Jigging and Dry Fitting a Model Aircraft Wing

The first spar laid on the board will determine how straight the wing is.  If the spar is wavy, so will be the wing and it can not be corrected.   Be sure you understand that.  Getting this one piece properly aligned will go a long way toward keeping the wing straight.

If this part is not straight then you can sand the leading edge and trailing edge straight, but the airfoil will also be wavy and the sheeting is not going to be thick enough to allow you to sand the wing to a uniform shape across the span.

I lay a straightedge on the board and then push the spar up against it.  Pin the spar in place and then remove the straight edge.  If you use magnets then hold the magnets that are already in place so they can not shift and put magnets on the side where the straightedge was.

This is a very important step.  Do not rely on the plans to be straight because they probably are not.  Paper shrinks, expands and warps due to humidity.

This step was 4 minutes.

Before gluing anything, I make sure everything fits.  All the ribs, shear webs and both spars are put in place.  This photo was taken before adding the upper spar.

Now you can see why I say the Great Planes building board does not come with enough magnets for real world use.  I bought a second pack of magnets as well as magnets from various other sources.  Details here

Ideally I would like four magnets on every rib to hold it perpendicular (vertically) to the board and perpendicular (fore/aft) to the spar.

Notice that the upper spar does not fully seat into the rib notch.  The top of the spar should be flush with the ribs when properly seated.  This problem is due to the webs being slightly too tall.

Trim the webs so that the spar fully seats but still makes contact with the webs.

The above step and trimming the webs took 11 minutes.

Elapsed time 15 minutes

Drilling the holes should have been done during parts fabrication so I am not counting this time as part of the build time.  If you care it was about 5 minutes.

Note that the ribs on each side of center will sit directly on the wing saddle.  In this case the outside measurement between these ribs is 3-1/2".  That means the fuselage will be 3-1/2" wide at the saddle.  This is an important measurement so I wrote it down.  Remember, I am building without plans.

The same straightedge will weight down the aft end of the ribs during construction to prevent warps as shown here.  Alternatively, the ribs could be pinned to the stick.  Be careful not to move the ribs out of position when setting the weight in place or pinning the ribs.

This step took 3 minutes

Elapsed time 18 minutes

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