Design Issues for small, sail/human powered cruising boats

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

  1. scotdomergue
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    scotdomergue Scot

    I’ve been thinking about different approaches and thought I’d share my thoughts on design issues. I’ll be happy to get feedback and other ideas. This was initially written thinking about boats of 16 to 18 feet, but most is applicable outside that range.

    My Marsh Duck is an 18 foot long, 42 inch beam mono-hull with small aft cabin and 107 sqft fully battened sail. She weighs about 130 lbs (boat only), around 185 with all sailing and rowing gear (sliding seat) and small solar power system for electronics; stitch & glue construction, plans available from Duckworks Magazine on-line. I spent 3 months cruising the Sailish Sea on her last summer.

    Boat design involves compromise between different priorities, never more so than with small, un-ballasted sail/human-power cruising boats.

    I can’t see any way to successfully combine a fixed cabin of adequate length for sleeping comfortably with sliding-seat rowing in a boat noticeably under 18 feet. The cabin pushes the rowing position too far toward the other end for good weight balance. So a shorter boat (for example, 16 feet) has sleeping in the central cockpit area under a tent that’s put up each night (or under the stars when the weather is good) and/or uses paddle for human propulsion.

    While sliding-seat rowing with sleeping in the cockpit can certainly be done, I don’t think it really makes sense. At 16 feet and under the boat can be very light and efficiently moved with a kayak paddle, adding sliding-seat rowing adds a lot of complication and noticeable weight. And I’ve found that trying to add a little sliding-seat rowing power when sailing in light winds doesn’t work, while I think it can work quite well with a paddle.

    If using a paddle (double bladed kayak paddle is best in my opinion, though again, other options can be viable), the boat needs to be pretty narrow - for my style of paddling I prefer no more than 24 or 25 inches, AND there are double kayaks at 30 inches and some use kayak paddles with sailing canoes that are even wider (Hugh Horton’s Bufflehead is 33 inches).

    For un-ballasted mono-hulls, the narrower the boat, the less stable it will be. A very narrow mono will be quite challenging to sail in strong winds and rough conditions, though also potentially very fast if you can get your butt up on the side and body out over the water AND keep her upright. And a narrower hull moves through the water more easily in displacement mode - always those compromises and choices between priorities – unless we add amas and make it a tri, which involves other compromises (more on that below).

    Cabin size is also limited in a smaller boat, though I’ve been playing with expanding the width above waterline and aft of paddling position to get more cabin space without compromising paddling performance. Again, tri provides additional options.

    I’m now designing small tri’s that have aft cabins, with amas that can be moved out for sailing stability and in for righting, transport, and when situations call for a narrower boat (and also for rowing at 18 feet and longer with oarlocks mounted on the amas brought in for ideal spread),. The 16 foot versions keep the amas out far enough to not interfere with paddling in human power mode. Of course tri’s weigh more, and they involve more windage, so are not good for human power against much wind. For me, that’s not much of an issue as I’ll be sailing if there’s much wind, though in some conditions . . . another compromise.

    Tri’s also have different sailing characteristics – faster than mono’s in most conditions, but usually not as good in other conditions, particularly beating against the wind. Generally tri’s are more difficult to bring about. The extra sail allowed by greater stability generally more than compensates for the extra windage. The stability combined with power compensating for windage also allows for a larger cabin above waterline. A cabin sleeping platform above waterline can provide lots of storage space in the cabin (below the platform) and a relatively large, comfortable space inside – at the cost of additional windage and weight. Always those compromises. My current 18 foot tri concept has a cabin minimally adequate for 2.

