Semi Submersible Sailboat Hybrid

Discussion in 'Boat Design' started by NautiPhillip, Aug 31, 2019.

  1. NautiPhillip
    Joined: Aug 2019
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    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

    This is my first post so please allow me a minimal introduction. I am an old man now and my days are numbered, but my love of all things nautical remains a major interest. I started boating in the late 1950s, crewing charter monohulls and racing tornado class catamarans in the '80s and sailing has remained a passion throughout my life.

    My professional background is varied and includes a wide range of occupations; the most applicable here would be my time as a database designer. programmer and design application researcher. DGO systems (now defunct) hired me to find applications for new technologies in the '90s where we developed vocoders for cell phones and data compressions and transmission techniques among other things. There were other, more physical project that included optics and mechanical designs, some of which I am still restrained from discussing. But the bottom line is that I love innovation.

    Recently, as the result of medical malpractice, I sustained 'remarkable' peripheral and central nervous system damage that impairs my abilities to do mathematics among other things. But I can still conceptualize and do limited research and I have some ideas I would like to share and develop further. Perhaps a few of the more kindhearted members here might help me along the way.

    While most boat designs are specific to their intended use, there are also those that incorporate a remarkable variety of compromises to widen that scope. My interest is to explore such a compromise design that can be economically constructed and upgraded as needed. Specifically, I am curious about VSV power hull design characteristics and how they might best be modified to accept sail as a primary long range power source while still retaining the comfort and survivability that the wave piercing and semi-submersibility of the VSV design offers. Obviously, I am intending a non-planing versions of the VSV concept.

    Let me conclude by saying that I understand how disparate and even contradictory this cross platform concept might seem, However, after spending a few months performing cursory research and making general drawings addressing some of the more apparent obstacles, they no longer appear to be insurmountable. In fact, it is my belief that this is not just doable, it is a reasonable approach with many attractive qualities.

    Thoughts?
     
    Last edited: Sep 7, 2019
  2. NautiPhillip
    Joined: Aug 2019
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    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

    IMPORTANT NOTE: It is not the intent of this post to promote or condone ANY illicit or illegal activity. I am simply intrigued by certain feature of this design variant for the purpose of developing a cruising sailboat that incorporates some of these features.

    [​IMG]

    Please excuse the sensational aspects of the drawing, but the 'narco' (Colombian cartels, Tamil Tiger, Hammond Motors 'Needle' et al.) variants of the DARPA inspired SOC craft, are of interest to me for a number of reasons. This drawing visually illustrates the L/W ratio of a non-planing version of the VSV concept compared to other submersibles and semi-submersibles. So I would like to gather information on how to best incorporate some these features into my design. It should be noted that stealth is not a feature I am seeking, nor is it likely to be achieved when applied to a sailboat. ;)

    I find it more than a little intriguing that an approximately 50-60' vessel, built in the jungle 'on the cheap', can sustain 20+ knots while running fully loaded and awash in heavy weather conditions, all the while powered by less than a combined 300 horsepower produced by standard outboard engines. So I have some questions.

    >What is the breakover point in terms of length vs. width as it applies to speed?
    >How much does wetted surface negatively impact the advantages of a VSV hull design? Stated another way; How much does draft affect these calculations?
    >Since planing versions of the VSV design rely on hard chines for lift, is it reasonable to conclude that that a cylindrical hull with stabilizing features will not negatively affect speed in non-planing versions? But if so, how?

    Any assistance in these matters will be greatly appreciated. Fair Winds Y'all!
     
    Last edited: Sep 1, 2019
  3. NautiPhillip
    Joined: Aug 2019
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    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

    So, a little reading got me to 6:1 L/W or better and that info got me to this point. The rigging and keel would be mounted to the rings that are flush to the outer hull and rotate the sail rigging and extendable and canting keel together but separately from the hull which would require its own stabilizing surfaces.

    The bridge area and upper deck is already being scaled back. I'm using Sketchup Make 2017 and it is very limited in the shapes I can draw. I expect to 3D print the segments and assemble a working model as soon as I workout the upper deck hull shape. So as far as the hull shape goes, this is very rough at this point, but kind of what I was thinking.
    ConceptBoat2Bridge.png ConceptBoat2.png ConceptBoat2.png
     
    Last edited: Sep 6, 2019
  4. NautiPhillip
    Joined: Aug 2019
    Posts: 26
    Likes: 1, Points: 3
    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

  5. NautiPhillip
    Joined: Aug 2019
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    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

    Not a single damn comment. This is discouraging.

    NOTE: All images and concepts are Copyrighted (2016) and All Rights are Reserved. The unique design elements are in the early stages of the patent application process.
     
