Semi Submersible Sailboat Hybrid

[NautiPhillip]

I'll recommend doing all the math in metric, it's much simpler.
Total volume = 6197.5056 cubic feet = 175.494 cubic meter
Submerged volume 4/5 (0.8) of total volume = 4958.004 cubic feet = 140.39 cubic meter. 64lb/cubic feet of seawater displaced x 4958.004 cu ft of submerged volume = 317312.28 lb = 143.93t

Thanks for the correction and the suggestion. I am learning a lot from you.

So if you want to submerge that conic/cylinder shape to 4/5 the whole object (that is including the crew and their rubber ducks) must weigh 143.93t. How much is ballast, structure or payload is irrelevant, seawater is pushing up with 143.93t so you must push down with an equal force, meaning you must provide the mass.

It should also support dynamic ballast for more displacement than that. But just getting through to basics is a milestone. So thank you again.

As I said this puts us solidly into J-class yacht displacement territory, so needed sail area will be at least the same, around 7500 square feet. Actual sail area depends on target speed under chosen conditions and could be less or more depending on the SOR (with a desired average speed in fair weather of 20kn I expect much more).

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.

Given the hull configuration the only way of doing it would be using A-frame masts. The sail by wire aspect is solved, all superyachts do it.

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.

The canting ballast/rig and the true submarine requirements I can not comment on. I can only say that even if you solve the technical parts of stress and weight distribution the handling of the whole object will be nothing like you imagine. If you really want the thing to be able to submerge even the nice interior you seek will disappear, it will get as crowded in there as any WW2 sub.

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.

 

[NautiPhillip]

thats mostly because that hull is optimized for fully under water operation and reduction of noise/sonar, and max underwater speed under nuclear power.

I'd say the late model Nazi U-boats/USS Nautilus type hull is a good compromise for current civilian use.

PS-IIRC the USS Nautilus suffered from vibration of the "sail"/conning tower at higher underwater speeds.

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?

 

[Rumars]

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.

 

[NautiPhillip]

You need to decide what the primary mode of operation is and design the hull accordingly.

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.

 

[CocoonCruisers]

Quite a readymade just calling for more experimentation :
You Can Buy This Crazy Experimental Littoral Combat Ship For $180,000! https://foxtrotalpha.jalopnik.com/you-can-buy-this-crazy-experimental-littoral-combat-shi-1683431253?fbclid=IwAR1SkQZFvkmFLwQViOJsUYPnOzZpZSDkuZDlIQyOMyX9aefC3dH7zMxKpdo

 

[fallguy]

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.

 

[NautiPhillip]

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.

 

[NautiPhillip]

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.

Hi fallguy,

That is just it. I don't. The idea is to be able to navigate through heavy weather and sea states; not to just submerge and wait it out.

The SVS cargo boats I observed, those boats that run awash, still make 20+ knots in heavy storm conditions. Not only did this strategy greatly reduce lateral stresses on the hull in big waves, it produces a very comfortable and stable ride for the occupants.

This design will never work as a true submersible. Everything will have to be simplified.

The concept I am attempting to develop is a hybrid aimed at a very specific market. I want to come up with a design that is attractive to middle-income consumers that wish to sail as long range, long-term, live-aboard Cruisers.

It is amazing the number of sailboat owners and crew I know that suffer from motion sickness. Those people that can 'gut it out' remain on the water. Those that can't, don't. So I love the idea that there is an alternative to traditional sailboats that can be affordably mass-produced.

I realize that with this design that trade-offs will have to be made. Sacrificing beam means giving up living space. I'm currently trying to work out the math for an elongated teardrop hull shape with control surfaces and a wave piercing bow. This is no easy matter for a novice such as myself. But that doesn't mean I'm going to give up.

If, in the end, this proves to be an unworkable design, so be it. But I'll never know unless I follow it through to its logical conclusion.

I want to thank you again for your input. All criticism is welcomed. In fact, it is exactly what I need.

Regards,
Phillip

 

[fallguy]

Hi fallguy,

That is just it. I don't. The idea is to be able to navigate through heavy weather and sea states; not to just submerge and wait it out.

The SVS cargo boats I observed, those boats that run awash, still make 20+ knots in heavy storm conditions. Not only did this strategy greatly reduce lateral stresses on the hull in big waves, it produces a very comfortable and stable ride for the occupants.

This design will never work as a true submersible. Everything will have to be simplified.

The concept I am attempting to develop is a hybrid aimed at a very specific market. I want to come up with a design that is attractive to middle-income consumers that wish to sail as long range, long-term, live-aboard Cruisers.

It is amazing the number of sailboat owners and crew I know that suffer from motion sickness. Those people that can 'gut it out' remain on the water. Those that can't, don't. So I love the idea that there is an alternative to traditional sailboats that can be affordably mass-produced.

I realize that with this design that trade-offs will have to be made. Sacrificing beam means giving up living space. I'm currently trying to work out the math for an elongated teardrop hull shape with control surfaces and a wave piercing bow. This is no easy matter for a novice such as myself. But that doesn't mean I'm going to give up.