    Personally I tend toward a fairly small cabin space that is quite low. If the weather’s good I’ll leave the hatch open so that I can see the stars and sit up whenever I want, and if the weather is wet, I’ll probably put up a cockpit tent anyway, so will still leave the hatch open. The cabin allows me to have bed ready whenever I am, in a space sealed with watertight hatches (I’ve been designing much better hatches than on my original Marsh Duck) so that I don’t need to put everything in dry bags and pull things out and set up camp, whether on shore or in the boat at anchor. But cabin size, like most everything, is a matter of personal preference and the compromises one is willing to make – personal priorities. These cabin choices are relevant for both mono and tri approaches.

    My current inclinations are toward a very light 15’9” mono for solo, and a 17’9” tri with sliding-seat rowing for 2 (though it will also work well as a solo boat, just a lot heavier and more complex than the 16’ mono). The longer boat will also paddle OK, though that's not as powerful as sliding-seat rowing for maximum human powered speed in this size boat.
     
  2. Skyak
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    Skyak Senior Member

    Hi Scot,
    glad you are sticking around and starting a thread on a subject near and dear to me, wind and human powered cruising. My own direction is toward ultra light weight with high performance camp gear.

    About hull length, once you have decided how much stuff you will carry hull length is pretty much a function of the continuous thrust you can generate. For my ultralight direction reconfiguration of the cockpit for various functions is a given. My direction has been double blade paddle for light weight and control but rowing has better mussel use. I just don't like facing backward when I am boating and the size and weight of oars and a slide don't fit well. I am looking for ways to use my legs for propulsion -peddle props are pretty impressive.

    About sailing performance, my philosophy is that if the wind isn't strong enough to impair your paddling or other muscle based propulsion it's not enough wind to sail in. This sounds either obvious or pompous but it is an important distinction. Most small sailboats don't have a good plan for when the wind dies and are strongly influenced by sail racing. In racing all propulsion must be by wind and a win in zephyrs counts the same as a win in a gale. Cruising or adventure racing don't care how you propel the boat, but you must get to your destination no mater what the weather. There are advantages to only sailing in significant wind, mostly that you don't have to manage excessive sail extending high in the sky with the righting moment it requires. Trimarans are nice and would be a nice place to mount oarlocks. Do some design and then do a check - how much of the size and weight is required to carry the extra size and weight?

    About adding two man capacity, I concluded that there are too many sacrifices and that the best plan for me is two optimized 1 man boats that can be configured as a catamaran for sailing and camping at the destination.
     
  3. P Flados
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    P Flados Senior Member

    I just recently was looking at your Marsh Duck and was wondering if you were going to move on to "refine" your concepts.

    I have be working on a project that has some overlap with yours. It is small proa multihull that was intended to be a "test platform" for foiling and or rigid wing stuff I would like to try. I have learned quite a bit from both building the boat and some initial sailing activities (including a nice little low wind sail yesterday when it got 68 °F on a Sunday in January :)).

    A narrow main hull tri using oarlocks on the amas sounds neat, but making it all work like you want it sounds like a challenge.

    I have done some building with using inexpensive carbon tow on the top and bottom surfaces of a hollow wood box for my cross beams. I found that I can get super bending strength, low weight and small size, all at a very real reasonable cost. The build is somewhat tedious, but again we make our choices and then deal with the results.

    Better cross beams can really help a small multihull. Combine longer but smaller beams with small, light and low freeboard ama's and you can get your stability at a lower performance compromise.

    I am actually a bigger fan of a single ama (think outrigger canoe) than the tri configuration. As I recall, this configuration is popular with the guru's of performance pedal powered boats. You can go over and look at the "Pedal Powered Boat" thread for more info. Note that it is one of the longest active BDN threads and has tons of great stuff.

    Although a single ama would not do the nifty oarlock mount thing, you could probably configure a rowable boat with crossbeams far enough forward and aft for clearance and the ama far enough away from the main hull for clearance. From a few inches above the waterline down your main hull can stay very skinny for low drag, and then from this point up, your "cabin" / seating arrangements can extend over toward the ama side for good balance.
     
