Freesteel Blog » Weekends

Sunday, June 25th, 2017 at 8:16 pm - - Hang-glide

It’s been the fourth day of hang-gliding in a row and the first of the competition. My god today was something. The comp is at Monte Cucco, and the drill is you drive up the hill and get set a task in the form of a series of GPS coordinates with cylinder radii around them, and your job is to race from one to another and tag each one. Your track log verifies your score.

This is quite different from free flying, because you are forced to go to places you wouldn’t naturally go to if you were following the air — and get back from them.

Here is what the course looked like against the terrain map:

flightmap

This leaves out all the forests, cliffs, canyons, sprawling suburbs at the base of the mountains and power lines. The beginning of the journey was absolutely terrifying because any escape routes to lower ground were into wind and unlandable. You had to learn to trust the ridge lift.

I didn’t trust it, and instead spent the first 30 minutes wheeling around these scary wind turbines on take off unable to find a satisfactory way on.

windmills

Then the clouds really began suck and I raced back north to the second turn-point. The third point was the landing field. There was such an uprushing of air in the valley I could not get down. Well I did eventually, by pulling all sorts of stunts (tight circles) that are the exact opposite of efficient gliding. Then, when I gave it a rest for too long, the air sucked me right back up again.

Hang-gliding is a sport for turning long pieces of aluminium into short pieces of aluminium. That happened yesterday when I broke an upright. I have no more spares. Today I got away with skinning my knees (I’m wearing trousers from now on). Clearly I do not deserve to fly this higher performance glider (a Wills Wing U2) since landing is the compulsory part of every flight.

It’s 9pm now. I’m finding I don’t really give a damn about anything else, eg reading and answering emails, or thinking about work. It’s too hot here even if I wasn’t flying.

Bed time.

Monday, June 5th, 2017 at 11:52 am - - Hang-glide

Some friendly competition in Derbyshire between hangies and paragliders on Saturday meant I got to witness the scale, organization and infrastructure of the paragliders — which included following me on xcrt.aero and being at the nearest road before I’d even had time to pick myself off the ground.

Then I was in the car for an hour as they drove madly up and down the M1 taking wrong turnings in an effort to collect three other paragliders strewn in the area.

Motto: write the logbook on the day and edit the video as quick as possible without wasting too much time.

My flight datalogger failed to record anything, so I can’t see if my thermal detector collected any signals.

Not that I had any spare brain capacity. For two hours I was continually trying to visualize and feel the structure of the air convection wafts while making constant adjustments to my circling.

I’m also learning how to stay in very weak air where you are gradually losing height — but at a slower rate than if you were on a desperate glide to nowhere — which moves you forward in time for something else to develop. It’s like skipping a turn in a card game.

Here’s a screen-grab of the livetrack24 view of my flight, which receives updates from an app running on your mobile phone.

livetrack

This is not to be confused with the latest AirWhere technology thing, also done by the paragliders recently which create an ad-hoc Lorawan network among themselves that displays their distance and climb rates of your neighbours on the network.

A small amount of additional calculation and they’ll be able to circle the ones who are in thermals you should fly to and join. This helps people haven’t learnt how to judge distances, times and glide angles.

I just cannot keep up with the tech.

Here’s some plots that I did salvage the data.

flightterrain

flightterrainside

Friday, June 2nd, 2017 at 3:32 pm - - Hang-glide

This is the follow-on of my Loser Plateau article of last year in Skywings magazine.

4 page PDF version

I should find something new to write about next time. Now that I am flying my BWG (Boring White Glider), which is a more advanced U2 I got second hand off Tim who no longer needs it because he’s got a whole hang-glider factory. Helen the bright orange HSMWorks glider is a Sport2, and I’m not ready to let go of her yet.

swp1

swp2

swp3

swp4

Thursday, June 1st, 2017 at 4:06 pm - - Flightlogger, Hang-glide

I’ve been flying around my data logger on my hang-glider and doing my own data processing with mixed results for two years now.

During this time I’ve been on the lookout for someone else’s work that I can copy.

Just yesterday I discovered the existence of Dropsondes and then Radiosondes (devices that get lifted by a weather balloon with a radio link; nothing to do with sound-waves).

The fact of their existence has been staring me in the face for years.

raspsoundings

Those little red *S* symbols in the rasp forecast are not weather symbols for sunshine, but in fact the locations of half a dozen atmospheric “sounding” stations.

Until now I’d believed they were something involving a fancy radar beams shining up through the clouds, but it turns out it’s a freaking weather balloon with a humidity, temperature and gps sensors (they don’t bother with the barometer anymore and just use the gps altitude) that radio back data for an hour and a half till the latex balloon bursts at 25,000m and the device falls under a biodegradable parachute with a 95% of never being seen again.

