Small 60 - 90 degree tunnel to get bigger prop viable ?

Discussion in 'Sailboats' started by globaldude, Jul 21, 2006.

  1. globaldude
    Joined: Jan 2005
    Posts: 110
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Whangarei New Zealand

    globaldude court jester

    Hi guys, I did try to ask this question on an old thread,but apparently it was too old for me to reply to so I'll ask it here .
    I have a shoal draft yacht [ in construction ] and am shortly to drop the keel to enable me to fit a larger prop - amongst other things - I was wondering about fiting a semi pipe / tunnel [ probably only 60 - 90 degrees ] to enable a larger prop / better, or more tip clearance .
    I have a big old slow reving lister [ 1100 rpm max ] with lots of tourque so a large prop = better efficiency , right !?.
    Pete.
     
  2. messabout
    Joined: Jan 2006
    Posts: 2,975
    Likes: 187, Points: 63, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Pete;
    Try to find a copy of Dave Gerrs' :propeller Handbook. It contains a wealth of information about application and selection. There is also information about Kort nozzles and the like.

    I believe that shrouded props work well for low speed applications but not well for high speeds. With the big Lister you are not likely to be a speed demon so perhaps your idea has some merit. If your Yacht is a sailboat then the big prop will make much drag while under sail. If it is a power boat intended for moderate speeds, then a large diameter prop is probably more efficient than a smaller one.
     
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.