The roller ship was not an effective way to cross the high seas

https://hackaday.com/2024/03/27/the-roller-ship-was-not-an-effective-way-to-cross-the-high-seas/

by Stratoscope • 2 years ago

109 30 2 years ago

hackaday.com

helsinkiandrew• 2 years ago

Reminded me of the 19th century Russian circular ironclads:

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

0823498723498722• 2 years ago

If someone does a steampunk version of Star Wars, that'd be the Falcon design.

mojomark• 2 years ago

"The general hope was that the roller ship would slash travel times by virtue of its low-drag design. Sadly, an attempt to cross the English Channel in 1897 revealed that the roller design had one unforeseen drawback. In the water, the rollers tended to drag a great deal of water up with them as they rotated."

Super fun. I'm a marine engineer and design vessels. I've seen a lot of whacky designs over the years and never encountered this one!

Apparently, from the above quote, the culprit for increased drag was skin friction (in this case, that meant water clinging to the surface of the rollers and being lifted out of the water - kind of like the reverse effect of a Tesla turbine which exploits skin friction between moving air and a stack of rigid discs on a rotor). That would certainly cause propulsive inefficiencies.

However, from my view, the primary source of drag here are the "hollows" between the rotor discs. If you were to look at a plan (top) view of the vessel as it moves through the water you would find significant water pressure gradients between (at the aft and fore end of) each wheel. When you have multiple wheels in series, you have oscilating high and low pressure zones along the length of the waterline. That's a tremendous amount of energy lost to water turbulance.

When you look plan views of hydrodynamic hullforms at the waterline (whether monohull, or multihulls like catamaran/trimarin/SWATH) or even aircraft foil shapes, you don't see "wavy" form lines for this very reason.

I will say that these inventers were encroaching on the SWATH hull shape. The author states that this roller disc hull would not be stable due to the high CG. However, SWATH hulls are known for their stability in high sea states.

LorenPechtel2• 2 years ago

So many things are obvious once pointed out. I never would have thought of pressure gradients but once you did it's obviously a very uneven surface and you don't do that in anything contending with a lot of drag.

How do you see this as a SWATH? This is a catamaran that combines buoyancy and propulsion. I do agree it has a high center of gravity, but that's a relative term--what counts is the ratio of height to width. And a catamaran or SWATH has a much wider base than a typical ship.

Wikipedia says SWATH ships require complex control systems--why? Yes, they're very load sensitive because the small contact at the surface means a lot of vertical movement to compensate for weight changes, but couldn't that simply be handled with some pumps and tanks? Make the ship always weigh X--take on water or pump it out as needed to maintain that X.

usrusr3• 2 years ago

I'm not a marine anything, but I'd assume that the control system Wikipedia mentions are ballast tanks that need to reflect any change in load, load distribution and even wind load I'd guess. Sinking a little deeper won't do much to compensate increased load because the small surface area means little change in displacement per change in vertical position. Active trimming pumps.

Someone• 2 years ago

I don’t understand why they would think this to have low drag.

- Displaced volume wouldn’t be lower than that of a traditional ship (likely even quite a bit higher because the wheels would add mass and the hull would have to be stronger than one that rests on the water)

- Surface area would be higher than that of a single hull.

Also, looking at this as a variant on the paddle steamer (https://en.wikipedia.org/wiki/Paddle_steamer#Seagoing_paddle...), didn’t we already know in 1897 that screw propellers are a lot more efficient? SS Archimedes (https://en.wikipedia.org/wiki/SS_Archimedes) was built in 1839.

So, what was the thinking? It being easier to have low rpm in steam driven engines, and that compensating for those disadvantages?

eternauta3k• 2 years ago

Part of the drag scales with the relative velocity between the surface of the wheel and the water. If they move with ~0 relative speed, drag is reduced.

bluGill• 2 years ago

Paddels can he just as efficent as screws but only with mechanical comylexity which makes them unreliable.

s1artibartfast2• 2 years ago

Wheels add mass and cross sectional drag to my car, but rolling more than makes us for it.

I assume the thought was similar.

Some of the energy is lost to friction, some is lost to the motion of water.

Imagine a ship where the hull sufface has the same relative velocity as the water. It would behave the same as a frictionless ship.

usrusr3• 2 years ago

Isn't it rather obvious that they thought friction was the main (or the sole!) component of drag? If displacement waves didn't exist, or did not cause meaningful drag, floaty wheels might even have taken over already in the age of sail.

lttlrck• 2 years ago

Ignoring why they didn't intuit that it would not work, I don't understand why the models didn't demonstrate it.

