24-02: Initial trim and drilling wingtips to wings

The initial trim

Chapter 24 starts with an initial trim of the flanges of the wing tip - they come way oversize and need a trimmed to be able to even start to try and fit the wingtips. I measured the available flange (it was a bit more than 1/2") and cut the flanges so they would not contact the rib. I did a rough cut of the wingtip at the trailing edge so it just cleared the aileron - i will do a proper trim once the wingtip is drilled to ensure a parallel gap to the aileron. 

The 'joggle' where the wingtip goes under the skin was fairly rounded. So i squared this off with a Permagrit sanding board, and marked the edge with a piece of tape to ensure the wingtip didn't get pushed too far in. 

Squaring off the joggle.

I found the best tool for cutting the fibreglass was a japanese pull saw. This thing is great - it leaves a 1/64" kerf, and does not create any dust - more like small chips. The Dremel tool seems to heat up the fibreglass and gives off a noxious smell. No good. 

Jig to mark the initial cut line

Using the Japanese pull saw.

Drilling the Wingtips

In March 2020, Van's changed the method for aligning the flaps and the ailerons. You no longer use the aileron jig that came with the kit (Page 23-10 of the plans). Now, you make sure the flaps are bumped up against the spar, then align the ailerons with these. You can see how initially did this, here. 

Basically, with the ailerons aligned in position i just needed to align the wingtips with the ailerons / flaps. Once i was able to get the wingtip in position on the end of the wing, i used a ratchet strap to ensure it pulled forward with the leading edge. I then ran a builders string all the way from the inboard edge of the flap to the outboard and of the wingtip. 

The trouble was, without the trailing edge rib installed in the wingtip, it would deform at the unsupported section aft of the wing skins and not align with the aileron very well. To counter this, i drew a line on the aileron at an arbitrary position on the top and bottom, and carried this over to the wingtip. This allowed me to measure the aileron thickness at this position, and once i had this measurement, install the trailing edge rib in position with tape, such that the thickness of the wingtip at this point matched the thickness of the aileron at the same point. 

I took this measurement...

And slid the trailing edge rib into place so the wingtip thickness matched. 

Once this was in place, i was able to re-install the wingtip using the ratchet strap, use the builders line to make sure it was all in place, HOLD MY BREATH, and match drill the wingtip to the holes in the wing skins. I drilled the lower 5 holes, and the aft most hole on the top and the bottom first. This held the wingtip in position. I was then able to remove the ratchet strap and drill the remaining holes. Due to both wings being on the wing stand, i needed to use my 90 degree drill for many of the holes. In the middle of the wingtip, i found the tip would collapse in on itself when drilling - so i used my go-pro suction mount to keep the skin flush with the skin. 

Aileron bellcrank was in the neutral position..

And the aileron crank at the wing-root was also at it's neutral measurement.

The ratchet strap held the wingtip in position. The tape shows where the edge of the 'joggle' was in the part - this was aligned initially with the wing skins.

I tied the builders string off to the lower bit of the wing, then tightly pulled it up over the corner of the flap - taping it in position.

It was run tight all the way to the wingtip and taped in place. 

Aligned at the flap root end

Aligned at the aileron / wingtip intersection.

Aligned at the flap / aileron intersection.

This was the other wing:

Flap inboard end

Flap / Aileron Intersection

Aileron / Wingtip Intersection

Once the wingtip was setup, i was able to match drill the holes from the wing skins to the wingtips. 

Initially 5 holes were drilled top and bottom at the leading edge, and one at the trailing edge then the ratchet strap could be removed (it got in the way of drilling the holes mid chord). 

My Go-Pro suction mount was used to keep the wingtip flush with the skin as i drilled.

I had to use my 90 degree drill in-between the wings (as they were on the stand). 

This initial drilling effectively sets the location of the wingtips and their alignment. It was an important step! Once this was done, i was then able to cleco the wingtip in position and mark and cut an even parallel 3/16" gap between the aileron and the wingtips. 

Very satisfying!