"In het verleden behaalde resultaten bieden geen garanties voor de toekomst"
About this blog

These are the ramblings of Matthijs Kooijman, concerning the software he hacks on, hobbies he has and occasionally his personal life.

Most content on this site is licensed under the WTFPL, version 2 (details).

Questions? Praise? Blame? Feel free to contact me.

My old blog (pre-2006) is also still available.

See also my Mastodon page.

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Sailing trip to the Isle of Wight (Sponsored by Murphy)

Atlantis under sail

I originally wrote this, just under a year ago when I returned from this sailing trip. I found this draft post again a few weeks ago, being nearly finished. Since I'm about to leave on a new sailing trip next week (to France this time, if the wind permits), I thought it would be nice to finish this post before then. Even though it's a year old, the story is bizarre enough to publish it still :-)

I've put up photographs taken by me and Danny van den Akker up on Flickr.

Last year in May, I went on a 11 day sailing trip to the Isle of Wight an island off the southern coast of England. Together with my father, brother and two others on my father's boat as well as 10 other people on two more boats, we started out on this trip from Harderwijk on Thursday, navigating to the port of IJmuiden and going out on the north sea from there on Friday morning.

Initially, we had favourable wind and made good speed up to Dover at noon on Saturday. From then on, it seemed Murphy had climbed aboard our ship and we were in for our fair share of setbacks, partly balanced by some insane luck as well. In any case, here's a short timeline of the bad and lucky stuff:

  • :-( Just around Beachy Head, our engine stopped running. We quickly restarted it and carried on, but shortly after the engine stopped again. It didn't want to start again either. In case you're wondering
    • not having a working engine is a problem for a (bigger) sailing ship. Sailing into an (unknown) (sea) port is usually hard and on the open sea your engine is an important safety measure in case of problems.
  • :-) Fortunately, Atlantis, one of our companion ships was only a few miles ahead (after having crossed most the North Sea through different routes, many miles apart). We sailed towards the port of New Haven, where they towed us into the port.
  • :-( We diagnosed that there was a problem in the fuel supply, but couldn't find the real cause. We spent the sunday in the thrilling harbour town of New Haven, waiting for a mechanic to arrive.
  • :-) On monday morning, a friendly mechanic called Neil fixed our fuel tank - it turned out there was a hose in there with a clogged filter as well as a kink near the end that prevented fuel from getting through. Neil cut off the end of the tube, fixing both problems at once and our engine ran again like a charm.

Fort in the Solent

  • :-( We continued towards Wight around noon, but shortly after passing No mans land Fort - guess what - our engine stopped running again.
  • :-( This time we had no friends around to tow us in, but there was a Dutch ship (the Abel Tasman) nearby. We tried to get their attention using radio, a horn and a hand-held flare, but they misunderstood our intentions and carried on. We kept on sailing, but contacted the very much polite and helpful Solent Coast Guard by radio, to let them know we were coming in by sail and might needed a tow into the harbour.
  • :-) After we finished our conversation with the Solent Coast Guard, the Abel Tasman hailed us on the radio and offered to tow us all the way to the harbor. With the wind dropping, we gladly accepted.
  • :-) On monday evening We arrived on the Isle of Wight!
  • :-) In the harbour, our engine started again (with some initial coughing). Yay for having a working engine, but without having fixed a problem, it could break down any moment. :-( We had some theories about what the problem could be, but no real confidence in any of them.
  • :-) In the morning, we called for Tristan, a mechanic from the town Cowes where we were staying. He had a look at our engine, but since it was running again, there wasn't much he could do. He found a connection in the fuel line that wasn't very tight - guessing that that had allowed some air to slip into the fuel line. He tighted the connection and left us again.
  • :-( Shortly after he left, we started the engine for a short refueling trip - and it stopped running again. We called for the mechanic to have another look, but he didn't show up all day...

