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Building Model Airplanes from Plans and Materials

by Bill Kuhl

 

 

                                     

                            Denny Dart II flying indoors                                                                                                                     Denny Dart II flying outdoors

 

 

 Buying kits is convenient and saves time. You know that there should be enough materials. Distribute the kits to the students and they shouldn’t have to ask endless questions about where to find this piece and that piece. You don’t have to go to one source for rubber, another for propellers, and another for balsa. Everyone should get his or her own instruction sheet.

 

If you don’t mind the extra work and time, building model airplanes from materials can save money. With careful shopping from the right sources and using a "balsa stripper" you can save even more money. No doubt the plastic prop assemblies will have to be ordered. Some hobby shops carry rubber strip but not in a variety of widths and lengths. For more than a couple of airplanes, it is best to purchase rubber by the pound.

 

               

 

 The Denny Dart II can be built from just two sizes of balsa 1/16" and 1/18" when the balsa is cut from sheet wood.                         Motor sticks cut from 1/8" sheet

   

Most hobby shops will carry balsa wood in a variety of sizes, but again if you are building many airplanes this is rather expensive compared to ordering balsa mail order in larger quantities. Mail-order companies selling balsa normally have a minimum order amount and charge shipping so this needs to be considered as well as the price. Depending on where you order from and what you pay, it might be possible to specify the weight of the balsa you purchase.

 

                                                           

While it is possible to purchase balsa in pre-cut strips, cutting your own strips will be significantly cheaper. The easiest way to cut balsa strips is with a device known
as a balsa stripper. One popular model of balsa strippers costs just a few dollars and holds a common hobby knife blade vertical at the width that you adjust. With one
edge of the stripper pushed against the right edge of the balsa sheet, push the stripper away from yourself.
 

Strip balsa on smooth, flat surface with the edge of stripper pressed firmly against balsa edge. The blade does not pass completely through all the time, so turn over
sheet and make a pass from the other side to complete the cut. If the balsa sheet does not look straight, fix this by making a cut with razor blade and straight edge.

 

 

Covering

 

Kits that use the plan for the covering material are adding significant weight with this covering material. The covering also can shrink a significant
amount with changes in weather. Although you can purchase tissue for model aviation sources, I have found gift wrap tissue that is comparable
weight and much cheaper.  

 

                               

 

This gift-wrap tissue was the same weight as the tissue I had ordered                             This 6" square piece of "Japanese Tissue" was the same weight as the
for model airplane use.  Tissue can vary in weight considerably.                                         the gift-wrap tissue. Plan material covering is much heavier. 

 

  

                              

                       Plan page covering was twice as heavy                                                                         Gift-wrap tissue sample slightly heavier                

 

 

 

Propellers

  

                                 

                             Midwest 6" Propeller                                                                                                                                Sig 5 1/2" Propeller

 

 The biggest expense no doubt will be the propeller/hanger assembly. Most popular are the Midwest or Sig propellers.  Midwest is 6" diameter and is
a heavier propeller, but will work very well. Sig prop is 5 1/2" diameter but lighter.  Propellers normally come out of balance (one side heavier than the
other), it is worth it to spend time trimming from the heavy side until the propeller blade will remain horizontal. Also watch that the prop shaft is not bent
from straight which will also cause vibration.

 

Building Supplies

Some of the supplies you need can be found from non-modeling sources such as discount stores.

 

                                             

 Push pins used to hold balsa strips in place while the glue                            Ceiling tile makes an ideal building board to push pins through, 
 is drying can be found in a variety of stores.                                                        but three layers of corrugated cardboard can work provided it is perfectly flat.
 

 

                                            

 

 Single-edge razor blades can be found at building supplies                                      Wax paper used for covering plans can be purchased in grocery stores. 
and hardware stores.    

 

Rubber Strip

 

                                                     

       Rubber strip can be purchased in many quantities, I purchase                                        I cut and tied the lengths of rubber to save time and waste later 
        in one pound boxes from FAI Model Supply                                                                           (was afraid what might happen to the one pound box of rubber if 
                                                                                                                                                                 students were cutting).

 

Normally when you purchase a kit, it only comes with one strip of rubber or a rubber band that is way too short, when that breaks, the plane is grounded or
you rob from another kit.  Most modelers purchase rubber in one pound boxes although it  can be purchased in smaller amounts. For model planes that
will fly with a six inch plastic propeller, 3/32" wide strip work well, or possibly 1/8" for a larger, heavier plane. 

 

 Glue

 

                                                           

    

 My preference for students is to use the yellow carpenters glue because it is economical and gives off no annoying odor.  Easy to find in building supply
or hardware stores. Can place a blob of glue on waxed paper and apply with a toothpick. Glue stick is used to adhere tissue covering to the wood
structure. Duco is a brand found in some hardware stores, similar glues such as Testors, Ambroid, or Sigment will be found in hobby shops.

 

 

Darcy Whyte uses the "Tacky Glue" for his building sessions for his Squirrel model airplane.  I plan to experiment more with this glue.

 

The Building Process

  • Have the materials ready and available. Try to minimize waste.
  • Have to get across to the students that it is important to do things in sequence.
  • Get across to the students the importance of NOT making their planes heavier than need be.

 

 

 

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