Want to design only a top part of catamaran, looking of plans for hulls 14m, aluminum

Hi!

Got some savings over the years and recently thought to start to build an aluminum solar powered catamaran.

It is not tons of money, but from my rough calculations I should be able to afford to build a 14m aluminum solar powered cat. I'm total newbie to building boats so here will be my couple of questions that I'm curious of:

1. Software: what software you find best to design yachts (free or paid, but if paid lets keep it reasonable price)?
2. Would be actually happy to get ready design of hulls, where I could just step in and do design of the top part of boat, any recommendations where I can find such a designs that I could only adapt to my needs (14m, aluminum, ocean crossing)?
3. If it is gonna be a catamaran and will have 2 electric motors that can drive back and forth each separately then do I still need a rudder?
4. What is the minimum speed to maintain in storm conditions on such a boat?
5. What would be recommended clearance between bottom part of deck and water level?
6. Anyone else building an aluminum boat?


Will be glad if you drop a line of comment, link or anything else about above questions

 

Welcome to the forum Daniel.

Quick simple answers to your questions:

1. Any - which ever YOU find easy to sue. There are many out there but each takes time to learn. So which ever you find most intuitive.
2. Many on this forum (including myself) can provide such.
3. How will you steer without a rudder?
4. A 14m boat in a storm..should be in port and/or safe harbour!
5. If a cat, the wetdeck freeboard should be a minimum of 5% Lwl.
6. Many.. just search this forum.

More broadly.
For anyone to assist you, you need an SOR - a statement of requirements. So the designer, knows what they are 'aiming' at.
Otherwise you could get a box hull or a canoe hull and/or anything in between which may or may not be suitable for you.
Thus, define your parameters via the SOR.

 

Can you post your rough calculations of the cost of building the boat?

 

Thanks for your reply!!!

Ad1. I feel actually very comfortable with Solvespace, but never thought of it as something I could design a hull with. I'll think of it...
Ad2. Do you have like ready ones? And how much would you want for it? (and where are you from? ) Or can you recommend someone, or someones plans?
Ad3. As it is gonna be all electric solar powered (no sails or whatsoever) catamaran with electric motor on each of hull I can make one motor even pull and another push at the same time. The question is if that would provide enough maneuverability on 14x8m boat?
Ad4. Agree, but crossing Atlantic in a solar powered boat (I assume it is not gonna be a speed daemon) might end up in some rough conditions, thus my question

I did already requirements, some basic cad drawings and estimations based on that.

 

All electric, all aluminum, power catamaran, without anything close to fancy interior (woods, etc) - 150K USD
That is rough estimation, might be less, might be more.

 

@Daniel Mazurkiewicz I think that your estimate of US$ 150,000 is extremely optimistic.
While the cost of labour to build the boat in the Ukraine is probably much less than in Western Europe, you still have to buy the aluminium and the welding materials, not to mention the large battery bank and the electric motors.
Can you maybe post some copies of of your CAD drawings on here please?

Yes, having the engines so far apart will make the boat very manoeuverable - but you will still need to have rudders, unless you are proposing to use outboard motors (but I don't think that anybody yet makes electric outboard motors big enough for a 14 metre cat).
If you do not have rudders, and something happens to one engine, then you will not be able to steer the boat.

 

Software is the least relevant question here.
And "ocean crossing 14m cat from aluminum" is not really an SOR.

$150k sounds unrealistic for a custom built boat of that size. Add electric powertrain and it is not going to cut it. I also question how sensible choice solar is for ocean crossing. It is ok for many uses but for day in day out (nights too..) it is not simple or affordable choice.

Quickly checked price ranges of used 45ft cats. Seems to be $1 million new, $500k for 5 year old and $250k 25 year old. +-20%

So how will one make one, with an exotic powertrain, for $150k is beyond me.


Disclaimer: I am a farming game developer not a naval architect or ocean crossing specialist

 

I'm an electrical engineer, so nothing exotic from that side for me (and nothing extraordinarily expensive here). Did estimations for:
20kWh peak solar panels
2 x 10kW BLDC motors
60kWh batteries
~~ 40k USD

Don't need speed boat thus thought 2x10kW should be enough to run a boat efficiently, but if I'm wrong, will be happy to hear what is the minimum that I should consider

Then question of how much aluminum sheets will I need? I assumed 5000-6000kg, is that right?

And then all the rest...

 

Nothing fancy there, just couple of boxes that did let me quickly and roughly estimate how much aluminum I would need for desired dimmensions

 

I see your point. Thanks!

