An extra-heavy-displacement 11ft long Atlantic Proa for circumnavigation

[artisguru]

I am currently designing an extremely unconventional sailboat, which we as a couple hope to sail around the world, and if we are successful, that would also set a new Guinness World Record for circumnavigation in the smallest boat.

I have been thinking through a lot of things on my own, and I would like to ask you, all the knowledgeable and experienced people on here, if you might be interested to discuss this design and point out any possible problems and difficulties in it.

As you can see from the attached drawing, the design is technically an Atlantic Proa (the one which always keeps the outrigger to leeward), but unlike conventional multihulls, it has an extremely deep draft and heavy ballast.

Below are my main design considerations.

The main focus of the design is to build a seaworthy boat which would move in a pattern that would cause the minimum amount of sea-sickness possible. Due to my woman being quite prone to seasickness, I see seasickness as the highest of all the risks why our circumnavigation plans might fail. And because of that, we are happy to sacrifice many other things, such as speed, draft, conventionally acceptable looks etc.

Here is my train of thought:
1) The boat’s design has to minimise any rolling movements, as they are the component which makes the brain seasick. Straight up-and-down movements doesn’t matter, because our brain is perfectly accustomed to them, since it is the same kind of movement which our vestibular system gets when we walk.
2) In order to cut out the rolling movements, the hull must be mostly submerged, float vertically and have vertical walls, which eliminates any shape-stability and leaves the vessel with mostly vertical movement in waves (like a pencil with a lead attached to its end, floating vertically, 3/4 submerged). That means extremely deep draft compared to its length and beam. The inspiration came from R/P FLIP (https://en.m.wikipedia.org/wiki/RP_FLIP).
3) In order to have a vertical hull which is still manageable under sail and sculling oar (without engine), it has to be extremely short and narrow, in my case: the length of 3.5m (11.5 feet) and the main hull beam of 1.1m (3.6 feet), with a draft of 4.5 m (14.8 feet). This kind of crazy contraption would have a fully loaded displacement of 12,780kg (28,175 pounds).
4) In order for such a hull to be capable of carrying at least a modest amount of sail, I add to the hull an outrigger. But as I want the minimum possible roll movement induced by the breaking waves of the Southern Ocean, I put the outrigger only on the leeward side of the main hull (hence the Atlantic Proa). That way the bashing of the steep wave faces would be taken by the main hull’s vertical convex wall, and the hull would respond to it mostly by lifting up vertically through the wave, instead of rolling over to the side. The back of the wave is not as steep, therefore the leeward-outrigger-induced roll should be relatively small. But for it to be still tolerable, the ama should not stick out to leeward too far- just enough to enable the unstable hull to carry a modest sail area, enough for a slow cruising.
5) As one of my big concerns is if such a hull would sail enginelessly at least as close to the wind as the old square riggers did, I minimise the windage by having a small above-water volume (compared to the excessive underwater volume), which makes this boat to behave almost like a surfaced submarine. I also streamline the pointed hulls and outrigger, and I take advantage of the proa design and make the leeward sides of the hulls absolutely flat and vertical, which will maximise the lateral resistance, as well as giving a hydrodynamic lift towards the windward side.
6) I plan for an enormous amount of storage space and load carrying capacity in the deep bilge, enough for carrying 1 year’s worth of our provisions. With this heavy design I can afford it, and also it would give us a lot of wiggle room in terms of where and when we re-provision. That is especially important since I don’t expect such a boat’s speed to average more than about 2 knots.
7) The deep draft’s imposed limitation regarding shallow anchorages should be more than outweighed by the ability to anchor further out and in rolly anchorages, or simply staying heave-to in the open sea, while still having a pleasant living conditions aboard due to the lack of roll.
8) In order to maximise the living space on the very short boat, I make use of it’s deep draft and create many floors. As an added bonus, we also get an extra room with underwater windows (like in the concretesubmarine.com), which always stays pleasantly cool, even while becalmed in the middle of Indian Ocean.

