Dan - What you are seeing in the photo is the surface left by the rolling mill rollers.
This is the greatest problem with non-clad aluminum, other than the fact that the alloy is harder than the clad overlay of
pure aluminum on alclad material. Try not to bear down so much - only firm contact with the surface is necessary - shouldn't
be hard work....
Just be sure that the pads you are using are COMPOUNDING
pads, and not just normal wool pads. The ones we sell (EQ-140) are compounding pads, but if you go to the auto supply
and just order wool pads you'll get pads meant for polishing paint. If you want to buy locally, the 3M #05711 or
#05719 are compounding pads. Look for the wool hairs to be twisted up into tufts on a compounding pad. The REGULAR,
non-tufted wool, pad will probably never be able to clear the mill marks out of aluminum. It is very important
that you use a real wool compounding pad - and it is the number one problem I run into when people call our Tech Support
line with a problem.
If you
are using a compounding wool pad, then be sure that you don't use too much polish. The black "slurry"
should stay on the surface for no more than 60 seconds and then clear up by itself as you continue buffing. If you use
too much polish, it will stay on the surface as you buff beyond the sixty second timeframe, and there is so much polish on
the surface that it is just sliding around in the stuff, and not blending the metal surface.
When the "slurry" does finally disappear, you can continue to
buff for a bit - 30 seconds or so - which just uses the accumulated polish on the pad, and can work well - just don't
get the metal too hot by working the same area over and over and over... Hit one spot by passing the spinning pad over
the same track 6 or 8 times then move over to the spot next to it, then move to a third spot, then back to the first
(it has cooled some by then) and so on. Let that whole 2' X 1.5' area cool down while you work another area,
maybe two, then back to the first, and so on.
Another thing that might help is the use of the spur... any time you start to get a shiny look on the wool pad,-usually
after about 5 minutes of buffing - use the spur (looks just like a cowboy spur with a handle on it). Turn
the buffer over so the pad is up, lean it against your leg, turn it on and run the spur thru the wool. It should fluff
up and work better again. If you don't spur the wool, it quits working and you have to! When the spur raises
matted layers, you need to change pads.
The 6061 as used on the Sonex, Zenith and Murphy aircraft all have the mill finish problem you are seeing. It takes
many passes to smooth it out (I've done 8-10 NuShine II F9 passes - but of course we are only talking about a 60-90 second
timeframe for each pass.) Luckily, the polish job is much tougher and takes may times longer to cloud up than the clad
metal polished airplanes. So you are doing some of the ongoing work up front instead of during the flying time!
Don't sand it unless you find gouges in the metal.
Sanding will deteriorate the thickness of the sheet in an uncontrolled manner, and the material strength specifications will
no longer hold for the monocoque structure.
-Ron
