Side by side structure model testing
September 12, 2008 at 12:32 am #3797
“there will be about 35 lbs of ballast pulling on it, and it needs to stay watertight.”
Thus a ring of screws around the join, with a generous slathering of water-proof adhesive. Still pretty cheap: a couple bucks of screws, a can of multi-purpose adhesive for another $5-$10. Plastic buckets essentially free if you aqlready have them or get them used.September 12, 2008 at 1:16 am #3798
This plastic is really slippery. I did not expect that I could find an adhesive that would stick to it. But if I can find it on this small island then that should work. I guess even if I have to order it this is still the best idea so far.
Hum. I have been reading about how they fuse/weld plastic HDPE pipe together with a bit of heat. Wonder if I could do that with the two buckets…September 22, 2008 at 12:35 am #3884
Casio is coming out with a camera that has a 20x optical zoom and can shoot at up to 1000 frames per second. It should be out next month and cost about $600. Shooting from the pier I could make some measurements of how far the models move and what the accelerations are. And slowing down 150 fps to 30 fps will make for great quality slow motion. Anyone seen a cheaper camera that can do 150 fps or better?September 24, 2008 at 8:53 pm #3909
I am thinking of getting this Casio Exilim EX-FH20 so I can shoot movies at 150 frames-per-second. I have found a couple places with a beach for launching the kayak and then a rocky shore next to deep water not far away. The Canon that I used from the pier in previous experiments has a 4x zoom and the video was usable with the models 100 feet from the pier and great at 50 feet. With a 20x zoom I should be in fine shape shooting video from a tripod on this rocky shore. If I have a PVC pipe sticking up from the model with every other inch of it black I will be able to measure movements and waves in the video using this for scale.
http://online.offshore.com.ai/anguilla/chart.gif – Just South of Eastern end of main island, and North of middle
Only problem is that I can only get small waves at the Eastern side when there is a tropical storm nearby to stop the trade winds here. The middle/North location will have small waves more often as it is on the protected side of the island. In any case, video of models in big waves is fun.September 25, 2008 at 2:30 pm #3915
I would think that with screws for strength, typical silicone caulking would work for sealant… Like tub and tile caulk.October 8, 2008 at 9:07 pm #3943
I played around with some models like these (although smaller scale) a number of years ago, and found that the up and down motion was almost impossible to get rid of with a free floating structure, but with an anchored structure it could be entirely eliminated.
I found that If my anchor systems weighed enough that the entire rig (including anchors) actually had negative buoyancy, but the anchor(s) rested on the bottom, it was possible to achieve a situation where a passing waves NEVER dropped the structure, they just increased and decreased the upward force due to buoyancy. Tension on the anchor line(s) will more or less, but they never go slack and the structure will never move up or down.
Additionally, multiple anchor lines also seemed to help with side to side stability.
Of course such system would only work in fairly shallow water, or the cost of the anchor system would quickly exceed the cost of the structure – but it might be worth playing around with.
Oh, and also, one additional drawback was that structures anchored like this had a tendency to jump out of the water and tip over if an anchor line was cut. Still, interesting posibilities…October 9, 2008 at 12:29 am #3944
In the gas/oil exploration industry, these platforms are called Tension Leg Platforms (TLP.) A severed cable is pretty much a total disaster.October 9, 2008 at 6:24 am #3945
We really want to be in international water and this tends to be deep water. So the tension legs can be expensive (as Sean said, maybe more than the cost of the structure). I also think it would be hard to scale down to single family size when your legs are miles long. I am mostly interested in the single family sized seastead. Another problem with TLPs is you can not do migration with a TLP, so you can’t use the bird’s trick of going where the weather is nice. So you have to be able to handle the worst possible weather from any time of year at that spot you are at. With migration you just have to handle the weather for that spot for the time you are there.
So currently I think migrating structures are the way to go as a general solution that can scale to many thousands of seasteads. There might be sea mounts near the equator, where there are never the really bad storms, that could work for TLPs in limited numbers. For a large seastead a TLP might be reasonable anywhere. The TLP is a nice trick worth keeping in mind.
Glad to hear of another person who has done modeling. I now know of 4 seasteaders who have made models, Patri, Wayne, me (Vince), and Sean. Are there others out there?October 12, 2008 at 1:30 pm #3958
I agree that migration is key, but I don’t think that rules out the TLP concept entirely as a useful idea.
