Aluminum Offshore Fishing Catamaran CNC Cost?

Discussion in 'Metal Boat Building' started by jwells11, Apr 1, 2020.

  1. jwells11
    Joined: Apr 2020
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    jwells11 Junior Member


    Good info....

    I heard some crazy numbers on CNC costs........Numbers that will put CNC costs higher than the sheets of aluminum themselves. Is this true or should I expect much much lower costs than that?

    I imagine a 30ft sheet gets heavy though.

    I have a 50hp tractor w/front end loader.

    If that dosent do good enough, I will build a I beam winch that slides(dont know what they are call).

    40k after thinking and looking up what I wanted is a low.

    Thought about it with some research this morning, and for 24inch simrad and radar, Im at 10k plus already. 5k in stereo to do right at least, 5k in good llebroc seats, $3500 in Dometic AC, and then you got general hardawre, auto pilot, good bottom scanner, upholstry, and possibly a windless(I want a flat deck up front for now toe stubs so still debating on windless)

    Then glass although I have a good friend that will cut me a deal on that. No labor no mark up most likely. But still......

    Will be simple as possible though. Im a utility person.
     
    Last edited: Apr 2, 2020
  2. jwells11
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    jwells11 Junior Member

    Time and I grew up in a sign shop and just down imagine the lines being accurate. I did think of this though

    If I do another boat, it will be a hybrid bay catamaran. and will probably use this and make a cardboard model. be free and make sure I have the demensions right for I dont havent found a CAD for one.

    Only one manufacturer making a catamaran hybrid bay worth doing(aka CAYO)

    @Barry As far as cnc costs I heard some crazy numbers flying around on CNCzone.

    Thats why Im concerned that CNC work will cost 20k alone on this. Doesnt seem like it should cost more than the metal though
     
  3. Barry
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    Barry Senior Member

    It is unlikely that the cost for CNC work will be that much. We had our own plasma table so I cannot comment on current costs. As per my earlier email, contact Specmar or those companies that they recommend as they will have experience with pricing etc.

    A good quality table will do about 80 inches of cut per minute in 1/4 inch with an AIR-AIR gas mix. So to make a 20 foot cut would take about 3 minutes. As most of your cuts will be slow curved cuts the machine can pretty much set up to
    run at a high rate of speed. If you have a lot of tight corners, and there will be some in the frames, you might need to turn it down 40 ipm.
    I would expect that it should not take more than 3 -4 hours of cut time and even that seems high. But positioning each sheet does take time.

    There a couple of things to consider
    1) If you have someone design the boat that would be one cost.
    2) making the dxf file, ie the cut file can be another.
    3) almost all good CNC machine programs will have a nesting feature where you can enter the data, ie the shapes and the quantity and then enter the size of sheets and the number of sheets.
    The program will then nest all the parts to minimize sheet usage. This is such a huge savings as compared to starting with pattern and trying to get the best bang for your buck. Another good feature is that for aluminum you can use
    air for both the cut and plasma functions, which does not cost anything

    Cutting of aluminum
    The best way for larger pieces is a 7 1/4 inch circular saw with a 60 tpi carbide blade, Freud or Diablo, cross cut grind ( don't try to skimp here and buy offshore junk) You might need 2 to do a 40 foot boat, maybe 3.
    Buy a good saw, Milwaukee was our choice. We had tried Makita and Dewalt but they did not last as long.
    Do not use wax or oil or anything during the cut as it will impact the integrity of the weld. Clamp everything well. AND ALWAYS WEAR TWO LEVELS OF EYE PROTECTION Safety glasses and a face shield. The chips coming of these cuts
    are HOT and I am convinced that they can turn 90 degrees within 2 inches to get underneath a single barrier. (they probably are bouncing at 90) And the cut process is loud, extremely loud, buy a top level set of muffs.
    As aluminum is tougher than wood, you need to ensure that if the saw bucks back at you, that the blade path does not cross a member of your body.

    You will need a circ saw to back cut butt welds on sheets and to cut back any welds that are continuous or where they meet each other to get rid of any craters cracks which sometimes you do not see easily
     
  4. Rumars
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    Rumars Senior Member

    CNC costs are determined primarily by the time on the machine, then machine size and type (asuming nesting is already done by the NA). Your basic need is a 3-axis router as is commonly used for plywood, the problem is most of those have 4x8 beds. A 5-axis machine can already put in all the bevels, but only if your NA draws them in, which is a lot of work for what you are paying. Waterjet is faster then router, but usually more expensive. You will not know the needed machine size until you know how you buy the material.
    Finding someone with a 12ft long 3-axis router and a good price should not be difficult, if not you can build one yourself there are kits for them.
    Cutting by hand is accurate enough. The full size plans stay glued to the plates and you can cut wide and adjust by sanding.
     
  5. jwells11
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    jwells11 Junior Member

    I see a ton of people using square tubing stingers on the more straight part of the hull and then using plate on the curved parts.

    Whats the purpose of this? Why not run the entire length with cnc plate as stringers?

    From what I plate read is that square tubing is not that much stronger and more expensive to use than plate. considering that you dont have lateral/side force.
     
