Nuts & Bolts
Aircraft Building
IN ONE RESPECT, AIRCRAFT welding is similar to aircraft painting. In painting, preparation accounts for about 90 percent of the time to do the job. This is also true in welding; 90 percent is a bit high, but prep time is greater than torch time. You must cut and form the metal pieces so they fit perfectly, clean them to ensure a good joint, and build and install
joint you’ve produced will be of poor quality. The final weld is an expression of the preparation that went into fitting the parts. If you’re welding to build an airplane or aircraft parts, then jig building is in your future, because fitting and jigging help ensure that the welded assembly conforms to design specifications. Let’s take a more in-depth look at welding jigs, how to use them, and how to
Prepping for welding RON ALEXANDER the pieces in a jib, if necessary. You can be the world’s best welder, but if the parts fit poorly, the welded
LEE ANN ABRAMS
Welding Jigs & Cutting Metal
A jig holds cut and fitted pieces of metal in the right places and at the right angles for accurate welding.
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ELECTRIC TRIM SYSTEMS Install this small, 14 volt servo motor to control Elevator, Aileron or Rudder trim.
Aircraft Building Servo
Trim Systems include:
Position Indicator
Rocker Switc h
T2-7A Trim System (.7 inch travel)....$225 T2-10A Trim System (1.0 in. travel).....225 T3-12A Trim System (1.2 in. travel).....245
STICK GRIPS
Stick Grips come as a complete kit.
G101 features a PTT switch...$32
Pushrod Assembly
Position Sensor
1.2 inch travel for flaps, vent doors, valves, etc..........$30
G205 includes a PTT switch and 4 mom. contact pushbutton switches for controlling 2-axis electric trim.............................$80
G101
G207 has 2 additional SPDT switches that can be used for controlling avionics, GPS, auto-pilot, speed brake, etc.........$105
G207
WING WALK
Unique rubbery feel, self-adhesive. Measures 26.5 in. x 9.5 in...... $16
Plasma cutter 2525-8 Pioneer Avenue, Vista, CA 92081* USA Phone 760 599-4720 FAX 760 599-4383 * NOTE: new ZIP code see us at:
www.rayallencompany.com
800-221-9425 Fax 618-654-6591
wicksaircraft.com For more information, visit SPORT AVIATION on the Web at www.eaa.org
cut pieces of metal to ensure a perfect fit. Welding Jigs Jigging is a means of holding pieces together at the proper angle and relative position. A jig allows the pieces of metal to be cut and shaped to the proper size as they are fitted within the fixture. Whether you’re building or restoring an aircraft, a jig can be an elaborate assembly designed to hold an entire fuselage, landing gear, or engine mount, or a simple welding clamp. When building an aircraft the plans often provide instructions for building the necessary jigs. In most cases, they use 5/8-inch or thicker particleboard for the base and support framework make of 1-by-4-inch boards. The thicker the material, the fewer tendencies for the jig to warp or move. With the board level and secure on legs or sawhorses, you draw the entire full-sized structure that you are building on it. Then screw or bolt (don’t use nails, which can pull loose) pieces of wood as necessary to hold the metal pieces in their proper places. The blocks of wood should be large enough to keep the metal from shifting and lifting while you weld. Blocks that are 1 inch by 2 inches are usually sufficient. Place the blocks of wood close enough to ensure that the tubing is held in place without shifting. Be sure to build the jig so you can easily remove the part when you’ve finished welding the pieces together. Use a saber saw to cut out the wood around the areas where you will actually be welding. This will reduce 104 DECEMBER 2003
Welding magnets can help hold small metal parts in position for welding.
Chop saw
the chance of igniting your jig. Take your time while building any jig. Measurements are critical for a proper fit. You do not want
large gaps between the metal pieces to be welded, and don’t bridge the gaps in poorly fitted joints with filler material. If you’re
building a fuselage, build a rotating stand so you can turn it for easy access to all sides of the fuselage structure.
