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OpenTransat

Building an Autonomous Sailboat That Pursues to Cross the Atlantic Ocean

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The goal is to build a fully autonomous sailboat that will cross the Atlantic Ocean while following strict rules of the Microtransat Challenge – a transatlantic race for autonomous boats. According to the rules, the maximum length of the boat is limited to 2.4 metres and the target point across the ocean must be reached within 25 km radius. It's quite a challenge, isn't it?

Our first transatlantic attempt commenced on September 12, 2016. The boat was launched from Newfoundland and was expected to reach its final destination in Ireland.

The boat went through a series of troubles and automatic recoveries, so it was really exciting to watch the progress.

The name OpenTransat suggests that all the details including the code, schematics and actual build process will be revealed. Going open-source will definitely speed up the development of autonomous sailboats and help others build upon a proven concept. We are just at the beginning of a long, thrilling journey!

Track the Boat

There are three trackers which are located on the boat. One Iridium tracker (RockBlock module) which is represented by the green color, and two Globalstar trackers (SPOT Trace) which are identified by the red and yellow colors.

On the tracking map, you can also read comments with explanations and assumptions, outlining what could possibly create challenges. Is the boat mechanically damaged by a wild storm? Was it hit by a floating object? Hopefully, we will find the definite answers after the boat recovery and a thorough examination.


Track the boat here:

http://www.opentransat.com

Launched from Newfoundland

The boat was shipped to Newfoundland in several packages and launched from a fishing boat about 5.5 km (3.4 miles) from the harbour. The route from Newfoundland to Ireland has been chosen as the shortest path across the Atlantic, and it's also in the direction of prevailing winds.

How It Works

The main framework is built from aluminum profiles on top of a surfboard, so the boat will never sink. The boat is balanced by a heavy keel that would flip the boat back over in case it flips. This concept has been chosen for its fast assembly and also because of the ability to make easy modifications. It's more like a proof of concept, with the purpose to test different hardware modules and navigation software before proceeding to a more streamlined design.

The sail is designed to resist high ocean winds. It is made from ripstop nylon that is reinforced by nylon webbing and thick carbon fiber tubes.

The electronics is securely sealed in a Pelican case and two polycarbonate cases. The Pelican case contains four LiFePo4 batteries, solar charge controller and an Arduino-based controller for navigation.

Satellite Communication

The Iridium satellite module, as well as GPS, is in a separate polycarbonate case for better signal reception. Another polycarbonate case contains a SPOT tracker and a GPS logger too.

You can find more about hacking SPOT Trace in the project log.

Rudder

The video below demonstrates the rudder being turned by a servo when the compass is off-course.

The servo alone is said to be IP67 waterproof, but what if the boat encounters 5-meter waves? A few layers of latex gloves filled with a silicone grease were added for extra protection.

Camera

A Git2 action camera is recording a 15-second video every 30 minutes. The camera has been hacked to be powered by the primary battery source and controlled by Arduino.

The video is stored on a 128 GB SD card, and it can be accessed only when the boat is recovered because it is unrealistic to transmit any part of the video over a satellite network. Sending a single high-resolution image would cost hundreds of dollars, not to mention that the speed is significantly lower than dial-up.

What's next?

What comes after failure, is another trial. A new boat built from super-strong materials with radically improved hardware and software will be definitely more capable to cross the ocean. Stay tuned for the next transatlantic attempt in 2018!

  • The finished sailwing

    Andy Osusky05/28/2018 at 07:04 0 comments

    The two resin-infused carbon fiber parts as seen in the project log were joined together with epoxy putty and waterproofed with a fiberglass tape. The inner skeleton makes the sailwing really robust.

    Sailwing Control

    The sailwing orientation is controlled by a flap that is adjusted by a waterproof actuator. Here's a video how it works:

    The actuator has a potentiometer that provides a position feedback. However, in my endurance test, the potentiometer was the first thing that failed. I found it's going to be pretty easy to mount a magnet on the end of the flap shaft and use it for a more reliable position feedback.

    Magnetic Encoder Teardown

    The magnet fits into a standard M6 nut after the nylon collar is removed. I glued it all together with a marine epoxy.

    I 3D-printed a PETG housing for the encoder PCB. The PCB will be potted with a heat-conductive epoxy compound.

    Finally, here's how the flap was built. A 1-mm carbon fiber sheet is glued to a carbon fiber tube and wrapped with Kevlar.

    The next thing to do is a sailwing position sensor that's designed as multiple Hall sensors around the mast. It will act as a backup wind sensor.

  • Hacking a linear actuator

    Andy Osusky05/14/2018 at 06:45 0 comments

    The actuator for sail control has to be small, lightweight and waterproof for full submersion. There are no great requirements for strength and life span as the force needed to adjust the flap is relatively small and it will move only when the wind direction reverses which may happen max. once per hour.  In the following video, a hacked actuator was completely submerged in a concentrated salt water and tested for 3000 cycles. 

    How to waterproof the actuator

    You need u-cup seals, plastic bushings and a piece of tube with a smooth inner surface, preferably a polycarbonate tube. The inner diameter of the u-cups must match the diameter of the actuator rod and the inner diameter of the tube must match the outer diameter of the u-cups.

