Knotmeter or Speedometer without hole

The limited level in the description it looks like the data is derived from GPS, so will give SOG (Speed-over-ground) NOT velocity through the water so it may be very good for navigation, - but not for tweaking sailing performance, as it does not exclude tide and current movement...

Someone with electronic skills may be able to create an electronic device that forward looking transducer that emits sonar pulses and the returning echoes can be calibrated to give velocity through the water... A complex device prone to problems and difficulties in setting up... I have often thought of how to design such a device...

Injecting air bubbles into the stream? - - but how to ensure they 'flow' and that the bubbles of air do not stall behind barnacles to give a false reading? Some ships used to carry a small propeller on a wire, (that does not twist), that imparts the full spin to the instrument attached at convenient reading height aft... - a relatively simple mechanical device...

Alternately, I have a cheap depth sounder that attaches to the transom by a slide in - to a bracket permanently mounted - It has a paddle wheel but is easily removed... Not viable on my boat as that gets the prop wash so mine is mounted on a stick to give depth and anchor watch only...

 

Masalai,

You can buy off the shelf transducers that do this, but they are much more expensive than paddle wheel designes. Though they do work much better, since they dont have a habit of getting clogged all the time.

http://www.raymarine.com/ProductDetail.aspx?SITE=1&SECTION=2&PAGE=1877&PRODUCT=4237

 

Sailing and navigation is about speed thru the water, depth and a compass.

Airmar supplies many transducers, combo speed, depth and ultrasonic non fouling sensors.

http://www.airmartechnology.com/2009/marine/product-search-results.asp

http://www.airmartechnology.com/uploads/InstallGuide/17-263-01.pdf

 

In the United States we can buy used "Android" based phones - I'm not sure if they are available in the Philippines. Anyway they are usually sold for $150 or less. They have a GPS antenna in them - which does not require any phone service. You can download maps for free from your home internet connection, and use them without any service contract. So you could buy a used phone and use it without any additional cost. Especially when compared to paying $350 for a little puck that only tells you speed. That seems really expensive.

 

Thanks Jetboy. Android based phone are available here. All types, even China made. I bought my "Navigator" in UAE and was using it. Just got tired of it since newer model makes my old phone look like a brick and did not want to subscribe anymore. Grew a fondness for IPhone.

My Nikon camera also has a GPS and no subscription. Talk about technology.

 

I think I have seen some hand held GPS units in the $ 100- (U.S.) range - doubt they were mapping but can't remember - each time I look at them they have added more features and lowered the cost - the advantage of a regular handheld GPS unit is they should be water resistant

 

I actually just completed a trip from Panama City to New Orleans using nothing but a iPhone for navigation. The base phone plus a $3 app and all the free NOAA charts you can download. But this is getting pretty far afield from a day sailor wanting to know how fast he is going.

I would stick with the speed puck, they work great, have larger numbers, so are easier to read when mounted on the mast, and typically have much faster refresh rates than a phone. Plus the newer ones use small solar panels and an integral battery so you never have to worry about the charge level.

 

The Puck also has compass heading, lift/header info and remembers the max speed. I bought it so I could see it easily, because it was waterproof along with the other features...

 

Agree with Dough and Stumble. The puck has all the "marine" features. I have seen it in West Marine catalouge. WM is a good source of Speed Meters and there are a lot of transducer choices. Thru hull, impeller, pitot tubes.

However, if you are just going for occasional use, grab something that works (you may have one available but just don't realize it) Zip Loc it in a clear plastic bag and it is "waterproof".

 

For navigation purposes I'm interested in speed over ground more than speed through water.

 

Why don't you do it the old fashioned way.

Measure the length of the boat and have someone drop a (dead) fish in the bow and measure the time it takes the fish to reach the stern then use the apps in your mobile to............ eh......

find the speed using GPS.

 

What about a GPS Watch for Speed, i cant seem to find one? I know someone has to make it, there has to be one available by now, does anyone know of this?

 

REI has 33 listed online - many by Garmin - Looks like battery life in GPS mode might be a bit short

http://www.rei.com/category/40001902