catamarans vertical clearance

Discussion in 'Boat Design' started by Brian.Lin, Nov 27, 2017.

  1. Brian.Lin
    Joined: Aug 2006
    Posts: 37
    Likes: 0, Points: 6, Legacy Rep: 10
    Location: Taiwan

    Brian.Lin Junior Member

    dear Sir,
    how to decide the catamarans vertical clearance between waterline and wetdeck?
    I try to search information on www.
    I find following simple formula.
    a. DNV rule. HL=0.22*Lwl*(0.3-0.0008*Lwl)
    b. documents from THE SECOND CHESAPEAKE POWER BOAT SYMPOSIUM.
    Ⅰ、Displacement catamarans : t=(0.045…0.060)L
    Ⅱ、Planning catamarans: t=(0.02…0.03)L
     
  2. jorgepease
    Joined: Feb 2012
    Posts: 1,415
    Likes: 25, Points: 48, Legacy Rep: 75
    Location: Florida

    jorgepease Senior Member

    Sailing?
    Everyone always says don't compromise bridgedeck clearance but I see some big names at around 30" while other performance cats above 47" regardless of length.
     
  3. goodwilltoall
    Joined: Jul 2010
    Posts: 677
    Likes: 14, Points: 18, Legacy Rep: 31
    Location: nation of Ohio

    goodwilltoall Senior Member

    Min. 1'-0" clearance (no obtructions) for every 10'-0" Beam OA.
     
    fallguy likes this.
  4. JSL
    Joined: Nov 2012
    Posts: 526
    Likes: 12, Points: 18, Legacy Rep: 41
    Location: Delta BC

    JSL Senior Member

    A guide I got from a well known multihull designer (power and sail) was minimum of
    Disp. hull = 6 1/2% of the DWL (ie: 30' DWL = 1.875')
    Planing hull = 3 1/4% of the DWL

    As a check I looked at a 65' power cat (225 passenger tour boat, semi-disp hull form- cruise 8-10 knots) I did several years ago. Wet deck freeboard was 3.0' on a 60' DWL = 5%. Boat does harbor tours so water is usually calm.
     
    Last edited: Nov 28, 2017
  5. Mr Efficiency
    Joined: Oct 2010
    Posts: 6,303
    Likes: 132, Points: 63, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    These formulae are a guide, I suppose, but other factors affecting the calculation would be area of operation, slimness of hulls, vertical taper of hulls, shape of intersection of hulls with the wet deck, and provision of wave breakers. Or at least, I "imagine". :cool:
     
  6. JSL
    Joined: Nov 2012
    Posts: 526
    Likes: 12, Points: 18, Legacy Rep: 41
    Location: Delta BC

    JSL Senior Member

    Correct
     
  7. TANSL
    Joined: Sep 2011
    Posts: 4,654
    Likes: 87, Points: 58, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    They are a guide indeed, there is no rule that requires a minimum value of the air gap but, depending on the navigation area, Lwl, ... and the air gap you will have to reinforce more or less the wet deck.
     

  8. Ad Hoc
    Joined: Oct 2008
    Posts: 5,354
    Likes: 207, Points: 63, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Depends on the type of catamaran, its duty, role, location of operations, what is it: yacht, passenger, crew boat, fast ferry, and of course sea conditions...etc etc
     
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.