    The u-cups are inserted into the tube. Plastic bushings keep the rod and tube concentric.

    The actuator is further reinforced by a fiberglass sleeve which also makes the body completely waterproof. The plastic end of the rod on the original actuator looks like a weak point, so I glued a piece of aluminum tube over it.

  • Rudder Control

    Andy Osusky05/09/2018 at 07:18 0 comments

    The rudder will be driven by a worm geared brushless motor mechanically coupled to a rotary magnetic encoder that provides an absolute position feedback. A while ago, I was testing this setup and shared my results in this project log. Now I have put together a metal "servo" that can be easily connected to the rudder shaft.

    Updated source code:

    https://github.com/OpenTransat/ServoEncoder

  • More carbon fiber parts

    Andy Osusky04/25/2018 at 06:36 0 comments

    The boat consists of 6 carbon fiber parts: two for the hull, two for the sailwing and two for the keel. All parts were made by resin infusion just like the hull as seen in the video from the previous log.

    The sailwing

    Plugs:

    Molds:

    Laying up fabric: 80gsm fiberglass, 200gsm Kevlar and 3x 200gsm carbon fiber

    Resin infusion:

    The parts released from the molds:

    The rectangular cavities you see on both sides of the sailwing will be fitted with small solar panels that will provide power for the actuator.

    The keel

    Plugs:

    Molds:

    Laying up fabric: 200gsm fiberglass, 200gsm Kevlar, 2x 200gsm carbon fiber, foam core (2mm Lantor Soric) and 2x 200gsm carbon fiber

    Resin infusion:

    The finished parts:

  • The finished carbon fiber hull

    Andy Osusky03/28/2018 at 07:26 0 comments

    The hull was built from carbon fiber, Kevlar and a foam core. In the video below, you can see the whole process from laying up the fabric to resin infusion.


    Bottom part (hull)

    The yellow outer layer is Kevlar. It protects the carbon fiber hull from impacts and abrasion.

    The rudder is designed with a flange that will fit this cavity in order to prevent entanglement around the rudder axis. This cavity was made in the same way as the cavities for solar panels on the deck (see the previous project log).

    Top part (deck)

    These cavities on the deck will fit solar panels with connectors and cables, making the boat hull streamlined.

    Because carbon fiber partially blocks GPS signal and satellite Internet connection, it's replaced with fiberglass and Kevlar in some areas of the deck. With this little trick, communication modules can be placed under the deck.

  • The molds are ready!

    Andy Osusky03/12/2018 at 07:51 0 comments

    Check out a video how the molds were built from the plugs:

    Bottom part mold (hull)

    Top part mold (deck)

    Now it's time to build strong carbon/Kevlar parts using resin infusion.

  • Finished plugs!

    Andy Osusky03/01/2018 at 08:44 0 comments

    Check out a video how the foam plugs were built:

    Bottom part (hull)

    Top part (deck)

    The next step is building the molds.

  • Final 3D Design

    Andy Osusky12/05/2017 at 10:30 1 comment

    The design posted back in 2016 has now been improved in many aspects. It's more streamlined, balanced, robust and optimized for speed.

    This rudder combines two interesting features – avoids entanglement and reduces the power needed to steer the boat. 

    Here's how it's designed on the inside. The heavy duty aluminum skeleton holds all the critical parts together.

    From this point, it's going to be pretty straightforward. The next step is to make a foam hull using a CNC foam cutter and then build the molds.

  • Successful Lake Test

    Andy Osusky11/06/2017 at 13:28 0 comments

    The small-scale model from the previous log has been tested on a lake. Wow, this wingsail concept works incredibly well!

  • Small-Scale Prototype

    Andy Osusky10/16/2017 at 11:47 0 comments

    A small-scale prototype of the boat has been built to test and tweak the concept before spending a lot more time building the bigger boat for extreme ocean conditions. It's a close copy of the final design with the same hardware and navigation software. Here's the build progress.

    Carbon Fiber Hull

    Different techniques were evaluated to build these two carbon fiber parts. I will give more details when building the ocean-going boat.

    Filling with Foam

    The hull has been filled with a closed-cell polyurethane foam. The side floats were made from XPS foam wrapped with fiberglass.

    Joining and Painting

    The two parts of the hull were joined using a Kevlar tape and painted with a special antifouling paint. This kind of paint doesn't give as smooth finish as a gelcoat or normal paint, but it prevents subaquatic organisms from attaching to the hull.

    Rudder

    The rudder is made from carbon fiber, Kevlar and a steel rod.

    Keel

    The keel is made from two threaded rods and a foam wrapped with fiberglass. Finally, the foam was dissolved with acetone to decrease buoyancy.

    Bulb

    The “bulb” is made from aluminum tube filled with lead and two 3D-printed plastic parts.

    Servo, GPS, Electronics Housing

    Electronics

    The battery provides enough power for 8 hours of continuous operation. 

    Wingsail

    The wingsail is made from a foam wrapped with carbon fiber. This kind of sail works much like an airplane wing – it automatically maintains an effective angle of attack using the small "tail" behind the large wing. This concept is inspired by experimental work found on www.sailwings.net.

    Finished Boat

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