Define what a Surface-Piercing propeller is

Discussion in 'Propulsion' started by tom kane, Jul 12, 2009.

  1. powerabout
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    powerabout Senior Member

    pretty cool set up Chris
     
  2. ChrisN67
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    ChrisN67 Senior Member

    Carbon Fiber Transom Lamination and Water Pickups

    The carbon fiber was laminated than vacuum bagged onto the transom, prior to the painting. It was routed and filled with AwlGrip Filler then painted.

    The transom water pickups are the only source of raw water on the vessel. Countersinks were made from bronze in the areas where I could not bolt through due to the stringers.
     

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  3. ChrisN67
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    ChrisN67 Senior Member

    Misc Pics

    Engine, Transmission and drive rebuild. All sandblasted epoxy primed and 2K epoxy paint. "Yanmar" Logo was done in gold leaf

    New engine placards made out of stainless. Plumbing system , etc...

    CG Calculations and shifting for better Surface drive performance.

    Electrical system layout with remote battery switches, auto charging relays and USB- Programmable Power Distribution Modules

    ALL electrical load goes through the Ground shunt BEFORE the batteries so the Balmar 180 AMP alternator connected directly to the batteries with 240 Amp Breaker

    Custom Hinges, Air Intakes, Dorade Boxes with integrate transom catch box and drain.

    Qty(3) 50 Watts HID bronze housing transom under water lights (from Aircraft Taxi lights)

    Qty(3) Abyss 1500 Series Blue Led transom Lights

    Qty(2) 50 watt HID forward looking Carbon Fiber KC pods lights.

    Any Questions feel free to ask.

    Any questions just ask.
     

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  4. ChrisN67
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    ChrisN67 Senior Member

    Prior to using the epoxy, various methods of surface preparation were made and different epoxies and fabric were tested for adhesion. It turns our that water and soap created a better adhesion than acetone or lacquer thinner
     

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  5. ChrisN67
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    ChrisN67 Senior Member

    New Engine Placards

    It took a little time to desgin them...but what the heck, all that work on the engine (complete rebuild) and then stick a crappy placard on it?

    When I was gold leafing the "Yanmar" it made no sense to use the old placards....
     

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  6. ChrisN67
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    ChrisN67 Senior Member

    I am officially off topic... Time to cease and desist.

    If anyone wants to chat about the rebuild, and challenges and new methods, please advise. I encourage anyone working on boats with new and improved methods to start a thread or email me.

    Thank you
     
  7. tom kane
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    tom kane Senior Member

    What I see of new technology I would be inclined to accept a S/P propeller blade profile that is blunt on the front side cupped, but no camber but tapering off to the trailing edge. The angle of attack is very aggressive on S/P propellers now and must be at the limit of forward motion.
    The blade would travel in it`s own pressure wave. Quantum Mechanics is about wave functions and sub atomic particles behaving as they must in the environment we create turning propellers and such like.
     
  8. powerabout
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    powerabout Senior Member

    the guys that design the props on the worlds fastest boats only have a degree in experience hence its all art not science
     
  9. Don H
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    Don H Junior Member

    This has been quite an interesting thread to read and has spanned several years with some very technical input.
    Some years ago i raced tunnel hulls with what was called a surface piecing prop, the class was 1000cc supersports which was dominated by mostly OMC short shaft outboards. The 75 Stinger or 75 Hustler were most common unless you had the extra money and could afford the nitrous injected FT units or the MERC XS650.Chrysler made a black short shaft at the time but was an 85hp so was too big for the class.
    I had the Hustler and my propshaft was about 1 inch above the bottom of the sponsons so at full noise only 1 blade would be in the water at a time (maybe the term should have been water piecing rather than surface piercing.) I ran a 12 x 23" 3 blade OMC cleaver with solid hub and no exhaust tube. ( some thought the long prop exhaust tube could actually provide some lift but i never noticed any difference) i sharpened the leading edge of each blade with an angle grinder and polished the black teflon coating off but that was all the modification it got. The Hustler's water pickups were well above waterline but those old outboards had a second pickup at the rear of the cav plate, the rooster tail was so big it had no trouble catching cooling water.
    That prop cost me $350 almost 40 years ago and like chris's props it lived in its box under the bed too.
    The thinking was pretty simple at the time and that was to get as much of the gearbox out of the water to lower drag.Only one blade in the water meant less load on the motor, less load on the motor meant more revs, more revs meant the motor developed more of its hp, more HP meant you could swing a bigger prop.Bigger prop makes you go faster!! There were many compromises, go too high and you have less of the outboard skeg in the water which caused a large amount of propwalk,or you don't get enough grip, too low and the outboard had trouble spinning such a big prop. Mercury has one of its short shaft race engines the MERC XS650 which was even available with a hydraulic jacking plate to alter how much prop hit the water. They were fast but the cost again made them rare.
     
