Bubble canopy / solar heating -- addendum

I was reminded, in an off line conversation, that UV intensity increases
with altitude. Therefore, the skin cancer risk that I always regard as
exagerated at sea level is much more worthy of concern--and therefore of
prevention--at altitude. The higher you go the more important it gets, and
sailplanes spend a lot of time above 15,000 feet; but even my own plans to
fly a lot between 8,000 and 10,000 feet mean that this issue deserves a lot
more attention than I have been giving it.

Canopies by Ray Poguette of ThermoTecUSA.com were mentioned in the
conversation, giving excellent UV protection. A tinted version for reduced
heating is also offered. (Required disclaimer: I have no connection to
this company)

A quick web search also yeilded a little information on a GE product called
"Solar Control Lexan" which is stated to be both cold bendable and heat
formable and which they are recommending as a clear cover for excalator
tunnels--which might be exposed to sun, rain, and hail. The Lexan is
advertised as an IR (heat) blocker, and may also be an inherent UV
blocker--I do not know whether all, or only some, polycarbonates are UV
blockers--only that the polycarbonate used for eyeglass lenses is rated at
99% UV suppression. In addition, I found some references to scratch
resistant UV blocking coatings to be placed on the outside of windows and
scratch resistant IR coatings to be placed on the inside.

The bottom line is that canopies which are transparent to visible light, but
nearly opaque to both UV and IR are coming soon--and some may be here
already.

Peter

I wear eyeglasses when I fly that have "Transitions" lenses that
automatically darken when exposed to UV light. I don't know if they react
only to UV-A or UV-B, but they appear to be a convenient (although
uncalibrated) test instrument for how much UV the canopy admits. While
flying in bright sunlight in the mid-teens, my eyeglasses only get a little
dark; less than I would prefer. My conclusion is that my bubble canopy is
filtering out most of whichever UV rays the eyeglasses respond to. I wear
sunscreen and I'm not worrying about skin cancer related to flying.

Based on my experience with my eyeglasses in friends' airplanes and cars, it
seems that airplane canopies and car windshields filter out much of the UV
radiation. I don't know if that's inherent in the materials themselves or
if manufacturers add something to filter UV.

Dennis

"Dennis Johnson" wrote in message
. ..
I wear eyeglasses when I fly that have "Transitions" lenses that
automatically darken when exposed to UV light. I don't know if they react
only to UV-A or UV-B, but they appear to be a convenient (although
uncalibrated) test instrument for how much UV the canopy admits. While
flying in bright sunlight in the mid-teens, my eyeglasses only get a
little
dark; less than I would prefer. My conclusion is that my bubble canopy is
filtering out most of whichever UV rays the eyeglasses respond to. I wear
sunscreen and I'm not worrying about skin cancer related to flying.

Based on my experience with my eyeglasses in friends' airplanes and cars,
it
seems that airplane canopies and car windshields filter out much of the UV
radiation. I don't know if that's inherent in the materials themselves or
if manufacturers add something to filter UV.

Dennis



I don't know--or at least I know a lot less than I thought that I knew.

My current clear polycarbonate lenses seem to do a better job of filtering
out UV (or whatever made me squint a lot before) than the photo-grey-extra
lenses they replaced. However, the polycarbonate lenses that I have are
rated as 99% opaque to UV, and the photo-grey-extra lenses darkened with
visible light. I was not aware that another type of transition lens was
available--but it is an additional feature to watch for in window/canopy
material.

I had simply presumed that all polycarbonate was nearly opaque to UV, that
acrylic was not, and that neither had much affect on IR; but there now
appears to be a lot more to the story. I now suppose that you may be
guessing exactly right that something is added to filter UV--and it could
very well be throughout the material or as a coating. In addition,
polycarbonate was previously notorious for its poor abrasion resistance, and
its inability to be repolished; but the new formulations and/or coatings
have drastically improved the durability.

Typical window glass is nearly 90% opaque to UV; but glass that is nearly
transparent to UV is also available--and is/was very commonly used, at
venues such as home shows, to facilitate the demonstration of film coatings
for windows. Obviously, that was not its real purpose; but I don't know
what the real purpose might have been.

Acrylic is currently a big unknown--at least to me. I don't know how opaque
or transparent it might be to either IR or UV, or what range of formulations
might be available. What I did find, from a web search, was that both UV
and IR blocking coatings appear to be available--however, I tried to find
the reference again and I am not at all sure that it isn't really a
film--which might not be usefull for a canopy.

At this point, all that I really know with any certainty is that one canopy
manufacturer does offer a UV blocking canopy, and that most automobile
windows block nearly 90% of UV.

