Dinghy Design: Ideas for High Performance Disabled/Physically Limited Sailing

Discussion in 'Sailboats' started by Doug Lord, Mar 7, 2011.

  1. Doug Lord
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    Doug Lord Flight Ready

    There have been a couple other threads discussing this concept to some degree. I'd like to hear any ideas people might have for a high performance dinghy that would be safe for disabled sailing or for people whose physical abilities aren't what they once were. I know what that is like and I still have the need for speed.
    For this thread I'd like to limit it ,mostly, to monohull dinghies. I'm interested in every idea as long as it presents a design concept that might help people who can't move a lot sail fast safely. Some people will surely say it is impossible but don't worry about that-we can look closely at design concepts
    to see if they have the technical chance of success.
    I think monohulls might ultimately be the best way to go because they can be made self-righting. However, I'm building a model(SRT) right now(LOA 5') to test a self-righting multihull concept-automatically self-righting like a keelboat but it is highly experimental.
    In an earlier thread I came up with a boat I called "Trapwing"-see the model pictures below- with a sealed "wing" that slides athwartship. Inside the "wing" is a sliding tray that holds some lead ballast that slides within the sliding wing. The "wing" has more buoyancy than the amount of sliding lead so even with the weight stuck max out the boat couldn't capsize. The ends of the wing are supported by trapeze wires.
    I've tested versions of this concept in RC models and it appears to work well. It would use a small amount of keel ballast to insure self-righting. It too is very experimental in terms of a full size boat but with great potential. The main hull for the experimental tri above will also be used to test the Trapwing concept fullsize.
    There are a lot of imaginative, intelligent people on this forum: rack your brains and see if you can come up with an idea to be much faster than current single handed boats used for disabled sailing-maybe we could make a real contribution to design by coming up with viable concepts.
    --
    pictures- Trapwing model/ SRT main hull small model. Much larger model now being built:
     

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  2. Doug Lord
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    Doug Lord Flight Ready

    Dinghy Design: Ideas

    From another thread:

    I just found some details about a story that I'd heard a few years ago-about
    "Herreshoff" experimenting with on-deck sliding ballast.
    This is from a book "Herreshoff Sailboats" by Gregory O. Jones and lays out some interesting details of the first recorded use of on-deck iron sliding ballast that I've been able to find. Apparently, new rules and sheer terror got in the way of further development though the two boats that used this form of ballast were very fast. The Seawanhaka Corinthian Yacht Club, formed in 1871 banned movable ballast.
    Charles Herreshoff built four "Julias" ,the second was outfitted with an athwhartship track for 550lb. of iron ballast to slide. The method was to release the ballast from the windward side and allow it to slide to leeward just as the boat tacked. Charles designed a larger boat "Kelpie" that his two sons built that used a larger sliding ballast system-1000lb! Kelpie was very fast.
    This stuff is exciting to read about and one can only speculate how these systems might have been refined over the years. I think modern versions of systems like these using lead or water have a tremendous potential in high performance boats of all sizes. I'm going to concentrate on small boats where I see an exciting opporunity to explore this interesting technology.
     
  3. Doug Lord
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    Doug Lord Flight Ready

    Dinghy Design: movable ballast

    Julian Bethwaite took the time to say that he thought my "Trapwing" concept had merit in the post below. Some of you may not know that Julian Bethwaite, Paul Cayard and Russel Coutts collaborated on a concept called Pterodactyl: nominally a monohull and designed to use movable ballast sliding athwartship at deck level. More:
    ----

    Thanks again to Julian Bethwaite for the comments and information posted here:
    -----------
    One of my inspirations -that has bolstered my own work on this project- is the Bethwaite/Billoch collaboration on the concept of Pterodactyl-which was conceived of to use on-deck movable ballast. Here is the original SA article: http://www.sailinganarchy.com/fringe...teradactyl.htm
    --------------
    What wasn't known then was what Julian says about it here. I asked him to comment on the Trapwing which he did in a PM that I'm publishing here with his permission. He reveals who was behind the Pterodactyl project:

    "A few years back these pages graced a thing called the Pterodactyl, it was a big double proa that Russel Coutts and Paul Cayard asked me to do as the ultimate circuit boat. Among other things its nice to see the OMR*go that route, but Russel was big on having 3 tonne of lead on tracks moving from side to side, inside the wing beams. I thought moving water through 200mm diameter pipes would be better, but the concept has merit. Your issue is that unless you have significant tip pods, then you will never be able to react quickly enough to keep the wings out of the water. Just cant do it! "

    *Ocean Multihull Rule: it is the predominant rating rule used in Asia (and
    Australia) it seems for handicap racing in this part of the world.(dl)

    Pictures of Pterodactyl: (click on image)
     

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  4. Doug Lord
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    Doug Lord Flight Ready

    Here is a site with a number of boats targeted for disabled sailors:
    The International Access Class Association: http://www.skud.org/


    Pictures, left to right: Access 2.3, Access 303, Access Liberty and the Skud 18:
     

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  5. Doug Lord
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    Doug Lord Flight Ready

    The International 2.4 Meter is one of the largest classes suitable for the kind of sailing I'm talking about-except that it's not real fast. I'm told it is a real blast:
    http://www.inter24metre.org/
    ----
    Mark Bryant of Mark Bryant sailing is a well known builder of the 2.4 Meter and has also expressed interest in the Trapwing concept.
    http://www.markbryantsailing.com/mbs_index.php
     

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  6. Doug Lord
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    Doug Lord Flight Ready

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  7. timo
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    timo Junior Member

    I think this is a fantastic project. In terms of design for disability - there are a lot of things to think about;

    Simplicity: Complicated systems start requiring specialist skills and expensive design- otherwise they can become dangerous. Is a lead ballast moving athwartship fool proof and absolutely safe?

    accessibility: is it a moored vessel or launched from a slip? Will the person to pilot the vessel need help to get in and out / launched?
    can the person operating the vessel get to all area's - ie say a pulley jams at the bow can they get to it to unjam it?
    A disabled person may be harnessed in the vessel. If 'he' comes to trouble will he be accessible to ppl that come to help?

    failure: say a mechanical balast system fails, how will the operator fix it or is it better to try and eliminate potential failure.
    low tech solutions can be far more reliable and easy to fix.
    mechanical failure is everpresent - especially in a marine environment where mechanics have to deal with water and corrosion.

    capsize: say the vessel does capsize despite being very stable - can the person get out? is he harnessed in? how fast can the vessel correct itself?

    operation: how will the pilot operate the vessel - is there a multitude of functions that need to be done automatically?

    failure of pilot: who can operate the vessel (degree of dissability)? is the person prone to muscle spasms, black-outs, cardiovascular associated problems?
    what happens if the rig is sailing full tilt when something like a black-out happens? will the vessel continue or stop? Will there be warning to let others know there is a problem?

    Some idea's:
    Does a suction develop at a sail lying flat on the water? Can this hinder the rate of the vessel to correct itself. Can the sail/mast have a quick release system to minimize suction and drag when self-righting?

    Basically we want to be able to move the centre of gravity - is it possible to combine the design of a keel and movable ballast? - ie can the keel move from side to side? (Bear in mind failure)
     
  8. timo
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    timo Junior Member

    Maybe keels, outriggers and ballasts are not the place to look - maybe its time for other technology. Something relying less on weight and something less limiting and bulky(limiting as in a keeled boat can only go so shallow and a disabled person may find a boat that can go in shallow water easier vs a cat or outrigger design that is bulky).
    Maybe hydrodynamics and new sail type systems can be used for keeping a boat upright.
     