The US government has a complete tour of the procedure, but the MetOffice has some automated stations which assemble and let off a new balloon every 12 hours from a robot building.
(more…)

Tuesday, May 30th, 2017 at 6:11 pm - - Flightlogger, Hang-glide

First, here’s a picture of me and my cheezy grin high up in wave over Wether Fell with about a dozen other gliders last Sunday

wavegrin

I was able to generate my incomplete Tephigram as before to illustrate the warm dry air encountered way up there.

tephi

Unfortunately, the fancy Python tephigram software released by the MetOffice doesn’t work for me as it’s designed to plot graphs that go ten times higher in the atmosphere.

Tephigram is short for “Temperature” and “Entropy/phi” plot and was invented in 1915. I don’t understand all of it yet. But this science goes back a long way.

(more…)

Monday, May 8th, 2017 at 6:49 pm - - Flightlogger, Hang-glide

I’m getting tired of having “learning experiences” when I really want more “fun experiences”. But in the meantime, here goes.

On 2017-04-29 I was at the hang-gliding competition on Camlo hill in Wales, where I didn’t take any thermals over the back — like the folks who knew what they were doing — and I landed back on the top with nil points and little satisfaction.

For this learning experience, I downloaded the tracklog of one of the guys who did make it and snipped out the first 12kms of flight, like so:

darrentrack12

Direction of flight north is to the right (start of flight bottom left near (0,0)), the coordinates are in metres.

Having convinced myself I can extract the SRTM3 terrain, this is the graph of the flight altitude from the hill for those 12km against the terrain altitude:

darrentrackalt

Or you can plot the actual height above ground by subtracting the two:

darrentrackaltg

This looks like he was circling with a pretty consistent height of 350m as the air mass was carried up and down over the terrain, in a “bubble” of rising air.

Except there is no way this could be a bubble, because even if the bubble extended all the way to the ground 350m below, it would have certainly been been expended in less than 6 minutes at a rate of 1 metre per second to support an efficiently flying glider.

After 25 minutes of existence, we can rule out that it has anything to do with any packets of warmed air which may have risen from the ground 12kms to the south.

“Ah,” the usual response goes, “the glider was flying in a chain of thermic bubbles along the track of the flight, each one rising up just in time to pick up from where the last left off.”

This explanation is bogus. I don’t seem to pick up thermic bubbles that easily along my track, while the pilot that stayed with the thermal reported a continuously existing atmospheric formation which strengthened and subsided, but was always there.

I also don’t buy the idea that this structure is somehow kicking off thermic bubbles on the ground 350m below at least five minutes downwind of its track in time to reach his altitude.

No, this must be a self-contained, self-sustaining convection structure that may have been initiated by a thermic bubble, but which has clearly morphed into something altogether different.

(more…)

Friday, March 3rd, 2017 at 11:04 am - - Flightlogger, Hang-glide, Uncategorized

To be clear, I haven’t got mathematical proofs here (I don’t have the time), but the experimental evidence is quick to get.

Take the differential barometer sensor (used to measure airspeed) of the hang-glider flight logger. The Arduino code which updates the reading every 200ms looks like this:

long lastpx4timestamp; 
void Flylogger::FetchPX4pitot()
{
    long mstamp = millis(); 
    if (mstamp >= lastpx4timestamp + 200) {
        px4pitot->readpitot(); 
        sdlogger->logpitot(px4timestampset, px4pitot-rawpressure, px4pitot->rawtemp); 
        lastpx4timestamp = mstamp; 
    }
}

Why did I choose 200 milliseconds? It sounded like a good number to read it at. This is a quick way to program it to be a regular reading.

A better way is to actually synchronize it with the clock divided rather than simply add 200ms to the next time, like so:

int mstampdivider = 20; 
int prevmstampdivided = 0; 
void loop()
{
    long mstampdivided = millis()/mstampdivider; 
    if (mstampdivided != prevmstampdivided) {
        prevmstampdivided = mstampdivided; 
        P(micros());  P(" ");  P(singlereading());  P("\n"); 
    }
}

Now that code reads at 20ms rather than 200ms, but it prints a load of output which I can cut and paste into a file and read into pandas, like so:

rows = [ (int(s[0]), int(s[1]))  for s in (ln.split()  for ln in open("../logfiles/dmprapidtest.txt").readlines())  if len(s) == 2]
k = pandas.DataFrame.from_records(rows, columns=["t", "d"])

And then we can plot the autocorrelation (the covariance) with itself shifted in time, like so:

d = k.d   # just the measurement Series
dm = d.mean()
ss = [((d - dm)*(d.shift(i) - dm)).mean()  for i in range(400)]

autocov1

Let’s zoom in on the first 50 covariances:
(more…)

Saturday, October 15th, 2016 at 2:20 pm - - Cave, Hang-glide, Kayak Dive

Maybe I’ve got writer’s block. I’ve not even filled these into my logbook. I call it a hat-trick if I do a cave trip, a hang-glider flight and a dive in the same week. This is the fourth time I’ve done it. Generally speaking, the individual events are not all the greatest: the dive was pretty murky, the cave was gritty, and the flight was ridgy. Can’t complain.

The wreck of the Azmund is in Holyhead harbour about a mile of paddling out from the beach.

