Learning boatdesign. Can u have a look at "my" boat?

Discussion in 'Boat Design' started by sailingdaniel, Aug 6, 2011.

  1. sailingdaniel
    Joined: Apr 2011
    Posts: 50
    Likes: 2, Points: 0, Legacy Rep: 20
    Location: around the world

    sailingdaniel Junior Member

    Hello everyone..
    Here is a boat that im working on now while im learning about boatdesign.. I would be wery interesting (maybe scary) to here what u think. Whats good/bad? what works and what doesent? Any thoughts ?

    It’s a long boat , some would say narrow. The ide is to have an easy driven passagemaking boat. A little bit under rigged whit potensial to go fast when its blowing. The transom is 7 cm under water..I have added two pics.

    The 3d pic looks a little bit ruff . Im just learning 3d and its hard.. but I should give a picture of the shape.
    I read about shapes of the sectional area curve whit out getting any smarter. It should “look good” i read. Does it look good?  ?? The three curves and wl in the pdf are at 0 , 15 and 25 degree of heel. The cirkels are the Cf at 0 and 15 degree and the line is LCB. The 2 lower waterlines are wrong in the aft end..

    Here are some of the numbers..

    Lenth 16.1 m
    Max beam 3.75m
    Wll 16m
    Max beam wl 3.23m
    Disp 13 ton , metric
    Tc 0.55m l/tc 29 ,sounds a bit extreme to me ???
    LDR/DLR 6.8/ ca 90
    l/b @ wl 4.95
    wetted surface area 49 m2 ( whit 9 m2 in keel rudder, might be optimistic? )
    sa/sw measured: 2.05 real whit 100% jib and roach an main: 2.45
    SAD measured: 18.2 real: 21.8
    Cp 0.61 Aft around 0.68 and forward 0.53 if i understand it right…
    Lcb 54 % from forward end of wl
    Cf 56% @ 0 degree heel and 54.5% @ 15 degree heel, from forward wl
    Dellenbaugh angel: 9 degrees. Just outside “stiff” in the book principals of yacht design. (that is if I can get the vcg 7 cm above wl)
    S# ca 5 “hot” cruiser/racer
    SA 100 m2 , real 120m2 . low aspect ratio rig whit the head stay at 22 degrees angel from the mast.. 70m2 big roach main and 50 m2 100% jib..

    Im thankful for any comments , ides etc..
    Daniel
     

    Attached Files:

    1 person likes this.
  2. river runner
    Joined: Jul 2011
    Posts: 172
    Likes: 6, Points: 0, Legacy Rep: 91
    Location: Colorado

    river runner baker

    I'm not a naval architect and have only designed one boat myself, or only one that is likely to ever get built, and it isn't as complicated a design as a sailboat, but I've been reading articles on sailboat design for decades and own a copy of Skene's Elements of Yacht design, which I've studied. But here are my two cents. It looks very cool, but to my eyes it looks more racer than passage maker. I'd be inclined to soften the curve of the bilge a bit, make the bottom less flat and give it a bit of flare abover the waterline for reserve boyancy.
     
  3. gonzo
    Joined: Aug 2002
    Posts: 14,463
    Likes: 644, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    I think it is a typical generic shape that you get with software. There are no appendages on the drawing. They have a major influence on behavior. The hull is also typical of the downwind racing types that are in vogue today. As a passagemaker, it is unwieldy and of unconfortable motion. Balanced ends have much better handline and seakindliness. The latter is, in my opinion, the most important. Do you have experience in offshore sailing, particularly in rough weather?
     
  4. sailingdaniel
    Joined: Apr 2011
    Posts: 50
    Likes: 2, Points: 0, Legacy Rep: 20
    Location: around the world

    sailingdaniel Junior Member

    Thanks for your input river runner..

    Maybe i confused u when writing "passage maker" , that can sound like a sturdy colin archer boat.. I want it to be fast but whit out having a "racing" big rig..