  9. Doug Lord
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    Doug Lord Flight Ready

    ====================
    Timo thanks for your thoughts and your posts.
    1) A sail can certainly cause a bit of suction but usually slacking the sheet prevents it from being a problem. Problems with sock luffs holding water and any design that allows the sail or mast to fill are important to prevent. A disabled design should be automatically self-righting with no crew action required other than slacking the sheet(s).
    --
    2) Moving inanimate ballast can be accomplished in a number of ways. Water ballast can be pumped side to side, a keel can be designed to cant(pivot) side to side. Most of the large fast monohulls like Open 60's and Volvo 70's use a canting keel pivoting 40-50 degrees each side. Some canting systems have been designed to pivot 90 degrees or a little more to lift the keel out of the water when the boat heels though none with that facility have been built. It can happen on an Open 60 or Volvo 70 but it is accidental and not fast.
    For a high performance dinghy I think a movable ballast system like I described in the first post is a good choice since it allows a drastic increase in righting moment for a nominal amount of weight equivalent ,say, to another crew 6-10' to windward.
    --
    There are all kinds of possibilities , perhaps using hydrofoils like the DSS system that extends a foil to leeward thereby creating lift and righting moment. One guy came up with the idea of water out on some sort of extension.
    For high performance I think the key is finding ways to substantially increase RM with the skipper sitting in the center of the boat. I have no hesitation at all about using electrically powered systems to move the ballast because sophisticated electric onboard steering and sheeting systems have been pioneered by disabled sailors in classes like the 2.4 meter and Martin 16. You can go to the Martin 16 site and see some of what is already available.
    The priorities, as I see them, for developing a high performance design suitable for disabled or physically limited sailing are:

    A) A method to develop high righting moment
    --
    B) A design that ensures that the boat is automatically self-righting.

    The "checklist" in your post above is excellent-thanks.
     
  10. CutOnce

    CutOnce Previous Member

    The first item in the priority list should be:

    1) Any failure of any component in the systems on the boat result in safety for the user. "Fail safe" is a concept used in development of systems that can affect human life. I've been involved in medical systems technology and this concept is always the most important priority. If any part, component or subsystem can fail unsafely, this concept should not be promoted.

    --
    CutOnce
     
  11. Doug Lord
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    Doug Lord Flight Ready

    -------------------------
    Could you rephrase this?
    I agree with this as far as it is practical within the design, construction and operation of a sailboat including electromechanical systems used to meet the criteria of the first post and to aid disabled sailors in performing the functions required to sail the boat.
    It is imperative, in my opinion, that new thinking and innovative design be encouraged with the primary goal of meeting the criteria of a high performance, self-righting dinghy for disabled and/or physically restricted sailors. A prototype of such a design should :
    1) make sure that all on-board systems meet or exceed the standards currently adhered to in disabled dinghy design and in disabled electronics assist technology.
    --
    2) be developed and rigorously tested with active participation by disabled sailors and organizations who exist for the benefit of disabled sailors.
     
  12. tabman
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    tabman Junior Member

    One thing that should be considered is the ease of getting along side the boat when it is water to rendering assistance. Sailing with my daughter in the Access 303 for Special Olympics there were a few times that sailor needed help including removing them from the boat out on the water. The 303's simple open cockpit combined with with the boat's good stability made this an easy option. In fact it was easy to sail up along side another 303 and help sort things out, give a pep talk or pass a drink.

    The idea of outriggers will add complexity to doing this.

    I agree with Chris regarding "Failing to Safe". The idea of the sailor being in a harness gives me shudders.

    Timo's point about "failure of pilot" is excellent. The boat MUST assume a stable and stopped (or slowly moving) attitude when there is no input from the operator. Ballasted mono-hulls like the 303 (it has a very heavy dagger-board) will usually round up into the wind and jog along luffing if you take your hand off the helm.

    The ability to quickly reduce sail area is important. Being able to quickly de-power the boat is very important in building confidence when learning.

    If the boat does not sail well in a very wide range of conditions, it will be a failure. Being able to sail well in drifting conditions or in high wind and wave conditions will allow lots of sailing time, and allow regattas to be held in different places without having to depend on conditions.

