Help with small sailboat, sail's area - Beginner

Discussion in 'Boat Design' started by cpodest, Mar 10, 2014.

  1. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 139, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    there is no "perfect" size sail for any given size boat. The equations you have are junk, get that idea out of your head, the idea of it is ridiculous.

    Consider that in very light winds, the larger the sail you have the more speed you will make. But if you have that same very large sail when the wind picks up, it will be uncontrollable and you almost certainly will go for swim. So the "ideal" size for maximum speed is the largest sail you can fly that you can maintain control of the boat, the higher the wind speed, the smaller that "ideal" will be.

    Most lager sailboats deal with this problem by carrying several different size sails, and have a means of reducing the sail area by reefing (lowering it part way and tying up the excess at the bottom to reduce the effective sail area). On larger sailing boats when the conditions change the crew change the sails to match the conditions. This is not very practical in a dingy.

    It is always easier to handle any small boat if it has a small sail, but it will be slow in most conditions, and lose any race against similar boats with larger sails. In strong winds however, when out racing against other boats with larger sails, the other boats will more likely capsize while you can maintain control of your smaller sail and win the race.

    These are the decisions that go into how large the sail should be, not just the size of the boat. If it was intended to be a boat for beginners, than you would design a smaller sail. If you were designing a small fast boat for experienced racers, than you would have a much larger sail on it.

    One thing you might consider, is go with a smaller sail when you build it for learning on. than after you have a season or two on it, and you want to go faster, than design a larger mast and sail for it.

    The best suggestion you got is to compare the size of sails for all the small boats listed on the attachment above. choose smaller size sails from the list for the design of your first boat that you will be learning to sail with.

    Also, I highly recommend a much wider beam. The more beam, the more comfortable you will be in the boat, and the more sail you can comfortably carry. Again, look at similar sized boats from the attachement to get an idea on typical width.

    good luck, and do not over think this too much, you can make any thing work. Sailboats have been around much longer than fancy mathematical formulas, many sail quite well.

    Pick something "about right" and go have fun with it. Post some pictures of what ever you build.
     
  2. peterAustralia
    Joined: Mar 2006
    Posts: 359
    Likes: 23, Points: 18, Legacy Rep: 233
    Location: Melbourne Australia

    peterAustralia Senior Member

    hi carlos

    For a beginner small boat, first up just forget all the calc stuff. Start by looking at general purpose skiffs. Look for something around 13 x 4.5ft which should make a large capable skiff that should go well. Find an existing design, maybe modify it a tiny bit from there. My first guess would be around 70 or 80 sqr feet of sail area. Start with that... and then see how it all goes.

    Generally smaller boats are used more than bigger boats. they are cheaper, easier to move around, easier to cartop, easier to man handle, and are still a fair bit of fun
     
  3. cpodest
    Joined: Mar 2014
    Posts: 32
    Likes: 1, Points: 0, Legacy Rep: 22
    Location: Ilhabela - Brasil

    cpodest The Beginner

    Dear PAR, Dear Petros and Dear Peter,

    Thanks very much for your comments, and really, all opinions are important to me. I really appreciate your help.

    I will take a look at some beginner's dinghy and i will study and try to construct by my self, considering all yours advices. (can you recomendme any flattie?)

    Now, i will take specially atention in a simple sail, with an small area, without a jib, to make my sails learning more pleasent and safe.

    Please, give me a couple of days, maybe on monday, I will present you an scketch in order to have yours comments? (should I make a new thread for that?)

    And PeterAustralia... that is exactly what i'm looking for, a boat, a cheaper, easy to move and easy to handle¡

    Thanks a lot guys¡
    Carlos
     
  4. SukiSolo
    Joined: Dec 2012
    Posts: 1,270
    Likes: 25, Points: 0, Legacy Rep: 271
    Location: Hampshire UK

    SukiSolo Senior Member

    The Optimist is one of the smallest boats but designed for children. Next up and a 2 person boat is probably the Mirror, definitely worth looking at. Perhaps the Graduate but it is too cramped for 3. After that it starts to get to double chine, strip plank or maybe clinker.

    The larger GP14' is I would suggest maybe a bit heavy but a good beginners boat in some ways. She is also a two plank a side boat so relatively simple to build. Sail area is modest and she is stable so would be OK to learn in with reasonable (for a traditional dinghy) performance. The class is International too.

