Lean to port.

[kindredspirit]

I haven't solved this problem and no one in the marina can find an answer either.

Sometimes my boat leans to port when above 2,000 revs. Not all the time, only sometimes. It never leans to starboard. It's not a weight distribution problem of my own doing.

Someone said it might be to do with "the inertia of the flywheel in the engine"
That seems to be a bit far fetched.

I had a New Zealander boat designer look at it whilst it was out of the water. He couldn't see why it should lean.

I'm probably missing some simple little answer, but for the life of me, I can't see it.

Has anyone got any ideas?

<hr width=100% size=1>Kev.

 

[hlb]

Have you got trim tabs. One of mine works quicker than the other.

<hr width=100% size=1> <font color=blue>It's flog a flag day.<font color=red> Today.<font color=blue>

Haydn

 

[kindredspirit]

No, Haydn, I forgot to mention, there's no trim tabs on the boat.

But, it's an option I'm considering if I can't sort out the problem.

<hr width=100% size=1>Kev.

 

[tcm]

the flywheel inertia sounds a bit unlikely. If there was such an effect, it would be progressive from low to high revs, and eventually flip the boat over.

I wonder if it is to do with hull design - if it is tall and narrow, then there's the possibility of "chine running" where the hul catches the chines and runs along that.

Trim tabs sounds the easiest answer.

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[HowardB]

If it were flywheel inertia it would only take the effect accelerating and the reverse when decelerating IMHO. If it was the gyroscopic effect of the flywheel it could be true but very unlikely, and would get worse and worse with higher revs.

I had similar in a sealine 255, and found that it was the trim of one leg, not the trim tabs. The hydraulics were leaking slowly. As I went faster the leg trimmed further in and lifted that side up. Bl**dy scary, because it was a progressive effect and the trim tabs couldn't compensate. Took a while to realise what was wrong... Sometimes it didn't lean, and that was when I had trimmed both legs in before getting onto the plane.

But you're on one engine (?) so dunno.

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[Johnjo]

Could it be the thrust of the prop turning one way causing the boat to lean the other?
Was it Newton who said for every action there is a reaction?
only a guess though!.........

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[hlb]

I thought it was Fankinstiens law of relitivity??

<hr width=100% size=1> <font color=blue>No one can force me to come here.<font color=red> I'm a volunteer!!.<font color=blue>

Haydn

 

[kindredspirit]

Could you explain "chine running" in more detail?

The beam of the boat is 3 metres and she's very high sided with the flybridge. There's a lot of windage with the boat.

<hr width=100% size=1>Kev.

 

[hlb]

Think you've explained it. If boat only 3 metres wide and one big prop wizzing around in the middle. Then boat is trying to wiz round the other way and maybe resting on chine. Which way your props going round??

<hr width=100% size=1> <font color=blue>No one can force me to come here.<font color=red> I'm a volunteer!!.<font color=blue>

Haydn

 

[kindredspirit]

I'll have to check up on that.

When I engage reverse slowly in the lock the stern moves to port. Is that a RH prop or a LH prop?

<hr width=100% size=1>Kev.

 

[Observer]

RH prop (i.e. turns clockwise viewed from behind) so turns LH in reverse so 'walks' the stern to port.

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[kindredspirit]

I've just done some propellor research on Copernic.

I have a RH propellor and too much RH propellor torque will produce a list to port. Therefore as I have a fairly powerful single engine, I'm going to have to invest in trim tabs next autumn.

Thanks very much to everyone who replied. Problem and solution identified.

Thanks again.

<hr width=100% size=1>Kev.

 

[Chris771]

Hi Kev,

Been missing in Angola without easy internet access for a while, now back in europe. Actually down your way on a rig off Kinsale this week.

To elaborate on heel, Arctic Fox (similar configuration) does the same thing. If I just wind the throttle wide open I also get a torque reaction to the single prop whizzing around. Have found that if I back the throttle off a bit she will then ride level and the revs can gradually increased without causing chine riding. A reasonably strong side wind acting on the superstructure will also push her over onto a chine, a few 25 litre drums of diesel moved to the high side cures that (not very elegant but it works).

I have also bought some trim tabs (but not fitted them yet) for that very reason.

Chris

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[Chris_d]

Could be flywheel inertia in combination with prop rotation, i had the same problem
the faster i went, the worse the list became until the boat veered violently one way and we fell off the plane. It was made worse in my case by trying to apply tabs to correct the lean, the bow digs in to far and that makes things even worse.
Turned out i had a LH turning engine with a LH turning prop, so engine was twisting the hull and the prop was helping it as well, if you think this b*****ks, try to grabbing the end of a drill chuck while it turning, the body will spin the other way ever seen Wallace and Grommit!
Obviously the only applies to single screw boats, twins will cancel out becasue the props are usualy contra-rotating. I my case i fitted a RH prop and reversed the gear cables so i was going in reverse for forward and vica-versa, this was possible on my outdrive but not on all apparently.
Anyway this might not be your problem at all but cetainly worth checking, boat builders aren't that through in my experience.

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[kindredspirit]

Oh ! So trim tabs may not be the easy answer.

Looks like I'm going to have to look further into it.

<hr width=100% size=1>Kev.