Why a sailing dinghy's hull is so much heavier than a windsurf board?

Discussion in 'Sailboats' started by xarax, May 4, 2009.

  1. xarax

    xarax Previous Member

    Newer longboards, ( like Warp X 380, Phantom 380, Mistral Equippe 3 , Kona One, Longrider ) weight less than 15 kgms, a lot less than the hulls of even the lighter single handed dinghies. Why is this so ? A windsurf board fitted with an unstayed cat rig would be an interesting hybrid water craft. A truly car-top transportable dinghy hull could be very convenient to the weekend young sailors. How this failed to be noticed by the board manufacturers that offer similar hulls products ( SUP boards, sit-on-top kayaks, etc.)? A hull like this could have detachable trapezes for additional stiffness and balance.
     
  2. BWD
    Joined: Aug 2006
    Posts: 229
    Likes: 11, Points: 0, Legacy Rep: 128
    Location: Virginia, US

    BWD Senior Member

    Dinghies weigh more because they are bigger, no?
    -more hull surface area, more parts, reinforcements >>more weight.
    People have made equipes and similar windsurf boards into dinghies, with some kind of rack or trapeze to hike out on. Trouble is, these end up weighing more also, and they are always falling over. But it has been done.

    Did you ever hear of the HOOT?
    It was/is a boat under development in the San Francisco area. HOOT is 14 feet, pretty narrow hull body with hiking wings.
    They had a picture on the web of a girl carrying the hull under her arm, claimed hull weight was 50lbs, all the parts together 140lbs.
    You can see the picture at
    http://www.gohoot.com/prod_info.html
    I think it is not coming to market though; the builder's production facility is fully committed to other projects.

    One could build a similar hull, it would be tippy.
    Or, the "open bic" is pretty good for kids up to 65kg or so and weighs 45kg.

    It would be interesting to take a formula width sailboard and stretch it a few feet, I guess....
     
  3. xarax

    xarax Previous Member

    Thank you BWD,
    Dinghies are bigger, true, but usually not longer than the longboards cited. So the should n t weight three times their weight, should they ?
    This HOOT dinghy is very near what I had in mind...May be it should be produced by a windsurf boards - and not by a sailing boats - manufacturer, to appeal to a wider market... Much of the success of the windsurfs has to do with the lightness and simplicity of the boats, as much of the not-so-much success of the dinghies has to do with the opposite !
     
  4. CT 249
    Joined: Dec 2004
    Posts: 1,701
    Likes: 78, Points: 48, Legacy Rep: 467
    Location: Sydney Australia

    CT 249 Senior Member

    As BWD says, two basic problems are (1) volume and (2) the simple fact that a dinghy has more gear and all that weight adds up.

    The only high-performance dinghy of similar dimensions is the International Moth, which has an 11' x 1' hull. The bare Moth hull can come out of the mould at around 6-8kg but by the time you add a rudder, wings, mainsheet, stays, wing netting etc the sailing weight climbs to to about 26kg, which is similar to a rigged Raceboard. And the foiler Moth is a much more high-tech and expensive and (in many ways) more advanced design that can often beat a Formula board and would almost always beat a Raceboard.

    Another thing is that boats are just tougher than a Raceboard. Maybe that's because they are not foam filled, so a leak is a much bigger problem. But our club's raceboards are constantly being damaged, whereas the dinghies of similar age are still in very good condition.

    The biggest problem may be that a dinghy needs to be more stable than a board if it is going to be sailed by the typical sailor. That means more width and weight. The only boat with an average beam similar to that of a board was a "fat skiff" Moth, and they were extremely difficult to sail. Even more modern rigs won't make them into something that most people can sail.

    The International Canoe is 3' wide and 17' long, but it's harder to sail than a Raceboard or Lechner/D2, because sailing a boat is more complicated; therefore you need more stability to keep it all upright.

    The problems with skinny boats are not just in straight-line sailing, but in getting through fluky winds, on and off the beach, etc. If the boat is so skinny that it falls over even in a light breeze when stationary, how do you get your trolley back ashore after launching? The answer is - with difficulty!

    Tacking and gybing a skinny boat involves moving from one side of the wing/trap/plank tot he other while changing mainsheet and tiller. This is harder than tacking or gybing a board. And a capsize is more of a problem than dropping the rig, which is the equivalent move on a board. Finally, on a super skinny boat you can't sit around between races, wait for rescue, or (sometimes) even paddle through a small calm patch. The practical difficulties become enormous - last time I saw a Moth race, most of the fleet missed the start because the boats are so tippy they could not paddle 200m through a dead-air zone.

