Hi, Ferg --
> However, what is the dial indicator?
That's an $8 oriental, standard dial indicator. It's mounted on a
U-shaped frame of ali, 3/4" wide, 3" on the legs. For those with
time on hands and need for speed. It is said laminar flow is not
possible beyond c. 45% of chord, but a Mike Arnold used it on his
design to achieve a claimed 65-70%. Theory is max waviness is .002"
in any 2" of chord, or .003" on mine, else laminar flow ends there.
When you move across the surface, you get needle movement as airfoil
shape changes, but the wavies are still obvious. Arnold's web site
is www.mypage.onemain.com/airmike , but no need to buy the tapes.
> ...and is the System III a commercial product that just cannot be beaten?
Fold, don't beat! See systemthree.com. They supply products mostly
to glass boat builders (cf. environmental brutality). Their finish
coating is a water-reducible polyurethane. By odor and physical
properties, it appears similar to Poly Fiber Top Gloss,
solvent-resistant, and so far non-yellowing. Advantages of a
clearcoat process are several, tho originally just to improve
appearance of metallics. Auto mfrs now clearcoat even whites.
Don't know if glossier than Top Gloss, but less danger of cutting a
single color coat too thin in the final sanding/buffing. It also
permits one clearcoat over everything, including automotive metallics
for trim. Water clear over solvent base sounds bad, but a test has
been passed so far (using a "dead" base such as Dupont Lucite, the
real old-style of lacquer, after 30 days). Further advantage of
mitigating the bump at the trim's edge. Haven't seen any negative
comments on the boat bldrs newsgroups yet. Disadvantage may be a bit
more weight, even with a permissibly thinner base. And some glazing
compounds can cloud this type clear coat, so must test them.
Their primer is claimed to be a UV shield. Interesting that PolyFiber
once pooh-poohed chemical UV barriers, and had a dark gray intercoat
as a physical barrier. Now just one white coating. Same as S-III???
> Did you use spraygun or roller?
The base will roll on and flow out, with proper foam roller. Haven't
tried clear w/roller, but they sell a trial kit.
Like similar products, it just don't like to come out a spray gun,
especially HVLP, even gravity feed. Tip size? A pressure pot I bet
solves it, and that's the way to paint a plane anyway, especially
under fuselage. Elsewhere wrist fatigue in worst way, keeping gravity
cup filled.
There are automotive clear coat systems, with option of urethane
additive. But ironically much more expensive, and the additive
especially requires full respiratory protection. Fully solvent
resistant probably not.
Regards,
Fred F., A063
|