Date: Mon, 10 Dec 2012 22:21:56 -0600
Reply-To: Mike South <msouth@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike South <msouth@GMAIL.COM>
Subject: Re: Is it open-cell foam if it doesn't say closed-cell? (heater
flap material)
In-Reply-To: <50c658d3.8520340a.5ec6.5606@mx.google.com>
Content-Type: text/plain; charset=ISO-8859-1
Thanks everyone.
Synthesizing these comments with what I read in the archive, I think the
softer stuff is preferable because you don't want too much friction or they
will be hard to close. One message in particular speculated that for the
ones that blow down, they are activated by differential force of air flow
or something like that, and possibly won't even be able to function with
something on there that's too stiff.
Another consideration is that the stuff that they put in there originally
looks like it was pretty soft stuff back before it became fossilized (by
that I mean its skeleton appears to be that of something that was of the
"open and spongy" variety; I think the technical term is softosaurid rather
than stiffosaurid).
Here's the bit from the archives I was referring to above (from David
Beierl on May 5 2012:)
While you're in there, don't forget to check the pivots on the
> free-swinging flaps that slam shut when the blower air is stronger
> than the ram air. They tend to wear triangular and then jam or fall
> out. If either happens, your blower will have a merry time blowing
> air around in a circle to itself, though the ram air will still be
> fine. A challenging item to repair because of access issues and the
> need for it to swing freely. I didn't last time, but I believe
> opening up access from the side (and covering it with aluminum body
> tape afterwards) would be the way to get in there without going
> insane. I don't regard renewing the foam on those flaps as
> important, and likely to do more harm than good because of the small
clearances and low forces involved.
Here is that in the archives, there is some other good stuff in the thread:
http://gerry.vanagon.com/cgi-bin/wa.exe?A2=ind1205A&L=vanagon&P=R17516
Thanks again everyone, your input is very much appreciated.
mike
On Mon, Dec 10, 2012 at 3:48 PM, David Beierl <dbeierl@attglobal.net> wrote:
> At 01:19 PM 12/10/2012, Mike South wrote:
>
>> Is the difference just that one is porous like a natural sponge and one is
>> formed of a bunch of closed bubbles stuck together? I saw a lot of
>> recommendations that you use "open-cell foam", so I guess I'm wondering if
>> that's the "default foam" :).
>>
>
> Open- and closed-cell foams are as you say. If not specified you don't
> really know which it is. All else equal the closed-cell foam will be
> harder to compress because you can't squeeze the air out of it, but foam
> density, material etc. also influence how soft a foam is. It's been too
> long since I've been in a heater box (it's hanging over my head, though)
> and I've forgotten what I learned while inside them, but in general you
> don't have much force to operate the flaps, so you have to have a light
> soft foam to be able to compress the hinge side enough so the far edge
> seals.
>
> Yrs,
> d
>