    I'm not sure the windsurfer manufacturers are more successful. In many (most?) countries, there are more probably dinghy sailors than windsurfers. In racing classes, boats like the Laser are far more successful than any board. The boards could learn a lot from boats!
     
  5. xarax

    xarax Previous Member

    Thank you CT 249. Very informative response, as always !
    For a car top transportable dinghy, it is only the bare hull weight that really matters. The main problem during transportation prior or after sailing is this bare hull weight, not the whole sailing gear of the sail-ready boat. I think that a dinghy s hull could be much lighter for this purpose, even if this would necessarily involve some extra, easily attachable and detachable structural elements that would stiffen the whole structure, like aluminium tubes for trapeze wings, mast and daggerboard bases, etc.
    An extremely light hull could not possibly perform at the high-performance end, where high material loads are encountered and great stiffness are needed, but you would agree that this is not the biggest section of the dinghy market, and surely a high performance skinny dinghy is not what the average weekend young (or not-so-young-anymore..) sailor needs or wants. A truly car top transportable boat, with a hull that one person could easily lift and move around, would not necessarily be a skinny boat, but neither it should be three meters wide ! So why it should weight three times a one-meter-wide formula board, for example ?
    The absence of foam from dinghies hull : Very interesting remark indeed ! So why there are not, in the dinghy world, any such hulls ( like in the windsurf boards, the SUP s or the sit-on-tops), i.e.foam filled, one piece monocoque, round shapes ? It seems like the shapes of dinghies are glued to an epoch 50 years ago, while the building materials are rapidly evolving. New, lighter materials always transform vehicle shapes, and this should happen in the dinghy world, too.
    "sailing a boat is more complicated (than sailing a windsurf board); therefore you need more stability to keep it all upright." I don t agree with this statement, if it is literally taken. Sailing a windsurf is at least as complicated, it needs at least the same amount of skills and concentration, especially if we consider the sea and wind conditions the windsurfer usually confronts with. It is the easiness of handling the windsurf sailboat, the direct way of transferring one thoughts into body and boat movements, that facilitate the windsurfer but is almost absent in the dinghy world average sailor. So the ball is on the dinghy world designers .They are who need to make the dinghy easier to sail for the weekend sailor, and easier to upload from the top of his car too !
    P.S. Of course there are A LOT more windsurf boards than dinghies, and that is a sad state of affairs for all of us !
     
  6. ancient kayaker
    Joined: Aug 2006
    Posts: 3,497
    Likes: 146, Points: 0, Legacy Rep: 2291
    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    Boards can be made using foam cores which are available ready made and customised. To use this method for a dinghy it would be necessary to cast the core first, not easy. Even then, for a typical dinghy say 4ft beam and 1ft high the midships circumference is about x3 that of a board. Then add the weight of the mast step and decks ...

    I have plans for a plywood 10 ft x 4.5 ft skiff which I expect to come in at about 60 lb hull weight. It will be build pretty light. About the only way to beat that by a significant amount without hi-tech materials would be to use the skin-on-frame method.
     
  7. bistros

    bistros Previous Member

    Agree with the above responses (pretty much). Doug Kidder (the guy behind the Hoot project) is NOT giving up on the Hoot at all. He's been busy with his main product lines - rowing shells. As you can imagine, with an Olympic year last year his production facilities were jammed with shell business, and the sailing venture took a back seat.

    Although he doesn't keep the web site all that current, Doug posts on Sailing Anarchy as dgkidder and he's updated progress recently.

    MY 14' single hand skiff hull came in at 74 pounds before hardware and paint. All up it weights around 130 pounds ready to sail with aluminum mast (not carbon). This is for a trapeze / asymmetrical spinnaker boat with a cedar stripped hull.

    --
    Bill
     
  8. CT 249
    Joined: Dec 2004
    Posts: 1,701
    Likes: 78, Points: 48, Legacy Rep: 467
    Location: Sydney Australia

    CT 249 Senior Member

    Actually, around many places there are probably more active boats than boards. Certainly that's the case in the USA, UK and Australia.

