My ST60 wind, masthead unit has sat at the top of my mast since 2002 and always worked very well until last season. I have taken the mast down to replace the rigging and when I came to remove the masthead unit found that some of the wind speed indicator cups were full of spiders webs and nesting remains. Whilst the instrument still worked it was obvious that the recorded speed was less than the true wind speed and it failed to turn at wind speeds below 4 or 5 knots. The bearings still seem in OK condition and although I cannot be certain it would appear that the blanking off of some of the cups by the spiders webs has been the cause of the under reading.
If I had realised what was uptop a quick trip up the mast would have resolved the problem. We do get a lot of the little blighters on our river mooring in Brittany but the thought never crossed my mind that they could cause such havoc.
Has anyone else had such an experience.