Semi Submersible Sailboat Hybrid

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

  1. NautiPhillip
    Joined: Aug 2019
    Posts: 27
    Likes: 1, Points: 3
    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

    Thanks for the correction and the suggestion. I am learning a lot from you.
    It should also support dynamic ballast for more displacement than that. But just getting through to basics is a milestone. So thank you again.
    You are most probably right. I'm not greedy. I know 20 knots is near tops speed. Half or three-quarters of that number would be acceptable and even great. Who knows at this point? This may turn into a hybrid motorsailer of sorts.
    Great idea! I have some thoughts on the matter which I'll share soon. I think I'll try sketching it out and posting it when I'm done. I hope to include the retracting and canting counterweight arrangement too.
    I think you are correct, especially about handling, but this shape does not include a keel or control surfaces either. In any case, those things can be sussed out with flow dynamics software once the basic shape is decided upon. That is the foundation upon which all else will depend, right?

    I think we need more space above the waterline. What do you think about tramps that retract? Most of the time the weather will be calm enough for lounging above deck. I'd like to explore how we can minimize the 'dark cave' scenario and come up with something more 'fun'.

    In most oceangoing vessels, no matter the size, below decks in rough weather is uncomfortable at best and dangerous at worst. There are recorded cases of over 20g impacts coming off a large wave. That is bone-breaking and massive trauma territory.

    There is a US government study that demonstrates a profound reduction of injuries, stresses on the boat and a great increase in comfort for occupants, through utilizing wave piercing modification to the bow shape and running awash. There's an online PDF on this topic; a research paper. I'll try to locate the link for you.

    What I'm trying to say is that it could be much more comfortable that most large monohull sailboats under similar conditions. They can take on a dark cave feel too when the boat is violently hobby-horsing under dark skies, through a big blow in a long fetch and your shipmates are puking in a bucket. Know what I mean?

    Your contributions and instruction is proving to be very valuable to this old man. Thank you very much.
  2. NautiPhillip
    Joined: Aug 2019
    Posts: 27
    Likes: 1, Points: 3
    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

    Right on the money Squidly-Diddly. But the shape I am trying to use is not a classic sub shape. Instead of the rounded bow of a typical sub, this one is tapered and will be modified to a more wave-piercing shape. Shouldn't that help too?
  3. Rumars
    Joined: Mar 2013
    Posts: 275
    Likes: 58, Points: 28, Legacy Rep: 39
    Location: Germany

    Rumars Senior Member

    You need to decide what the primary mode of operation is and design the hull acordingly. You have in this thread mentioned "running awash" and "only the tower showing" and "submerged to snorkel depth". For running submerged the best shape is the modern Nautilius shape and you saw how that performs on the surface. Only the tower showing is running submerged and you don't see subs doing it often because running submerged is an unstable condition. Running awash means having a defined waterline and a minimum of freeboard present at all times. This means the shape must be optimized for surface operation. That would be the shape submarines had in the interwar era and WW2 up to, but excluding, the german Type XXI.

    But for the goals you stated in your last post the best hullform is SWATH. Minimal effect of seastate on vessel, big platform above for living. You just have to make one sail, but it's a big catamaran after all, it can carry the sailarea needed and we have the tehnology to make it tack against it's will. For ultimate sea confort just add electronicly stabilized cabins and you are done. The bed and table stay level at all times. No need for dark caves, rotating ballast and mast and all the sub gear.
  4. NautiPhillip
    Joined: Aug 2019
    Posts: 27
    Likes: 1, Points: 3
    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

    Agreed and I am currently re-evaluating my entire approach. Expect a more detailed response in a few hours.
    UPDATE: May be longer. We have a dinner guest; a tropical storm named IMELDA and I have to go check on my boat.
    Last edited: Sep 17, 2019
  5. CocoonCruisers
    Joined: Dec 2015
    Posts: 45
    Likes: 10, Points: 8, Legacy Rep: 10
    Location: Marseille & BuenosAires

    CocoonCruisers Junior Member

  6. fallguy
    Joined: Dec 2016
    Posts: 1,984
    Likes: 113, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    I think you need to revisit the SOR.

    If you merely want to submerge to get out of heavy weather; you would not need to design for underwater movement.

  7. NautiPhillip
    Joined: Aug 2019
    Posts: 27
    Likes: 1, Points: 3
    Location: Seabrook, Texas USA

    NautiPhillip Junior Member

    Sorry I've been out of touch. I've been dealing with some health issues and besides, my internet is down. I hope to have these issues resolved shortly.

    I've been following your contributions with interest and I've continued to study the other threads on this site. Hope to be back online soon. Thank you for all your help.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.