  6. CocoonCruisers
    Joined: Dec 2015
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    Location: Marseille & BuenosAires

    CocoonCruisers Junior Member

    I'd think there is not much wrong with the design intent, warships have relied on slenderness for ages and many of the early small oceangoing sailboats came close to the 'run awash' ideal, hoping to avoid some of the wrath of the seas. Sutton's blog is a fun read, thanks for that discovery !

    But there are pretty mature alternatives to such designs, especially if you tend towards lower power / lower speeds. And there will be pitfalls in the execution:

    - 6:1 seems way too beamy if you want to go faster than single-digit speeds. And if you don't want to go faster, why bother with the constraints of wavepiercing ? Also with a beam like in your drawing, you'd need to carry around a hundred tons of ballast or cargo - more than the vessel weight - just to sink the boat enough to operate in the intended mode. If the intended use is leisure, where the boat is basically empty so that you can enjoy the luxury of space, that ballasting would make it slow/inefficient. For cargo, you'll need to consider access constraints (these can probably be solved) and the specific weights of the cargo types you want to load (Some may just not be heavy enough for the boat to function as intended. And what if you have to sail a leg without any load ?) .

    - Why monohull ? Long and slender wavepiercing hulls are quite common in multihulls. (Large french racing tri's , MY Ady Gil, adastra yacht, harryproa ...). These forms allow large bridgedecks like you seem to want, and they provide enough righting moment for fast sailing. But the hull beams are more like 1:15.

    - IF mono, you'll probably remain stuck with the very limited beam of the hull (less than half what you drew i fear), and with the 'dark cave' character of most of the living spaces. A deckhouse like you draw seems somewhat antinomic with the wavepiercing paradigm: It will be exposed to heavy wave impacts, like, or worse than a multihull with too little bridgedeck clearance. If what you have in mind is something with an extremely deep keel, think like these IOM rc racing models, you could probably lean towards a monohull variation on the SWATH aproach, with a conning deck + modest sailing rig high above the water, on a narrow strut.

    You could probably get some grip on the resistance/power aspect by playing with Leo Lazauskas ' "Flotilla" software (dig up the related threads on this forum); but you'd need to come up with a rough idea about the boat's weight first. Then you can compare with sail forces on SailPowerCalc https://cdn2.hubspot.net/hubfs/209338/docs/news/SailPowerCalc/SailPowerCalc.htm and find out if you can aim for 'pure' sailing, or if you'd better optimise for motorsailing.
     
    Last edited: Sep 14, 2019 at 9:33 AM
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  7. NautiPhillip
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    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

    CocoonCruisers, thank for your well thought out response. Please forgive my delay in responding as I have been hospitalized for lengthy testing and have been without my computer.

    I will take some time to research your observations and the material you offered. Thank you again. Your post is very enlightening.

    As far as the 6:1 ratio, that is simply what I deduced from the 'Covert Shores' drawing above. Do you have any more info on L/W ratios and the performance of non-planing hull designs or links to related research? I'm new to all this, but am fascinated by the concept.

    Regards,
    Phillip
     
  8. NautiPhillip
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    NautiPhillip Junior Member

    Btw, I have many friends that have developed physical problems associated with age or injury. I have also seen what can happen with multihull in extreme weather and seastates. So I'm just casting about and exploring ideas that reduce g-force stresses on both boat and crew and provide a more comfortable and safe ride. Thanks again.
     
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  9. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    Just a few toughts and hints:
    1. Change the thread name to something clear (and clickbaity) like "semi submersible sailboat".
    2. Minimum L/B ratio for overcoming displacement speeds without planing is around 8:1. Search forum for "displacement speed", "Froude number".
    3. There is a limit to the slenderness depending on displacement of around 16:1-24:1. Go higher and skin drag (frictional resistance) becomes prevalent enough to cancel out the benefits of higher slenderness. You need volume to carry the weight and if the hull is to skinny it increases wetted area disproportionatley.
    4. A boat can carry only so much sail area and horsepower is therefore limited. The usual strategy for speed is to minimize skin drag by flying at least one hull or go completley airborne on foils. Going semi-submerged is counterproductive for speed under sail, you can not simply add another motor to double HP.
    5. The closest thing to what you want were the early skerry cruisers. Then they got the "coffer rule" and that put an end to the excesses in slenderness.
     
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  10. NautiPhillip
    Joined: Aug 2019
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    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

    Rumars, Hi! This is brilliant! Exactly the type of response and input I was seeking. This is very exciting and I am very grateful for your contributions!

