What is more accurate for speed, navionics or nasa log?

[vyv_cox]

The "jet of water" that some talk of, will go no higher than the water level outside the boat, so can we stop the exagerations please.
You are making it sound like the fountain of youth from long lost past. It may go off at an angle in some deep bilges, but it is just a bit of water through a 32mm diameter hole, that one can hold back with the palm of one's hand. The hard bit is trying to clean the impeller with the other hand whilst it slips further into the bilge on the end of the wire.
Teach you not to keep losing the blinking blanking cap.

Rather than the 'jet of water' it's the astonishing amount of daylight to be seen down the hole that always fascinates me.

 

[dunedin]

Very simple rule of thumb:: GPs speed for navigation, Log speed for sail trim etc.

Except in places with very strong tides - Orkney, Sound of Luing, Morbihan etc.
When boat speed circa 5 knots but SOG is 10 or more, sail trim needs to match where the apparent wind is due to the speed over ground.

 

[Daydream believer]

Rather than the 'jet of water' it's the astonishing amount of daylight to be seen down the hole that always fascinates me.

Next you will be telling us that you once saw an Orca peering up at you

 

[flaming]

Except in places with very strong tides - Orkney, Sound of Luing, Morbihan etc.
When boat speed circa 5 knots but SOG is 10 or more, sail trim needs to match where the apparent wind is due to the speed over ground.

Not really. The only thing that is a measure of the potential power available to your sails is the difference in velocity between the water and the air.

After all, if you are in a 5 knot tide and a 5 knot wind, if they align then you have 0 knots of "true" wind to use. If they are opposite you have 10 knots. But your ground wind would read 5 knots in both cases.

So it would only be the water derived "true" wind that would have any relevance to the sails you might choose etc.

 

[oldharry]

Except in places with very strong tides - Orkney, Sound of Luing, Morbihan etc.
When boat speed circa 5 knots but SOG is 10 or more, sail trim needs to match where the apparent wind is due to the speed over ground.

Well if you WILL insist on sailing in these outlandish places......! It actually can be like that in the Neeclles channel at the western end of the Solent where tides can run 4+kts, Even Chirchester harbour entrance, where I have made -.5kt SOG with 5.5kts on the log.

 

[Snowgoose-1]

People calling it ‘The Fountain of Death’ feeds the irrational paranoia of many people to cleaning their log impeller…. It’s a ridiculously easy and trivial task in reality.

PS. I question how commonly the term is used. In 50 years of sailing I’ve never heard it.

Jeez.. Fountain of death , a term used on these forums in the past. If anything to lighten things up. It seems that some folks on here just want to finger wag and judge for no good reason. Or is it just to satisfy there own insecurities ? You always know when it's preceded or followed by how many years you have been sailing, teaching or whatever .

 

[john_morris_uk]

Jeez.. Fountain of death , a term used on these forums in the past. If anything to lighten things up. It seems that some folks on here just want to finger wag and judge for no good reason. Or is it just to satisfy there own insecurities ? You always know when it's preceded or followed by how many years you have been sailing, teaching or whatever .

Whatever. I’ve still never heard of the expression and I’ve been on these forums a few months now too.

 

[vyv_cox]

Whatever. I’ve still never heard of the expression and I’ve been on these forums a few months now too.

New to me too and I have been using this and other forums for a few years now.

 

[Chiara’s slave]

Whatever. I’ve still never heard of the expression and I’ve been on these forums a few months now too.

I haven’t heard it either. And whilst it’s disconcerting to me 5 minutes after stepping on board a strange boat, doing it on my own is routine. Ours is only a foot below the waterline.

 

[Babylon]

Sadly, it is a practice that most skippers have a morbid fear of!

I, conversely, have a morbid fascination with taking as long as I dare watching the sea come in before inserting and screwing down the log/blank...

