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Ball House
Thu, 07/10/2008 - 02:19 — vincecate
Idea is that a 30 foot (9 meter) diameter ball with ropes going from the sides to a single hanging ballast maybe 100 feet down or more could be stable and very cheap. Truth is I found a 36 cm (14.2 inch) buoy on the beach that is just perfect for modeling this at 1/25th scale, so I will have to model it. And since I will be testing a model of this design I decided to write it up to match the model. :-) I think concrete could be reasonable for this, so it could be the cheapest design we ever find (like $100,000 cheap).
The idea is growing on me the longer I think about it. Should have results over the next week.
http://wiki.seasteading.org/index.php/User:Vincecate/BallHouse
I prefer a short cylinder
You are converging on my preferred low cost design, which is a short cylinder with a single ballast hanging below with 3 or 4 cables to support it. I think a short cylinder is easier to build and has more usable inside space available. It would have a "wave transparent" cantilever on top for a little more outdoor space during calmer weather. For "wave transparent", think in terms of a taut cyclone fence for the floor. I've asked a couple of our volunteer 3D modelers to draw one up, but nobody has done so yet.
It is one of the two designs that I will be putting on the table next week when we finally get some face-to-face time with the marine engineering consultants we are hiring.
What sort of dimensions do you like?
I guess slip forming does work well for a cylinder so that is much easier to make out of concrete.
I am going to be doing some 1/25th scale models this next week. What dimensions do you like for your low cost cylinder? Like 40 feet high and 25 foot diameter or what?
Seems like a 5 gallon paint bucket would make an interesting model and I have one, so I can add that to the collection.
Bucky Balls and Soccer Balls
You can make a ball out of 12 pentagons and 20 hexagons where all the sides are the same length. Bucky Balls and Soccer balls are made this way. So 32 pieces of only two different types. So you could make a big ball by bolting together 32 smaller pieces of plastic made from 2 molds (or maybe fusion welding with heat). You might also construct an aluminum ball out of 32 pieces and use that as the rotomold for making a single large plastic ball.
.
So now I wonder if I can make 32 plastic pieces that when put together make a ball big enough for 2 guys to play on in the ocean with a hanging ballast for stability (really 31 to leave top open). Just need 2 molds. Seems some types of plastics can be pored into plaster of Paris molds. Can heat the plastic on the kitchen stove. The ball could be like 7 foot diameter. The ballast a big block of concrete. There are crane trucks that could pick up the ball and ballast to take to the upwind beach or to return home from the downwind beach. The tricky part may be lowering the ballast as you go to deep water and winching it back up when you get to the downwind beach.
http://www.allsands.com/home/crafts/plasticmoldedo_tyo_gn.htm
http://online.offshore.com.ai/balseros/
Another method is to put the raw plastic on the mold and just put the mold in your oven. I think the pieces I need would be small enough to fit in my oven. So this could work too.
Another way is to have the mold in some cooking out that is being heated. Could do this outdoors.
Nice thing about this is you could make a 7 foot one, then a 14 foot one, then a 25 foot one. Just doing a little bigger prototype each time. If you went to production then probably the rotomold would reduce costs.
Though not AS spherical...
An icosahedron (http://en.wikipedia.org/wiki/Icosahedron) or a dodecahedron (http://en.wikipedia.org/wiki/Dodecahedron) may be just that much easier to make, because they will only have one mold, and could yet be spherical "enough" for asthetics and what not.
Just a thought.
Paint Bucket works for me
My nominal dimensions were 50 ft high by 20 ft diameter. This give a nominal floor area of ~300ft2 on 4 floors (10 ft. ceiling) for 1200ft2 of living area. A ladder would be used to move between floors (this is kind of kid hostile.) Area wise, this is better than a studio apartment, but not much better. There would be an additional 300ft2 on top, plus whatever the wave transparent cantilever provides during calm weather. I would ballast until about 3/4 of the structure is submerged.
The concept behind this design is to have something that will survive really bad weather, be inexpensive to build, and be more comfortable than and roomier than spending the same amount of money on boat. Let me reemphasize here, it just has to safer/cheaper than a boat.
