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Folding (not feathering) props for a (multihull) sailboat

Discussion in 'General Sailing Discussion' started by lestercressey, Dec 19, 2020.

  1. lestercressey

    lestercressey New Member

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    I did a search on CF for folding prop reviews. I have a Martec Mark III 2-blade but they are no longer in business. I want a folder, not a feathering props to improve my sailing speed and reduce catching kelp strands or fishing nets/lobster traps. Any suggestions?
  2. HTMO9

    HTMO9 Senior Member

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    Sail drive or shaft? What kind of engine (HP)?
  3. HTMO9

    HTMO9 Senior Member

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    The choice for the best propeller for a multihull sailboat depends on the size of the boat and the engine power.
    A folding prop may not always be better than a folding prop. I assume we are talking about a multihull at 60 ft LoA or less.

    There was very comprehensive test in the YachtingMonthly magazine with test about those wheels. They tested various props in regard to thrust, bollard pull, drag when folded and fuel consumption.

    For me those large varaity of available props in this size narrows down to two providers.

    1. The Gori foldable prop. It comes as 2-blade, 3-blade or even 4-blade. I have had this prop on several sailboats. Trouble free, easy to clean and mount, even under water.

    GORI-ImagePropel-30-cm.jpg
    87435-CC-Flatten.jpg
    This prop works perfect on shaft and saildrive. And this prop comes as an option with an overdrive function. Means, when unfolding during engine start, You can select a different (higher) pitch for mor ecconomical cruising by just going shortly in reverse. So actually, two props in one. I personally would go for this overdrive option only with a turbo diesel engine, as the the prop in overdrive mode places some more load on the engine with a little higher CHT on normal aspirated diesel engines. The turbo compensates for that. A 50 HP engine will save about half a Gallon of diesel fuel per hour at the same speed but lower RPM.

    2. The flex-O-fold foldable prop. This prop won the test made by YachtingMonthly in most categories. We have of that those examples in use at the moment. Best prop ever for this size of boat (64 ft monohull racer).

    The YachtingMonthly test can be downloaded from their website. Both propeller companies are located in Denmark like several others. They ship worldwide and spare parts are available within days.

    If You are using a shaft setup, I would add a bold on rope cutter in front of the last strut. Very easy to screw on and no noticable penalty, as far as thrust and drag are converned.
  4. AnotherKen

    AnotherKen Member

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    Why would you put a rope cutter in front of the prop if you are trying avoid damaging nets and lobster trap ropes?
  5. leeky

    leeky Senior Member

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    Because the rope cutter might cut the ropes that can't be seen or avoided.
  6. AnotherKen

    AnotherKen Member

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    Yes, but Lester appears to be asking if there is a prop that would not get fouled by ropes or nets so it could be used without damaging them or the boat's prop.
  7. leeky

    leeky Senior Member

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    I assumed the rope cutter was recommended as an aid to preventing the prop from being fouled, because lestercressey said that he wanted a prop that would "reduce catching kelp strands or fishing nets/lobster traps;" he said "reduce" and not eliminate. I'm just guessing, though. Maybe HTMO9 will chime in and educate us.
  8. HTMO9

    HTMO9 Senior Member

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    We never had a rope cutter on our Gori Props. As soon as You stop the engine and the prop is folding, any rope will slide off the prop by itself. We had once one of our own lines entangled around the prop during mooring maneuvers. As soon as the engine was stopped, the crew could pull the line off. One prop was damaged by a floating debris (a large 4 blade). We were able to exchange the prop in the water with two crew members with scuba gear (we always carried a spare prop).

    The only thing I would use with caution on the Gori prop is the overdrive function. On advice of the engine manufacture, we added an EGT indication on the engine displays for engine health monitoring. Very low RPM in the overdrive mode may result in higher CHT.

    On any other variable pitch prop I would use a low resistance rope cutter just for the peace of mind. But for a true sailor the advantage of the little higher thrust of a conventional prop is not worse the hassle compared with the Gori prop. The Gori is IMHO the best prop for any sailboat from 30 ft to 100 ft + LoA, if you monitor the sacrificial zinc.

    My present large cruiser / racer sailboat is retracting both props completely into the hull when sailing. This is the best solution I ever had. But this works for larger boats only.