On Wednesday, September 9, 2020 at 5:08:11 PM UTC-4, Chip Bearden wrote:
On Wednesday, September 9, 2020 at 3:50:55 PM UTC-4, John Sinclair wrote:
On Wednesday, September 9, 2020 at 11:29:22 AM UTC-7, Chip Bearden wrote:
What UH said. He allowed me to supply a huge number of hours of work when we refinished my ASW 24 a few years ago. With two guys in the workshop (sometimes three), it was actually enjoyable sanding and talking soaring. But it takes a long time. I'm sure there's an easier way but I haven't talked to anyone over the years who's found it.

I recall there were spots--areas, actually--especially on the fuselage, where the gel coat just seemed a lot harder to sand than in other spots. And it was unrelated to whether it was over a seam where you would expect to encounter a slightly different gel coat/hardener ratio. Maybe it was where the factory had patched defects in the gel coat coming out of the molds?

One other thing--and I'll defer to UH and JJ on this--is that I wouldn't have started with the stab and elevators. The elevators and ailerons were the touchiest surfaces for me to sand, both removing old gel coat and finish sanding PU. The narrow chord combined with slightly concave surfaces meant it was really easy to sand through. And, of course, due to weight/mass balance considerations, we couldn't just spray on a whole bunch of stuff and sand some of it off. The sharper leading edge of the stab and the tight compound curves around the fairing for the rudder are a little fussy, also.

I had done some contouring/profiling on wings in previous years but was otherwise a rookie. If I were approaching it again, I would do it the way UH did. The first winter we did the fuselage (sans horizontal tail). The surfaces were big and relatively easy to sand and the consequences of slight imperfections were smaller. The compound curves, especially on the forward fuselage, were less of a problem than I had thought. In all, it was a good project on which to learn some technique.

The next winter we did the wings and tail. We were very careful with the wings because I think I have a "good" '24 and didn't want to have that little edge disappear in the dust. So we pulled leading edge templates from one wing and used those when applying the filler/primer. UH also wielded the grinder when we did the "B" leading edge mod and then we used templates to profile the outer portion of the wings where that applied (the leading edge is less sharp on the ASW 24B on the outer wings).

Sanding the big surfaces--fuselage and wings--went faster than I thought. My biggest mistake was not wanting to swap in new sandpaper often enough. It was still cutting but just not as fast. UH will laugh or be moved to tears for all the times he encouraged me to change paper and I declined.

It was a therapeutic, educational, and rewarding experience. And the glider still goes great and looks like new. We even did a few upgrades: e.g.., UH's fuselage vent and filling in the factory water dump ports on the wings.

Chip Bearden
Roger on changing sanding pads often .........they’re expensive, but nothing compared to what the labor is costing. Also a good idea to weigh the controls before starting and check and record the trailing edge weight (balance). Easy on the prime and paint on all control surfaces. I have had to sand off and repaint controls that didn’t check out after painting. Use a respirator when spraying AU! If you smell the stuff, your killing brain cells!
Enjoy!
JJ
Agreed, JJ, although UH might argue that my labor cost was pretty low. Or high, depending on whether he still recalls what a PIA I was worrying about tinkering with the airfoil.

We took it VERY easy on the control surfaces and actually came out a little to the good, IIRC, when measured against factory specs. The downside was more than one sand through. IIRC, he finally finished off the last elevator and winglet when I was at my real job one day rather than take a chance on another sanding/spraying/sanding cycle with me on the job! My hat is off to you guys who do/have done this full time. It's a huge amount of work and a few seconds of inattention can result in hours more.

UH did the spraying but I hung around to watch a bit. Respirator, of course, and he was wearing the full positive pressure treatment. I also wore a pretty effective dust mask when dry sanding (old gel coat). I had one left over that I tossed in my toolbox. When the 'Rona first hit, I went downstairs and checked: sure enough, N95. I haven't been able to find any more since then, though.

My one physical effect was "trigger finger" from clutching sandpaper on rubber sanding blocks with all the finish sanding I did. It took over six months to go away from the fingers of both hands.

JB

Now on my fourth refinish project in a club environment, I'll just say that it's an acquired taste. The fun part doing it with a club is that you can sometimes enlist lots of help. Our record is 10 (ten! ) RO sanders all grinding away at once on a pair of Grob Twin wings. Makes fast work of a really nasty project. The downside is managing "free" labor. You pretty quickly identify three sub-groups:

- Those who get it. A few minutes of dual and you're okay letting them work more-or-less independently until a new skill is required.
- Specialists. They lose interest in the boring stuff, but they can be counted on to spin a wrench or work on tricky sub-projects (like divebrake caps or control surfaces).
- Gophers. These are the ones who really want to help, but end up creating twice as much work with sand-throughs, flat spots, or destroying equipment. I assign them critical tasks like going to get lunch/beer or making hardware store runs.

Speaking of which... off to the shop tomorrow or Friday to put a couple coats of primer on LS3 Flaperons. Now there's a crazy-ass piece of work...

P3