battleship replica cruiser...critique?

Discussion in 'Boat Design' started by tugboat, Aug 29, 2012.

  1. tugboat

    tugboat Previous Member

    Hey all- wondered what you think of this quasi replica battleship?...think it could work as a small 2 person cruiser on the great lakes? I could tweak it- any suggestions on the tweaks? can be built in wood/ply/epoxy or light ga. steel (16 ga.) done stitch and glue or conventional light steel construction.
    tanks are located where the man is standing aft bow has a berth.

    stats:
    Volume Displacement = 59.7569
    Center of Buoyancy = 23.6106, 0.044214, -0.221839
    Wetted Surface Area = 200.427
    Waterline Length = 41.8188
    Maximum Waterline Beam = 5.9999
    Water Plane Area = 194.038
    Center of Floatation = 26.6147, 0.0439894,0

    loa- 47 ft
    max beam 8 ft
    power 36 hp diesel
    predicted speed- 13-17 knots @ 3300 rpm

    :) thanks!
     

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  2. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    It will have some stability issues
     
  3. tugboat

    tugboat Previous Member

    hi Steve and thanks--can you please elaborate?... I was thinking of adding lots of ballast ...like a sialboat hull..maybe a heavy keel...?

    p.s I liked your site...especially(and not surprisingly) the mini tug!

    Doug
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    5:5 Beam/length ratio, a few inches of draft and the rest of the boat (and it' mass) all out of the water. Yep, you'll have stability issues, without a 48" deep fin and big hunk of lead dangling from it.

    The idea can be done, but some things don't scale well, especially downward, such as people, beam and engines. There's a very nice Bismark that a fellow rides around in. It's scale, though has several modifications to make it stand up right. What BB are you going to build?
     
  5. tugboat

    tugboat Previous Member

    Thanks PAR, I appreciate your input.
    I thought a streamlined older style type destroyer type hull with a modest hp would be economical and relatively fast with that long waterline...Im guessing this wouldnt be a true planing hull but a semi-displacment although a fast one for that category. I had one calculation using a 40 hp steam engine and geared 0.5 : 1 to give a faster shaft speed - showed the hull might be capable of speed in excess of 18 knots at 1500 rpms. but required an lot of oversquared pitch on the prop. the tactical diameter would also suck with this hull, coming into port would require a bow thruster im guessing?

    intuitively i knew the beam to waterline ratio was like a 150- 190 or something...so I figured that there might be the possibility of the righting moment not being substantial enough and perhaps the initial satbility is off..although i couldnt give you the numbers on it. My thoughts would be to add a very heavy steel plate like a big half inch steel plate as a skeg--but again i doubt it would help all that much..and if I add more waterplane area or more draught, it slows the boat down, as does the added weight...

    its a no win situation.
    my thinking on this was since its almost flat bottomed that if the weight of everything was down in the hull it might overcompensate for the stability losses? like a barge hull?


    I am still building my tugboat. thanks for asking. pls forgive my ignorance here -I know you like to use abbreviations so im learning a lot with regards to that when i get posts form you--but what is a BB? I have never forgotten what an SOR is since you posted that one time...:cool::)

    I appreciate the opinion of experts..thanks Par. if your not too busy- do you have any ideas on how to redesign for better stability?..plumb sides maybe?.

    cheers!
     
  6. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    Make the bottom out of 3/8" plate and everything else foam core... especially anything above knee high. Stick a lead skeg on it for additional weight. Plumb sides will reduce ultimate stability unless you increase the freeboard. If you bump out the waterline beam to create the plumb sides that won't be so bad (increased initial stability) as reducing the shearline beam but either way... ultimate stability will remain the same or be negatively affected
     
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  7. tugboat

    tugboat Previous Member

    I hear you Steve- its too much work to invest in...- I just thought it was a neat design..IF i could make it work--down the road i might have tried a build...but --i did have the oversight of too shallow a draft for the boat--who knows maybe ill just look at scaling one down -or build a model just to see...

    again your input is always appreciated,...
     
  8. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member

    William/Bill Garden was in my area,and renowned for his many long and skinny boats.

    Perhaps one of his boats with a modified look would do...your local library may have one of his books.
     
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    My approach would be to design a stable flat bottomed hull and put a BB superstructure on it. I also wouldn't try to make it very shallow, instead placing much of her bulk as low as possible (especially crew and engine). From a technical stand point, she wouldn't be true scale, but she'd stand upright and look like an Iowa class (or whatever class). BB is the USN designation for battleships after the 1920's, the Iowa is BB-61 for example.
     
  10. tugboat

    tugboat Previous Member

    Thanks Par-- once again -great info. TBH - I dont know much about battleships--but they seem to be very seaworthy. I like the look of them--I am drawn to functionality in design rather than mere esthetics. I see the two as interconnected--functionality = a beautiful boat--of course-I could show you some butt-ugly tugboats-that i wouldn't take as a gift

    and my guess-is they perform about as good as they look...

    do you think flared sides with flat bottom?...

    or maybe plumb sides and flat bottom??

    I noticed today that a destroyer has about half its mass below the surface--i was quite surprised to see that...considering they are very fast and -im guessing they are probably quite agile vessels despite thier long waterlines. your advice is sound-and I might play with the design on rhino for a while--do what you suggested and see if i can come up with a float tank test model ...im big on this type of learning...did a lot with my sub models and learned a LOT of things through experimentation...
    oh btw! I havent got a BB in mind but - Ill look at some designs and then scale them and see how that goes...when i scaled down the subs - you are quite correct- they dont scale down well...
    regards
    Doug
     
  11. JosephT
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    JosephT Senior Member

  12. tugboat

    tugboat Previous Member

    "you sank my battleship!!!" :p
    was wondering when that line would come out...:D
    one of my pics posted here for the battleship is labelled just that!
     
  13. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    That's what the guys on the Bismark yelled "you spanked my battleship" . . .

    Battalewagons have so much boat in the water because of the enormous burden of armor, guns, ordnance and fuel they must carry. It takes that much volume just to hold them up. In fact, they aren't especially stable and they capsize pretty easily as a result.

    In this vain, I'd design a nice relatively narrow flat bottom skiff like hull, with a faux bulbous bow and everything, knowing she's not going to get over hull speed. I'd concentrate on the topside shapes, to offer the illusion of a Iowa (or what ever) class, with it's deck structures in foam. Maybe the whole bridge tower can hinge forward so you can climb in and roast in the afternoon sun, while peering through scale 6" square ports?
     
  14. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Last edited: Aug 12, 2015

  15. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

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