    We're always told that boards are more developed that boats, but IMHO it's not true. The 1970s Windsurfer One Design was 21kg at 3.66m and 195L; now the Raceboards are about 14kg at 3.85m and 270 L. Considering that the One Design was tough as rock and cheap as chips (currently 1/3 the price of a Raceboard), that doesn't seem to be huge progress.

    When the Windsurfer first came out, it was a bit slower than a Moth. Now, the fastest course racing boards (Formula) are a bit faster than a Moth in a breeze, and much slower than a Moth when not planing. So the development rate of the top course-racing dinghies and top course-racing boards seem to be pretty equal. That's the effect of all those smart engineers working at home - just like Jim Drake did when he created windsurfing!
     
  9. xarax

    xarax Previous Member

    Thanks again CT 249,
    "because of the greater freeboard ( of a dinghy, in comparison with that of a windsurf board )"
    Why should a dinghy has to have a greater freeboard than a windsurf board ? Dinghy sailors can also wear wetsuits as the windsurfers do, cant they ? :)
    "I think you'll find that dinghy materials are vastly more advanced than in boards."
    Of course, but that was exactly my point, was n t it ? Their structural shape is not vastly advanced ! The structure of dinghies has not yet taken full advantage of the available modern building materials. The so called high performance all carbon dinghies seem like something that could have been build in plywood as well, if they should not have cost so much... One often finds dinghy plans that can be executable in carbon or in plywood, but the plans, the structural philosophy and the overall shape of the hull remains the same. Something like building a 1905 Wright airplane in carbon...
    "There's many, many, many more engineers and much more money going into boat engineering than into board engineering. Those $100 million budgets for America's Cup boats or $10 million supermaxi budgets dwarf anything the boards have ever done, and with a lot of people moving back and forth from AC to dinghies, the leading-edge dinghies and skiffs can use all that development. For example, the builder of many of the top Moths and Skiffs (Macca) is a renowned supermaxi and AC boat builder."
    Well, they should try more ! :)
    What might be an interesting idea would be of a board where there is not any forward-backward movement of the mast, only some kind of a somehow controlled, (not fixed), fin. This would also be called a sailing dinghy, would n t it ? I do not see why such a hull should be much heavier than a truly car toppable modern longboard hull.
    P.S. How much time does this fitting of the detachable wings take ? Could it be simpler and faster ? ( if, for example the tubes were made to fit into pockets integrated, or build into, the hull ?
     
  10. bistros

    bistros Previous Member

    Dinghy shapes have evolved significantly. Thinking you could render a Beiker 5 I-14 in plywood is ridiculous. The 90's saw us progress from planing hulls that had to overcome climbing the bow wave to what Frank Bethwaite calls "humpless" planing boats capable of exceeding windspeed around a race course. The combination of light weight, strong stiff hulls and modern hull shapes have made a difference that is easily noticed.

    And Paul Beiker ....

    I can't say I'm a fan or follower of the last decade's AC technology - I'm still stuck on 12 meters.

    You should take a look at Chris Maas' Development Canoe work over the past three years. Spectacular craftsmanship and a world championship as well.

    The work done on Moth foilers in the past three years is worth study as well (putting on my Doug Lord hat here). Light weight, well designed and applied rigs and spectacular speeds that are at or exceeding the top level of dinghy performance in the right conditions (but only the right conditions).

    Object 2 Skiffworks has recently built a carbon B5 I-14 that weighs under 100 pounds fully rigged - it needs 50 pounds of lead to be class legal. Light weight with strength is possible, it just is expensive. The same people built both the world's winning C Class wing sailed catamaran, and a fully foiling C Class catamaran as a challenger. Object 2 owns several world championships in multiple classes of boats. Better have a good checkbook though.

    Board sailing delivers spectacular high performance in regards to overall speed on the right point of sail, but the performance exhibited is one-dimensional compared to modern high performance dinghies/skiffs/foilers where performance has been developed on all points of sail in a wide range of conditions.

    Sounds like you really should talk to Doug Kidder, as the Hoot seems a great fit for your design brief.

    From my perspective a lot of people have put a lot of time, research and money into extracting optimal performance from modern composites and materials - throwing out the rules from frame and stringer construction years ago. Even homebuilders of Cherubs and R-Class skiffs are building foam cored, vacuum bagged carbon/kevlar hulls that are orders of magnitude better than those of ten years ago.

    FWIW, I understand how a board sailor's perspective of dinghies might be somewhat negative, but this is an apples versus oranges comparison.

