The UV Index and why your canopy is your friend
Eric Greenwell
Among other things, it measures the UV flux and computes the UV Index
(UVI), then determines a "safe exposure time" based on your input of
skin type and the SPF of the sunscreen you are using.
Naturally, I made a measurement in the sun (UVI = 8), then another one
inside the cockpit (UVI = 0), indicating the canopy provides quite a bit
of protection. Testing other kinds of plastic, like baggies, plastic
wrap, Lexan, etc., gave readings from 0 to 7, so not every kind of
plastic is protective.
These measurements made me curious about what the UVI index is, so I did
some searching and learned a few things:
* The UVA band (315 nm to 400 nm) is the primary tanning and
wrinkling band
* The UVB band (280 nm to 315 nm) is the primary skin damage band
* The UVC band is almost entirely blocked by the atmosphere, so has
essentially no effect
* The UVI is a weighted value that accounts for the skin's response
to different irradiation frequencies (almost none to UVA, quite a
bit to UVB)
The most interesting discovery for me is that tanning can occur without
harmful skin damage (I know, we hate wrinkles, but they don't kill!), so
getting a tan, such as the tan described by a letter writer to a recent
Soaring magazine, does not mean you are also damaging your skin.
Looking at an "erythemal dose rate" chart, you can see almost all (>99%)
of the dosage in the direct sun occurs below about 330 nm. Since our
canopies block UV below about 360-370 nm, they provide essentially
complete protection from damaging rays. The fraction of the UVA that
comes through will still give you some tanning, and some fabrics will
fade slowly, but your skin is protected from the UVB. This is very good
news, that the canopy affords even more protection than I first thought.
So, cover yourself as much as possible (hat, long sleeves, etc), put the
sunscreen on when you get to the gliderport, do your rigging and outside
preparation early in the morning, and take shelter under a wing, under
an umbrella, or inside a building or vehicle (glass protects, too) while
waiting to take your tow. Breathe easy while you are flying the glider,
and apply more sunscreen when you land, unless the sun is low.
This is the main reference I used for my education and conclusions:
* http://www.aero.jussieu.fr/~sparc/News21/21_Long.html
Other interesting references are:
* A simpler version of the main reference (National Weather Service):
http://tinyurl.com/evfc7
* UV meter:
http://tinyurl.com/f3uuy
--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly
"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html
"A Guide to Self-launching Sailplane Operation" at www.motorglider.org
Greg Arnold
Maybe you could do this test on some of older canopies at your
gliderport?
Eric Greenwell wrote:
> I recently bought an Oregon Scientific UV888 Personal UV Monitor (~$30).
> Among other things, it measures the UV flux and computes the UV Index
> (UVI), then determines a "safe exposure time" based on your input of
> skin type and the SPF of the sunscreen you are using.
>
> Naturally, I made a measurement in the sun (UVI = 8), then another one
> inside the cockpit (UVI = 0), indicating the canopy provides quite a bit
> of protection. Testing other kinds of plastic, like baggies, plastic
> wrap, Lexan, etc., gave readings from 0 to 7, so not every kind of
> plastic is protective.
>
>
fado...@yahoo.com
variety of gliders at our gliderport. So, I wouldn't suggest resting
easy until you've tested your own canopy.
Eric Greenwell
> Greg Arnold wrote:
>> Do older canopies also protect against UV, or is it only the newer ones?
I haven't tested a variety of canopies, but based on the data sheets
from acrylic manufacturers, and comments by canopy and sailplane
manufacturers, I'd expect even older canopies (mine is 12 years old) to
offer plenty of protection. Acrylic that transmits UVB is more expensive
than the ordinary kind, so there would be little reason to use it.
>> Maybe you could do this test on some of older canopies at your
>> gliderport?
> Some older ones do, some don't. That's what we found by testing a
> variety of gliders at our gliderport.
Do you recall which gliders didn't offer as much protection, and how you
tested the canopies?