  10. ChrisN67
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    ChrisN67 Senior Member

    40 years ago! and surface props still are considered an "exotic application"?

    It is interesting to note that some prop shops tell you not to worry about the balance on a surface prop as it is already running with asymmetrical load.

    I will be putting this 3 year project in the water by months end. We will see how it likes the water in the Arabian/Persian Gulf in the winter. The whole idea behind surface drives and diesels was reliability and speed just in case we come across unfriendly characters while diving on the edge of Kuwait territorial waters.
     
  11. indywtf
    Joined: Dec 2013
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    Location: great lakes

    indywtf New Member

    great build on the intrepid!

    chris i'm like you and spend allot of time to completely de-rig, rebuild, and re-rig. you did a great job and have a creampuff there. congrats. I have built for a living my entire life and love what you did. is the carb fib on the transom clear coated or black paint? cant really see from the pics. love the drives!!!

    oh back to topic, here's my latest surface drive project, I picked it up this week. re-power will be in the build. I have ran choppers on other boats to get the extra bow lift but the attitude this boat runs, I will run a cleaver with a lighter outboard. that's a 600 lb. 300hp V6.

    starting point on 88' eliminator...

    [​IMG]

    [​IMG]
     
  12. indywtf
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    indywtf New Member

    wow chris, that is truly an impressive build, you spared no expense. I would love to hear on the performance after you splash, the conditions, and if you had any issues getting the boat on plane.
     
  13. ChrisN67
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    ChrisN67 Senior Member

    A water version of a crotch rocket

    I have always been curious regarding the tuning of these little rockets boats. I have seen many videos of then flipping. It is usually a laterally oriented flip after a chine walk event, but about 30% of the time the flip over longitudinally from aerodynamic lift. How do you control that?
     
  14. tom kane
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    tom kane Senior Member

    The time comes when you need to decide if you want to go boating or flying then you need a specialized craft for that purpose. You can only push the limits of a particular design so far then you need new technology. There are new aircraft that can achieve 12000 MPH but they can not control them yet.
     

  15. Greg Lars
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    Greg Lars New Member

    Curious Lurker: First Post

    I have decided to emerge from Lurker status, because I have pun I need to share. It is in regard to the discussion of how thrust is produced, i.e. suction on the back versus pressure or displacement on the face vs. atmospheric pressure filling in the contracted wake downstream, etc...etc...

    And now, the pun you've all been waiting for:

    The prop doesn't operate in a vacuum!

    Oh my, that was bad. What I mean is, the pressure on the back of the blade is low relative to the face. And the velocity of the water downstream is fast relative to the water upstream. And the contracted downstream wake is "filled in" due to atmospheric pressure acting normal to the water surface, relative to undisplaced water nearby. So you're all right! In a way! (Unless you're completely wrong.) The prop functions in a system. The system is composed of pressure differentials and energy transfer and fluid motion and thermodynamics and viscous effects...and to isolate one of these factors as THE mechanism of thrust, is erroneous.

    It's like the African butterfly fart that blossoms into a hurricane. It's all one big, happy system. My question is; what did the butterfly eat that made it so gassy?
     
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