Affordable, long-term liveaboard?

Discussion in 'Projects & Proposals' started by Filmdaddy, Aug 4, 2005.

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  1. NoahWannabe
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    NoahWannabe Junior Member

    Energy

    I have heard of "Physics for future Presidents" by Richard Muller. ;) It isn't that presidents don't have good information, the problem is that most presidents don't have good constitution and political skills to solve our energy problems. Coal/NG power plants are cheap to build, more profit and no protesters.

    Bill Gate was promoting certain nuclear power plants for a while in order to reduce carbon emission, but he went quiet after Fukushima. If we can operate dozens of nuclear submarines and nuclear aircraft carriers, then we can operate safe, non-polluting nuclear power plants. But it would be too much to expect a logical, scientific energy solution from majority of public and our politicians.

    I am hoping, algae diesel would be available in a decade. Hydrogen production from nuclear and solar makes sense if total non-emission is required. Algae or bacteria derived hydrogen production would be nice. Tesla Model S looks pretty good. Mass produced electric cars with good fast charging station network can work for most of us in near future. It just requires much green backs. Near term, one of the plug-in-hybrids look real good. Using ICE (Internal Combustion Engine) and electric motors make hybrid cars to accelerate quite quickly too, but Audi TT would be more fun.

    I doubt we will run out of oil anytime soon. Easy oil in shallow depth is probably gone, but the current issue really isn't available oil but emission-free energy. How did the crude oil created? I doubt they are from dinosaurs, many astrophysicists believe the crude oil is made through some kind of internal planetary mechanism then rises to crust.

    I have not heard of successful clean coal yet, even with closed loop carbon capture, it seems to be difficult to build large scale carbon storage facility that doesn't leak. Where could I find some good read on clean carbon? It is difficult to find good technical development in seas of marketing pieces and mis-informations.
    Yup, Germans and Japanese used coal-diesel and charcoal-diesel fuel during the WW2.

    Why do I sound so disdained with "Extrem Environmentalists"? When they start discussing population reduction as a solution and how they became a lesbian to help that goal, I knew I was in a wrong crowd. They would never volunteer to be the part of initial population reduction or give up their jet-set life styles. They need to live long and travel to educate ignorant masses.
     
  2. Sailor Alan
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    Sailor Alan Senior Member

    Unfortunately the copper needs to be absolutely pure. This is one of the issues with nuclear engineering, contaminants of any kind can destroy (sometimes literally) your work. For example, i was once party to a breakthrough experiment in Nuclear physics, but it was being bad mouthed by American research groups as not working at all. We were certainly puzzled, as we could make it work easily. Remember air travel was slow in those days, and photos traveled by post. Eventually an English group realized that we, like them, used stone lab benches, and the Americans wood. The carbon in the wood was absorbing neutrons (carbon is a nuclear moderator), and simply preventing the process from working. The Americans had to back down (which they did graciously, and very generously) while we all learned a valuable lesson. This was one of the reasons they were so generous with resources, embarrassment.

    The pure copper can be recovered because it is pure, and does not contain beryllium et-al. These elements pick up radiation with a long half life, and so we would be back to nuclear waste. In some ways your reaction was exactly the same as people wanting to ‘improve’ the original development, which simply crushed it under the weight of ‘improvement’.
     
  3. Sailor Alan
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    Sailor Alan Senior Member

    I think empennage drag is always a bad thing. It is the drag of the underwater propulsion installation, i.e. shaft, bracket, rudder, propeller, propeller hub etc, including the shaft and gearbox on OB’s. Even today, people try to reduce the number of propellers, ie 2 X 150hp OB’s will have higher drag, and therefor poorer economy that 1 X 300hp OB, all other things being equal. Some choose two OB’s for redundancy, some because they might be cheaper, some because 300hp outboards are not available yet?

    A bad situation is a stopped propeller for drag. Running it slowly, feathering it, or folding it all help, but best of all is simply retracting it out of the water. This is one huge advantage of an outboard.

    As regards directional stability. A jet boat with NO empenage, rudder etc, swings its stern around the front of the boat, the center-point of a turn being near the bow. With power off, they do not steer at all. A long keel power boat pivots about the center of lateral area distribution, more or less, and usually depends on skeg or keel size and shape. I'm sure Yobarnical can tell some horror stories, but most of his vessels would have reasonably square underwater side elevations, and so turn about their (relative) middles.

