Ready to lay a piece of plywood on top of the nail heads for transferring the frame shape from the loft floor to a pattern.
Lofting is essentially scaling up the three views on the drawing (Profile, Deck Plan and Body Plan) to full size, preferably on a nice flat floor. Books, and many chapters, have been written on the subject. See Howard I. Chapelle’s “Boatbuilding” (W. W. Norton & Co, 1941) or Larry Pardey’s “Details of Classic Boat Construction – The Hull” (W. W. Norton & Co, 1991). It’s an iterative process, going back and forth between the three views, smoothing out lumps in the curves and reconciling one view with the other two. Just to make things even more interesting, all three views are superimposed on top of one another. When you’re done, you have probably corrected small inaccuracies in the drawing and Table of Offsets, which are inevitable because of the scale to which the drawings are made. You have full size lines from which to make patterns. And perhaps most importantly, you will have a much better understanding of how you are going to build her.
In his book “Boatbuilding,” Chapelle says “…there was never a boat built in which too much lofting had been done.” I took this to heart – lofting took 6 months!
(NOTE: For latest work on the boat, check the Deck page.)
Most photos are captioned to explain the process. Click on any photo to enlarge and scroll through the gallery.
Shop floor is concrete, so lofting required a more suitable surface
The concrete slab was leveled with grout. Then two layers of 3/4″ T&G plywood were applied
The first layer was nailed to the slab. The second layer glued and screwed to the first
The seams and defects were filled with Bondo, then all sanded and painted
Bela the barn cat is not so sure about her new floor
On the left, white “story poles” for recording and transferring measurements; on the right, various white pine battens (painted black) for drawing curves
A 32 foot heavy batten was glued up for drawing the sheer line and other gradual curves
Mandi scrapes glue in preparation for planing the long batten
Planing the 32 foot batten required opening the window
Measurements were scaled from the drawing and recorded in the traditional “Table of Offsets”
2nd page of the “Table of Offsets” records the grid dimensions, profile, and other parameters
Linda supervises the grid layout
Mandi was really into lofting!
The “Table of Offsets” defines the boat’s shape, and my existence for the next few months
Laying out heights from the baseline for defining the sheer line
One height measurement at each station defines the sheer. These are then connected with the the long batten to draw it in.
Another view of the sheer line being drawn in using the 32 foot batten
This smaller batten defines the forward profile of the stem
The aft profile of the sternpost drawn in
Plan view of the deck aft
Plan view of the deck forward about to be drawn in
After the Profile Plan is drawn the next step is the Body Plan, which is overlaid on the Profile. A straight edge is fixed at Station 7 to act as the centerline of the Body Plan.
From the “Table”, a half-breadth is marked at each waterline.
Those marks are then connected with a batten to draw the body cross section for each station
The body cross section at Station 2
This batten is for one of the Buttocks aft. Note the relatively flat part of the Buttocks where it passes through the Load Waterline. Chapelle states this flat section is characteristic of good speed
A waterline aft
Another section of waterline aft
Mandi and Ian help with lofting
Photographing the lofting floor was difficult. I needed Tyson Trish!
A detail of the body plan
This is an upper portion of the body plan showing the deck and rail lines
One of the most important results of lofting – a plywood pattern for each of the 29 frames is taken from the body plan. The making and use of these frame patterns is detailed in the “Frames” page.
If you zoom in on the keel portion of the lofting here, you can see a cross section of the rabbet which was drawn in at each station on the keel, stem and sternpost (Click on View full size”, bottom right, then enlarge)
Comments on either the website or the boat will be greatly appreciated. You can contact me (Mike Danesi) at [email protected].
