Philippines Banca 100 Islands

Discussion in 'Boat Design' started by 100islands, May 30, 2013.

  1. 100islands
    Joined: May 2013
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    Location: Philippines

    100islands Junior Member

    Greetings everyone, we have recently started our build of a 36' Philippines Banca, our building is taking place on Santiago Island, 2nd largest of the 100 Islands Chain, PH.

    Banca boats are exceptionally stable due to the outrigger design, they have very low drag, which allows them to be fuel efficient. They are commonly powered by 16 hp Briggs and Stratton engine however we have opted to power this boat with a larger twin for longer and smoother running times.

    This Banca will be modified from standard design, it will have a slightly larger and more flat planing area for increased cruising speed and fuel efficiency.

    I will be posting progress photos and would be happy to answer any questions. Please enjoy!

    Build Specs:
    Single Main hull with 2 outriggers
    28' Solid wood Keel
    4' Bow
    4' Stern
    36' Total approx length

    Propulsion:
    30 HP Twin Cylinder - Kohler Command Pro (Gasoline)
    8' Stainless Shaft
    8" Long Tail Prop

    DAY 1-2 (Hand carved Keel)

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    Last edited: Jun 3, 2013
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Very nice, I love riding on the Bancas.
    Where is this one being built?
     
  3. 100islands
    Joined: May 2013
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    Location: Philippines

    100islands Junior Member

    Build Day 3-4

    Build Day 3-4

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  4. 100islands
    Joined: May 2013
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    Location: Philippines

    100islands Junior Member

    North Western Luzon
     
  5. 100islands
    Joined: May 2013
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    100islands Junior Member

    In regards to this build,

    We have a question for the members about prop placement. Usually these bancas are deep v hull non planing like a canoe basically and shaft comes directly out of the stern without much precision.

    Is there any formula on how far below the hull should the top of the prop blade be located?

    Also any advise on the optimal angle in which a shaft should be running from power source?

    I noticed some of the larger power boat designs shafts are angled downward somewhat rather than horizontal to the waters surface. Any advice on optimal angle for best cruising?

    Thanks in advance!
     
  6. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    The lesser the angle the better, the greater the distance between the hull and the prop the better. Min is best around 20% of prop diameter. But of course the length of shaft this generates will dictate too..since the length of shaft from the stern tube if too long, you'll need a p-brack of sorts to support it.
     
  7. 100islands
    Joined: May 2013
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    Location: Philippines

    100islands Junior Member

    The distance from prop to stern is limited on this build because of the rudder that must hang off the transom into the water behind the prop.

    About the angle we can minimize that with the Thrust bearing joint (Python) well be using well try to get it as straight as possible. We are planning on a approx 8 foot 3/4" shaft size.

    Thanks for the advice!


     
  8. noli
    Joined: Jul 2012
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    noli Junior Member

    ..

    l really like this thread.

    Please keep the pics coming.







    Noli
     
  9. 100islands
    Joined: May 2013
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    100islands Junior Member

    Any thoughts on a 8 foot stainless shaft @ 3/4", if balanced properly coming from the thrust bearing direct to the prop without a p-brack should be ok?. It will reach 4k rpm. Thanks!!


     
  10. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    It'll wobbly about far too much without a P-Bkt. Also you should support a shaft of that diameter at roughly 1.0m spacing with supports/bearings etc. Again, you'll get excessive vibration otherwise and could also damage the shaft permanently too.
     
  11. 100islands
    Joined: May 2013
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    100islands Junior Member

    Its mostly due to the placement and angle of the engine that we need the 8' ...however we might be able to go down to 7 feet.

    Perhaps we should increase the shaft size to 1" or 1-1/4" we were initially concerned about the weight of the shaft and the limited HP im not sure how much extra load that creates on the engine. Im also not sure if i can find bearings for this application here, normally used is 10foot 1/2" shafts they do have high vibration.

    *Update Found Pillow Blocks in 3/4

    thanks!

     
  12. noli
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    noli Junior Member

    .

    What are these 36 foot Bancas used for ?



    .
     
  13. 100islands
    Joined: May 2013
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    100islands Junior Member

    Fishing, Diving, transport inter-islands. These are not incredible seaworthy so mostly for protected bay use. The strong point is the fuel efficiency at 1GPH at cruise, hard to beat.

     
  14. noli
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    noli Junior Member

    .

    Very impressive!

    We can convert the banca to a mold for you where you can begin building the bancas out of fiberglass.

    Proly save some weight, and we can create a flat transom where we can design a drive system to allow the drive shaft to be lower and thus closer to horizontal position to maximize efficiency.



    would be a cool project.



    .
     

  15. 100islands
    Joined: May 2013
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    Location: Philippines

    100islands Junior Member

    Yes it does sound like a cool project! We will be glassing the outside of the hull. Having a mold woud be great, would really bring the weight down.

    More pics soon!



     
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