Low power day boat - protected waters.

Discussion in 'Boat Design' started by kerosene, Jun 25, 2014.

  1. kerosene
    Joined: Jul 2006
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    Location: finland

    kerosene Senior Member

    Designing minimal power day boat / camp cruiser - protected waters.

    Hi forum.
    I am contemplating a small powerboat for family use on small river and connected lakes.

    The SOR discussed with my fiance are as follows:

    Minimal ascetic boat. Minimal fuel use.
    General description of use: day trips and camp cruising on nearby river and connected lakes. A few narrow spots and quite shallow too limit the draft to 1 foot range.
    Range: (if electric) round trip to town is 30km, so 50km / 30nm should be plenty. At 6 knots that is 5h which is more than enough for a day. If gas outboard double or triple that.
    Speed traget: 6 knots is good
    passenger capacity:
    2 adults, 2 kids (sub 10yr) for max range trips. More kids or more adults for short ones. Preferably decently handles varied displacement (within reason).
    construction: easy to build. cheap. more further.

    Equipment:
    -cuddy cabin (room for naps, according to my better half no place is better for a nap than a boat under way). Barely sitting headroom, minimalist.
    -cooler (ice box)
    -storage for camping gear (as in a tent), food, PFD and portable gas stove
    -some kind of light canopy for light rain (not a rainy day boat) this cover can be more of a sun shade
    NO: porta potty or head, sink, anything fancy.

    I have been checking Atkin designs and other easily driven slow speed power boats (hard chine). Also the smaller ones like Kayleigh have been in consideration (though out board well is waste of boat length in my opinion, especially at that length) http://www.tracyobrien.com/Boat_Plans-Kayleigh_Plans.html

    Kayleigh and the "ugly" AF4 (http://www.duckworksbbs.com/plans/jim/af4/index.htm) are on the very minimalist end but they seem a bit too compromised and sort of not worth the effort + could be outgrown very quickly. Thus I am thinking more along the lines of a 22' / 6.5 meter narrow (less than 5' / 150 cm) displacement boats. Atkin has a few close to what I have in mind though they are mostly semi-displacement and (I think) over built for my scenario of broken lake landscape and near flat water)



    edit: added images for what is close to my heart in this searching progress
     

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  2. kerosene
    Joined: Jul 2006
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    Location: finland

    kerosene Senior Member

    So this is what I am nearing at in terms of hull:
    longer than the kaleigh or truly minimalist boats. Narrow.
    Transom will get tilted, still rough.
    cabin as in wanderer or less.

    If my speed target is in the 6 knot range and the chop I will face is quite minimal I am hoping tiny motor would do. I mean 1-3hp. Freeship resistance calcs give me anything between 500w to 1300w power required for 6 knots, depending on calc mode. I am a bit clueless here and respect real input vs me monkeying with software.



    Design length : 6.500 m
    Length over all : 6.488 m
    Design beam : 1.500 m
    Beam over all : 1.532 m
    Design draft : 0.363 m
    Midship location : 3.250 m
    Water density : 1.025 t/m^3
    Appendage coefficient : 1.0000
    Volume properties:
    Displaced volume : 0.737 m^3
    Displacement : 0.755 tonnes
    Total length of submerged body : 6.304 m
    Total beam of submerged body : 1.269 m
    Block coefficient : 0.2533
    Prismatic coefficient : 0.6145
    Vert. prismatic coefficient : 0.3308
    Wetted surface area : 6.849 m^2
    Longitudinal center of buoyancy : 3.062 m
    Longitudinal center of buoyancy : -1.424 %
    Transverse center of buoyancy : 0.000 m
    Vertical center of buoyancy : 0.288 m
     

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  3. parkland
    Joined: Jul 2012
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    parkland Senior Member

    What about going pontoon?

    Something like this:
    http://www.ebay.com/itm/New-house-b...58d37d3&item=191219185619&pt=Power_Motorboats

    Or this:
    http://www.ebay.com/itm/pontoon-house-boat-/281369324265?pt=LH_DefaultDomain_0&hash=item4182eb2ae9

    You could either buy or build, just buy the pontoon and deck kit, and build whatever you want.

    You were thinking maybe electric, so put some electric trolling motors, and batteries, maybe even solar panels on roof. Maybe a generator to charge the batteries if you need.

    Or electric trolling motors, plus a small outboard?

    You'll have a ton more room than a monohull, and a more comfortable nap, along with room for cooking and stuff, and still trailerable.
     
