Designing a sailing dinghy for expeditions

Discussion in 'Boat Design' started by BoraBoats, Feb 25, 2019.

  1. Tiny Turnip
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    Tiny Turnip Senior Member

     
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  2. sailhand
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    sailhand Junior Member

    I think it is a wonderful challenge to approach the design from what may be perceived by some as the opposite direction. To prioritise the end users requirements above all else can result in entirely new combinations of older existing technologies and the development of original and unique vessels. As an industrial designer you may be required to apply this "thinking outside the box" approach to any and all projects you work on to some degree. The possible evolution of concepts at a far more rapid pace than most of us on this forum are used to, and some may even be uncomfortable with. I have seen amateur design efforts on this sight that have created a looming sense of doom and disaster, and others as innovative and inspired as I've experienced. I for one appreciate the efforts of all contributors to the forum no matter the content of their posts. It is after all the good that make the bad and vice versa. Every idea has merit of some description inherent in its content event if only to inform us of what not to do.
    I perceive these efforts as one giant brainstorming exercise and always look forward to new and exciting discoveries, like some old prospector in search of the mother load. As a designer I like to think I challenge the boundaries just a little and not just "conform to the norm". You may find inspiration for some aspect of your design, in particular the transition between land and water and handling ashore, by googling magic carpet 3.5 with a three horsepower. The ideas behind most of my designs are far from new, they just evolve from a different perspective. Good luck and keep us informed of your progress.
    I suppose my two cents worth here for a small cruiser would be that multihulls offer stability beyond that of monohulls. Unfortunately that includes when they are inverted. Multihulls are usually faster for a given length and monos carry a greater load. One design that moves almost from mono to multi via folding amas at will, pedals rows or sails, is easily rigged and reefed, and easily moved from land to water, and vice versa, is the Hobie Adventure Island. There is a lot of novel concepts in this small package that would benefit greatly from a fresh approach and a good quality lightweight build. Having owned and used several Adventure Islands from the Hobie stable I see great merit and versatility in their novel approach, that not unlike your task at hand, approaches the concept from a different perspective and results in a spectacular combination of versatility and originality .
     
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  3. BoraBoats
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    BoraBoats Emilie

    Thank you, sailhand, for your encouraging words!
     
  4. Clarkey
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    Clarkey Junior Member

    I agree that it is an interesting brief and quite achievable with proper attention to functionality and materials selection. It strikes me that it requires a mindset more like that of ultra-lightweight climbers/trekkers and cyclists than that normally associated with dinghy cruising or sailing in general.

    The Hobie Adventure Island is a really interesting example. I suspect that it was originally targeted simply as a leisure product but has gone on to prove itself in any number of extreme expedition scenarios - from dominating the Watertribe Everglades Challenge (at least numerically) to being picked up off the shelf and completing the Race to Alaska. It is pretty heavy but that is a consequence of rotomolded construction. A lightweight version would be quite easy to do albeit at added cost, though in my experience developing some products for the climbing and marine world dedicated users such as your 'expedition' types are prepared to pay a premium for technical products that offer significant performance advantages.
     
  5. BoraBoats
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    BoraBoats Emilie

    Yes! I think it should be the "mountain bike of dinghies".
     