    Tom
     
  13. Doug Lord
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    Doug Lord Flight Ready

    ==============
    Thanks for your comment, Tom. One of my self-imposed criteria has been that the boat is 100% self-righting. Apparently, that it not the case in a whole host of designs used for disabled sailing. However, most disabled sailboat designs cannot be classified as "high performance". I'd think that a trully high performance boat should be self-righting.
    -----
    There are at least two small multihulls being used for disabled sailing-neither of which is "high performance":
    The Challenger and the Weta.
    --
    Video about the Weta being used for disabled sailing: http://www.musicaperu.org/peru/s9sz277VrWg/SAILING-STANDARD-WETA-TRIMARAN-BY-DISABLED-PERSON.html

    pix: Challenger and Weta(click on image) :
     

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  14. tabman
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    tabman Junior Member

    1) A sail can certainly cause a bit of suction but usually slacking the sheet prevents it from being a problem. Problems with sock luffs holding water and any design that allows the sail or mast to fill are important to prevent. A disabled design should be automatically self-righting with no crew action required other than slacking the sheet(s).

    Even that may be too much. . .
     

  15. Doug Lord
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    Doug Lord Flight Ready

    Here are the design specifications for the prototype that will be used to test the Trapwing concept. The hull for the Trapwing will also be used to test the SRT(self-righting trimaran) whose specs are in the next post. I have been delayed on starting this prototype by the intercession of real life. I hope to overcome those problems and proceed with the full size build sometime this year. No model will be tested of this boat because I have built and test numeous RC models of the Power Ballast System over the last ten years with many ,many hours of sailing in all kinds of conditions. The Trapwing concept has passed the model tests with flying colors with excellent results.

    =================

    A Summary of the Trapwing concept:

    In the course of this thread and a couple of others various incarnations of this concept were considered. The final "incarnation" came down to the Trapwing 15 for which you can find sketches and numbers in an earlier thread. Due to some fortuitous events I was able to get my original 16' foiler hull back and then made the decision to go with it as the prototype for developing this project. The 15 remains the ideal version of the planing version of this concept(so far) and will likely be built after the Prototype is thoroughly tested and explored. The Prototype hull based on the 16 is a bit narrower than ideal but it is an all carbon hull and ideal for a relatively quick conversion to a sailing prototype. So, that's whats next- and here are more details that reflect the modifications to the topsides and bow that change the 16 into the Trapwing Prototype. The prototype is shown with weight and sail area ranges that reflect the potential capability of the modified hull as well as the tests that need to be made. The suitability of the concept to disabled sailing will be determined by sailors involved in disabled sailing. Engineering, as required, will be done by a Naval Architect and Marine Engineer with electronics expertise as required. Performance testing will be exhaustive with help from one of the top marine testing laboratories in the US.
    ===========
    The following is a detailed look at the characteristics of the new Prototype, as well as the design elements it will encompass and test:
    -----
    Trapwing Prototype:
    LOA 18'
    Beam hull-3.25' overall 12'(subject to testing)
    Weight- hull 138+38=176(corrected from original post mistake)
    ballast-wing 80-180lb(variable and subject to testing)
    keel 0-80(subject to testing)
    SA-upwind 100-182 sq.ft. variable
    downwind 200-360sq.ft. (variable and subject to testing)
    crew-singlehanded-120lb-220lb (variable and equalized under class rules- subject to testing)
    crew position for racing on the centerline inside boat, fixed
    athwartships, variable fore and aft
    --------------------
    1) Sail area to be between 100 and 182 sq.ft
    a-different rigs
    b-different amounts of ballast
    --
    2) Ballast wing to be supported by trapeze wires and unique retention system that allows wing and ballast to slide simultaneously, allows athwartship pivoting and fore and aft movement.
    a-version one will use two aluminum tubes with sliding external tray- the tubes and tray move simultaneously:
    -attachment system allows wing- with weight centered-to be levered up and then pivoted from a position 90 degrees to the CL to a position parallel to the centerline for transport and stowage.
    -weight can be added or removed in small increments.
    -fore and aft pivot/sliding tube is mounted to the boat slightly offset from the CL to allow room to retract board/keel.
    -aluminum tubes terminate at outboard ends in buoyancy pods-pods will be changeable as determined in testing.
    -sliding ballast tray and structural design of wing to be capable of 180lb max ballast @9' from CL; ballast completely adjustable in the range of 80 to 180lb.
    b-version two is a slightly curved(athwartship), molded and sealed(with seal-able access to ballast tray) wing with an internal sliding ballast tray. This version will be the final version and incorporates all the features of version one with significantly increased sealed buoyancy.
    c-Wing movement by manual or electric means. Minimum electrical movement full out to full out:4.5 sec. Minimum electrical "stamina" on single battery-12 hours at a rate equivalent to a approximately 60 (full track)tacks per hour. Manual back-up.
    --
    3) Crew Position
    a-version one-racing position-allows crew to sit in an extremely comfortable seat that is fixed athwartship and slides fore and aft adjustably while sailing.
    -extremely wide crew weight range:for racing lower tray attached to seat may contain ballast used to equalize crew weight in the range of 120 to 220 lb.
    -seat may be moved manually or electrically.
    b-version two-center seat is removed and two fixed carbon seats with backrests are "plugged-in" to each side deck.
    --
    4) Rigs to be tested are main and jib, main alone, with and without an asymmetrical spinnaker.
    a-asymmetrical will be tested as permanently mounted off a bowsprit(a la Weta tri) or retracted into a trough with roller(a la Viper) and a retractable pole.
    b-mast to be sealed with masthead floatation in an endplate configuration. Some buoyancy possible in head of sail.
    --
    5)-Daggerboard/ keel/rudder
    a -boat will be tested with and without a retractable "lifting keel"
    which would essentially be a carbon daggerboard with the minimum ballast required(determined in testing) to right the boat from a pitchpole(where the wing buoyancy may not significantly help).
    b-self-righting from a knockdown or pitchpole is a required design element for any version of the boat used for disabled sailing.

