[C320-list] How Often to Repaint Hull

[Jack Brennan]

Hi Troy:

Don’t underestimate the quality of Catalina’s work with the vinylester.

My boat, no. 528, has been continuously in the warm waters of the Gulf of Mexico for the last 20 years, except for maybe two months in boat yards. It has never had a single blister, even though these are prime conditions for the pox.

I’d say Catalina did a good job of laying up the 320 hulls to ward off blisters. With operations in Florida and its vast experience in boat building, it follows that they would know how to do the job right.

I don’t think an epoxy barrier coat is needed on the 320s with vinylester, based on my experience. Sand blasters use epoxy to repair the damage they cause. If soda blasting is as good as you say, it  should not require a barrier coat.

Jack Brennan
Sonas, 1998 Catalina 320, no. 528
Tierra Verde, Fl.
Dolphin Cruising Club of Tampa Bay







Sent from Mail for Windows 10

From: Troy Dunn
Sent: Wednesday, August 21, 2019 7:19 PM
To: C320-List at catalina320.com
Subject: Re: [C320-list] How Often to Repaint Hull

Hmmm...

I believe that Catalina switched from polyester resins to vinyl ester
resins for laying up the 320 during the early years of production.   So
perhaps not all hulls are vinyl ester.   Not sure.   Early hull owners may
know.   Hull #514 is a vinylester layup.

Before layup Catalina sprayed gelcoat into the mold.   So the hull is
gelcoat, then vinylester resin FRP.

Vinylester has improved osmotic blistering performance, but it is not
blister proof.

Vinylester has no where near the performance that true epoxies have for
forming a water barrier.   A single barrier coat of Interprotect 2000E will
improve the resistance of the hull to water intrusion.   However, it must
be stated that this is not the intended use of the product when going for a
true barrier coat.   Many more layers are typically applied to a polyester
resin FRP hull.   Interprotect is a fantastic primer however if properly
applied and the proper ablative is applied while the 2000E is still curing.
  Most folks who have used this approach will tell you they have fantastic
results.   I have heard folks have had just as good of luck with cheaper
ablatives than micron CSC in the same approach.   If you need to cut costs
this is the place to cut I suspect.

Soda blasting is not sand blasting.  I would not recommend using any of the
services of a boatyard that wants to sand blast your hull...unless your
hull is made of ferrous materials.  Soda blasting uses baking soda, just
like some dentists do for polishing teeth now.   Some soda blasters are now
using walnut shells which is apparently even milder than soda blasting.  I
think a lot of antique restorers use the walnut shell process with
partially rusted or delicate antiques.

If anyone is in need of a reputable soda blaster in the Chesapeake area PM
me and I will send you details for the folks our marina uses...I think they
service all the marinas between Deale and Havre de Grace probably.  The
folks we used left the hull in great condition ready to prep, and did not
mar up any of the gel coat.  Getting the hull that nice with a sander in
any reasonable amount of time without buggering up the gelcoat somewhere is
not a skill this casual sander possesses.

FWIW-

Troy