Taking the long view, the only way to protect the keel is to start
with bare metal. Several choices of treatment from that point, but I
don't think "Extend" should play a part.
On my first attempt at saving Ursa's keel -- a year or two into our
relationship -- I did the Extend thing. I subsequently commented that
the [next and] 'final' solution "starts with bare metal -- not really
that bad unless you've already applied something tough but not tough
enough. Briefly: two coats of two-part epoxy bare metal primer, two
coats of two-part epoxy primer, one coat of some kind of two-part
epoxy topcoat, and four coats of ablative bottom paint."
Well, Extend was that "something tough," with emphasis on the"not
tough enough." In combination with paint, it lacked physical strength
and usually lifted slowly when penetrated.
I finally ground the stuff off at great expense in mess and time and
grinding disks. (Resistance to being completely removed *was* it's
tough part.) Never again!
I don't really recommend "Extend" for the keel, even though I've
cheerfully used several drums of it on my 22 yr old van.
Regards,
Bill Combs
WWP 19 #439 (Aug 1987)
"Ursa Minor"
Fort Walton Beach FL
ttursine@gnt.net