Design Issues for small, sail/human powered cruising boats

Discussion in 'Boat Design' started by scotdomergue, Jan 6, 2014.

  1. scotdomergue
    Joined: Jan 2009
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    Location: Twisp, WA USA

    scotdomergue Scot

    I continue to think about, pay attention to, and design small sail/human power cruising boats. I've learned a lot and changed some over the last 5 years. I have much greater (though still limited) experience with tri's, and have paid a lot of attention to the smaller boats competing in the R2AK and Water Tribe events and showing up on the web. I continue to find sliding-seat rowing my preferred mode of human power, at least partly due to back problems that make significant periods of both fixed-seat rowing and paddling problematic. At age 72 I find that comfort and stability are a little higher priority - and I continue to be a minimalist and be comfortable with far less stuff and space than most! I also find myself returning to an interest in boats that could, potentially at least, take me almost anywhere, even across oceans.

    I'm currently refining a design at 15.75 feet with 4-foot beam, using Divinycell panel cores and fiberglass/carbon/epoxy skins. I expect I'll build it this summer. Basic boat weight should be 55-70 lbs, perhaps 100 with all sailing and rowing gear and small solar power system for electronics.

    I'll be very interested in any further thoughts on this general subject. Have any of you changed your thinking these past years? Any new ideas? Any new folks interested?
  2. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    Didn't you build a better boat for R2AK?
    As I recall it broke just before the race.
    Was it too light, in the wrong place, and broke?
  3. scotdomergue
    Joined: Jan 2009
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    Location: Twisp, WA USA

    scotdomergue Scot

    Yes, I designed and built Sealark, a 19-foot tri with akas that pivoted to bring the amas inward for rowing. The design and build were rather rushed, trying to be ready for the R2AK. Yes, the vaka-side end pivot points of two of the akas broke. Toward the end of the build I'd had misgiving about these, but in the rush didn't address it. Otherwise the boat worked out fairly well as far as it went.

    From the experience I concluded:

    Tri's are complicated and heavy compared to unballasted mono's of comparable space (not new information, but of greater importance to me after the experience).

    Moving the amas in for rowing wasn't worthwhile. The boat performed well in very light wind and it was easy to move by paddle at 2 knots while fully rigged for sailing, getting up to 3 or 4 knots with just a little help from the sails in a breath of wind. It took significant time and effort to switch between rowing and sailing modes. The swivel akas added complexity and had other disadvantages.

    I need a little wider sleeping platform than the bottom of that vaka hull for long term cruising.

    If I'd fixed her (almost certainly changing to fixed location akas, removable for transport), she still would not have been a boat I wanted. She wouldn't be suitable for long-term, live-aboard cruising and would be too big, heavy and complicated for a boat that wasn't.

    She could have been fairly easily fixed, but I was really burned out from the rushed build and was ready to move on. It would have taken too much time and energy to do the work and then to test her to the point where I'd feel good about selling her at an adequate price. I probably could have modified her to be more suitable for long-term cruising, but I wasn't up for it. Instead I offered her for sale "as is", and , when she didn't sell quickly, sold parts (mast, sails, etc. and later the hulls).

    I enjoy designing and using boats, but am much less enamored of building them. I build because it's how I can afford to create/have the boat I want. If I could find and buy what I want at a price I can afford, or afford to have someone build what I want, I'd be happy to do so. I bought an old San Juan 21 a couple of years ago and enjoyed a few months cruising on her, but, again, she wasn't the boat I want long-term.

    Most of my cruising is likely to be solo. A boat that's what I want solo, and is adequate to occasionally have another person along on shorter, less demanding trips makes sense.

    Sealark was a valuable learning experience, and fun during the couple of weeks of sea trials before she broke.

    I've continued to design some small cruising tri's, but have decided that, for me, currently, the very light, small, 16-foot mono makes more sense.
  4. Squidly-Diddly
    Joined: Sep 2007
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    Location: SF bay

    Squidly-Diddly Senior Member

    "My Marsh Duck is an 18 foot long, 42 inch beam mono-hull with small aft cabin and 107 sqft fully battened sail."

    how about some pics?
  5. scotdomergue
    Joined: Jan 2009
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    Location: Twisp, WA USA

    scotdomergue Scot

    anchored, watmough bay.jpg sailing.jpg

    Attached Files:

  6. Clarkey
    Joined: Aug 2010
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    Location: UK

    Clarkey Senior Member

    This is a topic which really interests me, thanks for all the insight and ideas.

    I have been playing around with a few thoughts for a while now. What I keep coming back to is a small (approx. 13' x 4-5') rowing catamaran that basically just provides a platform for camping on the water. Other ideas creeping in are:

    • A small rig designed to assist rowing upwind, rather than down.
    • Ability to row from sitting or standing position
    • Rig(s) would also be easily reconfigured to provide some shelter both under way and at anchor.
    • Use of a rollable swag tent for accommodation.
    After a few years of career and relocation hell I am now making first cuts in a pile of plywood and hope to be on the water in the spring.
  7. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    BlueBell likes this.
  8. Tiny Turnip
    Joined: Mar 2008
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    Location: Huddersfield, UK

    Tiny Turnip Senior Member

    Here is the assembly and launch of the slightly smaller and definitely simpler re-design of the Solway Dory Osprey, similar to my trimaran earlier in the thread. Lots of neat details, particularly the beam and ama connections, that make the assembly and rigging very quick and easy.

