.
Joining the Wing Halves (cont.)
Making the Hard Points
Make the cavities for the hard points by “hogging out” the foam between the marks
you made previously. Only about 1/4″ of depth is required here. Filled these spaces
with a mixture of 5 minute epoxy and microballoons to create the hard points. Try to
keep this mixture as level as possible with the end of the cores as it is a bugger to
sand very much. Mark the location of the wire channell on the bottom of the wing so
that it can be easily located after the cores are joined. Using a nail or piece of
music wire, make some small pinholes up and down the entire chord of the wing to
enhance bonding.
Allow the filled epoxy to harden. If you used 5-minute epoxy, this should not be
long, as filled 5-minute epoxy has a very short pot life.
Sanding the Dihedral
Place wing cores back in beds with root end sticking out about an inch. This is
the best way to hold the wings while sanding dihedral angle without damage to wings.
The XP-4/XP-4.5 calls for about 6-1/2″ of dihedral, measuring with one wing flat on
the table, and the other wing propped up with something.
To sand the angle into each wing-half, prop each wing have up so that the wing-tip
has half of the “full dihedral” measurement, which in this case would be 6-1/2″, so
prop each wingtip up 3-1/4″ when sanding the root. One easy way to sand this angle is
to use the edge of the table as a guide with the root of the wing flush with the
edge. Using a sanding block or bar, sand the angle into the root. Check frequently
not to over sand. It doesn’t take much so take your time here. Test fit them together to ensure you have sanded a nice, straight line into both cores.
