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had an inclined transom top forward ie longer at the water line..... rudder was soon found to be very inefficient... With the pintle line near 30 degrees of vertical when you ask the rudder to provide lift for turning the boat the lift is inddeed partly TRYING TO LIFT THE STERN OF THE BOAT ....

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I'd suggest that an inclined pivoted rudder is no more trying to lift (or sink) the stern of a boat than your foresail mounted on an inclined forestay is trying to lift it's bow into the sky! (Though I've heard that myth, too!) Nor is the rearward sloping forward edge of your keel trying to sink the whole boat. The force is generated by the FLOW of water (or air), and is (as I understand it) perpendicular to it. Provided that flow is horizontal and the boat upright, the lift is lateral in all three cases.

Imagine an 'individual bit of water' (as it were!) flowing under your boat and along the side of your keel. When it gets to the front edge of the rudder it is deflected to one side, but not (for our intents and purposes) up or down. It does not 'know' that the rudder starts ahead or behind just above and below it. it just continues it's course at its depth of whatever.

Many aircraft have swept back wings. They lift the aircraft up. They do not get torn off trying to fly in a direction perpendicular to their leading edges! This is because the flow of air across them is (like an inclined rudder) not perpendicular to their leading edge, but parallel to the ground and fuselage (or in our case the centre line of the boat and water water surface).

There are, no doubt, effects such as that arising when when a boat is severely pitching, but they are marginal to, and not to be confused with, the essential flows and forces involved.

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