How Necessary is a Knot Meter ?

[conachair]

Originally Posted by Cheechako

if you have a gps, totally unecessary... for a cruiser.

As a cruiser, I know from late night bar chats that I'm not alone in being a bit obsessed by getting as many free miles as possible. No idea how you would know how many you are or are not getting without something to measure distance traveled through the water.

Best days runs I've ever had was 70Nm just from the current, worth having a log just for the feeling of satisfaction

[bobconnie]

Boy to listen to some on here it's more important to tell the wife when your getting home ! then to have a simple DR tool! first a taff log don't show distance?, because of current? maybe so but it's one of the tools Ive used for 40 + yrs, and it works well enough for me ! cus it's another ck against my GPS ! but if I did not have a GPS as I did not have in yrs past I still wanderd around and always found home !! as the Indian said me no lost camp lost !! and I ALWAYS get home and the wifes always with me LOL give me a break your getting way overboard with trying to tell everybody whats up maybe?? just my 2 cents Bob and Connie

[Kettlewell]

No idea how you would know how many you are or are not getting without something to measure distance traveled through the water.

As a cruiser that has no interest for me. The thing I am interested in is miles over the ground. You can sail lots of miles through the water and not get anywhere if you are sailing in the wrong direction or against a current. By the way, many, if not most dinghy classes, race against each other with no instrumentation whatsoever, and they learn by reading the wind, the water, and by getting a feel through the seat of their pants when they are sailing fast and efficiently. Instruments are not required for that.

[conachair]

Originally Posted by Kettlewell

The thing I am interested in is miles over the ground. You can sail lots of miles through the water and not get anywhere if you are sailing in the wrong direction or against a current.

Er, exactly! So without knowing ditstance traveled through the water along with over the ground how can you get an accurate handle on what the current is doing?

A few miles left or right can make a big difference to free miles from the current and the pilot charts are not the real world. I can't see how you can know what the current is up to without knowing distance through the water.

[Cavalier]

On the few occasions the instrument has fouled up I've felt somewhat unconfortable. I always like having a backup option to GPS, especially in mountaineous coastal regions where your solid-angle of satellite visibility is diminshed and your SOG changes as new satellites rise on and existing ones set.

Paddle logs, when combined with GPS, give such good feedback regarding running currents and rough flow direction which a standard SOG doesn't give without another reference.

I knew someone who's paddle stopped functioning after a haul-out, and it turned out that the guy who he'd hired to jet-wash the slime off the hull had thought it was 'cool' to use the stream to make the paddle whizz at high speeds! Though i've always thought it prudent to pull the instrument and replace it with the blank before haul-out to ensure that it doesn't get damaged by any strops sliding around. Besides, as long as the paddles are given a slight wash now and again they tend to work well: just part of the standard 'automatic' checklist at the start of the weekend.

A paddle-log and depth log are essential backups - i'd just leave the instrument there IMHO as at least you'll get some use out of it in the event your GPS packs in, even if that means you need to clean it to get it functioning while the rest of the crew are blowing dust of the paper charts and hand compasses!

[Kettlewell]

Er, exactly! So without knowing ditstance traveled through the water along with over the ground how can you get an accurate handle on what the current is doing?

Based on a lot of observation of how my boat sails in different wind conditions, at different angles, etc. I know what its speed should be over the bottom and if I glance at the GPS and it says something different it tells me whether or not I'm getting a help from the current or not. But, in any case, I am usually trying to get somewhere, so the exercise for me is to figure out when I might get there and what is the best angle to sail at to achieve that. Yes, someone with accurate instruments can determine that with a greater degree of accuracy, but the seat of the pants method has served me fine for 30+ years and I think there are advantages to watching what is happening around you instead of the instruments. For a good chunk of that time I had no GPS, no knot meter or log, and nothing by dead reckoning to go by. Makes life more enjoyable for me to keep it simple. My goal is not to extract every tenth of a knot, but is often to adjust course for greater comfort, or to pass by something I want to see, or whatever...But, if you can keep a knot meter working well enough to give you more accurate speed information and you want it, more power to you, but I think many of us find that it is hard to keep these things working with any accuracy. So instead you are usually getting misleading information.