> So, I wouldn't suggest resting
> easy until you've tested your own canopy.
And at $30 or less for a UV Index meter, it'd be a cheap purchase for a
club to make. You only need to check each canopy once! And, if anyone
finds canopies that _don't_ pass the test, please tell us about it.
defi...@msn.com
ago, probably the same one you have. As best as I recall, it was
reading 12 (extreme) outside. When put under a newish DG800, older
DG200, and very old Kestrel, it read 0. Put under a 20 y.o. LS-6 it
read 3 or 4, indicating only around 75% was being absorbed (still
better than nothing).
Stefan
> Naturally, I made a measurement in the sun (UVI = 8), then another one
> inside the cockpit (UVI = 0), indicating the canopy provides quite a bit
> of protection. Testing other kinds of plastic, like baggies, plastic
> wrap, Lexan, etc., gave readings from 0 to 7, so not every kind of
> plastic is protective.
This is the reason why you needn't care too much about your sunglasses:
In the old days of glass glasses, it was the coating which protected
your eyes. There were good and bad coatings. Nowadays, it's the plastic
itself which protects. Get some cheapo poly-whatever, and your eyes are
protected, even with total clear glasses. Colour filter and sex appeal
may be a different story.
Stefan
Eric Greenwell
Very interesting. It's going to be a while before I'm near a collection
of gliders, so I hope others will buy or borrow a meter and check the
gliders in their club, and report the results.
Do you know if the LS-6 had the original factory canopy or a replacement?
jnbe...@aol.com
material?
Chip Bearden
ASW 24 "JB"
John Galloway
While I agree that a good quality clear canopy (eg
mecaplex) gives a gratifying amount of UV protection
I think that your sources under-estimate the risks
of UVA and the implications of a tan.
As regards tanning, to quote the current opinion of
the British Association of dermatlogists:
'There is no such thing as a safe or healthy tan. A
tan is a sign that already damaged skin is trying to
protect itself from further damage. The protecting
power of a tan is weaker than that of a mild sunscreen
of SPF 2-4.' See:
http://www.bad.org.uk/public/cancer/
UVA doesn't burn the skin as quickly as UVB but it
is much more deeply penetrating and the trend of medical
opinion in recent years has been towards an increasing
appreciation its cancer causing potential. UVA penetrates
cloud cover and light clothing.
I don't know whether UVA tanning beds are used a lot
in the US but in the UK they are very popular and manufacturers
and tanning studios propogate a great deal of misinformation
about 'bad' UVB , 'harmless' UVA and 'safe' tanning.
The message I take from your very helpful finding that
quite a bit of the longer wavelengths of UVA gets through
canopies is the opposite from your conclusion. To
me it emphasises importance of using UVA protective
sunscreens and clothing when flying.
John Galloway
Guy Byars
He talks about wrinkling and skin damage (sunburn?). Well, if you are only
concerned about sunburn and wrinkling, then go ahead and depend on the
canopy for your protection.
However, nowhere in Eric's post does he mention SKIN CANCER!
The UVA range of the sun's spectrum has a longer wavelength and penetrates
right through your canopy and deeply into your skin. There is a large body
of research which ties UVA exposure to skin cancer.
http://healthlink.mcw.edu/article/964647970.html
The canopy does provide some protection, but it is not sufficient. The best
protection is to cover yourself with light colored clothing and a good
protective hat while flying. Certainly a broad spectrum sunscreen should be
used as well.
Guy Byars
"Eric Greenwell" <flyg...@verizon.netto> wrote in message
news:x_hTg.79$Oh3.3@trnddc04...
Guy Byars
> some searching and learned a few things:
>
> * The UVA band (315 nm to 400 nm) is the primary tanning and
> wrinkling band
It is also the primary basal and squamous cell skin cancer band.
The UV coming through you canopy can kill you. Protect yourself from it
properly.
Eric Greenwell
> Are most glider canopies made of approximately the same thickness
> material?