What do you think about such a design? Does anyone of you have some experience with anything remotely similar to this? Or does anyone have enough theoretical knowledge and strong imagination to be able to predict how will such a boat behave herself?

Thank you in advance for all your thoughts and input, have a great day!

Artis,

[neilpride]

Looking at the plans, it's not a boat, it's a sub....

[double u]

Originally Posted by www.artis.guru

I am currently designing an extremely unconventional sailboat, which we as a couple hope to sail around the world, and if we are successful, that would also set a new Guinness World Record for circumnavigation in the smallest boat.

I have been thinking through a lot of things on my own, and I would like to ask you, all the knowledgeable and experienced people on here, if you might be interested to discuss this design and point out any possible problems and difficulties in it.

As you can see from the attached drawing, the design is technically an Atlantic Proa (the one which always keeps the outrigger to leeward), but unlike conventional multihulls, it has an extremely deep draft and heavy ballast.

Below are my main design considerations.

The main focus of the design is to build a seaworthy boat which would move in a pattern that would cause the minimum amount of sea-sickness possible. Due to my woman being quite prone to seasickness, I see seasickness as the highest of all the risks why our circumnavigation plans might fail. And because of that, we are happy to sacrifice many other things, such as speed, draft, conventionally acceptable looks etc.

Here is my train of thought:
1) The boat’s design has to minimise any rolling movements, as they are the component which makes the brain seasick. Straight up-and-down movements doesn’t matter, because our brain is perfectly accustomed to them, since it is the same kind of movement which our vestibular system gets when we walk.
2) In order to cut out the rolling movements, the hull must be mostly submerged, float vertically and have vertical walls, which eliminates any shape-stability and leaves the vessel with mostly vertical movement in waves (like a pencil with a lead attached to its end, floating vertically, 3/4 submerged). That means extremely deep draft compared to its length and beam. The inspiration came from R/P FLIP (https://en.m.wikipedia.org/wiki/RP_FLIP).
3) In order to have a vertical hull which is still manageable under sail and sculling oar (without engine), it has to be extremely short and narrow, in my case: the length of 3.5m (11.5 feet) and the main hull beam of 1.1m (3.6 feet), with a draft of 4.5 m (14.8 feet). This kind of crazy contraption would have a fully loaded displacement of 12,780kg (28,175 pounds).
4) In order for such a hull to be capable of carrying at least a modest amount of sail, I add to the hull an outrigger. But as I want the minimum possible roll movement induced by the breaking waves of the Southern Ocean, I put the outrigger only on the leeward side of the main hull (hence the Atlantic Proa). That way the bashing of the steep wave faces would be taken by the main hull’s vertical convex wall, and the hull would respond to it mostly by lifting up vertically through the wave, instead of rolling over to the side. The back of the wave is not as steep, therefore the leeward-outrigger-induced roll should be relatively small. But for it to be still tolerable, the ama should not stick out to leeward too far- just enough to enable the unstable hull to carry a modest sail area, enough for a slow cruising.
5) As one of my big concerns is if such a hull would sail enginelessly at least as close to the wind as the old square riggers did, I minimise the windage by having a small above-water volume (compared to the excessive underwater volume), which makes this boat to behave almost like a surfaced submarine. I also streamline the pointed hulls and outrigger, and I take advantage of the proa design and make the leeward sides of the hulls absolutely flat and vertical, which will maximise the lateral resistance, as well as giving a hydrodynamic lift towards the windward side.
6) I plan for an enormous amount of storage space and load carrying capacity in the deep bilge, enough for carrying 1 year’s worth of our provisions. With this heavy design I can afford it, and also it would give us a lot of wiggle room in terms of where and when we re-provision. That is especially important since I don’t expect such a boat’s speed to average more than about 2 knots.
7) The deep draft’s imposed limitation regarding shallow anchorages should be more than outweighed by the ability to anchor further out and in rolly anchorages, or simply staying heave-to in the open sea, while still having a pleasant living conditions aboard due to the lack of roll.
8) In order to maximise the living space on the very short boat, I make use of it’s deep draft and create many floors. As an added bonus, we also get an extra room with underwater windows (like in the concretesubmarine.com), which always stays pleasantly cool, even while becalmed in the middle of Indian Ocean.

