New Design for a 17' Daysailer/Racer

Discussion in 'Sailboats' started by Cleve Motley, Oct 31, 2004.

  1. brett
    Joined: Nov 2004
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    Location: Australia

    brett New Member

    Here is a roughie I just knocked up. I used a form of another boat I built scaled and teased a little. Plenty wrong with it at this point but you get the idea. I don't plan on doing anymore with it unless somebody decides to pay me. Afterall I'm entitled to make a living...:)

    Being in the camp that has already designed, built and owned a sportsboat, I'm in the Kiss crowd. Big sails, Clean and simple layout and less mistakes. ***. Pole hidden under the deck through the centreline. The only canting equipment on the boat. I personally wouldn't rule out Traps on this.

    Brett
    PS Tas. AMC. (assuming?)
     

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  2. TaSSie_deVil
    Joined: Jan 2004
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    Location: Launceston, Tasmania, AUS

    TaSSie_deVil Resident Boataholic

    Brett,

    Not bad at all for a quick rescaling job. I can see a few similarities between my design and yours; namely the flared side decks, generally KISS arrangement (ignoring the canting keel idea), somewhat dinghy-like profile etc.

    You assumed correctly, I do go to the AMC... hence the name.

    Cheers,
    T
     
  3. brett
    Joined: Nov 2004
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    Location: Australia

    brett New Member

    Was there myself a few years back...
     
  4. Doug Lord

    Doug Lord Guest

    Kiss /p17

    KISS is a really good idea when it is applied properly.For instance, using a self tending jib on this boat is important. Maximizing RM created by the two crew(who don't want trapezes) by providing maximum width carbon racks with seat backs for comfort is another simple idea when considering only two people handling a 17-18' high performance keelboat. A spin trough ahead of the forestay for ease of spin launching is a simple solution to better handling. A squarehead main could be a simple solution to improving gust response w/o a complicated rig.
    But taking away at least 1/3rd of the potential RM of this boat in the name of simplicity is a false economy sentencing the hapless owner and one crew to many lackluster days on the water carrying around lead that is not paying it's own way. 33%!!!!!
     
  5. Paul B

    Paul B Previous Member

    Really nice. Really, really nice. Not a scaled down K6, but I think it is a better type.

    Of course you should expect payment for doing real work. However, I know many design offices "knock up" just this sort of thing quite often to show what they can do, with no particular client hooked. I doubt it pays off more than rarely. It is nice to see how people approach various problems. There's one office in the UK who has a website that shows a lot of proposals, maybe 5 to 10x the number of designs actually built. It is entertaining to look at.

    Care to share what software you used to do this?

    Now if only the non-KISS expert will stop posting the same platitudes over and over, and will actually address the real engineering problems with his proposal, maybe some of the KISS group might be swayed.

    Or not.
     
  6. BrettM
    Joined: Apr 2002
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    Location: Australia

    BrettM Senior Member

    Never Seen a k6 here in OZ so no influences there. I did have a quick look on the net though.

    It always make me laugh when I see a web site of some designer that has many impressive rendered images passed off as completed designs but no photos of actual boats. I believe that the only reason one would do this is if you don't have any work.

    Hull was done in Maxsurf then transfered to Rhino for the cockpit and deck. Quickly Rendered using the standard Rhino render engine.

    As for the RM's of different systems I might (if I have time) run some numbers on the above hull to see how some of the claims in this thread might stack up.

    Brett
     
  7. 249

    249 Guest

    All of this bunch are very nice boats. Congratulations all.

    Tassie Devil, I can't claim to be a designer but one thing about your hull - would the sharp chines aft be a problem when heeled? I mean it's not a dinghy, so she must heel and that heel will turn your flat U-shape into a Vee shape (more wsa, less dynamic lift etc) won't it? Isn't that why Rockets and Thompsons have very rounded sections, which turn elliptical or curved with heel? Even downwind today you're heeled under assy if there's any breeze, aren't you?

    Hey Doug, the canter could be fun, but it's like having dirty big racks or a big genoa - some people like them for the extra pace, others don't like the hassle. You can be innovative and not be into canting keels; for example, I haven't got much interest in them because if I want a fast boat I don't want ANY lead.....
     
