RE: Hard, Fast or Slow? Fast, usually

From: Tracy Pierce (TPierce@goldengate.org-DeleteThis.com)
Date: Wed May 09 2001 - 11:33:45 PDT

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Message-ID: <87372ECCA42DD3118E3200508B2E11464B177B@ggexsf.engineering.goldengate.org-DeleteThis.com>
From: Tracy Pierce <TPierce@goldengate.org-DeleteThis.com>
To: "'wind_talk@opus.labs.agilent.com-DeleteThis.com'" <wind_talk@opus.labs.agilent.com-DeleteThis.com>
Subject: RE: Hard, Fast or Slow?  Fast, usually
Date: Wed, 9 May 2001 11:33:45 -0700 

this will probably require a little cut & paste...
http://www.westmarine.com/webapp/commerce/command/ProductDisplay?prmenbr=201
&prrfnbr=2637&store_num=4&store_name=Maintenance&subdept_num=196&subdept_nam
e=Resins%20Epoxy%20%26%20Fiberglass&class_num=197&class_name=Epoxy%20Resin

or just go to
Google: West Marine
Boat Maintenance
Resins Epoxy & Fiberglass
Epoxy Resin

where you'll find the manufacturer's recommendations (which I always follow
as very closely as I possibly can, after getting er strange results
elsewise).

Coyote Windcam? Great idea. Repeat it often, in the presence of SFBA board
members!

> -----Original Message-----
> From: J.R. Seven [mailto:seven@mechsys2.me.berkeley.edu-DeleteThis.com]
> Sent: Wednesday, May 09, 2001 11:01 AM
> To: Multiple recipients of list WIND_TALK
> Subject: Re: Hard, Fast or Slow? Fast, usually
>
>
>
> Ed Scott wrote:
> >
> > For anyone using the West System, a query:
> >
> > On cool California evenings during the summer, do you get
> better results
> > with the fast hardener or the slow stuff. Seems like the
> slow stuff is only
> > good for daytime use in direct sunlight. The stuff doesn't
> kick sufficient
> > for ding repairs at night (55-70 degrees) for 25-30
> minutes. If I apply it
> > to dings before then it runs all over the place, and that's
> when metering a
> > tad more than the pump puts out.
> >
> > Btw, any downside to using a little bit more hardener? I
> understand it
> > might make the finished product brittle. Also, when
> changing hardeners, any
> > concern about or procedures for cleaning the pump?
> >
> > So, for best results to get hard do you like it fast or slow? :-)
>
> I've been using the fast stuff for repairs with good success,
> at night and in
> the daytime in a shady area. Occasionally I have to mix a
> second batch because
> I couldn't finish the job before the first jelled up. The
> most significant
> problem has occurred when I mixed some up with microspheres
> (for use as a dent
> filler and rail shape adjuster) and left it in the mixing pot
> a little too long.
> The filler acted as an insulator, and the stuff was putting
> out smoke in a few
> minutes as it melted the bottom out of the plastic pot.
>
> I think the slow stuff is mostly used for larger jobs which
> take more time,
> such as laying up full-sized laminates rather than small repairs.
>
> As for ding repairs where some strength is needed, you want
> some glass in there,
> not just plastic. So it's best to use the stuff when it's
> thin (to wet the
> glass) and keep it in the right place with a mold made from
> tape or something.
> Where you don't need strength, mixing in some filler such as
> the aforementioned
> microspheres keeps the stuff manageable.
>
> Everything I've read says that varying the ratio of hardener
> to epoxy is a bad
> idea. This works for polyester because polyester hardener
> catalyzes a reaction
> in the polyester resin itself, and more catalyst makes the
> resin change more
> quickly. But with epoxy, the final hardened plastic consists
> of chemicals from
> both the resin and hardener; if some of either one is
> missing, you'll get a
> percentage of unhardened stuff in the resulting plastic, thus
> weakening the
> final product. (Any chemists like to give a more precise
> description? I know
> this one isn't exactly rigorous.) When I've messed up the
> ratio, I got something
> which had the stiffness of rubber but cracked easily as well.
>
> I wonder if people who live in the Delta (or farther East)
> need the slow stuff?
>
>
> JR
>

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