 

Build costs for all electric gonna run about 3-5k usd per foot

45' low end, very low end stuff, no work outsourced; cheap yard time maybe 3k

5k is more practical

 

Daniel, have you had a look at Bruce Roberts' webpage re his aluminium power catamaran designs?
https://www.bruceroberts.com/public/HTML/CATS.htm

Using the Cat400 as an example -
https://www.bruceroberts.com/public/HTML/descriptions/cat39_description.htm

They mention that the study plans cost US$95 and that
"Each STUDY PLAN contains ALL the construction drawings for each material - ALUMINUM & FIBERGLASS as applicable to the particular boat plan - with up to 25 sheets per plan!
Lists of materials - Technical information - Numerous construction drawings are all included."

It could be worthwhile investing $95 in a set of plans so that you can get a rough idea of what you will be up against re the design of your vessel.

Edit - for general reference, you could also have a look at the aluminium power (and sailing) cats built by GHI Yachts in South Korea.
https://www.ghiyachts.com/복제-products

But I will again agree with the others above, re how US$150,000 is only going to be a fraction of the cost to build your cat, and that 2 x 10 kw electric motors are not going to be enough power for it to operate effectively. What happens when you have to motor into a 20 knot (or more) head wind and a rough sea?
Your vessel is not going to be very seaworthy if it cannot do this, as you might have to motor off a lee shore in anger sometime.

 

I doubt you can find plans for generic hulls to put a superstructure on. Most you can do is buy plans for a similar sailing cat and adapt. I would suggest designing a rough superstructure/interior and making a detailed list of weights (primarily the propulsion unit, but also furniture, etc.), then hire a NA to transform your drawings into a boat.

2x10kW will probably be enough, there are similar size outboard powered sailing cats, altough most will be lighter. It all depends on your desired average speed, as long as 5kn is acceptable, you are good.
Battery size is marginal, 60kWh will barely bring you trough the night. Six hours of darkness means a max power of 10kW and no reserve. Unless you are willing to significantly go down with speed at night, upgrade to at least 80kWh.
20kWp of panels is ambitious with your budget. Covering the entire boat with standard panels will have disadvantages, better panels are more expensive. You should aim for a more realistic 12-15kWp. This also has implications on your daylight speed, since you need to recharge the battery.

Storms, you have two kinds of: the ones where you have searoom and the ones you don't. The first kind is simple, let out the drogues and run with the wind. The second ones are also simple, either you manage to get to safety with the available battery, or you wreck on a lee shore. You don't have the power or range to do much in a storm, for that you need a diesel (either an additional prop, or genset with additional electric motors). Morale, when in coastal waters follow the weather closely and always have a safe harbour in battery reach.

Needed Al weight depends. Thin skin is lighter but more difficult construction. Thick skin is easier to build but heavier. Waste ranges from 20-45%. But generally speaking yes, for an all Al boat (superstructure could be something else if you wish) you will have to buy around 5t (+/-1t) of it in different thicknesses.

 

2012 Custom Aluminum Catamaran sailboat for sale in Texas https://www.sailboatlistings.com/view/94066


For a build that size and your planned use, I would seriously consider using second hand Nissan Leaf power plants. They are affordable, compact, and powerful with an integrated gearbox and inverter, and there are experts out there offering stand alone control interfaces making them easy to adapt to builds like yours. They are a power plant you can grow into, and as batteries and solar get better, you can operate them at a higher voltage.

Regarding using forward and reverse independent thrust of each motor for steering, yes it can be done but as others have pointed out if you lose propulsion from one motor you won’t be able to steer or even keep a course without a rudder. I use this method on my catamaran and keep a rudder onboard that can be center mounted for steering in case of emergency.

Also keep in mind using the motor propulsion for steering is great for slow speed maneuverability, but is more inefficient at higher speeds and less responsive than a properly designed rudder.

On my boat, I tend to drop the throttle of one motor to allow the opposite to overtake in order to steer in a direction, rather than throttling one up to overtake the other.

Either way, your goal should be making the boat as efficient as possible, and a rudder system will allow the boat and its motors to maintain a more constant speed when maneuvering, wasting less energy.

 

Getting a friend with a FreeCAD since yesterday, i saw there are even FEM analysis available out of the box. Lets see what I can come up with over coming weekend.

5kn is not an issue for me, as long as it will let maintain safe speed/maneuverability in rough conditions. Plan to have onboard "emergency" power generator, wouldn't it solve the issue?

Was googling for superstructure in terms of boat design, you mention it second time here and I'm not sure if I get what it means exactly.


I find your advice and infos are very valuable, THANKS, will follow them! And before jumping to "deep water", will make sure that can afford what I would like to have