With the help of several members of this community, I could make the prototype in the torpedo design work and I did a lot of measuring and mapping with it.

It went very well, so I decided to build an improved version of the sonar boat which you can see in the picture above.

But first I will share some impressions of my first boat. In the following picture you can see me with my "torpedo design" boat.

In the video below you can see the performance of the boat.

The ArduPilot worked very well and the speed, size and the operation range were satisfying. But the propulsion nozzle turned out to be very sensitive to sea plants. And in windy conditions with waves and in curves, it was rolling quite a lot. I measured a big lake with it as you can see in the Google Earth picture on the bottom of this page, but I decided to build a more stable boat.

So now I tell you about the Making of the improved boat:

The new boat should be able to carry more batteries, be more stable in the water, be faster and not be too much bigger. So I decided to build a small trimaran. I started to plan it with DELFTship which is for free and easy to use.

I also used NX to plan the space I needed in the hull as you can see in the pictures below:

The next step was the making of the positive mold. I could use the laser cutter of the Fablab in Aachen (https://hci.rwth-aachen.de/fablab) to cut the sections that were exported from DELFTship out of 3mm MDF.

At home I glued everything together with hot glue and filled it with Styrodur that I cut before:

After a lot of grinding and filling, it looked like this:

After some more grinding and painting, I made a negative mold with plaster bandages to keep the costs low and painted it with 2K paint. After waxing the mold I could start with the glass fiber:

I used the following product and which worked very well:

http://shop1.r-g.de/art/100110

The resin has a curing time of 40 min which makes it very easy to use. The result looked like this:

After equipping the hull it was ready for the water:

In the following video you can see the making of the boat step by step:

Before letting the boat into the lakes I wanted to be able to find it after its work under any circumstance so I included an XBee 900 pro for a GPS-data link. Also I wanted to be able to manipulate the track of the boat by a joystick with the XBee, so I printed a case for a small remote control to include the XBee, a thumbstick, a small Arduino and other switches.

I am now able to switch between the XBee-controll and the ArduPilot with a multiplexer on board.

After that final step, I was ready for the next lakes.

After improving the ArduPilot parameters the trimaran performed very well. I could switch the boat on, put it into the water and have breakfast at home, before picking it up after several hours and it was always there. If the wind had blown it away, I could track it via the XBee and with the Earth Bridge, I could watch its position live on Google Earth.

In this Video you can see the performance of the boat in different conditions:

The following pictures will give you some impressions of the measuring:

In this last picture, you can see the work i have done so far with the boats and in the area, there will be many more lakes for measuring.

If you have questions or suggestions just comment and I try to answer quick.

In this blog I would like to share my experiences with my new project, an autonomous transducer boat, controlled by an Ardupilot. 

After a long time of reading blogs, searching parts online and planning, I started my project. My plans are to build an Ardupilot controlled boat, which measures and logs the depths and the temperature along its path on remote lakes to be able to create depths and temperature plots of the lake.

The idea for the boat developed in my head after my last fishing trip to Sweden. I visit friends in a small village in south Sweden at least twice a year and I relax from work by fishing on the remote and calm lakes at that site. In the summer time, I am very successful in fishing and it’s very easy to catch several big fishes within a few hours. Since the lakes are frozen in winter, my friends and I tried to do some ice fishing but we didn’t catch a single fish even though we spend at least 7 days on the ice. We guess that we didn’t catch at the right spots because we have no idea, where the deep parts of the lakes are, and how the lakes look like underwater. After that unsuccessful vacation, I decided to build that boat so I won’t have to drive back home without a single catch.

Thanks to the two great blogs from Geir Andersen and Harald Molle:

http://letsmakerobots.com/node/21098

http://diydrones.com/profiles/blogs/ardupilot-goes-into-the-water

a lot of question regarding the sonar, the navigation and software were answered and my project could start. And these two blogs are the reason why I also share my experiences with you.

Right now, I work far away from home so I can only progress with the project every few weekends. I started 6 weeks ago with the most expensive and important part, the sonar. It took a long time to investigate, which sonar I could use and which sonar could communicate with my Arduino and after I finally accepted, that there is no way around spending at least 200€ for a good sonar, I bought the Intelliducer from Garmin and the communication between the Arduino and the sonar worked instantly. The most important thing about the transducer is that it’s a digital transducer that sends the information in NMEA 0183 language. The transducer is quite small, easy to include in the Boat, the resolution seems to be 0,1m (correct me if I’m wrong) and the maximum depths is over 300m. It also measures the temperature, which can be interesting for fishing as well.