    Perhaps my flights of fancy will bear fruit. Perhaps not. But if so, it is not the first time that a novice has introduced what seemed to be impossible ideas that turned into workable suggestions, simply because they didn't know any better.

    I hope you will forgive me, but I broke out your post by number so I could respond in like manner. During that process, my spellcheck and grammar check modified your post slightly, but not in any material way so I left the corrections. I hope you don't mind.

    Anyway, I love your suggestions, especially the first one...
    ...the drawback being that I don't know how to change the thread name. Perhaps a Moderator or Administrator might help. So to any Mods or Admins reading this thread, please consider this as a formal request to change the thread name to, "Semi Submersible Sailboat Hybrid". You have my gratitude in advance.

    Will do. I love to read and that will go quickly. But I'm sure that I will spend quite a bit of time internalizing the concept and it's application before I understand it in any meaningful way. Thanks for pointing me in the right direction.
    In my initial thoughts, I envisioned deducing wet ballast requirements (because in my mind, a ballast system is a requirement to meet my design goals) after calculating the approximate weight and cargo capacity of the vessel. Presuming that some type of ballast system would be required seemed obvious, but calculating those numbers is premature at this point. As I mentioned in earlier posts, I am still spit-balling here. My first goal is finding the best hull shape to meet my objectives.

    As an aside, I do wonder if there is any information on hydrophobic coatings and frictional drag. My concerns are based on initial costs and long term maintenance vs. the benefits of reduced drag on wetted surfaces.
    Rumars, it is my understanding that they deduced an average between 20 to 25 knots SOG over 2000 nm operating in the western equatorial Pacific, as a conservative estimate for one of these 'narco' versions of a VSV. This boat was powered by 2-3 suzuki 150 hp outboards. It's estimated cargo capacity was 1.5 tons, length was 60' and beam was 5'.

    These hull designs are hard-chined elongated boxes that narrow to a wave-piercing bow. I am looking at comparing these hulls to classic submarine designs with the hope of finding a set of desirable compromises that preserve the best features of both hulls to accommodate specific criteria.

    It is worthy of note that the vast majority of their electronics were all handheld devices or portable marine instruments such as depth gauge/fish finder sonar and chart-plotter combos. I know a few delivery captains that employ the same strategy to augment and back up shipboard systems and I do love it's simple and lightweight approach.
    I am passingly familiar with this form of boat eye-candy. They are absolutely stunning vessels but not what I am really interested in designing. Long, sleek lines with graceful overhangs and iconic rigs? Sure. But a semi-fast, semi-submersible live-aboard that is comfortable and safe in heavy weather and suitable for long passages? Not so much. I'm sure you understand what I mean.
     
  11. Boat Design Net Moderator
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    Boat Design Net Moderator Moderator

    <thread title changed as requested>
     
  12. Squidly-Diddly
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    Squidly-Diddly Senior Member

    I sorta like the concept of semi-sub sailboat, for several reasons.
    1)Subs is gonna have ballast tanks, and I'm a big fan of transferable water ballast (or fuel, or fresh water, or booze lol) as a more efficient way to get more righting moment with less weight. While most subs are more concerned with fore/aft ballast trim, port/starboard for sailing should be easy.

    2)To go fast in most directions, a sailboat wants a big sail but low windage hull, so a boat that is normally decks awash should have that aspect well covered.

    3)Just to pull all that open air living space into the water you are gonna need heavy load in the keel. IIRC many WW2 subs had massive lead-acid battery banks AND an additional lead keel. IIRC a disabled British sub surrendered to a German flying boat in the shallow Baltic after detaching its lead keel and floating to surface. All that heavy keel should provide massive righting moment AND give you a reason to haul around lots of heavy batteries.

    4)Last but not least. Mast would function as both periscope/radar mast and snorkel.

    IMO a not-too-deep diving sub could do well in tourist market, where you got good scuba sight-seeing but not everyone wants to do the scuba or even snorkeling thing, and most of the best scenery is in 50ft or less of water anyway.
     
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  13. NautiPhillip
    Joined: Aug 2019
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    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

    CocoonCruisers, You are most welcome and again thank you for your insights. I've broken you post up by segments and will comment on each in turn.

    It is my intent to incorporate a ballast system and my goal to achieve full-time semi-submersibility and full submersibility for relatively short stretches. In fact, running above the surface is not a problem either, but may be desirable in smooth sailing conditions. So I see I have more decisions to make.

    You contributions concerning L/W ratio are worthy of greater consideration and I will answer more fully as my education in these matters proceeds.