If, in the end, this proves to be an unworkable design, so be it. But I'll never know unless I follow it through to its logical conclusion.

I want to thank you again for your input. All criticism is welcomed. In fact, it is exactly what I need.

Regards,
Phillip

Many sufferers of seasickness will get it from nearly no waves. This means they would get it on fair seas, long swells, and little chop. What you are proposing makes no sense if you are proposing it for said purpose. People that want to be on the sea want to be on the sea; not beneath it.

The only reason I would want to go beneath is to get away from danger.

I think you are making an effort at an undesirable solution.

There is a similar solution. This one 'enjoys' the water; then flies off in the face of 'heavy' stuff. It was more or less a flop.

Lun-class ekranoplan - Wikipedia https://en.m.wikipedia.org/wiki/Lun-class_ekranoplan

 

[Squidly-Diddly]

It is amazing the number of sailboat owners and crew I know that suffer from motion sickness. Those people that can 'gut it out' remain on the water. Those that can't, don't.

My understanding is:

1)Everyone CAN get seasick/airsick/carsick. I've never gotten seasick, or carsick since age of 5, but I did get airsick in Cessna touring the Grand Canyon and its bumpy air (didn't hurl, just felt really bad).

2)Those that do get seasick will ALWAYS adjust/recover in a few days, and it ALWAYS becomes a non-issue a few days out. That might not help typical sailboaters who spend a good deal of time less than a week out of port.

3)Anti-motion sickness drugs are cheap, effective and without major side effects, they just need to be taken ahead of time.

I'm guess that "Those that can't, don't" are about 3 hours away from full recovery when they throw in the towel. Motion Sick is a worse feeling than any flu or post-op, or hangover, I've ever had.

Several famous sailors, including no less that Admiral Nelson himself, suffered from seasickness (first few days out).Letter shows depth of Admiral Nelson's seasickness https://www.reuters.com/article/us-britain-nelson/letter-shows-depth-of-admiral-nelsons-seasickness-idUSBRE8BA0PP20121212

I'm thinking, instead of actual submersible, maybe a scheme to rig for heavy weather. Ballast down with Phat-Sacs, but make them secure enough to remain in place in case of flip, so they would help right the boat, not put it in S2. On top of the Phat-Sacs full of water, install Phat-Sacs full of air enough that if boat does flood you have more than enough buoyancy to keep any heavy keel from dragging everything straight to the bottom.

I'm nuts for anything that can be duo-purpose, so make the Phat-Sacs about 6'x1' logs. Use them for extra freshwater or even fuel. Add a few details and they could be lashed together to form floating platform, or filled with fuel or fresh water and towed behind the boat. I guess you could also use them to turn the whole boat into a RIB of sorts by mounting them on the gunnels filled with air.

 

[fallguy]

For the effort involved in a submersible sailboat; it'd be much easier to build a room that is motion free with gyros.

A capsule room like thing.

sorry Philip

 

[CocoonCruisers]

Many valid doubts here .. I think you can't escape quantifying

- Motion (The definition of 'comfortable ride' for a retired US exec spending 1M$+ on your specialty boat is probably not the same than for a gung-ho drug smuggler who was used to puke a whole week in a stinky 6-knot sub, and is now delighted with the 20knot speed that shortens the suffering, and reduces his chances for beeing shot by the US army from 30 to 10%).

- Efficiency. Guess i should have pointed that out in the first post, but 300+ hp at work for just two tons of payload at 20 knots are not efficient. Any carribean 3000$ Panga can do that with a single run-down outboard that was rated 120hp 20 years ago.

- Size and its relationship with weather, because surfacing, foiling or kissing the surface from below, you'll still cope with the waves in the ways pointed out in this pic: https://images.slideplayer.com/17/5344206/slides/slide_20.jpg . To get really independent from tha 10m waves in a real storm, you'd need a real sub, not a surfacing boat.

- Cost, because what you have described so far involves enormous weight leading to so much structure that you'd end up in superyacht territory (a few million $) and fuel bills in the thousands of $ every few days for an experience that is not much different in speed and motion from a big heavy bluewater sailboat that you can buy used for less than 100k$.

And defining:

- Usage. I fear that passagemaking is not the application that makes sense for this line of thinking.

- Competition: Have you had a chance to read up on the wavepiercing power trimarans ? On Dashew's FPB on setsail.com ? On SWATH vessels ?

 

[handyDanny]

NautiPhillip I come across your posts while researching deep draft or semisubmersible sailboat design. I was looking into building cast concrete deep draft sailboat. I was wondering what happened to you are you still alive. I hope you’re doing OK and I was interested if you made any more progress on your idea.

 

[handyDanny]

NautiPhillip here’s a Civil War era semi submersible torpedo boat similar to the design you was thinking of.
CSS David https://military-history.fandom.com/wiki/CSS_David