Tips and Techniques

How To Use AeroBroach

“Practice makes Perfect”

It is highly recommended to practice the following procedure until the modeler develops a technique and is satisfied with the results.

The following procedure should be used on all built-up panels, unless the control surface caps have not been installed.

For unsupported caps or cap without backing:

Once the hinge line has been established on the mating control surface caps, align the broach at the mid-point of a hinge location, and gently push the tip of the broach downward into the cap perpendicular to the control surface until approximately 2 teeth are engaged in the cap material. Rock the broach parallel to either side of the hinge line a distance approximately equal to the width of the broach (~3/4”). This establishes the cut-line. Push the tip further into the cap material until the tip is again exposed on the opposite side. Withdraw the broach slightly – following the cut line, use the teeth to “saw” the sides of the slot almost square until the tip is exposed at either side of the slot. Withdraw the broach again and gently push the broach straight down following the cut-line until the teeth penetrate the thickness of the cap.

For ARF kits:

Estimate the thickness of the cap and mark the broach accordingly (because you can’t see the tip through the covering), establish the cut-line and gently push the broach straight downward into the cap material  in a single motion. Caution – do not use excess force.

For thick caps or caps with integral backing:

Establish the cut-line per the above procedure, then re-align the broach with the mid-point of the hinge line and push the broach straight downward into the cap material  in a single motion to either completely penetrate the cap thickness or, depending on the modelers preference, to a pre-determined depth. Trial fit the hinge until the correct depth is achieved. When complete penetration of the cap is not required or cannot be accomplished, the serrated teeth along the sides of the broach can be used to square the slot, then use the tip to remove debris.

For built-up panel construction with caps not glued in.

If the caps have not been installed, the best method to form the slots is to attach the broach to a suitable mandrel using the holes in the tang for #4-40 screws, and pierce the cap material in a single motion        using a press (milling machine or drill-press will also work).

Always use a backing with a free cap!

The preferred backing material is the pink or blue extruded foam available at most home improvement centers, or a thick scrap balsa (not glued to the cap) – you need to protect the tip of the broach. The backing prohibits the opposite surface of the cap from breaking out ahead of the broach.

If you have a milling machine UNPLUG IT NOW! Excellent results can be achieved by aligning the back side of the broach with the inside face of the back jaw of the vice – then lock the spindle. Move the front jaw within 0.010” of the broach to form a die set.


Caution Statements :

1) Techniques and results will vary depending on the density of the balsa.

2) AeroBroach is intended to be used on balsa wood caps, not ANY hardwood. Consider backing the caps with plywood or carbon fiber if strength or stiffness is an issue in these areas.

3) ALWAYS PIN two (2) piece hinges through on both caps! Don’t rely on epoxy or any adhesive alone for resistance to hinge pull-out. Use anything from round style toothpicks or dowels, to steel roll pins as insurance.