I don't know about the Nasa unit, but my Raymarine one has a rubber flap in the barrel somewhere that reduces the inflow of seawater to a dribble. (Any spillage then drains aft under the shallow bilge to the deep one beyond the engine, from where it is periodically pumped out using the Henderson.)

If things go pear-shaped, which of course they never have in 16 years of regular swapping, then there's always the dedicated softwood bung attached by string to the blank... people do have these, don't they?!

 

[john_morris_uk]

I, conversely, have a morbid fascination with taking as long as I dare watching the sea come in before inserting and screwing down the log/blank...

I don't know about the Nasa unit, but my Raymarine one has a rubber flap in the barrel somewhere that reduces the inflow of seawater to a dribble. (Any spillage then drains aft under the shallow bilge to the deep one beyond the engine, from where it is periodically pumped out using the Henderson.)

If things go pear-shaped, which of course they never have in 16 years of regular swapping, then there's always the dedicated softwood bung attached by string to the blank... people do have these, don't they?!

I confess that my softwood bung is in a locker about a metre away.

 

[Refueler]

I'm one who rarely removes the log ... yes - it often fails to show speed when first setting off ... but a burst of full throttle (Superanne hits 9kts at WOT ) soon sorts that out ...
Having had the mount tube leak in the past ... I am not looking to have it again ... The Echopilot log is a very tight fit in the tube and always feels like somethings going to 'give' before it comes free.
When I have removed a NASA - that was a lot less 'tight' and came out easy.

Thinking about Echopilot and Nasa ... I know not really of much interest to most - but they are different diameters ... Two years back - I wanted to swap to the NIB Nasa I have ... my display had failed on the Echopilot and I bought a complete Nasa Dual unit ... but a kindly forumite had a display unit they kindly fwd'd to me ... so the Nasa sits in its box unused.

 

[Daydream believer]

I had an Echo pilot set of gear, for a while, but it was useless after 3 years & manufacture moved to Philips in the Netherlands, so there was no backup from them. I bought it to replace the equally useless NASA stuff. That replaced the failed Simrad gear supplied with the boat. Currently giving Raymarine a go. But not holding my breath.

 

[Chiara’s slave]

I had an Echo pilot set of gear, for a while, but it was useless after 3 years & manufacture moved to Philips in the Netherlands, so there was no backup from them. I bought it to replace the equally useless NASA stuff. That replaced the failed Simrad gear supplied with the boat. Currently giving Raymarine a go. But not holding my breath.

My log and sounder are Raymarine. Factory fitted in 2001, still working. Well, ok the log now needs a new impeller and spindle but thats my fault.

 

[STATUE]

It depends on where the paddle log is. Inevitably water has to take a somewhat longer route around a hull, than the hull straight through the water. Hence the need to calibrate the paddle log to compensate for the slightly higher speed of the water around the hull.

I had this with a B&G paddle log. Despite cleaning the paddles, it lasted at most 2 weeks.
Then someone told me that up in the 'arch' on the paddle cavity, little tiny shrimps and their mates lie, sniggering at you!
Poke a cable tie up there.

 

[Refueler]

I had an Echo pilot set of gear, for a while, but it was useless after 3 years & manufacture moved to Philips in the Netherlands, so there was no backup from them. I bought it to replace the equally useless NASA stuff. That replaced the failed Simrad gear supplied with the boat. Currently giving Raymarine a go. But not holding my breath.

My Echo Duo is nigh on 30yrs old ....

Only two things have needed action :

1, Display head failed after more than 20yrs.
2. Speed log developed a leak and had to be removed and rebedded.

Something that has not affected the log at all - to my surprise - when I lifted the log to try repair leak alongside ... the log is cracked in its body ...

I immediately grabbed the new Nasa I had on bench - but of course does not fit as they have different diameters ! I

I applied PU waterproof glue ... sanded back .... refitted and its been fine ...

Every log I've known in all the years of boating ... the #1 cause of failure is 'fouling' of the impellor - whether old style 'screw type' or the paddle wheel as most have today ...