from Hacker News

Wavy walls use fewer bricks than a straight wall (2020)

by caiobegotti on 7/27/23, 1:16 PM with 264 comments

  • by nonethewiser on 7/27/23, 2:10 PM

    I see this a lot in the rural US with wooden fences but had no idea why it was done, but I guess its for the same reason (stability). Apparently they've done it since the 1600s.

    https://www.louispage.com/blog/bid/11160/worm-fence-what-is-...

    Still, this seemed totally unecessary until I realized this mean they dont have to put any posts into the ground. No digging holes, which would be really nice when you're trying to fence up very large acreage.

  • by BobMackay on 7/27/23, 3:36 PM

    I think one should also consider the failure modes when, for example, a tree falls into the wall. For a straight wall, it is possible that a falling section will propagate the failure along the entire length of the wall. For a wavy wall, it is likely to fail in shear, limiting the damage to one section.

  • by hammock on 7/27/23, 2:00 PM

    Corrugated cardboard just is a wavy wall, sandwiched in between two straight walls.

    You can also observe corrugated steel and its use in construction, shipping containers, etc. Because these are steel and stronger than paper, the sandwich layers are not needed

  • by Terr_ on 7/27/23, 4:02 PM

    Another reason for some a wavy walls involves capturing more heat from sunlight over the course of a day, in this example for nearby plants:

    > The Dutch, meanwhile, began to develop curved varieties that could capture more heat, increasing thermal gain (particularly useful for a cooler and more northern region). The curves also helped with structural integrity, requiring less thickness for support.

    [0] https://99percentinvisible.org/article/fruit-walls-before-gr...

  • by vharuck on 7/27/23, 2:30 PM

    Soda cans also have a counterintuitive efficiency feature: concave bottoms. If a can with a flat bottom held the same amount of soda, it would be shorter and have less surface area, but its metal body would need to be thicker to withstand the same pressure. In the end, it'd require more aluminum.

    https://www.csmonitor.com/Science/Science-Notebook/2015/0414...

    ^Probably not the best article for this, but it was easy to find and has a link to a chemical engineer's video.

  • by andy800 on 7/27/23, 6:38 PM

    The University of Virginia, designed by Thomas Jefferson, features numerous brick serpentine walls.

    https://www.google.com/search?q=uva+serpentine+walls&tbm=isc...

  • by dang on 7/27/23, 4:36 PM

    Related:

    Crinkle Crankle Wall - https://news.ycombinator.com/item?id=33155781 - Oct 2022 (1 comment)

    Wavy walls use fewer bricks than a straight wall (2020) - https://news.ycombinator.com/item?id=25359550 - Dec 2020 (1 comment)

    Crinkle Crankle Wall - https://news.ycombinator.com/item?id=21554986 - Nov 2019 (56 comments)

  • by geeky4qwerty on 7/27/23, 1:51 PM

    This feels a bit like diet clickbait...

    "use fewer bricks than a straight wall"*

    *A straight wall of the approximal strength and length of a wavy wall, not just length.

    My counter would be that from a practical perspective the amount of space wasted by the wavy design seems to negate the usefulness of the design.

    Probably makes the lawn crew dizzy when mowing it too!

  • by CodeSgt on 7/27/23, 1:58 PM

    I feel like everyone this far is missing something, or perhaps just I am.

    I understand that a wavy wall will be stronger than a straight wall of the same thickness, therefore if you need that additional strength it technically uses fewer bricks to reach it.

    That said, if the alternative is a 2 layer straight wall, is the wavy wall equally as strong? Or is it just stronger than the single layer wall?

    Without knowing anything about the subject matter, I’d assume that the strength goes in order of single-layer straight, wavy, double-layer straight. No? Seems like needing just the amount of strength the wavy wall provides, and no more, would be a fairly rare use case. Leading to double-layer straights most of the time anyway.

  • by jamesmurdza on 7/27/23, 1:38 PM

    This looks similar to the way corrugated steel is harder to bend due to a higher "area moment of inertia".

  • by qwertox on 7/27/23, 1:47 PM

    Did my adblocker accidentally filter out the explanation?

    Following the link which is supposed to explain another thing, why it is more resistant to lateral forces, it contains an explanation:

    > The parameter a is the amplitude of the sine wave. If a = 0, we have a flat wave, i.e. a straight wall, as so the length of this segment is 2π = 6.2832. If a = 1, the integral is 7.6404. So a section of wall is 22% longer, but uses 50% less material per unit length as a wall two bricks thick.

