Design Assistance

Discussion in 'Boat Design' started by dragoon119, May 30, 2017.

  1. dragoon119
    Joined: May 2017
    Posts: 8
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    Location: Virginia

    dragoon119 Junior Member

    I am assuming by information you as asking for the SOR?
    Okay here is the information,
    The Length overall is 74'64"
    Beam 19'8"
    Draft 6'6-10"
    Mainmast is about 61' in height
    Mizzenmast is about 50-55' in height
    5 Rooms within the boat,
    1 Owners cabin
    2 queen suites/ or at the very least double bed suits
    1 double bunk room
    1 single bunkroom situated with a washing machine
    Each room will have private bathroom, except for the single bedroom.
    Single inline 6 desiel engine, however unlike the traditional method of having a propshaft. The desiel would preform four tasks. It would power three electric motors for use as bow thrusters and main prop. Finally act as a generator unit for the boat to charge the main batteries.
    Needs to hold 396 gallons of fresh water
    575 Gallon fuel tank
    If you want I could give you an approximate calculation of the sail area of the boat as well.
     
  2. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    The truth is that there is not much information you give us. It is necessary to know fundamental aspects, like type of navigation, speed, autonomy, regulations that must fulfill ....
    It is surprising that, for example, you know, even if it is approximately, the height of the masts without knowing yet the m2 of sail required.
    You should draw a General Layout plan to make sure that, at least, there is space for everything you want to carry.
    Do you have an idea of how you want the cross-section of the boat to be? Rounded shapes, knuckles?
    Do you know that you need to carry an emergency generator?
    How big have you planned for the gray water tank?
    What are the "hotel" services that the boat needs?
    Besides the passengers, do you need a crew ?. A boat so large will need several expert people to handle it, when sailing .....
    I do not continue, so as not to bore you but you should continue to define your boat in much more detail.
     
  3. dragoon119
    Joined: May 2017
    Posts: 8
    Likes: 0, Points: 1
    Location: Virginia

    dragoon119 Junior Member

    I do have an idea of how I would like the cross section to be, of which there would be 8-12 of them.
    An emergency generator is in the plans too, as well as a small amount of solar panels too which would be added later launching the boat and trouble shooting any issues from the sea trails.
    Yes I have planned for a grey water tank, but not its location as of let. I do know most of those auxiliaries will be below the salon, and or inside the engine room. Still thinking of exact placement to provide balance for the boat.
    Hotel services?
    No crew required, the boat should be capable of sail by 1-4 people.

    In what way do you want me to define the boat, in planned construction or planed features?
     
    Last edited: Jun 5, 2017
  4. TANSL
    Joined: Sep 2011
    Posts: 7,369
    Likes: 699, Points: 123, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    I mean to have perfectly defined the boat in terms of several fundamental aspects as, and I repeat, type of navigation, speed, autonomy, regulations that must fulfill .... Without having this clear, and I am not sure that you have it already ( you would have explained it to us if you knew), it is not possible to define a boat. I am surprised that you already know, for example, the draft without knowing so many other things.
    Regarding hotel services I mean everything that will make the boat habitable by the people as well as the spaces needed to accommodate it, to store food, drinks, air conditioning, bedding, etc. How many Days do you want to be without entering port?
    4 people to handle a 74' LOA sailing boat will require very experienced and efficient people or many automatisms or both at the same time. It would also be good to bring a good mechanic on board to serve as many engines. But that is you alone that can decide it.
    Yes, define the boat in planned construction will help a lot to know hull material, total weight, and some other things. And, of course, planned features is the first thing to be defined.
    Good luck.
     

  5. John Perry
    Joined: Nov 2003
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    Location: South West UK

    John Perry Senior Member

    I think it's not unreasonable to ask why large sailing yachts are not often designed with bilge keels, which I think is basically what the OP was asking at the start.

    I can think of a few reasons:

    Sailing yachts with bilge keels are usually designed with a view to drying out at low tide as much as reducing draft. A yacht that can dry out can utilise cheap drying moorings and is a bit simpler to lay up on shore during the winter. 74 foot LOA is quite a large yacht although still a long way short of superyacht size. The owners of such large yachts are usually wealthy enough that they are not particularly concerned with saving money with a cheap mooring - they are happy to use only the more expensive all-tde harbours and marinas. If they are not using a harbour they are happy to anchor in deep water someway offshore since they probably cary a substantial powered tender to use to get ashore.

    Also, if a large yacht does dry out, even with bilge keels, the risk of damage and the cost of consequent repairs is disproportionately higher than for a smaller and lighter vessel. We are quite happy to ground our 15 foot LOA cruising sail boat on most harbour sea beds, although even with that size of vessel one needs to check for isolated rocks or heavy mooring tackle that could damage the hull when taking the ground. Owners of larger vessels need to be even more careful - an analogy is that a mouse can land safely from jumping from many times its height where as an elephant would certainly kill itself doing the same.

    Bluebird of Thorne (google will find it) was considered in its day to be exceptionally large for a bilge keel yacht but at 54 foot LOA it was considerably smaller than you are considering. This was a steel yacht, not plywood as you are proposing!

    If relatively shallow draft is a requirement for a large sailing yacht then a lifting keel of some kind is a more likely option than bilge keels - this will potentially allow a smaller mininum draft than bilge keels whilst probably giving better windward sailing performance. Indeed, at one time I was involved with the design of an approximately 150 foot LOA sloop of aluminium construction which had a lifting keel to reduce draft, it was never intended to intentionally take the ground. Interestingly the lifting keel on this yacht was of neutral bouyancy - with that size of vessel just the form stability will support a pretty powerful rig under most conditions and if it is really blowing it was envisaged that the boat would be in harbour or under power.
     
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