  6. BoraBoats
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    BoraBoats Emilie

    Project Update 4: Concept 1
    Concept1_1.jpg
    The concept is combining three principles:
    1. A good rowboat is often narrow and has outriggers for correct position of the oars
    2. Kayaks with sails often have buoyant outriggers for stability
    3. Several sailing dinghies, like Tiwal and Waszp, have a frame that gives the crew a greater moment of force when hiking
    Concept1_2.jpg
    Concept1_3.jpg
    The boat has a narrow hull shape and a frame with buoyant elements that provide extra stability. The frame also creates a good position for hiking and an ergonomic oarlock position. A canvas is covering the frame and, together with the buoyant elements, is providing comfortable seating. The frame can be disassembled for easy transport and sailing in protected waters where the extra stability is not needed. I wanted a narrow beam because it would make the boat easier to handle. The boat can transform from a sailboat to a rowboat, but it might also be possible to explore other uses. The goal of this concept is a boat that is easy to handle, robust and flexible.
    Concept1_4.jpg
    Concept1_5.jpg
    This is a concept sketch and the details and dimensions are not decided. What do you think of the main idea of having a narrow boat with “wings”? Could it work? I am concerned that the wings might cause a problem in high speeds, but that might be a question of how they are angled. What will happen if the wings slam into the water in high speeds? If I increase the secondary stability of the dinghy by having the wings, could I then decrease the initial stability and have a narrow hull? Or would this make the crew use a lot of effort on stabilizing the boat even in light winds and make long trips exhausting?
     
  7. Clarkey
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    Clarkey Junior Member

    I think it is a good initial concept. There have been a number of attempts at adding buoyancy to wings on narrow hulls but they all tread a fine line between being a monohull with 'training wheels' and just going the whole way and becoming a small trimaran.

    Racing dinghies generally need to sailed in a dynamic way, with the crew exerting themselves to keep the boat flat and respond to changes in wind - which is a large part of what makes them fun. However I believe a boat which may be used for longer passages needs to have another 'gear' where the sailor can reef down (or otherwise de-power the boat) and take a more passive role, more reliant on the inherent stability of the boat (which is how I think a lot of the small 'sit in' trimarans operate). The tricky bit will be finding a design that can operate satisfyingly in both modes.

    With that in mind, here is an idea. How about a really narrow hull, just wide enough to provide a mast step, daggerboard case and rudder mount. Then attach two big, buoyant, wings to it with hinges so that their dihedral angle can be adjusted. You could pull the wings up high to provide a responsive, dynamic dinghy like a Moth or RS300 or lower them horizontal to make a stable, raft-like, platform for resting on at sea or camping.
     
    Last edited: Mar 1, 2019
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  8. Dolfiman
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    Dolfiman Senior Member

    I saw the various YouTube videos on "Sailing winter Norway" and Hobie adventure in rough conditions, the main difference is the exposure to green water, the Hobie is really very wetty for the crew as for the camping equipment on board, it is an horizontal shower at every minute, I can't imagine that within 8-10 hours of sailing, moreover in icy waters. I think that the Hobie trimaran, with quite low free board and the crew itself low in the boat, is adapted for sheltered waters with waves up to 0,3- 0,5 m but not fore coastal but open waters with waves up to 2 m.
    These highlights on the green water exposure, an important aspect, extreme expedition should not turn to unpleasant masoschist one. In my brain storming contribution here attached, I propose a half-decked dinghy with fore and aft protected storages for camping and sensitive equipment (electronics, papers). Fore and aft, instead of just Fore, also useful to distribute the masses and maintain an optimal trim despite the payload.
    The second idea is about stability, I share Clarkey comments here above, there is a need of both a sufficient initial stability when upright (for the general confort, to tack and to gybe by breeze and rough seas) and a need of sufficient righting moment without acrobatic posture : I propose attached a monohull bi-convex concept, with a sufficient Bwl + additionnal buoyancy acting when heeled at more than 10°. That can also prevent the spray to go up.
    And the third idea is from the Jimmy Skiff 2 concept : a central cockpit L 205 cm x 76 cm, clear of everything in order to make a confortable berth by night, + the boom can be use as support of a tent. And for that, a daggerboard put with an offset / boat axis.
     

    Attached Files:

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  9. BoraBoats
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    BoraBoats Emilie

    Thank you for sharing your ideas! I can only see drawings of the first idea in the attachment, do you also have drawings of the second and third?
     
