How to Locate a Water Line When Painting the Bottom of a Boat

If you can read blueprints, you can locate your boat's water line.

Being able to locate the designer's designated water line (DWL) on the hull of your boat can become an important part of your blueprint-reading skill. The key to locating the waterline is being able to find the DWL on the designer's scantling drawings. Sometimes called the "lofting drawings", these drawings are available from the designer or builder. Once you determine a single dimension, you only have to transfer the dimension to the hull of your boat.

Things You'll Need

• Scantling drawing, plan view and waterlines
• Draftsman's compass
• Measuring tape
• Level
• Carpenter's square
• Grease pencil

Instructions

1. Look at the plan view of your vessel's hull and find the horizontal line marked DWL for "designated water line".

2. Use the draftsman's compass to measure the distance from the centerline of the boat to the outside of the hull along the DWL by placing the point of one leg of the compass at the side of the hull on the DWL and the point of the other leg on the level of the DWL where it intersects the centerline of the boat.

3. Compare the distance between the legs of the draftsman's compass to the scale of the plan. Set the point of one leg of the compass on the "0" point of the scale and set the point of the remaining leg of the compass on the scale. Read the distance from the scale and record the measurement.

4. Use a measuring tape to measure outward from the centerline of the bottom of the boat, a distance equal to the measurement from the centerline to the outside of the hull along the DWL. Use a level to ensure that the measuring tape is level. At the correct distance from the centerline, set the right angle of the carpenter's square so that the arms of the square make contact with the level and the hull. Mark the location of the DWL on the hull with a grease pencil.

References

• Dudley Dix Yacht Design: The Case for Lofting