Wednesday, March 26, 2014

The new boat looks complete.

Finally, the windshield is completed.  My wife encouraged me to have a metal windshield frame, but now that it is done, she says that the wood looks better than a metal frame.  But she thinks that it should have been taller.  I considered the height, angle, and fore-aft placement of the windshield when designing it; both from an esthetic and functional aspect.  Unless you make the windshield quite tall, the upper edge of the frame is in your field of vision.  Tall would have not fit the esthetic I desired; most of the time I expect to be viewing ahead over the top edge of the windshield.  I had an extra cushion made for the captain's seat to raise the line-of-sight.

And the upholstery is completed.  The seats are separately removable, allowing access to the fuel tank under the front seats and access to the battery and storage behind the rear seats.  A person could do their own upholstery, but it is not an area I have any expertise in; so I contracted it out.  And the bimini top with full enclosure panels is complete as well as a travel cover.  Looking over the amount of detail in all those panels, the variety of materials required, and the expertise involved, I am glad to have it done professionally.  Bringing the boat home, I had to drive through a spring snow storm; the boat and cover were wet and dirty when I arrived at our garage.

The boat is still not done, but we are in the home stretch.  I need to bundle and strap the control leads, electrical wiring, and fuel lines in place.  There is one slight scratch in the paint to touch up.  I need to get the boat inspected by the State of Colorado to get a Hull Identification Number (HIN) for licensing.  Then we will be on the water.  Here in Colorado, the scenic mountain lakes aren't warm enough for boating until June.  We may end up towing the boat to lower altitudes for a longer boating season.


Saturday, March 01, 2014

Why I use rosin paper

I recently read an article concerning conversion of developable surfaces into flat sheet patterns.  In previous posts, I really haven't discussed how to do that using a mathematical approach.  It can be done; I used this approach when I built a 20 1/2 foot sharpie design many years ago.  The only reason I haven't expanded on the subject is that, once I have a hull framework constructed, it is easier to simply make a stiff rosin paper pattern by laying a roll of paper over the framework and tracing the edges.  But, for those who do not want to construct a full hull framework, being able to go directly to laying out patterns for sheathing may be worthwhile.

The method utilizes what may be best called external triangulation.  It is external because we are not calculating distances just between points within the design surface but instead are using our conic apex, located at some distance from the surface borders, as a reference point for many measurements.  Using the coordinates of the apex in conic development and the coordinates of consecutive points along the chine of the hull, we can calculate the length of radiating (ruling) lines emanating from that apex.  The chine of the hull is created using a mathematical equation; thus, by integrating this equation (the power of calculus) we can find an equation [it is a long but standard equation] to calculate the distance along the curve between any two designated points on the chine.  Those points along the chine provide the third distance in creating a series of triangles which, when plotted in sequence, will give us the shape of the developed surface.  However, part of the chine curvature may be contained within the outline of the surface itself; thus the sequential points of the chine are best first plotted along a fair batten which is then laid in place and connected to the ruling lines from the apex.  For parallel projections, instead of an apex, we would be plotting parallel ruling lines.  If you calculate the distance between two sets of coordinates in a developed surface NOT connected by a ruling (straight) line by using simply the formula square root of (x squared plus y squared plus z squared), the distance will be distorted by lack of consideration for the curvature present.

In conclusion, yes, I can create flat surface patterns for sheathing.  But is it really worth the effort when a roll of rosin paper will give me the same thing?