These designs would be the single family dwellings of my Venice style vision of a seastead community.
Having said all of that, I think the paint bucket is an excellent stand-in.
Models just about ready
I am almost ready to put a bunch of models into the ocean. Put up a couple pictures on my wiki page. Should be in the water in the next day or two.
http://wiki.seasteading.org/index.php/User:Vincecate/Models
PVC Not Very Buoyant
My experience with PVC is that it was not very buoyant. Your experience may be different. I eventually discovered swimming pool noodles. These are close cell foam cylinders that are extremely buoyant. The have a hole in the middle that can be threaded with twine or whatever.
I did all my initial testing in the kitchen sink.
Larger diameter pipe floats better
I think 2-inch pipe and larger diameters will float ok. I am mostly using 2-inch sched-40 pipe. This weighs a bit less than 1 lb per foot (19 feet weighs 14 lbs) and displaces almost 2 lbs of water, for a net boyancy of around 1 lb per foot. For 1/25th scale models it seems you probably want 2 inch pipe or larger, since 2-inch in the model is only 50-inch diameter pipe in a full scale version. Could also use thinner PVC pipe (not shed-40) if this seems too heavy.
The catamaran in the picture floats fine in my pool. With a 2.5 lbs weight as cargo it still looks fine. With 5 lbs it is too low in the water. This catamaran has the most fittings (which are heavy and don't add to bouyancy) of all my models and the most up out of the water. So since this works I think they will all work.
3rd set of videos of Ball House model tests
Took some more video of my Ball House model today.
http://wiki.seasteading.org/index.php/User:Vincecate/BallHouse#Experimen...
I agree with Wayne with
I agree with Wayne with regard to the conceptual similarity with the low cost seastead design discussed earlier.
Awesome you are putting it to the test: the link is not working for me at the moment, but id love to see it in action!
Wiki is back up now
The wiki was down this morning is back up now. Yes, this is similar to Wayne's design.
I like the way this rides the waves. Wayne's with a long hanging ballast might do the same. Even steep and breaking waves kind of fade away as this backs up a bit at the peak and sort of kills them. So the breaking waves are not even splashing this thing. I like to watch these videos. Also, I really think this would survive 100 foot waves.
I wish I had a good model for Wayne's design. I actually found a boat fender that might work. It is 1 foot diameter and 3 feet long and we really want 2 feet long. Not eager to pay for it though. http://www.chsmith.com.au/cgi-bin/hex4.pl?Display=191
I think Wayne does not really need a truss but I am not sure. It seems easier for a wave to tip over a cylinder than a ball. He probably does need a heave plate.
Also, mine at 30 feet is really smaller than his 50 foot design. And his flat top and bottom will have to be thicker than a rounded shape thing like mine.
A problem with heave plates is they might hold the structure down so that a big wave could go over the top. This ball does not seem to have that problem.
Mine should heave more on an 8 foot wave than Wayne's because of the larger waterline area. So while mine might do better on 100 foot waves, I don't really expect to ever see such waves because of migration. The normal wave is probably more like 8 feet. So I think mine is "lower cost and lower comfort" than his. Depending on the real cost and comfort values, and people's budgets, they might choose either.
I have tested a number of models. You can find links to results here: http://wiki.seasteading.org/index.php/User:Vincecate/Models
-- Vince
Engineering Trade-offs
My disjointed comments are below:
As long as you are inside one of these things, I think they will all survive huge waves and high winds. You might not enjoy the experience, but you would survive. Now the issue is to figure out the engineering trade-offs between cost, comfort and livable volume.
I'm pea green with envy of your ability to build a model and take it out to the ocean and test it out. We have ocean available in the San Francisco Bay area, but it is not easily accessible, and it is really cold.
Please understand that the 20' by 50' cylinder is just a rough guess. It might get a little rounded off on the bottom as the design progresses.
