Paul D Posted February 5, 2006 Report Share Posted February 5, 2006 Not having experienced this problem before ( having had a fixed mount engine ) I was puzzled why this happens - having done some reading up it all makes sense ( I think ) but I would like to make sure I am on the qight track. I noticed that when trimmed in the steering pulls to the right - trimmed out the torque steer goes. My dilema is that the boat handles better trimmed in ( presumably as I have two batteries etc. at the rear of the boat ) and trimmed out it starts porpoising. I have yet to adjust the anode trim tab - so I understand that to reduce the torque steer I need to move the trim anode around to the same way that the boat is steering. So as mine steers to the RHS I should move the trim around to the same side ? Quote Link to comment Share on other sites More sharing options...
blueboatdriver Posted February 5, 2006 Report Share Posted February 5, 2006 Paul, I have exactly the same problem and just haven't got around to messing around with the trim anode (or whatever you call it) yet. If you stand in the middle and steer it's not quite so bad. I've recently put an auxillary 4hp engine on the port side; I thought maybe with the extra weight on that side would help but it hasn't. Simon. Quote Link to comment Share on other sites More sharing options...
Maverick Martin Posted February 5, 2006 Report Share Posted February 5, 2006 Paul I think you will find that to counteract the steering you should adjust the trim tab annode in the opposite direction, so as your engine is trying to throw you to the right adjust your tab to the left or looking down on it clockwise. The tab acts like a rudder, take it steady try a little at a time as a small adjustment has a large effect at speed. Martin Quote Link to comment Share on other sites More sharing options...
Paul D Posted February 5, 2006 Author Report Share Posted February 5, 2006 Martin, That was the direction I was thinking - so a bit to the left will do the job ( and I need it to have a big affect as the pull is quite strong. ) Guess I will have to do more sea trials - oh well Quote Link to comment Share on other sites More sharing options...
Newboy Posted February 6, 2006 Report Share Posted February 6, 2006 Try putting as much weigh as you can to the other side, or starts carrying someone really heavy fishing. Quote Link to comment Share on other sites More sharing options...
duncan Posted February 6, 2006 Report Share Posted February 6, 2006 Paul what you are experienccing is not torque steer - this is experienced by large props turning slowly and creats a lateral thrust on the stern of the boat . what you are experiencing is normally termed prop steer - what it is is important to solutions and why adjusting the trim tab is a last resort! whilst a high speed propelor will create some forces due to rotation (which the trim tab is there to offset) if the prop shaft is not directly in line with the required direction of thrust in the vertical plane it will create a turning moment. As you also want the prop shaft lined up for maximum efficiency neutral steering is a great way of 'feeling' that position. There was a long thread on porposing here about 2 years ago. If you can resolve that with weight distribution do so, setting the boat overly trimmed in, and then compensating with the trim tab, is a poor solution. Finally worth checking that the tab has been set right in the first place - to do this establish the relationship between the top of the engine cowl and the prop shaft (once upon a time they were all flat topped and parallel but you get some fancy cowls now) then when out trim the engine so that the prop shaft is parallel to the water surface (by reference to the cowl) - there should be no prop steer in this position. IF there is then this is the time to play with the tab and start all over again! Good luck Quote Link to comment Share on other sites More sharing options...
Afishionado Posted February 6, 2006 Report Share Posted February 6, 2006 Duncan is right IMO. Another case of all torque and no action Prop steer can be an advantage when manouvering slowly in tight spaces as it will kick the stern in or out without much forward motion, but it is a real problem if you suffer it at speed. If tay the prop rotates clockwise when viewed standing behind the boat, it will walk the Stern to the right thus making the boat steer to the left. A round bilged boat particularly one with a slight taper running aft (transom width smaller than midships width will be most susceptible). Some engine manufacture trim tabs with a larger surface area than the standard ones to help with torque problems. Mad Mike Quote Link to comment Share on other sites More sharing options...
AlderneyBassman Posted February 6, 2006 Report Share Posted February 6, 2006 I had this problem with my Etec90. When travelling at speed I was having to really hold on to the wheel and force it to the left. It got worse when I changed the prop to one which revved higher too. So I consulted the manual which said that the trim tab should be turned to the right This sounded like a type error as surely that would steer me more to the right. So I thought I would see how all the other outboards were set up and guess what.......all were turned to the right So I copied them and the problem has all but gone Gotta be some weird physics going on!!!!! Quote Link to comment Share on other sites More sharing options...
