Archive for April, 2016

Alex sanding the boat, early in the process.

Alex sanding the boat, early in the process.

Last weekend, Jeremy, Wim, Alex, and I got together to paint the Hackerboat. The original plan was to get it all done during daylight hours last Saturday... but the filling and sanding steps took much longer than anticipated, so we only got to primer. Just that made a major improvement in the boat's appearance ahead of MakerFaire next month.

The paint I bought for the job was Blue Water Mega Gloss topside paint. It's a single-part polyurethane marine paint. Since this iteration of the Hackerboat won't spend long periods in the water, we're going to do the whole thing with topside paint. It's not too horribly expensive -- about $18/qt. I want to paint the boat safety orange (so it can be seen easily), while Wim would like to paint it with dazzle camo. So we compromised on safety orange and black dazzle camo. I picked up one quart each of black, bright orange, and white primer.

The polyurethane paint is supposed to be very thoroughly mixed before use. Wim and I, in a bout of optimism, stirred both the primer and the orange paint. When the orange paint dried on the stir stick afterwards, we discovered that Blue Water's color department believes that ketchup is bright orange. I hope it will look more like orange over primer, but I am not all that hopeful.

The fiberglass work we did on the hatch coamings a couple of years back was pretty rough, so the first order of business was to get it filled and sanded. We went through about 3/4 of a gallon of Bondo getting the topsides in somewhat paintable shape. We probably could have used the rest of the gallon, but it was getting late and we wanted to get the primer on before the end of the day. There's not much description here because the tubes are full of tutorials on how to do this and it's not the world's most interesting work.

Bottom primed

Bottom primed

Once we'd gotten the last coat of Bondo on the boat, we immediately flipped it over to sand and prime the underside. This was nice and uneventful, and it made the bottom of the boat look less busted immediately.

The can of primer had led us to believe we'd be waiting a couple of hours before we could flip it over and finish sanding the Bondo. This turned out to be very pessimistic -- the first primer we laid down was dry to the touch by the time we were done priming the boat. We still waited half an hour (and time for a picture) before flipping the boat.

Wim and Alex priming the boat.

Wim and Alex priming the boat.

We masked off the hardware we couldn't remove and primed the topsides. It went on as quickly and painlessly as the primer on the bottom, and was mostly dry by the time we finished the coat. It took about 3/4 of a quart can to do the whole topsides. I think this is because we did not thin it; however, it is clear from that experience that we will have to thin the orange paint if we want to get two coats out of the can. We'll do the stripes in black over that as a third coat.

The boat looks better even with just the fill and primer; I am looking forward to finishing up the paint job today.

Filled and primed

Our launch last fall proved that the Hackerboat hardware was working fine (other than the GPS) but that the software needed a complete rewrite. We've been working on that for the last few minutes. Debugging is a bit on the slow side, but we anticipate being ready to get back in the water in the next couple of weeks. We will be at both MakerFaire Bay Area and Toorcamp with the Hackerboat in tow. This weekend, we're going to put some paint on the boat to it looks a bit better in preparation for the next launch and for public show. There will be pictures! But let's talk about the systems in preparation to talk about the software.

The current electronics configuration of the Hackerboat has a bit of a Rube Goldberg quality. The underlying intent is to build a system out of relatively small modules that can be added to without major hardware surgery. Here's a schematic diagram of the various bits and pieces. Dark red is power and power control, green is computers, yellow is propulsion, orange is communication, blue is sensors, and purple is non-propulsion actuators.

Hackerboat-Systems-Diagram

The first thing to notice is that we have two on-board computers -- a Beaglebone and an Arduino. The intent is that the the Arduino will handle all of the low-level real time functions while the Beaglebone handles all of the higher-level navigation, obstacle avoidance, and mission functions. Among other things, the relatively more power hungry Beaglebone can be put into a low-power sleep mode for extended periods, especially while in the open ocean. On the flip side, we can use the Linux environment and fast processor on the Beaglebone to support all manner of cool navigational modes and mission applications.

The communications is likewise a layer cake. Our ship to shore radio is a Ubiquiti 900 MHz Ethernet bridge. The shore side radio has a directional antenna built in to the radio and the ship side uses an external antenna on the mast. For internal data on the boat, we use a standard WiFi router. This means we don't have to futz with waterproof Ethernet cabling (expensive and troublesome)... and we can add new equipment to the boat for the cost of a WiFi interface.

Right now, the sensor fitout is very basic. We have an IMU/magnetometer combo for heading, a GPS for position, and start/stop buttons on the outside of the boat. We're planning to add cameras next, and of course we have the option to mount any sort of instruments we like for mission requirements later.

Next update will be painting, and after that I will get into our software architecture.

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