    c-a turbo version of the boat will not use a ballasted keel and may not be suitable for disabled sailing but this will be determined in testing.
    d- the daggerboard may include as standard a lifting hydrofoil designed to provide "foil-assist" to reduce wetted surface and in conjunction with the rudder hydrofoil improve the pitch and planing characteristics of the
    boat.
    e-a fully flying hydrofoil system will be tested as will a fully flying system that allows the boat to fly downwind only(requiring less upwind SA and less ballast).
    f-rudder will be retractable with a t-foil.
    --
    6)-On the Beach
    a-the boat will be able to be easily beach sailed with a dolly incorporated into the trailer design to make it very simple to go from trailer to water. A "power assist" dolly may be available. Disabled sailors/coach(s) will assist in the design of systems to allow launching and use of the boat with the minimum outside assistance possible.
    --
    7)-Performance
    a- the goal is to develop a high performance planing sailboat that can be safely sailed from a center crew position by disabled or able-bodied sailors. I am hoping to be able to achieve an SCP/total weight of 30% or slightly better though that is just a target and a less powerful version with numbers and performance more like a Windmill or Tasar may be perfectly acceptable. The use of foil-assist technology will help to achieve the performance goals. Full flying foiling is possible in a self-righting boat-particularly one with the righting assist this boat has from version two of THE Wing.
    -------
    The concept has extraordinary potential and it will be a blast finding out just what she'll do.

    -------------------------

    DESIGN RATIOS(Trapwing prototype in its most powerful initial configuration)
    LOA 18( not including retractable gantry)
    LWL 17.7
    Sailing weight 653lb w/keel, 573 w/o keel
    ----
    Displ./ Length Ratio: 52.7
    --
    Sail Area to Displ. Ratio: 38.66
    --
    Sail Area/Wetted Surface: 4.23/1 w/o foil assist
    5.87/1 with foil assist
    --
    S number: 9.61


    =========================================
    Thanks to Eric Sponberg for introducing me to the "S number" and for publishing an excellent series on all these ratios.(see pdf below)

    Pictures show smallest rig and (probably) largest rig--click on image:
     

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