    I wish you had shared your catamaran with detachable center hull idea earlier, it clarifies quite a few things. That do you think about Wharram’s products, infinitely self reparable?
     
  4. NoahWannabe
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    NoahWannabe Junior Member

    40' Ocean Cruiser

    I think I am stuck on 10-12:1 B/L Ratio due to two reasons.
    1. As mentioned load carrying capacity. Not enough buoyancy volume and too much structural weight to make the boat rigid, unless kevlar or carbon composites are used with foamcore.
    2. 20:1 BLR would have too much wet skin drag for low speed displacement efficiency. Certainly for 40' cruiser, but tremendously for 26' cruiser would spend too much energy overcoming WSA drag. Sailing in most wind condition would be near impossible with low CE single handed sailing rig.

    Cruiser speed performance requirement: 8-12 knots cruise, 30 knots for emergency. SOR, Project Scope, Product Requirement, et al is to help us focused on target design rather than what is available.
    1. Very stable boat (condomaran stable) with 8-12knots cruising speed and 25-30 knots emergency speed to outrun weather (probably not real pirates). So, I am sticking with this as a target for now.
    2. Unless I decide to have multiple boats for each water type and region, I want to transport boats to each water without traveling to Panama or Cape Town. Hence the 40' length and 8-8.5' beam, or some modular design that can be transportable.
    3. Displacement: This is still up in the air, but 4000# light ship and 8000# loaded ship seems like a good starting point. My current fishing boat has 9500# towing weight.
    4. Propulsion: Fuel efficient power motoring and reasonable sails for good sailing. 8-12 knots cruise requires above hull speed and it can be done with 10-50 HP motor(s). 30 knots power will need ~300 HP and some foils to help semi-plane. Under sail, 6 knots is doable (hull speed) and 8 knots with some help from the electric motors or from strong winds when available. Upwind will be motoring.
    5. Fuel should be gasoline (petrol) AND diesel. Gasoline for emergency OB, and back up for diesel. Diesel would be my preferred fuel for cruising. Best setup would be a small diesel engine (~20 HP) to motor sail and also connected to an inverter (alternators) for electric generation.
    If I understand refinery process properly, then diesel should always be plentiful. I think the reason US government (especially CARB) is so bent on discouraging diesel engines in general is due to current environmentalists' belief that diesel fume is a single worst pollutant for our air. I think it may be valid in metropolitan area where micro-particulate is a big concern for lung related disease, but it has to be thousands of times better than smoking. Out in the ocean with thunderstorms, I think that cannot be an issue. They would have to get rid of bunker-C oil burning ships first. And, I think we will have multiple peak oils. The first peak oil was in Pennsylvania in early 20th century.

    The 40' offshore cruiser trimaran would be something like this:
    LOA: 38-40' Main hull (Vaka) and ~24' Amas
    BOA: 8.5' Trailer (24' cruising)
    Dry Boat: 4000# with motors
    Cruising Displacement: 6000# with 1/2 fuel
    Maximum DWL 8000#
    Motors: 300 HP OB + 20HP diesel engine + 2x10 KW electric motors
    Power Generators: 2KW solar, 12KW inverter, maybe a VAWT wind generator
    Sail: 800-1200 SqFt lug yawl
    Material: Marine plywood-epoxy with fiberglass reinforcement. Cedar strip for complex curves. Poly/nidacore cabin structures.

    - 300HP OB on main hull, and diesel generator on main hull
    - Electric motors and battery in amas
    - Extra fuel storage in amas in fuel bladder/ spare tanks
    - possible single berth in amas
    - water catchment rooftop and a small water maker
    - Main hull shape: dory (dory detroyer without the bulb), Bwl <40", Boa 8'
    - Amas hull shape: deep V (50* deadrise), Bwl <12", Boa 30"

    300HP probably is enough power to get the boat upto 30knots with enough lifting surface, I need foils. Foils in amas and vaka stern to lift enough to utilize dory flat hull in good AOA and prevent transom squatting, but not like AC72. Comfortable stability.
    I am all for Banka outriggers below waterline, but above the waterline, I want to carry the dory shape again for additional buoyancy.
    Parachute sailing needs more research to get full comprehension. It is my lack of familiarity with parasailing that prevents me from doing this. It is very tempting to not have tall sailing masts. The short mast is good for lifting and instrument mounting. I will miss sail steering possibility though.
    I am a west coaster fisherman, no fishing chair is needed. Although comfortable fishing chair to fight sailfish for 8 hours bring smiles :)
    My preferred bow and stern shape is Aleuts Iqyax. Hence the bartender transom with a rudder. Topside needs to be very aerodynamic in all directions unless absolutely necessary.
    Short amas closer to vaka seem popular for power trimaran. They say there isn't much wave drag between hulls. I guess available power to wave disturbance drag is insignificant. But they are a big issue for slower boats, are they not? Since my main goal is comfort stability, I choose long amas placed wide from vaka. As probably mentioned in a previous post, partial retraction and some akas angle control maybe desirable for my setup.


