Giving up on my Raymarine ST40 Wind

[Praxinoscope]

My ‘new’ boat came with the Raymarine ST40 instruments. I can manage with the depth and log, but the wind speed/direction is a disaster. No matter what I do to re-set it the direction part of it occasionally displays roughly the direction of the wind, but most of the time it bears no relationship at all to the actual direction. I have never really understood how the ST40 wind functions with only one masthead component and just two wires, in fact I don’t think it does.
I do have a masthead Hawk, but as I have an old neck injury I find an instrument giving me wind direction at cockpit level a great help.
Much as I would like to fit a Raymarine ST60 wind system cost rather rules it out so am looking at the more economical NASA Marine units, at first I thought the Clipper range but the display units aren’t waterproof, which seems daft for something one would normally fit in the cockpit, but the cruiser and target units are waterproof. Has anyone any experience of these units?

 

[CPD]

The NASA cruiser wind (old/depth etc) got me to the Azores and back. NASA is lower end and cups etc have reputation of disappearing BUT great company to deal with.

 

[fearmhuir]

I had ST40 instruments on my last boat, and they were a quality product.
I had an issue with the wind instrument, similar to yours, and sent the masthead unit to http://marineelectronicservice.com/
They checked it, repaired and serviced it with new vane, cups and bearings, at a fairly reasonable cost.
I am not sure if there are only two connections to the instrument head - I have an idea there should be three - maybe that could be your problem?

 

[SvenH]

I recently replaced the cups after a storm with maybe hurricane gusts.

In the process of taking off the broken cups I tried removing the cups without loosening the hex screw.

As a result I had the mast units guts in my hand.

After putting everything back I now have an incorrect wind direction.
My Idea is that some of the guts were put back slightly wrong, even though i tried to look for indicators on how to put stuff back.

A mast lowering is planned but without a date yet...

Do not try to rush this kind of job, it is super delicate stuff.

 

[RussNelson]

The Rotavecta masthead unit has three cups. One of these cups has a fin. The two wires that go down the mast from the Rotavecta carry a signal that triggers multiple times for each rotation, probably at least three. The fin, when going downwind, pushes that cup faster. When going upwind, it pushes that cup slower. So, the speed of the rotation of the cups varies as the fin goes around and around, so the impulses that go down the two wires vary as the finned cup goes downwind and upwind. From calculating the variation between the impulses, the ST40 can determine the wind direction.

If your ST-40 isn't reporting the correct wind direction, you need to follow the calibration instructions, which include going around in a circle three times. There are videos on YouTube.