    --
    Bill
     
  11. xarax

    xarax Previous Member

    Thank you Bistros,
    "The 90's saw us progress from planning hulls that had to overcome climbing the bow wave to what Frank Bethwaite calls "humpless" planing boats capable of exceeding windspeed around a race course."
    The outer shape of the hulls have changed a lot, due to better understanding of the complex hydrodynamics involved in a planning hull, that is evident. But I was referring to the structural characteristics of the hull, the way the whole thing is holding together, the distribution of the load forces. not the shape of the hull s skin.
    "I can't say I'm a fan or follower of the last decade's AC technology - I'm still stuck on 12 meters."
    So now you would be less satisfied with this 90 ft sailing football stadium...:)
    Personally, I like light small things and heavy big things, so we agree that a heavy keelboat sailing to windward is a marvellous thing, even if the 12 meters class rules were not written in any divine wall... But here we are talking about the smallest possible sailing craft that is not a windsurf , so hulls should better be anorexic then obese...And I am not talking for acrobats like the foilers or skiffs with huge sails ! On these crafts, there are many other things that count except lightness, as a minimum stiffness that can not be compromised beyond a certain point. Average, weekend sailing dinghies are not meant to be as stiff or as strong to confront the heavy loads produced by the movements of a huge wave, sail or muscular athlete ! I am talking about the Pico that my 12 y old son can not still throw into the water without a trailer, and I can not upload it on my car s top ! No wonder he is now sailing with my 20 + years old Mistral Malibu he is able to set up and carry easily every time of the day into the water, alone...
    I have not "a board sailor's perspective of dinghies that might be somewhat negative...' Board sailors do not care about dinghies, but dinghies sailors should care about boards! They have cannibalized a far greater portion of the young watercraft enthusiasts than the young dinghy sailors, as one can see by counting the relevant journals in his local newspaper stand...
     
  12. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 139, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    I agree Xarax, boats are way too heavy. but consider several issues, one is the total surface area: the weight will be directly proportional to the surface area. Most small hulls have much more area than a sail board, high tech materials would drive the cost up even higher. As the hull gets larger, the forces on it go up expentially, so the stress is much higher too, even with the same size hull.

    The other curious issue with boats is they have been around much longer, so there is a tenancy to be stuck on "traditional" building methods with hulls. Small boats also tend to get knocked around much more, loaded up much more, and we expect them to last longer with little or no care on landing and launching, and stored outside. See how long your board will last if you always launch it off of a rocky beach rather walk out from shore, or ramming it into the dock each time you come in, and leave it out in your yard year round. Sailboard are just used very differently.

    I built a skin-on-frame 14' sloop that had a completed hull weight of about 40 kgs, I can get it on and off the roof of my car by myself (I lift one end at a time). It is large enough to sail with two adults, or 3-4 kids. You can find pictures of it elsewhere on this forum under $100 boat thread. Others have tried to build and sell skin-on-frame sail boats and canoes, and even sold them as kits, but they just have not caught on. They just do not look like "normal" boats despite their benefits, so skin-on-frame construction are not popular, except as kayaks. Build a small boat out of varnished heavy timbers and everyone says what a nice boat, I'll take one. Build it with an advanced truss frame and light fabric skin, and everyone says "what a strange way to build a boat". Sail boards are built for speed and performance, so they have no "traditional" look to them, they keep changing with better technology, the whole mind set of a typical sailboarder is very different I think than of your average recreational small boat sailor. Often class rules do not even allow you innovate sailboats, so they are mostly stuck with 19th cent technology and appearance, except in a very few classes.

    Make a traditional looking boat, light, tough enough to bang around, and reasonably economical, you might sell a lot of them. But I am not sure that is possible. I have been considering building and sailing a folding sailing dingy, like a skin-on-frame sea kayak, but with a proper sailing rig hull design. It would pack into several large duffles, fit in a car or closet for people without a place to store a boat (like if you live in an apartment or condo), or for use as a tender for smaller cursing sailboats. But I have not had the time to get one together and see if there would be much of a market for it.
     
