Subject: CPES Cure Times & Capability
Date: Wed, 29 May 2002
We write to you from San Diego, Ca. We are doing some repair work on
a wooden Lightning (approximately 45 yrs. old) and have a couple of
questions. Our project involves 1) replacing the deck with new 3/8
marine mahogany plywood, which we intend to CPES and varnish, and 2)
repairs to the hull (we added a few splines) and some minor rib work
(a couple show some rot), as to which we intend to treat all exposed
wood where repairs have been made or new wood added with CPES and
follow with paint. Here are the questions:
1) I can't recall what you recommended when I ordered the CPES a few weeks
ago about when we should consider painting/varnishing after application
of the CPES in order to achieve the best bond. In other words, how much
cure time should we allow before painting and/or varnishing? Our daytime
temp this week has been in the mid- to high-70's.
CPES will cure to a "tack free" state in about 1-3 hours at your
temperatures and San Diego humidity. At this point you are free to apply
the first coat of paint or varnish (un-diluted, full strength), and the
epoxy will "lock in" the surface coating. You have a little spread here,
and in the real world if you can get the first finish coat on within
about 8 hours you will achieve the superior bond. If for some reason it
goes longer and the epoxy cures, you will still get excellent
bonding...it's just a matter of degree.
2) We previously used the West System to glue in splines in doing hull
repair work. Any concerns about incompatibility of CPES and the West
Nope, go ahead and use the West. It will bond with the CPES-treated surface.
I still have some of the West System materials and was
inclined to use up what I had in a couple of patches (mostly filling
some gaps) after applying CPES to the surrounding wood. Any concerns?
None at all.
Any different cure time (from your answer to question one above) for
the CPES if I am following it with either the Lay-up and Laminating
resin or West System?
Nope, all application procedures remain the same.
All you are really waiting for with the CPES is for it to evaporate away
the carrier solvents, and the CPES "tack free" phase indicates that has
happened. The reason is that you don't want the CPES carrier solvents
diluting any subsequent epoxy or other finish that is applied on top.
3) I am trying to estimate whether I have enough CPES on hand
currently. My project has expanded since I ordered originally, but I
over-ordered some to begin with. I ordered two, two-quart kits so I
have a gallon in total. Based on the scope of my repair, I plan to
CPES the deck (both sides = approximately 80 sq. feet x 2, or 160 sq.
feet in total), the outer sides of the hull (bow to stern) and
approximately 25% of the interior of the hull (including ribs). Do
you think I have enough? Also, is the coverage rate of CPES
approximately 200 sq. ft per quart or per 2-quart kit.
The coverage rate of CPES for good wood is approximately 200-250 sq ft
per gallon. In your application you will lose a little due to plywood
cut-edge absorption, and some on the interior as it works its way into
seams and joints. My quick mental math tells me that your gallon of CPES
will not be quite enough.
Thanks for you help.
You're welcome, and come on back if you have further questions.