5.2. Vertical Location

Seakeeper Ride’s Controllers must be mounted so that the bottom surface of the Seal Plate (Item Number 2 in Figure 5) aligns with the hull bottom. The goal is to have the Seal Plate acting like an extension of the hull bottom. The Seal Plate’s location is determined by the Transom Plate (Item Number 8 in Figure 5), which is affixed to the transom and adjusted up and down during installation to allow for fine-tuning the location.

Figure 5 – Seakeeper Ride Controller Constituent Parts

1) Blade

2) Seal Plate

3) Rotary Actuator

4) Actuator Plate

5) 5 Degree Wedge Plate

6) 4 Degree Wedge Plate

7) 3 Degree Wedge Plate

8) Transom Plate

The Ride Reference Line (RRL) provides a guideline for the vertical location and orientation of the Seakeeper Ride system while considering many possible hull features. This section of the guide demonstrates how to find the RRL with different hull features.

The RRL is the intersection of the hull bottom and the transom planes, ignoring filleting or radiuses at the intersection. The hull bottom plane can be approximated by holding a long straight edge (3 ft [0.9 m]) flush with the hull bottom, parallel to the centerline. The transom plane can be approximated similarly by holding a short straight edge (6” [0.15 m]) flush with the transom.

Figure 6 – Straight Edges on Hull Bottom and Transom

An example transom with an exaggerated radius is shown below. The RRL is shown in blue and is the intersection of the two straight edges.

For optimal performance, the Seal Plate must be in line with the RRL and the bottom of the hull. The Seal Plate can be above the RRL up to 1/8 in. with negligible effects on system performance. If the Seal plate is more than 1/8 in. above the RRL or below the RRL at all, a significant negative impact on the performance of the system will result.

Figure 8 – Acceptable Vertical Variance

Figure 10 to Figure 13 in the following section show a view from the stern of the vessel looking toward the bow. Label 1 indicates the bottom of the hull, Label 2 indicates the RRL, and Label 3 indicates the outline of the Transom Plate.

Figure 9 – Demonstration of View

Strakes

For hulls with lifting strakes or spray strakes, the strake can be ignored during installation. The RRL, in this case, is defined as the intersection of the hull bottom and transom plane on either side of the strake, as shown below.

Figure 10 – Strakes on Hull Bottom with RRL and Transom Plate Trace

Concave and Convex Deadrise

The Seal Plates (Item Number 2 in Figure 5) have a straight design. Some hulls may have curvature along the deadrise which will cause the Seal Plate to show gaps between the deadrise at either the ends or center of the plate. The following sections describe how to find the RRL in concave and convex deadrise hulls.

Concave Deadrise

For vessels with concave curvature, the Seal Plate should be mounted such that the center of the Seal Plate is flush to the hull bottom and the ends of the Seal Plate are equidistant from the hull bottom (measurement A in the figure below). Measurement A must be 0.5 in. or less. For vessels with concave curvature, the RRL is defined as the tangent to the hull bottom, shown by the blue line.

Figure 11 – Concave Hull Bottom RRL and Transom Plate Trace

Convex Deadrise

For vessels with convex curvature, the ends of the Seal Plate should be mounted flush with the hull bottom with a gap between the center of the Seal Plate and the hull bottom (measurement B in the figure below). Measurement B must be 0.5 in. or less. For vessels with convex curvature, the RRL is defined as the straight line along the transom between inboard and outboard ends of the seal plate’s destination.

Figure 12 – Convex Hull Bottom RRL and Transom Plate Trace

Variable Deadrise

Variable deadrise hulls are those where the running surface has breaks that run longitudinally. Generally, these hulls have decreasing deadrise angle in each successive panel moving outboard from centerline. Seakeeper Ride Controllers are capable of being mounted on variable deadrise hulls, so long as the distance from inboard edge of the Controller to the hull (Dimension A in the figure below) is 0.75 in. (19 mm) or less. This requirement only applies to vertical changes beneath the Controller. In hulls with a variable deadrise, the RRL is the highest portion of the deadrise that the Seakeeper Ride system will cover. See Figure 12 for this position. Because performance may degrade at vertical changes between hull sections greater than 0.75 in. (19 mm) (Dimension A), please reach out to Seakeeper for guidance in this instance.

Figure 13 – Variable Deadrise Hull RRL and Transom Plate Trace