wing spar work continues

Good hours spent in the shop while I pondered how it could already be 19 years since that tragic September morning.  I'm so happy we have the freedom to chase our passions.

Finished up the spar root and front upper strut fittings.    Did the rough cutting on the band-saw to approximate shapes (the card stock templates shown in the middle were made early on this process in FreeCAD software):

Two spar root fittings after cleanup on the grinder and rough hand sanding.  Final fine sand will be completed just before primer and rivets as I still need to fit them to the spar and drill the attach bolt holes.

Laid out the location of the wing attach bolt holes.  It's important to be consistent here.  Length of the wings from where they each attach at the cabin frame must be equal for rigging purposes when the wings are installed.  The circled crosshair point is the centre of the bolt hole.  My holes will be round, not sketchy round like the marker shows!

Right wing spar in the upright position.  I clamped the spar attach fitting to the spar cap in the correct location ensuring the bottom lines up exactly flat with the lower spar cap and sticks out the appropriate distance from the root end of the spar as per the plans.  I used a flat piece of tool steel to do this, the plywood of the table top isn't a reliable flat reference.

​I laid the spar down and back drilled through the spar cap using a block of wood as a backer up to A3.  The rivet spacing here is 20 pitch eventually up to A5 size:

Up sized the holes to A4, then removed the spar attach fitting for matching up with the one for the left wing spar:

My original plan was to stack one on top of the other and back drill through the top one into the other, but I figured the most critical dimension was the bolt holes.  If the attach fitting to spar holes aren't exactly the same that doesn't matter as much as the bolt holes being equal.

Stacked the attach brackets on top of each other and pilot drilled the bolt hole location throught the top one and just starting into the lower one.  Attempting to drill through both by hand can lead to out of round holes or slippage despite the clamp used to hold it down.

​Then I used the drill press to final hole size each of them to AN7 which is 7/16 inches (I confirmed this in the plans and on the cabin frame attachment points to be sure). I also drilled out the A3 and A4 size holes required in the right attach bracket (not shown in this picture, but you can see them in subsequent photos at each end of the 20mm rivet pitch lines)

Next step was to start the left wing spar, following the same procedure that worked so well on the right wing spar.

With the spar caps and stiffeners added to the second spar, I wanted to figure out a way to make the spar tips exactly the same, i.e. both wings from root to tip exact same length.

It started by using a scrap of angle as a base line zero measurement point at the root end.

Placing the spars back to back (or spar top cap to spar top cap actually) I clamped them together in parallel at the root end and at the spar web outboard end.  I confirmed the spar webs and caps are equal length.

With the right spar as the guide or "master" I added the matching left spar tip and clamped it in place.  Essentially the left spar is now a mirror copy of the right.

Finger clamp at the far most tip end keeps things exactly where they need to be.

The left wing tip is pilot drilled to A3 to match the right.  Final measurement confirms both wings are exactly the correct length as per the plans.  Very happy.

With length confirmed correct, I fabricated the root doubler for the left spar.  Here it is clamped in place for fit prior to match drilling and having the flange trimmed.  It was easier to make the bend and trim it than guess at the width of the flange.  Think smarter not harder my grampa used to say!

Flange trimmed and spar laid down again for layout of doubler rivet holes.  Still need to trim the upper spar cap to match the taper of the spar web and doubler.

With the doubler in place and complete, it was time to compare the attach brackets again and confirm the bolt holes will have the same extension from the spar root.  Lining the second (left) bracket up against the first (right bracker) while it is attached to the right spar and using a square confirms they are the same.  Measuring the extension on the first (right side) confirms 39mm from spar root edge to the outisde of the bolt hole.

Using the same measuring points, I clamped the left attach bracket to the left lower spar cap and pilot drilled exactly matching the rivet spacing of the right wing.  Double checking the bolt hole distance I confirmed both bolt holes are exactly same on both spars, meaning they are true mirror copies of each other for length.  More happiness!

The twin spars lined up bottom to bottom.  Very happy how these are so far, but I have a bunch still to do for these to be a complete assembly for the wing.  Still need to trim the upper spar cap to match the taper too. 

Next up, cutting and forming the 063 web doubler plates, adding the front upper strut angles and fittings.  After that cutting the lightening holes and flanging them (that should be "fun").  Then it all comes apart again for debur, prime and re-assembly prior to final driven rivets.

Onwards!  Thanks for following along :)