Wednesday, April 22, 2015

Modified "next boat" design

After re-considering the boat lines plan I posted a few months ago, I decided it could be improved.  The aft portion seemed too dominant, so I added more taper to the deck and topsides, and gave the transom more of a forward slant.  That aft section is now proportionally smaller.  My goal in developable designs has been always to show that a design that can be sheathed in plywood doesn't have to look "boxy", and I think that has been achieved.  Of course, a developable design can also be sheathed by almost any other technique or material.  There are no sharp curves which would require extra thin sheathing materials; 6mm ply will bend to

any of these curves.

An outboard engine of 60-90 hp should give 30-40 mph at the altitude here (6000') and somewhat faster speeds near sea level.  I have wondered about installing an inboard engine, revising the cockpit, and increasing the deadrise to 14 degrees (due to an anticipated greater displacement).  An inboard would have that authentic runabout aura; the deep rumbling exhaust; the weight and power to knife through waves, but I can't forget the many advantages of an outboard.

We will be busy this summer on some significant boating trips: the Grand Tetons in Wyoming, Glacier National Park in Montana, and Coeur dAlene, Idaho.  Our current boat is well-suited for the trip.  The ample freeboard and raised foredeck provide weather protection.  A newer boat is only a dream for now; however, I hope to build a scaled model this winter.

Because the design is created mathematically (geometry, algebra, trigonometry), the design is initially a table of offsets for a full-size hull. To make a model, the dimensions need to be scaled down and then plotted on paper.  Engineering paper makes the task easier for a model.  Full-size patterns require much larger sheets of strong, stiff paper (rosin paper) and careful plotting.