    Bear in mind I am coming from a UK/European perspective and I am well aware of different classes in the US and Oz but the guys there know them better!.

    Fyneboats are worth checking out. The more traditional Drascombe Lugger type too but they may be a bit too long. Hope you find something that gives you a guide, and helps you along.
     
  5. cpodest
    Joined: Mar 2014
    Posts: 32
    Likes: 1, Points: 0, Legacy Rep: 22
    Location: Ilhabela - Brasil

    cpodest The Beginner

    Displacement question

    Dear Phil,
    I was looking some models in sailboat.com (Blue Crab as an example) and I have a question related the features presented for each model. Are these features presented there (like the displacement) including a crew?
    Thanks a lot
    Carlos
     
  6. philSweet
    Joined: May 2008
    Posts: 2,258
    Likes: 150, Points: 63, Legacy Rep: 1082
    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    I wouldn't trust any single dataset on that site. Go to the owners organization or the mfg to confirm numbers you find there. But the site is very handy for getting a feel for the numbers if you look at several boats similar to what you want. It helps to understand how each crew balances the boat. Is the skipper sitting on the rail and the crew using a kickstrap? You should compare boats that are sailed in the same manner. A skiff with 2 in trapezes is going to have different numbers from a similar boat with just a kickstrap for one crew. I-14 compared to Jet 14, for instance. Derived from the same hull, but different crew ambitions.
     
  7. petereng
    Joined: Jan 2008
    Posts: 581
    Likes: 21, Points: 28, Legacy Rep: 252
    Location: Gold Coast Australia

    petereng Senior Member

    Hi Carlos - I think you need to do this on two fronts. If you have access to a small boat start getting your skill up. A laser with a small sail is good. Any small existing boat is good. Won't take much time to get RH and LH to agree!! During this practice you can develop your design. You need to pick a reference boat, something that exists, works and you can get basic statistics on. Then design your boat for what you want it to do not straying too far from the reference for your first time. Once you think your design is done put it away for a couple of weeks go sailing come back and review your design... its amazing how things look good today but look poor given some thinking time. If the design is still good after digestion then go for it!! good Luck Peter s
     
  8. cpodest
    Joined: Mar 2014
    Posts: 32
    Likes: 1, Points: 0, Legacy Rep: 22
    Location: Ilhabela - Brasil

    cpodest The Beginner

    Dinghy from Dinghy.pl

    Dear Friends,

    I decided start to build a 3mts LoA boat from www.dinghy.pl

    I will analize the design ... sail a little and then try to desig a bigger one!

    Thanks a lot for your help

    Carlos
     
  9. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 139, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    those look like excellent designs, good beginner boats. Are you talking about the 3m tender? simple design, but I would consider the 3.8 m dingy instead. It is a bit more complicated to build, but makes a much more useful boat, gives you room to bring a passenger and yet still easy to handle on your own. you will not outgrow it as fast either, it is much more capable boat.
     
  10. cpodest
    Joined: Mar 2014
    Posts: 32
    Likes: 1, Points: 0, Legacy Rep: 22
    Location: Ilhabela - Brasil

    cpodest The Beginner

    Yes, 3mt tender.

    I was considering the "twin dinghies", because they have building plans instead the 3.8 dinghy that has only "study plans", but my experiencience building boat is very to close to zero ... so, i decided to start with one of the simpliest.

    On the other hand, If u take a look at the 3mt tender, look at the plans and you will notice that the daggerboard, is a little bit displaced from the central axis (longitudinal axis).... do u know if it is possible locate it on the axis? I will send an email to the designer to ask

    Thanks a lot for the comments
    Carlos
     
  11. peterAustralia
    Joined: Mar 2006
    Posts: 359
    Likes: 23, Points: 18, Legacy Rep: 233
    Location: Melbourne Australia

    peterAustralia Senior Member

    looks like a quite nice little first boat. i personally would just go with glue, nails and paint, forget the epoxy. i would also go with the vertical mast, not the lateen sail version. have fun
     

  12. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 139, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    I do not see why the dagger board could not be on the center line, it appears there is a wear strip/strake on the bottom he wanted to avoid with the dagger board box. I would not put those strakes on the bottom, it will add to the drag noticeably, but iI would use the next thickness up of plywood for the floor and delete the strakes.
     
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.