Severe Torque Steer To Port

[Bondo]

Re: Severe Torque Steer To Port

I have a question.....Regarding the pictures from GKing I can see that if your tab adjustment is at the rear of the tab then what is shown and what you say are true, but if the tab adjustment is at the front of the tab would you not adjust it to the opposit to counter the pull? I don't know that's why I'm asking. I set mine for neutral steer and it didn't change the starboard pull I was experiencing. I have radjusted it to oppose the original set up but was unable to test drive it so see what if any difference there may be. I don't have a power trim so it's kinda tough changing plane while running across the water. My engine is a Force 85HP the boat is a 1989 Spectrum aluminum hull sport/fisher. I tried to balance the weight evenly throughout the boat but that has no effect. This motor really gets this thing up on a suitable plane very fast but it pulls like crazy getting there. Once on plane if I let up on the steering wheel it just swings the boat to the right and I mean right now. Scarey stuff.....HELP!!!!!!!!!!!!!!!!!!!!!

Ayuh,.... The tab pivots in it's center, 'n those pictures explain the Right way to set it....

 

[Another retired guy]

Re: Severe Torque Steer To Port

Welcome to iboats, George!

I used to think exactly the same as you until someone here explained that what changing the trim tab does is change the direction of pressure on the outdrive, not the entire boat. Think about it: when the boat is turning to starboard/right, the outdrive is turned to the right. Moving the trim tab's rear edge to the right pushes the outdrive to port/left.

I've been reading this thread very carefully and have studied the pictures but I still don't understand the physics here. In the above example if the boat is turning to starboard and the tab is adjusted to the right, which you say puts pressure on the drive to port, then surely that would tighten the boats starboard turn?

 

[NYBo]

Re: Severe Torque Steer To Port

I think how it works is the effect on pushing the drive more than offsets the small rudder effect on the boat itself.

 

[Another retired guy]

Re: Severe Torque Steer To Port

I think how it works is the effect on pushing the drive more than offsets the small rudder effect on the boat itself.

Thanks, but I'm going to have to file this under one of life's mysteries. Everyone says it works so it must, but I just don't see how

 

[Oshkosh1]

Re: Severe Torque Steer To Port

It's a "Ronco" adjustment..."Set it and forget it"!

 

[V153]

Re: Severe Torque Steer To Port

Think about it this way: When you're in a canoe or, God forbid, kayak. You paddle on the port side to turn toward stb. Right? Right! Works the same way for OBs & IOs. Focus the thrust to port. Considering it's an IO that would (hopefully) eliminate the possibility the motor's mounted off-center. But might be worth checking?

 

[Another retired guy]

Re: Severe Torque Steer To Port

Think about it this way: When you're in a canoe or, God forbid, kayak. You paddle on the port side to turn toward stb. Right? Right! Works the same way for OBs & IOs. Focus the thrust to port. Considering it's an IO that would (hopefully) eliminate the possibility the motor's mounted off-center. But might be worth checking?

Ah, thank you! I'm seeing it now - in the canoe your body acts as the pivot point twisting the canoe AWAY from the thrust of the paddle. So with an IO the drive will be trying to twist the boat away from the thrust generated by the tab. I think I got it!!!

 

[Oshkosh1]

Re: Severe Torque Steer To Port

Sounds like what we in the Navy called "PFM"...Pure F-N Magic"!

 

[04fxdwgi]

Re: Severe Torque Steer To Port

The tab does not act like a rudder like a normal rudder would, which has a single pivot point, but a rudder for the prop wash against the drive which has a 2nd pivot point on it, the steering.. Works just opposite of what you would think. By moving the tab one way or the other, the thrust from the prop wash "pushes" the drive in the opposite direction, the direction in which the tab is facing, causing the a pressure on the drive steering pivot point (effectively steering in the opposite direction). Very small adjustments can yield large changes.

In this case, though, something seems a little strange, as many adjustments have no effect.

 

[Rokomo]

Here's another question-Do trim tab anodes have to be shaped like a little upside down fin ? I see several of them available that are simple round discs or half-spherical ones. If the prop and fin annode aren't playing nice together why couldn't I simply switch to a flat or rounded annode ?