RE: [T3] POR 15 Question, IMPORTANT

["Bryan \"bc\" Castles" <bc@version3.net>]

<x-charset iso-8859-1>Keep in mind that the tar boards are pretty old and there is much better
technology to perform the same function available today.  The purpose of the
tar boards is to add mass to the panels thereby lowering the resonance of
the panel.  Lower resonance often results in lower perceived noise. The tar
boards are just the age old solution to that. Yes, many of them also claim
to actually convert vibration to thermal energy, thereby further increasing
their effectiveness...  but read up.  That is usually a secondary function
of the board, and not as effective as using other methods. You can add much
more effective mass in the same sized package by using some high temp mastic
once you have pulled the tar boards out, scraped, wire brushed and POR'd.
HTM would be like Dynamat and stuff.  I personally don't use the name brand
stuff because of the markup.  I have VERY good results with the stuff from
McMaster-Carr ( www.mcmaster.com ).  It is an adhesive backed HTM similar to
the all of the asphalt based mat the that car audio folks fork over many
pennies for. The nice thing about this newer stuff is that it is so much
thinner, that you can occupy the same space with 2-3 layers of the new
stuff, adding much more mass to the panel, and doing a much more effective
job of decreasing perceived noise.

Example:  I stripped the carpet from my square which is my daily driver, and
took out the tar boards, and cleaned and wire brushed the passenger side.  I
then went through my POR-15 procedures.  After that cured, I did the POR-15
black.  Followed by Rubberized undercoating.  I followed that up with
sprayable truckbed liner, and finally added the tar boards.  An important
note to the way I did this:  make sure every stage CURES before you attempt
to apply the next one, or you may not get proper adhesion.  While this is
not a big deal on the HTM on the floor, it makes a BIG difference you when
you do the inside of the doors.  The result (this is how I am driving it
currently) is a much more effective decrease in sound than factory, and I
haven't even put carpet back in it yet.  The next stage when I finish the
other side, will be some carpet jute, followed by a nice high quality loop
pile carpet.

The reason I used this undercoating in the interior is pretty simple:
secondary sound deadening.  The undercoating helps add strength to the panel
reducing flex and vibration, and it also (in the case of the rubberized
coating) absorbs much of the vibration energy and coverts it to thermal
energy. By combining these two types of sound deadening practices you get a
MUCH more effective than stock cabin sound... or lack of it.

Sorry about the book...  I guess I just suddenly had a lot to say on the
subject this morning.  :-)


Bryan Castles
Arlington, TX
USA

'64 Sunroof Beetle
'70 Bus (Ex-Westy)
'73 Square
www.version3.net <http://www.version3.net>



-----Original Message-----
From: James Altemus [mailto:jaltemus@snet.net]
Sent: Thursday, April 25, 2002 10:13 PM
To: Type 3 Mailing List
Subject: Re: [T3] POR 15 Question, IMPORTANT


I used the silver POR-15 on the floorboards of this Golf race car I'm
putting together.  As long as you get any scaly rust off you'll be fine.
You can also get the POR-15 off...with a grinder.  We had to remove some to
weld the rollcage in, and my chassis builder was none too happy...

I definitely plan on POR-15ing the inside of the pan on my Fastback.  BTW,
is it possible to remove the tar boards in one piece?  Or should I be
looking for something to use in its place?

Jimbo


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