Afishionado Posted February 6, 2006 Report Share Posted February 6, 2006 I had this problem with my Etec90. When travelling at speed I was having to really hold on to the wheel and force it to the left. It got worse when I changed the prop to one which revved higher too. So I consulted the manual which said that the trim tab should be turned to the right This sounded like a type error as surely that would steer me more to the right. So I thought I would see how all the other outboards were set up and guess what.......all were turned to the right So I copied them and the problem has all but gone Gotta be some weird physics going on!!!!! Boats steer from the stern. i.e. It's the end that starts the steering effect, if the stern moves to the left the bow moves to the right and visa versa. So in your case (veiwed standing behind the boat/rudder/o/b ) turning the trim tab so the leading edge went to the right would make the stern of the boat move to the right and thus the bow to the left. The bow of a boat under way always wants to go straight ahead, it's the movement of the stern from side to side as directed by the helm that makes the boat alter course. Mad Mike Quote Link to comment Share on other sites More sharing options...
Paul D Posted February 9, 2006 Author Report Share Posted February 9, 2006 Mike, BUT - The trim tab cannot be turned so the leading edge turns to the right ..... The manual states "turn the rear of the trim tab to the direction of the pull". ( I am presuming the rear of the tab is the trailing edge ). Given that the trim tab cannot be physically turned the other way I shall try as the manual states. I don't think it does behave like a rudder, it is a little aerofoil shape. ( Hence Dick - AlderneyBassman's "weird physics" ). Duncan, I agree with what you are saying and I need to get some weight on the boat moved forward somehow but I apart from the batteries ther is nothing else to move. I will report back with findings after Saturday's trials ! Quote Link to comment Share on other sites More sharing options...
Afishionado Posted February 9, 2006 Report Share Posted February 9, 2006 BUT - The trim tab cannot be turned so the leading edge turns to the right ..... The manual states "turn the rear of the trim tab to the direction of the pull". ( I am presuming the rear of the tab is the trailing edge ). Isn't that just what I said? If you move the rear of the trim tab to the left to correct a left pull then the leading edge of the trim tab must be vectored right. It does act as a mini rudder. it is the same principal as used on aircraft trim tabs. These are adjustable from inside the cockpit and setting them is one of the pre and post take off checks. particularly on small single engined aircraft as these suffer similar (not the same) torque effects from engine/prop rotation. Mad Mike Quote Link to comment Share on other sites More sharing options...
duncan Posted February 9, 2006 Report Share Posted February 9, 2006 back might do as well Paul - either way you are changing the angle of attack off the hull which is causing the porpoising Quote Link to comment Share on other sites More sharing options...
Paul D Posted February 9, 2006 Author Report Share Posted February 9, 2006 Still puzzled to be honest. The trim tab can be in the "neutral" position or can be rotated such that the trailing edge is on the starboard side of the boat - ie. rotated clockwise looking down on it. If this corrects a pull to the RHS I am puzzled as well. Manual is not clear at all as it mentions movig the back of the trim tab - ambiguous as to what the back is. It also mentions moving the tab right or left but mine will only move one way ( and is graduated like this as well. Yours confused ! What I need is a picture of AlderneyBassman's prop/trim tab so I can see exactly how it was adjusted. Any chance ? Quote Link to comment Share on other sites More sharing options...
Paul D Posted February 9, 2006 Author Report Share Posted February 9, 2006 Now less confused. Great article found here - Trim Tab Adjustment This also has loads of tips on adjusting the trim and other things. Quote Link to comment Share on other sites More sharing options...
Paul J Posted February 9, 2006 Report Share Posted February 9, 2006 I will report back with findings after Saturday's trials ! Paul, i'll buddy you in MB PJ Quote Link to comment Share on other sites More sharing options...
Paul D Posted February 9, 2006 Author Report Share Posted February 9, 2006 Paul, That will be great ( hope you will be able to keep up ). Gordon is crewing as well and will probably aim to launch around 8:30 from Mudeford as I want to get back for the football later. cheers Paul Quote Link to comment Share on other sites More sharing options...
AlderneyBassman Posted February 10, 2006 Report Share Posted February 10, 2006 Paul, Sorry can't take a photo at the moment, my boat dries out on spring tides only. Sounds like you've got it sussed though, slacken off the central bolt and rotate the circular plate with trim tab clockwise. Weather looks good tomorrow, I'm off to a wreck on the edge of the hurd deep. Hope you have a successful day Quote Link to comment Share on other sites More sharing options...
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