Tacktick anemometer under-reading

Iain C

Iain C

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So my wind instruments are clearly under-reading, and it's fairly visibly due to the cups on the masthead sender unit turning too slowly.

What is this likely to be? Bearings? Corrosion? I'm probably not the first person to have experienced this so if anyone has any pointers as to how they fixed theirs, to minimise trips up the rig, I'd be grateful!

The rig has been up for the last few years with the boat kept on a swinging mooring, so in theory the cups have been turning all of that time so there's probably not much scope for a waterborne party of spiders to take up residence...

Thanks in advance.
 
There are two different designs for the tacktick MH unit, if you have the earlier one (as I do) it is known that the bearings on these do wear. They can be user-replaces but it's a fiddly job and difficult to reseal the unit afterwards to keep water out of the electronics. If you take it to Raymarine they should do a service/repair for a set fee which means they will sell you one of the later type but at reduced cost.

Mine is of the earlier type and it is under reading by a few knots. I must investigate to see if there is a way of calibrating it in the short term to make up for the error but the long term it will probably need replacing.
 
Iain C said:
So my wind instruments are clearly under-reading, and it's fairly visibly due to the cups on the masthead sender unit turning too slowly.

What is this likely to be? Bearings? Corrosion? I'm probably not the first person to have experienced this so if anyone has any pointers as to how they fixed theirs, to minimise trips up the rig, I'd be grateful!

The rig has been up for the last few years with the boat kept on a swinging mooring, so in theory the cups have been turning all of that time so there's probably not much scope for a waterborne party of spiders to take up residence...

Thanks in advance.
Click to expand...

Our Tacktick had the same after two years. A new bearing (courtesy of the dealer) solved the issue...for now.
 
This might be a very stupid question but how can one tell if one's MHU is under reading. I can understand indicating a F1 when the dogs are being blown off their chains but a few knots out??? :confused:
 
Giblets, it's fairly significantly out. If I believed my instruments, I would have a Sabre 27 that's pretty much faster than the windspeed on all points of sail, and yes her freshly antifouled bottom does make a difference, but not that much of a difference! In light airs my cups aren't turning when other people's are, and I'd estimate it to be at least 50% out between 10-20kts.

Georgio, are there any visible differences to the old and new versions?
 
Yes, sorry, I should have explained...

The casing that is immediately above the cups is more cone shaped on the new-style, while the old one is not. Sorry, it's hard to describe without a picture. I'm sure the Raymarine site will show the new version.
 
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Check the 'units' being displayed. Metres per second is roughly half the numerical value of knots, which then appears as an under read. I have had this happen.
 
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If it ain't spinning when others are the units won't matter! I'm fairly convinced it's the bearings so I'll order a new set.

Thanks all!
 
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