Rear Wing Spar

Time: 4 Hours

Once I had the wings initially attached I set out to make their final adjustments. Even though the wings are securely attached at the main spar they still have a little bit of play since the rear spar is not drilled yet. This allows you to make adjustments before drilling and finalize their position. There are three adjustments that need to be done. First is the sweep forward and aft with regards to the wing tip and fuselage. To measure this you run four plum bobs along the wings. Then you run a taught string along the floor so that all four of the plum bob’s a line on that string. You can make adjustments forward and aft to get them to line up. The plans allow for up to 1/2″ in the difference. My wings were wishing 1/8″ and I tweeted them a little to tighten them up a little more.   

 The second measurement is to make the wings square with the fuselage. To do this you make a measurement from the tip of the leading edge on the vertical stabilizer to the seam on the wing top skins at the wing tip. Again you get a 1/2″ play in the two sides and I had less then a 1/16″. The final and most critical measurement is the angle of incidence. Every wing has some angle of attack built in to it with reference to a level fuselage. Van’s tells you that with a level fuselage you can run a level from the leading edge of the main spar flange to the aft edge of the rear spar flange and there should be exactly 2 51/64″ space between the aft end of the level and the wing skin. The easiest Way to do this is to make a spacer that you can place at the aft and underneath the level. My buddy Glenn had saved his spacer from his first airplane so I borrowed it to make my adjustments.  

  With the spacer and my 4 foot level and my digital level I worked my way along each wing at several different points checking the measurement. I had to make some small adjustments on both sides to get them just perfect.   

  

 With all three of those adjustments perfect I clamped the rears are in place. I then took the day off and came back at it the next day and re-did each of the measurements to doublecheck and triple check that they were perfect. After confirming that all the measurements remain the same I prepared to drill the rear spar to do this I used my drill cup and a #30 drill bit. The drill cup made sure that I drilled square to the surface. From there I stepped up using two readers and two drill bits to get the final size of 5/16″. 

   Now the wings are all set in their final position, hopefully the plane will fly straight and won’t have a heavy wing. Now that I have the wing secured in its position I can start to work on all the extra wing attach chores like rigging the ailerons, flaps and other items. 
  

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