Friday, July 31st, 2015 at 11:19 am - Hang-glide
This blog has as many gaps as my logbooks which are sitting on the to-do section of my desk waiting for their pages to be filled with flights and caving trips done many moons ago.
After expo my passenger and I drove back to his house in Bristol. I continued onwards the next day through horrendous rain showers to a campsite behind the Long Mynd for the third and final BOS hang-gliding competition of the season.
Here’s a picture on take-off on the Long Mynd in special smudged-lens-o-vision:
Tuesday, July 21st, 2015 at 8:36 pm - Cave
Top camp was still relatively empty before the hoards arrived for the third week expo. Two young ULSA (University of Leeds Speleological Association) cavers fresh from their bus trip from Leeds showed up and were easily persuaded to walk up the hill at 6am. We got there in time for Rachel to organize us into three teams and go do Balconyhohle into the area known as the Leeds Bypass. (Leeds people are gradually taking over this expedition in name and numbers.)
The team comprised of David, George and myself. Frank had found a new hole in the floor the day before and persuaded David to check it out. George and I went for a poke in the western extents in the direction of the Tunnocks cave (to which this one has not been connected yet).
On the walk back, I said to George, “You know that thin gap we saw in the ceiling back there? Do you want a leg up?”
“Sure,” said George.
He found a moderately large unexplored chamber up there. I didn’t believe him because there was no echo, but I had to squeeze through anyway to check it out.
We went back to fetch David who had so far only managed to push a big slab of rock over so it filled in Frank’s hole. He didn’t take any persuading to give up. We traipsed back to the drafting ceiling slot (tagged as “Question Mark 90b” in the database), pushed all our kit bags through, drills, tacklesacks of rope and ourselves, and began exploring and surveying it. Down one end there was a perfectly preserved dead bat spread out on the floor complete with wings and fur. David began drilling for bolts and putting in rope to get down the hole opposite to access the next level below.
We ran out of time and came back the next day.
Partway through the trip I finally got suspicious at how quickly George had been taking notes.
“Oh, I didn’t know you were supposed to draw a map. I’ve only been writing the numbers.”
David’s rigging had by then lead us down a rope and onto traverse line along a loose ledge above a bottomless pit to a proper passage.
I lay down for a nap while David sorted out some of the missing surveys. I planned to bodge out a map of the chamber above.
We carried on while David looked down the far end where there was a sandy slope with rocks embedded in the crest. He pushed one of them forward and it slid round the corner and carried on down. Back in the main passage with the high domed ceiling, George and I thought the world had ended with the entire cave imploding like a pile of boulders in a blender. I went rigid, unable to see any solid looking rock shelter nearby that I thought wastn’t going to burst into an avalanche.
When the noise subsided, David didn’t know what we were yelling at him about, so we stood him exactly where we had been and then went and pushed one of the other boulders off the slope so that he too could experience the amazing sound explosion.
As we were derigging the rope, a couple of other cavers were struggling through the crack to inspect our discoveries. “Go up in that direction,” I said. “There’s a perfectly preserved bat on the rock.”
Luke said, “What bat?”
I led him over and showed him where it was, now trodden on by a boot so that bits of wing and tail were spread over a wide area.
It was time to go out.
I came down the hill in the morning and typed in the survey data. It definitely doesn’t look right. There’s one huge rift passage which claims to coincide with an already known small passage. What a mess.
Last week I did quick day trip to Greifenburg to take advantage of a weather window and a chance to do the “best canyon in Austria” with a couple of spare cavers who were festering in expo base camp. My tent spot hadn’t been filled since I abandoned it three days earlier, so I left the cavers Frank and Dave to pitch up while I waited for the taxi to carry my glider up the hill. It turned out I’d just missed the 9:30am rush to the bus, so we ended up driving my car up with David’s mountain bike for a pack lunch in the shade of my wing and a lazy start.
And so it was straight off for a fly at 1pm with low cloudbase and strong lift to 2400m. I had my radio tuned to the channel of my german friends. They couldn’t hear a word I said, but I could hear everything from them, which wasn’t very useful as I don’t know any german.