  4. Petros
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    Petros Senior Member

    Hi Scott,

    I like your thoughts on this topic, and I wanted to share my experience that may add to the discussion. A friend of mine and I enter a boat building contest every year for the last 5 years or so on Lake Union in Seattle at the Center for Wooden Boats. It has a complicated formula for a win, with points in each category for cost of materials, time to build, weight of tools used (more tools the more you are penalized), innovation, originality, quality, etc. plus the results in the race. two person teams have 24 hours to build on-site their entry, and than race it around the lake usually on 4th of July as part of a Independence Day boat show. The idea is to show that it does not take a lot of cost nor tools, nor time to build a good performing boat.

    What is relevant here however is the race, one leg is required to be sail powered, and one leg muscle powered, with the third leg as "free style" (either or both). Most people use paddles, either single or doubled ended mostly because the cost, time to build and complexity of any other system (though both rowing and pedal powered have been built for the contest by some contestant, in addition to using paddles).

    To put in a good showing in the race using paddles, the hull has to be narrow to paddle well. and of course to sail well the hull needs to be wide. What usually wins the race is a boat that paddles well since two out of the three legs usually use muscle power. Every configuration of hull has been used, from pram dingy, kayak hull, catamaran, trimaran, dory, etc. We have also entered both kayak/canoe type hulls and trimarans (catamarans do not work well because they can not be paddled efficiently, they always lose the race badly).

    After trying out several different types of hulls we have found the trimaran is always a reliable winner. We configure it with a vary narrow main hull, about 18" wide, with a single set of small outriggers at the mid point. the very stream lined amas are only about 3 ft long and about 1 ft deep set about 4 ft out from the center line of the hull with a single beam supporting it. We have found that this makes for a very stable configuration that allows us to apply our full muscle power to paddling without having to concern with balance (this was never true with the monhulls, even one that had a 38" wide beam, we still had to maintain good balance and stay low in the hull, and it was difficult to paddle fast because of the gunwale width). The crew on our trimaran is separated as far forward and aft as the hull shape allowed so the cross beam would not interfere with our strokes, that left a large center hull section that would be available for a cabin or cargo if this was a multi day race. And of course with the sail deployed it was also a very relaxed configuration, we did not even have to put our weight off center because of the low amount of heel with this configuration.

    the configuration works well for the race because it gives both a narrow hull and a stable sailing platform. And unlike the monohull configurations, we built it as a sit-on-top configuration since our CG height is not so critical for stability, this too allows us better paddle angle as compared to a conventional canoe or kayak with your butt low and below the water line. And the stability also assisted in getting maximum benefit from paddling because we felt stable and comfortable when we were paddling so we could put maximum effort into going forward, and even under sail we could continue to paddle on the "free style" leg without fear of capsizing.

    What works against us on this contest is that we have more hulls to build, so it takes longer to build having to make the amas. And the way the point scoring works, often the 2nd or even 3rd place finisher in the race ends up the contest winner because the race is only about 20 percent of the total score. we have won the race with this configuration several times, and came in second in total points several times (alas, first place finish and overall points winner has been elusive, so we have to find a way to significantly reduce out build time).

    What we find works best for the race however is a narrow thin hull about 18 ft long with two small amas with a single beam. Max overall width is about 10 ft. With a single beam and the small amas it is very fast to disassemble and stow the amas and beam when we put the hull on the roof of the car. With a sit-on-top configuration, it leaves the whole volume of the center hull for cargo or cabin space if it was to be used on multiday trips.

    However, this configuration does not behave well with a solo crew because the rear cockpit is too far aft, so either ballast would have to be added up front, or the solo crew would have to move forward, putting the beam and sailing rig in the way for good paddling. and it is kind of awkward for just solo sailing too, you have to avoid the sail coming about when you tack, which is not a problem when all the way back in the aft cockpit. Though if you were building one for either solo or two crews, you could build in three seats, but that might restrict the height of any cabin to the gunwale height were the center seat was located.