On the open sea

  • :-( Near the end of the day, we didn't want to wait anymore and tried to bleed out the air from our engine, thinking that was the last problem. No matter how hard we tried, air nor fuel would come through. Debugging further, we found that the fuel tank would again not supply any fuel at all. We "fixed" this by disconnecting the fuel line, blowing into it and then sucking at it (credits to Jan-Peter for sucking up a mouthful of Diesel...). Together with the diesel there came also a wad of something that looked like mud.
  • :-( Previously, we didn't suspect any pollution of our fuel tank, because the looking glass in the fuel filter was squeeky clean. Now, prompted by the gunk coming out of the tank, we opened up the filter to have a more thorough look and it turned out the filter was nearly completely filled with the same muddy stuff (which turned out to be "Diesel Bug" - various (byproducts of) bacteria and other organisms that like liveing in diesel tanks)
  • :-) We didn't have a working engine yet, but at least we knew with confidence what the cause of our problems was, and had been. As Danny stated it: At least it is truely broken now. All we needed now was machinery to filter our fuel and rinse the inside of the tank.
  • :-( On Tuesday, we found another mechanic who couldn't help us directly, but made a few phone calls. He found someone with the exact machinery we needed. The only problem was that the machinery was in the Swanwick Marina, on the UK mainland.

Improvised fuel tank

  • :-) On Wednesday, we tried to get into contact with the mechanic in Swanwick, to see if he could come over to Wight by ferry. We weren't hopeful, so in the meantime we also found a small plastic fuel tank (normally used for larger outboard motors) that could serve as a spare diesel tank. After also finding a few meters of diesel hose, getting an extra hose barb fitted and even getting a valve for fast on-the-fly switching between tanks (Thanks to Power Plus Marine Engineering for going out of their way to help us!), we had a working engine again by the end of the day!

    We weren't confident our shiny new tank to sail all the way back to the Netherlands using it, but it would be more than sufficient to get over to Swanwick to get our main tank cleaned. As an extra bonus, it would be a good backup tank in case we still had problems after cleaning.

  • :-) Early Thursday morning, we headed over to Swanwick where Geoffrey and Johnny laboured all morning to get a ton of sludge out of our tank. They sprayed the fuel back in using a narrow piece of pipe to clean the stuff off the edges of our tank as good as possible.
  • :-( As soon as they were done, we cast off and set course to Brighton Eastbourne Dover Ramsgate Dunkerque, Oostende, Zeebrugge, Dunkerque. Unfortunately, the wind direction was unfavorable (and later also didn't abide by the prediction, in our disadvantage of course), so we ended up sailing for only a small bit and using our engine most of the way.

    We changed our destination a few times along the way, usually because we thought "We might as well go on for a bit more, the further we go now, the easier it will be for the last stretch". Near Dunkerque, we planned to go on to Zeebrugge, but the wind picked up significantly. With the waves and wind against, we were getting a very rough ride, so we stopped at Dunkerque after all.

  • :-( We came into port friday after office hours, so there was no personell anymore. In the restaurant we managed to get an access card so we could get to the toilet and back again, but the card had no balance, so we couldn't even take a shower...
  • :-( Early saturday morning we carried on, this time with favorable wind direction, but not enough wind to make a decent speed. Since we lost all the slack in our schedule already (we had planned to be home by saturday afternoon), we used our engine again to make some speed.
  • :-( Shortly after crossing the Westerschelde, our engine stopped running again (can you believe that?). We quickly found that the engine itself would run fine, but would stop as soon as you put it into gear - there was something blocking up our screw propeller. Using Danny's GoPro underwater camera we confirmed that there was indeed something stuck in the screw. We didn't want to go into the water to fix it on open sea because of the safety risk, as well as the slim chance that we'd actually be able to cut out whatever was stuck.

  • :-) We contacted the coast guard again (the dutch one this time), telling them we'd sail towards the Roompot locks and would probably need a tow through the locks and into the harbour. We contacted the Burghsluis harbour and found they had a boat crane and were willing to operate it during the evening, so we had our target.

