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Post by moonshadow on Jul 14, 2020 15:43:40 GMT
Here is an issue that I need to explore. When my saildrive equipped SO469 is under power if I let go of the wheel it will gradually achieve full right rudder and the boat turns hard to Stb. Totally a motoring issue. Under sail all is normal and when trimmed the boat will sail with no wheel input in a nice straight line with rudder neutral. And gently holding the wheel still under motor the boat goes straight with small input to hold it still. Since the saildrive and motor are bolted together as a unit I don’t think there is a drive alignment issue. I am wondering if my engine has shifted on its mounts. I’m thinking the prop wash hits the port side of the rudder and gradually pushed it over. Has anyone seen a motor cause this if incorrectly aligned in the boat? How to measure and fix it? Any other likely cause that needs to be looked at? Thank you all for your input.
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Post by jy51 on Jul 14, 2020 15:48:43 GMT
Have you considered that the prop kick caused by the rotation of the propeller, might pull the boat to one side.
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Post by moonshadow on Jul 14, 2020 21:22:02 GMT
I did consider that the prop was was just odd due to the saildrive. But after talking with other owners this is still not normal. Another 469 owner specifically tested after we spoke and he is able to let go of the wheel under power with no significant turning. Thanks.
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Post by moonshadow on Jul 14, 2020 21:22:52 GMT
And is is easy to see that it is the rudder turning first after a few seconds and then the boat turns.
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Post by zaphod on Jul 14, 2020 21:23:40 GMT
Have you considered that the prop kick caused by the rotation of the propeller, might pull the boat to one side. Propwalk wouldn't cause the rudder to physically turn hard over. I have shaft drive not saildrive, but my boat "pulls" slightly to one side, but nothing as extreme as you describe
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Post by Charlie-Bravo on Jul 15, 2020 8:23:26 GMT
it could be something has grown or attached its self to the starboard side of your hull increasing drag on that side, as you sail your sail balance will be the deciding factor on direction and how neutral the helm feels , under motor alone where you stash the beer, spare anchor etc can also effect the trim, our boat being smaller has needed quite a few heavy items like life raft etc to be on the stub side to get her balanced , When not on your boat does she lean a little to starboard ? Has this steerage issue always been the case or is it a new phenomena? CB
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Post by NZL50505 on Jul 15, 2020 9:33:31 GMT
Most boats pull to one side under engine due to prop walk. Usually at low speeds the effect is small and if you take your hands off the wheel it might be 2-3 mins before it finally starts to turn. At higher speeds the turning effect is almost immediate and stronger. And once the turn starts it tends to accelerate and yes it can result in the rudder going over full lock and boat into a tight turn.
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Post by moonshadow on Jul 15, 2020 12:37:30 GMT
I bought this boat about two years ago and it is not about 5 years old. This is the only boat with saildrive that I have spent time on. The turning of the rudder has been apparent since I bought the boat and I attributed this to the saildrive. But I recently talked with another SO469 saildrive boat owner that did not have this effect. So now I am wondering if sometimes this is compensated for during installation. I know that small airplanes have the engine mounted at a small angle to compensate for similar behavior and I’m wondering if the engine should be a few degrees off center. Is there anyone at Jeanneau that answers questions on these types of issues?
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Post by Zanshin on Jul 15, 2020 15:05:43 GMT
I am not certain that this is due to problems with the boat.
I think the effect is the same as that experienced when flying a propeller driven aircraft. There are several reasons why most aircraft pull to the left - engine torque (not present on boats), P-factor (present), precession (not present on boats) and swirling slipstream (present). I think that the latter might be hitting the rudder at just the right position to exacerbate the turning moment.
The prop blade is deeper in the water on a saildrive than with a standard shaft, so the "slipstream" is going to be more pronounced.
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Post by moonshadow on Jul 15, 2020 20:58:47 GMT
Thanks. Since a saildrive is horizontal there would be no P-factor, just like there is no prop walk in reverse. Since the prop is a tight turning prop it makes sense that the prop wash swirls around time hit the left side of the rudder and could explain this effect I see. But I have not heard the same from others. Does anyone else have a saildrive and a single rudder that can comment on what they see when motoring and letting go of the wheel? Thanks.