    I think this configuration would work well for a mini cruiser, it would also be possible to install nets between the hull and the amas to give you room to stretch out.
     
  5. peterAustralia
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    peterAustralia Senior Member

    if i have you right, are you saying that Marsh Duck has not worked out quite as well as it was hoped?

    If I was to turn back the clock 100 years, and someone wanted a small row/sail cruiser with accommodation, they may well go for a 15ft skiff, maybe a sprit sail as the rig. For accommodation, the center part of the boat is covered with canvas (maybe using hoops to give rain shedding and more space). When sailing, the 'accommodation' is packed away.

    At 15ft windage is less than a larger boat. I know that I found rowing my 18ft rowboat very hard work in any real breeze, so I downsized to 13.5ft, the smaller boat can still be rowed well in moderate breezes. No way would I go back to the larger boat. My boat (the smaller one) is hard single chine with flared sides and 4ft beam, for sailing I guess a few inches extra beam and multichine would suit better. I have plans for bateau.com Otter 16, the sort of boat that could do both (just as one example, there are others out there too). I should have built the Otter 16 instead of the 18ft dory (my stuff up)

    http://www.bateau.com/studyplans/OT16_study.htm?prod=OT16

    one of the thwarts would need to be removable,,, and replaced with a ring frame, but it could be done
     
  6. Skyak
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    Skyak Senior Member

    Petro, can you post a link or text of the rules? Was the latest boat yellow and disposable? I have a picture in my head but I am not sure.

    My thoughts are that the dimensions you list are more strongly influenced by the rules of the competition which are more concerned with entertainment than what you would build to own. Specifically more time to build with more tools optimized for longer time on the water. 18ft is the length corresponding more closely to a single paddler than two. I have a CLC PAX 20 that is very close to those main hull dimensions (the site says 19" beam but mine is 17.5" or less at the waterline). The V hull has barely tolerable stability if you sit directly against the hull bottom. Load carrying capability is less than I would want for one and the the hull is too narrow to fit the shoulders of someone strong enough to paddle at the speed it is designed for. With a little wider main hull I think that would make a good light cruiser for one OR day boat for two.

    I think the small outrigger idea is worth detailed consideration particularly with oars because they need the wide oarlocks and the stability for efficient operation. I also want to do some calculation of storing water in the amas and having a simple means of shifting this weight from side to side. The case against short amas is that they add major wave drag every time they touch and they don't add useful weight or volume capacity for their own added weight and volume. I think for sailing I would propose a wing setup with feet in the main hull and a low drag float at the outside edge large enough to keep the hiked sailor dry when the wind dies.

    In the posts so far I think there is a wide disparity in capacity and accommodation. "Cruising" can be construed to mean a boat that would be comfortable to stay aboard for a day in port in the case of bad weather on the beach or at anchor -not just toss a tent in the canoe. Can we consider this part of the SOR? I also think we should agree on the weight of supplies to be carried. My thought is that 70 lbs is a good nominal for one individual. This includes drinking water reserve but not shelter which is part of the boat weight.
     
  7. scotdomergue
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    scotdomergue Scot

    I posted and then tried to edit, and it disappeared, so try again . . .

    Great to see all the interest and ideas! I'll come back and share more when I have time, but wanted to clarify one thing immediately:

    I'm VERY HAPPY with the Marsh Duck. I cruised the Salish Sea on her for 3 months last summer. I had a wonderful time. She performed better than I'd ever imagined or had any reason to hope for.

