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ContinuousWave: Whaler Performance
List at Planing Speed
|Author||Topic: List at Planing Speed|
posted 07-10-2001 04:19 PM ET (US)
Last weekend my Revenge V-22 was listing to port at planing speed. We have tried to balance everyone to equal sides of the boat, but it still isn't working. With six people on board, I have to have four of them on the starboard side to keep it level. Any ideas what is causing this? I do not have trim tabs. Could gas in the tank be shifting? It happens no matter which direction relative to the wind and waves I go. It is pretty pronounced, but only once on plane.
posted 07-10-2001 04:30 PM ET (US)
Propeller torque thats all. Put more weight on the starboard side or get trim tabs.
posted 07-11-2001 09:02 AM ET (US)
I was glad to see your post. I experience the same condition on my '80 17' with a 70 hp johnson. For some reason I thought there was some adjustment you could make on the motor to help equalize the effects of torque. Kelly
posted 07-11-2001 11:37 AM ET (US)
If your motor is pulling to a side, you are constantly countersteering the effect. That is where the list is coming from.
|Tom W Clark||
posted 07-11-2001 11:43 AM ET (US)
Listing can be caused by many different things, propeller torque among them.
You say this listing happened last weekend when you ran the boat. Does this mean that it hasn't happened before? If so, this would suggest some condition peculiar to last weekend's trip and would tend to rule out propeller torque.
Let's start with the most obvious causes of listing: weight. If the boat is floating level at rest but listing while on plane then weight distribution is not the problem (though it may be the answer). Gas in the tank has nothing to do with your problem.
Propeller torque: this will tend to cause a single engine boat to list to Port, but in reality a 22 on plane will have almost no perceptible list from the propeller torque. A 17 might. The trim tab (the small fin behind the prop used for canceling out steering torque caused by the propeller) on the lower unit comes into play here. If this trim is not adjusted so the steering effort is neutral at the most common trim angle you use for the motor (I'm talking about "trim and tilt" type trim now) then it may force you to steer the motor a bit to Port or Starboard in order to correct for it. This will cause the boat to list. It also raises an interesting question: If you have hydraulic or NFB steering, can the steering trim be way out of whack and not be felt at the helm?
As a corollary to the above, the trim angle of the motor itself will cause what is known as P-factor, the asymmetrical distribution of thrust relative to the prop shaft (axis of rotation). As the motor is trimmed out the prop blade on the Starboard side will have a reduced angle of attack on the down swing and the blade on the Port side will have an increased angle of attack on the up swing producing more thrust and causing "torque steer". I noticed this on my Outrage and Montauks when I would trim all the way out for high speed runs. There would be quite a bit of torque steer and the helm would have to be turned to compensate for it thus causing the boat to list a wee bit.
A cross wind in any form will have a much larger effect on listing than propeller torque or torque steer. Outboard powered Whalers in particular will tend to be blown down wind and consequently the boat must be steered into the wind to hold a straight course. This always causes the boat to list into the wind.
Transom mounted transducers can often act as mini trim tabs and if not adjusted properly will through the boat off an even keel. Sometimes moving the transducer from one side to the other will alleviate a listing problem.
Lastly, there may be something particular to your hull that causes it to list. I experienced an annoying list on my Outrage 18 which I was never fully able to eliminate. It was not a weight distribution problem, nor a propeller torque problem. If the boat floated level it would run with a list which I generally adjusted for with passengers and gear. I also played around with my transducer locations and improved it somewhat. I have been out in identical Outrages with the same power and not experienced the listing so I know it was something about my boat. I checked to make sure the motor was mounted on centerline (it was), and I was never able to completely get rid of the list. But I was able to compensate for it and run it level most of the time.
posted 07-11-2001 01:28 PM ET (US)
Thanks for the replies! Truth is, I am just getting used to the boat after a lot of work being done to it. I had hydraulic steering put in, and the motor rebuilt (couldn't wait for the new engines to arrive- would have missed out on summer!). As such, the torque from the motor is way different than I'm used to, as well as the steering. What is the steering trim that Mr. Clark is referring to? Is that an adjustment that can be made that might help solve the problem? Can that be the solution to the countersteering Bigshot is talking about? I hope to take her out tonight to do some more re-aquainting with the new parts.
posted 07-11-2001 04:07 PM ET (US)
Here's a bit of additional info on Tom Clark's transducer advice; this is from my SS15 owner's manual:
"Mount the transducer on the port side of the transom. The transducer in most cases will act as a mini-trim tab and can affect hull trim. When mounted on the port side, particularly on 17 foot models, the transducer will counteract port listing tendencies from propeller torque, providing better hull trim."
posted 07-11-2001 04:34 PM ET (US)
What about the motor level, port-to-starboard? Could a minor mis-alignment here cause issues? When I rigged my Tohatsu via setback brackets, I was careful to align all components. Comments?
|Tom W Clark||
posted 07-11-2001 08:50 PM ET (US)
The steering trim I am referring to is the "trim tab" or "water rudder" that is bolted to the underside of the cavitation plate directly behind the propeller. It is there to be adjusted to counteract the steering torque. You simply loosen it up with the appropriate size socket wrench, move it and retighten it.
It is interesting to note that you have new hydraulic steering. It may be that the "rudder" is misadjusted and causing a lot of torque steer which you cannot feel because of the no-feedback quality of the hydraulic steering.
You say the boat is listing to Port. Try moving the trailing edge of the rudder to Port. I suspect it may now be to Starboard. Run the boat and see if it makes a difference.
SuburbanBoy, it's good that you paid attention to aligning your new motor but I really doubt that caddis' motor could possibly be so far off center or out of plumb that it would make any difference.
sport15er, the quote from your BW owner's manual is verbatim, to same as what they wrote in their manuals back in the and 70's and 80's when transducer design was somewhat more primitive. Nowadays a lot of good transducers are much smaller and of the surface piercing design which I believe exerts less influence on trim. But none the less it's probably a good idea to get the transducer adjusted as close to perfection as possible and mounting it to Port may have the additional benefit of reducing the potential for cavitation or ventilation of the prop by allowing "cleaner" or less disturbed water to flow out from under the hull on the Starboard side where the prop blade is on the down swing and more likely to grab air and ventilate.
posted 07-11-2001 10:18 PM ET (US)
Tom Clark writes:
> A cross wind in any form will have a much
> larger effect on listing than propeller
> torque or torque steer. Outboard powered
> Whalers in particular will tend to be
> blown down wind and consequently the
> boat must be steered into the wind
> to hold a straight course. This always
> causes the boat to list into the wind.
I have observed this effect and I had not deduced its source. It was quite enigmatic that the boat should lean into the wind, and I was curious what mechanism was causing this.
I think your explanation is a good one and accounts for this phenomenon quite nicely!
posted 07-11-2001 10:27 PM ET (US)
What Clark says is sooo true.
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