My Quickie Q-200: Sanding

Saturday, August 09, 2008

Sanding

Over the years, we have learned better sanding techniques than were called out in the original plans. I'd thought I'd cover some of the main sanding tools that I now use. (As always, click on the photo the the full size image).

Again, the main idea is to lay your filler material on THICK, then sand down the high spots until you just reach the fiberglass. There are two excellent on-line descriptions that describe best practices.

Chapter 25: The Contouring Process

and

Finishing a Composite Airplane

1. Sand Paper The first strong recommendation is to buy only automotive body shop quality paper. I think that the 3M paper is the best and longest lasting and is my preference, by far. I get my paper at a local automotive paint shop supply store.

Almost all of the work will be done with 36 grit paper and I keep a good supply on hand. I really like the stuff that comes with the adhesive backing. It's 2" wide by 16" long.

2. Small Sanding Blocks Try and avoid doing any sanding, at all, with just your fingers - always use a sanding block. If you use solely your hands, the paper will follow the contour of the thing you are trying to sand down and you will not get a smooth surface.

I make extensive use of the rubber sanding blocks - there are both 6" and 8" available. I stick the paper to both the curved and straight sides.

For fillets and the like, I simple stick some 36G on a piece of cardboard tube.

I have also used this single stick board for many years.

3. Long block I used some shelf board I had laying around and cut it to 32" and mounted a section of aluminum angle for a better grip. This length allows me to use two 16" sticky back strips. With fresh paper, this is a great tool and really cuts into the micro.

I strictly use 36 grit on the whole plane until I get the contours that I want. When I have that desired shape I switch over to 80 grit. All the 80 grit does is to knock off the highest cuts left by the 36G.