  8. Doug Lord

    Doug Lord Guest

    P17-no hassle

    249, seems to me that a canting keel designed and installed properly should not be a "hassle"
    in any way. It's thirty year old technology for crying out loud! This is a relatively new application and does require the use of new technology(kFOIL or fixed wings) but the result is a fairly high performance ,reliable, easy to sail boat perfectly suited to just two people-and I want one......!
     
  9. BrettM
    Joined: Apr 2002
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    Location: Australia

    BrettM Senior Member

    OK, I ran some numbers on the hull (using Hydromax)posted in the above pics. I came up with conditions that I believe are reasonable estimates and carried these through the entire analysis. For camparative purposes the basic boat weight/vcg has remained constant except for the crew a,d bulb positions.

    I have simplified the report to save me some time. For those who don't know, multiplying the GZ values with displacements will give the RM value. Area 0-30 is the area under the GZ curve to 30 deg and is effectively the righting energy across the sailing range.

    Principal Particulars
    LOA 5.5m
    Beam OA 2.2
    Beam WL 1.3 (Approx)

    Lightship (Unballasted) 200 kg 0.4m above base
    100 kgBulb 1.5m below base
    2 persons & effects @ 90 kg VCG 1.0m , TCG 1.2m (on gunwale)
    Total Displacement 480 kg
    LCG was adjusted to give a reasonable initial trim.

    Standard Condition as above
    GZ0 0.450
    GZ30 0.699
    Gzmax 0.747 @ 42.3 DEG
    Area 0-30 18.095 MDEG

    Canted Keel Condition ie bulb moved 55 deg to TCG 1.23m VCG –0.86
    GZ0 0.706
    GZ30 0.853
    Gzmax 0.859 @ 36.1 DEG
    Area 0-30 20.689 MDEG

    Standard Condition, crew moved outwards 1m on trapezes
    GZ0 0.825
    GZ30 1.022
    Gzmax 1.034 @ 36.8 DEG
    Area 0-30 28.829 MDEG



    Standard Condition as above but with 3 crew
    Total displacement 570 kg
    GZ0 0.568
    GZ30 0.740
    Gzmax 0.759 @ 42.3 DEG
    Area 0-30 20.409 MDEG

    To get RM you need to multiply GZ x displacement ie 480 kg for the 2 person conditions and 570 for the 3 person.


    Have Fun!
    Brett

    edited, 3 person RM 0=30 (oops didn't change the value from the 2 person value)
     
  10. Doug Lord

    Doug Lord Guest

    P17

    Thanks Brett! Seems a canting keel adds a whole lot of power to carry sail compared to the two person fixed keel and it seems it would pay to keep it relatively flat maybe 15-20 degrees..
     
  11. BrettM
    Joined: Apr 2002
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    Location: Australia

    BrettM Senior Member

    Principal Particulars
    LOA 5.5m
    Beam OA 2.2
    Beam WL 1.3 (Approx)

    Lightship (Unballasted) 200 kg 0.4m above base
    100 kgBulb 1.5m below base
    2 persons & effects @ 90 kg VCG 1.0m , TCG 1.2m (on gunwale)
    Total Displacement 480 kg

    Standard Condition as above
    GZ0 0.450
    GZ30 0.751
    Gzmax 0.814 @ 43 DEG
    Area 0-30 18.928 MDEG

    Canted Keel Condition ie bulb moved 55 deg to TCG 1.23m VCG –0.86
    GZ0 0.706
    GZ30 0.905
    Gzmax 0.921 @ 37 DEG
    Area 0-30 25.238 MDEG

    Standard Condition - 1 crew moved outwards 1m on trapezes
    GZ0 0.638
    GZ30 0.913
    Gzmax .953 @ 38 DEG
    Area 0-30 24.297 MDEG


    Standard Condition - 2 crew moved outwards 1m on trapezes
    GZ0 0.825
    GZ30 1.075
    Gzmax 1.097 @ 38 DEG
    Area 0-30 29.666 MDEG

    Standard Condition – with 2 crew on wings Max beam now 3.5m
    GZ0 0.694
    GZ30 0.961
    Gzmax .995 @ 40 DEG
    Area 0-30 25.907 MDEG



    Standard Condition as above but with 3 crew
    GZ0 0.568
    GZ30 0.794
    Gzmax 0.820 @ 38 DEG
    Area 0-30 21.235 MDEG

    To get RM you need to multiply GZ x displacement ie 480 kg for the 2 person conditions and 570 for the 3 person.

