Blogs

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.