Help me choose the best boat type to design?

This is what I need in a boat to be used for global travel:

*ease of build - I will build the boat myself, learning as I go, and starting with hardly any tools, and zero boat-building experience.

*energy efficiency - it needs to be fast where needed like a catamaran, but also like a hydrofoil.

*comfort/stability - again, like a catamaran. I really do not want to be thrown around inside a monohull for weeks at a time.

*speed - it needs to out-run any hostile craft.

*cost - the cost needs to be low. I will design and build the boat myself.

*strength and survivability - perhaps the most important. The boat needs to remain functional after being struck by large waves, grounded, and so on. It needs to be easily repairable at sea if necessary (welding equipment can be carried).

*radar signature - visibility of the boat on radar is a factor. How visible is a 40-foot boat made of aluminium, or steel, or steel coated in fibreglass?

This is not a leisure craft and it's not a racing craft. It is purely for long distance travel under all kinds of conditions. I have been thinking of a catamaran design with retractable hydrofoils propelled by a Z-drive, which also has a folding mast so it can be used under sail. It consists of two hulls that connect via retractable hydraulic arms to a central capsule. The capsule houses the living area and is from where the craft will be controlled. The hydraulic arms are to allow the craft to shrink in envelope for transport and storage reasons, but also to reduce structural stress during a heavy storm. They could also facilitate amphibious operation - the craft can, essentially, walk up a beach in the same way a heavy crane or mineral extracting machine can walk (the capsule/central body sits down while the two hulls simultaneously lift, move forward, are lowered, and the central part rises, moves forward, is lowered, and so on).

This thread is to gauge opinion on this, and to seek better ways of going about this project. The only real issue I have is structural strength (the other issues are, of course, very important still). Two slender hulls connected to one another via a central capsule at the ends of four hydraulic arms will be very vulnerable to snapping under heavy wave loading, and heavy waves are an inevitability. Moving the two hulls closer to the central capsule will mitigate this slightly, but likely not enough unless they are then braced together somehow with removeable braces/temporary structural members that are stored while not in use. Would this bracing (connecting the bows together with a tie rod, and the same with the sterns with a second such beam) be sufficient to prevent structural failure during a storm? In essence, the boat will have a protective storm mode/configuration so that it is more resilient while in extremely bad sea states.

Thanks in advance for your input. My intention over the coming months is to focus on designing this boat, beginning with a lot of study, but I should be grateful for a good starting point. This is actually a project I've had in mind for a long time, and now its time is about to come.

 

The questions you are asking are very fundamental. To get to the point that you coul design a good boat will take several years. It is a typical amateur desire to design a boat. However, the cost of a stock design is a minute percentage of the cost to build the boat. Also, it will come with instruction on construction, a list of materials and other very valuable information. The complex mechanism you describe is the opposite of what a long distance cruising boat that can be repaired and maintained in remote locations should be. The key to surviving at sea is experience and good seamanship. Most boat projects started by inexperienced amateurs reach the point where the builder realizes that he has made more mistakes than less. At that point the projects are usually abandoned. I strongly advise you to buy a used boat and go to sea. You romantic idea of sailing may come apart the first time to get hit by a gale.

 

Awe geez another one, I get it the home island looks like it could get sporty in the future....

Gonna cherry pick and answer a few in bold just for kicks.

Could probably pick one or two of your goals and hit them, all will require bending physics or need a budget only available to major governments.


Don't want to be dismissive, seems like we're getting a UK viewer every few months or so wanting a "get outta dodge" machine. Obviously there is a cultural phenomenon pushing this and I don't want to be unsympathetic to it. However a man's gotta know his limits.


I've been involved with boats professionally for my entire adult life, have worked in shipyard and on my own projects from a family who built boats and was in the trades. Have stripped and rebuilt hulls, fit out and adapted hulls, assembled boats from other peoples plans and dedicated full winters to reading and studying hull design. My shop has all the tools to build a boat, hundreds of thousands of dollars of specialized tools bough over decades of boat ownership and repair.

My first truly "me" built boat, my design, build and everything will be a dingy this fall....

I know enough to know what I don't know.

Define a very specific realistic vessel parameter, and go from there.

