super custom 70+ft cat. need feedback

Discussion in 'Boat Design' started by Vitmus, Nov 10, 2016.

  1. Vitmus
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    Vitmus Junior Member

    A friend of mine was looking at a rather large endeavor that I'm thinking pretty hard about. He told me to join and get some opinions, hoping a naval architect will look at it! I have several steel boat building books and am a very accomplished machinist/fabricator. Now I'm looking at changing gears a little and starting a large boat build. There is a skp (sketchup) file to look over in the bottom of the post. (you can download sketchup for free to view my files. 1mm = 1 inch in my drawing).

    A couple notes, the hull will have a 1ft radius on the sides continuing to the front where there will be a small bulbous nose. I have a lot of planning work to do such as figuring out all of my weights in quarters and comparing to the various buoyancy of the hull design. It is supposed to sit flat and remain the same while driving, just piercing the waves. Should ride pretty smooth. it will displace 60 tons when done and have a draft of about 4.5 ft. Plan to push it with twin 220 hp volvos. more hp than needed. but just in case... Estimated hull speed of 11 knots and top speed of 14 or so. have fun with it.
     

    Attached Files:

  2. Squidly-Diddly
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    Squidly-Diddly Senior Member

    post actual pics, not a zipped file.

    1/2 the time I can't figure out where the unzipped file runs off to.
     
  3. Richard Woods
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    Richard Woods Woods Designs

    try "printing" it as a pdf then everyone can see it whatever software they have installed

    RW
     
  4. mydauphin
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    mydauphin Senior Member

    Any boat over 50 feet, please get professional help. Everything is a lot of money. Not something for even inexperienced professionals. Lots of money... even if you build it yourself. It is huge. Mistakes can be very expensive. And a 70-foot boat should never be your first boat build. And once you build it, you will even have a hard time finding a dock for it. I know these things, I have one. Pain in the a...
     
  5. kerosene
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    kerosene Senior Member

    For general reference it woulf be good to get honest answerd on following:
    A) The owner'd/builder's boating experience. What kind of boats owned and maintained previously
    B) even rough estimate of budget for the project
    C) any previous boat built

    These will help any professional answering to gauge what kind of project are we talking about. And as said pictures would help hugely. When asking for free advise you need to make it easy if you want good responses.
     
  6. Vitmus
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    Vitmus Junior Member

    I have had several boats and still have several. Im currently in the master berth of my Carver 466. I understand docking and maintenance and the 300 to 500k its going to cost me to build it. I own a machine/fabrication shop. I have a LARGE shop at home that is fully equipped with cranes and welders, Lathes, mills all that. (excess equipment from when I bought current business after starting my first one from scratch). I have spoke with my current marina and docking won't be a problem. $10 a foot on the inside of the breakwater. Don't really plan to be at the dock after I build mine. On the hook. Local or afar. Roof would be covered with solar, so no need for any hookups. I do understand the scope of the project, and am ready to take it on.
     

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  7. Vitmus
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    Vitmus Junior Member

    The hulls would have a 1 ft radius on the sides that would go to the front, but it would be a flat displacement hull. running twin volvo 220 hp diesels. all the calculators that I have found show it needs about 200 hp to get it to its 10.8 knot hull speed. Here are some xray pics of the interior on different levels. NOTHING is in stone, just planning right now. THANKYOU for any input!
    Oops, to much data. over my limit. will have to try later or?
     
  8. Vitmus
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    Vitmus Junior Member

    I plan to go to a naval architect before I order materials, just looking for some thoughts or red flags besides the cost and scope at this point. Thanks for your concern, it's duly noted.
     
  9. Vitmus
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    Vitmus Junior Member

    I'm trying... I got it saved as a DWG. but I'm out of space to upload it. How to get more space available? Don't want to delete pics, just got them posted. Thoughts...
     
  10. mydauphin
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    mydauphin Senior Member

    Good Vitmus, glad your not a total dreamer like a lot of people that come here. Let's talk build material.... Fiberglass,composite, steel or aluminum. $300k might get you hull and propulsion, and another $200k for inside. and depending where you build it rent can be a couple bucks a month. I built a 70 foot mono hull and originally had idea of using outboards, but doing calcs, I could not fit the right props in the motors to be efficient.
     
