V- Twin a concept to make a fast mono easy..

Discussion in 'Sailboats' started by G.R.F, Apr 28, 2011.

  1. G.R.F
    Joined: Dec 2010
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    G.R.F Junior Member

    Now I've made a bit of progress, beyond just sketches and computer renders, I thought I'd widen the audience a bit.

    Basically why and what are in this blog rather than post all the pics over again and it's been on the Y&Y forum for some time in a 'should I-shouldn't I' kind of discussion, it being a bit left of field in regards to modern thinking.

    Anyway, I'm now committed to it and the rig options are under discussion, I shall probably use a known rig to first prove the hull works, then I'm considering other options, and it's what those options could be I'd like to provoke some discussion on.

    I'm looking for light, depowerable, want an assym kite, am thinking self tacking jib on a boom, anyway any radical ideas would be welcome...
     
  2. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    Hey GRF, looks very interesting. Are you familiar with the M20 tunnel hulled scow? Designed to sail at an angle of heel-the tunnel reduces wetted surface. I think you're right about the wider bow.
    You might be interested in some thoughts I had on the use of curved lifting foils in dinghy design. Inland lake scows use twin centerboards-see the sketch below of a tunnel hull inland lake scow modified with a curved lifting foil. If you're interested in more detail check out the last page of this thread-there is an index of sorts and a summary-check it out. http://www.boatdesign.net/forums/sailboats/dinghy-design-open-60-influence-36401-10.html

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    The Wing Tip Rig below has been tested on my full size foiler and on numerous models-seems to have some potential. The newest version on my next boat will have a small jib boom with a pivot point set up like a model except that the pivot slides athwartship keeping the leading edge on the centerline.

    pictures L to R: 1-4- wing tip rig with square top jib-attachment of jib is with short "gaff" whose pivot point can be adjusted-allows whole rig to twist-not just individual sails. 5-6 shows a single curved lifting foil that slides in an athwartship, continuous partially open trunk. Develops vertical lift and lateral resistance. Crew has to slide board across unless boat has a sliding seat which can then be used to "automatically" move board. Board 100% retracts and can be an asymmetrical section. 7-tunnel hulled scow with dual curved lifting foils("normal" scow uses board that is vertical when boat is heeled.)
    8-sliding jib boom track

    click on (some) images:
     

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  3. G.R.F
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    G.R.F Junior Member

    Hey I'm really interested in that rig, what's going on there? (Try and explain it to me as you would a child, I'm not that au fait with all the dinghy rig terminology, I'm told what I'm looking at with my jib is a 'dangly' pole which I've got no idea about and then they go off on one discussing 'barber haulers' something else I've really no idea about and actually don't want to know if it's 'last century'.

    But that top bit of the rig in your pic looks to help build a jib that will twist, I'm guessing now..

    And yes someone else mentioned a tunnel hulled scow moth, and this is kind of a tunnel hulled scow, my logic, split the planing area, do away with the need for flushing strips, give me more righting moment, dump a hull upwind (and maybe down) and sail it widewindsurfboard style upwind if the conditions (flat water) permit.

    And knowing your interest in foils I had also thought of comissioning one of our local foil experts to build me a foil that would retract up inside the tunnel when launch and recovering and presto - you could be one step nearer your 'everymans' foiler, who knows, early days yet. Don't even know if it'll do the stuff it's supposed to.

    I'll keep y'all posted though, love to hear more about that rig (has to be easy to single hand, hence the jib boom idea like a boat we have over here called a K1).
     
  4. Doug Lord
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    Doug Lord Flight Ready

    GRF, the rig is designed to be sailed singlehanded which is super easy using a version of the Swift Solo sheeting system. The square top jib allows automatic gust response from the jib as does a square top main. The unique part of my arrangement is that the jib head is supported by a small "gaff" that
    allows the camber of the upper part of the sail to be adjusted before you go out and allows the leading edge of the upper part of the jib to rotate to windward. This allows both sails in unison to have a small amount of twist so that viewed from above, the whole rig appears to be slightly twisted-like washout on an airplane wing. The twist of each individual sail is also adjustable. See below for the schematic of the Swift Solo sheeting system which allows main and jib to be controlled with a single sheet but also allows jib slot control thru the "relativity" control.
    ======
    The curved lifting foils are, in some ways , better than a t-foil in that they can be fully retracted. There is additional hassle in controlling them in tacking and gybing but that can be automated in some cases. The single curved lifting foil can be partially or fully retracted without getting in the way of the vang and/or boom. The best application is probably as "foil assist" where the foil lifts the boat enough to reduce drag significantly though twin curved foils could be left down downwind and probably fly the boat. At no point do these curved lifting foils need an altitude control system(wand). And by pivoting the head of the board fore and aft the angle of incidence can easily be adjusted if you feel the need, The cool thing about curved lifting foils is that the lift profile(degree of vertical lift) of the board can be adjusted by slightly retracting the board without reducing the lateral resistance the board develops. This trumps straight angled boards by a long shot.

    picture: Swift Solo single sheet system for main+jib

    click on image:
     

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  5. CutOnce

    CutOnce Previous Member

    I'm in no position to comment on your decisions regarding hull design, but I certainly do understand the result you are trying to achieve. I'm in the middle of the first year of my second half century, and am facing a lot of the same issues - my single hand trap/asymmetrical skiff demands a lot from me, and I can see a point in time where I may not be able to supply the needed effort to keep it upright and fun.