0823498723498722• 2 years ago

For the high seas I had thought a design criterion was self-righting; is that only true for smaller vessels?

s1artibartfast2• 2 years ago

I don't even think it is true for small vessels. Catamarans and outriggers are absolutely not self righting.

adonovan• 2 years ago

the culprit for increased drag was skin friction

You raise the question of whether Teflon-coated rotors might have improved the efficiency... but isn't the skin friction also the source of propulsion? Would eliminating the tendency to "drag a great deal of water up" also eliminate the tendency to make headway?

rokkitmensch2• 2 years ago

Devil's bargain. The friction losses you save in dragging water up are more than compensated for by the loss in propulsive efficiency.

cpeterso• 2 years ago

“In 2016 a Florida man attempted to run from Boca Raton, FL to Bermuda in a home-made, inflatable plastic bubble. Reza Baluchi had been warned by the Coast Guard that any efforts to attempt his journey would be futile and result in severe legal and financial retribution. However, Reza’s convictions and ambition left him undeterred by such threats - he’d been waiting his whole life to do this and nothing was going to stop him. This is the story of that fateful journey as told by the man who attempted it.”

https://youtu.be/da6_LjiIzXk

ricardobeat• 2 years ago

That video is so frustrating. The coast guard complains the “rescue” cost $144k, but nobody called for it, and then they sink $120k of private equipment for no good reason. What a waste of resources. No difference from people who cross the atlantic alone in a kayak but they don’t get forcibly rescued.

rokkitmensch2• 2 years ago

Typical USG "because we can, and nobody can stop us, therefore we're correct".

senkora• 2 years ago

It seems to me like, if he were to have tried to do the voyage accompanied by a dedicated support boat, then the Coast Guard probably would have let him do it.

On his first trip, the Coast Guard intercepted him, but eventually let him continue, but then a few days later he had to be rescued.

On his second trip, they were much less lenient and forcibly removed him from the bubble.

So it sounds to me like the Coast Guard didn’t think he had planned well enough to do what he was trying to do safely, and they were probably right.

If he had instead done a series of progressively longer trips accompanied by a support ship ready to rescue him, and then planned to do the trip to Bermuda with a support ship, then he may have been able to convince the Coast Guard to authorize him to do the voyage.

Animats• 2 years ago

"Damnation Alley" (1977) had the "Landmaster" [1], a large ATV with a roller ship mode. But that was an amphibious vehicle with some river crossing capability, not a ship.

There are amphibious monster trucks. Here's a Russian one.[2] No props, just ridged tires. They're not great watercraft, but if you are crossing frozen ground and break through the ice over a lake, they can grind across the water and up onto hard ground.

[1] https://youtu.be/26n3RsXNyKE?t=392

[2] https://www.youtube.com/watch?v=3j7n00Xx38o&t=104s

ChrisMarshallNY• 2 years ago

Argh. I just got PTSD from that reference.

Damnation Alley was Plan 9 From Outer Space-level bad.

bryanlarsen• 2 years ago

SHERP is a Ukrainian brand that used to have production facilities in Russia.

user32489318• 2 years ago

Did research on this company quite a while ago, so this may not be fully accurate now. Back then, it was a Saint Petersburg based. In my opinion, most likely state subsidized. On its own SHERP, is just a commercial substitute for homemade vehicles popular in the Northern Russia going back to ‘60s. The company model hinges on a patent of one or more critical components (wheels, drivetrain,..). That model failed for its predecessors, see link below.

It is hard to google, but there a bunch of research papers and open source designs (from 80s, 90s) for all kinds of wacky 3, 4, 6-wheelers. The last patents related to these expired in early 00. Newer patents are all from the SHERP guys.

The older patents are from a bunch of other companies that failed before Sherp. For instance, one below was made by SMZ in ‘94, (sub)contractor for the military that produces parts for nuclear submarines and what not. https://pnevmohod.ru/forum/index.php?topic=3956.2180 (Now nicknamed Elon’s cyber truck)

pfdietz• 2 years ago

Drachinifel on these:

https://www.youtube.com/watch?v=qNLf0yt0IHo&t=1559s

jbm• 2 years ago

Rather than turning quickly, the rollers labored and the craft could barely break a dozen miles an hour according to a contemporary account. Even for the late 19th century, that was slow

This reminds me of a lot of my failed efforts to refactor code.

yalue• 2 years ago

Heh, so it's an 1897 version of what this guy on youtube attempted with a monster truck with mild success: https://www.youtube.com/watch?v=ohxGA7fpfu0 (warning: extremely redneck)

cratermoon• 2 years ago

Oh, so the self-driving car of the late 19th century

RecycledEle• 2 years ago

I know the texture of the wheels on a roller ship (or the hull on a traditional ship) determines its drag coefficient.

Are there materials that let us change that on the fly? For example, can we apply a magnet to the back of some material to change its surface to increase or decrease its coefficient of drag?

The roller ship was not an effective way to cross the high seas

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