have two speed logs - what if I remove one ?

[Refueler]

My B&G system has a port and stbd speed log setup ... which had switches and apparently auto setup .. to determine which supplied data to display.

I have disconnected the multitude of wires from the mystery blue box which may have been the auto side of it ... it is still connected to the B&G #7 Junction box ...

The #7 box appears to have the transducer cables enter and then a cable goes to the 'Blue Box' ... with possible feed back into the #7 for data out to the display ??

I am of a mind to remove one of the speed logs and just stay with one .. as they are very close to keel line ahead of the actual keel.

The problem is >



As I note - there is nothing in the box - just a line of terminals ...... its going to be a nightmare to decide which / what to disconnect ... I just pray that removing one set of multi's black cable will be OK ..

 

[Alex_Blackwood]

My B&G system has a port and stbd speed log setup ... which had switches and apparently auto setup .. to determine which supplied data to display.

I have disconnected the multitude of wires from the mystery blue box which may have been the auto side of it ... it is still connected to the B&G #7 Junction box ...

The #7 box appears to have the transducer cables enter and then a cable goes to the 'Blue Box' ... with possible feed back into the #7 for data out to the display ??

I am of a mind to remove one of the speed logs and just stay with one .. as they are very close to keel line ahead of the actual keel.

The problem is >

View attachment 196281

As I note - there is nothing in the box - just a line of terminals ...... its going to be a nightmare to decide which / what to disconnect ... I just pray that removing one set of multi's black cable will be OK ..

Just disconnect one transducer and see what happens, you can always reconnect it

 

[Refueler]

I hope that the cables follow the cable description I found online ...

 

[shanemax]

When I was doing a sailing coarse many years ago out of Maldon in Essex the instructor towed a log 50 meters behind the boat. He said what a useless piece of equipment it was with any weed in the water and that the results were never correct.
That stuck with me and with the advent of satellite navigation logs seems pointless. Its a bit like having a cranking handle on a new car.

 

[Daydream believer]

My speed log is to one side of the fin keel & it makes little difference what way the boat heels. As tested on dutch canals with limited tidal flow & GPS.
There is greater inaccuracy with speed depending on what speed one is doing. I have set it to be accurate at 5.5 kts when motoring & it varies from GPS speed ( measured in the Walcheran canal both ways )depending on going faster or slower than 5.5 kts
I think that is more important than the difference caused by heel which is less.

 

[Refueler]

Just disconnect one transducer and see what happens, you can always reconnect it

Easier said than done ... its identifying the cables ....

The 'Blue box' which I suspect is the auto switching unit .... is now not connected fully - so maybe no transducer is going to feed into display ??? Only way to find out is pull transducers and spin by hand ... or go for a sail !!

 

[Daydream believer]

When I was doing a sailing coarse many years ago out of Maldon in Essex the instructor towed a log 50 meters behind the boat. He said what a useless piece of equipment it was with any weed in the water and that the results were never correct.
That stuck with me and with the advent of satellite navigation logs seems pointless. Its a bit like having a cranking handle on a new car.

I would not have a lot of confidence on a clearly biased instructor

 

[Dockhead]

When I was doing a sailing coarse many years ago out of Maldon in Essex the instructor towed a log 50 meters behind the boat. He said what a useless piece of equipment it was with any weed in the water and that the results were never correct.
That stuck with me and with the advent of satellite navigation logs seems pointless. Its a bit like having a cranking handle on a new car.

Satellite gives you very accurate SOG, but tells you zero about STW! These are completely different things.

You must have STW to calculate true wind, laylines, and to have any idea of whether you are trimmed right and sailing at the needed speed.

SOG is not a substitute for STW.

 

[Dockhead]

My B&G system has a port and stbd speed log setup ... which had switches and apparently auto setup .. to determine which supplied data to display.

I have disconnected the multitude of wires from the mystery blue box which may have been the auto side of it ... it is still connected to the B&G #7 Junction box ...

The #7 box appears to have the transducer cables enter and then a cable goes to the 'Blue Box' ... with possible feed back into the #7 for data out to the display ??

I am of a mind to remove one of the speed logs and just stay with one .. as they are very close to keel line ahead of the actual keel.

That's a good system, and I would preserve it if I were you.

Do you have any kind of sailing computer in that setup, maybe an old Hydra or Hornet?

The old B&G logs had a tilt switch which would switch you over to the lee side transducer when the boat heeled. A very simple, reliable and good system.

If you don't calibrate your logs much then you might not notice, but the windward side transducer will always under-read when there's more than a certain amount of heel, even if they are pretty close to the centreline. This will throw off your true wind and your laylines. Your system is a very effective way to solve that.

 

[Refueler]

That's a good system, and I would preserve it if I were you.

Do you have any kind of sailing computer in that setup, maybe an old Hydra or Hornet?

The old B&G logs had a tilt switch which would switch you over to the lee side transducer when the boat heeled. A very simple, reliable and good system.

If you don't calibrate your logs much then you might not notice, but the windward side transducer will always under-read when there's more than a certain amount of heel, even if they are pretty close to the centreline. This will throw off your true wind and your laylines. Your system is a very effective way to solve that.

Sailing Computer as you put it - may be that 'blue box' .. it has orientation arrows scribed onto the case ...

