SEDATION 4 - Ergonomics

SEDATION 4 Ergonomics

Boats are supposedly built by people for use by people. So why don't many boats fit people comfortably? Lack of planning, cost-cuts during design, apathy and ignorance are all factors. Volumes have been written on the science of ergonomics and many practical examples of ergonomically-correct implementations exist. Yet, in many instances, "ergonomics" is just another marketing buzzword.
Designing a yacht with ergonomically correct proportions is not rocket science. Guidelines are readily available. These two diagrams, found in Principals of Yacht Design, served as the starting point for my 3D models.
I utilized a 3D solid model, with Pro/DESKTOP, to assure that every feature aboard SEDATION 4 fits my 6'3" body perfectly. The body and extremities can be posed into any position desired.
Overhead clearance was of primary concern. Static analysis is not sufficient. Dynamic simulation of activities such as climbing- and decending-stairs is required to be certain that adequate headroom exists in all scenarios. Dashing from the helm to the aft deck, for example. changes the relationship of the aft pilothouse windows to the top of my head. Dynamic analysis showed that these windows needed to be moved 7" aft to assure that I wouldn't bump my noggin during such an abrupt single-handed maneuver.

The stairways into each hull required 3 iterations before the design was "right"! I mocked-up model steps in plywood, using the ShopBot to cut precise computer-generated prototypes. Now the stairs are elegant. This may seem trivial but, when you're going to be spending years living-aboard, such details are essential to comfortable cruising.
Approach- and departure-angles to the bottom step are different, due to the floorplan, so nuances such as step corner radii and support under-cut are uniquely optimized for each hull.
2D floorplans are fine for sales brochures but worthless for optimum placement of amenities in a complex structure like a boat hull. Look at my floorplan of SEDATION 4 and notice the placement of the heads within their private compartments. This looks fine on paper but does NOT work in real life.
Locating the head's base fully outboard is the correct solution. Since the hull's sloping walls are further away within increased elevation above the floor, adequate shoulder room is available symmetrically with the head offset in this manner. It may look funny but it works great!
Switching from gasoline outboards to diesel I/Os required a re-design of the aft deck stairways for additional stiffness at the transom. In the process, I optimized the ergonomics of the steps and railings. Previous studies of the main hull stairways provided ideal step-length guidelines but the pitch was undetermined. With 47.5" vertical height between the aft deck and the side decks, I had to choose between 4 steps at 11.875" rise or 5 steps at 9.5" rise. I don't like spilling drinks when traversing stairs, so the 5-step decision was obvious :) Click the image at right for more details.
My trusty "Larry-Bot" model was employed, in the preliminary 2D layout, for basic hand rail dimensioning. All railings aboard SEDATION 4 are 30" above deck (ABYC recommends 29" as a minimum) despite the accepted industry norm of 24". The top rails are Ø1.5" while all (24) vertical stanchions are Ø1.25" to enable pretty welded joints. An Ø1/8" lifeline is placed half way up for additional safety. All bends are 8" outside radius to minimize stresses in the Schedule 40 aluminum tubing. Creating the 3D solid model was tiresome but the results justify the effort.
When placing the Bollards at their designed locations, I encountered undesirable interference with several of the rail's stanchions, so an iterative modification process followed. Several grueling hours later, I can now assure that there will be NO interference between lines attached to any of the 8 bollards and any rail stanchions. Some folks have commented that the bollards are obtrusive, if not downright ugly, and that they present large obstacles to deck passage. I argue that stubbing your toe on a Ø3.5" cylindrical post is much better than being jabbed by a traditional pointy-ended deck cleat. Bollards would not usually be considered in the context of ergonomics except for this esthetic debate :)