The future of maritime propulsion

[farmerben]

There is a lot of interest in making maritime propulsion green.  I've been looking at sailboats.  Most yachts have a sail area to displacement ratio of 10-20m2 per ton.  If you scale that up, it doesn't work for anything like a modern cargo ship.  There are some videos out there about Magnus effect sails and inflatable sails.  Nobody really breaks down the performance of these devices.  I suspect they motor sail all the time and get maybe an extra 1/2 a knot of speed boost under ideal conditions. The Magnus device is powered so it's really a question of air propellers vs underwater propellers.   I love sailboats, but they are mostly just expensive toys.  Back in ye old days sailing cargo ships were all we had, but they were terribly slow by modern standards.

The idea that you could use solar alone, also doesn't really scale.  I suspect methane and hydrogen to become prominent as maritime fuels before they make it into other transportation sectors.

[darthgently]

3 hours ago, farmerben said:

There is a lot of interest in making maritime propulsion green.  I've been looking at sailboats.  Most yachts have a sail area to displacement ratio of 10-20m2 per ton.  If you scale that up, it doesn't work for anything like a modern cargo ship.  There are some videos out there about Magnus effect sails and inflatable sails.  Nobody really breaks down the performance of these devices.  I suspect they motor sail all the time and get maybe an extra 1/2 a knot of speed boost under ideal conditions. The Magnus device is powered so it's really a question of air propellers vs underwater propellers.   I love sailboats, but they are mostly just expensive toys.  Back in ye old days sailing cargo ships were all we had, but they were terribly slow by modern standards.

The idea that you could use solar alone, also doesn't really scale.  I suspect methane and hydrogen to become prominent as maritime fuels before they make it into other transportation sectors.

Very slow cargo craft that could take advantage of wind, currents, and tides is worth exploring for loads that are consistent but not in a hurry but they would almost have to be mostly uncrewed and automated as labor costs are big deal the slower you go

[Hannu2]

Ammonia is seriosuly investigated as ship fuel.  It  can  be made from air and water with renewable energy and it does not produce any carbon dioxide because NH3 does not contain carbon. Ship Diesel engines can use ammonia with relatively minor modifications.

Negative things which need more development are toxicity, lower energy density than methane or diesel fuel and tendency to produce nitrogen oxides.

https://spectrum.ieee.org/why-the-shipping-industry-is-betting-big-on-ammonia

Edited October 7 by Hannu2
Typo error correction

[magnemoe]

Square cube law is sails enemy. Above 10.000 ton displacement it become very hard to use sail power only as the sail area become inpractical. 
Yes you have larger sailing ship but they tend to be Great Eastern or smaller modern cruise ships who often don't have to go far island hopping. And they are sail assisted, granted an cruise ship island hopping don't need much speed and they have an huge crew  
Going up to 50.000 ton and above and sails don't add much while crew count and fuel cost / ton carried goes down. 
This goes both ways, you can cross the pacific in an pretty small sailboat but an motor boat has to be more of an ship to do this. 

[kerbiloid]

Fresnel-lensed solar-powered steam/stirling engine.

[darthgently]

3 hours ago, Hannu2 said:

Ammonia is seriosuly investigated as ship fuel.  It  can  be made from air and water with renewable energy and it does not produce any carbon dioxide because NH3 does not contain carbon. Ship Diesel engines can use ammonia with relatively minor modifications.

Negative things which need more development are toxicity, lower energy density than methane or diesel fuel and tendency to produce nitrogen oxides.

https://spectrum.ieee.org/why-the-shipping-industry-is-betting-big-on-ammonia

I just had a flashback to the movie The Mosquito Coast wherein Harrison Ford’s character inadvertently poisons a big stretch of a tropical river when his ammonia based ice factory gets riddled with local thug bullets.  Hope that wasn’t a spoiler given the movie is decades old

51 minutes ago, kerbiloid said:

Fresnel-lensed solar-powered steam/stirling engine.

Very steampunk 

[DDE]

Hey, have the new ecological requirements for residual fuel oil been put in effect, or has COVID given everyone the excuse to flunk them?

