Airfield Models - Wing Construction Example

Mount a Model Airplane Wing to a Fuselage - Part I

May 02, 2015



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Airfield Models (http://www.airfieldmodels.com/)Mount a Model Aircraft Wing to a Fuselage Part I

Mounting the wing is one of the most critical steps in building the model.  Depending on the methods used, it can be tedious, but a methodical approach with an experienced helper will make it much easier.  Failure to get this right will result in a model that will not fly straight or trim properly.

Your goal is to mount the wing absolutely square to the fuselage centerline in all respects.  Additionally, the incidence must be correct.  The wing should be centered (both tips equal distance from the fuselage) and perpendicular to the fuselage centerline.

The tips should be equal height above the building board as well.  Not counting incidence settings, any adjustment made affects the others.  Therefore, squaring the wing is a matter of "dialing in" more than anything else.

Obviously the fuselage must be constructed before the wing can be mounted to it, but if you can leave the forward area of the fuselage open as I have done here, this task is simplified and more accurate.

 
 
Before the wing can be mounted, it must be very close to its finished shape. Before the wing can be mounted it must to be shaped as closely as possible to its finished shape.  A razor plane is used to rough-in the leading edge.  A long sanding block finishes the job.

Do not make the mistake of giving the leading edge any shape that pleases you.  The leading edge shape should closely match the plan.  In the worst case a poorly shaped leading edge can lead to devastating stall characteristics.

It is best to cut out a cardstock template to place over the leading edge as you shape it.

Take special care with the leading edge - it's shape greatly affects flight characteristics. This shape very closely matches that of the airfoil as designed.  Notice that the sheeting and leading edge are still over-length.  The excess must be trimmed and sanded off before proceeding.
The wing must be measured from an identical point at each end of the wing. Most plans indicate that the wing tips should be glued on prior to mounting the wing.  In theory that is a good idea, but I like to mount the wing before the tips are in place.

The shape of the tips is usually open to interpretation and one tip may or may not exactly match the other.  If the rear, outboard corner of the tip is rounded then there is no set point to measure from.

Therefore I measure to the last rib.  Wing tips that vary slightly in shape will not affect flight or trim characteristics noticeably.

The tips are sanded perfectly square. It is important that the tip ribs are related identically.  Some wings may have ribs that are not parallel to the centerline of the aircraft.  That is OK, but you will need some type of triangle template to ensure both ribs are the same.

In this case, as is most common, the tips are parallel to the aircraft centerline.  I use my old, rusty framing square to ensure the tips are sanded square to the wing.

The fuselage must be secured on a flat surface. The fuselage must be set on a flat surface large enough so the wing does not over-hang any edge.

Use weights or pin the fuselage to your building board.  The important thing is to ensure that the fuselage can not move.

Mount the wing and center it from side to side. Center the wing on the fuselage.  I usually measure each wing tip from the opposite fuselage side because it provides a convenient point to hold the tape measure.

You should be able to get all matching distances within 1/16" without difficulty.

The distance to the left wing tip. The measurement to the left wing tip.
The distance to the left wing tip should match the distance to the right wing tip. The measurement to the right wing tip.  Both tips are very slightly under 24-1/2" from the opposite fuselage side.
Measure from the tail post to each wing tip. Next, measure from the center of the tail-post to each wing tip.  If the distance is not the same to each wing tip, then you will have to adjust it and then go back and re-center the wing.

To clarify any time you move the wing you must check all measurements again.  It can get tedious, but if you built accurately in the first place then it shouldn't take more than two or three times to get the wing square.

The distance to the right wing tip from the tail post. The measurement to the right wing tip.
The distance to the left wing tip from the tail post must match the distance to the right wing tip. The measurement to the left wing tip.  Both measurements are 34-5/8".
When the wing is centered, lock it in place. Lock the wing in place on the fuselage when you are satisfied that the wing is square to it.  You can use pins, weight, clamps or anything that will prevent it from moving.

Use a soft pencil or fine-point marker to make alignment marks on the wing and fuselage.  You should make a minimum of three marks.

At this point you should check the wing incidence.  If it is correct then you can move along to the next step.  If not then make adjustments to the wing saddle until the incidence is correct.

Do not continue until you have done this because it is easiest to adjust before the leading edge dowels are in place.

Measure the height of both tips to ensure they are the same. Check the height of each wing tip.  Make adjustments to the wing saddle as necessary.  Sand the high saddle or shim the low saddle depending on whether the wing needs to be raised or lowered.  With each adjustment you should also check the incidence again.

Because you have to remove the wing, you will need to go back to the beginning and re-measure everything.  The alignment marks you made should position the wing very close when it is replaced, but check anyway.

Do not drill for wing dowels or hold-down bolts until you are absolutely satisfied the wing is mounted as straight as it can be.  If you do not take your time with this step your plane will never trim properly.

 
 

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Building Model Aircraft Wing Ailerons and Flaps
Mounting the Wing - Part 2

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Copyright 2003 Paul K. Johnson