Help on upper deck

Discussion in 'Fiberglass and Composite Boat Building' started by francois100, Oct 21, 2010.

  1. francois100
    Joined: Oct 2010
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    Location: Soutg Africa

    francois100 Junior Member

    Hi my name is Francois and a rookie as well. Please dont crap on my head I am not a boat designer just enjou working with my hands. Can some of the experienced builders have a look at my pdf and give me some comments. Almost based on pontoon design. I worked it out and each hull can take 3000kg. The boat is 20'. Outboard 15-50 hp just for cruising down the river. Hoping it may take 15 people. My mane worry is the upper deck and how to make it sturdy. Is currently supported from the beam inside the hull and will be one structure with the boat. Any ideas on making the top deck strong enough. thanks
     

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  2. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    You need to specify some sizes and materials planned.
    The most obvious improvement is to modify the design to increase structural strength. Curve and laminate the upper corners for increase rigidity, spread the superstructure weight over two stringers


    The other trouble area is that you have the stringers sunk below the upper deck level, so the supports have to go through the deck for joining. Either bring the stringers to the deck level, or add 'filler' blocks to achieve deck level supports. This means you can bolt directly to something solid without creating 'thru hull' problems.

    Just a few starting items.

    eg
     

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  3. francois100
    Joined: Oct 2010
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    francois100 Junior Member

    Thanks

    Thanks for the reply. Now that you showed me this it seems quite obvious. Was thinking of using 12mm ply and then fiber glass. I was hesitant to use a bolt on system and though by making hull and deck one piece would be stronger. My hull design will it work. It is 31" at bottom and 35" at top. Inside the hull I have 7 ribs. The boat is 9 foot by 20 foot long. Should I make the 2 hulls sepaprate and then put it together or can i build the 2 hulls and centre between hulls as one piece. Thanks
     
  4. francois100
    Joined: Oct 2010
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    francois100 Junior Member

    Sorry

    Here is what I am trying to say
     

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  5. rwatson
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    rwatson Senior Member

    Just one question, why are the stringers not hard up agains the hull at the top and side ?
     
  6. francois100
    Joined: Oct 2010
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    francois100 Junior Member

    I wanted to make the 2 hulls and centre piece one unit. I drop it down so that the centre cross beam is level with the top of the deck. The other reason is that i am not a boat designer. Lol. That is why i am asking if i can nake the 2 hulls as one piece. Also the support beams for the centre piece comes from the bottom stiger. I have an CNC machine so i can change the ribs as i want. Do you think i must remove the angled supports. Am i over designing here. If not how do i use the supports without creating thru hull problems. Here is what i wanted to do. Cut the ribs with the machine, assemble the the ribs and stingers for both hulls. Level hulls and position. Mount cross members and angled supports. Use thin marine ply to get desired shape, glass the complete assembly to become one piece. Please bear with me this is my first time. Would you please comment on the hull size as whell. Thanks
     
  7. francois100
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    francois100 Junior Member

    Stringer

    Is this b better option
     

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  8. francois100
    Joined: Oct 2010
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    francois100 Junior Member

    More or less

    Hi I know this is not some of the boats that is being build from this forum and there is not allot of people willing to comment, After Rwatson's comments this is more or less the direction I went in.
    2 Individual Hulls, cross members mounted as an pontoon boat.
    I have put drafts and curved most of the design.

    The build is going to be mm Marine Ply and glass.
    All the stringers is moved to the out side.

    Thank so far rwatson, can any of the other senior members comment *** well.

    PS, I know she is not to best but will be fun to build for an inexperienced builder and it will be fun to cruise with.

    Thanks for the Help.
     

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  9. rwatson
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    rwatson Senior Member

    I think the reason why comments arent forthcoming is the obvious missing info. Have you got the hydrostatics worked out ? "each hull can take 3000 kg" is very basic. There are very few dimensions, no weight table, ( 15 people would be veeery ambitious ) and lots of 'gotcha' areas. Commenting on this very basic design concept is being sucked in to a vortex of 'what if's'. Basically, it appears to be a very usefull, practical design ( apart from the flybridge which I think is going to make the whole thing a safety issue )

    If I were you, I would take the design as it is at the moment to a qualified designer for checking and material specs. For the thousand dollars or so, you are saving several thousand dollars of problems, and adding even more value to the re-sale value ( yes, you will want to sell it sometime)

    Even better, I would guess that you could buy existing plans that would fulfill your design requirements,

    Sure , its fun to be creative, but when it comes to safety and performance "a mans gotta know his limitations"
     
  10. francois100
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    francois100 Junior Member

    Thanks

    You are right I am just ambitious, I see double deck boats all over the show some of them build out of oil Drums, steel frames and cruising around with 20 plus people on them... I thought I could do the same but just do a decent job of it... I looked at pontoon designs, size and shapes and basically copied it... Some people are using PVC pipes... Where I live there is no designers, there are barley a shop but I will see what I can do, thanks for the advice and patience

    I admit i am a rookie and should probably not be fooling around with this..

    Thanks again.
     
  11. rwatson
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    rwatson Senior Member

    No, dont be too hard on yourself. The design is as good as I have seen for a newcomer, and the drawing skills you have acquired are very evident. What software do you use ?

    Wanting to do a better job is a good sign too, and will provide some usefull insights. I suspect that you can link up with a designer over the internet, so your geographical location is less important.

    Building out of drums and PVC can be fun, but putting 20 people on board a vessel ( especially with drink involved I bet ) opens up a whole area of personal liability in the event of mishaps.

    Who knows, if you get a good design worked out, you might have a usefull income earning hobby on your hands.
     
  12. War Whoop
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    War Whoop Senior Member

    Francois you have done some Stability work on that right? You have 4000 pounds running around 8-10 feet above the water line!
     
  13. rwatson
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    rwatson Senior Member

    yes, and in the event of some entertaining event or panic, all of them on one 3000 pound displacement float - boggles the mind.
    Plenty of examples at coroners courts all around the world.
     
  14. francois100
    Joined: Oct 2010
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    francois100 Junior Member

    Thank

    I am a designer for a process company, we do piping and vessels, autoclaves and so on, I use a verity of software, mostly cad and Inventor and some times UGS and Catia...
    You don't understand how mush I like to work with my hands, My last project was the CNC Machine witch was a grate success. The Beast is 6Mx3.5M. I cant wait to cut my boat parts on the machine..

    Regarding the boat, I think I must maybe get one of those house boat plans, the ones that have only one hull, I just liked the look of the 2 Pontoons, like a cat.. or I must stick to the Pontoons but forget about the top deck. Just like some of the pontoon boats on the net or the kit ones you can buy..

    After your mail I have bought a book that teaches you how to work out and design a boat. All of the right terminology that I see but don't alway understand. The Book Is called How To Design a Boat by John Teale.

    In one of my post a mentioned the pontoon sizes or show it via the drawing. The pontoon is 20 feet long and 32" in diameter. The boat with is 9 feet. The shape of the Pontoon is one I saw of a company that sells the kits (http://www.custompontoonboatkitsetc.com). I am going to forget about the top deck and focus on a normal pontoon. Is my Pontoon design sufficient or should I go bigger. It is still in design so I am very flexible and can change overall sizes and so on with out a problem. Would you like me to make a detail drawing of the hull or pontoon. I can show where the ribs and stingers wil be..

    Thanks again.
     

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  15. War Whoop
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    War Whoop Senior Member

    what speed range to these boats operate in?
     
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