Aluminum boat..Help!

Discussion in 'Boat Design' started by ringoo83, Jan 27, 2009.

  1. ringoo83
    Joined: Sep 2007
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    ringoo83 Junior Member

    I'm designing 8.5m aluminum boat, could someone tell how many water tight bulkheads it have to includ & the locations, the deck height is 700mm.

    Could anyone post a link of websit which shows structural details of aluminum boats with this size.

    Thanks in advance
     
    Last edited: Jan 29, 2009
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Which Class and Flag is it too...if any?
     
  3. ringoo83
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    ringoo83 Junior Member

    It's not decieded yet under which class flag will be registered
     
  4. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    That will influence how your design should be. Since it will either have to meet regulations of some kind (may be not??)...need to establish this first before you rush off trying to locate the WTBs.
    If you do not know the criteria which the vessel must satisfy, why draw it up at all?
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    You are not designing a 8.5m aluminum powerboat. What you are doing is drawing sketches of 8.5m boats, scaled down to a handy size. This is a long way from designing a vessel.

    Without the engineering/hydrodynamic principles and concepts firmly grasped in one's mind, you would be best advised to get a real designer to draw up your boat. You could also purchase plans and make modifications (within reason of course) to suit your desires.

    I mean no disrespect, but judging from your few previous posts (of which, just like this post, were filled with very basic and elemental design or engineering questions), you do not have a firm grasp of the things necessary to design a boat. This requires education and considerable study. You can do this on your own, but it requires a very diligent person and would be the rare exception, unless of course it was across many years of industry experience.

    Courses are available as well as a few correspondence classes. You'd be well heeded to avail yourself of these courses and continue your personal studies of the differing related subjects.
     
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  6. Guest62110524

    Guest62110524 Previous Member

    if you want to email me, I will draw the structure for you, see my gallery, wont cost you anything, have a design that size too, that WILL cost you a quid or two, with developed plates
    do yourself a favour, check out the profiles of people here, their rep points(like Par) and beleive half of what you see and nothing of what you hear
    if they have no gallery and no profile then usually they are bluffing! good luck you are at least enthused
     
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  7. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    PAR
    well put!
     
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  8. ringoo83
    Joined: Sep 2007
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    ringoo83 Junior Member

    Dear PAR

    I respect your opinion I don't have that experincein in the field of designing planing hulls, but I have read many things that I think they would help me to start in,for instance: Dr. Savitsky's articles, The elements of boat strength, rules for high speed craft (ABS, LR)....but I'm confused because of many things, for example ABS rules for high speed craft are limited to boats with L>12m, and I compared the scantlings of many boats with what they would be when using the book (Elements of boat strength) I found that it's not giving accurate results......etc

    Anyhow, I'm studying naval architecture at the moment..and I think I have the requird knowledge to understand and use many engineering priciples..... but Still I miss the experince you have......for this reason I'm asking your help. Regarding your comment and mentioning that the top file is only a sketch, kindly be informed that I'm drawing the structural details and I'm using Autoship package (now autostructure). I would like to send you dxf file to check my work and assess it if you accept to share me your opinions and advise.

    Thanks
     
  9. ringoo83
    Joined: Sep 2007
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    ringoo83 Junior Member

    Thanks for encouraging me

    I checked ur gallery. impresseive !I'll follow your suggestion & I'll contact you sooner.
     
  10. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    At least three...
    Engine
    Main
    And Bow
    Also perhaps fuel tanks in hull.
    Is a flotation required?
    What kind of boat?
     
  11. ringoo83
    Joined: Sep 2007
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    ringoo83 Junior Member

    This is like a small patrol boat with outboard engines

    I already made 3 bulkheads, the problem is stiffening these bulkheads, cuz they are small, stiffeners lengthes are not more than 350mm.

