Looking for a long range expedition aluminum power catamaran design

[Silvard]

Have you given consideration to a second hand sailing catamaran? There are so many for sale nowadays, of all shapes, sizes and prices.
Alaska to Ushuaia in a motor boat is going to cost a lot in diesel, even if the boat is fairly efficient re miles per gallon.

We have, but neither of us is too enthused with the idea of traditional sailing despite its obvious benefits for our use case. We are also not confident it can accommodate our toys. We also have considered adding a kite sail to this design though as it adds more autonomy, but we haven't yet priced it out (there seem to be only 2 vendors for this).

The idea isn't to go from Alaska to Ushuaia in one go. But rather slowly make our way around while getting to know many places. We acknowledge the diesel costs and we're ready to budget for it, it's not that dissimilar from constant international air travel. We just want to be "efficient" about it (as efficient as one can puport to be in the endless money pit that is operating a boat).

 

[philSweet]

I think there is a big disconnect here between what you want and what your price range is. I don't see a catamaran working for you. Half a million gets a decent second or third hand 45'er in aluminum.

Garcia Exploration 45 – Arctic Monkey https://swiftsureyachts.com/garcia-exploration-45-arctic-monkey/

The support for a gyrocopter would probably add half a million to the same yacht w/o one.

50' fiberglass catamarans that weren't anything special were running 2-3 million 20 years ago once you had some cruising kit added on - and then they were 15,000 pounds over their brochure weight.

I suggest you pick up something like the Garcia and get used to it. It's really about all the boat two people can handle, and you would want at least four for passage making - at least your insurance company will want you to have at least four.

 

[Silvard]

This is probably so, but can you please break down for me the actual costs of involved? I'm not trying to be a contrarian, I know I'm out of my element when it comes to ship design, building and budgeting, but I want to understand. I know everything is a compromise but I was hoping to see some more specifics on what it actually takes (especifically hull and basic/essential fitment). If we need to adjust our budget or our goals then we do that, but we're not yet at the stage where we jettison the whole idea and settle for an alternative.

As for the gyrocopter, I'm not talking about a helipad, just in case, just a surface/deck that's at least 18ft long to place it on. The gyrocopter operates on the water. And at most it weighs 800 lbs unoccupied with a full tank. Would that really cost 500k on its own? If so, why?

 

[comfisherman]

I've not purchased large quantity of marine aluminum since 2019, but it's a number that could be found. I'd guess it's somewhere near the 4$ mark per pound in bulk. Last time we had a boat nested it was close to if not a hair over 20% wastage. Having it machine cut wasn't bad per pound (was in the upper 20 cents a pound at the time I'd guess near double that now, not trivial when your talking 60 to 70 foot boats.)

Couple hundred grand and it still needs to be welded together, hard to guess exact prices on labor as it's changed so much in the last few years. Old adage for commercial boats (spartan and plain commercial fishing boats) was same in labor as plate... guessing that's changed wildly in the last few years.

Before your dropping engines in its gotta be half a mil on the small optimistic plane side....

9 liter main is 55-65k each, 12-13 are 75-110. Gears, exhaust, couplings and shafting could easily put you 200k in just on basic driveline.

Heck on a boat that big windows and a couple doors hit 25k easy, never mind hatches hinges and railing work.

Doesn't take long for the ticker to rack up.

 

[Silvard]

Gotcha, thanks, that is actually helpful. We haven't bothered getting a quote from a shipyard because we figured it would be pointless to do so without a design, which is why I'm here in the first place. We've only priced out systems and equipment that for the most part don't change that much with the size of the boat, and to our layman math so far it seems quite reasonable, which is why it's confusing when people dismiss the idea with examples of luxury finish yachts that are obviously a whole different type of target.

Right now our main concern is the design and the actual structural work (including fitting things like propulsion, thrusters, generators, etc. which we have also priced out). That is the current scope. We have priced out the systems and equipment and we are comfortable with the idea of doing the installations ourselves wherever possible. We also feel comfortable with the idea of finishing the boat with our chosen utilitarian interiors ourselves as well.

