HP-24 Project

Update 10 September 2007: All over the place

Since the last Update I've been down to the annual Experimental Soaring Association's Western Workshop at Tehachapi, done a bit of climbing, rode the 1500-foot zipline at nearby Moaning Caverns, and got a lot of work done on the flaperon plugs of the left wing.

The ESA meet at Tehachapi was somewhat saddened by the recent passing of Paul MacCready. He was expected there, he'd RSVP'd before passing away in his sleep on 28 August.

However, the event was well attended, with standing-room-only for many presentations. For the first time in six years I didn't have a talk prepared. But it was fun to see all the sailplane development enthusiasts and see what they were up to. Greg Cole was there with what is probably the prettiest sailplane trailer ever built. And Danny Howell presented the latest LightHawk progress, including more info on the very much updated 18m wings.

Bruce Carmichael talked about the current state of suction boundary layer control, presenting a plausible argument that solar-powered suction would provide a greater performance enhancement than were the same energy applied directly to thrust through a motor and propeller. In a later conversation with Al Bowers I tried to sell a nano-pezio-solar panel that would turn solar power straight into diffusion of the boundary layer air across a semipermeable membrane. But he wasn't buying any snake oil that day.

After Saturday at Tehachapi I drove my rental sedan north to Merced where I stayed the night. The next morning I was up at 4:30 and headed to Tuolumne Meadows.

For the past few weeks I've been meeting with some climbing friends for what we call Wide Wednesday. That's where we practice climbing offwidth cracks - cracks that are too wide for conventional hand or fist jams, but too narrow for chimneying. Offwidths require strange and despair-inspiring configurations of hand stacking, knee bars, arm bars, chicken wings, and other tenuous modes of upward mobility.

So, Sunday I spent with climbers Ed Hartouni and Gary Carpenter trying out my untested offwidth skills at Olmstead Canyon, just west of the popular Olmstead Point vista. We started with a relatively conventional crack Ivory Tower Center, and then got down to the messy offwidths.

Gary led right up the route Enemy Within, protected by largish cams, the which Ed cleaned on the follow. Then I toproped it, constituting the most difficult pitch of climbing I have ever finished. Eventually I arrived at a configuration of right leg and shoulder in, right arm chicken-winged, and left foot pawing randonly at the rock. That seemed to yield ascent in sweaty, groveling, two-inch increments, the sum total of which got me to easier chimney and face climbing to the anchor.

After Enemy Within we took turns toproping the chossy, mossy chimney Talk Dirty To Me and the stem-to-roof-to-offwidth The Thrill is Gone. I managed the first route with fair ease in at least the chimney portion. The second stumped me just beyond the roof. After several falls I did manage an elegant knee bar at the roof, But upon getting plugged into the offwidth above I found myself outmatched fair and square by the right-side-in configuration demanded by the crack. I whimpered uncle and lowered off.

Monday was Alia's birthday, and what she wanted to do was ride the zipline and do the rappel at nearby Moaning Caverns. Which we set out to do, but were half shut down at the Caverns: she didn't meet the minimum weight requirement for the rappel. It takes a certain amount of mass to overcome the friction applied by the J-bar rappel devices used in caving rappels, and Alia just didn't have it. But she was fine for the zipline, so we just did that - one trip for me and two for Alia.

Tuesday morning 4 September I arrived at work to see on CNN that Steve Fossett was missing after taking off from Barron Hilton's Flying M ranch. I did call Major Ryan to see if I could help, but they already had all of the people and resources they needed.

As of this writing on 10 September, I have to say that it's not looking good for our International Man of Adventure. If the aircraft were on the ground intact I think it would have been found by now by the CAP searchers who have discovered at least six previously unknown aircraft crash sites.

I've done a fair bit of flying and driving out in that part of the country, including a retrieve out of Hilton Ranch, and I am too too aware what a geographical and topological puzzle that part of the country is. Also, having worked at small airports and having owned a tube-and-fabric Aeronca I have a fair idea how easy it is for something like a Decathalon to become an unrecognizable collection of semi-random shapes. It may already have become the sort of secret that the Nevada countryside guards jealously, and yields only to close inspection. Hopefully, the next few days will prove me wrong in this.

Anyhow, over the 8/9 September weekend at the shop we've taken a bit of a detour from where we were headed last. We were getting set up to make a set or two of horizontal stabilizer molds. But Brad Hill wants to get under way with the flaperon molds as soon as possible so that he can get them over with before the weather turns. So when I went to the shop on Saturday I immediately set about moving forward on the left flaperon plugs.

The biggest challenge of the weekend was probably the wing mold stack shuffle. The problem was that the wing molds were stacked four high, and that the lower left wing mold that I needed to work on was on the bottom of a stack that weighs right around 1200 pounds.