    Reserve boyancy: for and aft that should be ok whit such a long boat , long lever arm? I dont know if that was what u meant..

    I find it hard to get rounder shape and keep the Cp up . But i think that the hull is very shallow.. But maybe i have let the Cp guide me to much..

    What do u think of the "shape" of the curve of area ?
    And is the sa/sw to low , will it be slow in light winds?
    And the other ratios and number ? do the "match" ?

    Im glad u think its cool.. Many other cruisers thing its "but ugly" :)

    Cheers
     
  5. sailingdaniel
    Joined: Apr 2011
    Posts: 50
    Likes: 2, Points: 0, Legacy Rep: 20
    Location: around the world

    sailingdaniel Junior Member

    Gonzo.. Just just saw youre reply now..

    The lines are mad in Autocad, same prinsip as when drawing by hand..

    Whit balaced ends do u meen duble ender? I dont want that. The lines are balaced if u think of curve of area. And the heeled hull sidetracks only 1 degree per 10 degrees of heel.. thats not so much i think..

    I have some sailing experience , and i have been in bat weather..

    thanks
     
  6. sailingdaniel
    Joined: Apr 2011
    Posts: 50
    Likes: 2, Points: 0, Legacy Rep: 20
    Location: around the world

    sailingdaniel Junior Member

    My sailing skill is better than my spelling!!! :)
     
  7. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 98, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    I agree about it being a generic modern shape. The computer programs and also most designers are deeply influenced by racing fashion and many good cruising attributes are lost in the process of going faster, and looking hip and modern in the berth while drinking in the yacht club bar.
    This is one type of hull among many, and not necessarily the best for the job. A sailing yacht using racing technology is quite expensive per pound compared to simpler, older style rigs.
    Personally I don't like sailing the modern type off the wind as it generally takes too much attention and sail changing since she is dependent on the light sails to move. Workboats rarely carry light sails and consequently have a large working rig which is easily reefed instead. For long distance cruising, easy steering and motion are very important, more so than pure speed. This usually means a longer keel and more weight.
    A friend was on a similar type to the drawing racing to Hawaii with the big chute up at 2 am when they were suddenly knocked down, the lee bow went under, the boat did a 360, scooping up a lot of water in the companionway, then the spinnaker filled again and she went back to her course like nothing happened, except the two feet of water below. Helmsman fell asleep...
    I don't like adrenaline sailing, but much prefer lounging in a hammock while a well-designed traditional type steers herself downwind at slightly lesser speeds.
     

    Attached Files:

  8. sailingdaniel
    Joined: Apr 2011
    Posts: 50
    Likes: 2, Points: 0, Legacy Rep: 20
    Location: around the world

    sailingdaniel Junior Member

    Thanks BATAAN.

    Im not sure what generic means.. But its not "what type of boat is best" im interested in. Anyone can sail/design what ever they want. som like motorboat , some sailboat and some like kajaks ore catamarans , and that is ok...
    Its more comments on the boat i have shown i after.. like , is the lcb in the right place? Is the Cp right for a boat like this? Is the sail area to big ore small? Does the curve of area look ok? Are the differen ratios good for this type of boat? etc.. Any constructive arguments is very welcome..

    I mostly been loocking in "principal of yacht design" , but most of the ration are far away from the norm so i so i wonder if i have done it "right" Mabybe the book was not written for long slender hulls like this?

    Cheers
     
  9. sailingdaniel
    Joined: Apr 2011
    Posts: 50
    Likes: 2, Points: 0, Legacy Rep: 20
    Location: around the world

    sailingdaniel Junior Member

    most of the ratios are far away ( im typing in darkness)
     