    Any suggestion will be appriciated
     

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  12. ringoo83
    Joined: Sep 2007
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    ringoo83 Junior Member

    This boat has a cuddy

    It has 2 side girders (5mm thickness)
    10 transverse frames (800mm spacing x 5mm) (frames 1,5 and 8 are W.T BHDs)
    Deck height is 700mm
    Each side has 4 bottom long. + 2 topsides long.
    Each side of the deck has 4 stiff.s
    Bottom plating 6mm
    Topsides & deck 5mm
    cabin & cuddy 4mm

    To tell the truth I selected the scantlings based on similar boats, rules (ISO & LR & DNV & ...) give different figures (about 1mm difference).

    I never calculated the pressure to define the scantlings.

    I only used flat bars for long.(Bottom& topside 70x5mm Sp:200mm)& (50x5 Sp 190mm)

    forward of BHD 8 I used 3 small girders instead of long.

    Any advice regarding stiffening the BHDs & the scantlings of the Bottom/topside/ deck longitudinals will be appriciated
     

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  13. ringoo83
    Joined: Sep 2007
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    Location: kuwait

    ringoo83 Junior Member

    Loads on shell envelope

    I have just finished of calculating the pressures on the shell envelope, used LR rules:

    hydrostatic pressure ( bottom ) =1.8 [KN/m^2]
    hydrodynamic wave pressure ( bottom) = 16.02 [KN/m^2]

    Relative vertical motion Hrm = 0.2633
    Vertical acceleration av=2.526

    The pressure acting on weather & interior decks in planing mode= 20.176 [KN/m^2]


    I don't know if these figures are reasonable; Could anyone tell or suggest?

    Thanks
     
  14. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    Post measurement in inch fractions for me. I dont do metric.
    But right off this boat looks like it is designed for wood not Aluminum
    Aluminum structure is more like a wire cage otherwise it needlessly heavy. It is made of a lot of Ts and welded stiffeners. Think of a wireframe of aluminum bars covered in aluminum sheeting.
     

  15. ringoo83
    Joined: Sep 2007
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    Location: kuwait

    ringoo83 Junior Member

    Inch

    Inch
    It has 2 side girders (0.197'' thickness)
    10 transverse frames (31.50'' spacing x 0.197'') (frames 1,5 and 8 are W.T BHDs)
    Deck height is 27.56''
    Each side has 4 bottom long. + 2 topsides long.
    Each side of the deck has 4 stiff.s
    Bottom plating 0.236''
    Topsides & deck 0.197''
    cabin & cuddy 0.157''

    To tell the truth I selected the scantlings based on similar boats, rules (ISO & LR & DNV & ...) give different figures (about 1mm difference).

    I never calculated the pressure to define the scantlings.

    I only used flat bars for long.(Bottom& topside 2.755"x0.197" Sp:7.87")& (1.968"x0.197" Sp 7.48")

    forward of BHD 8 I used 3 small girders instead of long.

    Any advice regarding stiffening the BHDs & the scantlings of the Bottom/topside/ deck longitudinals will be appriciated

    hydrostatic pressure ( bottom ) =1.8 [KN/m^2]= 1800 pa
    hydrodynamic wave pressure ( bottom) = 16.02 [KN/m^2]=16020 pa

    Relative vertical motion Hrm = 0.2633
    Vertical acceleration av=2.526

    The pressure acting on weather & interior decks in planing mode= 20.176 [KN/m^2]

    I tried to do it like a wire cage but I was worry about the total section modulus in case I want to class it, so I replaced 2 bottom longitudinals with 2 girders, and I supported the fore part with some small girders (BKTs), the deck is stiffened with FB, only the the portion where the cabin sides stand was supported with T badrs still I'm worry about building this structure, I noticed there is no enough space for welding !!! Any suggestion!!! cheched alot of aluminum structures, not all of them were wire cage built, check the photos.

    I calculated the structural weight, i guess it will be about 2200 kg (4850 pounds)


    Appriciate any comment- suggestion
     

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