True Wind on B&G Zeus 3: missing something obvious?

[jbinbi]

Just reviving this. On my zuess 3 I unchecked 'use sog ' under advanced > instruments and on my triton under 'boat speeds I have dst810 checked. This is paddlewheel depth temp unit. I think this combo gives the most accurate you can get true wind measurements. Correct if wrong.

[noelex 77]

Originally Posted by jbinbi

Just reviving this. On my zuess 3 I unchecked 'use sog ' under advanced > instruments and on my triton under 'boat speeds I have dst810 checked. This is paddlewheel depth temp unit. I think this combo gives the most accurate you can get true wind measurements. Correct if wrong.

Yes, if you want a measurement of true wind then what you are doing is correct.

However, it is worth (on a cruising boat) trying the alternative ground wind display (using SOG) to see which you prefer.

[Statistical]

Originally Posted by jbinbi

Just reviving this. On my zuess 3 I unchecked 'use sog ' under advanced > instruments and on my triton under 'boat speeds I have dst810 checked. This is paddlewheel depth temp unit. I think this combo gives the most accurate you can get true wind measurements. Correct if wrong.

You are correct. This assumes the STW is correct. If you keep your speed log calibrated and clean then this is the best way to compute TWA and TWS. However if it isn't then garbage in -> garbage out.

[Dockhead]

Good true wind is the holy grail of yacht instruments.

It's really hard to obtain because of the difficulty of measuring speed through the water.

I'm still chasing good STW data. I bought a DX990+ which was DOA and has been sent back to Airmar for service. I was previously using a CS4500 ultrasonic which was the best I've used, but still far from perfect. Currently using a UST850 and waiting for a Signet Blue top which is on back order. And for the DX990+ to come back.

The DST810 does not have a good reputation. If you want to go paddlewheel, then the Signet Blue Top, as used by racers, is a far better option.

Whatever transducer you have, you have to calibrate it, as no speed log transducer ever made has a very linear response. Heel also affects speed measurements.

The smart Airmar transducers -- the ones which use the bluetooth Cast app and can be calibrated for heel and at multiple points along the speed range. The DX990+ does that and I think one of the paddlewheel transducers. This is really useful. Otherwise, you need to use a racing computer -- either a PC running Expedition, or a B&G H5000 (what I use), or one of the other systems.

Otherwise you will calibrate it to be right at one speed and heel angle, but it will be off to some degree at others. Maybe OK for casual cruisers, but you'll see that the true wind goes wonky in various conditions.

Ground wind (calculated with SOG instead of STW) is useful for strategic purposes, especially planning for tide changes, but is useless for sailing in any kind of current. You sail in the sheer between air and water and ground has nothing to do with sailing. So if you want to have valid laylines, be able to sail near DDW safely, understand where a tack will take you, you have no choice but to work on getting decent STW data.