If we have a design where one can adjust both the buoyancy of the structure and the tension of the cables, I can easily imagine a single spar sort of design that had some level of stability in free floating (deep water) mode, but could also be made more buoyant while at the same time having anchor lines tightened to pull it down into the water for necessary tension. this could both achieve a very stable fixed location in shallow water and also allow it to float free to travel into deeper water when so desired.
Maybe independent adjustable buoyancy chambers could reside on each of the anchor/ballast weights allowing them to be made heavy enough to provide a tension leg effect or light enough to be picked up from the bottom and just act as ballast when so desired?
It is also possible to imagine enough individual ballast / anchor cables such that a single point of failure might not be catastrophic – that where one cable failed, the remaining weights would still be heavy enough to keep the platform from surging out of the water past its balance point.
–SeanOctober 12, 2008 at 6:12 pm #3963
Yes, I think a TLP and migration could be done together. It would be fun to be able to lower a hanging ballast to the bottom of the harbor. You could kind of put your seastead in “park” and make a really stable TLP out of it. But in order to pull down hard enough when in park and still be able to lift everything when you wanted to move, I think you need to fill/blow-out a big chamber down in the ballast. So the big chamber, valves, pumps, etc add to the cost. It also makes for more things that can go wrong. But maybe…
I think when you are in a harbor or shallow water downwind from an island you will be seeing small waves. So if your seastead can handle open ocean alright then these shallow water situations are really easy. So I would not pay much extra for a feature that only helped then.October 12, 2008 at 8:59 pm #3964
I am calling the model I brought to the conference the “WaterWalker”. I have made a page for it with videos and pictures:October 13, 2008 at 6:09 pm #3969
Would the optimum comfort zone for this be when the balls are almost completely submerged? Are there other drawbacks with loading it up that much?
Do you hang the habitat only from the pole crossing (the tip, peak) or do you attach it to the middle of the poles as well? I´m thinking this could bend the poles.
Looks like it could be an efficient type of platform. Storm capacity is unknown though.October 13, 2008 at 7:49 pm #3970
>Would the optimum comfort zone for this be when the balls are almost completely submerged? Are there other drawbacks with loading it up that much?
I think it will be more stable with some more weight on it but have not tried it yet. With too much weight you could get to a point where the motion of a wave might put two balls underwater and the center might fall over the top of those two balls. I will probably try different weights in a month when I get a new camera that can shoot really nice slow motion.
>Do you hang the habitat only from the pole crossing (the tip, peak) or do you attach it to the middle of the poles as well? I´m thinking this could bend the poles.
I would hang it from the center/tip/peak. Instead of attaching to the middle of the poles you could have stabilizing ropes going to the 3 sticks near the 3 balls. Then there would not be any bending force on the poles.
I seriously think about building a prototype with telephone poles and winching my MacGregor 26 boat up as the habitat. The empty weight is 2550 lbs and there is a bunch of room. Since it is a boat it would be easy to get into position for winching after the WaterWalker was setup in the harbor. Would only pull it like 10 feet off the water. It sort of gives me a backup flotation plan. http://www.macgregor26.com/
>Looks like it could be an efficient type of platform.
Ya, I think so. Also seems fun that a used boat could be the habitat easy enough. It is kind of like putting training wheels on the boat.
>Storm capacity is unknown though.
Santa Cruz did not give me storm test conditions when I was there. People said that normally the waves were bigger. In Anguilla I have spots where I can simulate big waves and will do so.October 13, 2008 at 10:26 pm #3971
You could make habitable layers with this structure as well, each attached to the poles. Brilliant. No wonder it won all the contests.November 12, 2008 at 10:44 pm #4247
I got my new Casio EX-FH20 (thanks to TSI grant of $500!) which can shoot at 210 frames-per-second to make really nice slow motion video. I remade the WaterWalker from California (same balls but all else is new) and tried it out from the Island Harbor Pier here in Anguilla. The youtube “watch in high quality” did not show up at first but does now. I used their multi-file uploader this time as the regular upload method does not do well on 300 MB videos. Below is a sample from today.
This is slowed by a factor of 7 and I really want 5. The camera has modes like “1000 fps”, “420 fps”, and “30-210 fps”. I thought that meant that I could be anywhere between 30 and 210 but really it means you can switch between these while shooting a video. So I can’t set it to the 150 fps that would be perfect for making video slowed by a factor of 5.
There are some pauses in some of the videos, like at 2:26 in the above video. There is new firmware for this camera that should fix this problem.
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