Conversion from trailer-sailer to low power motor boat

Discussion in 'Boat Design' started by Dr. Peter, Apr 27, 2010.

  1. larry sellers
    Joined: Sep 2012
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    Location: chico ca

    larry sellers Junior Member

    Yes Mr. May, a fine job! A rather longer story of your project and additional pictures would be very welcome! Please tell us more...
     
  2. James May
    Joined: Jan 2013
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    Location: Christchurch, New Zealand

    James May Junior Member

    Hiya,
    well if you have time....
    unfortunately i have very few photos of the build (suprising considering i am a photographer)
    we have had the boat a few years, we originally brought it from a older couple who had let the condition get away on them. They were so pleased for the boat to go to a new home that i actually had to talk them UP in price!!
    that first spring i started dealing to the obvious rot in the topsides, but it quickly become clear that the rot was terminal.
    I patched it up enough to enjoy a summers sailing with my very young family and was still only a few hundred out of pocket.
    As the hull looked remarkably sound, i had not done much more than tapped the few stringers i could find to check for any soft spots and inspected (not too closely) the outside of the hull.
    sometime into the first summer i decided to open up a little more space in the outboard well to make space for a slightly larger 4 stroke outboard and discovered that the hull itself was Glass, not just GOP.
    this discovery, along with the degree of rot in the topsides was the encouragement i needed to build something i have always wanted to build. (i'm one of those, "it's the journey", not the destination types)
    so i sat down with a pad and paper and started to draw up a slightly more usable version of the yacht.
    i had to build all of the cabin without glue, in a rented house's garage, as at the time we had to move out of our house while it was demolished (canterbury earthquake damaged) and while the new house was being built.
    once we had moved home i simply had to pull off the old cabin and fit the new one into place and glue as i went, then built the decks and sides etc.
    i used BS1088 Meranti and Gaboon for all the timber except the trim and fold down seats which is Kwila.
    I think she still needs some more balast as the new top is a lot lighter than the old one.
    I stuck to the drawings as best i could, but a lot had to be made as i went, and i am terrible at maths, so the thing the pictures don't show is the relief in my face that the boat is atop the water, not under... Someone did ask me once how i would know if i had done it right... i said when it slides off the trailer if i can see the entire boat, right way up, it probably turned out ok...
    After doing some maths, i think she took around 1300-1500Hrs (im sure most of that was sanding) and all told including original purchase maybe as much as $3000. not including the motor.
    a quick run down from the bow:
    There is a door in the front of the cabin to get in and out without walking down the sides or over the top of the cabin. Then inside the forward berth remains pretty standard, the drop Keel is still in and also serves as one side of the galley which has hot and cold water and a wee drop in table.
    There is a companionway and seating opposite.
    Further back opens onto the deck, which is too low to be self draining so is drained into a tank underfloor and pumped overboard from here.
    The deck i used ripped down ply for decking and filled in between with filler to give it a nice white grout look, there is a seat across the rear and a dropdoen seat on either side of the deck. then there is the motor well which ahs been adated to take a 25Hp Mercury (only 2nd hand one i could find that takes remotes and is electric start)
    then a little boarding platform.
     
  3. James May
    Joined: Jan 2013
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    Location: Christchurch, New Zealand

    James May Junior Member

    now that she is complete, i think i'll make her a little stitch and glue dingy to tow around and start looking at plans for as larger boat i can make fit a trailer without permits.. which of course will also be displacement.
    i know i have only just joined the forums but i have been reading them for a really long time, so thanks for the inspiration, especially the member who had been using his hartly without sails!!
     
  4. James May
    Joined: Jan 2013
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    Location: Christchurch, New Zealand

    James May Junior Member

    I still have a couple of wee jobs to do like the tidy up the boot topping and other bits of paint touchup
     

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  5. whitepointer23

    whitepointer23 Previous Member

    Great job. Looks good. Love your work on top gear to.
     
  6. James May
    Joined: Jan 2013
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    Location: Christchurch, New Zealand

    James May Junior Member

    Hahahaha,... while i'm a car nut, (also built rally car over last winter) unfortunately i am not the wealthy James May...
     
  7. Dr. Peter
    Joined: Mar 2010
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    Location: Zeerust, Victoria, Australia

    Dr. Peter Junior Member

    Well Done

    James,
    I have been focussing on my sailboat lately and my Hartley conversion project has stalled for the moment, but it is not out of my thoughts. I just got back from 9 days sailing around the Gippsland Lakes, Victoria, Australia where you see a lot of converted boats - that is sailing hulls with new top structures. Very inspiring - as were your photos. Well done - 'Sweet as ... bro'
     
  8. sltak
    Joined: Feb 2011
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    Location: New Zealand

    sltak Junior Member

    I was looking at a Noelex this morning, wondering how it would convert to a power boat. Pity to cut down such a beautiful sail boat, but on the other hand if it is past its sailing days....it seemed to me to be such a sweet hull it wouldn't need much power. Tell me, how does yours go with the 25hp mercury (I would have though this to be way to much)- does she plane, or do you just use a small amount of the power. And how does the outboard well cope with the stern wave? I have been thinking about this for a while, would be very interested.
     