  10. BATAAN
    Joined: Apr 2010
    Posts: 1,614
    Likes: 98, Points: 0, Legacy Rep: 1151
    Location: USA

    BATAAN Senior Member

    You will design a successful boat I am sure.
    Beware of too much theory from any one book or computer program, and try to test your ideas with other people's design procedures, and physical models if possible. Pick someone else's similar design you really like and analyze it to educate yourself.
    A boat is such a large investment that one wants to make double-perfect sure of everything possible before proceeding.
    Read Herreshoff, Weston Farmer, Skene's for starters. Boats are simple and infinitely complex at the same time since they function in chaos theory at the water/air interface and are subject to many energies.
    You have a smooth set of lines there, and you might make a sailing model to mess around with and learn more.
    Weston Farmer (book: FROM MY OLD BOAT SHOP) has a very simple method for floatational models to verify drawings and calculations. Though not widely used today, the system has revealed many subtle things about designs that looked perfect on paper, but would have failed in practice due to "oversights".
     
  11. river runner
    Joined: Jul 2011
    Posts: 172
    Likes: 6, Points: 0, Legacy Rep: 91
    Location: Colorado

    river runner baker

    You can get a better explanation of reserve bouyancy in a book on yacht design, such as Skene's, than I could give. My parents (when they were alive) and I toyed with the idea of buying a cruising boat and sailing off to distant lands. We did a lot of research into what sort of boat would be best. In my mind reserve bouyancy, especially in the ends, would be something I'd want if I were ever caught out in a storm. You want the ends to lift over the waves and not be burried by them.
     
  12. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 474, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Daniel, the best advise you can get is two fold. The first part is develop your sailing experiences, so that you have a clue as to what you desire and need in hull forms, rig types, appendage optimization, accommodations, equipment, etc. and secondly do some serious studying on yacht design theory, dynamics and typical structural engineering in the build method(s) you intend to work with.

    Nothing personal, but your knowledge of yacht design is so weak and limited, you can't possably expect to draw up a successful 52' sailing vessel. Simply put, you may have some CAD skills, but without an understanding of the concepts and principles involved, your "creation" is just going to flop over on it's side come launch day. I'm not trying to insult you, but we get this set of questions all the time and enthusiasm and CAD skills don't make a yacht designer, study does (lots of it). I recommend "Principles of Yacht Design", by Lars Larsson & Rolf Eliasson as your first text book. After you absorb this, you should have a much better "grasp" of what's involved and you will not have to come to a discussion forum and ask the most rudimentary of design questions. In other words, would you be willing to fly in an airplane, that was designed by someone that asked an online discussion forum, about the "average length of wings" for a 52'er? Yep, me neither.
     
  13. sailingdaniel
    Joined: Apr 2011
    Posts: 50
    Likes: 2, Points: 0, Legacy Rep: 20
    Location: around the world

    sailingdaniel Junior Member

    Thanks again all..

    PAR.
    Thanks for your long answer. I am reading in "principles of yacht design" and has done so for the last two years. To understand what i am reading i have also had to get basic books i math. I am learning as much an fast that i can , i do my very best.. And while im learning im trying to draw a boat. I Find that helpful.

    My computer skills are not good at all and the boat u see is not generated by some program.. Its taken me hundreds of houer. In my mind, my understanding of the basic boatdesign is much better than my CAD skill..

    My experiance as a sailor is that for the last three years i have been sailing solo from norway to where im now , mauritus. Before that i worked an a commercial dive vessel in norway for 6 years..

    Im hoping to get some more book when i get to south africa, thats my next stop on my trip.. while sailing i have had a lot of time to read and study and i have done that for a few houers every day , but i might be a slow learner...

    There is few people i meet who can help me , U dont meet a lot of boatdesign teachers.. :) , Thats why im here. And while reading in the forums one thing often comes up. That is that u want more pictures/data to answer the questions asked.. So i tried to give u as much data i could..

    My understanding of boatdesign might be limeted , that is why i want commets so i can learn an get better at it.. Im not trying to take any shortcuts..

    This type of boat is what i want. I dont think its so far from a sundeer for ex. The people i have met who sail them is very very happy whit there boats.. It all comes down to "taste" . I have no problem whit other people thinks that its not a good type of boat.. For Me , this is what I want..