I've looked at the ball videos with a long cable and concluded that I do not know what is really going on. The cable does not appear (to me) to remain vertical. Instead, it seems to allow a fair amount of side angle. I wonder if some sort of "double pendulum" effect is going on. By this I mean, waves push the ball to one side, this causes the mass below to swing like a pendulum, which pulls the ball along behind it. Repeat.
I figure that once people are inside the structure, the primary purpose of the heave plate is to improve comfort. If some waves break over the top, so be it.
Anyhow, those are my random comments.
Free seastead model testing services
>I'm pea green with envy of your ability to build a model and take it out to the ocean and test it out.
>We have ocean available in the San Francisco Bay area, but it is not easily accessible, and it is really cold.
I grew up in the bay area and remember how cold that water is. In Anguilla I can get to several good test places in a few minutes so I have easy access to different wave sizes. I doubt you can buy time in a 30+ foot deep wave tank, which I get for free. :-) Also, we have very clear water so underwater pictures are possible (far better than the bay area visibility). I can even get small versions of breaking waves that look very much like scaled down versions of the dangerous waves I see in books like "surviving the storm" where really only a small part at the top of the wave is breaking. I think my last two tests are very realistic for what the model would do in 30 to 50 foot waves, more so than you could do in a wave tank. And I do have reasonably warm water all year so I can do tests anytime. Anyway,I would be happy to test out any seastead models that anyone wants to send to me. I can provide any ballast, so you would just need to send the rest of the model.
Yes, the cable moves over quickly at the top with the ball and may even move back before the ballast moves over much. If the ball moves over a foot, the sideways force on the ballast hanging from a 23 foot rope is just not much. With the drag of the water it is not going to swing back and forth fast. So it kind of stays below the average position of the ball as the ball moves back and forth with the waves. It really works out well.
>I figure that once people are inside the structure, the primary purpose of the heave plate is to improve comfort.
> If some waves break over the top, so be it.
If you can be sure that waves never go over the top you can build things more cheaply on top. So it could make for a cheaper overall seastead.
You can stay dry when testing models from sea-kayak
I sometimes use my Hobie Outback kayak, with peddles. http://www.hobiecat.com/kayaking/models_outback.html
This is nice because going 1/2 mile out to get the right sized waves is nothing with leg power. It has a good cargo area in the back that can hold models. I can hold the camera with one hand, and steer with the other while my legs provide power. I can keep me where I want to be, more or less. I can only steer with the ruder when I am moving, so if I want to change direction I kind of have to go faster than drifting speed for a bit. This is fine for keeping within 20 feet but not good for keeping within 4 feet like I can when I am in the water.
Anyway, I don't really get wet when I use the kayak (though my phone, wallet, and keys do go in a dry bag). You could do this at a number of places in the bay area. You would have to drive further than I do. But you don't really have to get in the cold water. And wet suits are cheaper than this kayak, so they are not a bad idea either.
Now I can leave my kayak on the beach at my father-in-laws, 5 minutes from my house, so it is really easy for me to just go. Anyway, I really am happy to test any models people want to send me.
PS Hobie has 2 person, inflatable, and 2 person inflatable peddle kayaks. These all seem worth looking at.
PPS It just occurred to me that if I took the paddle apart I could use half as an oar in one hand well enough to control my direction while drifting and then legs to keep position would work. So I think I can keep closer while using the camera.
That Kayak rocks.
I seriously want one. I've got a new item for my christmas list now.
Nice kayak
Ya, it is a nice kayak. It is so easy to use my 4-year old son can do it:
http://www.youtube.com/watch?v=d20kNFCkIy0
This is on his second day doing it on his own and he is very comfortable going all around the harbor. He is almost 5.
You can see him in slow-mo in my latest tension circle test. I am trying to get a water level that shows up well on camera but does not slosh back and forth too much. There were very small waves and it looked like the water inside was not even moving, so I asked him to bump it or lift the model, and I did too. It was a bit late in the day so there was not really enough light for this camera.
http://www.youtube.com/watch?v=5meYHNUJtn4
I browsed through your ball
I browsed through your ball videos. Regarding the ball being pushed sideways, do you think this (the rolling to one side when this happens) is dependent on the cable length, or is it more due to the ball twisting away from the cable "vector".