 

@Infinitus if this is not simply a very elaborate wind-up on your part, and you are absolutely dedicated to the goals mentioned in your post, then please take the very good advice offered above by @gonzo and @comfisherman

Dare I ask if you have done any sailing in the past at all? I have a feeling perhaps not. If this is the case, then do a one week sailing holiday course somewhere (or even a weekend introduction course) - you should be able to find something suitable on the RYA site -
RYA courses and qualifications https://www.rya.org.uk/training

If you have never been sailing before, I would suggest starting off by doing a dinghy sailing course - IMHO this is the best way of learning the fundamentals. If you jump into a yacht one time, and it is bristling with electronics, you can become too dependent on them.

Once you have had some experience of sailing on yachts, then revise the specification for your ideal yacht, based on your experience gained. I think that many of the desirable features mentioned will then be binned. But nobody can tell you that, you really have to find out for yourself.

 

Hi infinitus, have a look at your requirements one by one, and assess, quantify, and do a cost analysis with cheapest components available.
Ease of build with no tools or experience to begin with means over build it = heavy, slow, and expensive. Tools alone aren't cheap.
Energy efficient: look at that after you have quantified some things like energy needs of pumps and control equipment.
Comfort/stability, take a 25 to 35 foot catamaran out on heavy seas for a day and see how you feel, just a mild gale will do.
Speed and out running any hostiles: hostiles these days can run 40 foot speed boats with 4 or 5 massive outboards on the back, toting AK47's and missiles. It's not 'Pirates of the Caribbean' anymore.
Low cost: do a cost analysis of any of your requirements and your head will spin.
Hydraulically 'walking' trimaran: strong heavy bottoms, and sides, and bracing, and pivots, and mountings = heavy and slow; marine grade hydraulics = expensive, heavy, and power hungry; pivots and pins for surviving a heavy load in a storm = very heavy, and expensive maintenance; dual axis pivots = double the weight and the hydraulics expense at least; Solar and battery to run hydraulics = heavy and expensive.
Riding on retractable foils: now you really are dreaming.
I can see over a million dollars expense there, and a few tons of weight, for an inadequate prototype prone to failure and self destruction.

Or build a model 1 metre / 1 yard long first, and see how it breaks.
If it was possible, we would all want one, and a billionaire would have a factory making them. Navies would have them.
It's a nice thought, but re-think it. Sorry infinitus.
I'd love a big cat like in the movie 'Water World', but the cost of that simple boat is quite high, and it wouldn't survive a big storm.
We're not trying to put you down, we're trying to save your life, re. wasted time, wasted funds, loss of wife - G.F., etc.
Keep it simple, and have fun.

 

Back in 2011, you were a final year Mechanical Engineering student.
With 13 years of engineering behind you, you should have realized that all is (just about) possible.
BUT your requirement that it be "cheap- the cost needs to be low, I will design and build the boat myself."is the limiting parameter.

FYI:Infinitus started a similar thread in 2011, Submersible, Convertible, Hydrofoil Cat

Com's quote below is something that you should have learned by now.

Words of experience and wisdom

How much money do you have to spend????

 

Rumour has it, inflation in the UK has finally started impacting cocaine prices in London.

I see 2 things that immediately put his concept out of the realms of possibility, "low cost" and "home build".

A modified aluminium Mumby cat would be a good starting point, or just forget the dream of outrunning bad guys in 60 knot Pangas .

 

Thanks. I, with very few exceptions that usually cost $millions, am yet to see any boat that I would desire to own and trust. There are countless examples of dismastings and the need for ocean rescues involving boats priced more than good houses. The main reason for designing my own is to make sure I have something that is tough, unlike the overpriced plastic rubbish that Champaign-sippers go for. The boat I need must be functional. Boats are typically too incapable of anything but summer cruising, or marina entertainment.

 

Thanks. Yes, the UK is becoming, for everyone within it, that which Germany became for the Jews in the 1930s, and I am deadly serious. It is time to leave this place, but this is actually an idea I’ve had since the 1990s, and I’ve been a member of this forum for 16-years. During the past couple of decades, I studied and became qualified in mechanical engineering, so I am confident in my design abilities to produce something that will be good enough for me personally, if not for any customer.

To address some of your points:

Naturally, I would like the boat to be suitable for the roughest weather during the worst months. However, I will, of course, plan navigation as best I can to optimise weather and sea conditions for any voyage.

