And so it begins… R/V Taani’s first weld was laid October 16, 2018 by Gabriel De Jesus of Gulf Island Fabrication, Inc., Shipyards Division.
The official keel laying date remains on track for 7 November 2018. In advance of the ceremony (and regulatory keel laying date for those who follow such arcania), some work has started on the skeg. The skeg, we figure, is a lot like a keel, which is lacking in the traditional sense from the Taani class.
So what is the skeg? Primarily, it helps provide directional stability; it keeps the vessel pointed straight and steady. At least it helps. Z-drive vessels are notorious for having low directional stability as compared to those with conventional shaft/propellor drives. They sort of fight each other while they compensate for minor deviations from the set course. As a result, Z-drive vessels’ bows can swing slightly from side to side as they move forward. This can be problematic for such science missions such as bathymetric surveys.
There are a few ways this can be mitigated. Operationally, operators can lock one drive strait ahead and use the other to steer. On the design side, we’ve made sure that the skeg is as long as possible and we’ve added fairings to the z-drives themselves. These fairings also help improve the hydrodynamics associated with directional stability and propulsive efficiency by improving water flow through the propellers. Lastly, the designers at Glosten added what we call a “skeglett.” This is a non-technical term that refers to the little baby skeg that extends between the z-drives (see the following picture). There is some disagreement about the efficacy of the “skeglett” but the thought was to do all we could to help keep the ship going the right way.
I should also add that a longer vessel is less susceptible to z-drive induced swings than a short vessel. So the added 6 feet we added recently will also help keep the ship on the straight and true course.
Here is a portion of the plan that the shipbuilders used to weld together Taani’s skeg.
Here’s the skeg coming to life.
All in all, this is very exciting! We’ve been planning and talking for years. Now, there’s some actual progress to building these great ships! Stay tuned. Once GIS turns the switch in a month, we’re really going to start seeing progress fast.
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