For the work that we do want to hire and materials we have 0 intention of doing it in high cost of living areas like the US. We will go to east Asia or South/Central America, though this is something where we'd also appreciate the guidance and network of a savvy designer/NA.

From this thread:
Looking for Help with Our Aluminum Catamaran Build Plan https://www.boatdesign.net/threads/looking-for-help-with-our-aluminum-catamaran-build-plan.69893/

I see some people have undergone a similar journey, although that boat is obviously considerably smaller. However it still seems quite reasonable, so it seems to pull in a different direction than the observations made on this thread. What are they (and us) missing?

 

[fallguy]

I read the thread. I think the SOR needs refinement because you have too many conflicting requirements.

Fuel efficient ~ military grade

Fast ~ fuel efficient

Light ~ loaded with solar

Range ~ not stated with specificity

Mini sub launching ain’t coming in under your 1m pricetag. You need a massive crane and open decks which you said you did not want.

What flag you plan to fly? Think resale for build location, etc.

Anyway, my suggestion would be to pay a consultant to help tweak the SOR, cause one person here alluded to this problem and he is a true expert.

 

[fallguy]

A nice 20M power catamaran was sold last decade for about 400k. 4000nm range, great boat.

I think you hire a NA first to help define the SoR and help you set reasonable expectations.

 

[Silvard]

I read the thread. I think the SOR needs refinement because you have too many conflicting requirements.

Fuel efficient ~ military grade

Fast ~ fuel efficient

Light ~ loaded with solar

Range ~ not stated with specificity

Mini sub launching ain’t coming in under your 1m pricetag. You need a massive crane and open decks which you said you did not want.

What flag you plan to fly? Think resale for build location, etc.

Anyway, my suggestion would be to pay a consultant to help tweak the SOR, cause one person here alluded to this problem and he is a true expert.

I believe the military grade thing is a bit of self inflicted red herring. This has been taken to mean armored or combat capable I guess, when I just meant to imply utilitarian finish as opposed to luxury.

I haven't specified fast as a goal, or at least not particularly fast, just hull speed for top speed and fuel efficient cruising at 8 knots.

As light as possible for a full displacement catamaran? I don't believe I've stated lightness as a primary goal either, just as a vector for full efficiency.

I'm not sure how I can specify range. Ideally we would want 4,000 to 5,000 nautical miles, but there are many levers one can pull to achieve this. I am not qualified to optimize for this goal. That is why I initially avoided giving hard numbers and why I'm here asking for help.

Above I mentioned needed an open deck for the gyrocopter anyway I was talking about multiple lounging decks as seen luxury yachts. but I don't see why a mini sub can't be launched from a deck with overhang. I've done it from a scrappy trawler with a small Liftmoore 3200 and with minimal clearance, it's one of those Sports mini subs. Hopefully I'd be able to for something more sophisticated in the future but just based on specs it doesn't seem that farfetched anyway.

I am obviously not a boat designer or naval architect, nor do I have an extensive network of them. If the next step is to just directly contact a professional then that is great, that is what I meant by pointing me in the right direction. I was hoping to be guided towards a design or a NA suitable for the SOR I posted, flawed as it is. I suppose I'll just go through the links posted on the thread I referenced previously.

 

[fallguy]

Well, I can tell you one thing. Your reply to me is healthy. Lotsa people post here with awfully big egos that bruise from a whisper.

The SOR also requires an operating budget for power cat. I think Domino logged 60,000 miles and at 2mpg; it cost 30,000 gallons fuel and at $5, that is 150k fuel or 25k annual at say 10,000nm or more for more travel.

Or will you sail free on the winds?

 

[Silvard]

Well, I can tell you one thing. Your reply to me is healthy. Lotsa people post here with awfully big egos that bruise from a whisper.

The SOR also requires an operating budget for power cat. I think Domino logged 60,000 miles and at 2mpg; it cost 30,000 gallons fuel and at $5, that is 150k fuel or 25k annual at say 10,000nm or more for more travel.

Or will you sail free on the winds?

Unfortunately neither of us caught the sailing bug. Fortunately we can budget for these costs (yearly air travel and hotel expenses alone take care of it), especially given that we're in no rush to circumnavigate and we can spread out these costs over time. We are curious about using a kite sail to be able to take advantage of wind propulsion for long passages, but we haven't gotten a quote for that. For all we know that's worth a couple of years of fuel by itself.

