Re: Unlevel plane on 1989 Bayliner Capri
Chick;
There is no complicated issue here, and it has been addressed many times. With any "V" hull boat the tendency to list to port when cruising on plane is possible. It is more likely when the bow is too far down as this drives the most severe part of the "V" into the water. Like a teeter totter the boat will be riding on the keel and any side to side force will push it over to one side (list). The prop torque (resistance of the prop as it rotate in the water) will be opposite the rotation of the prop. Since the prop rotates clockwise the boat tries to unwind counter clockwise (list to port).
Trimming the motor out to a more vertical position will bring the bow up and allow the boat to ride more toward the back where the "V" is more shallow. This provides more resistance to the prop torque. Remember that the transom is angled (when looking at it from the side) about 10 to 12 degrees so that the motor can be "trimmed" (tilted) down under the boat to help the prop lift the stern when accelerating to plane.
This does not mean that the motor trim should remain in this position, and in fact this is the least efficient position. The propeller should be perpendicular to the surface of the water.
When a hydrofoil (doel-fin) is used to assist the boat to plain it does so by creating more running surface to lift the stern (like a single trim tab in the center of the hull). This has some effect which is dependent on size. However, because of the wing shape and the fact that it is fixed (not flexible) it increases the lift more and more as the speed of the boat increases.
This extra lift will raise the stern and push the bow down, and in addition to the motor trim (when in the down position) you end up with two devices pushing the bow in the water.
The results are what you would expect -
1) Since the boat is now riding on the most severe part of the "V" the tendency to list to port is more (causes a torque list).
2) The top speed is inhibited
3) The boat lays over too much in turns
4) Fuel economy is reduced
5) the ride is uncomfortable
Solution -
1) remove the hydrofoil
2) trim the motor out
A) If the boat does not plane easily, add trim tabs.
B) If the boat porpoises when trimmed out, add trim tabs
Trim tabs become an extension of the hull which can be adjusted (or self adjust) to change the hull design and compensate for the various conditions (speed, attitude, load, etc.) Because they are not fixed the issues of listing, incorrect running attitude, and handling are avoided. They expand the efficiency of the hull.