    And:
    - I enjoy the design process
    - boats are always a compromise, so infinite opportunity to develop new designs to address somewhat different sets of priorities
    - I'm in on-going communication with several people who have different priorities than mine and different ideas about how to satisfy them - great stimulus to thought and new designs
    - While I'm very happy with the Duck, she's not perfect in all ways for all things. I'm always interested in lighter weight, and the Duck's much better for one person than for 2. Those are a couple of the things that keep me thinking about new designs/
     
  8. Petros
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    Petros Senior Member

    ideal micro cruiser: can be folded down to fit in the trunk of a car, light enough to be carried under one arm, large enough to carry a weeks worth of gear and supplies, roomy enough to have a cabin you can stretch out in laying down, and sit up full height without hitting your head, and for a small galley area and private head. and enough room on deck to also stretch out on and stay dry. Oh, and durable enough to withstand open water sailing. Anything else?

    From there we have to prioritize and compromise each feature to make it realistic.
     
  9. scotdomergue
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    scotdomergue Scot

    What about fast and fun to sail in all conditions and excellent human powered performance?
     
  10. Petros
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    Petros Senior Member

    of course, that too! it is a sailboat, if it is not powered at least let it be fun to sail and row/paddle! Fast to sail gets you places faster but kind of hard to do in a 16 to 18 ft overall length (foils anyone?).

    As you know Scot, I favor the double ended kayak paddle for simplicity and light weight.
     
  11. Skyak
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    Skyak Senior Member

    I like the way you are thinking!

    The only exceptions I would make to that list are full sitting headroom would only be in the 'camp mode' at anchor, sea anchor, or beached. Sitting headroom inside would result in undesirable windage underway. I will just say it from the start, sitting upright protected underway and the private head are the job of a custom poncho on all my designs. I have no interest in occupying a small space with my own waste.

    And I don't see any value to sitting on deck. I would prefer to be able to roll the deck back to have an expanded safe dry cockpit. The purpose of deck is to shed water quickly to maintain buoyancy and stability. The measure of a good deck is the size of the wave you can stuff it through without incident. Correctly designed it would tend to be wet, slippery and shed any occupant. There is a related concern -stability and access to functions. Example; if you need to go to the bow to set or furl the jib but can not do it without returning to land or swimming -that's bad.

    I like the idea of fitting under ones arm and light weight but I would leave weight as a variable to measure against desirability. Packed size and portability limits are something I consider in grades -trailer-able, car top, inside SUV, inside apartment (standard shipping) airport or bus luggage are all pretty close, car trunk is yet a little smaller, and 'carry-on' is the toughest size limit I aspire to.

    There are so many trailerables I don't even consider designing another. I occasionally consider a trailerable fleet of microcruisers that a guide could haul or a micro-yacht club could take on regattas across the country. The only trailerable I would like is one that carries the trailer and the bike that pulls it along sailing (marsh duck II?). I already have plenty of car top-able cruisers -no more room in the garage. Inside SUV is the first interesting portability point for me -but not for anyone without an SUV. A boat that fits in your car, in your closet, in cheap UPS shipping, on the plane with you... this is a boat that will be with you enabling the best times of your life.
     
  12. P Flados
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    P Flados Senior Member

    After reading Skyak & Petros, I see some hope of a "focus on priorities" effort that may help guide you.

    If you really want rowing vs paddling, this probably need to be a priority up front. The 18" wide sit on top main hull still sounds about right. Consider a single cross beam just aft of the slightly forward of center main seat and small amas spaced out just right to be optimum for rowing.

    Build in the sailing features, but do so with minimal adverse impact on the rowing and make sailing as KISS (keep it simple ...) as you can. Consider two simple smaller sails. This lets you balance the boat without worry about board/rudder setup and the conversion to/from modes (muscle vs. wind) of two small sails on the water should be much easier.

    The second seat would probably be aft of the rower for a 2 seater (face to face seating) with the intent of stowing gear up forward in 2 man mode and stowing gear more even split for single handed work.

    If you are willing to paddle, the Petros experience from the Lake Union races becomes more directly applicable. Given the variety of what has been tried, I would try to not stray too far from the described layout.
     
