Rudder Angle Limits When Going Backwards

[Deleted member 36384]

Hello,

My Rival 41C does not go backwards very well. Her stern turns to port when under reverse power and when neutral is selected the port turn continues even with rudder blade is pointing to starboard. The hull is a deep forefoot, encapsulated, long and thick fin. The propellor is a 3 bladed job and she is over propped.

The stern gear travel is limited to about 35 degrees and there are massive stops glassed into the hull to prevent the rudder stock tiller arm from going any further. I understand that around the 35 degrees is the maximum angle and anything after that simply results in more drag and less desirable flow being deflected to turn the boat.

My query is this. When going astern is the rule much the same, or if I could turn the rudder more more would the stern change of direction be more pronounced and thus beneficial for coping astern direction, especially with the propellor not turning?

What do you think?

Thanks,

BlowingOldBoots

 

[Tranona]

The rudder has minimal effect going backwards (as you have discovered) and at those angles it is more effective as a brake. There is minimal waterflow over it and turning any further will only make it worse.

Time for a bow thruster if you really want to control the direction in which the boat is moving when going backwards.

 

[ex-Gladys]

Better technique can help, so don't have the engine running astern when you are trying to steer (unless the prop walk is helping). Burst of astern to get the boat moving, then she SHOULD respond more to the rudder - may need to be doing a couple of knots...

 

[Richard10002]

In the absence of a bowthruster, on our narrowboat when going astern, and the boat wont respond to the rudder, I give a burst of ahead, with the rudder in the appropriate position. Even if the burst stops the boat, it gets her pointed in the right direction, and I can get going in astern again. Sometimes I can be seen zig zagging along the canal back to my berth. Other times I manage an amazingly straight line.

Previously, on our Moody 44, we tried to arrange things such that a turn, or a swing, to port when going astern was helpful, e.g. when leaving a berth, or when arriving at a berth...

I used to sail on a Nicholson 31, which was very difficult to steer when going astern. i wonder if my new found skills would have improved things

 

[prv]

No science behind it, but intuitively I wouldn't expect more rudder angle to help. And probably best not to mess with the good solid stops.

Pete

 

[lpdsn]

I doubt whether the rudder is working well at 35 degrees unless you're already turning in that direction anyway. I try to keep the rudder angle significantly less than the max when going astern except for slow speed turns into my berth once the turn has already started. So I doubt a greater angle will be beneficial.

I find speed is the most important factor, although I'm lucky in having a boat with a deep spade rudder that I know will eventually take control. Of course the downside of speed is that if it doesn't work it makes the subsequent crunching and grinding upon impact both louder and more expensive.

 

[KellysEye]

We had a long keeler with prop walk and we did two things. We would go on to a pontoon bows to and when leaving tied a rope to an amidship cleat and a pontoon cleat near the bow. Have someone on the pontoon holdin g ther boat straight run the engine at 800 rpm and wait until you see water moving over the rudder, release the cleat keep the rudder central and the boat wil go straight back.

When manouvering blip the throtle that should stop propwalk it is dificult to do in strong wind or cross tide.

 

[pcatterall]

The 35degrees concept could help me without long keeler. The rudder will turn quite a bit more and I confess to trying to steer astern with max lock which is probably a waste of effort.
I will check where my wheel should be to achieve around 35degrees and test her at that angle!
As suggested I recognise that I need a bit of speed t get the water very the rudder.
Now......some practice!!

 

[lw395]

The rudder is stalling with an angle of attack of 30-odd degrees.
The turning force will get less if you increase the angle.
If there is a skeg you might even do better with less rudder.

A boat that is already turning can use more rudder as the stern is going sidewise to some extent.

All boats seem to handle differently.
My technique is based on squirts of prop wash in ahead to more the stern, followed by slower astern to move the boat.
I freely admit to not being very good at it, because I hop from boat to boat.
First time I get on a different boat I like to find a bit of empty (and unobserved!) water and have a little practice.

If I can plan my way to not needing to go astern, I'm happier!

 

[bikedaft]

pretty sure the 35deg stops are for going astern - when would you have the tiller/rudder that hard over going forwards/?at all?

(we/I have similar issues!)

oddly if we put the engine going astern at tickover only, i can 3/4 times get her stern to starboard. slowly, but worth a try. i nearly fell overboard in surprise the first time i (accidentally) did it...

 

[Deleted member 36384]

Thanks for all the tips, I will take note and practise. I can handle the boat okay with warps and stuff but would like to back up from time to time without having to turn her on the spot, such a palaver.
The bow thruster is likely on the cards but have sails and a complete set of electronics to change out first including auto helm.

 

[Richard10002]

pretty sure the 35deg stops are for going astern - when would you have the tiller/rudder that hard over going forwards/?at all?...

When stopped or almost stopped, and you want to swing the boat one way or the other on the spot. When going astern, and a burst of ahead will act a bit like a bow thruster. When tacking.

 

[RobbieW]

Hello,

My Rival 41C does not go backwards very well. Her stern turns to port when under reverse power and when neutral is selected the port turn continues even with rudder blade is pointing to starboard. The hull is a deep forefoot, encapsulated, long and thick fin. The propellor is a 3 bladed job and she is over propped.

The stern gear travel is limited to about 35 degrees and there are massive stops glassed into the hull to prevent the rudder stock tiller arm from going any further. I understand that around the 35 degrees is the maximum angle and anything after that simply results in more drag and less desirable flow being deflected to turn the boat.

My query is this. When going astern is the rule much the same, or if I could turn the rudder more more would the stern change of direction be more pronounced and thus beneficial for coping astern direction, especially with the propellor not turning?

What do you think?

Thanks,

BlowingOldBoots

Same boat but with a Brunton Autoprop - when clean underwater shes more likely to respond to the helm BUT, as I'm sure you're aware, the high bow is as important as the propwalk in determining whats going to happen - the wind is generally king...

 

[johnalison]

My last boat, a Sadler 29 had a transom-hung rudder which would go to almost 90 degrees, but I don't remember what it was like going astern. I do remember that changing to my current boat with about 45 degrees felt very strange at first, and this was compounded by a change to saildrive.

I've no experience with long keels, but it is hard to see why a boat going astern with the engine in neutral should continue to turn against the sense of the rudder. The usual technique of knocking it into neutral works well on my boat. Maybe the problem is allowing too much rotational momentum to build up. With my folding prop I find that a short burst of plenty of power is more effective than using less power for longer.