I started the shuffle by using my two stick hoists to raise the upper two molds, the ones for the right wing. Then I rolled the left wing molds laterally out from under the right molds. After that I attached wheels to the lower of the two right molds and then lowered the right molds onto the floor. I attached the stick hoists to the upper left mold and raised it high enough to clear the stack of right molds, and then carefully rolled the stick hoists laterally to position the upper left above the two rights. Then I did the rollover on the suspended mold and lowered it onto the top of the two rights. That gave me the lower left mold on its wheels on the floor. After rolling out of the storage bay and across into the work bay I was done. And right about then, Doug arrived and we got to work.

The real task for the day was to attach hinging gudgeons and radius blank strips to the flaperon areas we had previously liberated from the left wing plugs. After that, the next task would be to attach the flaperon plugs to the Radius Maximus machine so they pivot at the hinge gudgeons, and then mill the upper hinge radius into the blank strips. Then we can send them up to Brad for finishing.

By starting fairly early and keeping at it, we managed to do everything I'd hoped to accomplish for the weekend. So next weekend I should be able to chuck the flaperon plugs up on the radius machine and do the cutting that yields a nice narrow close-tolerance gap between the upper wing surface and the upper flap surface.

Here's the photos:

Here I am on 2 September belaying Ed Hartouni on the first climb of the day, Ivory Tower Center.

Here I'm in the squeeze crux on the mossy chimney Talk Dirty To Me.

And here I am trying to pull the crux of The Thrill is Gone. The idea is to undercling/layback this little roof, get a knee bar, and then squirm up into the offwidth. It took several falls, but I finally got up into the offwidth and realized I'd never done a right-side-in OW and had no muscle memory on which to operate. I lowered off from there.

Here's Alia geared up and ready to ride the zipline at Moaning Caverns. She wanted to do the rappel into the cavern as well, but didn't meet the minimum weight requirement.

Here she is just after launch. I'm on the parallel line.

And here she is in the trough at the end of the line. Heavier folks hammer right into the arresting rig and stop, while lighter ones tend to drift to a halt a little short. No problem, the recovery guy rigged to the line and hand-over-handed out to her and towed her in.

Here's Doug the morning of 8 September, marking and scribing the flaperon hinge line segments on the bottom left wing mold. Doug used regular old monofilament to find the line, and the scribed it into the mold in 4-foot segments using an old HP-18 flap skin as a straightedge.

Meanwhile I welded up another batch of flaperon plug gudgeons using little chunks of 1/2" mild steel tubing and 3/16" mild steel rod. The near tub contains the 20 odd gudgeons, the far tub contains the two alignment tools we use to place the gudgeons right on the hinge line on the mold.

Here's the left inboard flaperon plug section that we liberated from the wing plugs. We've smoothed up the cutoff edge and taped it in place on the wing mold.

And here it is chocked down to the mold with hot glue and bits of drip irrigation tubing and PVC foam.

Here I'm gluing in one of the gudgeons using 5-minute epoxy filled with flox (75%) and cabocil (25%). The alignment tool has 3/32" holes (hidden by my hands) that I sight through down to the line scribed on the mold. We have two tools, so we glued the sixteen gudgeons (eight per flaperon section) in in eight five-minute cycles.

Here's the inboard flaperon section with all eight of its gudgeons installed. Outboard, Doug is aligning the outboard flaperon section for similar treatment.

Here's the inboard flaperon section with the hinge radius blank temporarily attached with popsicle sticks and hot glue.

Here's the inboard end of the flaperon plug, where about 1" is missing. My solution was to use all the leftover 5-minute epoxy to mold the missing area from the bottom wing mold. It's a mess, but it will clean up fine.

The inboard flaperon plug, broken loose and flipped over. We've filled the gudgeon bores with clay (plumber's putty, actually) to mask it from the epoxy we use to permanently bond on the hinge radius blanks.

Meanwhile Doug gets to work chocking down the outboard flaperon plug.

And here it is with gudgeons inserted, hinge radius blanks glued on, and the whole thing broken loose and flipped over.

This closeup shows one of the outboard gudgeons, where the flaperon section starts getting awkwardly tiny. I had to bandsaw a recess in the radius blank for the gudgeon to allow the hinge feature that will secure the plug to Radius Maximus. Note the gudgeon bore filled with putty. I didn't do that for the right side flaperon plugs, and ended up spending about four hours making special tools and cleaning epoxy out of the gudgeons. Lesson learned and applied.

We've mixed up some filled epoxy (not the expensive 5-minute stuff) and troweled it into the notch between the foam core of the flaperon plug and the radius blank on both flaperon sections.

A closeup of the fill near one of the outboard gudegons.

Here's that pesky inboard end again. A mess, but one that will yield enough guidance contour to work with.

Homebuilt aviation is not for folks who don't try things at home.

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page updated 10 September 2007 all text and graphics copyright (c) 2007 HP Aircraft, LLC