Doug and Brad came out to the shop for Akaflieg Douglas Flat XI. This Akaflieg was originally scheduled for 5 through 12 December with half-days on the 4th and the 13th. But a big storm struck us on Monday 7 December, the power went out, and we did no work that day. The weather was bad again on the 13th and I could not get to the shop, so we cancelled the last half-day and met at Starbucks for a debriefing and then sent the guys on their way.
On 26 November 2009, a photo of a static test rig to test our method of anchoring the lift pins in the wing root ribs. The piece in the middle represents the root rib and lift pin, the pieces above and below are for anchoring the test article in the Break-o-tron. I purposely made the test article rather casually to make it representative of the worst possible construction quality.
The assembled test article, ready for stressage.
A couple days later on 29 November, tuning up the shop heater. This Hot Dawg had been intermittently coding an Error 6 and going into system lockout mode. Running it through its paces showed that the lower tubes weren't lighting, which was being detected by the three status thermocouples wired in series to detect upper tube ignition, lower tube ignition, and central heat. When the lower tubes failed to light, the control module would do three retries and then go into lockout. The problem turned out to be dust in the flame transfer passages that propagate the flame from the top tube (where the ignitor is) to the lower two tubes. A few blasts of compressed air blew the dust out, and it returned to flawless performance.
On 5 December we tested the lift pin mockup to destruction. I had earlier stressed it to 2500 and then 3000 lbs force. This time I stressed it to 5000 lbs, which it held for about 20 seconds before letting go with a bang. That is equivalent to all of the lift of the wings being applied to either the forward or aft lift pins at about 17g.
Later that day we demolded the lower left wing skin and trimmed the flaperon cove edge. We also weighed it. Here's the inner surface
And here's the outer surface.
We also placed the lower skin onto the upper skin still in the mold, and also placed the root ribs in position.
I needed to center-drill a bunch of little pieces of nylon, and this rig turned out to be the most effective way of doing it with the tools at hand. It represents one of my favorite lines from the movie "Galaxy Quest."
On 6 December, we laid up two of the rather complicated lower flaperon skins. On 7 December it snowed, hard. We managed to get up to the Arnold shop, but the power was out. We bagged the day. On 8 December, we laid up two more lower flaperon skins. 9 December, we laid up all four of the less complicated upper flaperon skins. One of them had a leak in the bag, but instead of trying to find and fix the leak I just double-bagged it.
On 10 December, we demolded one of the lower inboard flaperon skins and weighed it. It clocked in at around 2.5 lbs complete with all eight hinge pintles. Later that day we moved the upper left wing mold into the heated shop and bonded the drag spar into the upper left skin.
On 11 December we removed the spiders that located the drag spar and admired it. Here the lower flaperon skins are also set into place for reference.
Later that day the guys did some minor patching of the lower flaperon skins and started laying up two new root ribs for the left wing.
Late on 11 December, we moved the right wing mold into the heated shop next to the left one, and bonded its drag spar into place.
On 12 December, I had Raen at the shop for the day. Here she is demolding a new batch of flaperon pintles.
Later, we bonded the drag spar into the right wing and then used the spiders as supports while we demolded the patched flaperon skins.
After that, I fitted and bonded in the airbrake box ends for the left wing. The ping stuff is bits of PVC foam that I used to chock the box end into place while bonding it.
Homebuilt aviation is not for folks who don't try things at home.
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page updated 15 December 2009 all text and graphics copyright (c) 2009 HP Aircraft,
page updated 15 December 2009 all text and graphics copyright (c) 2009 HP Aircraft, LLC