    "as a wall two bricks thick". Hmmm. Even bigger savings as a wall three bricks thick.

  • by jolt42 on 7/27/23, 2:35 PM

    Has someone figured out the ideal frequency / amplitude of the wave? Maybe the frequency that matches the strength of a one-brick straight wall? The pictures strike me as possibly wavier than needed.

  • by dtgriscom on 7/27/23, 7:54 PM

    There's been a one-brick-thick wavy wall off a busy road in Cambridge for at least fifty years: https://goo.gl/maps/sxTsPW71F317gwK88

    It kept getting hit by cars until they finally installed a guard rail.

  • by nfriedly on 7/27/23, 1:45 PM

    I believe I've read that some plants do better when planted in the concave portion of a wavy wall, because the bricks absorb warmth during the day and release it at night.

  • by alecst on 7/27/23, 2:03 PM

    > As for the mathematics behind these serpentine walls and why the waves make them more resistant to horizontal forces like wind vs straight walls, check out this post by John D. Cook.

    The linked post does not explain why the walls are more resistant to forces. It just calculates the difference in length.

  • by omoikane on 7/27/23, 4:44 PM

    I first learned about serpentine walls via splint, which is a linter for C. The serpentine walls were visible on the front page until 2020:

    https://web.archive.org/web/20200521064022/http://splint.org...

    The FAQ explains why they chose this logo:

       The walls are one brick thick, but because of their design are both strong and aesthetic.  Like a secure program, secure walls depend on sturdy bricks, solid construction, and elegant and principled design.
    https://splint.org/faq.html#quest2

  • by Prcmaker on 7/27/23, 8:47 PM

    The same reason is why my roof has corrugated metal sheeting, rather than plate.

    This was a question I had students prove out. With the bending moment of inertia being related to the cube of the thickness for a flat plate, the maths trickles out very quickly.

  • by javier123454321 on 7/27/23, 1:38 PM

    Yeah but more space, and are therefore the wrong choice a lot of the time.

  • by NeoTar on 7/27/23, 2:04 PM

    "Popularized in England" - maybe popularized, but such walls are by no means popular or common.

    "The county of Suffolk seems to be home to countless examples of these crinkle crankle walls. On freston.net you can find 100 wavy walls that have been documented and photographed."

    Although it's not explicitly said, let's suppose that every one of those wavy walls is in Suffolk. The population of the county is 761 350 - let's assume there are 100 000 homes (although there is the city of Ipswitch, it's otherwise largely a rural county where single-family homes will be common). So only roughly one-in-one-thousand homes in Suffolk has such a 'wavy wall'. Elsewhere in the country probably even less - e.g. I've never seem one.

    Any for everyone complaining about mowing - do you actually have grass all the way up to your boundary wall? In my experience it's pretty common to have a flower bed running all the length of the boundary, so mowing would not be a problem.

  • by pfdietz on 7/27/23, 2:11 PM

    The labor to build such a wall may dominate the savings in brick. But if you're building a brick wall, maybe you don't care much about either.

    I wonder if this sort of structure could be built by 3D printing, say with concrete or even soil.

  • by cantSpellSober on 7/27/23, 5:30 PM

    No they don't

    > [Wavy walls] use more bricks than a straight wall of the same thickness

    However they "resist horizontal forces, like wind, more than straight wall would."

    > So if the alternative to a crinkle crankle wall one-brick thick is a straight wall two or more bricks thick, the former saves material

    https://www.johndcook.com/blog/2019/11/19/crinkle-crankle-ca...

  • by anArbitraryOne on 7/27/23, 8:50 PM

    Would it be stronger for the same amount of bricks if it didn't have the inflection point where there is no curvature, and instead had intersecting arcs like: ︾︾︾︾ ?

  • by kulor on 7/27/23, 2:11 PM

    Tangentially related; as covered in The Blue Factory documentary[1], one of the challenges with the EB110's design was its flat sides. Curved body panels provide greater strength and importantly, reduces vibrations.

    FWIW The Blue Factory had the same kind of charm as the General Magic documentary

    1. https://www.imdb.com/title/tt6301490/

  • by jansan on 7/27/23, 2:43 PM

    Of course title is a bit of a clickbait, because they are comparing walls of same strength, not single row straight walls with curved walls.

    But how does this compare with a straight wall with brick columns every two meters or so? My guess this is the best compromise, and maybe that is the best compromise, as it uses about the same number of bricks as a curves wall, but the area wasted is much smaller.

