Placement Of The Wing Ribs


After installing the Inboard & Outboard ribs and sheeting at both ends of the wing, we move to the placement, attachment and fabric rivit hole drilling of the main wing ribs. Similar steps will be followed when we do the left wing.

The wing construction section will be broken into three (3) parts and web pages as follows.

  1. Inboard Wing Construction
  2. Outboard Wing Construction
  3. Placement Of The Wing Ribs

Drilling Fabric Holes In The Ribs
Two methods of drilling the wing ribs for the rivets will be covered here: Type 1: Before attaching the ribs to the wing. Type 2: After attaching the ribs to the wing.


Click to Enlarge
         

Type #1: Before attaching the ribs to the wing. Starting from the rear, space the rivet holes about 4" apart, stopping about 4" before the top of the rib at the high point of the curve. The fabric rivets are only used in the "flat" area between the top of the rib curve and the trailing edge of the wing. Shrinking the fabric will hold it down into tight little valleys along the front section, up to the top of the curve, and even a short distance behind the top of the curve.

         
Click to Enlarge



Click to Enlarge
         

Type #2: After attaching the ribs to the wing. Make a drill jig using a "V" angle iron or half inch by half inch steel angle iron. Measure the length desired for your drill jig for placement of about fourteen, 1/8" drill holes, spaced 4" apart. Once you have the jig finished and drilled, you just place and clamp the jig onto each rib and, using your pre-drilled guide holes in the jig, drill through the top of your ribs, then move the jig to the next rib and repeat this process. This will give a precise and constant drilling for each and every rib.

         
Click to Enlarge

The rib jig is fashioned out of half-inch by half-inch steel angle iron as our builder has pictured. The pilot holes are usually drilled in the middle of one of the flat sides of the angle iron and used as a reference to level the angle iron on the rib.



Attaching The Ribs To The Wing Spars
It is very important to measure or lay out the locations of the ribs on the spars and mark those spots with a fine line ink marker. Make sure that the ribs don't interfere with either a cross tube bracket or with the bracket plates that the lift struts attach to. Don't allow a rib to sit on a rear lift strut bracket. The front brackets are no problem since they install straight up and down and are out of the way. However, the rear brackets install at an angle and the inside one can interfere with a rib if you aren't careful about placement. Just mark the locations on the spars in advance and then lay a rib in that spot to see if it interferes with anything on the spar. A variation of an inch or two will not hurt anything. Be sure to complete the leading edge rib placement first, then refer to the "Aligning Ribs For Straightness & Riveting" section (below) before starting on the trailing edge rib placement.


Click to Enlarge
         

The rounding of the gusset bracket edges is not necessary. The builder just wanted to make sure the edges were not sharp nor causing a sharp rise in the fabric once the wing was covered.



Click to Enlarge
         

Place your first rib onto the wing spar's at the marked location. Using a gusset bracket as a jig, mark the location of the lower rib rivet hole.

         
Click to Enlarge



Click to Enlarge
         

Using a center punch, place a dimple in the rib for the rivet hole location, then drill through the rib and spar.

         
Click to Enlarge



Click to Enlarge
         

Once the first hole has been drilled, place a Cleco fastener through the gusset bracket, rib, and spar to hold the gusset in place. Then mark and drill the upper rivet hole in the rib and insert another Cleco fastener in this new hole.

         
Click to Enlarge



Click to Enlarge
         

With the two Cleco's in place, mark and drill the remaining rivet holes in the rib and spar. Place Cleco's in the new holes to verify correct drilling and placement.

         
Click to Enlarge



Click to Enlarge
         

If this has been done correctly, remove the Cleco fasteners and place your rivets through the gusset bracket, rib, and spar then secure the rivets. This completes the indivdual attachment of one end of the rib to the wing spar. Just follow these steps for the remaining rib attachments on the rest of the wing.



Aligning Ribs For Straightness & Riveting

Click to Enlarge
         

When you have completed the leading edge, secure a piece of string across the rib apex (top of the curve) from the inboard to the outboard boxes. Now you can position each rib so that the apex of each one just rests below the string. This is done by slightly moving the rib's free end fore or aft so that the apex rests just below the string. Clamp and drill as with the leading edge.

         
Click to Enlarge



Click to Enlarge
         

It is also recommended you use a 90 angle square to check for straightness after you have completed rib placement at the leading and trailing edges of the wing. A slight straightening may be required at this time.

You have just completed the wing rib installation of the right wing and can now move onto the left wing where this process will be repeated.

         
Click to Enlarge