  Dead clever indeed!

Are you quite sure you have a life, though!

 

[Dominic]

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Quote[/b] ]Are you quite sure you have a life, though

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Yes.

A person with no life would have discovered this in his spare time.

I found it out when I was at work

 

[Lou]

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Touche!  

Point to Mr Humphries.

 

[Dr Stevil]

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got meself sorted with reflective strips for my tanks now. Used the old reflective Sam Brown I mentioned, and two straps which were removed from a Bowstone add-on dive pocket. The reflective material was already fixed to webbing, just threaded the strap thru inbetween the two and added a couple of stitches to hold it securely in place.
Will get a decent test-run if we're doing the Ellerton night dive trip  this week
Chee-az
Steve

 

[Mdemon]

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Funnily enough, I've been playing with reflective strips for a while now.  Initially I put some luminous mine tape round the valve and end of my cylinder.  Works great if everything goes pitch black, but otherwise pretty useless.  Got some reflective material of a traffic cone that had taken on a lorry and lost.  The material is not very robust, but using transparent outdoor tape, enough is visible on cylinder to respond to a flash of a buddy's torch...

I haven't tried the hood thing, but I probably will.  I have seen similar used by soldiers on helmets/hats to make them visible to helicopters, and don't see why it wouldn't work for divers.  I suggest some material is on the front of the body too - no good waving yours arms at someone if they can't see them!  Perhaps a piece along the edge of a slate might do it - failing that, on the shoulder straps should do.