    Sorry I had to repost all this but I discovers a typo in my load conditions. All fixed now. Most numbers went up.

    I think that this shows that the addition of a canting keel over a fixed one increases the GZ curve to approximately that that would be achieved by having one crew member on a trapeze. The canting Keel is slightly better in this respect than the addition of a third crew.

    It is however not quite so good as the addition of wings/racks to and overall beam of 3.5m and is far behind the 2 person trapeze configuration.

    In my opinion and using the facts above, a canting keel is not a cost effective or user friendly option (for this size yacht) against the additions of wings or a single trapeze.

    If it were my boat twin trapezes and no lead in the keel would make it fly - but that's become a dinghy:)

    Brett
     
  12. Doug Lord

    Doug Lord Guest

    P17-focus

    Thanks for your work ,Brett. The facts show clearly that if you don't have a trapeze("customer" doesn't want one or two) and if your max beam is limited to around 8' the canting keel gives close to the RM of a three person boat at a substantially lighter weight and with JUST TWO PEOPLE! As I estimated in a previous post this extra power may cost around $1500US over the fixed keel but it meets the specs pretty well-and for me personally it would be well worth it. (of course the racks on my boat would have seat backs!-high comfort quotient)
    With a properly designed system you have an easy to sail two person keelboat with a reliable ,quick, robust, retracting canting keel that doesn't talk back ,always shows up on time and takes minimal maintainance.And more than likely faster than any existing keelboat in ths size range.
     
  13. BrettM
    Joined: Apr 2002
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    Location: Australia

    BrettM Senior Member

    Doug,

    What Customer? Have you taken a deposit for something? Perhaps you want to share some drawings/numbers of your design?

    The numbers I put up show that if you start with a basic setup and decide that you want some more power, then a single trapeze, canting keel or an additional person will give approximately the same increase in RM. Bang for buck, the single trapeze is obviously at the top of the pile. Add a 2nd trapeze and you add a lot more.

    On this size range boat, where the bulb weight in near to that of a moveable crew member it it simply does not pay its way. On a larger yacht or perhaps a radio controlled "toy" the tables are probably turned.

    Unless one has a predetermined mindset, financial interest or loads of money to waste it is the wrong choice/reccomendation in this instance - period.

    I sail a high performance sports yacht and can not see how it is such a good idea. I'm not biased, I'm merely selling fact. I'll let some others jump in and comment.

    Brett
     
  14. Doug Lord

    Doug Lord Guest

    P17

    Brett, read the first post: the "customer" does not want any trapezes-not one, not two not any nor does he want a third crew-just two.
    Hands down the canting keel fits the bill better than any other solution with those restrictions; your figures prove it irrefutably.
    If you want to ignore the "customer's" restrictions then a foiling two person boat scaled up from a Moth might be best or an Aussie 18 or any number of currently available dinghies-BUT THAT IS NOT WHAT THE CUSTOMER WANTED.
    And as I've said before this concept with a canting keel fills the bill perfectly-and as best as I can tell there is nothing like it on the market currently.
    I love the concept-a two person boat with unmatched comfort and unmatched performance among keelboats in this size range.Easy to handle and big enough to take a couple of friends for a day sail.It's an exciting idea that would open up performance keelboat saling and racing to more people than ever before!
     

  15. BrettM
    Joined: Apr 2002
    Posts: 204
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    Location: Australia

    BrettM Senior Member

    Doug.
    Can you please highlight the relevant sections in the first post saying that traps are out and canting keels are in? I do see a part about two crew members though so I'll give you that.

    I do see cleve entertaining the idea a little later but only after your speech about how good your canting KFOil system is.
     
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