Peter

"Peter Dohm" wrote

I had simply presumed that all polycarbonate was nearly opaque to UV, that
acrylic was not, and that neither had much affect on IR; but there now
appears to be a lot more to the story. I now suppose that you may be
guessing exactly right that something is added to filter UV--and it could
very well be throughout the material or as a coating. In addition,
polycarbonate was previously notorious for its poor abrasion resistance,
and
its inability to be repolished; but the new formulations and/or coatings
have drastically improved the durability.

I have a pair of glasses that darken (don't remember what they are called)
that are safety glass rated, and have an anti scratch coating applied, also.
They filter UV and have proven to be more scratch resistant by a couple
levels of magnitude better than any others I have ever had.

Could it be that they finally figured out how to make a good scratch
resistant coating? I don't know the answer, but they are far better than
the other coatings I have gotten in the past. Nice, too, that they came
from Wally World, so the price was right.
--
Jim in NC

I had simply presumed that all polycarbonate was nearly opaque to UV,
that
acrylic was not, and that neither had much affect on IR; but there now
appears to be a lot more to the story. I now suppose that you may be
guessing exactly right that something is added to filter UV--and it
could
very well be throughout the material or as a coating. In addition,
polycarbonate was previously notorious for its poor abrasion resistance,
and
its inability to be repolished; but the new formulations and/or coatings
have drastically improved the durability.

I have a pair of glasses that darken (don't remember what they are called)
that are safety glass rated, and have an anti scratch coating applied,
also.
They filter UV and have proven to be more scratch resistant by a couple
levels of magnitude better than any others I have ever had.

Could it be that they finally figured out how to make a good scratch
resistant coating? I don't know the answer, but they are far better than
the other coatings I have gotten in the past. Nice, too, that they came
from Wally World, so the price was right.
--
Jim in NC


I don't know, but it's very possible.

Although mine don't change color, the scratch resistant coating has been
remarkably effective. There are no discernable scratches after a couple of
years--despite treating them as though they were glass.

I hope that something as sturdy turns out to be available for canopies and
windows.

Peter

In article ,
"Peter Dohm" wrote:


I had simply presumed that all polycarbonate was nearly opaque to UV,
that
acrylic was not, and that neither had much affect on IR; but there now
appears to be a lot more to the story. I now suppose that you may be
guessing exactly right that something is added to filter UV--and it
could
very well be throughout the material or as a coating. In addition,
polycarbonate was previously notorious for its poor abrasion resistance,
and
its inability to be repolished; but the new formulations and/or coatings
have drastically improved the durability.

I have a pair of glasses that darken (don't remember what they are called)
that are safety glass rated, and have an anti scratch coating applied,
also.
They filter UV and have proven to be more scratch resistant by a couple
levels of magnitude better than any others I have ever had.

Could it be that they finally figured out how to make a good scratch
resistant coating? I don't know the answer, but they are far better than
the other coatings I have gotten in the past. Nice, too, that they came
from Wally World, so the price was right.
--
Jim in NC


I don't know, but it's very possible.

Although mine don't change color, the scratch resistant coating has been
remarkably effective. There are no discernable scratches after a couple of
years--despite treating them as though they were glass.

I hope that something as sturdy turns out to be available for canopies and
windows.

Peter

Plexiglass II UVA has been around for decades! It filters out UV A, but
I don't know about UV B. It is the stuff from which aircraft canopies,
windows, windshields, etc. have been made for at least the past 45 years.

"Orval Fairbairn" wrote in message
news
In article ,
"Peter Dohm" wrote:


I had simply presumed that all polycarbonate was nearly opaque to
UV,
that
acrylic was not, and that neither had much affect on IR; but there
now
appears to be a lot more to the story. I now suppose that you may
be
guessing exactly right that something is added to filter UV--and it
could
very well be throughout the material or as a coating. In addition,
polycarbonate was previously notorious for its poor abrasion
resistance,
and
its inability to be repolished; but the new formulations and/or
coatings
have drastically improved the durability.

I have a pair of glasses that darken (don't remember what they are
called)
that are safety glass rated, and have an anti scratch coating applied,
also.
They filter UV and have proven to be more scratch resistant by a
couple
levels of magnitude better than any others I have ever had.

Could it be that they finally figured out how to make a good scratch
resistant coating? I don't know the answer, but they are far better
than
the other coatings I have gotten in the past. Nice, too, that they
came
from Wally World, so the price was right.
--
Jim in NC


I don't know, but it's very possible.

Although mine don't change color, the scratch resistant coating has been
remarkably effective. There are no discernable scratches after a couple
of
years--despite treating them as though they were glass.