  9. sltak
    Joined: Feb 2011
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    Location: New Zealand

    sltak Junior Member

    I forgot to add, I am also considering a Hartley 18, which is what drew me to this thread (Dr Peter) - the general consensus seems to be that 10hp is about all the Hartley 18 can absorb. In theory. Has anyone actually tried a 15hp on one of these? I want to do displacement speed most of the time, but also want to work up a river and might need to stem about 5 knot current. Is it feasible by over-powering a displacement hull like a Hartley 18? I know know it is not feasible in theory - I want to know what happens in practice.
     
  10. larry sellers
    Joined: Sep 2012
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    Location: chico ca

    larry sellers Junior Member

    My opinion is that the general rules apply - double the speed requires power squared. And that has a large effect on fuel consumption and thus range. Rivers are full of debris - punching a hole in a glass hull is pretty easy. If possible wait for tidal influence to quiet the current and go at a moderate speed - safer. Do not be hasty. Best.
     
  11. fredrosse
    Joined: Jan 2005
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    Location: Philadelphia PA

    fredrosse USACE Steam

    "double the speed requires power squared", implying 2Xspeed = 4Xpower.

    Not so with a displacement hull, actually the relationship is a cubic function, so double speed would require 8x the power!

    This is all considered with a displacement boat within the realm of displacement boat speeds, and that approximately means staying at less than 1.35 x the squareroot of the waterline length. Trying to push a displacement hull much faster results the cubic function raising to a fourth or fifth power function, power required skyrockets.

    For planing hulls there is a different set of functions, however I think, with a planing boat, double speed would still require more than 4Xpower.
     
  12. larry sellers
    Joined: Sep 2012
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    Location: chico ca

    larry sellers Junior Member

    Yes, excuse me. I was careless and I knew better. However the principle with respect to range and safety remains - obviously buttressed. I was perhaps thinking about the energy available to punch a hole being squared... I used to do rivers a lot. When the current was too strong I simply stopped in a safe place and found something to do, read, whatever.
     
  13. sltak
    Joined: Feb 2011
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    Location: New Zealand

    sltak Junior Member

    Thanks for the reply guys. I have no plan to go up a river at planing speed. Just want to be reassured I can move ahead in the upper reaches of a river (away from tidal influece) at more than a snail's pace.

    Not disputing the theory, but very keen also to hear from Dr Peter and James May as to precisely how, in practice, their particular hulls behave under "too much" power.
    The Hartley 18 and the Noelex 22 are rather different hull forms, albeit both sailboats - which makes the question even more interesting. I am familiar with both, as sailboats - but had not thought before about how much power they could take, and am right now considering one or the other as a conversion to a power camping cruiser.

    If it is not straying too far from the thread, I would be interested in more advice on river cruising - in a boat such as a trailer-sailer converted to motor boat. Anyone in new Zealand tried the Waikato above Ngaruawahia?
     
  14. Dr. Peter
    Joined: Mar 2010
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    Location: Zeerust, Victoria, Australia

    Dr. Peter Junior Member

    Hartley 18 @speed

    In its previous life as a sailboat my Hartley did plane once. It was on a screaming reach in about 20+ knots of wind. There were three of us on board and everything was sheeted on pretty hard. We were going really fast.

    As a motorboat, going upstream with the throttle wide open, there is a lot of noise, a big wake, and only a marginal increase in speed. To be frank, I usually set the speed based on how irritating I find the engine noise. I would rather travel a bit more slowly for a bit more peace.

    That might be a case for a larger engine like a 15hp - more oomph at less revs. More speed and relatively less noise. It might have a better charging coil too if charging batteries is important.

    Another approach is to use a particular engine with a different pitch. I have used a 5hp single cylinder two stroke and IMHO it is easier on the ears than an 8hp twin cylinder two stroke.

    This picture shows the current state of the boat. A single cylinder 5hp motor, a slot top, and a cut down mast as a ridge pole.
     

    Attached Files:


  15. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    If you want to get a bit more speed out of her, you might consider using some horizontal appendages under the aft quarters, much like the Bartender (below) does. This would offer additional area to prevent squatting so much and she'd be able to plane off, given enough power.

    [​IMG]
    [​IMG]

    There would be some experimentation necessary, so make them too big and cut them down until they work well.
     
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