  10. sailhand
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    sailhand Junior Member

    I think using the hobie adventure island concept for inspiration for a new design is the idea here. The combination of easily deployed/reefed/completely removed rig in seconds is a valuable idea in a small boat. I also like the ability to reduce the beam/swing in the amas to assist in righting the boat as well as providing ease of sailing. I dont think copying an existing design is likely to acheive the objective of the OP. A different central hull design perhaps. Similar to ocean crossing row boats with higher buoyancy to prevent stable inversion and provide accommodation, storage and a protected central helm position. If the boat was inverted, worst case scenario, the boat could be recovered by folding in the amas and allowing the bouyancy of the cabins to assist in righting the boat. A mast top float would help to avoid complete inversion and also the possibility of furling the sail whilst capsized to help right the boat would be a helpful feature. Again actually copying a hobie is not the idea just a conceptual framework with many useful attributes. Long distance sailing in a small vessel would be far easier with simple sail handling and steering from a comfortable central helm position, the proverbial armchair ride.
     
  11. sailhand
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    sailhand Junior Member

    Another design worth a mention is the G32 cat of the gougen brothers. The main aspect of this design that may be applicable to your project is the ability to recover from a capsize. I think they have the ability to cant the mast to the extent that they can move the centre of bouyancy of the submerged hull towards the mast float on top of the mast. When this is done the weight of the higher hull and the bouyancy of the lower hull work together to rotate the hull upright again. An ingeniously simple idea worth investigating.
     
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  12. Dolfiman
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    Dolfiman Senior Member

    Bi-convex section proposal is in the lower half of my pdf, you cannot see it ?
    Central cockpit/berth and daggerboard offset on port is showed on the drawing in the upper half.
     
  13. BoraBoats
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    BoraBoats Emilie

    Ah, my bad!
     
  14. BoraBoats
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    BoraBoats Emilie

    Just watched this video of G32:

    Such a cool boat!
     

  15. John Perry
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    John Perry Senior Member

    My own attempt to meet a similar objective is described here: http://www.hostellerssailingclub.org.uk/index.php/articles/building-a-dinghy-for-cruising. This boat was first launched in 1978 and has been extensively used since then, including a number of cross channel passages of 50 to 70 miles. Its good to see you are designing to meet fairly similar requirments. If someone with little or no sailing experience attempts to design a sailing boat I think the chances are that they will produce a boat that does not work well in practice, but there is also a (smallish) chance that they will come up with something quite different and better than anything that has been done before!

    Your initial sketches look nice. Re. your question about the 'wings', there are many sailing dinghies with 'wings', the olympic skiff class for one. I have not sailed such a boat but I imagine that the wings may slam into waves a bit but you have to remember that when sailing to windward in even a bit rough conditions the whole hull will in any case be slamming into waves, bouncing arround and soaking the crew with flying spray. I would say that fixed 'wings' would be an absolute pain when coming alongside quaysides or marina pontoons, how would you arrange fendering or avoid the wings getting trapped under a pontoon deck? A sailing dinghy intended for the kind of expeditions you have in mind needs to be versatile, sometimes you may like to spend a night landed on a beach (but only in benign conditions!) other times you will prefer to be anchored in an estuary, tied alongside a quay in a harbour, dried out in a harbour or tied to a pontoon in a marina. Small folding 'wings' are a possibility I have wondered about. Assuming that the rowlocks are at the edge of your 'wings' you have obviously drawn the oars too short for the width between rowlocks. Racing rowing boats generally have about 1600mm spacing between rowlocks although for non-racing purposes a lesser spacing is possible and allows the oars to be shorter. 1600mm is actually quite narrow overal beam for a winged sailing dinghy, many of these seem to be designed so that the wings extend to the maximum width allowed for road trailing. If you keep the wing width to 1600mm you will need the oars to be around 2850mm long, so where will you keep these oars when you are sailing? You could have the oars in sections but sometimes you need to use the oars in a big hurry - every second counts so you dont want to be fiddling with assembling oars from sections.
     
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