But tbh - I just want to be rid of the tangled mess ... I'm not bothered about a % here or there about speed ... my pal and I both have bad backs and decided that racing may be a thing in our past ...

Would be nice to get the wind / tactic displaying correctly though ... which I think is being affected by the mess installed.

 

[Blueboatman]

Whatever happens if you remove one log?
Well
If you remove one piece of drag then the speed on the other working log should- er- increase a bit.
So that’s good

It’s ok, I was going anyway

You probably need a bomb disposal guy who knows which wire to cut

 

[Refueler]

Because the two logs are through hull .... wondering if worth sorting a manual switch that both can feed to and I decide which feeds the network ? Seems a bit daft having two logs and only use one.

 

[Refueler]

Whatever happens if you remove one log?
Well
If you remove one piece of drag then the speed on the other working log should- er- increase a bit
So that’s good

It’s ok, I was going anyway

How would one cause drag on the other ??

The only interaction without change-over switch - would be the pulses of each would be out of synch .. possibly be regarded as faster due to the increased number of pulses seen ? But most likely - speed would not show due to interference of one to the other.

Brings me back to manual switch ? Hopefully its only the NMEA wire that needs switching...... once I identify the two tranducer cables !

And why did the 'Blue box' have connection to the analogue KNOT meters .. one in switch panel and other in hatch garage ??

 

[Dockhead]

Sailing Computer as you put it - may be that 'blue box' .. it has orientation arrows scribed onto the case ...

But tbh - I just want to be rid of the tangled mess ... I'm not bothered about a % here or there about speed ... my pal and I both have bad backs and decided that racing may be a thing in our past ...

Would be nice to get the wind / tactic displaying correctly though ... which I think is being affected by the mess installed.

Well, even if you're not racing, if you care about knowing true wind, if you care about knowing your laylines, you need good STW data.

It's more than a % difference here and there -- the data will be way off on the wrong tack. That means your laylines (I think what you are calling "tactic") will be way off.

It's a big fight to get anything like decent STW data. It's the hardest data to measure. Speaking for myself, I would never do anything to consciously to move backwards.

Obviously it's your boat, so you should do what you want. Just my two pence.

 

[Refueler]

Tactic ... display ... my B&G has two wind displays ... the full 360 deg WIND and the 60 deg TACTIC ...

As a trained ships navigator originally - vector diagrams and all that are old hat to me ...

But if I can get one 'ducer' talking to the Network without interference from the other - I stand a chance of the WIND displays behaving themselves.

 

[Dockhead]

Tactic ... display ... my B&G has two wind displays ... the full 360 deg WIND and the 60 deg TACTIC ...

As a trained ships navigator originally - vector diagrams and all that are old hat to me ...

But if I can get one 'ducer' talking to the Network without interference from the other - I stand a chance of the WIND displays behaving themselves.

Are the two speed logs interfering with each other? If so, that should be easy to fix. It's just simple wiring and a tilt switch.

Are you talking about displaying true wind, or apparent? If you're talking about apparent, then you need need any kind of speed data, good, bad or otherwise, for that -- apparent wind is directly measured.

True wind is the challenge. That's how you determine a layline, that's how you know how close to DDW you can go, that's how you know what the wind will be like after you make a turn, etc. etc.

If you care about any of that at all, then you really want as good STW data as you can get.

 

[shanemax]

Satellite gives you very accurate SOG, but tells you zero about STW! These are completely different things.

You must have STW to calculate true wind, laylines, and to have any idea of whether you are trimmed right and sailing at the needed speed.

SOG is not a substitute for STW.

STW depends on whether you are going with the tide, against the tide or across the tide at a variety of angles also how many hours after/before high water plus if there is a surge/anti surge and also on parts of the coast if there are any back eddies and if your log tells you all of this well done ??? Perhaps if you are totally out of sight of land for a prolonged period it may have a use. to give you an estimate of distance travelled and I deliberately use the word estimate.

 

[Mistroma]

I

STW depends on whether you are going with the tide, against the tide or across the tide at a variety of angles also how many hours after/before high water plus if there is a surge/anti surge and also on parts of the coast if there are any back eddies and if your log tells you all of this well done ??? Perhaps if you are totally out of sight of land for a prolonged period it may have a use. to give you an estimate of distance travelled and I deliberately use the word estimate.

I find it annoying if the log stops working due to fouling. I lose true wind as that's used to compare movement and calculate from apparent.

Pretty silly actually as GPS data is more useful. e.g. Holding station in a strong current should show apparent and actual as being the same. However, my Raymarine plotter only uses the log. Imagine moving at 6 knots into a 6 knot current. If wind is 5 knots from ahead GPS would show 5kts apparent but log data makes it 11kts as the log has 6kts.

I don't know if Raymarine changed this on more modern kit. I never understood their logic as the plotter has a built-in GPS and therefore assuming you'd only have a paddlewheel log made no sense.

 

[LittleSister]

The advantage of having two logs you can switch between is you can choose the reading you prefer!

 

[Chiara’s slave]

STW depends on whether you are going with the tide, against the tide or across the tide at a variety of angles also how many hours after/before high water plus if there is a surge/anti surge and also on parts of the coast if there are any back eddies and if your log tells you all of this well done ??? Perhaps if you are totally out of sight of land for a prolonged period it may have a use. to give you an estimate of distance travelled and I deliberately use the word estimate.

I think possibly you could do with a shore based nav course.