Fred,
Probably the best answer is, "it depends". Any of your pre-molded parts that
have
the green/tan factory gelcoat also has some amount of mold release that has
to be sanded off so it is safe to say you should sand the whole plane surface
and apply your primer. It might be a little picky but the gelcoat provides
not structural benefit but does add weight. It goes without saying, you can
sand
the gelcoat but not any of the thin layer of glass layup. What ever filler
you used first, maybe Superfil, is the rough fill, likely with many pin holes.
SmoothPrime is the finer fill. Any raw sanded fiberglass/resin area will
have even more pin holes. SmoothPrime, one of its key purposes, is to eliminate
the pin holes. Make sure the surface to be finish painted is clean. Sanding
of the SmoothPrime leaves a clean paint-able surface but likely some parts
have been around some time since sanding and handled a good amount and therefor
could have contamination that needs to be removed. Sanding removes the
contamination
very well. I found that if you rub/clean off the sanded SmoothPrime
with acetone or lacquer thinner just before painting, there is some residue that
soaks into the SmoothPrime and affects how the paint goes on and leaves the
pattern showing the wipe marks through the paint. You also want to make sure
you have eliminated the sub-gelcoat bubble voids that are inevitably in the
fiberglass layups which will likely give way later and ruin your paint job.
Anyway,
depending on how "perfect" you want your final paint job, how many time
you reapply SmoothPrime and re-sand, you could use three gallons and probably
more in getting it just right. A caution for you because you are in a coastal
climate. Smooth prime will retain moisture so make sure it is completely dry
before you finish paint, you don't want any moisture under the paint. Some
moisture in the SmoothPrime does not matter when adding additional coats of
SmoothPrime.
You might have heard in the distant past, someone had a real bad result
and !
had to r
emove a bad paint job because it did not stick. What is nice about SmoothPrime
is it goes on so easily, cleans up with water. Rolling on is so easy...but
leaves
a rougher finish to then sand off. I used a small fine foam roller and
wrapped it with cellophane after use until the next use. If wrapped well and
I then could use the roller again even a week or more later. Spraying is more
of a pain but gives a smoother finish requiring less sanding but more equipment
cleanup. Don't sand in your shop or the great amount of sand dust will be
all over everything. I found that 320 grit sand paper was a bit too rough and
shows through if you use an expert painter, i.e., who applies just thick enough
of paint coats to cover. Myself being well less than an expert painter applied
considerably more paint, so I had to do considerable wet sanding of the finish
paint... but that had the effect of erasing the 320 grit sand paper scratches
that showed through. SmoothPrime, though being water based, adheres very
well and sands very well, while drying to a harder surface than the Europa kit
filler (epoxy based fillers) and even slightly harder than SuperFil. Hope
this helps, sanding and filling is a big project.
Bill
-----Original Message-----
>From: Fred Klein <fklein@orcasonline.com>
>Sent: Feb 20, 2012 6:54 PM
>To: europa-list@matronics.com
>Subject: Europa-List: Smooth Prime
>
>
>To those of you who have used Smooth Prime on their Europa XS...
>
>Have you used it JUST on the filled/foam control surfaces?...or on the
>ENTIRE airframe?
>
>In either case, how much material is necessary for the required THREE
>(undiluted) COATS before sanding?
>
>Thanks in advance,
>
>Fred
>
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