Supplies, Tips & Techniques for Balsa Model Building

Do the job right with the right supplies and accessories
Working with these supplies and tools requires practise, learning, and some ingenuity and improvising.

 

1. Work Surface:  We suggest using an accurately flat, sufficiently large, soft balsa or pine board or piece of 3/4" softwood plywood, clean, flat heavyweight corrugated boxboard, 2’ x 2’ ceiling tile, or dense insulation foam board as a construction surface for use with these pins. Cover work surface with wax paper to permit easy removal of finished assemblies.

 

2.  Assembly Pins:   These make the job easier, produce better quality work. Two structure sides can be duplicated, one one top of the other with wax paper in between, for symmetric structure precision. Also provides light clamping pressure for setting glue joints at any angle. Use the pin shoulders to hold the work, or pin through a piece of scrap used to press the work to the workboard.  Gentle side pressure can be applied to keep joints in place while drying, and cambered ribs can be held vertical with 1 or 2 pins on each side of the rib. Note: Use very light pressure on balsa parts and do not pin through balsa on Leading Edge or Sorcerer models! 

 

3.  Speed Winders are a necessity for competition, especially for the Leading Edge & Sorcerer, which may require more than 1500 winds. Also aids in precise counting of winds, which is an essential part of testing and adjustment for optimum flight. Use 15:1 or 10:1 winder for Leading Edge & Sorcerer; 5:1 is OK for other models. Do not use an electric winder for competiition! ALWAYS COUNT THE NUMBER OF WINDS! 

 

4.  Mylar Film
We offer 1.4µ Mylar film in rolls 12.5” x 10’, enough for covering several models.  It is superior to tissue in several ways.  It is included with the Leading Edge kits, and may be purchased separately for the Sorcerers. We include updated instructions for use.  Application takes practice, but is worth the effort.

 

5.  Cutting Tools:
[all cutting tools are sharp and potentially hazardous. Use may require competent adult supervision]
Xacto Knives: We offer individual capped knives with safety caps and replaceable blades.  This is the long-time standard, suitable for kids over age 8 with competent supervision. 
Excel Brand single edge razor blades. Single edge blades are the choice of experienced modeler. Our blades are sharper than Xacto blades, more effective for most cuts, and make beautifully clean cuts if used skilfully.  However, they are also more hazardous to handle, must be disposed of safely, and are not recommended for children younger than 12 years.  We offer them in 10-packs.

 

6. Our Ikara Propellers are designed by Ray Harlan. They feature a highly efficient combination of weight, size, shape, and pitch, and are not available elsewhere.  They are extremely light and easy to modify. They twist easily to change pitch angle, and can be reshaped with sharp scissors to change diameter and surface area. They are available separately to enhance the performance of the Sorcerer or other model. 
SPECIFY 8.8" PROPS FOR TSA MODELS

 

7.  Care and selection of Rubber Motors:
Flight Central offers a variety of thicknesses of competition rubber string. For longest life and maximum performance, lubricate the rubber motors with Sil-Slick, available at our supplies page. Store motors in marked Zip-Lock Bags. Use Speedwinders for proper stretch-winding (directions in model kit package), and always count winds. Do not use an electric winder!! Select motor acording to weight specs and energy requirements, model weight and room dimensions, among other things.
 The selection of a motor, and determination of length, is dependent in part on the ceiling height of the competition venue and the prop pitch angle.  You need enough torque to get the plane up to the ceiling in a steady, gradual climb. The torque curve at that height should yield just enough to start the plane flying level, after which it descends under power.  Also, the greater the prop pitch angle, the more torque you need.  High ceiling, steep prop pitch indicates more rubber mass.  A thinner rubber gets more winds and a shallow prop pitch, spins faster.  A thinner rubber may not provide the power needed for climbing.  Experiment!  There is no straightforward formula for calculating this.  Another variable is number of winds.  We sell replacement motors. Select #377 (3/32") for Leading Edge or Sorcerer. 
Important: You MUST attach an O-ring to the tail end of the motor to facilitate removing and replacing the motor from the motor hook for winding. Hold the motor at 30 degrees from the fuselage while winding, and have your partner hold a cardboard sheet between the motor and fuselage to protect the airplane from damage if you lose control of the motor while winding. Wind about 1/3 to half the winds while stretching the motor to 2 to 7 times its length, then walk in slowly while winding the remainder. 

 
8. SCALES: .01g x 100g digital pocket scales
Digital Scale: .01g resolution, 100g capacity. Small portable scale is reliable to approx. .02g. Scale must be calibrated with standard weight according to product directions. It is extremely sensitive: use only on flat, level surface, away from all air currents. Turnertoys tests all scales for proper function before shipping.

9. Adhesives:
A. Ambroid Cement  is the choice of many experts. It is very forgiving, does not require joint pressure, and can be removed from an incorrectly built joint with acetone. Apply sparingly with toothpick or balsa sliver. Where weight is critical, do not follow tube directions; apply to one part only.  Where strength is more important, apply to both parts, rub into wood and remove excess, allow to dry a few minutes, then reapply to one part and mate surfaces. Hold in place until dry with gentle pressure with pins. (Ambroid is similar to Duco Cement, the old standby, at hardware or hobby stores.)
Potential Negatives: Contains VOC's (volatile organic compounds) which may create an inhalation hazard. Use with adequate ventilation. Also hardens by drying, rather than curing, so open tube may harden up before it has been completely used. Do not pour working supply into dish or cup. 
B. We also recommend a water-based glue such as Elmer's Professional Carpenters Glue or Titebond II, which can be cleaned up (before they set - approximately 20 minutes) with water, and afterwards, with some difficulty, with hot water.  A properly established joint using them is very strong, and has a very slight flexibility. They have only fair initial tack strength, unless heavy clamping pressure is used (not possible with these delicate materials). NOTE: Grip Pins allow some clamping pressure to be applied either vertically or laterally at almost any angle. These glues are minimally toxic and are almost completely free of VOC's. Pour a little into a disposable cup, apply sparingly with toothpick or stick of balsa. Excellent for use with younger kids, especially in groups!
Potential Negatives: They work best when contact between wood pieces is precise and intimate, and some pressure can be maintained until they set (use pins). They do not hold as well on end-grain as they do on side or face grain. They are only slightly thixotropic, i.e., a large drop of this kind of glue on a vertical surface will run a little. Assemblies must be allowed to set at least one hour before being moved.

C. Cyanoacrylates (Crazy Glue) are available in thick gap filling or thin formulations. In either case they set up quickly and can make assembly time much quicker. Fillets to strengthen joints can be made using the thick formulations but they have to built up bit by bit.

Potential Negatives: Contains VOC's (volatile organic compounds) which may create an inhalation hazard. Use with adequate ventilation. Also they set up very quickly and will stick anything together including fingers (they are used in some surgeries exactly for this property). Not recommended for use with groups of kids. Also the joints made with Cyanoacrylates are brittle - a model made with CA may not survive a crash that a kit made with more flexible  would.

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