All the ones I've looked seem to be about 0.60". Typical acrylic's
cutoff is steep and deep (<<1% transmission below the cutoff), so even
twice the thickness makes little difference. The acrylics designed to
pass UV (at least from the Cyro company) have a more gradual "tail".
Eric Greenwell
> I must strongly disagree with Eric's post!!!
>
> He talks about wrinkling and skin damage (sunburn?). Well, if you are only
> concerned about sunburn and wrinkling, then go ahead and depend on the
> canopy for your protection.
>
> However, nowhere in Eric's post does he mention SKIN CANCER!
>
> The UVA range of the sun's spectrum has a longer wavelength and penetrates
> right through your canopy and deeply into your skin. There is a large body
> of research which ties UVA exposure to skin cancer.
>
> http://healthlink.mcw.edu/article/964647970.html
>
> The canopy does provide some protection, but it is not sufficient. The best
> protection is to cover yourself with light colored clothing and a good
> protective hat while flying. Certainly a broad spectrum sunscreen should be
> used as well.
I certainly agree with these cautions, and they are needed even more
outside the cockpit, where glider pilots also spend a lot of time.
I read the article, but now I'm confused that the UV Index doesn't seem
to account for UVA, and the article didn't mention it. Can you describe
the reason or point to a resource that does? Perhaps the UV index hasn't
kept up with the science?
ASM
Hi there,
Eric makes an excellent point...there are some questions that we need
to ask....and he is not the first one to raise up the point. Great job
Eric....
Jacek
Washington State
defi...@msn.com
Derek Copeland
health warning then?
Del C
At 18:36 30 September 2006, Guy Byars wrote:
>I must strongly disagree with Eric's post!!!
>
>He talks about wrinkling and skin damage (sunburn?).
> Well, if you are only
>concerned about sunburn and wrinkling, then go ahead
>and depend on the
>canopy for your protection.
>
>However, nowhere in Eric's post does he mention SKIN
>CANCER!
>
>The UVA range of the sun's spectrum has a longer wavelength
>and penetrates
>right through your canopy and deeply into your skin.
> There is a large body
>of research which ties UVA exposure to skin cancer.
>
>http://healthlink.mcw.edu/article/964647970.html
>
>The canopy does provide some protection, but it is
>not sufficient. The best
>protection is to cover yourself with light colored
>clothing and a good
>protective hat while flying. Certainly a broad spectrum
>sunscreen should be
>used as well.
>
>Guy Byars
>
>
>
>'Eric Greenwell' wrote in message
>news:x_hTg.79$Oh3.3@trnddc04...
Guy Byars
> So should open cockpit vintage gliders come with a
> health warning then?
No, the gliders with canopies should have the following warning:
WARNING: Do not depend on this canopy for protection against the sun. Even
though you might not receive a sunburn through this canopy, you will still
be exposed to the sun's UVA wavelengths. The UVA wavelengths are a proven
carcinogen. While using this canopy you should still protect yourself with
opaque clothing and broad spectrum sunscreens.
Lew Hartswick
> So should open cockpit vintage gliders come with a
> health warning then?
>
> Del C
>
"Use of this product may be injurious o your health"
Or maybe.
"The state of California has determined it may cause cancer"
:-)
...lew...
Eric Greenwell
Guy, I seem to recall an article from a long time ago where you wrote
about adding tinted film to the canopy. Are you aware of what it takes
to have a canopy that blocks, say, at least 95% of the UVA? I've been
unable to find charts showing the transmission figures for tinted
acrylic. I suppose there might be coatings that could be applied by
either the material, canopy, or sailplane manufacturer, but I don't know
if these are available, practical, or even useful.
I use two plastic sheets on the inside of the canopy during the winter
to prevent fogging/frosting of almost the entire canopy during wave
flying . If these were made of a UVA blocker plastic or had the
appropriate coating, they could be left on all year. Even better would
be a anti-UVA coating with anti-scratch properties than could be applied
to a finished canopy.
