Conference unifix::sailing

    I had a Martec folder on my Pearson 40 and found it to be "reasonable"
    by this I mean I understood that it would not alow the boat to back
    down as well as a fixed blade prop and it didn't. However it did
    fold and therefore increased my speed under sail. 
    On my present boat, a Nauticat 43, I ordered a Maxprop feathering
    three blade. I have been overjoyed. The boat motors like it has
    a fixed prop, backs down like it has a fixed prop and sails like
    it has a folder. An increased benefit of the Maxprop is somw
    flexibility concerning the pitch of the prop. You can increase or
    decrease the pitch to some extent based on speed/rpm/etc.
    As further Maxprop propaganda the SSCA (seven seas cruising club)
    gave the Maxprop one of it's four "perfects" in their yearly servey.
    The only negative is the expense. The 16x22 was $1500.

    Also look at the feathering props build by Luke (not
    sure of their location -- anyone else know?).  VERY
    durable and dependable.  My father has had a three-blader
    on his boat for a dozen years at least, and it has always
    performed flawlessly.
    
    The Luke also had variable pitch.  I'm not sure, but I
    don't think the Maxprop does.  Variable pitch "is best."
    
    

Luke is in Boothbay Harbor, ME. 

Variable pitch propellers add a fair bit of complexity to the
transmission-propeller shaft-propeller system. The ones I've seen use a
hollow propeller shaft to which the propeller is attached. Inside the
propeller shaft is another shaft that is used to adjust the pitch of the
propeller blades. I'm not sure that the advantages of variable pitch 
(especially on a sailboat) outweigh the disadvantages of added weight, 
increased cost, increased maintenance, and reduced reliability.

    I agree with the possibility of problems associated with a variable
    pitch prop. A friend had one on his Westsail 42 and it was a constant
    hassle until he replaced it with a fixed prop.
    You might try some of the foreign mags for some ideas as varialbe
    pitch and feathering seem to be used more there while folders are
    a USA variant.
    Luke has an excellent rep.

    Uh oh, I guess variable pitch is the wrong term (seems I'm
    really slipping up lately).  The Luke prop on my Dad's boat 
    does not have an internal shaft.  I was referring to the design 
    of the prop's blades.  Their angle of attack to the water is 
    greater at the hub, and flattens as the diamater increases.  What 
    is this called?  The Maxprop has uniform pitch from the hub out.  
    Not as efficient, and prone to "walking" in reverse from what 
    I've heard.
    
    At any rate, the Luke-type of design I'm referring to provides 
    better thrust for a given diameter and rated pitch.  Alan, I'm sure you
    know what I'm talking about.  Can you elaborate?  Or has this
    been discussed in an earlier note?
    
    Do a dir/title=propeller, Dean...
    
    Thanks  ;)

    I think the Maxprop has preset stops that can be reset, with the
    prop removed, to adjust the effective pitch.  Apparently you fiddle
    with it till you get the best compromise for the boat, then leave
    it like a fixed prop.
    
    Anyway, I wondered whether the prop hitting the stops is a cause
    for wear, noise, or other problems.  Anyone know?
    
    Rick,

    As far as the noise is concerned there is less with the MAXprop
    than with the folder opening. As far as length of service mine mas
    been in use for three years and has shown no signs of wear. These
    props have been around for a while, in use mostly by the racers,
    

    The Luke on "Allez" is at least a dozen years
    old and is still in perfect working condition.
    

    Since I can't find the note which digressed into this propeller
    discussion, I'll put my reply here (appropriately).  What follows is my
    transcription of all the text in the Cruising Design, Inc. ad which
    appeared in the Feb/Mar issue of Small Boat Journal.  The also have a
    picture, which is reminiscent (to my eyes) of a high-speed prop with
    straight trailing edges; the one shown is two-bladed.  Here's the text:
    
    PERFECT PROPULSION
         The performance of your engine is only as good as the propeller 
    it turns.  With the Cruising Design Performance Propeller with Crystic
    CopperClad you will gain speed, thrust and maneuverability.
         The CD Performance Prop has a new and unique computer-designed 
    airfoil shape that gives your engine 80% more thrust in reverse and 
    20% more in forward.
         [There's a little diagram of a blade cross-section shown, with 
    this caption:  Unlike bronze blades, the CD blade is curved on both 
    sides like a true airfoil.]
         All CD Performance Props provide greater speed at lower revolutions,
    reducing noise and vibration while improving fuel efficiency.
         CD Props are also available in Crystic CopperClad, either solid or
    coated, to prevent barnacle growth that inhibits performance and adds
    maintenance.
         Remember, perfect propulsion can only be achieved with a Cruising
    Design Performance Propeller.  Available in 12", 14" and 15" diameters. 
    Call Joe today for more information at 508-532-2712.
    
    CRUISING DESIGN, INC.
    "The most reliable products for cruising"
    P.O.Box 151
    65 Walnut Street
    Peabody, MA 01960
    508-532-2712   VAX: 508-531-7577

    I put a Gori folding prop on elysium two years ago.  Reverse is much
    better with the Gori than it was with the fixed prop which came on the
    boat.  I've had people who have Martec props on their boats tell me
    that my boat has better response in reverse than theirs.  I've never
    been aboard a boat with a Martec, so can't make a first hand
    comparison.
    
    The Gori is made in Northern Europe, Denmark, I think.  The blades are
    geared to one another, such that one blade cannot open without the
    other blade opening, also.
      
    Late this past season I noticed my speed when powering was at least a half 
    knot slower than I would expect. When the boat came out, I found out
    why.  Barnacles and mussels had moved into the gears, preventing the
    blades from fully opening.  Guess that's what comes from not using the
    engine often enough. 
    
    I forget the size, but elysium is a C+C 29, and the prop shaft is 7/8
    of an inch.  The prop cost about $750.
    
    djc