22 Foot Racing/Pocket Cruising Sailboat

Discussion in 'Boat Design' started by Ned Lunav, Jun 14, 2019.

  1. Ned Lunav
    Joined: Jun 2019
    Posts: 1
    Likes: 0, Points: 1
    Location: Okanagan Valley BC

    Ned Lunav New Member

    I am relatively new to this forum and joined up because of a recent project I have been working on. About a year ago I began messing about in AutoCAD and eventually came out with what appeared to be a practical and enjoyable boat. This was accelerated when I purchased a 1979 Ranger 22 and, while the boat is great fun, I can't help thinking about everything it isn't.

    The conditions for my design were the following:
    - 22-24 feet LOA (including transom hung rudders)
    - Easily-tended rig with self-tacking jib on a furler and option to fit a genoa for lighter winds
    - Cabin with sitting headroom (something my Ranger sorely lacks)
    - Sleeping for 3-4 people (doesn't need to be extremely comfortable)
    - Table (fixed folding or movable)
    - Centerline retractable bowsprit
    - An easy way to get the spinnaker up/down short handed such as furling or a dousing tube/bag (used to race on the foredeck and not eager to repeat the experience of dragging down a kite in 20+knots)
    - Wide open cockpit (no traveller to bisect it) for 6 people for day sailing
    - Open transom, single or twin rudders
    - Retractable keel for trailering
    - Single or double trapeze setup (unorthodox for a keelboat, but allows for greater sail-carrying potential with a smaller keel bulb and a lower displacement)
    -Planing hull

    While I have been trying to get my hands on Rhino, the best I have right now is Autodesk Inventor. I have spent about a week modelling the boat in Inventor (kind of new to the program) and have come out with a somewhat acceptable result. Having 3D printed a 1/24th scale model, I have discovered that the model is somewhat flawed. In my pursuit of a planing hull shape, I have instead ended up with what amounts to a massive flat section of the hull running from about three feet behind the bow to the stern. I suspect that this is more a reflection of my incompetence when it comes to modelling than anything else. The diturbing part is that this resulted in two very sharp corners in the aft corners of the hull, sort of like flat bottomed aluminium power boats. While this allows them to achieve the planing affect, I very much doubt it would work when applied in my case. The hard chines I had baked into my design for stability mysteriously disappeared and the bow now curves down from about half way up, interrupting my planned vertical bow. This actually looks very good in person, but is probably catastrophic as far as the actual hull shape is concerned.

    I guess the real reason I'm here is that I want to know where to go from here. I keep chipping away and refining it every chance I get, but I would like some advice on how to proceed. I would like to construct a larger model (upwards of 4 feet long) in order to test the hull itself but am in the dark about how to go about doing it. Thanks for any assistance.
     
  2. rwatson
    Joined: Aug 2007
    Posts: 5,773
    Likes: 263, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    It sounds like a fun project.
    From my experience, you are just encountering the first of a long series of problems.
    It took me three months with Rhino to be able to produce fair and contiguous boat lines at will. Buying Rhino and getting stuck into the tutorials was worth every minute. It's a skill that just gives and gives. $1500 is worth every penny.

    Once you get good at CAD, then you can start thinking about the hull and interior design, rib and stringer placement, accommodation sizing, etc..
    Then there is buoyancy, centers of effort, performance considerations, including righting moments, sail size and placement, keel location and size, etc etc. to get into. Then you are going to face the engineering and structural sciences so you can create a safe, insurable craft.

    When you get to actual scale models, I can tell you from personal experience the best way to go.
    The 1:5 scale model I built was for a 28 footer, so pretty close.

    The ONLY way to build a model that will scale to the correct weight is a strong lightweight shell. You can't use sheets of solid fiberglass, no matter how thin.
    Balsa is OK, but it's not waterproof, and only comes in narrow timbers.

    I had much better success with 3mm dense structural foam. The cost is negligible for the accuracy and ease of build. When you get it assembled, just light glassing on both sides will create a very stiff, easily modifiable, waterproof shell.
    PVC foam Density 80 kg/m³ SCRIM-SLOT 3 mm x 0.99186 https://www.castrocompositesshop.com/gb/sandwich-core-materials/1379-pvc-foam-density-80-kgm-scrim-slot-3-mm-x-099186.html
    Foam.png

    see

    Fast Build Scale Model https://www.boatdesign.net/threads/fast-build-scale-model.40905/page-3

    for some inspiration.

    render.png

    rpg.png

    Have fun.
     
  3. Pammie
    Joined: Dec 2015
    Posts: 106
    Likes: 13, Points: 18, Legacy Rep: 10
    Location: Eindhoven, Netherlands

    Pammie Senior Member

    Ilan Voyager likes this.
  4. tpenfield
    Joined: Dec 2016
    Posts: 170
    Likes: 11, Points: 18, Legacy Rep: 10
    Location: Cape Cod, MA

    tpenfield Senior Member

    Sounds like an interesting project. I'm subscribing in for the ride.

