Semester One is Done

Team update

Phase 2: Off-Season Training

Sprint 4, December 6 — December 18

The overall goal of this sprint was to complete a full water test of Git Boat (Our new name for Damn Yankee) and start researching and making high level design decisions about the H-Boat, which will be called Hawsepiper. This is a shorter sprint than usual as we approach winter break and everyone was quite busy with finals, but we tried to make significant progress, and we did.

With Git Boat ready to go, we were ready to test. We took the boat out to the Babson pool one morning and put it in the water. A large poolside fan provided enough wind for us to test the systems. Overall, the test was a big success! Mechanically the boat held up quite well; our new seals were plenty sufficient to prevent water from getting into the boat and everything stayed in one piece. Some issues we did find are that the boat is a little prone to tipping (something we expected) and the rudder tends to slip down over time. For the tipping we plan on adding outriggers before testing in the spring, and the rudder just needs some proper key stock to hold the parts together.

High level Hawsepiper design is moving forward. Our hull will be a trimaran with one central main hull and two smaller outriggers. A big decision we made was to use a wing sail rather than a conventional sail. This decision was made after extensive research that showed that the primary disadvantage of a wing sail is that it requires precise control, something we don’t have to worry about on a robotic sailboat. Besides that it offers us greater control and efficiency.

A top-down view of Git Boat in the water

Software finished preparing Git Boat for water testing by calibrating the RC controller and servo positions. They also migrated their RC code over to use ROS, breaking it into two nodes. One node now handles reading the RC controller, and another listens for desired sail position messages and sets the sails accordingly. With the motors running on ROS, Software was also able to seamlessly integrate the Airmar ultrasonic weatherstation. Now the sails can be set from either the RC controller or by a ROS node which listens for wind direction readings and publishes sail positions. All of this was ready for demonstration by the Olin Exposition, though further testing is needed to refine the “autonomous” behavior.

After many delays we finally completed a full test of Git Boat! While it was of course not a flawless performance it was fully functional and didn’t suffer any catastrophic failures. Testing has helped us to plan out what we will do to get Git Boat ready for Spring testing. Meanwhile Hawsepiper is beginning to take shape with high level design decisions being made on the mechanical end.

~ Diego Alvarez (Mechanical Subteam Lead)