Hull 002.

The stations attached to the strongback.
The stations of Hull #2 attached to the strongback.

I have discussed the hull construction process in earlier posts, which you can find via the above search bar. To recap, you take the hull design and “loft” the shape of each section or bulkhead, from the drawing. You then cut this out of 6mm marine ply (or equivalent), mount each of the stations onto a strongback, and now you have something which forms the shape.

I also need to add a keelson to the picture. A keelson is a long, keel-like piece of wood which runs from stem to stern, connecting the bulkheads. I cut one already but it turned out to be too short due to a miscalculation on my part. Generally I cut a thin (about 2cm wide) outline of the keel of the boat, from a sheet of ply.

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The Reboot.

CAD drawing of the MegaMOOP hull, courtesy of Professor Paul Miller.
CAD drawing of the MegaMOOP hull, courtesy of Professor Paul Miller.

According to the calendar, it is now 963 days since my last blog posting on here. A lot has happened in that thirty month period, but not a lot in terms of the robotic boat.

I’ve worked on a variety of designs of winged sail and I think I have a design which will work really well. More about that, anon.

You may also notice I redesigned the blog, and switched from Wordpress to Jekyll. I had originally planned to code a Ruby on Rails site, and this is mostly why there haven’t been any blog updates for the last couple of years. I wanted to incorporate automatic blog updates from the boat when she’s at sea, but trying to decide on a layout for the new blog was like trying to choose the paint colour for the bike shed. Eventually I just went with Jekyll as it allows me to have boat updates, and doesn’t involve spending months tweaking HTML and CSS.

The big news though is a decision I made last year, to switch away from my own hull design, which you can find here. Chatting with Professor Paul Miller of the US Naval Academy, I came to the conclusion that the design he and his students had perfected, which they call the MaxiMOOP.

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The New Winged Sail

The wing-sail is in two parts, a leading-edge and a hinged 'tail' or trailing edge.
The wing-sail is in two parts, a leading-edge and a hinged "tail" or trailing edge. This is a CAD drawing of the leading edge.

My original plan was to use a traditional mast and mainsail, with Yannick Lemonnier of West Sails volunteering to produce the sail. Yannick is no stranger to mad schemes himself, having competed in far too many Figaro races. These days, he spends his time sailing his Moth winged-beast, or racing his International 14. That is, when he’s not making sails for everyone from Beoga Beag to the Volvo Open 70s.

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The rubber hits the road. Sort of.

Now that the hull is (almost) complete, it's time to start soldering the electronics into place.
Now that the hull is (almost) complete, it's time to start soldering the electronics into place.

Due to other, exciting distractions (which I will mention in a later post), I haven’t had a chance to keep the blog up to date. Still, work progresses on the boat, and that’s the important part. Last month, with the keel now in its new position about 30mm further back along the hull, and sealed into place, it was time to add the electronics board.

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Latest on the hull

Here’s a quick sneak picture of the hull with the wiring harness complete and the decks sealed in place.

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The keel is still only temporarily installed so the main compartment is again flooding with sea water. The bow is still slightly down in comparison to the stern, but this is mostly due to the flooded compartment. Also, the keel still hasn’t been moved back, yet. That will happen this week.

The solar power connector and the masthead connector are visible just in front of the main compartment. The ugly brown tape is to seal up the deck fittings for the rudder and sail servo motors. The deck plates are taped to the hull using polyester resin and fibreglass tape. They need to be sanded smooth, ready for another final coat of epoxy and then a generous layer of antifoul. The antifoul coating will be one of the very last steps prior to the Microtransat. If you look at the previous blog posting on the SGS, the alu plate which supports the electronics will be mounted over the main compartment and secured in place.

Sailboat Guidance System

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A quick look at the almost-complete Sailboat Guidance System (SGS). The board on the left is Igor. Otto is on the right, and the main CPU (Mother) is hidden underneath. The ribbon cable brings all the I/O to and from the boards. The red insulating tape is to remind me of some of the last remaining wires which need to be connected. You can also just about make out the DC/DC converter which is just underneath the ribbon cable at the bottom of the picture.

The First Sea Trial

On September 1st, we launched the hull in Aughinish bay, without sails, rudder or electronics. The purpose was to see how the hull performed in open water, with the keel attached. As the keel wasn’t properly attached or sealed in place, the main compartment flooded with water, but as the compartments are individually water-tight, this wasn’t an issue. It did lower the boat in the water somewhat, but not to any significant degree.

As the compartment wiring wasn’t completed, and the deck panels weren’t glassed in place, they were attached to the hull using duct tape. Not pretty, but it works.

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REDIS

After a lunchtime conversation with a friend of mine, I ditched some of the earlier design considerations around message-passing and MQ-based systems in favour of the NoSQL database Redis.

Redis is an open source, BSD licensed, advanced key-value store. It is often referred to as a data structure server since keys can contain strings, hashes, lists, sets and sorted sets.

That’s according to the official blurb on the web site, at least. It has several interesting components which are useful for Beoga Beag. It has a rudimentary pub/sub architecture pattern, it is extremely lightweight, it stores its database in memory rather than on a disk (so it’s less likely to burn through the Compact Flash file system), and it has an “append-only file” (AOF) archive mechanism.

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Hull water tests

Earlier this month, once the hull and keel were mostly finished, we took the boat down to Aughinish bay to see how she performed. I have some video footage of the hull in the water, which I will upload a little later on. To ruin the suspense, Beoga Beag didn’t sink! In fact, she moved through the water quite nicely, but more about that later on.

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The new rudder

Thanks go to Colman Corrigan for designing and building the keel and rudder. The keel follows the traditional NACA shape, with a rounded leading-edge, tapering off to a narrow trailing edge. It is approximately a 6318 shape, with the maximum width being about 36% of the length of the cross-section. Overall, the keel is coming in at about 750mm from hull to the end of the bulb, and about 240mm from front to back. That’s a 3:1 aspect ratio.

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