It was dark and murky and we didn’t find the way back to the boilers after starting on it. The wreck is huge though. Part of the metal juts out of water at low tide.
azmundwater

On the way back we discovered why the beach we launched from is not popular with kayakers — it dries out to about 500m. We couldn’t see our boats after the first time we walked back with a load to the car.
azmund

That was Saturday. There was a pleasant day out at Moelfre, with some people being terrified of the currents, but it was the wash from the joy-riding lifeboats that nearly sunk us. The image of the almost breaking 4 metre high wall of water that came upon us while we were anchored in the shallows of Rat Island a few minutes after they zoomed through the channel is going to live long in my memory. The second dive worked out well when we found the remains of the Royal Charter in the sand after groveling in the shallows among the kelp where it was supposed to be until giving up.

Then there was a cave trip to the far end of Ingleborough Show Cave (the only photo of which I have is a line of cavers getting changed on the footpath), followed by a quick escape home ostensibly to start clearing out the house, but which was in fact an excuse to be in North Wales for a flight off Penmaenbach.

penmanhg
I landed on the dwindling beach at high tide after an hour of very smooth sailing in the sea air.

frontroom

A concrete breaker was hired to smash up and take down the floor. We filled a skip with the crap a day later with some help from friends.

Now we live in a building site. Again. And it’s mid-way through October.

Sunday, September 4th, 2016 at 8:52 pm - - Canyon, Hang-glide

A bit of a bonus holiday slotted in here, with not much time or care to waste on the internet.

With three of us in the car, first we went down to a campsite near Perpignan and picked a 3.6/4 grade canyon of Llech, which was an absolute hit with all of us. There were jumps and toboggans galore, including one called the pistol that shot you up in the air 5m over a deep pool. We need to go back to that area and do the others.

llech2

Then I snuck in three days of hang-gliding off Ager with the bonus help of a retrieve driver. On day2 I tried to go behind the ridge, and it didn’t go well. I don’t know how I pulled it down into the field not of my choice without busting something more than the skin of my knee, but I got away with it.

It should have scared me more than it did. Instead my worst moments of terror were on the K5 rated via ferrata Cast Urquiza Olmo to the west of Ager by the lake.

On the third day up the hill I got an amazingly detailed briefing from some visiting British hang-glider named Al about where to go and what to expect (a huge zone of downwash behind the ridge which you can confidently get through if you start with 7000feet of altitude). It worked wonderfully on my third attempt.

tremp

Then I let myself down by nearly parking my glider on a rebar fence by curving round too wide and falling short of the field I was aiming for.
tremp2
But before that happened, the feeling came over me again where my wings became part of me for those few hours up in the sky. The joy was existential. A lot of the time I was circling with vultures. There are a lot of them about.

In the evening we picked up Becka from Lleida and then went to Torla-Ordesa to see the scenery. Unfortunately the morning buses were all full, and you’re not allowed to cycle up the tarmac road which carries the diesel buses because it’s a Spanish national park, so everything is banned even if it doesn’t make any sense. So we walked in until my foot-soles wore out on the way back and I had to catch the bus.

ordessa

Then, on the way back to France, we dropped in on the 3.2/4 rated Neste de Saux canyon, which wasn’t that great, but we were pleased because we proved we were still up to it.

Now we’re in a gite in Aspet with a bunch of cavers. Everyone is going out to run around the maze known as Felix Trombe, while I have carried on working on the ground window software, where I have implemented a real hack to create flat shading within a the GLSL GPU shading framework:

The trick is to note that the passage tube structures are made from quads which you can colour with 8 colours {-1,1,-2,2,-3,3,-4,4} such that no quad shares a colour with any of its neighbours (edge or corner otherwise). Choose the brightness factor on each quad (say it’s 0which goes:

float flatfac = max(0.0, max(max(abs(vflat4.x), abs(vflat4.y)), 
                         max(abs(vflat4.z), abs(vflat4.w))) - 510.0); 
gl_FragColor = mix(gl_FragColor, vec4(0.0, 0.0, 0.0, 1.0), flatfac); 

groundview3

(I’m now fed up with fighting with this crappy internet connection. It’s probably why I’m getting so much work done.)

Wednesday, August 24th, 2016 at 9:16 am - - Hang-glide

I spent the last three days at the washout known as the British Open Series 3 where one day out of five was flyable. This was yesterday from a hill called Camlo which is a “little flown hill, especially for hang gliders, as there is not a suitable bottom landing field”

Numpty here took off first with everyone watching and waiting because there were no clouds, and I got thrown about a bit. Luckily there were no other gliders in the air to dodge.

Then I came in and landed when things got full up like a zoo (orange glider on the 39th second of the vid).

Then I un-redeemed myself by sitting on takeoff for most of the next video until the launch window was about to close.

Most of the big boys got away during that time until I was one of just two gliders left in the air. I went in and landed just as the other one got away to a big cloud. Grumble.

Once you’ve tasted XC flying, nothing is ever good enough again.