Comment by Gwypaas | Hacker News Reader

Comment by Gwypaas | Hacker News Reader

I would be cautious about the twisting loads on containers. The side forces will be huge, especially in a swell. Then add mechanical parts that must work in an incredibly hostile environment, and lastly, add on the north Atlantic in the winter, and you are in for a bad time. Ships losing containers due to stacks collapsing happens very frequently, without any extra forces.

https://alsum.co/wp-content/uploads/2021/04/Perdida-de-conte...

Look at a purpose-built sailship from the age of sail in a north Atlantic storm. It is a rough ride.

https://www.youtube.com/watch?v=Y7RABaByP_8

Another attempt in a similar fashion is the Oceanbird concept by Wallenius Wilhelmsen, but that means building the vessel from the ground to handle the forces and that over-head loading and unloading is not possible, thus the aim at RO-RO ships.

https://www.theoceanbird.com/

With one vessel already ordered:

https://www.walleniuswilhelmsen.com/news-and-insights/highli...

Personally, as a commercial sailor and software engineer, this container approach screams of VCs throwing money at commercial shipping without understanding the industry. Profit margins are non-existent and are already hugely optimized with possibilities for specialized solutions. This wing sail will have to compete with synthetic fuels without increasing the cost due to crewing requirements.

Yep, supporting the moment from the wing via containers is the biggest structural concern. The containers are strong enough in most sea states, with reefing/feathering required in heavier winds and seas. We will stow the sail long before it encounters conditions like the ones shown in your video.

Oceanbird is awesome! The trouble is that overhauling the entire industry with new-built ships would take too long to make a meaningful climate impact, and be extremely expensive (not to mention that their approach only works for ro-ros).

Synthetic fuels will compete with aviation for the green hydrogen supply (needed to make methanol/ammonia/green hydrocarbons) and are expected to cost 2-3x what current fuels cost. This net makes our fuel cost savings case even stronger.

Industry insiders generally already know that there's really no good cost-saving decarbonization solution, and that decarbonizing fast is a hair-on-fire problem for owner/operators. The barriers standing in the way of most wind-assist devices are: poor ROI, shipyard availability for retrofits, risk to shipwoner (capital upfront), and that they don't package on containerships. We solve all these problems by using a large, efficient wing and depending on the container load path. There are technical problems to solve, but the fundamental physics works.

What is the order of magnitude of the wind load generated on one single wing?

10s of Kn . It's <10% the wingloading of a 747.

Every "I'm going to start with a shipping container" solution eventually runs into the same problem: shipping containers are effectively empty soda cans. They are only strong when loaded exactly as expected.

Have you actually talked to anyone in the cargo ship industry about your idea?

Ultimately they don't need to use an actual standard shipping container but just a container that's the same shape on the outside.

It's not their container that's the issue. It's the containers below it.

Is the sail-container sufficiently heavy to stay in place, or does it need pull on something that's holding it down?

If the sail is pulling, the container below would see a remaining uneven load from above. Is there a limit to this? Loading/unloading an unbalaned container sounds like a problem, but is it, while sitting on the ship?

To me the problem is transmitting the force generated by the sails to the body of the vessel

A small to medium vessel fully loaded is like 150.000 tons. 10% of that is 15000 tons, imagine the force that needs to be transferred to the structure of the ship in a place where it was not designed to handle that force.

Mass of the ship would matter if it was supposed to hover. Trying to google for engine thrust I found numbers that might be in the order of magnitude of 500kN (hp translated to pounds at certain speed). 10% of that through the kite 500kN. That would be enough to lift 50t, which is at the order of magnitude of the maximum mass of a shipping container. Looks like it might work.

The mass is actually 50.000 tons, I typed wrong. My point is not the force to move the mass of the ship, but transmitting that force to the structure of the vessel in order to move it forward. It’s a lot of force, the structure is not made for that

> Have you actually talked to anyone in the cargo ship industry about your idea?

I worked in the container shipping industry. It doesn't sound like this person ever talked to anyone in the industry. It's not like "add a sail" hasn't been thought off loads of times before. I've seen a few times where people spend 6 months to run a project where they never talked to a person with experience. Then that project would eventually fail. Circumstances and restrictions sometimes change over time, so trying to solve the same thing every few years is a good thing. But "sail in a container", ehh..

"soda cans" is very pessimistic. The structural integrity of containers is very high. Specially the end walls.

The typical problem with containers is non-standard or unsecured cargo pressing against the side walls, which are indeed very weak.

Nonsense. Drinks cans are strong when filled because they are pressurised. Containers aren't pressurised. Their contents have no effect on their strength.

That is why I explicitly said an empty soda can.

>> Oceanbird is awesome! The trouble is that overhauling the entire industry with new-built ships would take too long to make a meaningful climate impact, and be extremely expensive (not to mention that their approach only works for ro-ros).

Shipping is responsible for like 2% of emissions. A 5-10-20% reduction on a small number of vessels for a small number of voyages is not gonna make a dent.

This is clearly intended to supplement, not replace, the ship's existing power source.

You would fold these down rather than trying to ride out a swell with them up. They go out of they way to clarify how easily these can be furled and unfurled.

Im no engineer but this is what i thought too. Just automatically fold the sails when gusts reach above a certain threshold. Shouldn't be too hard, right?

This may be more challenging than you think; depending on how you 'fold' the sails, you may end up with enough 'windage' 'aloft' to over-stress the connections anyway. They'll likely be forced to bring the wing down completely, which will either make the wings small or expensive.

I believe the design is to roll them up like a measuring tape.

Everyone's forgetting that this is just like a jetliner wing. Huge forces, harsh environments, long lifespan... this is how commercial airplanes are designed, and one of the founders is a professional aerospace engineer who worked at Tesla.

> professional aerospace engineer who worked at Tesla.

Being fair, this is really broad and doesn't mean much at all.

> Everyone's forgetting that this is just like a jetliner wing.

Just like a jetliner wing that can be folded up. On the plus side, jetliners regularly hit speeds relative to the air that are ten times as fast

Well, you don't have to run it in those conditions.

Most of the popular shipping lanes traverse hostile conditions for at least one season of the year.

It's never gonna work for a multitude of reasons like you said. Usually I'm not pessimistic but this really seems like: we have an idea, make a video, post it on a site, ask questions later.

It probably won't succeed, because most startups don't succeed.

It won't succeed because of physics/math.

They claim a save of 400kW per sail, with a boat cruising at 22kts. Let's do some math:

- 400kW is 400e6 J/s, or 400e6 N.m/s

- 22kts is 11.31m/s

So the forward force must be 400e6/11.31 = 3.5e7N, so around 3500 metric tons of force for a single sail. And with a relative wind coming from the front usually, this means the side force will be much bigger than that.

I am calling this BS

Exactly my point. Not to mention transferring that load to the body of the vessel, which has a structure made to withstand loads in specific points. A container stacked on top of other containers for sure isn’t able to sustain such forces lol not even if it’s well latched. It’s just too much force. Also the ship is hollow, there are like 5 rows of containers below deck, so the deck itself is not very strong except for some points that have the mechanism for the ropes.

Agreed on all counts. "Mirage" is the perfect name for this product.

I'm sure it's implied the container itself will be fixed to the hull to meet those requirements

It’s really not: look at the first video on https://www.outsailshipping.com/

That video shows that they have no clue about containers or the container shipping industry.

Reply on news.ycombinator.com