Wanting to build a ~50ft aluminium power catamaran, and looking for others who'd like to build in parallel

[Rycochet]

So this has been a dream ever since Waterworld came out (don't look at the date lol) - and finally decided to actually follow through with it. I'm now 50, with the AuDHD skillset that covers a good proportion of what's needed - but something like this would be a huge job for me (and partner when I persuade her it's actually good to go) - finding other people who could see themselves building the same base design in parallel so we can share skills, workloads, and knowledge... Feels like it would help and be good for everyone - even if it's joining in as a collab effort and getting the ideas back out (strong proponent of Open Source software etc too).

Currently I have a framework of designs, that I'm slowly putting down on paper (well, keyboard), and doing deeper dives into specific parts (including future prototyping for some proof of concept ideas).

The rough idea:

• ~50ft aluminium catamaran.
• Currently looking at Kenya (Mombasa or similar) - they speak good English (my brain does computer languages and not spoken ones), have cheap labour, and are getting more skilled people every year, plus the Kenyan government makes it far easier to build there.
• All electric (with backup generator, not a hybrid drive system), solar and wind turbines, plus plenty of battery.
• Laser welding - get at least some of the solar panels and batteries to bootstrap power generation for it and save costs (also far lower skill required than getting MIG and TIG welding experience).
• 48V power backbone - similar to SV Delos - but local stepdown to 12V / 5V (usb) and fully digital switching, so saving a lot of weight / cost from unnecessary wires
• Centralised thermal management (aircon and more) - ie, using a closed loop heat distribution system and large freshwater tanks for thermal mass - one each for hot (washing) and cold (drinking), so only a single heatpump between them should be required. This will also use multiple locations around the boat for heat / cool heat transfer via aluminium pipe welded to the hull, including keeping the solar panels at a more optimum temperature when in hot weather.
• Propulsion needs a proof-of-concept to test energy efficiency - looking at similar to a Voith-Schneider Propeller - with more control than the standard mechanical linkage to allow the fins to act as rudders when not driving the boat (if the proof of concept puts it as too "expensive" in power use then back to some form of standard prop).
• Have a sailing kite as a non-electric propulsion system (even if not fitted initially, I feel integrating it in the design stage gives the right strength at the right locations). Yes this does use electricity to run...

My plan is to go for a circumnavigation in it after being built, but to take plenty of time, and keep (mostly) in warmer climates as both of us are feeling the cold in the uk now (well, except for this current heatwave!)

I'm not looking at building anything before 2027 at the earliest (beyond proof of concept scale tests etc) - but want to have a pretty good digital model / blueprint ready before paying a professional boat architect to tell me what's wrong and fix it (hopefully minor things only!)

 

[montero]

Lots of electricity and the ocean don't sound like a good combination. Why would you want to use so much electricity?

I know of only one reason to use anything electric on a boat. Besides a media , navigation, and communication.

 

[Rycochet]

Lots of electricity and the ocean don't sound like a good combination. Why would you want to use so much electricity?

I know of only one reason to use anything electric on a boat. Besides a media , navigation, and communication.

Diesel is a finite resource - I don't just mean ecologically, but also in terms of having an ongoing cost to refuel and having limited storage for it onboard. On top of that you need to keep mechanical components such as engines running, and be aware of diesel bug so having a scrubbing system in place (mostly in more out of the way places, but that's not an exclusion).

Sails work well - until the mast breaks, or you tear your sails, or you suffer an injury (or are already disabled) and can't use them. That's assuming the wind is blowing

But both of those (propulsion) negatives also have corresponding positives - diesel is available almost everywhere and is high energy, and the wind is free.

Well designed electrical systems don't care whether they're on land or on the sea - and most people with any background in electrical engineering can see the potential problems - keeping it under 60V or so handles the personal safety, although needs more thought put into the power distribution. Modern batteries aren't in any danger from salt water, and making the right choice also removes the danger of fire (lithium battery fires do exist - but hopefully anyone with lithium batteries on a boat is already using the correct type, or looking at replacing them).

From what I can see a significant proportion of liveaboards already use solar / wind + batteries to give a more comfortable life, from food preservation (fridge / freezer), to air quality (aircon / heater), and entertainment (internet / tv).

My personal view is that I'd like to do this with as little running and maintenance costs as realistically possible. Reduce moving parts and mechanical complexity, and make more use of tried-and-tested electrical systems where my yearly (boating, not living) costs come down to insurance and cleaning - whether anchored up somewhere or sailing thousands of nautical miles.

Also - somewhat broken body that really wouldn't be able to be consistent with rigging and sailing for long passages - and I'm not gambling safety on "am I capable of this today?" - which also is very valid for mechanical issues (even on a twin engine).

We all have preferences for those things we know, and there's a lot of people running various levels of electrical systems on their boats (those electric dingy motors are getting really nice!)

 

[bajansailor]

Have you got a design in mind, or are you going to design it yourself?
If the former, can you provide any links or details?
If the latter, bear in mind that just the design work required for building a 50' ally cat of this size is going to be considerable - and you will need to keep an eagle eye on your weights, as it sounds like you will be adding a lot of outfit items (all of which add up quickly to lots of weight - and the hulls need enough buoyancy to support this weight).

