Robart Hinge Points in Sheet Control Surfaces
I use the all-metal Hinge Guide made by Robart which has
worked well for me. The Robart hinge guide is the best of all the hinge
guides made. It has threaded inserts so that it can be used with any size
Hinge Point made by Robart.
Unfortunately, hinge guides are not foolproof. The guide must be held firmly against
the surface of the wood that is being drilled and not allowed to shift. It is best if you
have someone hold the guide while you drill. Use a wheel collar on
the drill bit as a depth stop. The hole in the control surface must be
deeper than the hole in the fixed surface to allow the hinge to be inset.
I do not use a power tool to drill for Hinge Points. Instead I use a
Pin Vise which gives me greater control. A power drill or
Moto Tool drills
through balsa so fast that mistakes can be made in the blink of an eye. If
the wood is exceptionally hard, then I will sometimes drill the first 1/4" or so
with the pin vise to get the hole started in the proper direction and then
switch to a Mini Mite to finish it off.
Constantly check the
progress of the drill bit by sighting from the top of the control surface to
ensure the hole is perpendicular. Also sight from the end of the surface to ensure
the bit is centered in the surface. The bit can cut through the outside
surface if the hole is drilled at an angle. This is more of a problem with
tapered or thin surfaces.
The bit should be backed out frequently to clear wood chips because balsa
will clog the bit. If the bit is clogged it tends to tear balsa wood
rather than cut it cleanly.
Place your fingers over the wood
where you are drilling so you can feel the bit moving into the wood. This will
alert you if the drill starts moving in a direction that will cause it to break through
the surface of the wood.
Tip! One little trick I like is to
sandwich a Hinge Point between the screws that attach the
control horn to the control surface. It works only when the control
horn has screws on
each side of the horn rather than aligned front to back. The screws must
be spaced at least the diameter of the Hinge Point apart. I use this
technique to sandwich tail wheel wires in the rudder as well.