  • :-( Then the wind dropped to nearly zero and we just floated around the North Sea for a bit. After an hour of floating, we contacted the coast guard and asked them to tow us in all the way - we were losing time quickly and with unreliable wind, there was no way we could safely cross the northern exit channel of the Westerschelde.

Diver on the open sea

  • :-) While floating around a bit more, waiting for the coast guard to arrive, we slowly floated nearer to a small boat that we had previously seen in the distance already. Now, and this is where the story becomes even more unlikely, this boat was running a "diver flag", meaning there was a diver in the water nearby.

    We slowly approached the boat and shortly after yelling over our problem to the woman on the boat, the diver emerged from the water. She told him of our problem, he swam over and under our boat and not even 30 seconds later he emerged again carrying a fairly short but thick piece of rope that had been stuck in our screw.

    We started our engine and were on our way again, suffering about a 3-4 hour delay in total.

  • :-) We contacted the coast guard again to call them off, but they were already nearly there. To resolve some formalities, they continued heading our way. A minute or so later, the Koopmansdansk, a super-speedy boat from the KNRM came alongside. After we gave (read: Tried to yell over the roaring of their motor) them some contact information and the gave us a flyer about sponsoring the KNRM, we both went our separate ways again.


  • :-( During the night, a thunderstorm came over us. I missed most of it because I was sleeping, but Jan Peter and Danny were completely drenched and attested that it was both heavy and somewhat scary due to the lightning.
  • :-) Early sunday morning we went through the locks in IJmuiden, passed through Amsterdam and the Markermeer pretty uneventful. It even seemed like I would be at home just in time to head over to Enschede for our regular Glee night with some friends.
  • :-( We were running low on diesel, so we had to find a place to fuel up in Lelystad. We found a harbour that was documented to have a gas pump, but didn't have one, so wasted some time finding one...
  • :-( When we got to the locks of Roggebotsluis, it took a long time for the bridge to open. After floating around for 10 minutes or so, we noticed that one of the boom barriers (slagboom) looked warped and bent. Turns out just before we arrived there, some car got locked in between the barriers, panicked, hit the barrier while backing up and then sped away past the barrier on the opposite side. A mechanic was being summoned, but being a sunday...
  • :-) After a short while, the bridge controller fellow came out, pulled the boom somewhat back into shape a bit and announced they'd give it a go. Thankfully for us, everything still worked and we were on our way!
  • :-) No more delays after that. Brenda picked me up in the harbour, where I took a very quick shower before we headed to Enschede. Just in time for Glee, though I started falling asleep before we were even halfway. Apparently I was exhausted...

Overall, this was a crazy journey. All the problems we had have been a bit stressful and scary at times, but it was nice nonetheless. I especially enjoyed trying get things working again together, it was really a team effort.

Improvised Arduino NMEA multiplexer

Also interesting, especially for me, is that we had installed an AIS receiver on-board, which allows receiving information from nearby ships about their name, position, course and speed. This is especially useful in busy areas with lots of big cargo ships and to safely make your way through the big shipping lanes at sea.

This AIS receiver needed to be wired up to the existing instruments and to my laptop, so we could view the information on our maps. So I spent most of the first day belowdecks figuring this stuff out. I continued fiddling with these connections and settings to improve the setup, running into some bugs and limitations. Knowing I might have to improvise, I had packed a few Arduinos, some basic electronics and an RS232 transceiver, which allowed me to essentially build a NMEA multiplexer that can forward some data and drop other data. Yay for building your own hardware and software while at sea. Also yay for not getting seasick easily :-p

Now, I'm getting ready for our next trip. We start, and possibly end, in Vlissingen this time (to buy a bit more time) and intend to go to Cherbourg. Let's hope this journey is a bit less "interesting" than the previous one!

Related stories

0 comments -:- permalink -:- 19:39
New career addition: Education

I don't really have a well-defined plan for my professional carreer, but things keep popping up. A theme for this month seems to be "education".

I just returned from a day at Saxion hogeschool in Enschede, where I gave a lecture/workshop about programming Arduino boards without using the Arduino IDE or Arduino core code.