[Cavalier]

Originally Posted by Celestialsailor

I'm sick of knot meters...I truly am! Half the time they never work due to the paddle fouling and their accuracy is terrible.

Raymarine Marine Electronics - CS4500 Ultrasonic Speed Sensor

A bit pricey - but you can find lower cost versions which do the job.. and at the end of the day all of the work in plugging, filling, GF'ing over a hole, sanding, recoating and anti-foaling the area isn't going to cost a couple of dollars either..

I have no experience with ultrasonic speed transducers.. and if they manage to narrow the expectations gap... maybe someone else has experience on the matter?

[Wotname]

This is getting better than a anchor or mono / multi thread- who would have thought it.

[Cavalier]

Originally Posted by Wotname

This is getting better than a anchor or mono / multi thread- who would have thought it.

surely then the OP's question should have been, "Paddle-logs: should I have one or two of them?" ;-)

[conachair]

Originally Posted by Kettlewell

Based on a lot of observation of how my boat sails in different wind conditions, at different angles, etc. I know what its speed should be over the bottom and if I glance at the GPS and it says something different it tells me whether or not I'm getting a help from the current or not. But, in any case, I am usually trying to get somewhere, so the exercise for me is to figure out when I might get there and what is the best angle to sail at to achieve that. Yes, someone with accurate instruments can determine that with a greater degree of accuracy, but the seat of the pants method has served me fine for 30+ years and I think there are advantages to watching what is happening around you instead of the instruments. For a good chunk of that time I had no GPS, no knot meter or log, and nothing by dead reckoning to go by. Makes life more enjoyable for me to keep it simple. My goal is not to extract every tenth of a knot, but is often to adjust course for greater comfort, or to pass by something I want to see, or whatever...But, if you can keep a knot meter working well enough to give you more accurate speed information and you want it, more power to you, but I think many of us find that it is hard to keep these things working with any accuracy. So instead you are usually getting misleading information.

Can't disagree with any of that. On the cruising angle my main obsession gets more intense offshore, no way I could tell with looking at water what could easliy mean 10 more or less miles a day. And from experience it can be all over the place out there. Simple is fun, but there ain't much to do out there and seeing how many free miles you've had on the days run can be something to feel good about.

[Kettlewell]

True story. I worked in Newport back when the Americas Cup came to town back in the 70s and 80s. One year the British team came into our store looking for a new propellor for their towed Walker log--I asked them what it was for and they said they used it to calibrate the onboard instruments. A shark had taken their last spare propellor. So they were using a 19th century device to zero in their 20th century electronics.

[conachair]

Originally Posted by Kettlewell

True story. I worked in Newport back when the Americas Cup came to town back in the 70s and 80s. One year the British team came into our store looking for a new propellor for their towed Walker log--I asked them what it was for and they said they used it to calibrate the onboard instruments. A shark had taken their last spare propellor. So they were using a 19th century device to zero in their 20th century electronics.

I do that too!!!! At the start of a long passage The walker may well be quite accurate but the chance of catching a fish is above accuracy

[Astrid]

chance of catching a fish

Catching a fish with the 'fish.' I believe fish was a colloquial name for the rotar. I have a number of rotars a machinist friend of mine made for the Walker I have, should some hungry aquatic take an interest.

[Cheechako]

Originally Posted by delmarrey

I heard somewhere that "the one with the most toys, wins"!

In that case , you need a knotmeter foward and one aft so you can tell what's going on at each end of the keel...

[Celestialsailor]

Originally Posted by Cavalier

Raymarine Marine Electronics - CS4500 Ultrasonic Speed Sensor

A bit pricey - but you can find lower cost versions which do the job.. and at the end of the day all of the work in plugging, filling, GF'ing over a hole, sanding, recoating and anti-foaling the area isn't going to cost a couple of dollars either..

I have no experience with ultrasonic speed transducers.. and if they manage to narrow the expectations gap... maybe someone else has experience on the matter?

Well it's not like I would pull the boat for one thru-hull. I will do it in 2 years when I totally strip the bottom for an epoxy job. I'm relocating 3 other thru-hulls. So another one is no big deal. It takes me less than an hour to remove a thru-hull, back-grind it and laminate inside and outside (not all at once). We DIY here, so no outside labor.