Houseboat review

Discussion in 'Stability' started by ddrdan, Mar 30, 2010.

  1. ddrdan
    Joined: Mar 2009
    Posts: 67
    Likes: 2, Points: 0, Legacy Rep: 37
    Location: Raleigh NC

    ddrdan Junior Member

    I'll admit it. I know just enough about vessel design to be dangerous!

    My friend and I like to go to the coast and fish from an 18' bay boat. We hate putting in and pulling the boat out every day so we can go to the hotel room. We want a shack houseboat for our weekend fishing trips. I've built 2 stitch & glue before so we decided to build one.

    I'm embarrassed to say that while drawing the plans I paid no attention to the height. I drew the plans from the bottom up and then realized the height exceeds the beam. To me it seems it would roll with the slightest shift in weight? Seems to me I must also go wider for the head height required?

    Bottom to deck line material weight = 750#
    Deck to roof line material weight = 600#
    Estimated passenger weight = 600#
    Livewell - Cooler - Water - Equipment = 800#
    Engine & fuel weight = 125# (9.9HP)
    Overall height = 8'-2 5/8" - Height above deck = 6'-6" - Draft = 10" (+/-) ???

    We wanted minimal use of the roof area. I can shed 150# from roof materials if using the roof is unrealistic. We can also delete the livewells if necessary.

    Can you take a look at the plans and give us some suggestions.

    Thanks,
    Dan
    [​IMG]
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  2. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    You have the opportunity to drop the cabin down to the bottom frames. Judging by the plan you could arch the top and drop it at the sides a good foot. Then try lengthening it to 16 ft. Might work well that way. A door could lead aft from the head to another deck, which is where I'd put the extra 4 ft of length.
     
    1 person likes this.
  3. rasorinc
    Joined: Nov 2007
    Posts: 1,854
    Likes: 70, Points: 48, Legacy Rep: 896
    Location: OREGON

    rasorinc Senior Member

    Go to the Glen-L site http://www.glen-l.com/ under boat plans click on houseboats and look at HUCK FIN, and WATERLODGE both designed by an Naval Architect.
    and have tall cabins but were designed for that. You can buy study plans for a few $$. This will give you some good ideas ++++
     
  4. dskira

    dskira Previous Member

    You are not that far off. Follow Alan's advice, and to be on the sure side follow Rasorinc advice about the Glen-L.
    A few dollar and you will be on your way for a lot of fun.
    Good luck
    Daniel
     
  5. ddrdan
    Joined: Mar 2009
    Posts: 67
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    Location: Raleigh NC

    ddrdan Junior Member

    Thanks for the help folks!! We are going to pontoons instead!

    We already have a pile of cold rolled galvanized Cee's and Angles in my stock pile we can use for the deck framing and transom. Pontoons, steel frame and 3/4" deck weigh only 800# for an 8' x 14' deck area. The cabin increased to 7'-6" x 7' x 6'-4" tall, giving us more room. Thanks Rasorinc for the direction we needed to go.

    One more question. My buoyancy calc on the 2 pontoons combined is 5680#. They are 20"(w) x 22"(h) x 15'-6" (+/- with bow shape). Adding 2000# above deck will give me an 11" +/- draft, correct? That's half the depth of the pontoon, is that a good ratio or should I increase the size?

    Thanks again for the help.
    Dan

    PS: How do I explain the 20 hours of wasted detailing time on the old design to myself? :D :D
     
  6. dskira

    dskira Previous Member

    What about our time? We will send you an invoice :p
     
  7. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    Rough calc.: Boat weight + crew and stores x 2 = pontoon displacement.
     
  8. ddrdan
    Joined: Mar 2009
    Posts: 67
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    Location: Raleigh NC

    ddrdan Junior Member

    OK ... lets see ..... Alan gave me a sound design change ........ Rasorinc gave me a link to a total design change which fit perfectly ...... you told me what they already said ..... and which one of you wants to send me an invoice?? And they say engineers are geniuses?

