Opinions on this newbie amateur daysailer

Discussion in 'Boat Design' started by Murdock, Oct 20, 2006.

  1. Murdock
    Joined: Aug 2006
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    Murdock Junior Member

    I'm an amateur sailor willing to build my first boat.
    As thinking on my dream daysailer, have seen lots of photos over the net, and still no one convinces me completely, so, got some freeship & cad stuff, and ended with this.
    2 handed daysailer:
    LOA 4.60 mts (14')
    Beam 1.40 mts (4' 9")
    Displ 0.187
    thinking on a 7 mts mast, mainsail + guenoa, even an assymetrical if worth the pain. no foiling (at least now, maybe later...)

    would like some opinions on it
    thanks a lot
    Murdock Stevens
     

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  2. Tim B
    Joined: Jan 2003
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    Tim B Senior Member

    You have to ask yourself what you want from a Daysailor.

    My requirements may be very different to yours. I know a lot of people sail Wayfarer dinghies as daysailors, and they're very good for it. They can take a lot of abuse, they're very weight tolerant and are as stable as anything.

    Personally I wanted something with a bit more performance. I decided to buy a LARK, a 1970s racing boat. It's performance is impressive, if not quite up to modern standards, but it has the benefit of being built strong, and having lots of storage under the foredeck. Therefore, I can take the tent, a sleeping bag and change of clothes, and go off somewhere for a weekend, or I can take the kit out and just go out sailing.

    There are a lot of good boats around. It is well worth looking at them, if only for inspiration.

    Anyway, your design:
    The bow looks ok, but be careful about freeboard with an entry that fine.
    Further aft, chined hulls are fine, but tend to be less forgiving than round-bilge hulls in handling.
    Centreboard, Lifting? how? rotating? space, centreboard case etc. Tapered boards don't lift nicely
    Aft, the cockpit doesn't look to have enough space for the structure between inner and outer skins. Look at the Phantom, RS range, International 14s etc. for inspiration.
    The rudder is way too small, you could increase the size quite easily. Perhaps 60% of the keel span and 60% of the keel root chord.

    Other than that, it looks good. The general styling is nice.

    Cheers,

    Tim B.
     
  3. Murdock
    Joined: Aug 2006
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    Murdock Junior Member

    Thanks for your answer.

    - Centreboard, Lifting? yes, some kind of NACA profile, lifting style.
    - Further aft, chined hulls are fine, but tend to be less forgiving than round-bilge hulls in handling.
    Lot of photos I've seen all over lead me to the conclusion that more & more moths and foilers are used to this kind of "angled" hulls instead of round bilged, just was a design choice.
    - Aft, the cockpit doesn't look to have enough space for the structure between inner and outer skins...
    Attached some framing & structural scheme, thinking on 11 frames about 40cm between each,
    strenght will be given by form (resin made w/ vacuum infused 2 #600 roving and something else).
    I preformed some preliminary calculations at about 35º heel angle, with 200kg (380lbs) loading and think can handle it.
    As of my preliminary calculations, hul will weight about 80/85kg.
    thanks again
    Murdock
     

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  4. tom28571
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    tom28571 Senior Member

    I 14's have been through 70 0r s0 years of evolution. You need to wonder if you can just immediately do something better. Maybe that is not your goal anyway but, just like many of us, you want to get your two cents into the game.

    It's a nice looking boat and a worthwhile exercise but its hard to tell a lot about its potential. I agree with most of what has been said. In addition, to the rudder being small, the daggerboard looks huge. Such a big high aspect DB will generate a lot of heeling moment. Unless you can offset it with a trapeze, the overall performance might be better with a lower aspect. A db such as you have drawn will give too much interference with the main boom to allow it to be raised for offwind and/or planing conditions and while down will reduce planing potential. I'd rather have a slightly less efficient centerboard than deal with daggerboard problems and I have mostly raced daggerboards.

    I know I'm in the minority currently, but I like transoms except in high performance racers that expect to be swamped regularly.
     
  5. Tim B
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    Tim B Senior Member

    Sounds like you've thought of most things. Remember that sailing dinghies will often work at thier maximum righting condition. Also think of what materials you're going to use. Carbon and clever moulding techniques may be the method of choice, but it may only be slightly more practicle than pre-preg if you're going to build it in a garage.

    You also need to think about the rig loading (mast step, forestay, cainplates etc.) and the longitudinal and tortional stiffness of the vessel. There are few rules that will help you for a vessel less than 6m, so if you want to do an in-depth structural analysis it will take a lot of time and effort.

    I agree with Tom or the transom point, they are rather nice to have when you encounter a quartering wave system that is almost as high as the freeboard.

    Tim B.
     