  4. parkland
    Joined: Jul 2012
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    parkland Senior Member

    And as far as cheap, when I looked, a set of 40ft pontoons was under 12k$ delivered to me, yes a hull could be built cheaper, but for aluminum, and the safety and simplicity of the design, it could be a best bet.

    If that isn't cheap enough, used pontoons can be had for a few grand sometimes.
     
  5. Westfield 11
    Joined: Apr 2008
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    Westfield 11 Senior Member

    I know this isn't what you want to hear, but the cheapest way to do this is a pontoon with two tiny used outboards. Probably only need 5 or 6 HP total split between the two sides to maintain 6kts. Keep an eye on Craigslist and you can probably find what you need for a couple of hundred bucks, if you can find something a bit larger, say 7 HP per side, you could run them at just above idle for great economy.

    Electric is the power of the future, but today, you would probably have to buy a lot of the stuff new which can get expensive. Gasoline is terrible stuff, but it sure is a great way to store a lot of energy in a small space. Unless you have access to a 240v fast-charger at each end of your 30m trip, you will have to allow at least overnight to recharge a drained power pack. With a pair of cheap outboards, you just buy a few more liters of fuel and away you go.
     
  6. kerosene
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    kerosene Senior Member

    no CL here and the boat I am looking for:
    1 way less of a boat than the pontoons posted
    2 project if my own. I know used is easier and likely cheaper (though not as cheap here as in the US, I am in Finland, updating my profile now)

    I get the electric and its limitations. I am not expecting same practicality and range from electric setup. about 1 hp for 4-5 hours and then charge sloooowly is what it would be. Being silent and the fun of building /using it would be the point. Gas would probably be cheaper over the lifetime use of the boat.
     
  7. BobE
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    BobE Junior Member

  8. parkland
    Joined: Jul 2012
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    parkland Senior Member

    22 ft used pontoon boat, tent trailer, solar panels, batteries, and a couple electric trolling motors.
    Hack those things together, save massive amounts of time and money.
    Maybe go 1 electric trolling motor, and 1 cheap 2 stroke gas motor, just for an emergency.
     
  9. SamSam
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    SamSam Senior Member

  10. Willallison
    Joined: Oct 2001
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    Willallison Senior Member

    I recently did this 7m electric launch for a local boat builder. With a slightly less elaborate fitout and some tweeks to the layout it could be suitable for your needs. Feel free to PM or email me if you think it may be of interest...

    http://www.imaginocean.net/#!noosa-launch/cxne
     

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  11. Petros
    Joined: Oct 2007
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    Petros Senior Member

    cheapest way to go is find something used, buy it cheap and do some alterations to get it the way you want it if necessary (or just use it as you bought it).

    Build it only if you LIKE the creative process of building, it is not cheaper than buying. or if you require something so special there is nothing even close to what you want available, AND you have the time and budget to build it, AND you like building boats. I have built a number of small boats, I do not justify it as being cheaper because my time is valuble, but I enjoy it and consider it a pleasant spare time activity.

    Even traveling a long distance to find what you want at a reasonable used price is far cheaper than building (and you get a cross country excursion out of it too). I have even flown to a distant location, buy what I needed as far as tow vehicle there, drove it home and than sold off the vehicle I did not need after getting it home. It was cheaper and faster than driving both ways, and I made a small profit selling the vehicle (helped pay for the trip).

    Good luck
     
  12. kerosene
    Joined: Jul 2006
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    kerosene Senior Member

    Parkland, pontoon boats don't really even exist here. And yes a used boat could be bought. Building (and even designing own) is major part of the purpose.

    Samsam - that is interesting but even that is more of a boat than I am after.

    Williamson - that is gorgeous but like above more than what iam looking for.

    Petros - yes I am aware that the decision is not rationla and I am cool with it. Building and tweaking is the fun part. I will have limited time in summers to use the boat anyway but Designing own for my specific needs would be nice.
     
  13. SamSam
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    SamSam Senior Member

  14. tom kane
    Joined: Nov 2003
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    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Lower powerday boat-protected waters

    In the 1950`s I wanted a boat for the purposes you outline and I was influenced by a Popular Mechanic`s article on how to build "lily Pad" a 16 foot flat bottom punt style with all usable space. I modified the design to have a 6 inch deadrise instead of a flat bottom and built it with a triple keelson with no external keel except a metal trailer runner. It floated in 4 inches of water and could go anywhere and was very robust. It was great for camping ashore or drawn up on the beach. We had lots of fun for many years. It was not beautiful but a great sea and camping boat and stable. Beauty brings a lot of un-wanted problems.
     

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  15. BobE
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    BobE Junior Member

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