The next stage of the project was the boat. I wanted to build a light and easy to realise boat, that is totally enclosed and waterproof. I also wanted it to be energy efficient and not too slow, so that the batteries would last at least for 4 hours and more than 10 km. I decided to use a torpedo design, since I could use cheap plastic pipes as the body. I only had to build the front and the rear part of the boat with fibre glass.

I could manufacture the positive Form with wood on the wood turner of my father.

After I produced a negative form around it by using bandages, I rinsed them with wax as a separator, and I started with the fibre glass. Even though the material of the negative mold seemed not to be the best for fibre glass I was happy with the results.

As propeller, I decided to use a kort nozzle from Graupner with 60mm diameter. In small speeds, the kort nozzle is supposed to be more efficient, and it also saves my propeller from rocks or other dangerous objects under water. For my boat with a diameter of 125mm the 60mm diameter of the propeller seems to be huge. But as an engineering student, I learned that a big but slow propeller is more efficient than a tiny but fast running one at the same speed. That was my progress for that long weekend and I was forced to take a break till last weekend, where I came home again.

In the first two stages, I invested around 300€ for the transducer and the boat body. The next stage would cost me another 300€ for the batteries and the rest of the electronic. The third most expensive part (after the transducer and the upcoming Ardupilot) is the battery. But will come on the next page.

As I already mentioned on the first page, mygoal was to construct a boat that could drive for at least 4 hours without charging while I could catch some fish :-). To reach that goal, my boat should weigh around 4 kg and the capacity of the batteries should be quite high. After a lot of searching in the internet, I decided to take LiFePo batteries, because they are supposed to have a gentle charging behaviour, they have a good Ah/kg value and you can buy them with a lot of Ah per cell. I finally got three of the Headway batteries put them into shrinking tubes and connected them to high quality cable and to a balancer cable. I also found a charger with a really good price that will charge and balance my batteries in the future with 6 ampere. All together I spend around 150€ on the energy system. I now have 15Ah with 11,1 Volts for a weight of 1,5 kg, which is very light in my opinion.

The motor was the next difficult part. How many turns per minute and what torque would I need for a propeller this size? I decided to buy two motors. One with a transmission of 1:6 and another one with a transmission of 1:11. A waterproof lid for easy and save access to the inside of the boat, a cheap digital 2,4 Hz 3-channel remote control, a motor controller for up to 15A and a steering servo made my boat ready for the first tests on the water to test the two motors with the different transmissions.

All the parts fit together perfectly and the radio controller worked great. I tested the boat in the bathtub first to see whether the stability was good enough for the test on the lake. It turned out, that the 1,5kg of the battery that I fixed to the bottom with hook and loop fastener, made the boat stable enough. I also checked the thrust of the boat in the small bathtub and the current consumption. At 11 volts, the 1:6 motor would take 1,9 ampere, with full thrust in stationary position (which is the worst case scenario). So the batteries would be able to supply the motor for more than 7 hours with full power, which was way better than expected. So the test on the lake could come.

On the lake near my home, the boat made a quite good performance. It was even stable in turns and the radio control worked perfectly. The speed was all right (around 4 km/h) for a long track via Ardupilot. But for a bit fun on the radio control, it could have been a bit faster though. So we didn’t build in the 1:11 transmission, and decided to buy the 1:2,5 transmission motor instead to test that one as well next time.

The long weekend brought my project a good step forward and in the next weeks, I will try to get the Ardupilot ready because in 4 weeks, I will be back in Sweden again, for the first real test.

I hope this project is interesting for some of you (even though it’s a boat and can’t fly ;-)) and if you like, I will share the future steps and the real test in Sweden of course.

Now my questions to those, who worked already with the Ardupilot and sounding:

1. I have the first and old Ardupilot already at home but I really think about buying the new Ardupilot, because it seems to me, that the handling and software improved a lot and is way easier with the new one. Does anybody have experiences with the old Ardupilot? Is the high price of the new Ardupilot worth it?
2. How can the Ardupilot share the GPS-data with my Arduino logger? I am ok in programming with the Arduino, but not an expert at all.
3. Unfortunately, the software DrDepth is not available anymore :-(. Not free and not even to buy. Is there somebody out there, who knows how do get the trail version or where to buy the full version? I was playing around with the free version of UnderSee Explorer, which is easy to use. But the plots seem to be better with DrDepth.