Keel Modification

Discussion in 'Propulsion' started by Ol Gillnetter, Jan 24, 2013.

  1. Ol Gillnetter
    Joined: Jan 2013
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    Location: Anacortes, WA

    Ol Gillnetter Junior Member

    Pictures of wedge with thru-hulls to alleviate cavitation noise.
     

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  2. boatbuilder41
    Joined: Feb 2013
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    Location: panama city florida

    boatbuilder41 Senior Member

    If its not a planing hull shaft angle is not so critical, as long as engine lubrication is not a issue
     
  3. Ol Gillnetter
    Joined: Jan 2013
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    Location: Anacortes, WA

    Ol Gillnetter Junior Member

    Got the mold built and filled for the "keel plug", lots of work, but it is done, need to trim it and fill with foam then encapsulate to get it ready to fasten to the hull. The hull is notched to accept the plug and was planning to expoxy or plexus the part on then likley erase the seam with a couple layers of 1708. Still plenty of work left at that point, but at least the heavy layup in the mold is done, 3/4 " thick is the end result of the sidewalls made up of 1708 and epoxy resin, couple pictures:
     

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  4. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Is the purpose of all this to make the boat go faster?


    If not , and you are just concerned the engine is more powerful, keep everything and change the gov setting to the old DD Hp .

    Probably will save $10,000 in modifications which would be hard to recover from fuel savings at cruise in 20 years.
     
  5. Ol Gillnetter
    Joined: Jan 2013
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    Location: Anacortes, WA

    Ol Gillnetter Junior Member

    I would like to gain the ability to run at more than one speed, the 53 series likes to be running at 2500 rpms, which is damn loud despite lots of sound proofing, and at 216HP a 653 is a bit shy of being able to put the boat on a plane at 15-16kts. It will push to just 13 kts at WOT. I would like to be able to cruise along at 8-9 kts efficiently as well as run at 15-16 to a fishing hole or dive spot. The boat just needs some more HP to do this, and more HP should really get some more prop to use the power the most efficiently. A 653 natural is already topped at 216, can’t do anything more than maybe drop a size larger injector in it and that really only gets a guy more coal smoke. To turbo the engine is a fair bit of work, and that doesn’t address enough prop top take more power. The boat doesn’t commercial fish and never will again, it has been torn down and rebuilt for pleasure only, the rebuild took a lot of weight out of the finished hull and she should do just fine with a few more HP. I realize the payback on fuel savings will never come around, and it was never a condition that was on the menu, sure it should get better mpg when running at 8 kts, but that will just be instant savings, not anything that will make up for the re-power. At this point there is no turning back, the DD was pulled and sold, the new engine is waiting for the mods to get done, which will take me a while at two hours a day to work on it. I hope to have the keel extension in place in the next month, just need to fill it with foam and get the mating flange machined to fit.
     
  6. JSL
    Joined: Nov 2012
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    Location: Delta BC

    JSL Senior Member

    I've only been following this post sporadically so I may have missed some details.
    For a 36' ? boat of average weight you should be looking at a 26" to 28" dia prop, particularly if you expect any kind of efficiency at speed. Make sure all the clearances are sufficient: ie: a 10%D clearance prop tip to hull (2.8") is not good (except in a tunnel), best is 20%D (5.6")
     
  7. Ol Gillnetter
    Joined: Jan 2013
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    Ol Gillnetter Junior Member

    Shooting for 26" 4 blade and will likley end up with around 4.5" tip clearance. I have been told if that is noisy then either cup it a little or go 5 blade. The boat should be at about 18K on the scale when finished, that is fueled up.
     
  8. JSL
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    JSL Senior Member

    sounds like you should be okay.
     
  9. JSL
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    JSL Senior Member

    weight, diameter, clearance, are good: you should be okay.
     
  10. Scotth80
    Joined: May 2013
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    Location: Bothell

    Scotth80 New Member

    Just a data point for you, we have a 34' Roberts (stretched 30', keel was not touched, length added above chine). We pulled back the running gear and added a strut to run a 24x20 prop. The boats has a 6B cummins @ 315 HP running a 2:1 gear. Not sure of the weight. The boat cruises 16 knots @ 2450 rpm and maxes out at about 19 knots. The bow starts to drive down and limits speed above 18 knots, could probably use a swim step to trim it a little bit.

    Nice boat! Looks great with the new cabin on it! The 36' hull is a great one.
     
  11. Ol Gillnetter
    Joined: Jan 2013
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    Location: Anacortes, WA

    Ol Gillnetter Junior Member

    Overdue update

    Been busy at the desk job, but have made progress: keel addition is on, new shaft log in, lam panel filled all open areas created withe the surgery, engine bay glassed back where shaft log enters, pretty much ready to get down to heavy layup on keel sides to finish mating old and new keel.

    gear train specs- 2" shaft, ZF280IV 2.27:1 gear, 425QSB6.7, 26X24 wheel to start with

    I also have accumulated a suprplus of itching powder, free to a good home, 10 gallons of it give or take.
     

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  12. Ol Gillnetter
    Joined: Jan 2013
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    Location: Anacortes, WA

    Ol Gillnetter Junior Member

    Long project at just a couple hours a week, but here is finished keel with bottom paint, still waiting on new rudder, working on installing engine, Cummins 6.7 with ZF V drive.
     

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  13. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    A good rule of thumb to keep in mind is DD 2 strokes get inefficient when under about 60% of the power you built it for.

    So cruising at 90% and up on the plane is fine (if you dont mind the fuel flow) , but going under 60% may not give the engines best when in displacement mode.
     
  14. Ol Gillnetter
    Joined: Jan 2013
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    Location: Anacortes, WA

    Ol Gillnetter Junior Member

    New cummins going in, the detroit went to craigslist... But I know exactly what you mean about the DD's and engine loading.
     

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  15. Ol Gillnetter
    Joined: Jan 2013
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    Location: Anacortes, WA

    Ol Gillnetter Junior Member

    Finished

    Figured I might as well put one last post here, project is done and boat is wet, all went well. Couple pics attached.

    Final numbers:
    Engine Cummins 6.7 480HP @3300, 2.276 ZF 280IV
    2" AQ 22 shaft and 26x24 Nibral Dynaquad
    100G of fuel she tops out at 24kts with engine at 82% load and spins to 3380rpms so prop seems good to go. 16kts is 50% load.

    Chris
     

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