It's more the pirates I’m concerned with rather then avoiding drug smugglers. I think a hydrofoil capability with a reasonable-priced engine should allow for 50 kts, which would give me confidence in escaping most situations should I fail to avoid them occurring. The hydrofoil aspect to this concept is the one part that is most likely to be dropped on account of safety concerns pertaining to developing a control system for it. However, I will investigate the idea because hydrofoils make a lot of sense, and there are many varieties to choose from if the most efficient type proves impractical.

One way or another, this project will be realised. I also, recently, acquired a sewing machine, and will make my own clothes. Would anyone else wear anything I will make? No, but if they are comfortable and fit well enough, I’ll be happy. Same with the boat.

 

Thanks. I have limited sailing experience, but this is not about developing a hobby. It's a means to an end, and as I want to be somewhere thousands of miles away, and I have a flying phobia, this is the way to go about solving the transportation problem. If it floats, can be steered, will be affordable, and survivable, then it will, ultimately, be as good as it needs to be. Luxury is for weak people.

 

Thanks. I understand, but there are many ways to go about things. I don't believe that the lack of any technology in common usage always means that it is not feasible. Things often do not exist because of cultural reasons rather than a lack of technical capacity, or because the monetary cost would be too great. Often, billionaires are not innovative or creative people. Just look at the standard, boring boats they commission. They are floating Champaign bars for narcissists, and they pretty much all look alike - Zuckerberg's new yacht is a case in point, which is just another floating plastic entertainment centre that should probably not be exposed to bad weather. I think it's fair to say that the typical billionaire is someone that knows how to exploit others and profit greatly from having done so. It's the people they exploit that, typically, come up with the ideas. However, having said that, if any billionaire reads this and wants to be involved in an interesting project, please get in touch.

Hydraulics need not be expensive. The working principles are very simple, and I could design a system for a local machinist to produce for just a few £hundred. If the arms are covered/protected then special marine materials will not be as needed, especially if they are regularly stripped, cleaned, and re-greased. Weight can be saved in other areas of the design to compensate for any excessive weight in the arms. The arms could even involve exotic material (titanium, carbon fibre) if the weight is too excessive. The beauty of designing and building a boat, or anything, oneself is that far more becomes, economically, a realistic option. Although I have not built a boat, in other areas I could have spent £thousands commissioning professionals, but spent but a fraction of that cost by doing things myself and buying cheap eBay tools. Yes, some such tools are rubbish but with a bit of careful choosing it is realistic to buy tools for a tenth the price of tools that snobs would insist upon, and these tools will last long enough. My drill cost me £20 from a local shop years ago, and it still works. It wouldn't offer sufficient precision for a space probe, but for my projects it's been fine.

If the craft will, ultimately, have a walking capability, it is most likely that "legs" will be secured in position rather than subjecting hull surfaces to such abuse as walking up a stony beach. I would not rely on PVs to provide power for this but the boat's engine, or a separate generator. Years ago, I had the value of 14-tons in mind for this project. There are cheap engines around for just a few £thousand capable of several hundred horsepower, which could be marinized. The greater the cost, the greater the luxury, but low-cost can still allow for things to happen. I'm going to keep it as simple as I can.

 

Thanks. Yes, I've been focused on other things since graduating, and mostly they did not involve mechanical engineering. I have, for now at least, dropped the submersible part of the idea, and am prepared to drop the hydrofoil part as well if the control system proves too difficult (perhaps ChatGPT could design one...).

TBH, I always aim for minimal budget, but the ultimate amount I spend will be determined by what it costs to achieve the aim.

 

Thanks. I'm not sure what cocaine prices have to do with this, but I do know that Bitcoin is inflation proof.

Low cost and home build are the two things that bring this idea well into the realm of possibility. How much would a design and manufacturing company charge to facilitate this ambition compared to the cost of doing it for oneself? I built my own furniture. I expect no one would buy it, but I'm happy with it, and it serves me well. Had I commissioned it, the cost would have been £thousands instead of a couple of hundred £s for bespoke items that fit my room very well.

The Mumbys look a little under-spec, as far as I'm concerned, and I certainly would not want to pay $hundreds-of-thousands for one.

 

If you are looking for design inspiration, there already is a boat out there that ticks most all of your boxes. Safehaven Marine's T-2000 catamaran.
50 knot plus speed capable, hydrofoils optional, all weather capable. comfortable motion in a sea way, long distance voyager.

 

Infinitus, welcome back.

So, you're blaming the equipment and think you can do better.
This is foolish and naive.

Best of luck to you.