    I would love to here some comments of the hull and "numbers" itself.. If my skills are very low and limeted there must be something i done wrong so far.. So any comments is welcome..

    Thanks
    Daniel

    Thanks
     
  14. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 474, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Okay, simply put, your hull form looks to be a typical, canoe body with moderate B/L ratio (at first blush), therefore limited sail carrying power without a massive, deep appendage and high B/D ratio. The sections appear to be backwards (shaped), in regard to what is commonly "acceptable" now, in that the forward sections show a fairly firm bilge, while she has slacker bilges aft, where typically they are firmer. If you don't understand this concept, you have considerable more hull form study to work on. It also appears you've dragged some hull volume forward (why?) and there's a fairly crisp kink in the waterlines aft, which will be troublesome in some situations. The buttocks have a fairly good exit, unless heeled way over and the diagonals look "clean" but there's very little volume aft, so she'll not have much "power" under a serious press.

    Simply put, the wise student doesn't deviate very far from known, well balanced shapes in their first design attempts. The only way to learn is to know where you've "screwed up". The only way to know where this occurs is to make small, very incremental steps in hull form "development", so if something doesn't work, you know what it was. In short, find a hull form that you like and sail on it. After a few hundred miles under the keel, you'll have an idea of how she "acts" under different sailing conditions. If it's a set of behaviors you can live with, then this hull form is one you should base your model from. Without this practical knowledge, pretty much anything you draw is a "crap shoot", because you haven't any idea which design feature, is doing what to the preformance envelop. This doesn't mean all NA's are experienced sailors and seamen, but it does mean they have considerable "sea legs" time and a very good idea of what does what and how it does it, which is what you seem to lack. Book study is fine, but practical understanding is a much faster teacher. Knowing why you don't want a fat butted canoe body, in steep breaking seas, while running down wind in front of a storm, can only be judged first hand. I can tell you how difficult the boat is to steer, but unless you've fought a constant broaching situation and stalled rudders, you can really appreciate how important this might be.

    Take the WestLawn courses and continue gaining sea leg time on various different types of sailboats. This is the bast advise you can get.
     

  15. sailingdaniel
    Joined: Apr 2011
    Posts: 50
    Likes: 2, Points: 0, Legacy Rep: 20
    Location: around the world

    sailingdaniel Junior Member

    Thanks again PAR..

    The B/L ratio i 5. Half entry angel 11 degrees..

    The rig is only 18.5m above wl, and fairly low aspect ratio.. as i wrote before..

    In the 3d pic there is something wrong in the aft. Im using only 2d but gave 3d a try but my PC is slow. So in the aft end i had to compromise.. I added it just to give a "feel" to the shape..

    In the other pic the two lower wl (under the blue, dwl ) ar pointy in the pic , that also is not right as u se when u look at the profiles.. sorry about that..

    I know Ill need a deep keel and rudder and that is ok for me..

    The volume forward is for space inside the boat. and to get LCB and CF close together. The flare in the lower part of the forward sections and the rounder aft sections is to have simulare shape to the curv of area whit heal with out having to make the stern very wide.. Also not to get the Cp to drop to much. Now it goes from 0.61 to 0.6 at 25 degree heal.. The boat "sidetracks" if thats the word , only 1 degree/10 heal..

    All above i think is a relative balanced boat . And from my understanding a long narrow balanced boat steers more easy . Is it not so?

    The aft is inmarsat ( how to spell that ) 7 cm under water.. Maybe u missed that as it is not shown in the pic but is in writing.. The LCB @ 54% from forward wl. Do u suggest a more "powerful" stern? that would give me problem whit the balance i think?

    I totally agree whit that u need good steering in bad downwind weather. And i think many boats have to small rudders. I regard the steering "system" as one of the most important an a boat.

    I wont go to school anymore and i dont have any ides to be a "real" designer. But to learn as much as i can and one day maybe 10 years from now build my boat. Whit the help/guiding of an N/A..

    Daniel
     
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.