Douglas
New member
Shall I buy Silva Star masthead wind instrument @£230, or Raytheon ST40 @£260? My main criteria is reliability, esp the masthead unit.
Wind instruments...
- Thread starter Douglas
- Start date
charles_reed
Active member
I think you'll find most instrument makers are using the same proprietary masthead transducer components, so you'll not find much difference between them on this count.
It really depends on what other instruments you want to interface with the masthead unit - eg if you want true and apparent windspeeds you need connection between log and windspeed indicator.
Though Raytheon use their own Seatalk protocol they do also have an NMEA083 as well.
It really depends on what other instruments you want to interface with the masthead unit - eg if you want true and apparent windspeeds you need connection between log and windspeed indicator.
Though Raytheon use their own Seatalk protocol they do also have an NMEA083 as well.
pvb
Well-known member
Some differences...
I'm not convinced by Charles' view that instrument manufacturers use common transducer components. Most wind transducers you'll see comprise a wind vane (to give direction info) plus a set of rotating "cups" (to give speed info), so there are effectively 2 separate transducers. Silva use a variation of this, with a sort of propellor device instead of rotating cups. But the ST40 has a very different transducer - just a set of cups with a little fin added to one cup. The rotational speed of this device varies minutely during each revolution; the variance depending on the direction of the wind. The ST40's electronics analyse this speed variation to give the direction readout. So the ST40 only has 1 transducer, rather than the normal 2. If you're looking specifically for reliability of the masthead unit, the ST40 would be the logical choice. However, masthead transducers are fairly simple and reliable units, so wouldn't it be better to choose the better looking display? I think the ST40 display lacks clarity. Don't know what the Silva one looks like, because I didn't know there was a Silva Star wind instrument.
I'm not convinced by Charles' view that instrument manufacturers use common transducer components. Most wind transducers you'll see comprise a wind vane (to give direction info) plus a set of rotating "cups" (to give speed info), so there are effectively 2 separate transducers. Silva use a variation of this, with a sort of propellor device instead of rotating cups. But the ST40 has a very different transducer - just a set of cups with a little fin added to one cup. The rotational speed of this device varies minutely during each revolution; the variance depending on the direction of the wind. The ST40's electronics analyse this speed variation to give the direction readout. So the ST40 only has 1 transducer, rather than the normal 2. If you're looking specifically for reliability of the masthead unit, the ST40 would be the logical choice. However, masthead transducers are fairly simple and reliable units, so wouldn't it be better to choose the better looking display? I think the ST40 display lacks clarity. Don't know what the Silva one looks like, because I didn't know there was a Silva Star wind instrument.
JamesS
New member
I've been usung an ST60 wind for the past 6 years without any problems or trips to the masthead. Its worth remembering that most ajustments can be carried out on the display.
Cheers
Cheers
rex_seadog
New member
Doesn't a lot depend on how heavy/aggressive the local seagulls are? Actually, a serious question as I thought this caused many failures of masthead gear. So far I've stuck to pieces of ribbon (a nautical blue!) tied to the shrouds and the force of wind on my cheek, sea state etc. to assess strength. I know when to reduce sail (the boat's trying to tip over!) without recourse to a number on a display.
mldpt
Member
Why do Autohelm use the log to give a true wind speed, on their ST50 windspeed instrument, when the speed over the ground should be used to give true wind speed and COG should be used to give true direction, I have all all my instruments seatalk connected, except my log which is a Stow so My wind instrument doesnt give me true wind, and yet I have GPS giving SOG and COG which is all it need to give true, true wind, perhaps you should consider this when you purchase your wind instrument, the question to ask is which one needs a compatible speed log.
Regards Mike.
Regards Mike.
johndf
New member
Re: True windspeed
Probably because a GPS input is not required if 'true' windspeed is calculated using the boatspeed, just a connection to the log, which is likely to be close to the wind instrument display. On my boat like many, I have the wind and log instruments at the wheel, with the GPS at the chart table.
In addition, a boat heading would surely be needed as well if SOG were to be used. Using the boat velocity vector allows a simple vector subtraction to give the 'true' windspeed.
Probably because a GPS input is not required if 'true' windspeed is calculated using the boatspeed, just a connection to the log, which is likely to be close to the wind instrument display. On my boat like many, I have the wind and log instruments at the wheel, with the GPS at the chart table.
In addition, a boat heading would surely be needed as well if SOG were to be used. Using the boat velocity vector allows a simple vector subtraction to give the 'true' windspeed.
mldpt
Member
Re: True windspeed
Yes but for true direction, COG must be used so a connection to the GPS is required, and in an area of high tide speeds the True speed and direction is not true,
Regards Mike
Yes but for true direction, COG must be used so a connection to the GPS is required, and in an area of high tide speeds the True speed and direction is not true,
Regards Mike
charles_reed
Active member
You'll find no instrument set will give you true windspeed unless the log is talking to the wind indicator - that's because it uses the log speedo to add/subtract the boatspeed and angle of incidence to give true windspeed.
Whenever my log impeller gets clogged apparent speed goes for a burton.
I don't know of any sets which use GPS input with apparent speed to calculate true windspeed, possibly because GPS with selective degrade on is far too inaccurate.
Whenever my log impeller gets clogged apparent speed goes for a burton.
I don't know of any sets which use GPS input with apparent speed to calculate true windspeed, possibly because GPS with selective degrade on is far too inaccurate.