Last I checked, it seemed to veer towards the latter. Can't start greening the industry that still relies primarily on muck from the bottom of the refinery crackers.

[kerbiloid]

Soap.

Have a barrel of it onboard.

Spoiler

 

 

Btw, about the solar Fresnel.

Spoiler

https://www.youtube.com/watch?v=CDCTANU8Tfk

 

 

 

[farmerben]

3 hours ago, kerbiloid said:

Soap.

Have a barrel of it onboard.

  Reveal hidden contents

 

 

Btw, about the solar Fresnel.

  Reveal hidden contents

https://www.youtube.com/watch?v=CDCTANU8Tfk

 

 

 

Bad for reefs.

 

How much horsepower does that thing have?

[darthgently]

5 hours ago, kerbiloid said:

Soap

Yes, this would have the opposite effect as oil.  Sailors of yore would dump oil during storms to drastically reduce spray and wave height in their vicinity.  Surface tension is a silent hero.  Soap would have the opposite effect and all this has an effect on skin friction.

 But both soap and oil are obviously drastic measures and not great ideas as a common practice

[darthgently]

Related:  so much energy is lost to wave making in displacement craft. How to make use of that energy?

 

[AckSed]

Today I learned "wake thieving" with specialised hydrofoil boards was a thing.

[farmerben]

https://proafile.com/multihull-boats/article/the-camel-a-sailing-cargo-proa

Quote

On a proa, cargo may be loaded entirely into the leeward hull, which is also the center of buoyancy. There will be very little change in righting moment no matter how heavily laden the proa might be. With a proa, righting moment is handled by the weighted ama and outrigger structure to windward, not buoyancy to leeward. The righting moment remains consistent, meaning stress, scantlings and sail area will also remain consistent between laden and unladen. This leads to a well-engineered and efficient structure through a widely varying displacement.

 

[darthgently]

1 hour ago, farmerben said:

https://proafile.com/multihull-boats/article/the-camel-a-sailing-cargo-proa

 

There is a lot to be said for reducing wetted surface area by way of multihull designs (riding highr in the water and not relying on low down under the waterline ballast for righting), but they get less persuasive as payload goes up.

[farmerben]

And a pacific proa gives you the longest boat for the mass.  The hull speed of a boat is determined by the square root of its length.

In the Marshall Islands they are very popular but typically rather small.  The biggest ships the Hawaiians traditionally used seem to have been catamarans.

 

Edited October 8 by farmerben

[darthgently]

22 minutes ago, farmerben said:

And a pacific proa gives you the longest boat for the mass.  The hull speed of a boat is determined by the square root of its length.

In the Marshall Islands they are very popular but typically rather small.  The biggest ships the Hawaiians traditionally used seem to have been catamarans.

 

I had a half baked storyline for an alternate history wherein Fletcher Christian with his crew and Polynesian wives, plus more Pacific Islanders in a loose alliance after the mutiny, end up building a small fleet of battle catamarans that are much faster than the British Navy and armed with captured cannon and swivel guns over time.  They end up pushing the British mostly out of the Pacific but then have to face the Dutch, Spanish, and Portuguese.  By this time all the navies have added faster catamaran “frigates” because that is how arms races work.  Because I’m a dreamer, not a disciplined writer that is as far as it got

[farmerben]

https://en.wikipedia.org/wiki/Kamehameha_I

King Kamehameha built ships matching your description around 1790.

[darthgently]

34 minutes ago, farmerben said:

https://en.wikipedia.org/wiki/Kamehameha_I

King Kamehameha built ships matching your description around 1790.

The only reference I see to water craft at that link are canoes.  Which were likely, at most, largish proa, maybe a few “chief” or royal catamarans, but cannon were extremely heavy and the cannonballs and powder just added more weight.  I could see the traditional craft bearing a few swivel guns perhaps but very hard to imagine typical ships cannons mounted on historical Polynesian craft.  In my fiction,  they learned techniques to build larger hulls from Fletcher Christian and his crew but adapted to multihull rather than monohull displacement.

