Creating a model of a boat before building it is a common procedure, and one I find very useful. For a 23′ boat, I chose to build a 1:4 scale model; this worked great since the 7′ 8″ model was big enough to use as a tender. For a nesting kayak that I designed, I started by building a full-sized model (also known as a mock-up) out of cardboard, to test for accuracy before cutting expensive plywood. The cardboard parts would be used for patterns.
My latest project is a 17′ pocket cruiser. The design challenge was to create accommodations for two with an acceptable level of comfort. Working with drawings and scale models was not going to definitively prove the success of the design or the many small construction details that would need to be considered when building the finished boat. My solution was to build a mock-up strong enough to climb aboard.
I made drawings and a half-hull model and then drew the frames full-scale. To begin the construction of the model, I gathered a supply of cardboard and scrap wood. As when building most boats, the keel and stem of my model were constructed first and then the frames set up on the keel. At this point, the mock-up departed from the traditional boatbuilding sequence. Instead of planking the hull, I constructed all of the interior components. The advantage was that none of the interior components had to be measured or scribed to fit the inside shape of the hull; they could be left to extend outside the hull between the frames and then marked for trimming using battens sprung around the frames.
The mock-up made it possible to sit in the cockpit and cabin as well as work out the building sequence and many small construction details. The many changes and improvements I devised in the process made the mock-up well worth the effort. The original design had a flat bottom intended for navigating very shallow water. The final design was changed to a V bottom to provide better performance in choppy seas and move the ballast closer to the centerline.
I purchased a trailer to fit the model, ensuring that there would be no surprises when the finished boat was loaded. Placing the model on the trailer revealed that there would not be enough clearance under the garage door to rig a hinged mast. The cabin roof was lowered as a result without much sacrifice in cabin headroom.
As the building progressed, the stem went through more changes than any other part of the mock-up. Seeing it full size, attached to the boat, and in three dimensions was a distinct advantage over drawings. I added a bowsprit to create more sail area forward and provide the more traditional look of a gaff-rigged sloop.
With most design and construction details worked out, I disassembled the mockup and set the parts aside to be used as patterns, which included truss-like patterns for the planks. The building of the actual boat is under way. The benefits of building a mock-up have provided invaluable experience. I’ve been able to proceed with confidence this second time around knowing that FREEDOM, as the boat will be christened, will meet all expectations. Only her sailing performance remains to be discovered.
Tom Hepp has spent most of his life around boats and water. He is a veteran of the U.S. Navy and Merchant Marine and has worked professionally as a boatbuilder for over 10 years. He spends summers on the coast of Maine and winters near the St Johns River in North East Florida. He designed, made cardboard mockups of, and built two take-apart pirogue-style boats (see “Nesting Boats”) to take in his van during summer vacations.
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