It was nice to be in front of students again and things went reasonably well. It's a bit different to engage non-academic (HBO) students and I didn't get around to telling and doing everything I had planned, but I have another followup lecture next week to improve on things.

At the same time, I'm currently talking with a publisher of technical books about writing a book about building wireless sensor networks with Arduino and XBee. I'll have to do some extensive research into the details of XBee for this, but I'm looking forward to see how I like writing such a technical book. If this blog is any indication, that should work out just fine.

For now, these are just small things next to my other work, but who knows what I'll come across next?

0 comments -:- permalink -:- 23:03
Replaced GPG key

For anyone that cares: I just replaced my GPG (Gnu Privacy Guard) key that I use for signing my emails and Debian uploads.

My previous key was already 9 years old and used a 1024-bit DSA key. That seemed like a good idea at the time, but for some time these small keys and signatures using SHA-1 have been considered weak and their use is discouraged. By the end of this year, Debian will be actively removing the weak keys from their keyring, so about time I got a stronger key as well (not sure why I didn't act on this before, perhaps it got lost on a TODO list somewhere).

In any case, my new key has ID A1565658 and fingerprint E7D0 C6A7 5BEE 6D84 D638 F60A 3798 AF15 A156 5658. It can be downloaded from the keyservers, or from my own webserver (the latter includes my old key for transitioning).

Now, I should find some Debian Developers to meet in person and sign my key. Should have taken care of this before T-Dose last year...

0 comments -:- permalink -:- 14:03
New website for "Matthijs Kooijman IT"

Matthijs Kooijman IT

Since 2010, I've been working as a Freelancer (ZZP'er). Of course I registered a domain name right away, but until now, I didn't get around to actually putting a website on there (just as single page with boring markup and some contact information).

Last week, I created an actual website. It's still not spectacular, but at least it has some actual content and a few pages etc. So, with a modest amount of pride, I present: the website of Matthijs Kooijman IT.

For anyone wondering: I didn't put up some bloated CMS, running on a database, but I store my content in a handful of text files (using Markdown markup) and using poole to translate those to (static) HTML files. I keep the files in git and set up a git post-update hook to generate the HTML to make things extra convenient.

0 comments -:- permalink -:- 17:07
Winter Efteling :-D

Last weekend, I've been at the winter Efteling. The Efteling opens up for a few weekends during the cold season, with an icy theme. Last weekend was the first. Brenda had been buying a lot of Madras Chicken from Knorr, which bought us six tickets at a discount. We offered two to Dennis and Alice and gave the other two to Suus and Gijs for their respective birthdays.

Monkey Matthijs We also knew about a few other friends (LARPers) who would go in the same weekend, but a whole throng of LARPers turned up last Saturday (about 25 to 30 I think). Apart from that, it wasn't too busy at the park, so there were hardly any lines during the day. I have a nice souvenir picture from the Pandadroom (Panda dream) attraction (since everyone knows the Pandadroom isn't so much fun because the fancy 3D animation, but because of the playground with video games that comes after!).

Since we did about every attraction in the park, my brains were upside down in my skull and I was pretty exhausted when we finally got on the train home. Yet, I was not headed home, since my aunt held her birthday in Eindhoven, which is pretty close to the Efteling. I joined in on the party and was not in bed before 0530.

I went home the next day after breakfast (halfway the afternoon), back to Brenda. As you might imagine, the exhaustion had hardly lessened, so I decided not to get up together with Brenda Monday morning at 0650. Good thing, since I managed to sleep until 1300 for a whopping 13,5 hours of sleep. Didn't know I was that tired...

0 comments -:- permalink -:- 17:04
Folk weekend in Mattstedt with the Gonnagles

Gonnagles logo

Last weekend, I've travelled to Mattstedt, a small village near the center of Germany, to attend a folk festival there. The Gonnagles, a Dutch folk band, were performing at the festival and asked me to help out as an audio technician (since not all of the Gonnagles could attend). Liking the opportunity to do some more sound engineering, do some dancing and hang out with the Gonnagles, I agreed to come along.

