Model - Lining Off Lessons

The Mould coordinates came from my modelling process using DelftShip (CAD software covered in an earlier post). I started with Iain Oughtred's standard full scale mould plan drawings to get 3D coordinates for the Sheer line and outer edge of plank marks. These were then adjusted allowing for the "wedge insert" to expand the hull width and the raising of sheer line. Using Delfship I then faired lines and adjusted the initial station points to get something looking good for body and plan view lines. One further change I made was to pull out the tumblehome in the sheer at the transom. This was partly to provide a bit more width to play with the framing to support twin rudders and centered outboard.

So it was going to be interesting to see how all this translated to a real 3D view of the boat in the form of the moulds. Well it soon became pretty clear to me that the plank lands emerging from this modelling work were not going to give an even and pleasing view of planking. I think the mould shapes are pretty much OK but the positioning of the plank lands needs to be done from scratch. Of course in a full size build we would be sorting out the plank land markings on the moulds before we assemble them on the building jig. But I am not too worried about this, it's all part of lessons along the way. So I rig up a small ribbon tape measure to remark all the plank lands using Iain Oughtred's well thought out method in his Book Chapter 3 - Lining Off. He even has his percentages there for Fulmar which also helps. One good tip - for good visuals of plank lines offset the width of the gunnel before applying the percentages to the girth of each mould.  Here's a pic of the measuring off of new plank lands on the jig. 

In the pic below you can see how the marks have changed from the original markings. You might also note the stem looks pretty rough and I have a bit more to do on this with the help of fairing battens.

The next challenge will be to get the lands marked for the stem and I will need to fit all the battens (with small brass pins this time) to get this sorted. Before doing so I have tried a sheerline, plank 3 and garboard clamp-fitted, to see whether I like the plank lines developing from the new markings and I think so far they look pretty good.

I'm using 6mm square oak battens plus the wider one on the sheer which is sitka spruce. I won't be leaving the battens on for planking - to do so I would need to trim all the moulds (or rebate them) by the batten thickness for this to work.  I have another plan for how to mark out the plank patterns - more later on this.