Knotmeter or Speedometer without hole

Discussion in 'OnBoard Electronics & Controls' started by Amateur_Expert, Apr 21, 2012.

  1. masalai
    Joined: Oct 2007
    Posts: 6,847
    Likes: 119, Points: 0, Legacy Rep: 1882
    Location: cruising, Australia

    masalai masalai

    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...
     
  2. Stumble
    Joined: Oct 2008
    Posts: 1,884
    Likes: 67, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

  3. michael pierzga
    Joined: Dec 2008
    Posts: 4,865
    Likes: 114, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

  4. Jetboy
    Joined: Feb 2012
    Posts: 278
    Likes: 6, Points: 0, Legacy Rep: 65
    Location: USA

    Jetboy Senior Member

    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.
     
  5. rxcomposite
    Joined: Jan 2005
    Posts: 1,573
    Likes: 83, Points: 48, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    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.
     
  6. Saildude
    Joined: Jun 2011
    Posts: 84
    Likes: 9, Points: 0, Legacy Rep: 119
    Location: Seattle, Washington, USA

    Saildude Junior Member

    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
     
  7. Stumble
    Joined: Oct 2008
    Posts: 1,884
    Likes: 67, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

    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.
     
  8. Doug Lord
    Joined: May 2009
    Posts: 13,894
    Likes: 118, Points: 73, Legacy Rep: 1362
    Location: Cocoa Beach, Florida

    Doug Lord Flight Ready

    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...
     
  9. rxcomposite
    Joined: Jan 2005
    Posts: 1,573
    Likes: 83, Points: 48, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    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".
     
  10. DCockey
    Joined: Oct 2009
    Posts: 3,719
    Likes: 120, Points: 63, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

  11. rxcomposite
    Joined: Jan 2005
    Posts: 1,573
    Likes: 83, Points: 48, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    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.:D:):)
     
  12. soulofasailor
    Joined: Nov 2011
    Posts: 39
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Pittsburgh

    soulofasailor Junior Member

    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?
     

  13. Saildude
    Joined: Jun 2011
    Posts: 84
    Likes: 9, Points: 0, Legacy Rep: 119
    Location: Seattle, Washington, USA

    Saildude Junior Member

Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.