Rudder For Outboard Motor

[Lakesailor]

I have discovered that whilst outboards are OK for small boats, close quarter manoeuvring without a rudder (always had them on yachts before) is a nightmare. As I like to put the boat into the boathouse stern-first this can be a balls-ache.
I had just built a clamp-on rudder which attaches to the outboard leg and has transformed the low-speed handling. As it's a displacement boat and can only manage 6 knots it doesn't have to be flip-up or anything posh.

Here's the story.
I made a cardboard template. It included the cavitation plate as I thought it may need to have little clamps on to that as well.

Then I bent some steel strip to the template and found a bit of grp, for the rudder blade, which I'd cut out of the boat's buoyancy tank to make a hatch.

I had some "D" section rubber fendering left from fitting to Feckless last year.

and squeezed that over the steel strip to protect the leg.

A test fitting seemed to look good

I cut the grp to suit (I hoped)

I used stainless bolts with locknuts. I know the clamps are steel, but it's only freshwater and I don't think it'll be a big problem If it is I'll do it in stainless or alloy.

There it is fitted

There is a little lip in the casting which I hope will locate it.

The proof of the pudding etc......

....is the video of before and after. In the first part you can see that getting lined up is tricky with any breeze blowing and the only way to steer is a small burst of throttle, which may get you travelling too quickly towards some very solid walls.

Any comments or suggestions welcome.

​

 

[BrendanS]

Neat. That looks like it does the job!

 

[sarabande]

quite a difference !

I can't remember the underwater config of your new boat (I've lost track, to be honest ) but I think it has a bit of a keel ? That obviously helps.


Now what you need is a bow thruster, and some underwater LEDs, and not even jfm can better you for having proper storage

 

[Lakesailor]

Bit of a keel, but in the nature of low power outboards it has been a bit wishy washy with corrections needed all the time.
Hoping that straight courses will be easier now.

 

[chewi]

Curious to ask why you added the rudder aft of the prop instead of above it if its use is for in reverse where the prop thrust is nil.

Wouldn't it be more convenient and maybe just as effective to make a vertical fin above the prop that doesn't extend the length so much?

I have contemplated doing this on my Honda 2.3 centrifugal clutch to improve steering at tickover instead of the point & squirt approach.

p.s . love the boathouse.. if only..

 

[Lakesailor]

Not sure what you mean. You couldn't put it above the cavitation plate as it wouldn't be in the water very much.
The prop thrust is not required. Once a bit of way is on it acts as a rudder. It means I can steer the boat at tickover or even in neutral. All you need is a bit of boat speed. Prop thrust is the very thing I want to avoid as every squirt speeds you up when you, in,fact, would rather be slowing down. (There are alternate holes so I can move the blade nearer to the axis if needed, but it seems to work well as it is.)
The second part of the video is reversing at tickover in astern and you can see the accurate corrections that can be made just by turning the leg.
In the first part of the video (without the rudder fitted) the stern needs a burst of astern to pull it into line with the boathouse doorway, but that would speed the boat up too much, so I abort and go forwards. It's only 15ft and weighs less than 400Kgs so a burst of throttle affects boatspeed very much. If it were a yacht weighing getting on for 1000kgs it wouldn't be such a concern. On the other hand I would have a big rudder to steer with anyway

 

[chewi]

The skeg has to deep enough to get the prop below the transom, so there is some scope to add the rudder behind the transom, and in reverse more of this would be in the water because of the wash rising up the transom.

One of our own club members has done as I have suggested, elongating the very thin skeg into a rudder by clamping a plate to it. Admittedly its purpose is to improve steering after the clutch disengages, not for reversing, but I expect it would still help a lot, and not be so exposed as yours is.

But yours works for you, so thats good!

 

[Vara]

Looks good, bit worried about the flat plate profile, maybe one of the less extreme NACA profiles might be better so as not to compromise the high performance of your speed machine.

Useful when the wardens go home.

 

[VicS]

I think I would just have driven forwards into the boat house!

Maybe I've missed something

 

[Giblets]

I think I would just have driven forwards into the boat house!

Maybe I've missed something

Perhaps he needs to be ready to make a quick gettaway!

 

[Lakesailor]

I think I would just have driven forwards into the boat house!

Maybe I've missed something

That's a very reasonable suggestion. The reason I like to back in is for security.
Anyone punting (or wading) up the the doors will not see the outboard this way. Bit paranoid perhaps, but outboards in quiet locations are tempting to certain people.