    I heard somewhere emmpennage drag can be used to help accelerate boat better. I don't quite understand it yet. A ship propeller version of turbo jet engine with fast core jet stream surrounded by the slower laminar airstreams to improve fuel economy and speed? or, are the outside rudders just lifting boat forward? Just a hearsay. http://www.modelwarships.com/reviews/ships/dkm/s-boat/s-100-72/72-S-100-p2.htm
    [​IMG]


    I am sorry I didn't share my modular multihull concept. It was a test bed kind of idea, so I can test multiple hull shapes and mix them together for testing. And it can be reconfigured for optimal performance for each trip. I will probably build 40' cruiser vaka and amas in 20-26' size first to work out the concepts. The 40' cruiser will not have a detachable main hull.
    This will be similar to Wharram catamarans inthat all hulls and beams come apart to test not just different hull combinations, but even switching asymmetrical hulls to optimize use for sailing or motoring with same two hulls. Hope to start building this winter.

    I hear Wharram style beam mounting is good for repairability but they needed constant (daily) inspections and rope retightening in real ocean passage. Another hearsay, no real experience. I will do similar setup using quality marine SS bolts, nuts and retainers. I am lazy.
    There are many great boat designers out there, so I wanna get inspiration from them then do my little final touch to get what I need. Comfort stability is one issue, best hull form I can appreciate visually and theoretically for fast semi displacement is Aleut's Ikyax. Alan, either you made this in your past life or you would have if you were there back then. Narrow beam 20.4", length ~16' 8", displacement to sheer 600+#. Fast, quick, surfs with buoyant stern and built-in rudder. Does the bow shape cut waves, knock bow wave down, give bow buoyancy and minimize bow slap? My guesses.
    [​IMG]
    Upside down Aleut kayak frame to see better stern shape. Amazing :idea:
    [​IMG]
     
  5. Yobarnacle
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    Yobarnacle Senior Member

    In olden days of narrow beam leadmine keel wooden yachts, diagonal strapping of the hull with bronze or iron straps was the norm. A practice developed in building large wooden ships.
    You may need to resurrect this engineering in your skinny hull design. Consider the beam/length ratio of a mast, and how it is strengthened by diamond stays and spreaders. some tensioned stainless cables strategically incorporated in your hull might improve longitudinal strength. :)
     

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  6. Sailor Alan
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    Sailor Alan Senior Member

    What an excellent description. I imagine a sort of Bartender, 40’ LOA, and 4’ WLB. stabilized by half length Ama’s set fairly far out. The Wharram boats, though successful ocean crossers, are a bit marginal as far as strength is concerned. For instance, if the hull sides are extended upwards, or the distance between the hulls increased, then the beams and their fastenings become a limiting factor very quickly. They are acceptable as is now, but will not stand the greater strain as above.

    If you are designing/making an AKA, the beam, then consider a proper “box” beam, with multiple plywood vertical elements, and solid (or laminated) upper and lower caps. This is similar to aircraft structure, and bridges etc. I could help with this.

    Rather than the self supported masts, consider deck stepped masts with simple wire stays. If the mast is 20-25’ long, it is relatively easy to raise. If you are going sailing, raise a Gunter Lug rig on a 20’ yard. This means the mast reefs as you reef the sail, and only a 20-25’ mast is left for storm, bridge, and other clearance. This too can be lowered single handedly. Alternately, Im sure Yobarnicle would like me to mention a bipod or “A” frame mast hoisting a lateen spar and sail between the legs. This is wonderfully efficient sail and rig, though the spar might be excessively long, i.e. more than 40’.