  6. Tim B
    Joined: Jan 2003
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    Tim B Senior Member

    Sounds like you've thought of most things. Remember that sailing dinghies will often work at thier maximum righting condition. Also think of what materials you're going to use. Carbon and clever moulding techniques may be the method of choice, but it may only be slightly more practicle than pre-preg if you're going to build it in a garage.

    You also need to think about the rig loading (mast step, forestay, cainplates etc.) and the longitudinal and tortional stiffness of the vessel. There are few rules that will help you for a vessel less than 6m, so if you want to do an in-depth structural analysis it will take a lot of time and effort.

    I agree with Tom or the transom point, they are rather nice to have when you encounter a quartering wave system that is almost as high as the freeboard.

    Tim B.
     
  7. Murdock
    Joined: Aug 2006
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    Murdock Junior Member

    Ok, got the message,

    - You also need to think about the rig loading (mast step, forestay, chainplates etc.) and the longitudinal and tortional stiffness of the vessel. There are few rules that will help you for a vessel less than 6m, so if you want to do an in-depth structural analysis it will take a lot of time and effort.
    I beg your pardon, I'm not a NA, but as a civil engineer have been involved in deep & weird calculations almost all my life, doesn't scare me....
    also I've been sailing since my first opti to my actual pair of laser's...

    one more pic on my favour: seen this photo over the net, seems quite similar or not?
    someone knows what kind of boat is? where to find adittional info about?
    thanks
    Murdock
     

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  8. Raggi_Thor
    Joined: Jan 2004
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    Raggi_Thor Nav.arch/Designer/Builder

    Looks great!
    I am wondering about the displacement, 187kg, does that mean that with two sailors at 75kg each the whole boat with rigging and sails is only 37kg?
    Is that possible?

    I also wonder if concave sections in the forefoot is good, but I don't know, just a question. Anyone with experience on this?
     
  9. Tim B
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    Tim B Senior Member

    Murdock, I'm not trying to pour cold water on your idea, but it pays to make sure it's right at this stage, otherwise you spend a lot of time building something that doesn't work properly.

    Tim B.
     
  10. wet feet
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    wet feet Senior Member

    You are much further ahead with learning Freeship than I have managed so far.Could you show us a profile of the boat with the planned rig in place?The reason for this is to get an idea about the dagger board location.It does seem a long way forward.Additionally,there appears to be something of a pinched look to the lower part of the bow sections which might not help with lifting onto a plane.
    As others have mentioned,the rudder seems small and the structure to support it has obviously not been finalised.Please keep in mind that if the boat gets built you will need to consider attaching the fittings and this may necessitate inspection hatches to allow nuts to be placed on bolts.Inspection hatches need to be fitted to flat surfaces.
     
  11. Figgy
    Joined: Feb 2006
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    Figgy Senior Member

    Heres my two cents..
    Keel- swept only 5 deg. and move it farther aft, thin it up too.
    Rudder- Cassette style, nice. Simple is good. Go deaper tho'.
    Really its one or the other. Big rudder, small keel and vice versa.
    All depends on how it responds. You wont know really
    know 'till you sail one. Give the lowest part a quarter circle arc.
    Rig- Think "A-cat", maby Moth
    Simplify const., make the deck one solid piece.
    Other than that..it's great!
     

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  12. Murdock
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    Murdock Junior Member

    Raggi_Thor:
    187kg, does that mean that with two sailors at 75kg each the whole boat with rigging and sails is only 37kg?
    As calculated, it will displace 0.187m3 of salty water @1.025 = 191kg
    2 guys between 75 and 100kg = (let's be generous) 200kg + hull weight = 85kg makes a total weight of 285kg.

    wet feet:
    Could you show us a profile of the boat with the planned rig in place?
    maybe you're right, the db location will move a bit aft..
    Still working on it, on first stage, a 7 mts height mast, aluminium 90s type, some wiring (forestay + the rest)
    mainsail 6.50/8.00m2 + guenoa 2.50/3.50m2, even an assymetrical, still not calculated how much the hull will handle.
    posting some more info about hull.
    again, thanks a lot for your patience.
    Murdock
     

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  13. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    I still think it looks good :)
    But the proof of the pudding is in the eating.
     
  14. Murdock
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    Murdock Junior Member

    hello, here is the rig (first approach)
    got a question, searching through specs of similar sized daysailers on the net, there is a tendency for increasing sail sizes (surely for performance), but what about the righting moment? trapeze is not anymore a luxury device, it's a need or I'm wrong?
    at first sight, [main 11.00m2 + guenoa 5.70m2] seems to be too much for this hull on a 15knot breeze?
    Murdock
     

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  15. Raggi_Thor
    Joined: Jan 2004
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    Raggi_Thor Nav.arch/Designer/Builder

    That's pretty much for such a small boat.

    I think many light boats with large mainsails have carbon spars with rather soft mast tops, that's only a guess.
     
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