What do you think about such a design? Does anyone of you have some experience with anything remotely similar to this? Or does anyone have enough theoretical knowledge and strong imagination to be able to predict how will such a boat behave herself?

Thank you in advance for all your thoughts and input, have a great day!

Artis,

AAA for trolling effort! (much to thick laid on though, u will not brake the record!

[artisguru]

Originally Posted by neilpride

Looking at the plans, it's not a boat, it's a sub....

Yes, you may call it like that, I don’t mind at all.🙂

[artisguru]

Originally Posted by double u

AAA for trolling effort! (much to thick laid on though, u will not brake the record!

Would you mind expanding on it please? I’m curious if you may see something which I don’t. Have a great day.

[Rucksta]

Originally Posted by www.artis.guru

Would you mind expanding on it please? I’m curious if you may see something which I don’t. Have a great day.

Ventilation

[artisguru]

Originally Posted by Rucksta

Ventilation

Thanks for the comment. Yes, I have been thinking about that. My plan is to have the ventilation done through the unstayed masts. On top of the masts would be dorades, facing the opposite directions on each mast so that one of the masts funnel the air in and the other one sucks it out. Then the air would flow through the mast itself as through a pipe. At the mast base would be a siphon with a drain back to sea. From the siphon the air would go through the ventilation pipes to the lowest underwater room, which is at the highest risk of accumulating too much CO2 without ventilation. Just before the air exits in the room I would install a heavy duty valve on the pipe (like the ones made for the extra thick water-pipes), so that I can slow down the airflow during heavy weather, or close it completely in an emergency. The pipes can be made as thick as the masts, and the dorade funnels can be made big enough to have more than enough airflow through the saloon. Plus during calm whether our hatch will be open too, equipped with the Hassler hatch cover, which actively sucks the air out from the saloon. All of that combined, I hope should be more than enough to keep the boat well ventilated.

[Chotu]

I love looking at things from a new perspective. It’s fun.

One thing I’m not understanding is how you go from one level to the next. I don’t see the stairs or ladder area or whatever.

Also, how do you get three stories out of 14.5-16 meters of height? Seems like crawling room only in places?

That kind of draft will also keep you out of the majority of harbors and nice areas to cruise but I can see you are willing to accept that.

I don’t know if I would call this a proa . I would call it a small oil rig.

But apart from those questions, there are concerns. And here they are:

Where does the dinghy go? You talk about anchoring way way out and being able to go ashore, how do you get ashore? There doesn’t seem to be a provision for that.

2kn of boat speed. Sounds completely unbearable to me but to each their own. Going that slowly will put more force on the sails than you would expect because they will be loaded up in even small wind. Apparent wind will always be high and coming from aft. So maybe in the real world the float goes forward. Maybe. This won’t go to windward at all. It’s basically going to drift downwind and at 2kn, it’s probably going to simply drift with the currents. You won’t have much control over where you end up.

Psychologically, this thing is scary. Like a prison cell. Is the wife ready to aimlessly drift around in this tiny area with 2 people for extremely long periods of time?

What about not getting run over? No one will see you mostly underwater. Where does the AIS go?

Power generation? Water storage or water maker? You need 4000 liters of water for that year of food conserving heavily.

Holding tanks? Batteries? Steering mechanism (probably not useful anyway since currents will take you)? Rig?

Propane or generator for cooking?

Finally, what material is this made from?

[massnspace]

Going to take 5-6 years to make it around in that thing…..and that’s with following winds….

[longjonsilver]

Originally Posted by double u

AAA for trolling effort! (much to thick laid on though, u will not brake the record!

But he very well might break the record

[Shrew]

So, so many things don't make sense with this design.

- Where are the passages between spaces?

-? 2 stateroom? There are two people on this adventure and the 'Wide Stateroom' appears to have you rubbing your nose on the ceiling as you lay down.

