Boat Balance

[Jango]

This question has probably been asked before, but here goes.

I am building a Fast, almost flat bottom , Mahogany Boat , Powered by a modified Mercruiser Engine. Which side should my steering and controls be to help offset any prop or motor torque? Prop rotation is LH (CCW).

Thanks, Jango

[PAR]

Your control cables will have very little effect on the trim of your boat.

Helm position is usually positioned on the starboard side if the helm person is expected to help out in docking duties. The boat pulls up to a dock and the driver grabs a handful of dock, maybe ties off a line, etc. It's mounted to port if the helm person is not required to help in deck chores and has similar advantages as used in a car on the road, the driver is close to the centerline of the "lane" they're in.

Torque steer tendencies can be compensated for in a few ways, most having little to do with helm or control cable locations. Your local boat repair person can help you setup your engine installation so you have a reasonably straight tracking craft, most of which is trial and error, until you find a sweet spot the boat likes.

[Jango]

Par,Thanks for your reply.

I guess I wasn't clear on my question. What I'm really asking is which side of the Boat should the Driver be, especially if he's the only one in the boat most of the time. I assume the Prop torque and/or Engine Torque will tend to make the boat list and it seems it would be advantages to position the Driver's weight to offset this condition. It should be noted, I am talking about a 380Hp motor turning 5500rpm plus in a 2100 lb boat. Docking the boat is not an issue, since I can use either side of the Dock.

Thank's again for your imput, Jango

[PAR]

It's subject to debate, personally I like the steering station to port, just like a car. The "rules of the road" have us operate the boat in the same fashion, so it makes sense to me. On larger craft the eyes at the helm are looking towards the "action", even if involved in a conversation with crew towards the centerline. If to starboard, your eyes are looking away from the "action" and you can miss something you need to know like shoal or no-wake signs and other markers. I also like the helm to be on the head to head pass side, it tight squeeze situations.

The choice of steering system can help a lot in the effects torque steer can have on the driver. Torque steer is a fact of life in single prop applications. There can be a number of answers, from tabs to skegs. If you feel it's necessary, you can place the helm on the other side of the torque steer, but with the power you're tossing at this boat, you may want to look at other possibilities.

Are you running a straight shaft through a Velvet Drive?

[Jango]

Yes, I am running a straight shaft from a Velvet Drive. According to the HP/Displacement formulas, the Boat should be capable of 75-80MPH.

I believe I found the answer to my question:

Propeller Torque effect (PTE)

"As the prop spins counter-clockwise (as viewed from behind), the engine tends to want to
spin in the opposite direction, due to the drag induced by the blades, as well as the
inertia of prop, crankshaft and flywheel, during acceleration. Imagine if you held the
blades still (resisted their rotation) and pulled the starter rope slowly. Because the
prop cannot turn, the engine will turn instead, albeit in the opposite direction. In a
similar fashion, the prop is to a small extent being "held back", so that force is
absorbed by the tendency of the motor to rotate clockwise. The amount of Propeller Torque
Effect, depends on prop mass, prop diameter, prop pitch, and prop RPM (engine RPM over
Drive ratio), but is basically directly related to available power. More power, means
(unfortunately) more Propeller Torque Effect."



The above says that the Hull will want to rotate Clockwise, which I believe translates to : unbalanced weight, i.e. the Driver, on the Port side.