  11. Vitmus
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    Vitmus Junior Member

    mydauphin,

    I choose steel. Due to the amount of steel that we buy on a regular basis, I can get a really good break on it, and I'm used to working with it. All the way from high end damascus that I have forged, to building custom 18 ft truck boxes with drag systems out of stainless. I may be forced, weight wise to use aluminum for the super structure, but that will come down to all of the weight calcs. I also thought about the outboard, more for a test than anything, just to like build one hull, fit it with an outrigger so it doesn't tip over, fill it with the appropriate amount of water to equal the final displacement and see how much HP I really needed and how it performed, but have found some online calculators that have confirmed my hp and prop needs. Hope to build most of it in the Tricities (wa.) area. Cheaper labor rates for hired hands and lower rent costs. Then float it down the Columbia River through the locks to the Ocean. Closer to my home also. It's hot and dry here in the summer, will do the woodworking and more detailed metal work at my shop in the winter months. Any input, thoughts on my hull design. The water line will be two feet below the V in the nose of the hull. Should cut right through 4 to 6 ft waves with hardly any movement or spray. (I was out this weekend and got HOSED. Top was buttoned up, but we still had a lot of water in the flybridge area. Canvas and zippers only block so much. The forecast was wrong! Instead of 15 knot winds, they hit 40! We took the carver on a 2000 mile trip from Bremerton Wa. to Juneau Alaska this summer and that trip taught me a lot about what I wanted in my "forever" yacht. Like a sealed top without canvas! So here I am, about to take on my biggest challenge yet.)
     
  12. TANSL
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    TANSL Senior Member

    It is only a supposition since, of course, I have not made any calculations about it, but I would say that the submerged volume of the hulls could be insufficient for such a large steel ship.
    But, of course, that and many other things are what a naval architect should check. It would be good to do it from the early stages of the project.
     
  13. Stumble
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    Stumble Senior Member

    I am with Tansl, that is a whole lot of steel on very skinny hulls. Second, the hp predictions are all wrong, with long narrow hulls your hull speed will be far in excess of 10kn.

    Frankly I think the next step is to find a NA with experience in large metal cats and speak with them. And I really doubt that $500k is enough to pull this off. You can probably get a hull and propulsion out of that, but that still leaves outfitting, systems, and interior, decorations... I am thinking you need to be closer to $1M to make a fair shake at it.
     
  14. Vitmus
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    Vitmus Junior Member

    I calculated the volume of the hull (not including the loss of volume from the radius on the bottom corners) to be able to float 120k lbs at 4 ft of draft. So I should be able to float it with the 4 ft stated, possibly 5 ft. with the radius taken into account and will I really be able to build it and stay under the 120, 150k lbs mark... 2500 lbs equals 1 inch of draft. Originally I got a price quote for enough 1/4" plate to make 2-80ft long hulls 5 ft wide and 10 ft tall. It weighed 40k lbs. for $20k, but since then, I have found that 3/16" is sufficient (that cuts it to 30k) and Im not going 80 ft, but the interior structure, decking and super structure weren't taken into account. Its all pretty open though and the engines aren't that heavy, so I "think" I can make it.

    I agree, I should exceed 10kts pretty easy, that number came from a mono hull calculator. Maybe I'll end up with 5 ft of draft. Need to see what the calculation for the resistance for the wetted surface drag is. Do you see a problem with the wave piercing design??? I really want the steel hull for its forgiving durability (dents don't equal leaks, reinforced bow area 1/2" plating added for first 5ft or so) The narrow wave piercing is so that if I hit a log or sticks, they would travel up and slide off the sides, not down under the hull into the props. The displacement hull design, because I don't plan to be in a hurry. Speed cost money! My 25 ft baja with a single 454 running 45 to 50mph around the San Juan Islands in one 6 hr trip, took as many gallons as my carver 466 taking about the same trip over a nice relaxed week.
    Does anybody have any thoughts on the overall look of the vessel? I don't want to end up building this and ending up in the ugly boat forums... Note: there will be a few less windows up front, that was ease of drawing. There has to be some structural support up front besides just the glass. Bound to take a wave at some time... There will be some windows inside and outside on the lower berths as well as some in other hull areas, for some natural light in case one must tend to some chores and to balance things out.
     

  15. mydauphin
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    mydauphin Senior Member

    Unless you are into ice breaking, especially on a cat I would go with Aluminum, or at the least the superstructure which is pretty big.

    When building a boat hauling around AL is a lot easier than steel. Yes, it is a bit harder to weld but it makes up for it in easier to cut, and smaller cranes. If you go with AL you will save 100k lbs and 2 feet of draft, think about that.

    On looks... I don't like the back. It looks like a huge boat for one bedroom, one bath and kitchen. Not sure if I understand your hull design, Almost feels like a swath. What is Water line length, are you including the overhanging platform in 70 feet?

    Can you post a diagram with measurements?
     
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