    A few further thoughts relating to my tri.

    The handling on land is very important to me. I would like an easy way of getting the trolley under the hull when landing (while still afloat) and into the boat when setting off. I'm working on an idea for this.

    Most of my sailing, certainly expedition sailing, is with two people, which makes paddling, and lifting and carrying the boat on the shore so much more viable.

    I am continuously attracted by the idea of sleeping on board, and am thinking of a boom tent that goes out to the amas, with tramp/hammock stretched between the beams on each side, for sleeping and sitting with feet in the hull. However, the realities of sleeping in a small boat at anchor, and the associated anchor dragging anxieties and movement in chop, mean I have so far come back to beaching the boat and sleeping in a tent.

    Here's some pictures of camp cruising in my SD trimaran:

    Snufkin round about Mull
    kerosene likes this.
  9. Zilver
    Joined: Nov 2007
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    Location: Amterdam the Netherlands

    Zilver Junior Member

    Hello TT, I use a dome tent on my little trimaran the way you describe. Because of the foot(and sleep)well the headroom in the tent is very genereous. Also I can store all my stuff on the trampolines, but underneath the outer tent.
    I always try to get a sheltered place, else the light boat is much to rocky and noisy for sleeping/resting.

    Greetings, Hans

    bajansailor likes this.
  10. scotdomergue
    Joined: Jan 2009
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    scotdomergue Scot

    I continue thinking about and designing boats of this nature. I'm currently focused on designing a boat capable of crossing oceans, while still fun for coastal and island cruising. Current designs are 19 feet 10 inches long and 36 to 44 inches beam, the boats weigh less than 100 lbs, and under 150 lbs with all sailing and rowing gear. Lightly loaded I should be able to row at 3.5 to 4 knots for extended periods of time (narrower boats, higher speeds). Gross displacement loaded for ocean crossing should be under 1000 lbs., possibly as little as 600 or 700 lbs.

    I am very interested in any examples of boats of this sort. Any suggestions?
  11. peterAustralia
    Joined: Mar 2006
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    Location: Melbourne Australia

    peterAustralia Senior Member

    sounds like a rowing boat.

    44 inches is a little narrow,, maybe 50 inches

    some wonderful person (me) made a list of over 500 rowing boat designs... 33 inches is a canoe, and not what u want.
  12. Andrew Kirk
    Joined: Jul 2021
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    Location: Chorley UK

    Andrew Kirk Pedal boater.

    Having built a successful sternwheel, pedal powered dinghy I'm now looking to combine human and sail power in a new boat. (This forum should carry the health warning: BOAT BUILDING CAN BE ADICTIVE!) It will be a light weight catamaran with mainsail, jib and 2 paddlewheels between the hulls. I don't intend to sleep onboard but this is a great thread for some inspiration and to know I'm not alone.
    Last edited: Dec 24, 2021
  13. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member

    I am presently building an experimental boat of my own design. It is a straight-sided scow with a 3 ft beam.

    It will be powered by a 42 sf sail and what I call a "short sweep".

    The short sweep is really a glorified canoe paddle with a fulcrum. It works by inclining the boat toward the side it is to be propelled from, and by using the rudder to counter act the turning moment.

    This particular boat is only 10 ft long, so is not intended for long voyages. It is intended for small-lake fishing.

    But the concept of the short sweep might be interesting for other applications.

    For example, I can imagine it being used on a single-outrigger, with it being deployed on the outrigger side of the boat.

    I got this idea while trying to paddle the SuperSnark, I once owned, around.

    It didn't paddle at all, with a single paddle, without the dagger-board being down along with the rudder.

    But, with both appendages down, I needed a free hand to steer it. So I devised a paddle that I could use with just one hand. My hand gripped it lower down, and I braced the handle against my fore arm.

    It was somewhat uncomfortable, but it worked. And the paddle took up minimal space. It was quick and easy to deploy whenever needed.

    I quickly imagined how nice it would be, if I didn't need to grip it near the bottom and brace the handle against my fore arm.

    But there was really no practical way to add an oarlock to a boat made of plastic-coated foam that I could think of. So, I decided that, if I ever built a boat of my own design, I would try this idea.
  14. scotdomergue
    Joined: Jan 2009
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    Location: Twisp, WA USA

    scotdomergue Scot

    Good to see there remains interest. Yesterday I did basic design for a 66-inch beam. It needs higher topsides to have potential to self-right, is heavier, a half knot slower rowing, would need more sail, etc. I think I'll stay focused on 40 to 44 inches beam.

  15. scotdomergue
    Joined: Jan 2009
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    Location: Twisp, WA USA

    scotdomergue Scot

    I've settled on a 19'10"x44" forward cabin design for serious solo cruising, capable of crossing oceans, probably self-righting if rig is stowed below and loads are properly stowed and secured. Construction is stitch & glue using panels with Divinycell cores and fiberglass/epoxy (bottom & bilges for abrasion resistance) or carbon fiber/epoxy skins.

    Attached Files:

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