How much rudder trim is necessary on ProStar 190

[swbca]

The 190TT I bought last October was used by a trick skier . . never used for slalom except of its first year as promo boat. The steering bias is light at 20mph but heavy at 34 . . . and the boat goes into a death spiral in 2 seconds if you lose grip on the wheel. (we don't do that much).

 

Anything I should know about decreasing the trim ? Any issues with the fasteners after 18 years ?

[eyepeeler]

Looks like perfectly set rudder torque.

[swbca]

@eyepeeler If the boat is never used for towing at low speeds, is there a reason not to reduce the steering bias at slalom speeds ?

 

Separate subject . . Safety. . after I posted this question I tested what actually happens if you let go of the ProStar 190 wheel at speed. The actual time for the boat to turn near full-lock-right is less than 2 seconds. I know some can make a joke about someone else talking about safety but this could be catastrophic. If driver loses all control, the front seat passengers would be pinned to the port side of the boat and not be able to help anytime soon. I wouldn't want to be the skier . . I had a friend whose child was killed by a boat she was driving . . . she was thrown out of a Boston Whaler with a 40hp engine when it hit a large wave. It turned by itself circling her several times before it hit her.

 

Are the current model ski boats the same ? I am into having all risks being calculated . . like teaching your kids its better to jump out the side of a boat at speed than jumping out the front. When our parents weren't around, we would jump out the side of our Ski Nautique at 40mph. We calculated to make sure our entry angle into the water wouldn't hurt much.

 

Then back to ProStar steering . . this seems to border on a risk that hasn't been well considered. I am not a big sissy . . I stopped racing cars last year so I could afford to buy a boat. It obvious no land vehicle designed to act like that would ever happen.

[Alberto Soares]

Always wear the kill switch. You will need some rudder pressure for a good drive, how much pressure it is a personal preference.

[BrennanKMN]

I'd set it up based on primary use.

 

My boat is almost exclusively used in the course, the only time it's not pulling a skier is going to and from the course and boat launch. Thus I prefer a strong rudder load.

 

If my boat was an open water family ski boat I'd prefer it setup much different. I agree, the strong rudder load could be dangerous for newer or less focused drivers.

[MISkier]

I thought that the prop rotation would make the boat turn quickly anyway, even if the rudder were neutral. Prop rotation is one thing that differs from a land vehicle and why a boat probably isn't designed to continue on a straight path when the wheel is released. You might be able to offset/mute the effect of prop rotation with extra compensating fins, etc. But, I think a rudder that moves will always be somewhat affected by the prop rotation when nobody is holding the wheel.

 

I think the amount of rudder torque you want is just enough for you to not need to constantly move the wheel from side to side and not enough that you feel tired from resisting the wheel for a few slalom sets. If you are constantly moving the wheel each way a lot to keep the boat straight, it is too neutral. If you get tired of holding the wheel and resisting that force or otherwise think it is substantial effort for you to do so, there is too much torque on the rudder.

[eyepeeler]

@swbca You should start to feel rudder torque at about 23-24 mph,

 

[swc5150]

My boat was supposedly set up by a pro skier back in the day, and it has no rudder torque, but steering feels tight and true. I've never driven a DD set up like it before. I can take my hands off the wheel at slalom speed, yet it tracks great with no slop.

[LeonL]

ALMOST every slalom ski boat will turn hard to its natural direction if you let go of the wheel. So, don't do that! I think that @MISkier hits it on the head. Another note, it's pretty hard to "ungrind" a rudder. In other words it's hard to take out rudder torque.

[MDB1056]

what year is the boat? 03?

[jjackkrash]

I like some tug on the wheel; the boat feels like it is floating and imprecise if there is no torque steer at slalom speeds. IMO.

[swbca]

@LeonL @MDB1056 Its a 2004TT with an adjustable trim on the rudder. Maybe the trim was only on the TT model . . I'm not sure.

 

I thought rudder torque was to keep the steering up against 1 side of the "free-play" in the steering components, so in effect there is no free play from the steering wheel to the rudder. The high torque on my boat is way beyond that.

 

But I have the impression from some comments that rudder torque serves some other function beyond killing the free-play in the steering components. Is that so ?

 

[MISkier]

A certain amount of rudder torque will aid a driver in countersteering and blocking a skier without degrading the path of the boat through the course. If it's too neutral, it is less effective to help keep a good rhythm with the skier. Driver's will let the torque adjust the boat one way (by slightly releasing pressure on the wheel) and then use their steering movement the other way to maintain the correct line while ensuring the skier load is properly resisted and results in a good path. It helps make the adjustments either way more subtle and more balanced.

[Dacon62]

Is that a custom built tab on a Malibu Boats rudder?

Should be able to back off the tab bolts and reposition the tab slightly toward the drivers/port direction to reduce the pull to port.

[swbca]

@MISkier I get that ! When driving through the course, rather than adjusting left-right with symmetrical action from both hands, you are in affect steering with a variable force from one hand, while the other hand and the rudder torque provide a relatively constant counter force.

 

Do all the boats now turn the prop the same way ? Back in the day I had left and right screw boats switching from Correct Craft to Master Craft. From @MISkier 's description, a tournament driver would have to learn 2 ways to drive slalom if there were both Left and Right screw boats in use.

[swbca]

@Dacon62 The Rudder picture is the original factory setup on a 2004 ProStar TT model.

 

[MISkier]

@swbca, the boats have two different prop rotations. Drivers do have to learn to drive for both setups and the opposite rudder torque. Nautique turns opposite from Malibu and MasterCraft (and probably most other boats).

[2001PS190]

Swbca, did you ever get a good answer? I’m having similar problems. The higher speed I am going the more aggressively it turns. I don’t have to fight to hold it straight and it performs great. I’ve had the boat about 14 years and I don’t use it near as much as I use to but I don’t remember it turning like this. Mine is a 2001 Prostar 190

[swbca]

The rudders that came with the boats may not all be the same. On 2004 TT, the trim tab on the rudder was designed with a fixed angle. It was deceiving because the two bolt holes in tab were larger at the rear face to accommodate a change in angle but the contact face of the rudder and the tab prevented any adjustment. I incrementally ground down the contact face of trim tab until it would seat with less angle. I currently takes less pressure to hold the boat straight at 34. It still turns to full-lock right in 2 seconds if the drive loses grip. This makes the case for the safety kill switch attached to the wrist, but it never happens when the driver is changing rope length after every pass.