Author: J. Smartt
Edition: Model Aviation - 1994/10
Page Numbers: 53, 54
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Weight Reduction for Duration Models

Electric duration models thrive on lightness. I go to great lengths so that my models will be lighter. I was a duration runner, and now I'm a duration flier.

I've been competing since 1947 and had a forty-one-year career as a long-distance runner, many years at the national and international level.

Running background and the value of lightness

Weight reduction was important during my running years. Commercial track shoes came with four or six spikes; I had mine made with three spikes each to save weight. I replaced laces with smaller-diameter ones cut just long enough to tie, and removed anything stitched onto the shoe (logos, stripes, etc.). Running singlets and shorts were the briefest possible and made from the lightest materials.

This habit of minimizing weight carried over into airplanes. Mine are lighter, and it starts with decent wood. Below are practical tips, primarily for wings (many apply to tail surfaces as well).

Tools and materials

  • A good digital scale is essential. I use an Acculab from Champion that is accurate to 0.1 gram.
  • Consider substituting thinner sheeting (for example, 1/20" for 1/16") and using smaller and/or fewer longerons, turbulators, and spar pieces where structurally acceptable.
  • Mark each piece of wood and balance sticks before use.

Balancing sticks and layout

  • Find the center of each stick, including trailing-edge (TE) and leading-edge (LE) pieces.
  • Balance each piece on a fingertip and mark the heavy end.
  • Always orient heavy ends toward the wing center.
  • When cutting to length, measure from the lighter end so weight removed comes from the heavy end and is discarded.

Ribs — methods for lightening

I use two primary methods for lightening ribs:

  1. Cutting round holes
  • Remove the eraser from a pencil, sharpen and serrate the metal ferrule, and use it as a hole cutter.
  • Use a fingertip as backing while spinning the “pencil” to cut holes.
  • Extra care in handling is required after removing material.
  1. Coring and TE holes
  • Core ribs fore and aft of the main spar.
  • Lighten the TE by drilling or punching holes spaced about one inch apart.
  • If ribs are notched (guppy-style) for the LE, scallop the inside of the LE between ribs after framing.

Wingtips and covering

  • Scallop the inside of bulky wingtips to reduce weight.
  • Cover the wing bottom with ultralight clear Mylar.
  • Use black MonoKote on the top for visibility.

Fuselage and other structural savings

  • Remove excess wood from the firewall.
  • Honeycomb pylon innards where possible.
  • Hollow-core fuselage formers.
  • Substitute thinner wood and smaller sticks for longerons when strength permits.

Landing gear and wheels

  • On Old-Timer designs with landing gear, use smaller-diameter music wire to save weight.
  • Be inventive with wheel construction; wheel collars are convenient but heavy. Eliminating collars can save 5–6 grams.

Hardware and electronics

  • Modify Sermos connectors by sawing off the rear portion of each connector; this can save about 1.5 grams per pair.
  • Remove heat-shrink from battery packs to save 2–3 grams; packs run cooler without it. Use caution: store packs in old (washed) sweat socks to keep contacts from touching.
  • Replace servo and extended wiring with smaller, lighter wire (telephone wire works well).
  • Reduce the weight of soldered splices: avoid long perpendicular splices, snip excess solder with diagonals, and add heat-shrink.
  • Removing the casings on two Futaba 133 servos saved me six grams. Extra care in handling is essential when protective coverings are removed.

Caution and closing

Extra care in handling is necessary when you remove protective coverings or otherwise reduce structural mass. I have enjoyed sharing these tips. Some naysayers may call them "rubbish" — remember, one man's rubbish is another man's treasure. As the bard said long ago, I shan't say goodbye; good flying.

Author

  • Jerry Smartt

Sources

  • Acculab scales:
  • Champion Model Products
  • 800 Carmen Court
  • La Verne, CA 91750
  • Lightweight clear Mylar:
  • Model Research Labs
  • 25108 Marguerite #160
  • Mission Viejo, CA 92692
  • Folding props & adjustable motor mounts:
  • SonicTronics
  • 7865 Mill Rd.
  • Elkins Park, PA 19117

Transcribed from original scans by AI. Minor OCR errors may remain.