fairing topside - degelcoat bottom
#1. Imco, prep for painting above the sheer has to go forward with 2-part epoxies.
Initial repair with epoxy gel, with or withoust chopped strand glass for structural filling.
There is no other technology that has the versatility of good epoxies for predictable results.
Cosmetic, ie filling small holes and shallow depressions, ought to be done with
laminating epoxy mixed with WestSystem's 407 low density powder filler.
That should be your final fairing and filling.....ready for primer, pin-hole filling, no other flaws.
Imco, follow that with a sandable epoxy primer. Any number of coats necessary...
to present the surface to whatever paint system you will use for final color....for show.
IMCO = 'in my considered opinion'.......
Using 100% solids, no solvents - no-blush - premium laminating - 2-to-1 epoxy will,
imco, protect the boat and also protect the coatings you are finishing the boat with.
100% solids epoxy so there is no out-gassing to screw up your color coats. If you
use SOLVENT epoxy primers & sandables make sure they cure well beyond what is specified.
Seriously look into SystemThree's water reducable 2-part epoxy sandable primers.....
WR-155 works over polyester and epoxy bases, and is compatable with all finish systems,
so far as I know. No outgassing to screw them up. No VOCs to kill you.
(Epoxy primers are the transitional chemistry between, in this case, polyester/ vinylester....
and any finshing emanel or LPU. Imco the best primers are water reducable.)
#2. I'm not sure that removing gelcoat is necessary for barrier coating the hull.
The hull is not known for blistering, as the laminations (and gelcoat) were made with
unadulterated polyester rsisns available in the 60's.
But since you are....once you are done....suggest covering the hull with a primo white epoxy
'structural' coating* (not epoxy enamel paint). Depending on how you roll or spray it on
....three or four coats. Usually unnecessary to prime the bottom if using industrial coating.
Before you apply those important epoxy coats, you can fill and fair with the same 407 material
used topside. Would not recommend any other off shelf powder (but only because I haven't
used them TMK - 407 is good stuff.......However I will not use West System's toxic laminating epoxy.)
Don't use Bondo or any polyester filler in the bottom prep.
Get the ingredients and experiment with your own epoxy formula for a sandable fairing compound.
Imco it's important that the whole bottom up to the waterline is redundantly epoxy sealed.....
certainly if the boat is going to spend the next 50 years in the water..
Assume that if you already have Awlgrip on the topsides the surface would have been prepped
with epoxy. The topsides most likely would not be stripped of gelcoat. They would have been
dewaxed & heavily sanded - fairing and filling done with epoxy and appropriate compounds.
Main reason for the multi-layered epoxy coating after gelcoat sanding or grinding is
to have a water proof barrier to protect the more water vulnerable original antique polyester....
second, to create an obvious layer of color that future bottom prep for bottom paint
will not go beyond. (extra coats so that you won't sand through to the polyester.)
If the waterline is where you want it, imco, choose the top or bottom of it and stop
there with your new bottom coating system. Probably the pro that did the prep
for the topsides Awlgrip went to the bottom of the painted waterline, but stopped his
spray at his masking tape at the top of the waterline stripe.
Waterline stripes are commonly painted with one-part non-urethane enamels to allow
them to be sanded and repainted regularly. Awlgrip cannot take constant immersion.
Matching, or touch-up re-painting, of existing Awlgrip color is out of the question.
Use the boot stripe to adjust mistakes. Top line of stripe doesn't have to be straight.
That's one way to see it!
Hope we're having fun!
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* This type of industrial coating will probably have solvents in its formula, or will have
to be thinned with aromatic solvents. For tutorials and products see www.epoxyproducts.com