Final Fairing & Finishing - WEST SYSTEM Epoxy

A long flexible sanding block, or fairing board, is the primary tool for overall fairing on
wood and fairing compound. See Appendix A, page 23 for information on making fairing
boards. The key word is long, especially at early stages. Working on the same principle as
the batten, the sanding board should bend to the overall shape of the surface, but be long
enough and stiff enough to bridge the low areas and knock down the high spots over a
large area. A short sanding block and most power tools at this stage will simply follow
the contours and remove material from the low areas as well as the high areas.
We prefer aluminum oxide sandpaper as it seems to cut a wide range of materials, including
cured epoxy/fairing material, better than other types of sandpaper. Zirconia
alumina also cuts well and it wears longer. Stick sandpaper to boards and blocks with a
feathering disc adhesive, or use adhesive backed sandpaper. Either will permit removal
of the paper when replacement is needed. See Appendix A, page 22 for more information
about abrasives.
Begin your final fairing with 50 or 60-grit paper, concentrating on taking down the
high spots over a broad area. Change sanding direction frequently and check your
progress from time to time by eye or feel, or with a batten.
When you are getting close to final fairness, switch to 80-grit paper. If you will be clear
coating wood, begin to sand only in the direction of the grain to remove and avoid
cross-grain scratches. Vary the angle you hold the board to avoid sanding in or creating
a valley (Figure 3). As a final check, place the batten in different positions on the surface.
The batten should make solid contact everywhere on the surface with no voids
anywhere along its length.
Figure 3 Vary the angle of the board (0°,45°,90°) to avoid sanding in or creating a valley.
Filling low areas
Final Fairing 4
If you will be painting the surface, you may decide that it is more practical at some
point in the process to fill the remaining low areas with fairing compound rather than
continue sanding high areas. Often the decision to begin filling low areas is determined
simply by the volume of material remaining in the high areas and the time and effort
required to remove it.
Four methods for filling low areas may be used depending on the area or volume to be
filled and the degree of fairness and accuracy required. A large job may have applications
for all of these methods.