H in t s F or H o m e b uil d e r s
Splicing a Broken Cap Strip
A simple jig
By Cy Galley
Have you ever had to splice a broken cap strip on an existing rib? You need accuracy for a good glue joint when you
scarf in the repair piece. Here is a simple jig that is easy to
make from a simple U-shaped aluminum extrusion available from a local hardware or lumber store. It is also very
small, so it will fit inside your wing.
Select the width of your extrusion to fit your rib cap strip;
they come in 1/4-inch, 3/8-inch, 1/2-inch, and 3/4-inch
widths. I believe they are sold to protect edges of plywood.
The other thing that makes this jig work so well is the
X-Acto Razor Saw. As the 3/8 inch inside is actually 1/2
inch on the outside, it is easy to get a 1-to-10 scarf by
making a mark on one side, then measuring up 5 inches
and making a mark on the other side. You must adjust your
marks for other width extrusions, of course.
Clamp about a 3/8-inch-thick straight edge between the
two marks. Use the clamped straight edge to guide the cut
perpendicular to the extrusion. The razor saw will easily
cut the aluminum extrusion. Note: I blocked up the far side
so the guide didn't twist or slide off.
Clamp your wooden cap strip material in the channel and
saw your replacement. Scarf the damaged end on the old
cap strip, also using the channel. The new piece should
be a good fit without gaps. If it doesn't clamp both the new
and the old together, then run the saw down between the
two until there isn't a gap.
There are several sizes of razor saws. I only included two
in the photo. As one goes up in channel sizes, the saw has
to get longer to span from guide slot to guide slot. In that
case, the dovetail saw shown on top in the accompanying
photo might do the job. However, use a hacksaw to saw
the guide slots in the aluminum extrusion.
Advisory Circular 43.13-1B requires an overlapping gusset on both sides as a finish, which is also a good idea on
a homebuilt.
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Vol.2 N o.6 / June 2013