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Boat Moving Sideways

nickd

By nickd
in Boat Handling

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nickd Engager

nickd

Posted
Posted

Hello Folks,

 

I've just bought a boat, 42' with Lister SR3.

I'm still learning its steering foibles and am having a few problems and wonder if you can help.

 

When I put the rudder hard over and put any reasonable thrust on the engine, instead of the prow moving in the required direction the wholeboat 'crabs' sideways in that direction; under low power it's fine but there are times that I need to quickly manouvre, eg tricky turn, winding or when there's a wind blowing etc etc

 

When the survey was undertaken the surveyor said the boat had a smallish rudder, would this have any bearing on it?

 

I would appreciate any advice.

 

Regards,

 

Nick

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howardang Influencer

howardangDonate to Canal World

Posted
Posted
Hello Folks,

 

I've just bought a boat, 42' with Lister SR3.

I'm still learning its steering foibles and am having a few problems and wonder if you can help.

 

When I put the rudder hard over and put any reasonable thrust on the engine, instead of the prow moving in the required direction the wholeboat 'crabs' sideways in that direction; under low power it's fine but there are times that I need to quickly manouvre, eg tricky turn, winding or when there's a wind blowing etc etc

 

When the survey was undertaken the surveyor said the boat had a smallish rudder, would this have any bearing on it?

 

I would appreciate any advice.

 

Regards,

 

Nick

It sounds like the rudder is stalling - i.e. the prop thrust is flowing on each side of the rudder with the rudder hard over so as well as a turning component you are also getting more ahead thrust that you would normally expect. Try easing the rudder back towards amidships until you get maximum turning effect and then remember that setting for future use.

 

HTH

 

Howard Anguish

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DHutch Veteran II

DHutchDonate to Canal World

Posted
Posted

Yeah, if nothing else, try it a little off full lock.

- On most boats the rudder will move further than its optimum position.

- Only emilyanne you get more turning half a turn off full lock, going left anyway.

 

 

 

Daniel

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dor Veteran II

dor

Posted
Posted

When turning such as winding, try wiggling the tiller and watch the wash coming out at the back. As you move the rudder from say 20 degrees to about 60 degrees you may see the wash split round the prop. If you keep wiggling slowly, if you are lucky you will suddenly see all the wash directed to the side instead of being split.

 

It's all to do with something called "fluidics", and basically it's because the water likes to keep attached to a surface.

 

It may not work if the rudder is too small or doesn't have enough balance area, but if you can catch the trick, it's amazing how easy you will be able to turn your boat. Get it right and you will be able to spin the boat practically in its own length.

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  • 1 month later...
John Orentas Veteran II

John Orentas

Posted
Posted (edited)
When the survey was undertaken the surveyor said the boat had a smallish rudder, would this have any bearing on it?

 

 

It should have two bearings on it: One top, one bottom. (Oh dear should have read the previous post).

 

It could be too small, but more likely not enough 'balance blade', that's the extension forward of the rudder shaft. Also as Daniel says it may be a case of to just just to much rudder angle, experiment using less angle you may find an improvement, many boats are built like that.

Edited by John Orentas
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zenataomm Veteran

zenataommDonate to Canal World

Posted
Posted

I agree with most of the replies (except about the bearings, I lost mine ages ago and haven't suffered at all ..... those around me have, but I'm ok)

 

What is worth remembering is that narrow boats aren't really designed to be steered in reverse, it's there to stop you. There will always be the odd design that can do it, and those that can will be loud in their claims. They only do that to make us lesser mortals hang our heads in envy, and because they can!

Yes of course the size of the rudder is important in order to get maximum efficiency as is the balance area. You will find as others have suggested that you'll get a feel for what works.

 

The other thing that may be affecting the sideways crabbing motion is your engine. Listers, even 3 cylinder ones are still slow revving and throwing a lot of weight to one side. You'll not notice it when in ahead but when you change direction (ahead to astern) it'll make itself felt. You can prove this to yourself in a wide lock on your own. The boat is likely to show a preference to staying aginst one wall than the other, due to the rotation of the engine even on tickover.

 

zenataomm

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bristol & argo Collaborator

bristol & argo

Posted
Posted
snip,

a case of to just just to much rudder angle,

snip,

, many boats are built like that.

 

And if you've got a full size boat, it can be quite important that it does, along with being able to lift the stern fenders so you can get through Caen Hill :)

 

Hmm, those friends still haven't been back for another trip :lol: .

 

 

simon.

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zenataomm Veteran

zenataommDonate to Canal World

Posted
Posted
Who mentioned going in reverse?

 

JOTW

 

 

I did!!!!!! ...... t'was me!........ I recognise that dribble anywhere!

........... but only because I wanted to create a tenuous link in order to start waffling about slow rotating engines with heavy flywheels that make boats go sideways when they lose way. Perhaps I lost my way! But that's not my fault, you really shouldn't let me on these forums , I can't be trusted you know? Anybody got any custard creams?

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