The pilot would still need to protect himself while outside the glider,
but a completely protective canopy would eliminate many hours of
exposure. Sunscreen could be wiped off the face just before getting into
the glider, preventing the eye irritation/blinding problem.
309
happy here:
"To avoid injury to eyes, soar with eyes closed."
This has been shown effective in reducing the fear factor, too.
FWIW, I plan to keep using my Ray Ban G-15 lenses, heavy as they are,
and the "Water Babies" (easier on the eyes) SPF 30, 40 or 50 (when I
can find it), the ubiquitous soaring cap (which some folks feel are
more effective than BCG's worn by us engineers), and of course, lip
balm.
Those that know me will attest to the fact that I come in two colors:
1.) pale and 2.) extra-crispy.
Thanks, Eric...until now I hadn't thought to try and quantify wether
the canopy acted as a filter or a magnifying glass...of course, the
sports canopy on my 1-26 adds another factor: windburn!
Cheers,
-Pete
#309
Bob Kuykendall
> All the ones I've looked seem to be about 0.60"...
Now wait a minute, Eric, I think you might have slipped a decimal
point.
A thickness of 0.60" is about 5/8" or about 15mm. I have seen aircraft
transparencies that thick, but only on transport and jet fighter
windshields. In polycarbonate, thicknesses like that might be
considered "Bullet Resistant" (I don't like the term "bulletproof").
The canopies for the early HPs are usually made from 1/16" thick
material; that's about 0.063" or just over 1.5mm. That's pretty typical
for small transparencies such as you'd find in older sailplanes with
two-piece canopies. It makes for a transparency that is perfectly
adequate for most sailplane flight loads, but with less than inspiring
stiffness; especially for limber plastics like polycarbonate. For a
while I had a 1/16" Lexan forward canopy on my HP-11, and I remember
once when I was pressing back to Truckee through hail that the whole
forward canopy shimmered like a soap bubble with each hailstone strike
- and they were not much bigger than peas.
More typical sailplane canopies, such as the HP-24 transparencies I've
been ordering, are made from 1/8" material; that's 0.125" or just over
3mm. Most of the broken European sailplane canopies I've seen seem to
be about 3mm thick.
Here's the thing, though: The minimum thickness of a canopy is often
substantially less than that of the original sheet of material. Since
most canopies are either free-blown or stretch-formed from flat
material, the finished canopy has more surface area than the original
pre-formed material. That extra area doesn't come from nowhere; it
comes from stretching the acrylic while it is hot and rubbery. Since
(for our purposes at least) acrylic is incomressible, it has to get
thinner where it is stretched, and gets thinnest where it is stretched
the most.
It's hard to say how much thinning is typical, but I have seen pieces
of a broken canopy made from 1/8" material where the minimum thickness
at the crown was about 0.090".
Thanks, and best regards to all
Eric Greenwell
> Earlier, Eric Greenwell wrote:
>
>> All the ones I've looked seem to be about 0.60"...
>
> Now wait a minute, Eric, I think you might have slipped a decimal
> point.
It's the "beanie" option offered by all the manufacturers to pilots that
like to fly with the hats that have the little button in the center. It
hurts like heck when turbulence throws you against the canopy, but it
doesn't crack the plastic!
> More typical sailplane canopies, such as the HP-24 transparencies I've
> been ordering, are made from 1/8" material; that's 0.125" or just over
> 3mm. Most of the broken European sailplane canopies I've seen seem to
> be about 3mm thick.
All this time I've been flying gliders, and I've never measured one
until tonight. So, here it is: 0.096"! Lots thicker than I thought.
That's at the vent window opening on my ASH 26 E, the only convenient
point to put a caliper (I hope I never get the chance to measure it
elsewhere).