  13. philSweet
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    philSweet Senior Member

    Frankly, I don't find HPV's and sail mix very well. A tiny auxiliary sail is fine. 1 SM per person or so. Handy downwind and maybe able to reduce the windage on a breezy day, but not exactly spirited sailing. I've sailed canoes using umbrellas and tent flys all over the Florida bay. You need a really good umbrella anyway.

    The problem with sailing properly is you end up in a much higher power range than what a HPV is designed for. Little, light sailboats are wide. Wide doesn't paddle well. And there isn't really a good middle ground in the 200 - 600 pound all up range.

    For paddle craft, I go with a 17' solo or 21' tandem canoe. I sail it with the biggest, baddest umbrella I can find. I'd normally have 300+ pounds of kit per person for a saltwater trip of two weeks. At around 1500 pounds total or more, a little kicker is worth bringing along. Can run for a week on 6 gallons at hull speed.

    For sailing, two can camp cruise on 16' just fine. A kicker is mandatory, though. No ifs, ands, or buts about it. Can be stripped down to a weight that can be dragged up a beach by two.

    Once you get into bigger boats, it is easier to mix sail and oar. A six person, four oar boat, or a 28', 16 person war canoe can be sailed along just fine. They come with the beam to hold some sail. They carry more human power than they can put to use, so you can transition to sail under a wider range of conditions.

    One note. I think water ballast can be put to good use if a serious, if somewhat complicated, one or two handed voyager is desired. The water ballast can let the boat carry some sail. But ultra light weight and simplicity isn't part of it. I have a sketch of an Florida Challenge boat that relies on about 400# of water ballast to sail, and can be dumped or shifted when tacking. It can be pole assisted, or stand paddle assisted under sail. It is intended for ultra endurance and very low average human power. The FC has a 40 mile portage, so weight is a concern.
     

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  14. scotdomergue
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    scotdomergue Scot

    For now, just a quick note to follow-up on a couple of things.

    No need for "Marsh Duck II". I often tow her with my Bike Friday Pocket Llama, which fits in the forward storage compartment along with the trailer parts. Usually taking the bike along is excess weight, and it gets in the way of easy access to other things, so I don't do it that often, but it's easy enough when I want. The main part of the trailer (2 wheels, axle, cradle) that straps on a little aft of center I always carry along as it also works as a 2-wheel dolly. The forward part of the trailer which straps securely to the front of the boat and hitches onto the bike (compressed air fittings) I leave at home unless I'm taking the bike too. Key trailer parts are available from www.bikerev.com as well as the hitches that fit onto the bike. If you go there, let Ian know I referred you.

    Water ballast can make sense, and I stow the gallon jugs of fresh water I carry as low in the boat as possible, as well as tools, canned food and all the heaviest stuff. But I'm much more interested in light weight and general simplicity and feel no need to build in a dedicated tank, pumps and such for water ballast. That's what crew is for. The Marsh Duck is designed to sail like a racing dinghy, with one's butt out at the edge of the side-deck wings, and body hiked out over the water. It's a fun, fast sail. Works better than water ballast in a small, light boat as long as you're up for the very active style of sailing.
     
    Last edited: Jan 8, 2014

  15. scotdomergue
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    scotdomergue Scot

    Following up further: I've often heard this idea that sail and human power aren't compatible. I quite thoroughly don't agree. The Marsh Duck combines the two quite nicely - fast, fun sailing (107 square feet of full battened sail) and quite nice sliding-seat rowing. I find I can maintain 4 knots rowing quite comfortably. And she's a full-on cruiser, not a camp cruiser. I slept in her cabin all but 2 nights during my 3-month summer cruise, usually at anchor and occasionally pulled up on a beach (usually when I wanted to work on her which is much easier when you can walk all around her).

    I'm currently playing with much smaller designs using kayak paddle for human power. Really fast sailing, and stronger winds/rougher conditions will be more challenging, but I know from past experience that decent all round sailing is possible in a narrow boat - beating against the wind and broad reach as well as downwind.
     
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