Windspeed cups rotation

[Roberto]

The rotation speed of the three cups of the masthead unit of my Raymarine wind meter is somewhat strange: suppose a steady 20k wind, the cups will rotate freely but say every 5/10 seconds the suddenly slow down, stop, and restart rotating immediately thereafter. And so on, more like if the wind was blowing in 10 seconds puffs.

With very low wind speeds (say 2-5knots) the cups sometimes do not turn at all, which might indicate there is some friction in the unit.

WInd speed indication seems ok, or maybe a bit underreading up to 25-30knots, then upwards basically correct.

I have looked at other masthead units in my marina and found that there are quite a few with the same "pulsating rotation" movement: is it normal ? or all these units have the same fault ?

In a trip to the masthead, what should I look for ?

tia

 

[ChrisE]

Sounds as if you'll need to get the bosun's chair out! We have Raymarine kit and a it reads down to very light winds and b seems to have constant rotation.

 

[Guest]

If you are in a marina then turbulence. If you are out at sea then mast movement. Wind never blows constantly near objects (or rough sea) it is a figment of the damping in the instrument.

 

[CraigB]

Think yourself lucky. Mine doesn't spin at all!

When the mast was down recently I took it off, inspected it, blew on it with as many beauforts as I could muster, and it spun perfectly. But after a couple of days remounted aloft it has stopped again. I am loathe to go near it with any type of lubricant. Only cleaned it with fresh water. Perhaps I need a new one /forums/images/graemlins/frown.gif

 

[awyatybw]

The bearings do eventually go on these. Raymarine do a bearings replacement kit which is quite a bit cheaper than a complete new masthead unit.

Of course, the bearings/fitting could just need cleaning. How old is it?

Alan.

 

[Skyva_2]

As above, the bearings can be replaced or lubricated. Wind speed rose dramatically when ours was serviced.

 

[roberth]

Had same problem. Had good response to post and tried the easiest solution first, which was to spray a bit of lubricant on the workings.

Did a couple of months ago, and now spins in the lightest of breezes - no probs so far.

 

[CraigB]

I was told not to use lubricants because they end up attracting dirt. What lubricant did you use? Something like Pro-Lube? WD40?

 

[Roberto]

thank you all!

The unit is a ST50, maybe around 10year old ?(I bought the boat 2hand)


I ll try lubricating first, in case replace the bearings.

Also interested in what kind of lubricant should be used: something like wd40 or just soapy water ?

and, can the bearing replacement be done up the mast or is it necessary to bring the unit on deck?

 

[Skyva_2]

WD40 is not a lubricant - maybe use sewing machine oil?

It would be difficult if not impossible up the mast, much better to bring it down.

 

[Roberto]

two trips up the mast then /forums/images/graemlins/crazy.gif
I think I ll replace the bearings anyway

thank you again /forums/images/graemlins/smile.gif

 

[awol]

Stay up mast, lower MHU to helper for lubrication, pull up MHU and refit. Requires a wee allen key, you know the smallest one that's not on the ring any more, to remove the cups and/or vane.

 

[macd]

"WD40 is not a lubricant"
Hesitate to contradict someone once engaged in aero engineering, but maybe someone should tell the WD40 Company (or maybe Trading Standards). They certainly claim it's a lubricant.

 

[cliff]

Now see here "The world's number one multi-purpose lubricant."
--------------------

"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[Skyva_2]

Point taken, but would you use it on a bearing which will stay unattended up the mast for a few more years. Its lubricating properties are limited and not long lived.

See


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