    I am quite concerned about the weight of the outboard on a classic bartender stern, or any other ‘pointy’ stern for that matter. If you place the OB (300hp?) behind the Bartender type pointy stern, then its weight is cantilevered out behind the somewhat minimal buoyancy, and the stern will be loaded down. So much so that waves from behind may not lift the stern when needed. I would suggest taking the full 4’ WLB all the way to the stern.

    The half length Ama’s are a good compromise, between the full length ‘sailing’ ama’s, and the 1/4 length ‘power’ ama’s. Being about half way along the boat, they could be rigged such that they are completely clear of the water, no drag, at 20+ kts, though only one will be in the water at a time at rest. It gives a slightly odd feeling, but the boat usually sits one side down at anchor. Be careful, if an ama dips in the water at 30kts, you might do a sudden, and unexpected turn. Normal sailing ama’s are often rigged far forward as that is the direction of force when sailing, and you will not have this characteristic. This means, you may not press the boat under sail, and need to reef early, not later.

    The 300hp you have chosen is rather large, so i checked. It appears that 300hp could get you literally flying at 50+kts, so i have taken the liberty of cartooning your boat both sailing, and flying. I have used some very obscure, and rather old techniques to do so. The boat will be flying in “Ground Effect’ which allows far greater lift per unit area of ‘wing’. I have increased dihedral significantly so the vehicle is inherently stable laterally, in roll. By using a rather obscure control scheme, occasionally used by cruise missiles, called ‘twist and roll’ i can dispense with vertical rudders, and minimize roll in a turn. This means the plane will stay reasonably ‘flat’ i.e. horizontal, during a turn. Finally, i chose a ‘canard’ layout, in fact a version of Reinhold Platz’s work (he was Antony Fokker’s chief designer) using ‘soft’ wings. This means the wings suport the generally aft biased weight distribution of a planing boat, rather than the generally forward weight distribution of an airplane.

    http://en.wikipedia.org/wiki/Platz_glider

    It just so happens these same masts and sails can be used to ‘sail’ as well as fly, and you can use the same masts and struts, though flying speed is limited. As flying height is limited by ‘ground effect’ i think a water propeller on the end of a long shaft, from the forefoot of the boat would work quite well, and be self regulating in flying height as well. An airplane propeller, like a swamp boat, would also work, but it is not as efficient as a water propeller.

    The next step is to do a proper ‘weigth and balance’ to get the dimensions and weights better, but these rough sketches will be close.
     

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  7. NoahWannabe
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    NoahWannabe Junior Member

    Sail rig, OB, akas, WIG :D

    The aka beams should be at minimum reinforced box beams, possibly welded metal beams. Thank you, but I hope that day will come soon too.

    You are being too logical here, hard to argue against this. I also do like Brian Eiland's A-frame aft-mast design for catamarans, but for a trimaran double masted yawl is my prefernce for fishability and sail steering.

    I am hoping to design OB well for 300 HP OB :D, so I can have proper lifting rudder after. The well should have top and bottom covers so well won't get filled with water and create drag. I know it will need some type of hydraulic jack system. So OB will be several feet forward of the transom, and it is still too heavy there with 600-700#. Maybe the well should be further forward.

    As mentioned, akas will be retractable. This isn't clearly thought out yet. Sometimes I want retractable beams inside tubes, then othertimes I want akas to retract by swing action. Swingarm akas maybe better here, ala Dragonfly and SeaClipper. During sailing, amas will fully swing forward with maximum beam width. When motoring fast with 300 HP OB, akas swing back to bring amas near the main hull and toward the stern. This will cause more CoB and CoG toward stern during high speed cruise and prevent amas from tripping.
    Amas will be fairly heavy with spare fuel and other stored stuffs. With amas forward, it should balance out 300 HP OB during sailing and at anchor. When 300 HP OB is lowered then amas should swinging backward and this action will bring CoG, CoBuoyancy and lifting foils backwards for proper power motoring trim. I will need locking articulating akas.

    Would it be easier to articulate sail masts to wing position, or use akas as a wing? Catamaran designer Bernd Kohler also loves WIG planes. Fascinating, but is this feasible technically and regulatory-wise? Water propeller, haha, make it with carbon-fiber and fiber-glass exterior for abrasion resistance when stowed in keel. This is still a boat with propeller barely in the water :p Solid wing sail with WIG capability. Awesome :D
    http://www.ikarus342000.com/
     
  8. NoahWannabe
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    NoahWannabe Junior Member

    Diagonal Strip Planking

    Thank you Yobarnacle. Diagonal strip planking is another method. I have not tried this method yet, since there seems to be some concerns with shaping each strip for complex curves especially if strips are made from thin plywood, and making boats heavier because of gap between the strip layers need to be filled with epoxy. I wonder if embedded steel reinforcement is better than carbon fiber or kevlar fabric reinforcement? Would this be better than aluminum over ply-epoxy hull? What about thermal expansion issue?