 

[montero]

I remember a passage in Alistair Maclean's book where he curses spark-ignition engines in marine use.

But the insulation and reliability of gasoline outboards, for example, are currently high.

What main engines are you planning? What main batteries?

 

[Rycochet]

Have you got a design in mind, or are you going to design it yourself?
If the former, can you provide any links or details?
If the latter, bear in mind that just the design work required for building a 50' ally cat of this size is going to be considerable - and you will need to keep an eagle eye on your weights, as it sounds like you will be adding a lot of outfit items (all of which add up quickly to lots of weight - and the hulls need enough buoyancy to support this weight).

Currently it's "pieces of designs" - lists of requirements and reasons for choices that overlap with multiple current cats - SV Delos 2.0 is the possibly the most visible modern aluminium sailing cat, and that's not far off above the water - but removing the sailing parts allows for slightly different lines, and differing propulsion (if tests work the way logic dictates ) will change things underwater.

(Note that I'm still writing these things down, and translating the ideals into actual text that people can follow - hence wanting to find others that are interested in helping)

I want to get this into a collaborative project on Github or similar, and when it gets onto actual design software have the actual plans on there too - but nothing is going to get made without paying an actual professional to go over it and make sure there's nothing obviously "wrong" (I'd like this to be like an open-source plan, so anyone can make their own).

Dropping the mast and rigging should reduce the weight by close to 100kwh of lithium batteries - and a good power backbone would allow the battery weight to be distributed better. Hopefully the design program can get all these things incorporated for raw numbers!

I remember a passage in Alistair Maclean's book where he curses spark-ignition engines in marine use.

But the insulation and reliability of gasoline outboards, for example, are currently high.

What main engines are you planning? What main batteries?

Motors and batteries are TBD.

I've got a leaning towards blade type batteries, and BYD is hoping to get solid state blade batteries in the next couple of years - but even their current gel lithium blade batteries are puncture safe -

For electric motors somewhere around the 20kw range - though normal "working" power should be around 6kw.

Electric dingy outboards are coming along, but diesel is definitely the fuel of choice for both backup generator and potential backup dingy outboard - why have 3 energy sources when 2 will do?

 

[Rumars]

I'm not looking at building anything before 2027 at the earliest (beyond proof of concept scale tests etc) - but want to have a pretty good digital model / blueprint ready before paying a professional boat architect to tell me what's wrong and fix it (hopefully minor things only!)

IMHO you are looking at this backwards. Hire a NA to design you the boat you want since "checking" a design will be just as expensive. If you want it to be open source afterwards, pay to have all rights for the design not just an individual building licence, then you can release it on the internet.

A few observations: it doesn't matter where it's buildt or what's it welded with, this is a question of price. You contact a yard they give you a price and it's irrelevant to you if they cut the pieces with a hacksaw and trim them with a file, or the brand of welder they use. All that matters is quality control so they deliver what's in the plans. Anyway, welding a hull isn't even half the way to a boat, the fitout and technical systems are. Whoever does your boat needs to either have this expertise or be able to access it and the relevant stuff to install.

Digital switching is a preference, but I doubt a 50ft cat is big enough to see any significant weight savings.
To my knowledge there isn't any Voight-Schneider unit made for such low power but I could be wrong.
I presume with your central HVAC you mean some sort of heat pump system, that's going to be an interesting thing to see on the hot water side.
Wind turbines are useless, concentrate on solar.

You should focus more on the basics, how much space to live for how many persons, how many toilets, how much kitchen counter space, flybridge yes or no.
On the technical side you are limited by how much solar you can install, how much battery you can afford and how heavy the vessel ends up.
You need to decide what you prioritize, for example a lighter vessel can do more with the available power, both electric and kite. Building lighter in aluminum is more difficult and may even negate some of the perceived benefits of Al.

 

[Rycochet]

IMHO you are looking at this backwards. Hire a NA to design you the boat you want since "checking" a design will be just as expensive. If you want it to be open source afterwards, pay to have all rights for the design not just an individual building licence, then you can release it on the internet.

That's actually an argument that I *am* looking at doing it the right way - being able to have a full set of blueprints in 3d space where every detail exists makes it easier to flesh out the design - especially if the cost is the same.

A few observations: it doesn't matter where it's buildt or what's it welded with, this is a question of price. You contact a yard they give you a price and it's irrelevant to you if they cut the pieces with a hacksaw and trim them with a file, or the brand of welder they use. All that matters is quality control so they deliver what's in the plans. Anyway, welding a hull isn't even half the way to a boat, the fitout and technical systems are. Whoever does your boat needs to either have this expertise or be able to access it and the relevant stuff to install.