  6. Barry
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    Barry Senior Member

    A general statement that square tubing is not that much stronger than plate requires many more parameters as height, width, area distribution around the neutral axis OF JUST THE TUBING compared to JUST THE PLATE.

    When you weld/attach the tubing to the plate, if you have enough weld to carry the shear flow stresses, the outside skin becomes part of the cross section. Ie the bending strength is stronger
    than just the square tubing or plate plus say the bending strength of the plate. When welded the components act as a single cross section which can increase the strength of the pair significantly.
    Normally, (with some other considerations ) say your stringer spacing is 12 inches. ( and for the discussion, the hull plate is at the bottom) It is a generally accepted design practice to take half the distance to the next stringer in each direction
    and that will be the lower cross sectional area/flange of welded profile. Then the upright section can be the web, ( for this example say the height of the web is 4 inches) either singular plate or double tubing, and then the upper flange ( for this example say the width of the upper flange is 2 inches) will be the third component.
    So when welded together then you have a plate formed into the web and upper flange as an angle then you have 12 inches of bottom plate forming the lower part of the cross section.
    As the lower flange length is 12 inches you do not need more material in this area to add strength to the stringer.
    If you weld in a square tubing though, the lower part of the tubing will be welded to the 12 inch wide flange (hull bottom) so you are providing and paying for this redundant material. If you need to bolt something through a piece of tubing
    which normally would be then half the equivalent thickness of say the formed angle, it can become a bit of an issue as the bolt can deform the often thinner tubing side wall.
    Additionally, you really don't want a lot of surface to surface contact of aluminum in a salt environment due to crevice corrosion. It may not be a big problem but why introduce this into your boat when the scribed/fitted plate option can be stronger for the same weight, allow better bolting ability and reduce chances of corrosion.

    We always used formed angle. Formed because due to our deadrise, the vertical webs could be formed so that the tops of the angle would form a flat to bolt the floor onto. If you do it with say 2 or 3 inch tubing, the only way then to make a flat
    attachment point for a floor is to add more material onto the tubing. Seems to me you would be going backwards.

    ( some very loose assumptions were made here, as you more than likely would not use a 12 inch measurement for calculations for the bottom hull flange, 6 inches either side of the vertical web if the top flange is only 2 inches)

    The main summary is that if you use square tubing welded to the hull bottom, you are spending more money with the extra weight for material that is not significantly contributing to the strength of the floor,web and upper flange combination
    With an angle ( some people use T's) for less weight you can get more strength
     
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  7. Mr Efficiency
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    Mr Efficiency Senior Member

    Being paranoid about poultice corrosion, I'd be leery about box tubing in contact with the skin, seems like a potential hidden problem.
     
  8. jwells11
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    jwells11 Junior Member

    @Barry

    Talking Corrosion, how do y'all better ensure that the boat doesn't experience electrolysis?

    I dont plan to leave in water but is there any common practices to prevent this.

    Insulated cable trays and other solutions to help prevent it.............

    Working in HVAC for a bit taught me one thing. If its loose and there is vibration, it will eventually wear a hole in it. Maybe 2 months, maybe 6 years.
     
  9. Barry
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    Barry Senior Member

    A galvanic protection system like Mercathode but there are many more that impress an appropriate charge on your hull to prevent metal transfer powered by your boat battery, an adequately designed anode bolt on system and
    as important a device that checks the polarity of the shorepower coming into your boat when at the dock.
     
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  10. jwells11
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    jwells11 Junior Member


    Now to paint

    How much is it to have someone do it?

    Can it be done adequately by myself?


    ****No anti foulant needed
     
  11. jwells11
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    jwells11 Junior Member

    @Barry

    Also considering painting below chine, tunnel, and above rub rail.

    And wrapping the "Slab". For two tone paint job
     
  12. jwells11
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    jwells11 Junior Member

    also considering white slab wrap, polished aluminum look, and seadek
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    You should be busy till 2025 building this thing, Do you really have to travel 150 miles to get to fishing grounds ? That is really an enormous distance for a day boat, the fuel bill would be "catastrophic", and even in a relatively soft riding boat, gunned along to ensure a longer period of fishing time, than travelling time, one would be thoroughly shaken up, if not stirred, at the end of the day. Whatever happened to the simple life ! :D
     
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  14. Mr Efficiency
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    Mr Efficiency Senior Member

    When power cats became popular in Australia back in the 70's, most were glass, but inevitably alloy was experimented with, the limitations of shaping with developable surfaces were not really an issue as much as with monohulls, performance wise, but many of the early alloy boats experiences structural problems, a cat not being a natural "shell" like a monohull. I would say structural design errors will show more readily in stressed areas of a cat, as the two hulls are sometimes working at cross purposes, so to speak. I would go with what is known to work, not experiment.
     

  15. jwells11
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    jwells11 Junior Member

    140 miles each way. Venice, La is about 120.

    Hence the reason charter captains in Venice have 42ft catamarans that will do 80+ mph.

    World Class fishing all be it.

    if I CNC and have someone help me weld I don’t think it will take that long.

    But if it takes that long it beats spending 400k for a used contender or 750k-1 million used on the a similar setup.

    yes I imagine a custom pilot house would be closer to 1 million
     
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