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Styles of Model Airplane Wing Construction

November 14, 2011



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Airfield Models (http://www.airfieldmodels.com/)Styles of Wing Construction for Flying Model Aircraft

There are a number of types of wing construction for model airplanes.  Methods range from simple outlines covered in tissue to complex geodetic structures.

The examples on this page are the most typical construction methods used to build wings for radio control, control line and free-flight model airplanes.

Also see

 
 

Non-Sheeted Rib and Spar Construction

Wings that are not sheeted are built with ribs that have an outline identical to the airfoil outline with whatever cut-outs are necessary.  This type of wing is arguably the simplest to build of wings that have ribs as well as the lightest.

Typically this type of wing is very flexible.  The covering will stiffen the wing somewhat.  Note that shrinking the covering, regardless of type, can cause the wing to warp or bow.

A typical non-sheeted wing that is lightweight and easy to build.

A very light wing that is designed to easily handle the flight loads imposed upon it.

 
 

Semi-Sheeted Wings

Often wings such as the ones above have some sheeting added to the center section to strengthen it and provide more support where the wing mounts to the fuselage.  The remainder of the wing has no sheeting.  The unsheeted sections of the wing have a rib pattern that is the same as the airfoil.

The ribs in the sheeted section of the wing must have the thickness of the sheeting cut from the perimeter of the ribs.

I usually cut all the ribs using the master pattern.  The ribs that will be sheeted are stacked and pinned together so that the thickness of the sheeting can be cut away using a scroll saw.

D-Tube Wing

A typical D-Tube wing.A D-Tube style wing is sheeted from the main spar to the leading edge on both the top and the bottom of the wing.  Aft of the main spar may be cap strips.

The rib pattern is created by subtracting the thickness of the sheeting from the outline of the entire airfoil if cap strips are to be used.

If cap strips are not used then the thickness of the sheeting is subtracted from behind the leading edge to the rear of the main spar.

A true D-Tube has shear webbing.  The webbing along with the leading edge sheeting gives it the "D" shape when viewing a rib cross-section from which the wing derives its name.

Many people believe a D-Tube wing is significantly lighter than a fully sheeted wing.  That is not true.

A D-Tube wing uses the same amount of glue to hold on the skins and cap-strips as a fully sheeted wing does.  The entire perimeter of each rib is glued.  The difference in the amount of sheeting used is minimal.

If you were to weigh the amount of sheeting that would be used to fill in the empty areas of a D-Tube wing you would find that it only weighs a few grams on a typical .40 size model assuming contest balsa is used.

 
 

Fully Sheeted Wing

Rustik has a built up balsa wing that is fully sheeted.Fully sheeted wings can either have a built-up rib and spar structure or a hot-wire cut foam core.

Built-up versions have a rib pattern that is identical to that of a D-Tube wing.  The thickness of the sheeting is subtracted from around airfoil to make the pattern.

Most builders have difficulty with their first built up sheeted wing, but the experience is valuable and a poor initial result should not dissuade you from trying it again.

You will not see too many fully sheeted, built-up wings on sport models for several reasons.

As I mentioned already, many builders are afraid to even attempt it because significantly more skill is required to build a sheeted wing than other types.  The ribs must be sanded to flow smoothly from one rib to the next in order for the sheeting to lay smoothly without undulations.

Additionally, it can be difficult to sand the skin smooth at the seams.  This is mostly a problem with poor technique or using the wrong glue.  The skins should be sanded after joining them but prior to gluing them to the rest of the structure.

Excessive sanding after the skin is glued to the ribs will cause it to have a "starved horse" look.  This is because the sheeting sands away at a faster rate where it is supported by the ribs which results in ripples in the skin.  In the worst case it is possible to sand through the sheeting at the ribs.  Sheeted wings also weigh more than a non-sheeted wing, but only marginally more than a D-Tube wing.

Most builders do not build fully sheeted wings for the above reasons and the fact that a fully sheeted wing does not fly significantly better than a D-Tube wing.

Sport models having fully sheeted wings most commonly have a foam core which are exponentially easier to build.  The main drawback of a foam core wing is weight.  A properly designed and well built balsa wing will always weigh less than an otherwise identical foam core wing.

Some people will claim that they can build a foam core wing that weighs less than a balsa wing.  Without exception, every person who has made this claim to me could not produce a wing to back their claim.  I'll believe it when I see it.

 
 

Jedelsky Wing

A Jedelsky wing is created by edge-joining two sheets of balsa wood at an angle.  The angle on the bottom of the wing formed by the two sheets is left intact which creates an undercambered airfoil.

The upper surface of the wing is carved, planed and sanded to an airfoil shape.  Jedelsky wings are most commonly used for free-flight gliders.

 
 

Hybrid Wings

A set of spars and a lattice skin create the airfoil shape for Thwing!'s wing.The above are the most common types of wing construction, but there are many other ways a wing can be built.  One method that is used from time to time is a series of spars that have cap strips overlaid to create the airfoil.  No ribs are used.

Each spar is the height that an airfoil would be at the percent chord at which the spar is located.  The caps form the curve of an airfoil over the spars.  As few as one spar can be used.  A sheet may also be laid over the spar rather than ribs.

This type of wing structure is most commonly used on very small models where cutting a set of consistent and accurate ribs is most difficult.

I used a variation of this construction method for my Thwing! design.  Rather than using cap strips, I created a lattice skin made from balsa.

 
 

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About Airfoils used with Flying Model Aircraft
How to Plot and Draw an Airfoil

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Copyright 2003 Paul K. Johnson