Route to Mattstedt

After I said yes, I realized that the Festival was quite far into Germany (5 hours from Enschede, though on the way there, we got caught in a traffic jam making it 7,5 hours, plus 1,5 hours from Amersfoort to Enschede). Still, I shared the car with nice people (Erik and Moes on the way there, just Erik on the way back) and the festival was nice, so in the end it was worth every minute of driving time. Moes, Erik and I also travelled on friday instead of saturday, leaving an extra fridaynight for dancing and saturday afternoon for relaxing.

During the festival, I ended up helping out with the audio engineering of the rest of the festival, instead of just the Gonnagles' performance. There were two audio technicians there, but neither of them were very experienced in setting up a live performance and getting to the bottom of any problems that (always) show up. Also, the rented equipmented wasn't quite top-notch quality, which didn't really help either.

Fortunately, I was able to help out a bit and debug some problems with the PA system and monitor speakers. On saturday, I also did most of the mixing for Cassis, one of the other bands. Apparently people thought I did a good job, since I got a lot of thanks from people who apparently thought I single-handedly saved the festival from horrible sound quality (which would be underappreciating the other technicians, which also worked hard to get everything running).

The festival itself was nice as well. I always enjoy the performance of Parasol, who are very talented, but I also enjoyed the other bands. The weather was good, so I had some nice relaxed moments lying in the sun, I listened to good music, shared some nice dances with a pretty German girl, and just had fun.

So, again next year?

0 comments -:- permalink -:- 16:59
New pet: Pelle the pelikan

Pluche Pelle the pelikan Sanquin

For the occasion of my fourtieth blood donation at the Sanquin blood bank, I got a nice pluche pelikan (which is their mascotte / logo). It got a nice spot on top of one of the speakers on my desk, where it has a nice view of my room.

Are you a blood donor yet? More donors are still needed in the Netherlands, so sign up now!

Related stories

0 comments -:- permalink -:- 16:58
Blood donor


As of today, I am officially a blood donor. I've been at Sanquin, the national blood donation organization, this morning to deliver half a liter of blood. I have been there once before, to let them take a small amount of blood for blood tests. Apparently they found nothing obviously wrong with, so I was invited again. Depending on the need, I will be invited a few times each year to give more blood.

Blood donation is something that has been on my "todo" list for quite some while now, so I decided to simply stop delaying and do it a while back. I think that everybody should think of being a blood donor. A lot of of our health care is dependent on donor blood. Since people expect health care whenever they need it, can't we expect people to give blood whenever needed?

What scared me a little, was that Sanquin Enschede is still short of a lot of donors. They are aiming to have another 1450 donors, while they currently have about 5000. Considering that Enschede has over 150.000 inhabitants, that amounts to just over three percent. Surely there are more people prepared to invest some time in this?

So, are you not a blood donor yet? Sign up now! It will only cost you some time every now and then, the people are very nice and there's free drinks and cookies involved :-)

Edit: This used to say Enschede had only 200 donors, but that turned out to be 200 hundred new donors in their current campaign for new donors. In total, Enschede has around 5000 registered donors.

3 comments -:- permalink -:- 16:58


This morning I've entered the next stage of my car mechanic career: I've stopped by the junkyard to get some spare parts for Brenda's car. About a year ago, I broke off one of the door handles from the car (the door was frozen shut, and I underestimated my own strength...). The KIA dealer was happy to replace the handle, for EUR 150 or something silly like that. Considering there was enough of the handle left to operate the door perfectly (after being pointed out which part to hold, mostly), we just left it broken for a year.

A few weeks back, we found a crack in one of the outer mirrors. There was no clue how this happened, but perhaps it got hit by some stray snowball or the winter's cold made it snap. Since the outer mirrors are a failure point for the APK (yearly checkup), we really needed to replace those.