    Got any pictures to post from your CAD modeling or the 3D model? I have often wondered how a stepped hull towards the aft section might offer a sailboat planing ability, so I'll throw that out there for consideration.

    Do you plan on a fully lifting keel ( like an S2 7.9) or more of a swing keel (like a Mariner 19 or Catalina 22)?
     
    Last edited: Jun 14, 2019
  5. Ilan Voyager
    Joined: May 2004
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    Location: Cancun Mexico

    Ilan Voyager Senior Member

    I do agree totally. The Dix mini is a nice little beast.
    The mini have been existing since more than 30 years, and a lot of experience has been accumulated.
    There are several plans as the 6.5 m mini is a pretty active class with an oceanic race (the Mini Transat) where a lot of good skippers have made their debut. There are plans less extreme and more cruising oriented. There are plenty of used boats in France; as the class is popular.
    Instead wasting my time trying to design a 22 feet without having the knowledge and the experience, I would build one basic simple mini from plans of an experienced NA and rather spend some time learning to tame these little monsters.
    It's great, great fun. Experience of dinghies like the 420, 470 and 505 is pretty helpful, and rather cheap to acquire being member of a club.
    And when you have learnt, that is the result...
     
    Last edited: Jun 14, 2019
  6. Ilan Voyager
    Joined: May 2004
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    Location: Cancun Mexico

    Ilan Voyager Senior Member

    That shows the potential and nice details of the hardware.
     
  7. Ilan Voyager
    Joined: May 2004
    Posts: 1,177
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    Location: Cancun Mexico

    Ilan Voyager Senior Member

    Last tendencies in mini design. In French but the images are very talkative... Look at the new scow bows.
    That redefines totally the hull, so you can get an isocarene hull, which stays symmetric even heeling with the keel and rudder aligned.
    Note also the volume of the hulls...
     
  8. Dolfiman
    Joined: Aug 2017
    Posts: 798
    Likes: 370, Points: 63
    Location: NICE (France)

    Dolfiman Senior Member

    Seascape 24, now called First 24 since Seascape joined the Beneteau group, is a good example of the last trends in that size and seems close to your specifications : a real cabin to sit in, a wide large cockpit, lifting keel, planning ability, a beam limited to 2,50 m so for tra le ring with a usual driving license, ... by a reknown architect Sam Manuard. Can inspire you for your project :
    First 24 | BENETEAU https://www.beneteau.com/fr/first/first-24
     
  9. lenm
    Joined: Dec 2014
    Posts: 21
    Likes: 3, Points: 3, Legacy Rep: 10
    Location: australia

    lenm Junior Member

    Hi Ned, i presume your final goal to personally build a full size prototype?
    Im with Dolfiman - check out the seascape 24 and sea trial videos. Pricewise, they seem great value.
    I am currently building a 24foot boat and it is ALOT of work (3 years to date). Personally i would be a bit shy about building anything other than a tried and proven design. There is just too much at stake (cost and time). Esp a sailing boat where there a lot of physics at play.
    I think a good boat (performance) comes from a combination of good navel architecture design in conjunction with trial and error and followup refinement.
    If performance is not too important to you then by all means keep persuing your project - it sounds like fun.
     
    rwatson likes this.
  10. Ilan Voyager
    Joined: May 2004
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    Location: Cancun Mexico

    Ilan Voyager Senior Member

    The last tendency in monohulls. Good base for a less extreme cruiser-racer

    The pics are about a 40 feet racer
    [​IMG]
    [​IMG]

    [​IMG]

    In reality the new is pretty old: scows, avery interesting sail boat type

     
  11. Ilan Voyager
    Joined: May 2004
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    Location: Cancun Mexico

    Ilan Voyager Senior Member

    The boat winner of the 2017 mini transat in "normal boats" a pogo-3,
    Pogo 3 (jauge série Mini) 6,50 m 920 kg 2015 NA Guillaume Verdier
     
  12. Ilan Voyager
    Joined: May 2004
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    Location: Cancun Mexico

    Ilan Voyager Senior Member

    Look at the difference with the winner in prototypes the very fast beast

     
  13. Ilan Voyager
    Joined: May 2004
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    Location: Cancun Mexico

    Ilan Voyager Senior Member

    Audio of no great interest but plenty of pics. That would give a very interesting cruiser.

     
  14. Ilan Voyager
    Joined: May 2004
    Posts: 1,177
    Likes: 96, Points: 48, Legacy Rep: 758
    Location: Cancun Mexico

    Ilan Voyager Senior Member


  15. lenm
    Joined: Dec 2014
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    Likes: 3, Points: 3, Legacy Rep: 10
    Location: australia

    lenm Junior Member

    I dont want to hijack Neds original post - but are you aware of anyone doing/selling plans for one of these modern scow design hulls??
    I recon a 24 foot scow with a 'trailerable' beam (2.5m) would make a good cruiser/racer. Would also have some more accommodation room up front with the scow nose (e.g double berth).
     
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