Any way, to come back on topic, multihull nonballasted ships that could carry what a  modern container ship carries would be a big engineering and materials challenge.  It would be great to know the limits

Edited October 8 by darthgently

[farmerben]

 

 

Edited October 8 by farmerben

[darthgently]

11 minutes ago, farmerben said:

 

 

Those are the “chief” or royal catamarans I was referring to.  Small swivel guns maybe.  Typical ships cannon of the era?  Nope.  But if scaled up beyond the size of large hollow logs via euro shipwright techniques maybe.

 Imagine ships of European construction technique, catamaran hulls, with topsides 1.5 to 2 storeys high at least, and 30 meters long.  If you want to keep that wetted surface low (so keeping the craft floating high in the water) while shipping multiple cannon and ammunition it is going to have to be big.  And there you run into the issues you brought up earlier with scaling up sailing rigs.  In my fiction the figured out a Marconi like cutter sooner to help a bit

That is indeed a swivel gun in bow of the catamaran on the left, btw

[magnemoe]

49 minutes ago, darthgently said:

I had a half baked storyline for an alternate history wherein Fletcher Christian with his crew and Polynesian wives, plus more Pacific Islanders in a loose alliance after the mutiny, end up building a small fleet of battle catamarans that are much faster than the British Navy and armed with captured cannon and swivel guns over time.  They end up pushing the British mostly out of the Pacific but then have to face the Dutch, Spanish, and Portuguese.  By this time all the navies have added faster catamaran “frigates” because that is how arms races work.  Because I’m a dreamer, not a disciplined writer that is as far as it got

Think wooden catamarans has an structural size limit well below frigate as in two half sized bolted together but idea is fun. also no idea how two sets of masts and sails would handle.  Talking about ships with an lower deck for storage, a gun deck and upper deck, perhaps an poop deck at the rear so putting the mast in center would not work unless you go for an trimaran there the outriggers is just gun deck with balsa below. 
Have fun sinking that  

My only experience with catamarans is two canoes connected to two branch and tied together. 
Its was some very unstable homemade canoes on an trip for young teens by the church.  
Or dear god don't let us roll over again theory for finding god, offset by all the swearing then it happened  
The catamarans was obviously very stable and we even rigged makeshift sails on lakes at the end I think most of the canoes with seats was catamarans, I assume sitting on seats not the bottom added to the unstably as it raised the center of mass but the seats was also that we used to tie the branches to

[darthgently]

The swivel gun would be good at close range against personnel on other ships but really wouldn’t damage a ship

Edited October 8 by darthgently

[magnemoe]

8 minutes ago, darthgently said:

The swivel gun would be good at close range against personnel on other ships but really wouldn’t damage a ship

My thought to and you are shooting up. I assume the railing on warships at the time was timber not planks to stop shotgun charges from the enemy main guns shooting up be effective. 
Same for pirates who tend to use ships as above, having an frigate made you powerful. 
 

[darthgently]

7 minutes ago, magnemoe said:

My thought to and you are shooting up. I assume the railing on warships at the time was timber not planks to stop shotgun charges from the enemy main guns shooting up be effective. 
Same for pirates who tend to use ships as above, having an frigate made you powerful. 
 

That’s right. Swivels full of of scraps and nails were used against sails but mostly they were loaded like big shotguns full of lead marble sized shot against groups of armed sailors.  Devastating on sailors at close range.  They could fire single larger balls like a cannon in attempts to take out spars and such but they were mostly boarding and anti-boarding big shotguns 

What you mention about shooting upward reminds me that swivels could often shoot at a much higher angle 

[AckSed]

To drag the topic back in line, here's a Scottish lake fisherman who converted his little boat to run on solar and batteries:

tl;dw The conversion was not that difficult, it has about the same capacity as a middle-of-the-road Nissan Leaf, and he doesn't go many miles, so many days in the summer he doesn't need to charge. It was the paperwork and regulation he had to deal with that was really challenging.

If you think about it, coastal fishing boats like this are good candidates for electrification.