Painting aluminum glider trailer

I have a 20+ year old trailer for my G102. Presently, its bare sheet
aluminum. I want to paint it white to reduce the amount of heat
absorbed by the trailer skin. A local autobody shop quoted me $1600.00
to cover with a polyurethene paint over an epoxy primer. This is far
more than I wanted to spend. Any suggestions on durable paints or
products that can be applied by a novice to sheet aluminum. I can rent
an airless sprayer if need be. Thanks.

John Murphy wrote:
I have a 20+ year old trailer for my G102. Presently, its bare sheet
aluminum. I want to paint it white to reduce the amount of heat
absorbed by the trailer skin. A local autobody shop quoted me $1600.00
to cover with a polyurethene paint over an epoxy primer. This is far
more than I wanted to spend. Any suggestions on durable paints or
products that can be applied by a novice to sheet aluminum. I can rent
an airless sprayer if need be. Thanks.

Most of the commercial cost is in the preparation and finish. If you can get
them to agree to just spray it the price will be substantially less. This
implies you clean and prepare for painting, and they do no flatting and polishing.

As long as the surface is well prepared you can paint it with a roller, and get
reasonable looking results...
--
Bruce Greeff
Std Cirrus #57
I'm no-T at the address above.

John Murphy wrote:
I have a 20+ year old trailer for my G102. Presently, its bare sheet
aluminum. I want to paint it white to reduce the amount of heat
absorbed by the trailer skin.

Clear reflective metal absorbs less heat than any paint, even white.

Stefan

Bruce wrote:

As long as the surface is well prepared you can paint it with a roller,
and get reasonable looking results...

Applying durable paint to aluminium is somewhat tricky. Cleaning the
aluminium is not enough, you need to "prime" it correctly. Of course you
can do that yourself, but you must know what you are doing.

Stefan

Exactly correct! The best thing to do is buff it to a mirror shine as
that will reduce the thermal absorption. Do this inside as well as
outside if you want maximum results. Doing the inside will reduce the
amount of radiated heat that goes from the inside surface directly to
the glider. Just like Techshield plywood roof decking.


Stefan wrote:
John Murphy wrote:

I have a 20+ year old trailer for my G102. Presently, its bare sheet
aluminum. I want to paint it white to reduce the amount of heat
absorbed by the trailer skin.


Clear reflective metal absorbs less heat than any paint, even white.

Stefan

Clear reflective metal absorbs less heat than any paint, even white.

A club member painted his bare aluminum tube type trailer white and
noted that the decrease in heat buildup was very noticeable. Apparently,
YMMV.

Tony V "6N"

I agree that the most highly polished Alu
has nothing against a pure white paint when it comes the reflectivity and
absorption rates of sun light. I just do not know where this myth comes
from.
Udo

Clear reflective metal absorbs less heat than any paint, even white.

A club member painted his bare aluminum tube type trailer white and noted
that the decrease in heat buildup was very noticeable. Apparently, YMMV.

Tony V "6N"

"Udo Rumpf" wrote in message
.. .
I agree that the most highly polished Alu
has nothing against a pure white paint when it comes the reflectivity and
absorption rates of sun light. I just do not know where this myth comes
from.
Udo

Clear reflective metal absorbs less heat than any paint, even white.

A club member painted his bare aluminum tube type trailer white and noted
that the decrease in heat buildup was very noticeable. Apparently, YMMV.

Tony V "6N"


I have to agree with Udo.

Anyone who has lived in the desert knows that polished aluminum will get hot
enough to inflict burns if left out in the sun. Painted white surfaces
won't.

The best evidence I know of for this is the telescopes at the National Solar
Observatory at Sunspot, NM. They are painted "Telescope White" to prevent
solar heating from distorting the supporting structure. If polished
aluminum worked better, that's what they would use.

The only rational reason for polishing a trailer instead of painting it
weight. Polishing is lighter than paint and that may save a little fuel.

Painting aluminum is a tiny bit involved but not difficult. Prepping the
surface with an etching wash and then using a good primer is the key -
consult with your paint supplier. Using a roller to paint a trailer is
perfectly reasonable.

Bill Daniels

Polished metals reflect sunlight very well - up to 90% for a highly =
polished aluminium surface. This property is easily compromised by any =
change within a depth of a few atoms near the surface. Oxidation is such =
a change and takes place quicky on most metal surfaces (except for a few =
'noble' metals whose chemical reactivity is very low). In aluminium, =
this oxidation does not look like rust and may be invisible to a casual =
observer, but causes an immediate loss of reflectivity, down to 40% or =
less. Surface contamination, dust and dirt will reduce it even further.

White paint has a reflectivity of about 20 to 30% in the visible light =
spectrum when well maintained, and is generally preferable as protection =
against solar gain.

There is a reason why a metal surface in the sun "burns the skin" while =
a painted one may not. It isn't because the metal surface is warmer - in =
fact it may be at the very same temperature. Metals, however, are =
excellent heat conductors, and will transfer heat very quickly to other =
bodies with which they come into contact. Paint, fiberglass, wood are =
essentially organic materials held together by covalent bonds and for =
this reason conduct heat less easily.

On the inside of a trailer, the property that matters most regarding =
heat transfer is the surface emissivity. Metals have a lower surface =
emissivity than other materials, even when lightly oxidised. For this =
reason, the innards of a metal trailer may well remain with their =
natural finish, except if the local climate is conducive to water =
condensation in the winter. In the later case, an internal lining with a =
vapour barrier will hinder condensation inside the trailer. Even just =
plain painting will reduce the severity of internal condensation.

Lining the inside of the trailer with any metalised, reflective foam, =
preferably leaving a small gap between this and the trailer walls, will =
do marvels in lowering internal temperatures. This is very cheap =
material and may be considered by anyone keeping a glider in a sunny =
place with large daily temperature swings. A ventilator helps too, =
mostly in avoiding condensation.

A mistake in my previous posting: white paint has a solar reflectivity =
of 70 to 80%. It is the opposite property of solar absorptivity, from a =
table of which I was quoting, that is 20-30%. I hope the argument makes =
more sense now.