DIY windvane idea

[Kelpie]

We're looking at buying a bigger boat and will be needing a self steering system for it. Due to the cockpit layout we would prefer an auxilliary rudder system like the Hydrovane.
However we already own a perfectly good little windvane, a servo-pendulum Navik.

My idea is to construct a balanced auxilliary rudder for the new boat, mounted on the transom, and then drive this using the little Navik. So it would be almost a DIY copy of a Windpilot Pacific Plus.
The Navik is very sensitive even in light winds, and whilst building the whole system from scratch is possible with much patience and trial and error, surely a simple rudder on its own would be much easier.

The main problem I would forsee is that the Navik might have to sit too low on the transom and get bad air on the air vane- it is designed for much smaller boats, after all. But that could be addressed by extending the turret tube and the pushrod.

Any thoughts? I can't be the first person to think of doing this...

 

[macd]

Any thoughts? I can't be the first person to think of doing this...

I'm sure you're not the first. A little googling might prove it...

Nor can I see any reason not to extend the turret, assuming it's well engineered. Preserving the weight of the push-rod is important, if possible: you may need to consider aluminium alloy or even CF. (Good ally rod is available from car and motorcycle race shops, used for custom control mechanisms.)

Good support for the new rudder is clearly paramount...far stronger than for the Navik itself. Ideally, it should also lift up.

What sort of control mechanism do you have in mind for the new rudder? Rather than a conventional tiller arm, you might consider a transverse bridle with the control lines led through blocks at each end, which may intrude less into the cockpit.

Do report back if it works.

 

[Kelpie]

Hadn't considered the pushrod weight- thanks for bringing that up. The current one is, I think, GRP, so already fairly light.

One of the attractions of this idea is that I can design and build the rudder to my own spec. I don't think the Hydrovane's rudder lifts up easily, so this is something that I could incorporate.
I'm thinking of the rudder being directly mounted to the transom, entirely independent of the Navik.

I've had two ideas as to how to couple it together. The obvious one is to have a short tiller, sweeping the aft deck (it's a CC boat so no cockpit intrusion). I might find it works better to have the tiller mounted facing aft, and cross over the control lines.
The other idea, a bit more elegant, is to create some kind of rack and pinion system. I could fit a toothed rack onto the Navik's quadrant (a section cut from a suitably sized flywheel perhaps?) and then a cog driven from that to create a rotary movement in a vertical axis, which can be used to drive the rudder shaft, either directly or via a belt/chain.

 

[Cardinal]

Regarding the possible use of a section of flywheel, is it not the case that the toothed circumference is usually a shrink fit and would have to be welded onto any segment?

 

[macd]

I've had two ideas as to how to couple it together. The obvious one is to have a short tiller, sweeping the aft deck (it's a CC boat so no cockpit intrusion). I might find it works better to have the tiller mounted facing aft, and cross over the control lines.
The other idea, a bit more elegant, is to create some kind of rack and pinion system. I could fit a toothed rack onto the Navik's quadrant (a section cut from a suitably sized flywheel perhaps?) and then a cog driven from that to create a rotary movement in a vertical axis, which can be used to drive the rudder shaft, either directly or via a belt/chain.

I suspect that a rack and pinion or similar system would need a weak link somewhere in it to avoid damage at extreme unusual loadings. I presume your Navik, as it's configured now, has a relatively light section of control line for this purpose.

An aft-facing tiller might well work. The "bridle" I suggested might look something like this:

 

[Spirit (of Glenans)]

Regarding the possible use of a section of flywheel, is it not the case that the toothed circumference is usually a shrink fit and would have to be welded onto any segment?

If I recall correctly, from the days when cars were engineered sufficiently simply to be taken apart and put back together by the average 'learning by doing' DIY mechanic, the toothed rack was heated up then located on the flywheel where it gripped on tightly when it shrunk back to normal size. Get one from a Ford Anglia

 

[SvenH]

Extending is indeed not a problem if you keep the weight of the connecting rod in mind.

I know from experience that the original (glass fiber) is heavier then a carbon fiber one needs to be.

I can also make you a longer one as I manufacture replacement parts for Navik.

 

[rogerthebodger]

We're looking at buying a bigger boat and will be needing a self steering system for it. Due to the cockpit layout we would prefer an auxilliary rudder system like the Hydrovane.
However we already own a perfectly good little windvane, a servo-pendulum Navik.

My idea is to construct a balanced auxilliary rudder for the new boat, mounted on the transom, and then drive this using the little Navik. So it would be almost a DIY copy of a Windpilot Pacific Plus.
The Navik is very sensitive even in light winds, and whilst building the whole system from scratch is possible with much patience and trial and error, surely a simple rudder on its own would be much easier.

The main problem I would forsee is that the Navik might have to sit too low on the transom and get bad air on the air vane- it is designed for much smaller boats, after all. But that could be addressed by extending the turret tube and the pushrod.

Any thoughts? I can't be the first person to think of doing this...

I have modified my monitor in the same way by attaching an auxiliary rudder system.

I have also extended the servo blade shaft incorporating a shear pins that will protect both the auxiliary rudder system and the servo.

some pics on the web site in my sig.