The range we want is to be able to do ocean crossings safely and reliably, but we don't expect them to be a common occurrence. We'd still like as much fuel efficiency as we can eke out, of course.

 

[comfisherman]

We still get a few circumnavigators although the numbers coming north is down. Seems like it's 8 or 10 to one sail vs power although of the sailors a few do as much motoring as a power boat. Sails wear, was a big shocked at the cost of modern high performance sails.... made modern diesels seem downright reasonable.

All just trade offs.

You mentioned power packages, did you have a ballpark size and weight you used for a benchmark for a power package?

 

[Silvard]

We still get a few circumnavigators although the numbers coming north is down. Seems like it's 8 or 10 to one sail vs power although of the sailors a few do as much motoring as a power boat. Sails wear, was a big shocked at the cost of modern high performance sails.... made modern diesels seem downright reasonable.

All just trade offs.

You mentioned power packages, did you have a ballpark size and weight you used for a benchmark for a power package?

Yeah, I've read quite a bit on the subject because instinctively I questioned the viability of motoring vs sails for long distance cruising (for recreational purposes) and I was surprised at all the literature I found that showed how the operating costs of both converge closer than you'd expect over a long enough period of time when taking into account new sails and rigging and time you end up needing motor propulsion anyway.

As for power packages I once again inisist I don't know what I'm doing, but we went by twin diesels from 150 to 250 HP as well as the equivalent in electric motors for both a serial hybrid and a parallel hybrid set up. It was a guesstimate based on formulas like these:

"To be fuel efficient you will need to travel at a speed length ratio (SL) of around .8 to .9. It is my understanding that this is the SL that ocean going freighters are designed to. The square root of the LWL equals a SL of 1. At a SL of .85 you need 1 hp per 1000 lbs of displacement. At what is often referred to as hull speed a SL of 1.34 requires 1 hp per 500 lbs of displacement. It takes approximately .055 gallons of diesel per hour to generate 1 hp. Playing with these numbers you can settle in on how big of a boat, engine size and fuel capacity to meet your SOR."

Among other corroborating sources, and trying to be conservative.

 

[skaraborgcraft]

€695,000 Long-Range LIVE ABOARD Explorer Yacht For Sale | M/Y 'Britt'

THIS Is Hull 1 €585K STEEL Trawler Yacht With A 5,000 NM Range!

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€495K Long-Range Custom Steel Converted Trawler Yacht

My Favourite Features On This ONE OFF Steel Long Range Liveaboard Trawler Yacht! - YouTube

My experience in the superyacht world will say the aircraft side of things is the the least used, while being the most expensive, even if its a "simple" gyro.

 

[skaraborgcraft]

81′ Ellemaid – George Buehler Yacht Design

Driives apparently at SL 1.0 with only 24hp, giving over 11,000nm range on a 1,000 gallons. (calm water predictions)

 

[Silvard]

€695,000 Long-Range LIVE ABOARD Explorer Yacht For Sale | M/Y 'Britt'

THIS Is Hull 1 €585K STEEL Trawler Yacht With A 5,000 NM Range!

Calling ALL Steel Hulled Long Range TrawlerYacht Fans! This One Is For You!

€495K Long-Range Custom Steel Converted Trawler Yacht

My Favourite Features On This ONE OFF Steel Long Range Liveaboard Trawler Yacht! - YouTube

My experience in the superyacht world will say the aircraft side of things is the the least used, while being the most expensive, even if its a "simple" gyro.

Thank a lot for those links, those are some interesting boats with some inspiring functionality, even if they're not exactly what we are looking for.

I understand that in the context of superyachts a helipad is quite the complication but that's not really what I'm talking about. How is a gyrocopter any different than storing a non-inflatable tender or any toy with similar dimensions and weight on an open deck with rotor clearance (only in terms of height)? They're not started on the boat, they're deployed to the water on floats where they take off and land on the water, not the boat. It's been brought up as this massive expense or complication and I'm failing to see why, what am I missing?