History of Hinge Slotting
Using a #11 knife blade to cut hinge slots in control surfaces has been done for decades- it’s highly dependent on the modelers’ skill, and time consuming. It can be physically damaging to both the wood grain and to the hinge.
While there are several type of hinge slotting tools on the market, the majority of them rely on splitting and separating the grain with a blade which can’t be controlled by the knife or the modeler – immediately followed by digging out the remnants to generate the slot.
Remember, a knife blade is a wedge – and we’re not splitting firewood in the backyard.
AeroBroach offers a revolutionary approach to hinge slotting
Each broach has been designed to penetrate the grain and roll the fiber downward – putting it in tension – so that it can be easily sheared by the serrations as the broach progresses through the control surface cap.
Each broach is a pre-determined thickness to generate the correct slot width for the type of hinge to be installed. The resulting slot length provides lateral adjust of the installed hinge with the mating control surface at final assembly.
- The “CA” broach is designed for use with the Cyanoacrylate Adhesive (CA) type hinges – the thin polyester strip with flocking bonded to the opposing surfaces – available in pre-cut packages and strip.
- The “60” broach is designed for use with the standard pre-pinned hinges such as Dubro #116 for up to 60 size airplanes.
- The “1/4” broach is designed for the heavy duty, two (2) piece plastic pinned hinges such as Dubro #257 commonly installed in ¼ scale airplanes.
The type of hinge to be used is determined by the modeler and largely dependent on the power, type of flying to be performed (skill level), and on the overall flying weight of the aircraft.
Hinges – The modeler must make conscious decision regarding the type of hinge that will be used in the model airplane – selection depends largely on the power, type of flying to be performed, and on the overall flying weight of the aircraft.
Typical hinges include the Cyanoacrylate Adhesive (CA) type (thin polyethylene strip with flocking material bonded to the opposing surfaces), and two (2) piece polyethylene pinned hinges. CA hinges can vary in thickness from 0.015” – 0.020”, while the pinned style thicknesses range from 0.025 – 0.045”, with some up 0.062” (1/16”) in thickness.
The modeler is usually responsible for generating the slot in the control surface caps with an appropriate tool that will accept the geometry of the hinge for chemical and/or mechanical bonding for permanent attachment to the control surface interfaces. Historically, knife type tools have been commonly used to split and separate the wood grain which generate wood shaving; the shavings must then be removed by either forcing them out through the backside of the slot or by digging the shavings out from the front side of the slot with a hook type tool.
The hinge selected by the modeler must be continually trial-fit until the correct slot width and length has been determined. The slot width is typically generated by multiple slices, which are incised parallel to the hinge line until the correct length and width is achieved; since this operation relies on the modelers’ skill, there are any number of unnecessary and misaligned cuts that are not included in the final geometry of the slot.
This process is time-consuming and largely damaging to the wood grain, and in some cases damaging to the hinge. Certain hinges have a flocking material attached to the opposing surfaces that can be damaged or removed by trial fitting. Splitting of the grain can extend beyond the useable slot length thus making the anchoring point unstable.
Since the hinges connect the control surface to the aircraft, is it imperative that they are securely attached to the airframe in a manner that is not mechanically detrimental to the airplanes structure in order to produce a controlled and predictable flight.
The AeroBroach is Different!
AeroBroach provides a means of forming a slot of pre-determined width for installation of commercially available plastic hinges in preparation for permanent attachment of the hinges to the control surface caps. The resulting slot is also wider than the hinge to compensate for lateral adjustment and final positioning of the hinge along the hinge line on the opposing control surface cap ( ie. aileron to wing, rudder to fin, and elevator to horizontal stabilizer).
The design of the broach provides accurate centering of the slot on the control surface hinge line and the serrated sides shear the wood perpendicular to the grain. The resulting geometry of the slot is similar to the hinge in thickness and width.
AeroBroach does not rely on splitting the grain, instead it generates the slot by shearing action perpendicular to the wood grain which reduces the time it takes to makes the slots and is less damaging to the wood.
But Why AeroBroach?
- Saves time
- Easy to use
- Accurate – broaches are designed to produce a slot that fits the selected hinge
- Each broach is clearly identified by laser engraving.
- AeroBroach can be used to clean-up and realign pre-cut hinge slots in ARF’s
- Great for field repairs – a new slot can be made on an inside corner without splitting the edge
- The broaching blade material is strain-hardened chrome/nickel alloy for strength and durability
- Laser cut for precision and accuracy
- AeroBroaches can be used with many commercially available handles and holders, used with or without a handle in a press, or adapted to a handle of the modelers’ preference
AeroBroach geometry, broach material properties and thickness, and the laser-cutting process used to fabricate the broach provides a tool to the aircraft modeler that precisely cuts hinge slots in control surface caps.
AeroBroach eliminates the need to drill the center of the hinge slot. When CA is applied to the joint, the precision slot generated by AeroBroach promotes rapid capillary action from the front of the hinge surface to the back because the hinge is not in being compressed or pinched in the joint by an incorrectly sized slot.