    Just kidding!!:) :)

    Thanks guys ... I'll post the new design soon and pics as we build it.
     
  9. ddrdan
    Joined: Mar 2009
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    Location: Raleigh NC

    ddrdan Junior Member

    Basic, succinct, and K.I.S.S. You're my kind of guy!! Thanks, that did the trick.

    800+2000*2= 5600 !!!!!

    Either I got real lucky or I should quit my structural engineering job and become a budding Naval Architect? Naaaaaaaaa. :)

    It's amazing how I can design things to stand on land and resist all the elements, but when it comes to fluid dynamics, I'm almost totally lost. You'd think there would be a point of cross over in design relation at some point. As of yet, I ain't seeing it! You guys win, yours is way more complex with intricacies that would baffle Einstein. And then you give me a nice basic formula? Go figure.

    Thanks Alan!!
     
  10. raw
    Joined: Jul 2006
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    Location: Oz

    raw Senior Member

    Not to point out an obvious flaw here...

    but you might want to reconsider having two guys sleeping on the same side. 2 100kg guys like you have will give 5-6 deg of heel.
     
  11. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    Wise words. A ballast tank to starboard would help. Maybe 100kg of water (25 gallons) would pump in in only a few minutes, and dump out instantly. It would make up for the heaviest person (who should sleep on the bottom).
     
  12. ddrdan
    Joined: Mar 2009
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    Location: Raleigh NC

    ddrdan Junior Member

    I saw that as a problem too. The limited cabin space, and possible layouts for bunks had me stacking as an only solution.


    I had the same idea, except, it's more like 110kg:) We're big guys.

    I have an over sized livewell, just forward and starboard of the bunks that I was going to use to accommodate the heel. The 8 CF gives me around 200kg of water, which will counter the bunks and the port cooler. During the day I can just add enough water to counter the port cooler. But it seems to me I'd have eccentric loading with that live well forward of the bunks? Is that right?

    I'm just now researching "how to's" on CG calcs and reviewing the loading on the new pontoon design.

    I am integrating the deck framing into the pontoons transverse framing to lower the vertical CG. The framing is 16ga - 2x4 galv, steel Cee's. It also allows me to delete the top ply of the pontoon and attach the deck directly. Is it worth the trouble or should I just put the framing on top of the pontoons?

    [IMG=http://img189.imageshack.us/img189/1451/02floorplan.th.jpg][/IMG]
    [IMG=http://img691.imageshack.us/img691/7446/02hull.th.jpg][/IMG]
    [IMG=http://img687.imageshack.us/img687/8417/02starboardview.th.jpg][/IMG]
    [IMG=http://img263.imageshack.us/img263/3787/02weighteval.th.jpg][/IMG]

    On the starboard view is a water tank & pump a friend gave me out of an RV. Any idea where I can put it? Centered on the roof?
     
  13. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    I recommended a small side ballast for a comprimise. I realize two guys would still lean the boat, but if one gets up, with equal ballasting, the ratio between weighted sides would be 3:1, rather than 2:1.
    Better to allow a small difference that allows someone get out of their bunk without the boat shifting suddenly and throwing the other guy on the floor.
    The design is developing well.
     
  14. ddrdan
    Joined: Mar 2009
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    Location: Raleigh NC

    ddrdan Junior Member

    I never thought about that! Might be a good prank to play on my fishing buddy late at night though?:)


    Thanks again for your advice. It's truly appreciated.
     

  15. peterAustralia
    Joined: Mar 2006
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    Location: Melbourne Australia

    peterAustralia Senior Member

    hi

    Not sure where you are up to with your design

    But you NEED to increase beam to 8ft. I really would nto think it safe at 6ft. One big wave and you are at a high heel angle.

    2 pontoons in catamaran arrangement, then your cabin on top of that, that is a nice simlple, smart idea.
     
    1 person likes this.
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