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?
Thx,
Pete
A239
-tank not yet installed, and contemplating the design and construction of an
all-composite tank (...the Cozy and LongEze builders have geen doing it for
years...no?).
On Wed, Dec 23, 2009 at 7:06 AM, Jan de Jong <jan_de_jong@casema.nl> wrote:
>
> Checking with John and Roger at the factory re tank installation.
>
> 1.
> The last of the original (2004) Ltd crew is retiring and having its last
> day at the office today. The end of a period - again.
> Roger will be available by e-mail for a while for technical questions. He
> monitors this forum. If I say a lie he will correct I'm sure.
>
> 2.
> The gaseous tank treatment introduced to prevent swelling causes epoxy to
> bond to the tank material.
> Thermal expansion rate difference is the most likely cause for tearing
> tanks.
> Prescription:
> Install in accordance with the manual but with a permanent release film
> between layup and tank.
> No other measures are necessary and triboelectrics are not an issue.
>
> (
> Googling gives a linear thermal expansion coefficient difference between
> glass reinforced epoxy and polyethylene in the order of 1 in 10000 per
> degree C.
> That would be 1 mm per 20 cm for 50 degree C.
> )
>
> Cheers,
> Jan de Jong
>
>
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