I'm not contracting a yard - I'm renting a space and building myself - I know my wife has very few transferrable skills, so I would also need to project manage and employ 1-2 other people to help with the build at various times - plus I do have the majority of the transferable skills for that. Laser welding reduces the skill level needed for welding (one that I have no experience with), as well as significantly reducing the running costs of welding by bootstrapping the solar generation / batteries as a source of power for it. Welding is the most visible "we've got a boat!" moment (even if it needs the fitout to be more than a bucket )

Digital switching is a preference, but I doubt a 50ft cat is big enough to see any significant weight savings.

I don't see there being a lot of saving of weight there (but I feel it'd be a non-zero saving) - I do see a reduction in complexity for the fitout - running conduit and wires for a boat "should" be simpler than a house (albeit one with different liquid handling requirements ).

To my knowledge there isn't any Voight-Schneider unit made for such low power but I could be wrong.

So I've not seen / found anything with details, but in the back of a Sailing Uma video at the MetsTrade show 2 years ago there was a single cut of a similar drive, and a French company was also demonstrating something that looked different to that around the same time (but their website is non-existent now) -

- one claim in that was a 10% energy saving, but my brain feels that the energy use would be related to the amount of water moved (so take the formula for normal prop energy use, and do something based on the surface are of the VSP fins, together with the angle of attack into the water and speed - and I feel you could find a formula to solve and give equivalent thrust).

I presume with your central HVAC you mean some sort of heat pump system, that's going to be an interesting thing to see on the hot water side.

100% - in perfect weather it would purely run off water pumps and transfer temperature between different surfaces, but for extra heating and cooling a heatpump (and probably an EV car heatpump at that) should be able to handle things... Another one for some maths to figure out the exact numbers...

Wind turbines are useless, concentrate on solar.

I was considering one or more retractable vertical wind turbine types (ie, not propellor based) in the corners above the bridge deck - if they were 2-3m high (on top of the distance above sea level) then they should each be able to provide maybe 500-1kw of electricity - the same as 1-2 solar panels - but they would be able to run at night and provide extra power when the weather isn't being friendly to the sun - I'd prefer to have that than a backup generator, but will definitely take input and discussion!

You should focus more on the basics, how much space to live for how many persons, how many toilets, how much kitchen counter space, flybridge yes or no.

Personally wanting an "owners hull" type, with 3 double bedrooms, and a toilet for each, somewhere around 3-4m of counter space (including sink etc), no flybridge - but digital cameras in higher locations to allow easier visibility (hopefully including IR / UV modes to be able to see in bad weather / at night).

The plan is to offer crewed charter in the future, as well as having friends and family come to stay - so extra bunks and sleeping spaces are needed too.

On the technical side you are limited by how much solar you can install, how much battery you can afford and how heavy the vessel ends up.

Yep - solar panels are getting better every year, but it's now at the trickle level of improvements. Batteries are hopefully getting a jump *very* soon with solid state (lots of things happening in the pre-manufacture space, but not much in consumer space yet though - should still be able to do 100kwh with it weighing around the same as mast + rigging... Double that with the next jump in batteries...).

You need to decide what you prioritize, for example a lighter vessel can do more with the available power, both electric and kite. Building lighter in aluminum is more difficult and may even negate some of the perceived benefits of Al.

Safety first, comfort second, speed third. Although I do want to go right the way around the planet that's in a relaxed and "ooooh, I want to stop and see that!!!" way. I'm currently estimating around 6t for the empty hull, guestimating another 5-6t for the fitout, then another 1-2t for full water tanks (thermal mass requirements - when I look at the maths)... Pretty much every number there will probably be wrong - but good design software should be able to give far more accurate numbers as its designed.

 

[montero]

Why do you think laser welding will help you build such a large boat?

 

[Rycochet]

Why do you think laser welding will help you build such a large boat?

The end result will be near identical no matter what welding is used - the benefit of laser welding is that it can self-feed with filler, so the skill to create a good weld is significantly lower, and the speed of welding is significantly higher. That also matches with the lower power draw, so it could actively use the solar panels and batteries that will later be fitted to the boat, and reduce power costs / reliance on mains electricity.

Additionally it can both cut and clean - so any pieces that aren't CNC'd by the aluminium supplier can be done easily, and no need for massive amounts of sanding and grinding for any areas that want a protective coat painted on.

 

[montero]

Did you weld antything ever ?

 

[Rycochet]

Did you weld antything ever ?

As I said above - nope... I did spend quite a while soldering with industrial electronics - but that's the closest I've been to "get two metals hot and stick them together with another metal"

 

[montero]

It's quite different game especially with big elements . What kind of AL are you thinking of using it?

 

[Rycochet]

It's quite different game especially with big elements . What kind of AL are you thinking of using it?

5083-H116 https://atlassteels.com.au/wp-content/uploads/2021/08/Aluminium-Alloy-5083-Data-Sheet-24-06-21.pdf

From everything I've read this is the best to use for salt water environments, although having a fully isolated hull and no metal mixing should let it last a long time (Sailing Dawn Hunters have a ~20 year old cat that is "standard" aluminium and has no corrosion).

 

[montero]

Forming large pieces of sheet metal is no easy task. Welding them is even worse.

Why are you insisting on an aluminum hull?