    Maybe this is the way to make wooden ply-epoxy boat capable in Northern waters. 1" thick hull below high waterline, 4 layers of 6mm ply-epoxy with kevlar both outer layers and fiberglass between ply layers. Would this be strong enough for icebergs? This would be equivalent to at least 1/8" steel wouldn't it? Except for surface hardness :(
     
  9. Yobarnacle
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    Yobarnacle Senior Member

    you need engineering advice and design. A naval architect is the expert you need. Stand your 40 ft boat on it's stern, bow aimed at the heavens like a rocket. It is NOW a 4 story building and vulnerable to storm winds and earth tremors, ect. Looks like a mini skyscraper!
    I would want an architect to design and engineer this building and it's foundation, so it didn't topple over with my family inside.
    The sea is a MUCH harsher environment than land. Running in 8 ft seas, is like picking your 4 story building up, and dropping it off a one story building once a minute, again and again for a long duration.
    Your basic concepts you can do, because it's more juggling priorities and determining reasonable expectations, than actual design.
    Engineering the design needs lots of education and experience. Even college degreed N/As don't get to design hulls fresh off campus. They do their apprenticeship drawing piping diagrams or other subsystems.
    And N/As are human and make mistakes. There are a lot of professionally designed and manufactured BAD boats out there.
    My recommendation is try to find a proven design, by a naval architect is re-assuring, but if it's PROVEN to work well, then THAT becomes the designers credentials.
    Have it re-engineered to use modern materials. Good Luck!
    As to icebergs, the 16 inch thick armor belt around the waterline of a WWII dreadnaught battleship isn't proof against rupture. My advice? Leave icebergs alone, give them a WIDE CPA. I have worked in ice on the great lakes. Pack ice, not ice bergs. we always had ice damage with one inch thick steel hull skins.
    Subzero degree F blue ice is diamond hard stuff! Ice navigation feels like a war zone and sounds like living inside a rock crusher. Noisy as HELL!
     
  10. NoahWannabe
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    NoahWannabe Junior Member

    NA? Wanted!

    Agreed. I don't know if an experienced NA with my requirement experience will work for a total boat budget of $250k. I wouldn't. I would need all $250k for analysis fee alone, excluding demo model building, model testings, modifications, retests, more analysis, then few more iterations and E&O insurance. So, I am looking for best features and other sub components that has worked first then hopefully sum of the design would be good enough for some "experienced" NA to look over and put his stamp on it after couple of hundred hours. Wishful thinking :)

    This I can calculate :) Easy! I have been to Waveland, MS (where Katrina landed, not New Orleans) and live in California doing charity engineering works sometimes. I can do most structural FEA too. Math isn't the problem, physics isn't the problem, but not having hydrodynamic/aerodynamic boat design experience is.
    The process is
    1. finding an existing technology to meet my requirements
    2. finding a NA that has kind of experience my boat will need
    3. finding a NA that can work within the budget

    I am at stage 1. I think I can find #2. Problem #3 will be difficult. The major issue I had with the original hijacker of this thread.

    You probably have seen more than I, but I have worked as a part-time commercial fisherman during college years off North East Pacific for fun, summer and winter :) I have seen 20' square waves in small 36-50' boats. I don't want to be in that kind of sea again in a small boat. Hence my desire for a fast storm getaway.

    I shouldn't have said iceberg, that wasn't what I meant. I am thinking of multiple trips of PNW to Alaska by Inner Passage during spring to fall, which will have much logs and some broken small glacial ice (floes?), but not the real 20' above water icebergs. I will make my arctic passage behind an icebreaker. Unless I get a sudden desire to go find Superman's sunken base in North Pole. I hear it is near Nick's workshop. Thanks for your love :)
     