  13. ancient kayaker
    Joined: Aug 2006
    Posts: 3,497
    Likes: 146, Points: 0, Legacy Rep: 2291
    Location: Alliston, Ontario, Canada

    ancient kayaker aka Terry Haines

    Xarax, it seems to me that, if you take away the freeboard from a dinghy you might as well halve the beam, omit the daggerboard casing and simplify the mast step so you can use the edges and by then you’re left with a board, more or less anyway. There are some advanced dinghies out there, take a look at the paper Dart for example, which is also designed to be a trainer craft with it’s low-end rig. However,

    The amount of money going into boat design has to be balanced with the vast range of boat types out there. There are not, as far as I know, any boards in the multihull, transatlantic, round the world, daysailer, rich man’s multi-berth yacht, foiler and other categories. A board is a board, with a relatively small variation within that category. There's probably as much money going into board development as into dinghies.

    We have to be careful here, by the by. There are folks on the forum that take exception and react with extreme prejudice to suggestions that boards are not boats! :)

    In my case my dinghy is limited by amateur construction, a strong preference for marine plywood - a material I trust - and a dislike of epoxy and glass. Also I wish to encourage my boat-phobic wife to experience a relaxed sail so it has to be decently stable and a bit comfortable. All that in a boat that I can put up on my minivan; it’s a long way up.

    I plan to stand the boat on it’s transom and let it tip until the bow is resting on the roof rack, then I can lift the stern up unaided. With a trolley that will fit into the daggerboard trunk, I will have no trouble rolling her across the beach. That method works for my rotomolded kayak.

    Now that kayak is an unnecessarily heavy boat for you to tut-tut over! Only 9 ft 4in long, and weighs over 50 lb! My 12 ft home-made ply canoe is 22 lb even with it’s rather splendid (IMHO) 19th century style slatted wood seat, replete with tilting and reclining back which includes a boarding aid for a geriatric paddler (unnecessary as I discovered on launching her). My 10 ft 6 in version, designed to fit inside the minivan, is lighter at 15 lb.

    The canoes share the same construction method with the 10 ft sailing skiff, but that will be 50 - 60 lb. The difference isn’t all due to freeboard and beam, there’s a need for beefier construction, reinforced floor due to extra width and standing crew, buoyancy tanks, daggerboard and trunk strong enough to stand on if she capsizes, two mast steps for large and small rigs and a transom strong enough for a small outboard. It all adds up. I hate the way that happens but what can I do? Factor in all those nickels and dimes into the weight of a board and see how it turns out.
     
  14. xarax

    xarax Previous Member

    Thank you Petros,
    Along a high tensile skin over a (space) frame construction , it has even crossed my mind to use some inflatable elements that could add stiffness with minimum extra weight. I was impressed by the lightness, and the durability, of the pack inflatable whitewater rafts, ( 2,5 kilos !). Also, there are some extremely light and stiff closed cell foams that could be used in some parts of the hull.
    I was thinking of a single handed, 3 - 3,3 meters (9-10 ft) long and around 1-1.1 metre wide hull, even if this is a little short for non planning conditions. But reducing the area reduces the weight, reducing the weight reduces the sail area needed for fast planning AND the loads from the water on the hull, as you have remarked. Another way of making a hull easily toppable and transportable would be simply to divide it in two or three parts that can be fastened together easily and quicly. These could be two amas that would fit alongside a stiffer narrow main hull carrying the mast, the daggerboard and the rudder, or two mirror halves, etc.
    The problem is that the average, weekend sailor is, like most average persons or most sailors, a very conservative individual. He is thinking is terms of pre-fabricated /determined concepts and pictures, he is interested mostly in how much, much less in how, and even less in why... and the only way this can change is with time and experience, i.e. very slowly ! Having said that, I also believe that if one builds it, a truly light, easy transportable and easy sailed small dinghy, they will come !
     

  15. xarax

    xarax Previous Member

    Thank you ancient kayaker ,
    I was hoping that you would be the first and best promoter of the idea of a trully light dinghy, but it seems that you have to do with a sensible mid-age wife and not with a wild teenager like I do ! :)
    Kayaks are formidable structures ! I love kayaks, even if i had never been in/on any of them, and I hate rowing too ! The ( real, animal ! ) skin on-bone-frame method of construction, the carefull balance of weight, length and width, not to mention their unimaginable way of righting, I consider kayaks as landmarks of human creativity. And I hope that this creativity, together with the space-age light and strong materials of 21 century, would help somebody to build a single handed dinghy that anybody, and not only Leonardo DaVinci using his crane, would be able to lift on ithe top of a car ! :)
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.