If an oars man rowed:

Discussion in 'Boat Design' started by BHOFM, Aug 2, 2009.

  1. BHOFM
    Joined: Jun 2008
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    Location: usa

    BHOFM Senior Member

    Twelve miles in six hours with a 175lb boat, flat bottom
    medium rocker, and he weighed about 250lbs and tried
    to maintain around 20/24 strokes per minute. There was
    near 0 wind and only a few swells from power boats.

    How many calories did he burn??

    If this is the wrong place for this, someone can move it
    for me. I looked around and didn't see a better place??
     
  2. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Twelve miles/six hours= pretty slow. There are a bunch of variables to address. ...The boat must have been very short, something like an 8 foot dink, or he was rowing against a considerable headwind or current, or he was not putting much strength into his rowing strokes., etc..... 20 strokes per minute x 6 hours x 60 minutes = a lot of strokes. One would need to calibrate the question more completely to arrive at a reasonable approximation of calories used. If we knew how much pressure was placed on the oar blade, duration of pressure, and the lever ratio, we could make an educated guess at the amount of work done. That could be translated into calories or kilowatts or whatever.
     
  3. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    A rowing machine gives 1670 for light effort (your criteria), 3300 for moderate effort, 4050 for vigorous effort and 5715 for very vigorous effort. Ball park figures for the same in your boat not fighting wind or waves would be similar.
     
  4. BHOFM
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    BHOFM Senior Member

    I am not a high performance oarsman. I do it for relaxation
    and getting away.

    I am also trying to loose some weight.

    I stopped several times to rest, get a drink and even fished
    a little, one small bass, 1lb maybe??

    Had lunch, salad, apply sauce, lime water.

    The oars are 7 1/2' flat bladed with a 27" in board. As to
    the pressure applied, very light?

    Was the 1670 for the entire trip?
     
  5. BHOFM
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    BHOFM Senior Member

    Steve,

    How is the scow coming??
     
  6. Guest625101138

    Guest625101138 Previous Member

    Take 70W at 20% efficiency for 5 hours gives 1750Wh or 6300kJ.

    You could have 5 by 65g Mars bars or 20 average sized apples. Or whatever else takes your fancy to replenish. If you do not replenish then you will burn a bit of fat.

    If you do not eat ant extra then you will lose about 200g (say 1/2lb) each time you do it. Initially you will lose water so it will look good. You might even start to build a bit more muscle. The fitter you get the faster you move so you tend to burn more in doing normal things. Do it a few times regularly and you will get the endorphin rush.

    Rick W
     
  7. BHOFM
    Joined: Jun 2008
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    Location: usa

    BHOFM Senior Member

    So, the basics are, it is a better way to get in shape than
    to try to loose weight??

    My right arm is weaker than my left, this is the main
    limit to my rowing power. I am a polio survivor. The difference
    will not change, even if I improve my strength.

    I do enjoy the rowing. It is a little funny, I had several
    people stop and check to see if I was OK. You don't see
    any row boats on the lake. I have had several people tell
    me it is the first one they have ever seen.
     
  8. Guest625101138

    Guest625101138 Previous Member

    I try to do dedicated exercise daily and at present do one good run on the boat each week. I did 22km on Saturday in a little over 2 hours. Fuel cost was 3 Mars bars.

    But I reckon my boat moves a bit easier than most - I expect a lot easier than yours.

    Exercising on water is much more enjoyable than on land. Even if it is only going up and down a rowing course - I do prefer a few twists and turns though.

    Rick W
     
  9. BHOFM
    Joined: Jun 2008
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    BHOFM Senior Member

    It is just a simple boat, sails very nicely. Rows easily but
    lacks directional stability when you stop rowing. Under
    power with the dagger board and rudder it is fine, but
    without them, it is a cork.

    I was thinking of fitting a skeg this winter??

    [​IMG]
     
  10. Guest625101138

    Guest625101138 Previous Member

    Mine is a bit more like a racing greyhound:
    http://www.boatdesign.net/gallery/showphoto.php/photo/15138/size/big/cat/500

    Your next project could be a pedal outboard - see video clip. A friend sent me the attached clip of a drive we worked on together. It is a lovely sedate action but you move swiftly because you are using powerful muscles.

    It is not particularly expensive to build. Something a clock maker should enjoy. Can be the next winter project. Takes a little setting up and attention to detail to get it to be reliable.

    I have the same pedal system in this boat but a conventional shaft rather than the outboard:
    http://www.youtube.com/watch?v=PYoW3XjHRbw

    Rick W
     

    Attached Files:

  11. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    80% done and 80% to go (mostly finishing) I hope to splash it towards end of September. I have one more day of vacation to burn before 14 oct. Blew through two other deadlines so hopefully this one sticks. Trouble is...I'm gonna be in the middle of moving during the next 10 days or so so those are probably a lost cause.
     
  12. terhohalme
    Joined: Jun 2003
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    Location: Kotka, Finland

    terhohalme BEng Boat Technology

  13. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Skeg would definitely help rowing, but if you sail it as well, then its hard to predict the effect.

    Why not build a simple smaller, fixed rudder to attach to the existing rudder pintles to act as a 'rowing skeg' - a lot less work for the same effect.
     
  14. BHOFM
    Joined: Jun 2008
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    Location: usa

    BHOFM Senior Member

    OK! I have it figured out!

    I need to build oars. It is more work than using them!

    :p :p :p

    Thanks for all the input.
     

  15. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    BHOFM: Your boat looks much like my own. Thus, I congratulate you for your impeccable taste in small boats. Flatties are deceptively competant. Goldilocks is more narrow than your boat appears to be. 37" at the chines. She rows very well, and goes sweetly and quietly with a tiny 23 pound thrust electric troller. About 4.8 kn at full throttle. The sail is a 59 square foot sprit boom rig that Bolger specified for his Gypsy. Not much sail for a 16 foot boat but entirely adeqate and demonstratedly capable of getting the attention of much more sophisticated sail boats of that size.

    When rowing I lash the tiller/rudder amidships. She goes where you point her. No skegs or skid shoes clutter up the bottom. I am also a BHOFM who has not lost much weight as a result of rowing. No doubt, I might shed a few pounds but for my recurring appetite for single malt scotch.
     
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