  11. Yobarnacle
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    Yobarnacle Senior Member

    There have been numerous long skinny canoe type craft built for centuries. Hydrodynamics does scale over a fairly wide range either side of baseline.
    By that, I mean you could scale a 30ft boat up to 40ft or down to 20 ft. or even to a 3 ft model and the hydrodynamics would be recognizable, but not easily scale up to 600ft. because they would be different by orders of magnitude.
    Yacht designers do model testing of new designs. If the data learned wasn't scallable?
    Of course it is.
    There must exist a design that already proved seaworthy and seakindly and durable, that you could expand or contract to your required size.
    Engineering the scantlings isn't that big a deal. Nor is calculating forces and moments and required reinforcement. You just need the engineering to use modern materials on an existing design. If you can find a design you like, the modernization shouldn't take long or be expensive. For two hundred fifty large, you should be able to gold leaf the boat. :)
     
  12. Yobarnacle
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    Yobarnacle Senior Member

    Found this article about asymmetrical hulls being easier to power, more efficient, and this occurred to me.

    If you built a catamaran by buying and slicing an existing fiberglass monohull into two halves longitudinally, along the centerline. Build the two halves into two asymmetrical skinny catamaran hulls by creating the flatter missing half hull on each. You would save a lot of money and work. Also, interiors would be simple to work on, while being one sided like a stage set.
    but it still is a MAJOR project and needs proper engineering.
    Might work for the luas on a trimaran. Buy TWO used fiberglass boats and save them from the landfill and recycling means you were living responsibly. I'm pleased MY two 40 year old boats have extended life spans because I saved them. I AM environmentally conscious. Just resent big intrusive government. :)
    Here is the link and excerpt.

    http://www.academia.edu/5221214/CFD...il_was_taken=true&login=&email_was_taken=true

    "so that the catamaran with asymmetrical hulls requires lower thrust power than the traditional catamaran does. In other words, all the other conditions concerning the advancement being equal, the acceleration of the fluid in the convergent part involves a reduction of motion quantity given to the mass of water by propeller, increasing the catamaran efficiency."
     

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  13. NoahWannabe
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    NoahWannabe Junior Member

    Misinformation

    Yobarnacle, I will have to disagree with your points for benefit of any uninformed readers.
    1. Test results froma small models such as a 3' model for a 30' vessel doesn't work too well. It is 'orders of magnitude' different because of many inverse cube relationships in boat design dynamics. Also there are things that doesn't scale at all, such as wave. They are the size they are. Modeling is used for specific aspect of performance analysis and model size depends on which performance criteria one is testing. Minimum I would go for 30' vessel is 14' for general testing. 60' model for 600' probably works, but that I haven't given any real thoughts yet.
    2. Scantling, moment, vector force, harmonic distortions, etc. are all easy to calculate if you understand which one to calculate. Do you calculate X, Y and Z directional load? Axial and torsional load? What about diagonal? What about interaction between these forces and loads? All at same moment or in sequences? This is where you need experience AND complete understanding of medium. As you have mentioned, most graduates don't get to work on the boat for long time. Even then one makes mistake.
    3. Anything new (design, material, techniques, application, etc.) requires time to test all possibilities whether through failures or ingenuities. Most of the time it is based on past failures. So I am looking for collective minds advices here, whether boat design professionals or boat related professionals. I will acknowledge good advices and point out wrong untilproven otherwise.
    4. Unless you want to make a float for protected water that look like a boat, you can't cut a boat longitudinally and make it into a catamaran. It won't perform for anything typical applications require. Most boats have a specific performance requirement 99.999% of the time.
    5. Using existing FRG boat hull for a new boat is a false economy for most part unless that exact same hull shape is needed and the hull is in very good condition. It is NOT a reuse or recycle. Amount of time and resource required to bring them into some useful vessel usually requires same or more energy (carbon) than to build a new boat. A hobby boat builders in retirement is different since time and subsistence are already accounted for.
    Luas? Amas? Using old FRG boat and cutting them up for amas in trimaran assumes rough shape of amas. Would it work? Probably. Would it work 50% of the required performance? Probably not. Too heavy, too fat and probably unsafe for this application due to lack of buoyancy for a given volume.

    This is the reason why I am here, sharing my needs and hoping someone will tell me which boat can do what I want. My need may be very unique or wrong altogether, then I need someone to tell me to take a pink pill and get a Thai longtail taxi with Inflatable tubes around it. Until then I am in a slow search. This is fine as my admiral is not in a hurry, and I like tinkering, designing and building. Modernizing with new material, new design or new equipment in most part is not easy and not cheap. Then you don't find all the faults until something unexpected happens. ie: World Trade Center was designed and built to withstand an airplane crashing into them with fuel. If we only built one tower then we may have said, unexpected unusual event, but both tower collapsed meaning it was a total design failure for that type of event. It was a new material, we have been building skyscrappers with steel and mostly masonry, but not steel only. Easy, quick and cheap? None of the above.