-Underwater windows are a fanciful, yet completely unnecessary design element. From an Engineering perspective, its borderline ridiculous.

- At 2 kts, it would take upwards of 60-80 days to cross the Atlantic. Where are you storing enough provisions for that amount of time?

- how are you generating power? Your going to need lights and to be able to power nav and comms equipment.

[wyb2]

Originally Posted by double u

AAA for trolling effort! (much to thick laid on though, u will not brake the record!

OP may be pulling legs, but this strikes me as too interesting a thought experiment to call it trolling. Trolling is about entertaining the troll by inciting frustration/anger in everyone else. Making up some BS that entertains everyone is more just...entertainment.

Originally Posted by www.artis.guru

...
The main focus of the design is to build a seaworthy boat which would move in a pattern that would cause the minimum amount of sea-sickness possible. Due to my woman being quite prone to seasickness, I see seasickness as the highest of all the risks why our circumnavigation plans might fail. And because of that, we are happy to sacrifice many other things, such as speed, draft, conventionally acceptable looks etc.

...Does anyone of you have some experience with anything remotely similar to this? ...

No experience with anything remotely similar as far as vessel (obviously). But I do have experience with living on a boat as someone who gets seasick. I can all but guarantee this will go one of two ways, regardless of vessel design. 1: person adapts to the motion and stops getting seasick for the most part. Or 2: the trip ends quite quickly.

As I understand it, even submarines can experience a fair bit motion when near the surface.

[Lee Jerry]

I'll add a few comments that jump out at me:

Motion sickness is more complicated than this. It's not just rolling. For example, cars don't roll (to any great extent) and yet people get car sick. So you may not actually be solving the problem with this contraption. I'd say that different hull forms can have different comfort levels, but predicting or designing for sea sickness is very difficult. The two are not the same.

What is the construction material? Regardless, you will lose interior space to structure, making your arrangement even tighter.

You don't mention steering. At 2 kt (if you can even make that, you don't mention the rig much), you'll not have great control. A large rudder will help a little. If it's an external / transom hung rudder, this will add to the overall length. Do you still meet your record length? Control cables generally run internal, eating up space. If external, exposed to the elements.

What about self-steering? Or are you going to hand steer the entire way?

You don't show any tankage. At a minimum you'll need potable water and black water tanks. You can't discharge at anchor or in coastal waters.

Which brings up another (rather large, IMHO) issue - variable loads and draft changes. This is particularly of import w.r.t. the "small" outrigger. You give a full load displacement, but what about lightship? Your immersion is about 160 lb/in. How much will the draft change when you've consumed half of that year supply of provisions? Is the outrigger still in the water? Are you going to take on water ballast to compensate?

Another big concern is the "spar buoy effect" you're going for. While your goal is improved motions (which you may or may not achieve), I think this has dangerous effects in heavy weather (i.e. seas). With the heavy weight for size, she won't rise to the waves the way a lighter, more conventional craft of her size would. This means that waves will be crashing into the hull and ONTO the deck. This makes it unsafe for the crew to be on deck and a huge risk to the rig and anything else up there. Solar panels would have to be deck mounted; no arch for you.

These are some brief comments. Hopefully I've mentioned enough detail to get the point across without writing a book.

[boatpoker]

Absolutely cannot wait for Jeff_ H to respond to this.

[wholybee]

Do you have any experience in yacht design, or have any understanding of how a sailboat works? You seem to have focused entirely on the living space, and given no consideration to how the boat will actually sail. What I see is something that might (if you add a sail) get pushed around by the wind, but I don't think you will have any control over it. And with more wetted surface under water than some boats of that size have as sail area, ocean currents might often be a larger driving force than the wind.

If you want to do this, start by ignoring the living space, and design a boat that is 3.5m LOA that is sound and ocean worthy. Then figure out how to live in the small space. Ocean going sailors in much larger boats have done without having a "shower" or "kitchen" so don't expect to have those things if you are trying to set a small boat record.

The last person to attempt an ocean crossing in a weird shaped small boat didn't even make it a single day.