Simple Longboard Sanders for Cedar Strip Canoes and Kayaks

Particularly for builders of strip boats and hybrids, a longboard for fairing is an essential tool. Commercial products are available, but they tend to be very expensive. Here at CLC, we build our own from scrap materials, and you can, too.

Expert boat builder and instructor Jay Hockenberry shares his process:

A longboard is a hand sanding tool made from a long, narrow, slightly flexible board with abrasive fixed to its face and handles at each end. Unlike small sanders, which tend to follow the surface, a longboard bridges low spots and cuts high spots. This makes it one of the most effective tools for producing a fair hull.

In cedar strip canoe and kayak building, fairness matters more than simple smoothness. A longboard reveals bumps, ridges, and dips that power sanders often hide. With a small set of boards of different lengths and grits, you can move from rough fairing through final surface preparation with excellent control.

Construction

The width of your sandpaper strip or salvaged sanding belt determines the longboard width. The length is up to you if you're using sandpaper strips. Find a full list of materials and sizing information below.

If using a salvaged belt, split it at the factory seam and lay it down flat. The usuable length is the full width portion.

Rip and trim your plywood to match the sandpaper or belt size. Lengthwise grain is stiffer, widthwise grain is more flexible and is useful for compound shapes. 

Fashion two simple handles for the ends. Don't make them too small or too narrow as it is hard on your hands. These are 2x4 end cuts and 1-1/2" long.

Spread contact cement on both the back of the belt and the plywood base. Allow it to tack per the instructions on the can.

Carefully line up the edges and stick the parts together. Trim the ends of the belt flush to the ends of the base.

 

Orient the handles to suit on the back of the board and bond in place with CA or wood glue.

Use weights to ensure a good bond.

Your board is complete.

Here is an example of how you can use the grain to your advantage. The top board grain is running left to right and the bottom board it is running top to bottom.

Cross grain is very flexible, which is very handy feature on the inside of the hull or
deck.

Use and Technique

Use two hands, one on each handle Apply light, even pressure.
Sand in long diagonal strokes.
Work in a crosshatch pattern.
Mark the surface with pencil:
High spots sand away first
Low spots remain visible.

Longboard sanders are simple, inexpensive, and highly effective. Their performance comes from length and controlled flexibility rather than complexity. A small set of boards built from thin plywood and common abrasives will reliably produce a fair surface ready for fiberglass.

Materials

• Plywood, 3mm–9mm thick
• Sanding belts, 3"–6" wide, various lengths (40–120 grit)
• PSA (sticky-back) sandpaper rolls (120–220 grit for final fairing)
• Contact cement
• Wood glue or CA glue
• Wood blocks for handles

Notes: 

• Grain direction affects stiffness:
  • Grain running lengthwise → stiffer board
  • Grain running across width → more flexible board
• Build multiple boards with different flex characteristics

Board Sizing

• Width: determined by belt or paper width (3"–6")
• Length: determined by the usable flat section of the belt
• Typical ranges:
  • 20"–24" for coarse grits
  • 24"–36" for finer grits
  • For final fairing using 120–220 grit PSA paper, boards can be made slightly longer.