    You've obviously tried the Alto and RS100 route, and are looking for better answers.

    I'm currently mulling over my next project, and I'm already reaching some design conclusions similar to yours. I want comfortable, fast enough to be fun, stable enough to be able to turn my back on it, and big enough to go out with a friend (acknowledging performance degradation). I also want home build without high end materials & equipment.

    I'm aware that my choices are a little more "low-end" than yours, but my budget and build resources are apparently more limited as well. I don't mind the odd swim, but want this to happen less frequently than it does now.

    Like you, I want to re-use existing rig components. 29er kite for a masthead asym etc.

    My basic goal is faster and more fun than a Laser, low cost home build and ability to take my son (& wife) out. Want really low weight as well. Willing to give up compound curves beyond what I can develop in plywood.

    Once I get further down the compromise trail I'll post more thoughts. I'm still willing to consider a catamaran, but like the easy one-man mobility of a monohull.

    --
    CutOnce
     
  6. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    ===
    You should consider a boat like a WETA trimaran. Its light, easy for one person to handle and capable of taking others for a ride. A similar design could easily be home built and you would have a fun boat that could transition with you for years.
    I think GRF's boat will be somewhat "easy" and a very interesting concept to try out but I think there are ways to design faster boats that are easier to sail and build.
     

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  7. CutOnce

    CutOnce Previous Member

    Doug:

    I like the Weta very much, but between the current economic climate, planning for retirement & educating my son etc., I'm just not comfortable writing large cheques for boats. If I thought like most North American consumers, I probably would, but I like having no debt.

    I also get more satisfaction out of building boats than most people. The journey is as much fun as the destination for me. My current vocational revenue-generating work is not visible and tangible to 99.99% of the world. System design, implementation and coding secure communications is a great mental challenge - but you can't point to it and say I made that. Boat building gives me a tangible output and shows progress visibly.

    I'm also going to do 100% of this design myself - I've been practicing & working with various naval CAD tools for a while and feel the need. My last two projects were done in co-operation with a naval architect friend, and I felt the designs deserved better treatment and promotion than they got. Designer attention spans are not very long - as soon as another shiny object rolls into view, they are off like a kitten chasing a laser pointer. When someone else owns the design, you have no real say in what happens, even if you were an integral (if not critical part in) it's creation.

    I'm a big fan of Graeme building this boat, and the decisions he made to arrive at a real build. I think my path is going to arrive at something a little different, but that's okay too.

    I don't think his boat is going to be easy - he's been at this a long time and will probably err to the side of too much power. He's also in the UK, and the whole country is mad as hatters right now in the run up to the Royal wedding. If I hear one more report about Wills & Kate I will barf.

    --
    CutOnce
     
  8. Cheesy
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    Cheesy Senior Member

    How does the jib auto de-power? is this controlled by the 'gaff' stiffness? also how do you generate sufficient leach tension, is there a cord going from the top corner of the leach to the crane?
     
  9. Doug Lord
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    Doug Lord Flight Ready

    ===========
    The jib head "gaff" is attached to the halyard about 30% of the length of the head aft. This attachment point is adjustable fore and aft along the gaff. The gust response of the jib is adjustable by moving this point and by increasing or decreasing leech tension. Leech tension on the original version was adjustable in the "normal" way by adjusting the angle of the jib lead. On the original full size version of this rig we learned that the jib head should be bigger and that controlling jib leech tension would work better if the sail was on a jib boom like a model sailboat with the pivot point on the boom adjustable fore and aft along the boom. The problem with that is when done just like a model the leading edge of the jib rotates to windward which adversely affects pointing ability. The solution was to slide the deck attachment of the jib boom pivot athwartship on a ball bearing track. Works very well.

    see picture #8, Post #2.....
     
  10. BWD
    Joined: Aug 2006
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    BWD Senior Member

    GRF I see you cut some molds, but....
    imho you'd best lose the chines in the tunnel till aft the daggerboard root or that thing may ventilate spectacularly once it's moving.
    And if it doesn't vent, it will generate enough suction to to dechrome all your fancy bits.
    BTW if I'm right, you owe me a quiver of fuels.
    :p

    Or ya could do separate P & S side boards -they could double as preventers :lol:

    More seriously, another viable alternative you will probably explore is moving the the board fwd the depravity (err, concavity).

    Anyway, easy enough to make a submold to fair in those laser mold$$$ to a smoother shape.
    Or just do it on the proto....

    Cheers.
     
  11. G.R.F
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    G.R.F Junior Member

    Hmm yep that's everyone's concern, ventilating the foil but think about it.

    Upwind, only one side will be in play.

    Offwind I'm hoping to dump the plate up between the hulls, like we do on racing sailboards, then I'll need a little grip from those chines until it comes back on the afte section of the rocker and all that tunnel entry lifts clear.

    Well that's the idea of the three stage rocker.

    We'll see, only one way to really find out.
     

  12. G.R.F
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    G.R.F Junior Member

    There's been a bit more progress, finally married the deck to the hull and it fitted.

    Then we spent saturday deciding on where all the rigging bits will go, pics on the blog at the start of the thread...

    Getting real exciting now..
     
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