|
|
|
In a message dated 9/28/2006 2:43:50 P.M. Central Standard Time,
brent@regandesigns.com writes:
Brent,
I agree
with Scott 99% of the time but my experience with WLS is quite different than
his.
I have been using WLS primer since the mid ‘80s when we were using
the WLS paint system on IMSA GT race cars because it was extremely tough and
easier to apply than Imron. I believe I was the first guy to introduce the
product to the Lancair builders in the very early days of this list. My IV-P
was topcoat painted in ’95, still looks great and is frequently complimented
on its appearance.
Primer is NOT a topcoat. It should not be used as a
topcoat. It is designed to bond to a topcoat so you should not be surprised if
it bonds to whatever is applied over it, be it “”rattle can” pint, oil or bug
splats. If you want to fly before the final topcoat then apply a thin, cheap
one stage topcoat that you will sand off later.
Right. I readily admit to that mistake - that I did not have the
painter apply a "topcoat" before the PPG automotive base/clearcoat paint
(including the Diamont "Extreme Rainbow"). I was an ignorant neophyte
working alone in my garage without the benefit of the LML. Hmmm, I was
somewhat like a mushroom - kept in the dark with some, uh, fertilizer
occasionally thrown on.
Paint is heavy! If you put it on with a trowel you will have
pounds of extra weight. Spray one day and sand the next for the first couple
of coats. If it doesn't cure overnight then it is defective or wasn't mixed
properly or sufficiently. Spot prime areas that need lots of work. Stop
sanding when you burn down to carbon. If you keep sanding you will only make
things worse.
You do not need to, nor should you, wet sand the primer.
The surfactants, minerals and other contamination in, or the water itself,
will bond to the primer. I used guide coat (thin black fast dry paint) and 180
grit to get the surface flat followed by guide coat (again) and 220, then 320,
then 400 grit to progressively to remove scratches. Take three welding rods or
straightened wire coat hangers, bend them in half and wrap tape for 6"
around the cut ends. Use this like a mini carpet beater to clean your sanding
media of clogs.
Yeah, sure, now I know. The wet sanding did not produce any negative
effects.
After you are happy with the flatness and finish, spray on a
thin reduced primer coat with a couple drops of pigment in it so you can
remove it later with precision.
If the weave starts to show it is the
fault of the substrate, not the primer. The heat and pressure that is used in
the composite curing process induces stresses that relieve themselves over
time through microstrain. This process can be accelerated (then sanded flat
again) by thermally cycling the primed parts. I would spray some guide coat on
the various parts so they are relative dark in color, put them on supports and
place them in the summer sun. Repeat daily, weather
permitting.
Yep. Pre-preg glass certainly relieves itself.... I am sure others
have noted this "feature" although I probably would have had a better result
with a "topcoat" before painting.
The best tip I can give for producing the best finish coat is
to NOT do it yourself. Topcoat application is a skill that requires practice
and is best left to someone that does it on a daily basis. Find a reputable
automotive body shop with a large booth. IMHO you can get a better and cheaper
job at an automotive shop versus and aircraft specialist if you take the time
to explain how to handle, and the importance of, the various parts. A picture
of a completed aircraft is helpful. Let them do the final sanding and prep.
Hire a pinstripe specialist to do the graphics taping. It takes an experienced
eye to put a tape line on the 3D surface and have it look good from all
angles. I have seen lots of botched trim lines on the ramp. They draw
the eye like a bad toupee. Gee, your paint job looks...errrr...ahhh... fast!
Yeah!
Well, I built the craft for my education and "pleasure." I had to
succumb to pros only where the learning curve was too steep. Hmmmm, I
should have had a plumber do the hard hydraulic lines.
Most importantly, take the painter and his assistant aside and
give each $50 with the instruction to paint the plane like it belonged to
them. The fact that you trust them enough to give them a bonus up front will
make you a freaking hero! Promise another bonus at the end of the job too. Be
on site for the actual painting to help move parts, mask, clean, run for lunch
or whatever else is needed. A little humility and respect will be rewarded
with a quality job that lasts for decades.
This works. I have painted
two IV-Ps this way, both won outstanding workmanship awards at OSH and both
look great a decade later.
Well, the best I could do was "Outstanding Workmanship, OSH '98" and
"Outstanding Aircraft, S'N'F '99". She still looks pretty good (in the
sun) after 10 years of flight in the dirt below 18000 except for the chips from
constantly messing with the engine compartment and control surfaces.
BTW, the WLS reducer is way too expensive to use for cleanup.
Use some el-cheapo fast lacquer thinner for that.
Hmmm, I always had reducer left over from each "gallon kit" of WLS.
Anyway, I agree with you if one uses others and machines to prep and paint
the airplane. Hmmmm, 4000 hours to slow build, 3000 of which was
devoted to sanding one thing or another.
Scott Krueger
AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)
A man
has got to know his limitations. (Too bad I didn't know
mine) |
|