So, this morning I went to a local junkyard, that had an old Kia Pride. It was a ghostly sight, all those half disassembled cars. Some missing wheels, hoods, doors, etc. They had a spare mirror on the shelf, but the door handle was still on the car. I found a blue Kia Pride out back, and after some fiddling disassembled the door handle. I actually quite like this junkyard thing: Not only do you get to do stuff with your own car, you can find out how its done on some other car first, without the risk that you break more stuff while prying something loose.

Just now, Brenda and me put on the "new" parts, so the car is as good as new again (if you ignore the occasional squeeking and creaking, of course), for just EUR 25.

Next up is finally fixing up some rusty spots on the paint of the car, but I'd really like to have some place to put the car inside for a few days for that (lest my fingers freeze off and the new paint won't dry).

0 comments -:- permalink -:- 14:23
Hostel review: St. Christopher's in Edinburgh

Party hard, sleep easy

Last week, I've been in Edinburgh for a few days for a conference on Haskell and functional programming. Since we were late with booking, all the nearby and slightly cheaper hotels were booked full. Since it's likely we'll have to (partly) pay our travel to and stay in Edinburgh ourself, we went looking for a hostel nearby. The first one I tried was pretty close, so we booked four nights at "St. Christopher's Inn". I'll write up a review of the place, since I was rather content with it. A small disclaimer: This is the first hostel I've been to, so I can't really compare it with anything but my common sense expectations of a hostel :-).


St. Christopher's is a hostel co-located with Belushi's Bar at Market street. The bar is a nice bar with slightly alternative (lots of torn out jeans and piercings), but very friendly people. The bar and hostel are heavily integrated, so the reception is behind the bar and breakfast is served there as well. There are two separate bars, so there's usually plenty of room.

The hostel is located on Market Street, which is directly south of Waverly train station. This means you're close to public transport, but also right in the city center and close to attractions like the Edinburgh dungeon, Edinburgh castle and a big shopping center (St James IIRC).


St. Christopher's has a wide range of services. Included with our stay was free breakfast every morning, consisting of bread / toast, coffee / tea and various kinds of cereal. I personally found there was not much choice in bread spreads (Is this a proper term?), just different flavours of jam, peanutbutter and marmite (though I usually only eat the latter with cheese), but that's probably how Scottish breakfast works (and it was still very enjoyable).

There is free WiFi in the bars, which is a nice service if you bring your laptop. There are also a few computers available, but they cost a pound for 20 minutes of use.

There is a lot of useful stuff for sale or rent, like deodorant, toothpaste, padlocks, towels (rent), power plug converters (rent), etc. Most of these go for just one or two pounds, so better than buying them at the airport :-) There is a laundry machine available for a few pounds.

On the first floor, there is a "Chill Room", which has a big TV and some moderately comfortable couches. While we were there, the room was a bit messy, I suspect they recently installed new electric lockers in the luggage room (behind the chill room), which caused a bit of mess. This luggage room offers free lockable cages (bring or buy a padlock) and rentable electric lockers to store your luggage. Unfortunately there is no WiFi coverage in the chill room, so you'll have to do your surfing down in the bar (which might be full and noisy during the evenings).

Room & Beds

I can't say anything general here (I've only seen one room), but I'd expect most rooms to be similar. We were sleeping in a 6 bed dorm on the fourth floor. The room offers space for the beds, but not much else. Fine for sleeping, but less suited for spending the day.

The beds are bunk beds, so you might need to sleep on top. The beds weren't too big (I'd guess they're 1.90 long, since I needed to curl up a bit to fit in) and didn't have the best matrases, but they were ok enough. Linen is included with your stay, so no need to take a sleeping bag.

Each bunk has two cages underneath for storing valuables. You'll need to have your own padlock to lock them. You can buy these at the reception (for just two pounds), but you might want to take a slighly bigger one yourself (one or two of the cages in our room had a broken handle, so they could only be locked with a bigger lock).


In summary, I found this a very decent hostel, with good service. If you have any different or additional experiences, don't hesitate to leave a comment!

2 comments -:- permalink -:- 21:40
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