Monday, July 13th, 2015 at 7:05 pm - Machining
Just how bad are these minimization algorithms
I’ve been caught short trusting these classical numerical recipes, packaged up in scipy.optimize.minimize and failing to get an adequate result in the case of the triangular machine tool calibration and its nine unknowns.
So here’s a simple example for finding the circumcircle radius of a triangle whose sides have lengths a, b, c.
Monday, July 13th, 2015 at 8:34 am - Hang-glide
I didn’t get very far up the Drau valley from Greifenburg, but the flight was sooo satisfying.
Anna Schutz is a bitch, if her Haus is anything to go by.
That’s the strange name for the sharp ridge on the north of Lienz marking the turning point where you can go around Kreuzeck range. It was my self-set task for the day because it’s described in a bit of detail in the Burkhard Martens Cross-Country Flying book.
Picture 8.5.17 Flanks over the Anna-Schutz house. A racetrack up high and a dangerous lee down below.
After a very difficult start of flight trying to get up from deep in the ravine between Emberger Alm and Gaugen, and then scoring 3000m altitude to get that hunger out of my system, I headed over to the red cliffs of Scharnik.
Here I had the usual nightmare with the rigid wing Atos gliders, who are always above you like mosquitoes because they glide more efficiently. However, they don’t thermal so well in turbulent air when a normal hang-glider can make progress by really throwing it around in the air currents, and inevitably you come face to face with them on the level. They think they own the thermal because they started out above you. And they fly differently so you can’t circle with them. And if your glider is easily recognizable like mine, they can give you a bollocking in the landing field as you’re derigging. They all look the same to me, these Atos gliders, so I have no idea when that was. It could have been two days before.
I do always keep out of their way, to the extent of making bad decisions and losing thermals. So I followed the back ridge from Scharnik to Damerkopf, lost all my height, went back to the rocks at Scharnik and did it all again this time without the distraction of the other glider threatening to bite me. I then crossed directly to Damerkopf, hopped over onto Anna-Schutz’s spine-back house perfectly lined up to take advantage of the thermal highway as advertized.
Far below on the southern flanks I could see gliders returning low from a competition task and having a hard time staying up. I’m glad I’m not down there, I thought to myself.
Five minutes later I was down there where it was as rough as a pair of long-johns flapping in a sea breeze. You couldn’t see anywhere to land except for a few green cornfields far in the distant valley that probably had three rows of power lines through them, so it was best not to bail out. Sometimes your shadow was so close you could almost touch it. Then you’d have a heart attack when you saw another shadow coming directly at it and you’d have to rapidly dart your head about like a chicken’s to see where the other glider was camouflaged against the boulders and scree.
Thursday, July 9th, 2015 at 1:45 pm - Machining
Little to report from Austria. Shoddy internet over the road that cuts out after 2 minutes. Eight minute flight straight down (with cavers watching, wondering what’s the point). Days of rain when I worked on my electronic logging devices, all of which were broken in various ways, from short circuits (caught in time before the Teensy boiled its plastic off), broken I2C connections, a completely bricked BNO055 orientation sensor, and a slightly folded micro-USB card probably from when I accidentally drop-kicked the device on my way out the door which was causing of the short circuit. I debugged for six straight hours like a machine, and still it wasn’t enough.
There’s something making the microcontroller crash after eight minutes whenever the Serial1 connection to the GPS is opened, but it doesn’t happen when you run a program that just listens to the GPS only.
I’ve also done two carries up to top camp of rope and metalwork and my soles are now sore. Now I’m worried that I’m coming down with the lurgi just before I strike camp and head for better air at Greifenburg.
I think I’d better go jump in the river to chill everything out while it’s still hot.
Wednesday, July 1st, 2015 at 5:17 pm - Machining
Over the last few months, well, since December, I’ve been producing an awful lot of plastic scrap from the UP! 3d printer we have here.
We had better find a way of recycling this soon. I’ve got my eye on the plastic injection moulding machine as a potential consumer.
