Upper Wing III

4/10/2007

Normally the trailing edge ends at that tail rib, but I unfortunately cut my trailing edge short! So I have trimmed it to end at the first main rib. To remedy this, I was going to span the remaining gap to the tail rib with spruce, and shape it to match. As luck would have it, I stumbled across a trailing edge drop-off in the parts-bin from when I built the lower wings last year :0) Amazingly I got this piece to line-up first time.

Foam

I clearcoated the inside area where the foam was to be placed. While the second coat was wet, I pushed in the foam blocks I had trimmed ready, the clearcoat acts as an adhesive for the foam. Over all of this will be Superfil instead of the usual fiberglass. I tried fiberglass matting on the lower wing tips and made a mess of it, the supefil is a reasonable alternative, maybe not as tough as FB, but when finished later with clearcoat, it's pretty tough.

All drag block holes were syringed and soaked with clearcoat using a pipe cleaner, reamed out, then the process repeated the next day. I die cut one end of each wire, placed in situ to mark off the other end then die cut it accordingly. Square 4130 .125 plate washers I had made were used instead of regular washers due to potential 'cupping' of the softer washers. In hindsight, the amount of torque applied to the wires i don't think warrants these robust washers. If I built another plane, I would simply double-up the regular washers.

Next, I marked out my trammel points at the compression rib stations, my trammel bar is advance technology: a length of 2x1 with nails in it ;-)

Drag / anti drag wires

First, I unclamped the wing from the jigs so the wing was 'free'. Working from inboard out, torqueing was done with a 'touchy feely' type of approach. I hand tightened the nuts with maximum effort, then used a wrench for about 3/4 to 1 full turn, this moves the trammel point a little. Then went to the opposite wire and did the same, trammeling again to move the trammel point back, at the same time tapping both the wires at the cross-over point with a kitchen fork in order to achieve the same audible pitch [equal tension is of course the objective].

Plastic tubing was then added as a friction/shim sleeve to the wires at the cross-over points, tied together with tie-wraps. I left the wing to sit overnight to 'settle' with these new pressures added to it, then trammeled again for good measure.