Determining the Sheer

Introduction

When fitting more strakes from the garboard strake up the sides of the boat at a certain moment you will encounter sloping lines everywhere (image 1). At that moment the correct line for the boat has to be determined. Three aspects are important for this:

  1. If you let the ideal line sag slightly fore and aft then you will also get differences in beam. Somewhere in between you have to find a good compromise.
  2. The top line of the boat must have a nice ‘sheer’, a nice line from forward to aft, whereby the bow is always higher than the stern.
  3. For boats from Zeeland the rubbing strake must have a small S-bend from the stern going forward, which is slightly more or less depending on the type of boat.

These three aspects must be in harmony with each other as a combination of lines. This is entirely visual work. No rules can be provided for this. Those ‘in the know’ can even tell you which yard built a boat by looking at its lines.

Once the lines have been determined for the ‘sheer’ of the boat the wash strake can be fitted and you will have a complete hull. This is then followed by finishing with extra frames, the bulkheads and the decks.

Procedure

Proceed as follows to determine the sheer of the boat:

  • A traditional method for determining the ‘ideal line’ – a method that is still used at many smaller yards– is based on a small team working together. The person who is responsible for the line places the laths at the required height with the help of his assistant (in the case of the ‘Nieuwe Zorg’ PVC cable ducts with adjustable plywood brackets were used (image 14), but traditionally this was done using thin laths). If you use laths then it is preferred to use Oregon pine clear and better, in other words the timber left over after making spars. Make sure that the grain runs nicely with the length and that there are no knots. Check that the line is as required (image 15) and then leave the laths in position for a few days.

  • The team (for example 3 people) then returns to take another look at the line. The first person looks, evaluates and says nothing (image 16). The second looks, evaluates and also says nothing. The third person looks and expresses his opinion (image 17). If they are not all in agreement then you change the height of the lath line. The same procedure is followed to look again and re-evaluate for as long as it takes until everyone is in agreement (image 18). In this way you obtain a boat with a nice line and that gives a great deal of satisfaction.

  • Apprentice boat builders also work in the same way in a team. In this way they learn to think properly about building boats. And that is good for their feeling of self-esteem. At large yards it is the manager who determines the lines, as shown on the drawing, and occasionally that contains an error ...
 
Choose Language

Tools Required

  • Chipboard screws
  • Screwdriver

Materials Required

  • Long, thin laths or cable duct
  • Small sheets of plywood