    My only reservation to multihull designs is their inherent difficulty to right after capsize. I have a LOT of hours sailing and racing cats, mainly Tornado Class. I have also sailed full size cats starting with a West System 26' Cat we found abandoned and restored with some friends one summer long ago. I love them. However, I am looking to design a resilient, self-righting sailboat hybrid designed for survivability, comfort and a reasonable average hullspeed. So I could go either way if some issues can be overcome.

    There are a number of industrial products I am investigating that may prove valuable in producing a component based assembly with minimal customizations and adaptations. Like I said. Still spitballing.

    The 'dark cave' aspect is something I'm working on. I'll post more later.

    I surmised as much. The drawing is actually a reject because of the bridgedeck, but still represents the hull I envisioned.

    I'm curious. What is the advantage of a elongated rectangle tapered to a point over a cylindrical hull tapered in a like fashion? I mean in relation to both speed and stability. Can you elaborate?

    This is great! Thanks for the link and the suggestions. I see I have a steep learning curve to overcome, but this is not a first and I welcome the challenge. Expect that I will more fully answer you questions and respond to the pitfalls you have highlighted. Thank you again for you help!
     
  14. NautiPhillip
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    NautiPhillip Junior Member

    I agree.

    Also true.

    I'd love to read that story. The moral of that tale is maintenance, the bane of many sailors.

    I have envisioned a diesel/electric drive as ideal for this platform. Definitely worthy of more deliberation.
    I have some thoughts on this, but will reserve comment for now. In principle, I agree.

    Unfortunately, most of the alternative applications for a boat of this nature are precluded by it's length. But this is a topic I intend to explore more fully as I have some ideas that may prove doable.

    All in all Squidly-Diddly, you make some very good points. Thanks!
     

  15. CocoonCruisers
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    CocoonCruisers Junior Member

    Just a couple quick thoughts:

    If you go through the trouble of water-ballasting, why not turn it upside down ? If you have a multi with foam in the coachroof, and one hull with a large ballast tank and enough engine weight or lead so that you can to make it heavier than water, you could right your multi with a bit of pumping. No deadweight to drag around in that scenario, and you wouldn't even need a new build for that - a (substantial) modification could probably do.


    Can't resist going full circle - how about a pneumatic powder blow tank to do it with the coke ?

    There might be some coherence between the insanely heavy windows required for this functionality and the need to ballast the boat.

    Then, again, maybe you'll want to see something else than fish from time to time. There also is a conflict between the need to generate righting moment for sailing, and the very low center of buoyancy of a semi-submersible. Internal ballast might not be the complete answer to that problem. Speed is not going to be very high, so appendage drag is not going to matter all that much. Canting could be desirable.

    Then, how about some kind of solution with multiple deep keels that can also serve as legs to raise the boat near a beach, like a spud barge ?

    Not quite sure if understand this one right. If it's about the SWATH vessels, the aim of the whole 'small waterplane area' thing is to reduce the breaking effect and devastation potential of greenwater impacts. It's done by moving most of the buoyancy below the waves, and the platform for the people and activities above. Just like an oil rig, but streamlined so that it can move.

    Wishing you best luck, but there is a philosophical pitfall in what i understand from your approach so far:
    - Singling out trends can only give you a starting point, and it will most often only be a local optimum in the design space. Deeper checks of your ideas will probably lead to considering very different solutions, like suspensions...
    - What i think you are actually trying to do is: Exploiting differences in scaling to come up with a breakthrough design for a certain usage scenario. Scaling diverges widely for the various aspects of your project: Size of humans and the size of waves in a given region are fixed, 'hull-speed' style resistance scales with displacement and wetted surface, foiling and planing resistance scale with weight, areas and aspect ratios, your budget and lifetime to be invested don't quite scale at all, righting moments and accelerations scale with levers, structure scales with length and the way you expose surfaces to wave impacts, while the actual magnitude of the greenwater impacts will also scale quite a bit with the crew's level of masochism... That is, like most things in marine design and engineering, an optimisation in complexity. So it can only be solved iteratively, which cannot be done without quantification, nor without a bit of automatisation of the analysis.
    - The nice news are that thin ship theory covers a large part of your approach (hence the Flotilla hint), while the design goal of minimization of the added resistance from waves impacts will also reduce the headaches about their quantification.
    - But there is more to it. It's not necessarily all that hard to tackle, but it's more than can be handled casually on a forum, and if you try to do it all from scratch you're in for years of learning and debugging of the tools. So perhaps you should hire some help for the quant part and tool setup for a couple days here and there, or just for an "educated guess crosscheck" at adequate granularity from time to time.[/QUOTE]
     
    Last edited: Sep 15, 2019 at 10:23 PM
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