Though I recall seriously questioning the bonding called for in the
manual, I blithely went ahead and laid up the glass on the tank...much
to my chagrin. Because of the isolated reports of swelling, I did
install a padded FG "shield", intended to enhance the apparent
function of EURO 25 spacers shown on pg. 16-5, Fig. 7.
At this point, I intend to place a release film between underside of
tank and the inside surface of the bottom of the fuselage and squirt
some non-expanding foam through the twin access ports to fill the gap
between tank and fuselage. I'll use a long straw on the foam can in
order to raise the possibility of ending up with a full bed of
foam...the intention being to provide uniform support for the fuel
tank and to minimize any stresses on the tank caused by it being
cantilevered from the FG "straps" previously bonded to the tank. This
is a procedure described in Ron Pagoris's build-log. To my knowledge,
this is a theoretical band-aide with no operational experience which
might speak to its effectiveness.
...my 2 cents...comments & wisdom welcome,
Fred
A194
On Dec 23, 2009, at 6:46 AM, Bob Borger wrote:
> Pete,
>
> My thoughts as well. And I have a factory assembled CM with bonded
> tank.
>
> And because I had the same understanding as you, I keep the tank
> full and won't empty it for an extended time if at all possible.
>
> Where do we go from here?
>
> *** Merry Christmas and Happy New Year to all ***
>
> Bob Borger
>
> On Wednesday, December 23, 2009, at 08:13AM, "Peter Zutrauen"
> <peterz@zutrasoft.com
> > wrote:
> >
> This is the first I have heard of thermal expansion being attributed
> as a contributor to cracking.
>
> It was my understanding that even the flourinated tanks swell, and
> it was the swelling + adhesion of the epoxy (restricting the
> swelling locally, creating point-stresses) which was the cause of
> some cracking. - Or have I mis-understood the previous reports and
> email threads?
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