I hope that something as sturdy turns out to be available for canopies
and
windows.

Peter

Plexiglass II UVA has been around for decades! It filters out UV A, but
I don't know about UV B. It is the stuff from which aircraft canopies,
windows, windshields, etc. have been made for at least the past 45 years.

The only reference I could find was 280 to 400 nonometers, on the
RPlastics.com web page. According to the ThermoTecUSA.com web page, that
looks like the bottom third of UVB and all of UVA.

But, all of that brings up an ... umm ... interesting ... umm ...question
....
(Considering that I wasn't the only one on the NG who didn't know this)
Do you suppose ... presuming that your timeline is correct ... that OEMs for
both civil and military aicraft have been using the "right stuff" ... and
that Homebuilders may have been using whatever happened to be lying around
at the local plastic distributor?

Peter

In article ,
"Peter Dohm" wrote:

"Orval Fairbairn" wrote in message
news
In article ,
"Peter Dohm" wrote:


I had simply presumed that all polycarbonate was nearly opaque to
UV,
that
acrylic was not, and that neither had much affect on IR; but there
now
appears to be a lot more to the story. I now suppose that you may
be
guessing exactly right that something is added to filter UV--and it
could
very well be throughout the material or as a coating. In addition,
polycarbonate was previously notorious for its poor abrasion
resistance,
and
its inability to be repolished; but the new formulations and/or
coatings
have drastically improved the durability.

I have a pair of glasses that darken (don't remember what they are
called)
that are safety glass rated, and have an anti scratch coating applied,
also.
They filter UV and have proven to be more scratch resistant by a
couple
levels of magnitude better than any others I have ever had.

Could it be that they finally figured out how to make a good scratch
resistant coating? I don't know the answer, but they are far better
than
the other coatings I have gotten in the past. Nice, too, that they
came
from Wally World, so the price was right.
--
Jim in NC


I don't know, but it's very possible.

Although mine don't change color, the scratch resistant coating has been
remarkably effective. There are no discernable scratches after a couple
of
years--despite treating them as though they were glass.

I hope that something as sturdy turns out to be available for canopies
and
windows.

Peter

Plexiglass II UVA has been around for decades! It filters out UV A, but
I don't know about UV B. It is the stuff from which aircraft canopies,
windows, windshields, etc. have been made for at least the past 45 years.

The only reference I could find was 280 to 400 nonometers, on the
RPlastics.com web page. According to the ThermoTecUSA.com web page, that
looks like the bottom third of UVB and all of UVA.

But, all of that brings up an ... umm ... interesting ... umm ...question
...
(Considering that I wasn't the only one on the NG who didn't know this)
Do you suppose ... presuming that your timeline is correct ... that OEMs for
both civil and military aicraft have been using the "right stuff" ... and
that Homebuilders may have been using whatever happened to be lying around
at the local plastic distributor?

Peter

YUP!

Plexiglass II UVA has been around for decades! It filters out UV A,
but
I don't know about UV B. It is the stuff from which aircraft canopies,
windows, windshields, etc. have been made for at least the past 45
years.

The only reference I could find was 280 to 400 nonometers, on the
RPlastics.com web page. According to the ThermoTecUSA.com web page,
that
looks like the bottom third of UVB and all of UVA.

But, all of that brings up an ... umm ... interesting ... umm
....question
...
(Considering that I wasn't the only one on the NG who didn't know this)
Do you suppose ... presuming that your timeline is correct ... that OEMs
for
both civil and military aicraft have been using the "right stuff" ...
and
that Homebuilders may have been using whatever happened to be lying
around
at the local plastic distributor?

Peter

YUP!

It certainly looks like you are correct.

I found a little more information, although some of the Plexiglas
nomenclature is slightly different, on another vendor page at
http://www.plexiglas.com/literature/pdf/81.pdf and that one includes
graphical presentation of the solar sprectral distribution as well as
transmittance of several types of Plexiglas.

At the moment, I have not found much on the IR side for Plexiglas, aside
from the assertion that coatings exist--and of course the obvious that
tinting does reduce overall heating.

And, of course, there is also the Solar Control Lexan--which has both the
fault and feature that it is not intended to be frangible. That is a
feature in the event of bird strikes and also regarded as a fault in some
excape situations where a canopy can not be readily opened. BTW, some of
the Plexiglas formulations are also asserted to be either non frangible or
less frangible.

Clearly, more research is indicated and some volunteers are needed.

Peter

("Orval Fairbairn" wrote)

"YUP!"

(5)
(4)
(3)
(2)
(1)

We have a winner. g


Paul-Mont
I know, I know - hypocrite me!
....quoting his entire reply like I did. :-)