  • by tonmoy on 7/27/23, 2:30 PM

    Not sure about the actual function that defines the wave, but let’s assume they are convex and concave semi circles. Then to make a wall of length L with bricks of l length, we need piL/l number of bricks. The linked Reddit post says a straight wall needs to be 2 bricks wide to have the same length, which needs 2L/l number of bricks which is fewer than the wavy walls

  • by kazinator on 7/28/23, 6:02 AM

    Corrugated cardboard uses less paper than what it would take with flat paper, and the box weighs less.

    A wavy fiberglass roof uses less cloth and resin, and less reinforcement, than flat composite sheets would require.

    A wavy roadside guard rail made of sheet metal uses less metal than a flat guardrail.

    A snowshovel stamped/moulded with kinks in it can be thinner than a solid one.

    ...

  • by hyperhopper on 7/27/23, 8:16 PM

    This headline is awful and sounds sensational.

    Better headline would be "wavy walls use fewert bricks than thicker straight walls"

  • by Lio on 7/27/23, 8:28 PM

    I saw the title and instantly thought, of Suffolk, England.

    Quite pleasing to see it referenced in the article too.

    Proper Suffolk that, like little pink cottages and good quawlity tea towels[1]. :D

    1. https://m.youtube.com/watch?v=6-7hcPXwpBQ

  • by throwaway894345 on 7/27/23, 1:43 PM

    I’ll save folks some reading: they’re comparing a very thick straight wall with a much thinner wavy wall.

  • by serial_dev on 7/27/23, 8:42 PM

    > these wavy walls actually use less bricks than a straight wall because they can be made just one brick thin, while a straight wall—without buttresses—would easily topple over.

    And what about a straight wall with buttresses? Can we make them just as sturdy with fewer bricks?

  • by gowld on 7/27/23, 2:55 PM

  • by toss1 on 7/27/23, 2:19 PM

    Very cool. So what is the optimal solution?

    To maximize the strength and minimize the bricks used, is a sine the best shape, or is there a better curve, and what is the best period and amplitude of the waveform? Does this solution change with the height of the wall?

  • by trhr on 7/27/23, 2:02 PM

    Given how much OCD I have about naming variables and writing unit tests, I think if this was in front of my house, I'd take a sledgehammer to it. Fences shall be straight, damnit.

  • by carapace on 7/27/23, 6:27 PM

  • by HideousKojima on 7/27/23, 1:31 PM

    If you follow the link in the post explaining the math behind everything, it says:

    "They use more bricks than a straight wall of the same thickness but they don’t have to be as thick."

  • by silisili on 7/27/23, 5:03 PM

    Not a physics person...but is this similar to the effect of 'rolling' thin pizza so it won't droop? Or is it strictly about being better at wind resistance?

  • by spread_love on 7/27/23, 5:48 PM

    Another "article" summarizing a reddit post. They even took the top comment and put it at the end

    > wavy walls that lawnmowers surely detest!

  • by throw9away6 on 7/27/23, 1:49 PM

    I’ve seen this design when making ultra light weight structures. It does work but can be difficult to manufacture

  • by ilyt on 7/27/23, 8:24 PM

    At cost of like 5x the space ? I guess if you have cheap land but bricks are at premium it makes sense

  • by esafak on 7/27/23, 7:23 PM

    So, when it comes to pressure, the straight wall isn't "gonna take it"?

    (twisted sifter)

    I'll show myself out.

  • by fredley on 7/27/23, 1:56 PM

    In the UK these ate known by the wonderful term "Crinkle crankle wall"

  • by dontrustme on 7/27/23, 4:20 PM

    if you think of it from the context that the diagonal length of a brick is it's longest dimension, you can start to intuitively imagine how this efficiency in layout pattern is achieved.

  • by LegitShady on 7/27/23, 4:25 PM

    “Hackernews discovers first year university engineering statics/analysis from articles that are really just reposts of 3 year old reddit content”

  • by fnord77 on 7/27/23, 1:36 PM

    looks infuriating to mow around

  • by Jemm on 7/27/23, 6:55 PM

    fewer bricks than a straight wall with supports.

  • by MR4D on 7/27/23, 3:15 PM

    TLDR: they don't need buttresses, hence the savings.

  • by rkagerer on 7/27/23, 7:39 PM

    TLDR: Because they can be one brick thin. The waviness works just like corrugated cardboard.