Boat In Tow, HP ?

Discussion in 'Boat Design' started by Wavewacker, Jul 23, 2016.

  1. Wavewacker
    Joined: Aug 2010
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    Location: Springfield, Mo.

    Wavewacker Senior Member

    Consideration is being given to towing a small (15-18'x 4') flat bottom skiff or jon boat behind a 23'-28' sail boat under power or sail. Rivers, lakes, ICW, not off shore.

    There are a lot of decent trailer sailor Hunters, Odays, Catalina, S2's and other sail boats out there that are pretty cheap. 23-28' under $5K, mostly the 70's and 80's bunch!

    I can't build a boat to match even these older boats, one of the draw backs is draft but many can be beached. Pulling a small flat bottom could serve as a dingy, may be some additional fuel and gear. Just a water trailer.

    So, most of these old glass boats cruise at hull speed with 5-10 HP kicker's. Say we move up to 15 to 20/25 HP just for some reserve power.

    How would I calculate the additional drag towing? What's the better hull design to be towed, flat I would assume but I'm often wrong. How much more power needed if any?

    I'm not thinking of pulling a loaded barge, may be a couple hundred pounds.

    It would be nice to know the little towed craft would be self righting, but I doubt we'd ever be going over 6-10 mph. Might use some bows and canvas over the cockpit to encourage it to roll up top side????

    This line of reasoning follows the buy a boat and go, build a first time small boat quickly and go.

    Thoughts please!
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    You can get an inflatable kayak for two persons for under $100. Towing a dinghy is a hassle. If you get into any weather or some bonehead on a powerboat makes a wake next to you, the dingy will swamp and/or capsize.
  3. JSL
    Joined: Nov 2012
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    Location: Delta BC

    JSL Senior Member

    Yes, avoid towing if you can but if you do tow, get a smaller boat (8' for a 28' is about the max.) make sure the tow line floats, is visible, and you have someone manage the 'towee' (your jon boat) when maneuvering & docking.
    PS: keep a knife or axe handy to chop the towline in an emergency. In a current or rough seas your 'towee' can cause real problems.
    Last edited: Jul 23, 2016
  4. Wavewacker
    Joined: Aug 2010
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    Location: Springfield, Mo.

    Wavewacker Senior Member

    Got it guys, thank you, it's not a great idea to have a big trailer! I have an inflatable, I'll use that! Okay, the smaller build will be for itself, not part of the armada. Thanks again! :)
  5. philSweet
    Joined: May 2008
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    For what it's worth, I routinely towed a 16' skiff behind a 28', and later a 38', sailboat. I towed it off shore sometimes, or just around the Florida keys and out to the Bahamas. The Cal 28 had a 15hp Mercury with extended 25" shaft in a well. The Catalina 38 has a 27 hp diesel, but from a practical standpoint in warm weather, its only about 18hp or so. The skiff is basically a big Mac Dinghy type that is very light, tracks well with a bit of board down, and has lots of reserve buoyancy. The dinghy tops out about 20 knots because it is a semi-planing hull. The biggest issue is the skiff trying to overtake the sailboat downwind in light air - because it surfs on the swell. When that happens, I drop the motor leg to add drag. 25-33' sailboats are a dog to cruise in because they are too big to beach and too small to handle a decent dinghy. I can just get a 9.5' dink on my 38'er. Towing something of decent size is better than trying to tow an 8 or 9 footer.

  6. Wavewacker
    Joined: Aug 2010
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    Location: Springfield, Mo.

    Wavewacker Senior Member

    Well Phil, you revived the thought with practicality.

    Let's say we tow a 16' canoe. Put a deck on the old canoe and waterproof canvas as a skirt, some dry bags with gear lashed down on the bottom. Might even have some leeboards dipping down. If it flips it flips, keep going and it should right itself.

    A few years ago, I saw a dingy pulled with a line through an aluminum tube with bumper balls at each end. Closely hauled with the line tight. That way the dingy couldn't kick you in the tail or pass you. Seems to me if you used two lines like that, one to each side the towee would have no place to go but to follow, more like a trailer.

    Now, a small garvey, jon, sharpe? Any significant power requirements?

    I had to swim pulling several boats along at times, one was a 5,000 lb cuddy cabin for about a half mile from running aground in the dark. I'm not even one HP, but it was more like tug and pull, swim ahead and repeat. That was a long swim!
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