I saw some of this happening. Would not several cables (3 at 120 degree intervals most likely, possibly suggested below) eliminate this instability and make for a smoother ride? How long was the cable, by the way?
Multiple cables for extra stability from hanging ballast
Yes, you can use multiple cables to make things a bit more stable. I actually did that and you can see some video below.
I am sort of amazed at how well a single cable works. The extra cables increase your static stability (how much you tip if you slowly add weight to one side) but the extra length helps what you really need which is a dynamic stability in the waves. The long rope was 23 feet. With the long rope the ball does not tip much. It seems much better to have 1 rope 23 feet long than 4 ropes 7 feet long. But 4 ropes that were 23 feet long would be a bit better than 1 ropes that was 23 feet long.
http://wiki.seasteading.org/index.php/User:Vincecate/Models/HangingBalla...
While the extra 23 foot cables could make the ball tip even less, it would still accelerate to the side about as much and I think that is going to be the main source of discomfort in these big waves.
Yes, that first video with
Yes, that first video with the bucket and four cables is what I had in mind. Though I would use three due to the inherent stability of that setup. Also, optimally the cables should probably be attached and converge as close to the center of mass of the counterweight as possible.
Of course the weight would be divided on the individual cables so they needn´t be the same size as the single one. I don´t think this will be much more expensive than a single cable. A bit of extra cable cost perhaps (but hardly three times as much), and some additional fasteners should do it.
Well, ok some extra labor of course, and the cables need to be of equal length which adds a need for more precise manufacturing. Still, I would bet it would be worth it to get rid of those small rolling motions.
One would have to make sure that none of the cables ever went slack though as I´m sure this would produce dangerous impact forces on the structure.
multiple cables for hanging ballast
>Of course the weight would be divided on the individual cables so they needn´t be the same
>size as the single one. I don´t think this will be much more expensive than a single cable.
The big win with the multiple cables to a single ballast is that it can sort of shift the full weight of the ballast over to whichever side is trying to lift up. For this to work the cables all need to be able to handle the full weight of the ballast.
But the truth is cables are cheap and even 3 of them is still cheap. I don't think the extra cost is much of an issue here.
>One would have to make sure that none of the cables ever went slack though as I´m
>sure this would produce dangerous impact forces on the structure.
Yes. But I think there are reasonable width seasteads where they won't go slack for waves up to reasonable sizes. It is something to check, but I think it can work.
-- Vince
You are quite right about
You are quite right about the load shifting over to one cable. I totally overlooked that. Still, with three cables a cable break is not as disastrous as with one so you mighgt be able to decrease the safety margin a bit. Although i agree too that the savings from using smaller dimension cable might not be that big.
With several cables you would need to calibrate the whole arrangement so it floats level. Probably nothing a simple mechanism like some eye bolts and nuts won´t manage, but still worth keeping in mind when comparing complexity between different arrangements.
More spherical and still one mold
This has 30 sides and only one mold would be needed.
http://en.wikipedia.org/wiki/Triacontahedron
This one has 60 faces and only one triangle. Could make a very large ball out of pieces that would fit in my oven:
http://en.wikipedia.org/wiki/Pentakis_dodecahedron
This has 60 faces and piece of bigger area than triangle might fit in my oven:
http://en.wikipedia.org/wiki/Pentagonal_hexecontahedron
Pouring 30 or 60 pieces of aluminum and bolting them together is not out of the question either. Even welding 30 pieces of aluminum would be very sensible. Even doing a 25 foot diameter ball from aluminum plate is not a crazy amount of money. http://www.metalsdepot.com/products/alum2.phtml?page=plate&LimAcc=%20&ai...
Very nice.
I really like the pentagonal hexecontahedron. Nearly spherical, plus a hint of futuristicness to it. 60 pieces compared to 32 on the soccer-style, and only the 1 mold. I'm a buyer.