Hi,

Congrats with your decision to build a Hariette to start with, she
will be a lovely boat ...
To answer your question on the pump ...
To begin with there are two kinds of units of pressure expressed in
microns, microns of water and microns of Hg (mercury), we suspect
these microns are microns of Hg, by the way it is not 0.75 microns but
75 micron, which is a deep vacuum if you consider that athmospheric
pressure is 760-770 mm of Hg (mercury) ...
But what kind of resin would you use in your infuson ...
Polyester, vinylester have high styreen (solvent) content and thud
easli "boil" at such high vacuum ... if you would like to have a
maximum compression on your laminate you should use epoxy resin. Epoxy
has no solvent content and thus can easily be used under such high
vacuum ... besides epoxy is superior in mechanical, chemical and
adhesion characteristics ...
If you have more questions ... feel free to ask them ...

Best regards,

Youri

youri@wangkaboats.eu

--- In harryproa@yahoogroups.com.au, "gardnerpomper" <gardner@...> wrote:
>
> Hi,
>
> I have lots of questions on how to build a boat, and since it will be
> a harryproa (harrietta to start), and everyone has been so helpful
> here, I thougth I would just start a thread.
>
> Rob has posted in another thread about how to start learning vacuum
> infusion, and I am gathering the materials for that. I didn't realize
> that getting a vacuum pump would be so complicated. I don't really
> know how to read specs. What is 0.75 microns of vacuum?
>
> Anyway, I have been looking at ebay motors, at item 190226298481,
> which seems an inexpensive pump. Would someone mind offering an
> opinion, or an alternative? I don't know how to judge. This is just
> for testing and harrietta, not for a "full size" harry.
>
> Thanks,
> - Gardner
>