Lorry
Guy, I am afraid I have to disagree with the notion that sailplane
canopys lack protection from UV. I would like to quote from an artical
written by Friedel Weber (DG Owner) which appeared on the DG websight:
"We also asked Mecaplex about the transmission of UV light through the
canopy. The canopies do not totaly screen out UV but do absorb about
95% of it." Further, during one of my visits to the Aero in
Friedrichshafen several years ago I discussed this at the Mecaplex
stand. We were having some language difficulties at the time so they
offered to send me their catalogue describing their offerings. They
offer different materials. As I recollect, those that I looked at were
polycarbonates all of which absorbed 95% or greater.
What we realy need to be concerned about is all the standing around on
the ground without adequate protection.
Lorry
Surfer!
<char...@aol.com> writes
<snip>
>
>What we realy need to be concerned about is all the standing around on
>the ground without adequate protection.
In fact by the time I've protected myself for all the standing around
helping on the launch line, I've protected myself for flying. One thing
that has caught me is how dehydrated I can get hanging around the
airfield - it has been very hot (for Scotland) this year, but maybe anno
domini is catching up with me as well...
--
Surfer!
Email to: ramwater at uk2 dot net
HL Falbaum
"Lorry" <char...@aol.com> wrote in message
news:1159940294....@m7g2000cwm.googlegroups.com...
>
> What we realy need to be concerned about is all the standing around on
> the ground without adequate protection.
>
> Lorry
>
I have heard several Dermatologists say that the first 30 min of exposure
produces the most severe damage. After that, the outer, dead, layer of the
skin becomes more opaque to UV. A good argument for sunscreen before going
out in the sun.
Hartley Falbaum
"KF" USA
Surfer!
<hfal...@comcast.net> writes
A lot of sunscreens need applying 30 minutes or so before going in the
sun.
soar2...@yahoo.com
Guy Byars wrote:
> I must strongly disagree with Eric's post!!!
>
> He talks about wrinkling and skin damage (sunburn?). Well, if you are only
> concerned about sunburn and wrinkling, then go ahead and depend on the
> canopy for your protection.
>
> However, nowhere in Eric's post does he mention SKIN CANCER!
>
> The UVA range of the sun's spectrum has a longer wavelength and penetrates
> right through your canopy and deeply into your skin. There is a large body
> of research which ties UVA exposure to skin cancer.
Your obsession with UV exposure thru canopies makes me laugh. You are
likely getting far more exposure standing out on the ramp waiting for a
tow. How many of you realize how poorly many fabrics protect you
against UV? Not many, based on this collective list of responses. I
remember a story an old physics instructor told me about a checker
board pattern sun burn from wearing plaid shirt while hiking thru the
Italian alps during WWII. Your light colored cotton shirt has only a
SPF of about 10 (or less):
The good news is that there is a laundry product called Sun Guard that
can improve this to around 30:
http://www.sunguardsunprotection.com/
Also, Plexiglas blocks over half of the UVA spectrum, and this is the
shorter wavelength, higher energy half.
Tom Seim
2G
Richland, WA
Guy Byars
in no way complete or sufficient protection against the part of the UV
spectrum that causes skin cancer. Several years ago, I put numerous
Mecaplex canopy samples in a precise spectrophotometer and generated
spectral curves for them. All the curves showed good UVB protection, but
inadequate UVA protection. (Note the spectrophotometer I used for my
research was a very precise research instrument at the University of
Cincinnati.... not a $30 toy)
Although your references claim to have products which block 95% of UV light,
that is not at all a precise measurement of the problem. Perhaps they block
95% of the UVB, but what do they do for the UVA? What % do they block at in
the 280nm-320nm range (UVB)? What % do they block in the 320nm-380nm
range(UVA)?
Again, I reiterate. Canopies will filter out UVB light which will provide
protection against sunburn. Canopies do a very poor job of filtering out
UVA light which causes skin cancer.
Guy Byars
"Lorry" <char...@aol.com> wrote in message
news:1159940294....@m7g2000cwm.googlegroups.com...
> Guy, I am afraid I have to disagree with the notion that sailplane