MEMORIAL WALL A PLACE FOR REMEMBRANCE & REFLECTION Somewhere, somehow, all of us were introduced to aviation by someone. It may have been a family member, friend, or neighbor. Perhaps it was an EAA member. EAA’s Memorial Wall provides a place to remember that important person in a very special way. Located behind the EAA Aviation Center in Oshkosh, Wisconsin, the EAA Memorial Wall honors departed EAA members and aviation enthusiasts among park-like surroundings provided by ponds and trees and Compass Hill, http://www.airventure.org/2003/whattosee/compass_hill.html Your loved one’s inscription will be cast on a bronze plaque. New plaques are installed every year listing all honorees whose names were submitted before March 31st each year. The official ceremony and first viewing of the new installation takes place during AirVenture. Your memorial contribution of $350.00 covers engraving and installation costs, administration of biographical data for each individual, a video of the ceremony that is completed during the month of October, and permanent maintenance of the site. To submit your special person’s name, or to learn more about EAA’s Memorial Wall, please call the EAA Aviation Foundation at 1-800-236-1025. You can also access the link to register online. http://www.airventure.org/2003/whattosee/memorial_wall.html For more information, visit SPORT AVIATION on the Web at www.eaa.org
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Aircraft Building Clamps Clamps hold the parts in the jig while you tack weld them. An assortment of spring hand clamps, Vise Grips, web clamps, bar clamps, and C-clamps will make the job of positioning parts much easier. If you have several parts to produce, you may want to invest in a toggle clamp that can be screwed to the jig to reduce clamping time. Cutting Metal This may seem like a simple process, but in welding it requires a lot of thought and planning. Here’s a list of tools for measuring and marking metal for cutting: Flexible steel tape 6-inch flexible ruler 12- or 18-inch steel rule Machinist’s combination square Circle scribe
Carpenter’s square An assortment of steel punches A spring punch Do not use a pencil to mark metal for cutting; the lead will contaminate the metal. Instead, use a silver pencil or soapstone. If you’ll cut metal with a torch, use a scribe
Measurements are critical for a proper fit and to ensure the part fits on the airplane itself. or punch to the flame will not remove your guidelines. Soapstone leaves a mark that looks like chalk but will not burn off at high temperature. Only use a scribe for an actual cut line because the scribed lines create a stress point in the metal. (For more on stress risers, see “Building Basics“ on page 100.) After marking the metal, match the cutting tool with the stock
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you’re using, from snips and a hacksaw to a band saw (with a metal cutting blade), chop saw, die grinder, cutting torch, or plasma cutter. Whatever you use, cutting metal is a two step process: cut to obtain the correct size and then dress the cut using a file, grinder, or tube notcher to achieve a perfect fit. A chop saw is effective tool for cutting tubing. It is relatively inexpensive and can be purchased locally. Be sure to get a good supply of cutting wheels because you’ll use them up rapidly cutting steel. Most chop saws have a small vise built into the platform that holds the tubing while you’re cutting it. Hacksaws and die grinders work well when cutting steel tubing. You have several options for cutting thick stock. If you’re gas welding, your outfit probably came with a cutting torch. Controlling it can be tricky, meaning your cut won’t be perfectly straight, but a final fitting and dressing will clean it up prior to welding. A plasma cutter will cut through all types of metal from steel to aluminum to stainless steel. It consists of a small power supply with a plasma-cutting torch and a connection for compressed air. When air comes out of the torch, it’s electrically charged to create a 25,000-degree plasma jet, an arc you hold 1/16- to 1/8inch from the surface being cut. A plasma cutter leaves a clean cut and functions as a cutting torch or a band saw. You can make precise cuts using a straightedge guide, and accessories enable precise hole cutting. When using a plasma cutter, keep your hands away from the arc. You should also wear eye protection, heavyduty gloves, and long sleeves, and make sure your work area is clear of flammable materials because the process generates a lot of sparks. Next month we’ll learn how to shape the pieces of metal for a proper fit. 106
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