[Rhodes22-list] Polyester casting resin over Epoxy

[Martinez, Juan]

I own a 1981 Rhodes 22.  I joined the list about a year ago. I find the
list very informative. I am repairing damage to the keel of my. I
speculate that freeze damage caused hour-glassing of the centerboard box
and longitudinal cracks following the seam line where the centerboard
box and the keel were originally bonded (bottom of the keel).  I cleaned
out all the ballast from the keel cavity down to the inner fiberglass
roving wall. The ballast was chunks of lead (about 100lbs), some resin /
sand mixture and the rest cement that had loosened up to the consistency
of packed wet sand. I am planning to repair the longitudinal cracks from
inside the keel cavity overlaying several layers of fiberglass and West
105/205 epoxy resin.  After the repair is complete, I need to fill the
keel cavity again with ballast. I am planning to use polyester casting
resin and lead shot.  I have read that polyester resin does not adhere
well to epoxy.  Is there anything I can do to improve the casting resin/
epoxy bond?  Are there any mechanical or chemical alternatives that may
promote good adhesion of the casting resin to the epoxy?  

 

Juan Martinez