<VV> Car Covers and Dew

Tue Mar 10 17:56:44 EDT 2009

You are correct; moisture also comes up from the ground and under the
cover -- as you've proven by observation.  Unfortunately, once trapped
under the plastic, it just sits there doing its nasty corrosion thing.
That's why you NEVER cover your car with a non-porous cover no matter
how dry your storage.

The second, and related problem, is with concrete.  Moisture will come
out of the concrete as it cures (which can take a long time), and it
will come up from the ground through the concrete -- unless you've
installed a vapor barrier under the concrete.  Another problem with
concrete is that in the spring it will still be cold and on a warm
spring day, water will condense on it.  Which is why I have a fan on a
timer that blows across the concrete floor for several hours per day.

As for dirt floors, they're not all bad.  For several years I stored my
cars in an old indoor horse arena (where they road the horses).  It had
a very high ceiling and a very loose, very dry dirt floor.  Any water
that hit the floor almost instantly disappeared -- like it was a desert
(which it essentially was).

Dave Keillor

-----Original Message-----
From: virtualvairs-bounces at corvair.org
[mailto:virtualvairs-bounces at corvair.org] On Behalf Of Alan and Clare
Wesson
Sent: Tuesday, March 10, 2009 4:22 PM
To: RoboMan91324 at aol.com; virtualvairs at corvair.org
Subject: Re: <VV> Car Covers and Dew

Hi Doc

Lots of good sense here and I agree with most of it.

However, the bit that I would question slightly is that the moisture
only 
comes through the cover - yes, most covers are porous, and are designed
to 
let moisture both ways, but I have several scrap cars here which are
covered 
with completely waterproof tarps (on some of the I use builders'
damp-proof 
membrane), and they still get moisture under the cover, whatever the
surface 
they are on (usually tarmac or gravel, here). That's why I only keep
scrap 
cars outside.

Apart from that, as I said, not much to disagree with. Bt it underlines
what 
will be the first paragraph of Book 2 of the Got Rust? saga, that I am 
currently writing.

That is going to say that the most important thing you can do, bar none,
as 
soon as you get a classic car, is secure good, dry storage for it. And
if 
you have to pay a rental for the storage, the money you pay will be
saved 
many times over by the repairs you won't have to do to the car and the 
depreciation it doesn't cause.

Cheers

Alan

----- Original Message ----- 
From: <RoboMan91324 at aol.com>
To: <virtualvairs at corvair.org>; <alan.wesson at atlas.co.uk>
Sent: Tuesday, March 10, 2009 8:58 PM
Subject: <VV> Car Covers and Dew

> Alan,
>
> While there is moisture in the ground that can rise up, it is more 
> difficult
> for that moisture to rise through concrete which is what most of us
park 
> on.
> If you park on dirt, that would be the worst situation in regard to
ground
> moisture.  During a rain, water will soak into the concrete and
slowing 
> evaporate
> out which could condense on the underside of your car if it is cool.
A
> sealed or painted concrete surface is best unless there is a
depression 
> where you
> park and a puddle forms.
>
> Dew generally comes from the air.  Hot air holds more moisture.  (This
is 
> why
> politicians are all wet.)  As the air cools during the night, it
reaches 
> what
> is called the "dew point" and water vapor will condense on any
surface. 
> This
> generally happens on the cooler surfaces first and most.  Since most
car
> covers are porous to let moisture out, they will also let moisture in.

> During the
> night, the moisture will soak through to the car's surfaces which are
> typically cool.  It probably seems to you that the moisture originates

> between the
> car and the cover because the moisture on the surface of the car cover
> evaporates first in the morning sun and the moisture below the surface

> evaporates last.
> Of course, the cover will lengthen the time it takes for any inside 
> moisture
> to evaporate.
>
> The worst case would be covering your car with a cover that reaches
the
> ground.  Any moisture from the ground, rain flowing under the car or
dew, 
> will be
> trapped there longer because the cover prevents air circulation and
thus 
> slows
> evaporation.
>
> Doc
> 1960 Vette; 1961 Rampside; 1962 Rampside; 1964 Spyder coupe; 1965 
> Greenbrier;
> 1966 Corsa Turbo Coupe; 1967 Nova SS; 1968 Camaro ragtop
> ~~~~~~~~~~~~~~~~~~~~~~~~
> In a message dated 3/10/2009 12:21:20 PM Pacific Daylight Time,
> virtualvairs-request at corvair.org writes:
>
>> Message: 2
>> Date: Tue, 10 Mar 2009 18:29:11 -0000
>> From: "Alan and Clare Wesson" <alan.wesson at atlas.co.uk>
>> Subject: Re: <VV> Car Covers
>> To: "Ron" <ronh at owt.com>, "mike hicks" <mhicks130 at cox.net>,
>>     <virtualvairs at corvair.org>
>> Message-ID: <C303FCFA02A6435EBC9AB5E5B23528E9 at ALAN>
>> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>>     reply-type=response
>>
>> I am prepared to take your word for it, but personal experience
indicates
>> otherwise! I have had several very unfortunate experiences with
>> micro-blistering, on cars that were left outside in *dry* but dewy
>> conditions, and because extremely micro-blistered where the cover was
in
>> contact with the paint. When I removed the cover the contact surface 
>> where
>> the cover touched the paint was wet, as were various places under the
car
>> where the moisture could only (apparently) have risen.
>>
>> And I have just done a quick web search on the subject, and the best
>> explanation seems to be that dew is formed from moisture that
condenses 
>> from
>>
>> air close to the ground, as the ground has harboured heat in the
daytime, 
>> so
>>
>> when night falls the vapour nearer the ground condenses more.
>>
>> That in itself strikes me as a good reason to avoid car covers,
because 
>> the
>> dew is going to be condensing under your car where it is near the
ground,
>> and wetting it (this is certainly what happens). So whatever the
cause of
>> the dew (and I'm prepared to believe what you say about dew, and I
stand
>> corrected) I still wouldn't touch a car cover with a ten foot pole, 
>> except a
>>
>> dust cover on a car kept in a very dry atmosphere.
>>
>> Cheers
>>
>> Alan
>
>
> **************
> Need a job? Find employment help in your area.
>>
(http://yellowpages.aol.com/search?query=employment_agencies&amp;ncid=em
lcntusyelp00000005)
> _______________________________________________
> This message was sent by the VirtualVairs mailing list, all copyrights
are 
> the property
> of the writer, please attribute properly. For help, 
> mailto:vv-help at corvair.org
> This list sponsored by the Corvair Society of America, 
> http://www.corvair.org/
> Post messages to: VirtualVairs at corvair.org
> Change your options: 
> http://www.vv.corvair.org/mailman/options/virtualvairs
> _______________________________________________ 

 _______________________________________________
This message was sent by the VirtualVairs mailing list, all copyrights
are the property
of the writer, please attribute properly. For help,
mailto:vv-help at corvair.org
This list sponsored by the Corvair Society of America,
http://www.corvair.org/
Post messages to: VirtualVairs at corvair.org
Change your options:
http://www.vv.corvair.org/mailman/options/virtualvairs 
 _______________________________________________