Any Idea?

[RUI]

1:why Would A 29' Power Boat Single Engine Inboard,with Keel Fall From Trim When Turning Starboard Also With A Rooster Tail.
With A Right Hand Prop
2:when Changing To A Left Hand Prop It Does The Same To The Opposite Side.
3:should The Turning Radii Be Different Turning Port To Starboard?
It Is Funny That When Doing #1 That Raddii Is Twice As Large As The Other Side.

[ClarkT]

Engine rotation acts as gyroscope. Enabling turn in one direction...inhibiting in the other direction.

This is why motorcycles turn well to the left, but are harder to turn to the right. If you ever need to run from a motorcycle cop (god help you) make lots of right turns.

[ClarkT]

I don't ride motorcycles, so I only know this by being told.

Also, if the cop is riding a Harley, all bets are off, their engine is aligned differently.

[SailDesign]

The motorcycle thing only works if the cop is riding a BMW or similar, where the crank axis is longitudinal. Most other bikes have a transverse crank, including Harleys.
And on a Bimmer, they'll still catch you.

Steve

[gonzo]

Do you mean it falls off plane? That is normal because at tight turns the boat looses speed.

Originally Posted by gonzo

Do you mean it falls off plane? That is normal because at tight turns the boat looses speed.

the thing i am mostly concerned about is why on the tight turn side does the boat turn normal meaning not loosing plane. When turning the other direction the boat noticeable drop 2-3 degrees and looses speed.

[SailDesign]

You may be experiencing a case where prop-walk is aiding your turn in one direction, and hindering it in the other.
How to fix prop-walk? Good question.....

Steve

[gonzo]

Most rudders are offset to allow the propeller shaft to be removed. This will make a boat turn differently.

[sndnlp]

This feedback relates to the theories some have posted about motorcycle right turns vs left turns. The differences between various manufacturers of motorcycles and the engine orientations has very little to do with the more difficult right turn phenomenon. The majority of this gyroscopic influence is born out of the front wheel spinning, which has a much larger radius of gyration and moment of inertia.

[marshmat]

RUI, the effect you describe- if I read your post correctly- is common to all single-screw inboards.

There are two main factors at work here: (1) Inboard propeller shafts are not parallel to the direction of travel, thus the prop is at an angle; (2) The bottom of the prop is farther underwater than the top of the prop.

The combination of these factors (through some slightly ugly mathematics) results in the prop producing a sideways thrust as well as a longitudinal thrust. This side thrust pushes the stern sideways a bit; normally you correct by steering the other way slightly. When turning, the side thrust will help you in one direction and work against you if you turn the other way, so you get a different turning radius to port than to starboard.

If the prop is correctly sized, you should not have problems staying on plane unless you are turning extremely tightly. If, when driving normally, you consistently fall off plane to one side, have a good prop dealer take a look- if a prop change doesn't help, you might want to look into getting trim tabs. Or you simply might not be going fast enough to be fully on plane- planing hulls do not operate well at semi-displacement speeds.

[cyclops]

My overpowered 19' bowrider with a 5.0 L 220 hp has similar high speed and docking habits. Excessive prop and torque.