Max L/B ratio for a fast cat ?

Discussion in 'Boat Design' started by ryanonthebeach, Dec 26, 2017.

  1. Richard Woods
    Joined: Jun 2006
    Posts: 2,159
    Likes: 141, Points: 63, Legacy Rep: 1244
    Location: UK, USA and Canada

    Richard Woods Woods Designs

    Maybe I didn’t phrase it well. But you should still be able to see the point I was trying to make

    RW
     
  2. Richard Woods
    Joined: Jun 2006
    Posts: 2,159
    Likes: 141, Points: 63, Legacy Rep: 1244
    Location: UK, USA and Canada

    Richard Woods Woods Designs

    You should also check Ilan Voyagers comments on his professional opinions versus amateurs

    No problem asking questions but surely it is best to believe experienced professionals above others? You do if it is a health issue or an aeroplane maintenance problem

    One reason why the AYRS lost credibility was because members only tended to talk to other members and not to trained experienced professionals. So basically the blind leading the blind

    RW
     
  3. fallguy
    Joined: Dec 2016
    Posts: 1,697
    Likes: 91, Points: 48, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    What happens with such a design?

    It appears the op has dreams of great speed while long, narrow, and light.

    What is he missing?
     
  4. TANSL
    Joined: Sep 2011
    Posts: 5,501
    Likes: 152, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    You are quite right and I can not but agree with you, but it is often not easy to distinguish an experienced professional from a talkative and it is also common to see that a professional is belittled only because he does not express himself fluently in a certain language. On the other hand, people are obsessed with academic degrees that are not always guarantee of anything
     
  5. Richard Woods
    Joined: Jun 2006
    Posts: 2,159
    Likes: 141, Points: 63, Legacy Rep: 1244
    Location: UK, USA and Canada

    Richard Woods Woods Designs

    Agree with you Tansl. But with due diligence you can easily work out who to believe by going to their blog Facebook page or website

    People commonly say “the Titanic was designed by professionals the Ark by an amateur “ (although I thought god gave Noah the basic dimensions).

    Anyway to that comment I always say “yes and both were wrecked on their maiden voyage”

    Yes we English speakers are very lucky that this forum as most is in our native language

    RW
     
  6. latestarter
    Joined: Jul 2010
    Posts: 334
    Likes: 26, Points: 28, Legacy Rep: 233
    Location: N.W. England

    latestarter Senior Member

  7. dsigned
    Joined: Aug 2017
    Posts: 174
    Likes: 11, Points: 18
    Location: United States

    dsigned O.R.C. Hunter

    > There are no emotions in engineering...just facts.

    ********. Emotion is quite often what sets the design parameters and is often the deciding factor between two similar design options. It's one of the primary reason we build sailboats at all anymore. And engineering isn't "facts"; it's data, which can be varying degrees of reliable and accurate. All the engineer cares about it getting data that's good enough for the design at hand. I don't need measurements to 1/10000th if my tolerances are 1/10th.
     
  8. Barra
    Joined: Feb 2014
    Posts: 94
    Likes: 4, Points: 8, Legacy Rep: 32
    Location: Perth

    Barra Junior Member

    Good question.

    Its a law of diminishing returns past a certain point.

    Long and lean with a modest rig has appeal to many.
    I recon I would go down this route if I ever build another boat.
    Length is cheap.

    Schionnings cruiser racers are around 15:1.
    Gougeons G32 was around 20:1 (maybe 22:1)?

    Gougeons Strings was probably similar.

    18 > 20:1 would not be unusual. The down side is that wetted surface drag increases.
    You really have to sacrifice all comforts for the concept you are touting to work.

    As others have pointed out theres more to speed than just hull L:B ratio.
     
  9. Ad Hoc
    Joined: Oct 2008
    Posts: 5,920
    Likes: 316, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Nope. You are confusing the two....and putting the cart before the horse.

    Facts are things which are known to be true. The waterplane area of a vessel, for example, is known to be true to influence the period of motions of a vessel. The EI of a structure is known to be true to influence the response from an applied force....etc etc.

    Data is a summary of information of a subject...and is derived from facts...which are known to be true. The period of roll (data) of a vessel is 8 seconds or 10 seconds, based upon a WPA (fact) of...XX or YY.

    In either instance none of which has an emotion as an 'input'.
     
  10. Steve W
    Joined: Jul 2004
    Posts: 1,800
    Likes: 55, Points: 48, Legacy Rep: 608
    Location: Duluth, Minnesota

    Steve W Senior Member

    To the OP, do a little research on the catamaran Sundreamer in New Zealand, I think you may like it as it has a lot of innovative features and is for sale for a lot less $ than you could build for. No, she was not designed by a NA, many very good boats are not, but rather by an artist, a very good artist.

    Steve.
     
  11. fallguy
    Joined: Dec 2016
    Posts: 1,697
    Likes: 91, Points: 48, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    Says gone to new owner on 12/13/17.

    Neat boat.
     
  12. ryanonthebeach
    Joined: Mar 2007
    Posts: 74
    Likes: 5, Points: 8, Legacy Rep: 61
    Location: CA

    ryanonthebeach Junior Member

    I've read many of Ad Hoc posts, he's certainly an expert agreed, but has also negative, unhelpful and condescending

     
  13. ryanonthebeach
    Joined: Mar 2007
    Posts: 74
    Likes: 5, Points: 8, Legacy Rep: 61
    Location: CA

    ryanonthebeach Junior Member

    Awesome, thanks Steve, that's in the direction I'm thinking
     
  14. ryanonthebeach
    Joined: Mar 2007
    Posts: 74
    Likes: 5, Points: 8, Legacy Rep: 61
    Location: CA

    ryanonthebeach Junior Member

    Sarcasm and condescending experts aside
    Ad Hoc
    I am confident in my approach, and ive done enough ocean sailing to know what I want and what my priorities and tradeoffs are. I've built boats to plans. I now want to design & build my own, and I will.
    I get that you're an expert in your domain but if you're not going to be helpful please don't reply to my posts, you're just wasting everyone's time to inflate your own ego.
    Good luck
     

  15. ryanonthebeach
    Joined: Mar 2007
    Posts: 74
    Likes: 5, Points: 8, Legacy Rep: 61
    Location: CA

    ryanonthebeach Junior Member

    Thanks for the examples Barra
    Yes, agreed, but it's not all about speed, its also about stability & saftey in big seas.
    I'm comparing viscous and wave drag for different hull lengths that I've put some rough designs together for.
    Will post when I have enogh time to complete
     
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.