    Thanks, I think ;) I didn't have chance to read the whole link. How does it apply to this thread? Generally, power displacement catamarans have straighter surface (less curve) on inner hull sides for reduced wave interaction drag, and sailing catamarans have more curved lifting surface on inside hulls for better lateral resistance. Planing power catamaran is completely another story. My motorsailing trimaran needs more curve inside for sailing then flatter hull inside during motoring. Impossible to do both unless I have a flexible surface changing hulls. Another new invention unless aeronautic guys covered boat hulls on their wing curvature changing patents.
     
  14. Sailor Alan
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    Sailor Alan Senior Member

    You are absolutely correct. These metal braces were inserted to resist torsional forces. In the day, a wooden ship was held stiff by extremely clever wood joints, where the wood on wood interface held the forces, and any fastening was merely to hold the interface together. Such joints always had some 'play' in them so all older sips worked, at least a bit.

    Modern plywood boats use bulkheads, or bulkhead like structures to stabilize their structures against such torsional strains. These bulkheads may be 'full' or partial, but always provide torsional rigidity. Under normal conditions, these structures are bonded together, but classically the joints between frames/bulkheads, and their associated stringers are very small and therefore rather too low a surface area for good strength. Perhaps the greatest single issue in this class of structure is providing sufficient connective force between the stringer and the frame/bulkhead normal too it. Aerospace structures attempt to solve this by adding 'shear ties' across the stringer/frame/bulkhead junction. Welded ships probably do too, but this is far less easy in plywood vessels.

    Composite Aero structures, like plywood boats, need a lot of help with these right angle joints, and I have spent the last decade or so of my professional life attempting to resolve this for the aerospace industry.

    To me, a better analogue for a boat structure is to imagine it suspended bow and stern between two points with forces added in the middle, whilst being rotated 360'. Of course a boat with no deck, like a Thai long tail, will have a much harder time satisfying this requirement than one with a full deck. Allowing access to an airplane, or ship, is always an issue. We for example looked forward to the day when passengers, or self loading cargo, were no longer necessary.
    As in all these structures, point loads are the issue. Could we do away with them, the structure would be far easier.

    Your plan to have the ama's pivot forward for sailing, and aft for power is exceptionally sound. There are any number of arrangements for pivoting your ama's, but I would suggest a simple swinging arm like a gate with the hull end pivots 3-4' apart vertically, and the AMA end 18"-2'. Welded from aluminum mast section, with large diameter aluminum vertical tubes, with rubber doughnut inserts as pivots, they could be most satisfactory. Alternately, welded SS would work, but SS still looks perfect AFTER its broken, so unless well stress relieved, i don't trust it.

    I include a cartoon on how your could stow the resultant vessel in a 8' square container for transport. Unfortunately, it needs the ama's to be removed and inverted for them to fit with a satisfactorily wide center hull.

    Moving your large OB forward has merit, but now it's bulk and it's well will dominate your cabin. Perhaps it is worth reconsidering a 300hp inboard, under the cabin floor, with perhaps a shaft to a vertical pivoting Thai Short Tail at the transom. You could use the drive shaft from a front wheel drive car, including its constant speed universal joint. In fact a case could be made to use the propeller at engine speed, rather like some Thai boats. If it's a diesel, then propeller speed is a bit slow for a true surface drive, but a normal gas engine could run nearly half surface drive RPM. This is sometimes what the Tai's do. Supercharged engines are usually lighter.

    I have shown a couple more cartoons of the flying boat. I am a bit surprised how well the numbers work out, but the key here is (relatively) slow and low.
     

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  15. NoahWannabe
    Joined: May 2014
    Posts: 89
    Likes: 1, Points: 0, Legacy Rep: 10
    Location: United States

    NoahWannabe Junior Member

    Arctic Sailing: Adrenaline Expedition

    4 reference: NorthWest passage, Alaska to Greenland, without any motor and in a single season. It is a foamcored, kevlar/carbon, 24'x16' sailing catamaran. Sailing through some water, some packed ice and some glacial ice. No support ship or outside help.

    [​IMG]
     
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