cavelamb wrote:
nothermark wrote:
On Fri, 02 Jan 2009 22:14:36 -0500, Pete Keillor
wrote:

On 2 Jan 2009 20:54:02 -0600, nothermark wrote:

On Fri, 02 Jan 2009 01:59:20 GMT, Dan@ (Pirateer guy) wrote:

On Thu, 01 Jan 2009 21:49:40 +0000, IanM
wrote:

My news wrote:
Any comment if Epoxy over Polyester will work?

No problem if the polyester is *well* cured. Months or years not
weeks.
Abrade surface thoroughly first.

Also make sure you de-wax the surface before sanding.
Ummm what wax?
Polyester uses a free radical cure with the reactive diluent styrene.
Oxygen activates the inhibitor, so a wax is incorporated into the
resin-styrene solution. The wax migrates to the surface during cure
to prevent oxygen exposure and allow complete cure. Otherwise, the
stuff won't cure on the surface. You need to remove this residual wax
as it'll prevent adhesion of the epoxy.

Pete Keillor

But won't sanding take care of that?


Depends on how aggressively you sand.

If you take the entire gel coat off, yeah, it's probably all gone.

If you are just scuffing the gel coat (not good) it's possible the wax just
gets smushed around and is still on the surface - and will contaminate
the bond.


God is in the details, as they say...
36 grit flap wheel aggressive enough? Or my other favourite, 24 grit
sanding disks on an anglegrinder :-)

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
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