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Post by ohana on Jul 15, 2020 21:53:16 GMT
So, with a SO439 with a saildrive and single rudder, I am perhaps fairly close to your engine setup, hull shape and rudder configuration. Can't say I have noticed this particularly, but will do so this weekend if I can get the opportunity. What happens if you let go the wheel but lock it, does the boat still have a tendency to drift to one side?
Also - prop is a flexofold 3 blade
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Post by NZL50505 on Jul 15, 2020 22:18:15 GMT
The type of prop might also explain slight differences between the behaviour of your boat and others. Do you know what prop you have and what the other 469 has? I've had the exact same effect you describe on all my boats which have been a combo of shaft and SD. It's not an awful ting - on the upside if you fall in at least the boat will circle back to get you eventually
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Post by moonshadow on Jul 16, 2020 0:51:04 GMT
My prop is a flex fold three blade also. And the turn does not occur if I lock the wheel. The effect is not just turning the boat, it is causing the rudder to turn which then turns a the boat.
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Post by NZL50505 on Jul 16, 2020 8:01:10 GMT
Yup that sounds like normal prop walk to me. If it’s not a strong force that is ‘grabbing’ the wheel immediately and forcefully as soon as you let go under low-med power then it’s not an issue. It’s totally normal on most boats. Under full power it will almost certainly pull one side quickly and abruptly and that’s also normal. I don’t think you have a problem!
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Post by moonshadow on Jul 16, 2020 10:00:00 GMT
Thanks for the input. Of course I was getting concerned, glad to know it’s not rare.
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Post by Bora on Jul 17, 2020 15:55:06 GMT
I’m heading out tomorrow after getting the bowthruster replaced....🤦🏻♂️ I’ll give it another go in the calm Croatian waters and see how I get on.
Just to be sure we’re doing the same thing can you let me know the RPM you’re going at and confirm the rudder is centered when you let go?
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Post by moonshadow on Jul 17, 2020 17:49:46 GMT
On my boat I usually am at 2300 rpm and the rudder centered, not locked. Let go of wheel and see what happens. Thanks.
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Post by Bora on Jul 17, 2020 17:56:24 GMT
Is that max RPM? I’m sure I only get around 2200. Not far off but that’s lever to the deck
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Post by moonshadow on Jul 18, 2020 1:39:13 GMT
I have a 4JH5E that I use at Cruise 2300 rpm. Full throttle gets me 3000.
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Post by neworca1 on Jul 18, 2020 19:36:42 GMT
We'll give it a test too, just to make sure we get the same results both East and West of you! Will report back.
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Post by moonshadow on Jul 19, 2020 14:22:50 GMT
Findhorn: im wondering why you only get that rpm at full throttle. The book on my 4JH5E says 3000 is full. And I think you have a similar flex fold prop. Perhaps a Different pitch? But might be worth looking into.
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Post by Bora on Jul 19, 2020 14:26:34 GMT
When I was motoring yesterday in flat water (with a breeze) I was getting 3000 and doing about 8 knots. Must’ve just been the last few times I’ve been out there’s been a decent sea so perhaps it just couldn’t reach 3000 with the load. What fuel consumption do you get?
I found I was having to put a bit of starboard rudder on to go straight in the conditions (1-2 degrees according to autopilot) but when I let go of the wheel she kept going straight.
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Post by moonshadow on Jul 19, 2020 20:08:22 GMT
Thanks for the info. More data is good info. I’m in the 7.5 kt range at 2300 rpm burning a bit under one gallon per hour. I guess that’s about 3.5 l/hr
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Post by ohana on Jul 20, 2020 8:24:52 GMT
So, with a SO439 with a saildrive and single rudder, I am perhaps fairly close to your engine setup, hull shape and rudder configuration. Can't say I have noticed this particularly, but will do so this weekend if I can get the opportunity. What happens if you let go the wheel but lock it, does the boat still have a tendency to drift to one side? Also - prop is a flexofold 3 blade Hi - was out this weekend but F4 - 5 so unable to trial the steering drift - apologies!
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Post by moonshadow on Jul 20, 2020 23:15:36 GMT
Maybe you will have a chance next time.
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