The first step is to lay out a series of vertical lines marking the stations. This is straight forward but they have to be parallel and at right angles to an arbitrary baseline at the edge of the lofting floor. The next step is to draw the waterlines where the elevation of the boat will be. These must be parallel to the baseline and the easiest way to do this is to mark their positions on a "tick stick" (lots of these needed). Then place one end of the tick stick against a temporary batten nailed along the baseline along the baseline and transfer the tick marks to the floor. Repeat this in several locations and then join the tick marks with a long straightedge. This rectangular grid is completed by drawing in the centre line and buttocks in the plan view of the boat. I drew the grid with a red ballpoint pen to make it permanent and clearly visible.
That's just about the end of the straight lines, it's all curves from now on. The first step is to draw the outline of the boat in both elevation and plan. These lines are taken from the table of offsets. Starting with the sheer line in the elevation the points are marked at each station and then a batten 6 metres long is put in place in a fair curve through all the points. It didn't meet them and there was a lot of eyeballing and adjusting until the curve looked right. This line was marked with a black ballpoint pen as it will not change. here's a photo of the batten in place. Forward end of the boat at the far end of the shed.
Two more lines are drawn on the elevation, the rabbet line and the profile of the keel. The sheerline is drawn on the plan view. These three lines are taken from the table of offsets and carefully faired. Again these lines are permanent and drawn in black ball point pen. While doing this I broke the 6 metre long batten trying to fair one of the sharper curves and had to make another thinner one. I ended up with quite a selection of wooden and plastic battens to deal with the different curves. There is also a pile of broken bits!
The body plan or sections of the boat are next. The sheer line is transferred from the elevation and plan views using tick sticks to transfer the heights and widths; using tick sticks is more reliable than measuring with a tape or ruler because you don't have to remember dimensions as you stand up, walk and kneel down! Again, the sheerline is permanent and is inked in.
For each station the widths at each waterline are marked off from the table of offsets and then joined by a fair curve using a batten.
The above is one of the gadgets I made to hold the battens in place; its a bent nail in in the end of a piece of timber used with a paver to hold it in place. The blue thing is a bucket that I kept the gadgets in so I didn't kneel or step on the business end of the nail.
I'm not going to attempt to describe the whole process of fairing the lines of the boat because it would take too long but here is how it begins. Using a tick stick the widths of the boat at each station are taken off the body plan for one of the waterlines and transferred to the plan view of the boat using a tick stick. The marks in the plan view are faired using a long batten. Any differences between the fair line and the tick stick are correct on the body plan and the affected sections are adjusted. This process continues until all the waterlines, buttocks and diagonals are drawn. All discrepancies are taken back to the sections on the body plan and each change to these sections may result in changes to previously faired lines. This process took several days and a lot of correcting fluid before I was happy with the lines on the floor.
If anyone is starting on the lofting of a boat I recommend that you find a copy of the Gougeon Brothers book on Boat Construction. It will guide you step by step through the whole process.
All the sections drawn so far show the outside of the hull but the moulds that the boat is built over define the inside of the hull. The next step is to subtract the thickness of the planking from the section lines. Because the planking lies over the moulds at an angle in most places on the hull simply subtracting the plank thickness will introduce errors. The amount subtracted has to be adjusted to allow for the angle or bevel at any point on the hull. To do this "bevel sticks" are needed and to create these a bevel board must be made. Here it is.
Looks easy enough to make but it took about 3 hours to do. It has to be made accurately and dividing a 90 degree arc into 1 degree intervals isn't so simple!
Once it is complete the bevel sticks are made, they have to be the exact width of the finished planking, as thin as possible and as long as the spacing between stations. They are tacked onto the bevel board at a distance from the vertical axis corresponding to the station spacing. Then they are marked every degree numbering every 5th mark.
The sticks are then used to measure the bevel angle between the sections on the body plan and then to mark off the effective thickness of the planking at that point. The length of the angled lines across the stick represents the effective thickness of the plank at that angle. This adjustment is made as many times as is necessary on each station line to allow a fair curve to be drawn.
This is the completed body plan, outside hull lines in black, inside hull lines in green. Is it worth the effort of allowing for the bevel rather than simply taking off the plank thickness? I think so, Everywhere on this hull the effective planking thickness was more than the actual 15mm, in a few places 25mm had to be subtract. Having taken the trouble to fair all the lines in seems counter productive to make them unfair by making the wrong allowance for planking.
The next job is to determine the bevel angles and allow for the planking around the stem of the boat and along the keel. More reading of the Gougeon book and another day of crawling about on hands and knees!