Here’s the work bench of chaotic iterations of circuitry and boxes to contain the circuits.
To be clear, none of it does anything, except get data and log data to an SD card.
Occasionally it gets a short-circuit which crashes the microcontroller.
I now have two data logging devices. I am busy printing off further legs and hooks to glue onto the second black one on the right so it can be strapped onto another hang-glider, or to my hang-glider beside the primary device, which will mean that I have two sensor boxes measuring the same factors and coming up with wildly different results, thus proving that this kit isn’t as great as it appears.
Building stuff is a great way of putting off actually doing anything with the data. But once I am in Austria in a campsitte and away from DoESLiverpool and its tempting 3D printers, I won’t have the option to put it off anymore.
Wednesday, July 1st, 2015 at 3:26 pm - Hang-glide
Last Saturday we skipped MakeFest in the Liverpool Central Library to take advantage of some sunny weather.
I had a nice flight off the Long Mynd, caught one thermal up off the hill, and then drifted over the back and totally lost my sense of direction on the way down, blundered through one thermal on Wenlock Edge and was quickly down in a grassy field as I deserved to be.
I walked most of the way back to Church Stretton by the time Becka arrived with the van after her midday cycle ride up and down the Mynd holding up all the cars. We set up in the camp-site nearest to my landing field, had a late lunch, and then pushed off onto a bridleway along the top of the Edge which quickly degenerated into a tree-rooty footpath through a series of wheat fields.
When we eventually got back onto the tarmac, Becka sped off downhill along the country lanes until she came unstuck at a T-junction with a lot of loose chippings at the centre.
This is day 3 of the recovery period.
No caving for you!
Friday, June 26th, 2015 at 12:59 pm - Kayak Dive
I took a break from my treadmill of unpaid unproductive work for a day on Cosmo’s boat with a couple of dives with Becka. We left the slip at 7am, having forgotten to have my morning tea. I wondered if my addiction was the cause of the headache most of the afternoon.
Aside from that, it was very calm out there.
We dived on the wreck of the Alarm (a light ship), which was pretty deep at 30metres, but clear enough to see and swim round.
There was a bit of a drama with the SMB reel which stops paying out if you squeeze the trigger too hard, doesn’t it?
Becka’s suit flooded completely. Luckily the water was 12degreesC, so it was like being in a cave. We pressure-tested it after the second dive with soapy water and only just detected the problem on the neck seal which had peeled off at the front and remained joined by a thick film of glue.
The second dive was on the Lelia in stirred up clouds of terrible visibility. (Here is a video from last time when it was clearer, which was also the last time I bothered taking a still-shot camera underwater.) Headcam video does the necessary job of aiding my memories.
We got off the wreck as soon as we’d dealt with the anchor, not wanting any repeat of our getting trapped inside experience from our last trip out (which, fortunately, was not our last and final trip).
Thursday, June 18th, 2015 at 9:31 am - Hang-glide
Here’s one of those great two-hour go-nowhere flights I keep having in places like Llangollen on the days when people with some actual talent were scoring hundreds of miles.
The GPS gives a direction and velocity in degrees along with the position. If we calculate the average velocity observed in each degree of the compass, like so:
degreesums = [ [0, 0.0] for i in range(360)] for degree, velocity in gpsvelocities: if velocity > 1.5: ideg = int(degree + 0.5) degreesums[ideg] += 1 degreesums[ideg] += v degreehistogram = [ sumv/max(n,1) for n, sumv in degreesums ]
… and graph it radially as the set of points
pts = [ (sin(radians(d))*r, cos(radians(d))*r) for d, r in enumerate(degreehistogram) ]
you get the yellow circle which is offset from the centrepoint origin by the wind speed.
In this case, the deflection (wind vector) was has an inverse bearing of 322 degrees at 4.7m/s. The radius of the circle is 12.15m/s, which I guess is the average velocity of the hang-glider if you take away the wind.
To fit a circle (in cyan) to a series of points, I rely on scipy.optimize.minimize using the centrepoint as the parameter vector and the minimization function as the standard deviation of the distances of all the points from that parameter vector.