User:Vincecate/Models

Idea is to use about the same amount of pipe in each model so they are sort of cost comparable and then test them all in the waves at the same time. Expect to have waterproof camera around July 10th.

I am going to assume migration makes 25 foot waves the largest we have to deal with because with a 1:25 scale model that makes for a nice round 1 foot wave.

With a 25 foot maximum wave measured trough to crest, we sort of only need 12.5 feet above average water level. But with rogue waves and safety margins, lets design for 25 feet above average water level. Seems like a spar with 25 feet above water could have a total length of 250 feet. Scaled down for 1:25 model we could use 10 feet of PVC pipe. If I use 2 inch diameter pipe in the models that is like 50 inches diameter in the full scale version.

So I will try to use about 10 feet of 2 inch pipe for each model. Some models might want some smaller or larger pipe, and more or less fittings, so I may end up trying to use the same total weight of PVC with each model. Cost estimation sort of indicates that the same weight steel ships are about the same cost. So if PVC in the models is replaced by steel in the full scale versions, equal weights will be roughly equal costs.

PVC models planned

• Tension Circle House
• multi-spar - like Versa Buoy - maybe a triangle - 3 pieces of 3.3 feet each - T-shape of lighter pipe for platform - elastic cord holding legs to platform so can flex
• Pipe Spar - 10 feet of 2 inch pipe
• fat-short pipe spar - using 3.5 feet of 4 inch pipe instead of 10 feet of 2 inch pipe other models get
• semisubmersible - can have square or triangle of pipes underwater and legs sticking up or frame on top legs down
• hanging ballast - use multi-spar or semisubmersible but with 3 or 4 strings to single ballast in middle, can also try pipe-spar and fat-short pipe-spar
• catamaran - 10 feet of 2 inch pipe cut and with fittings to make catamaran
• beach ball half full of water with some sand in the bottom - kind of the givens life raft design.

• raft made by lashing pipes together - 5 pieces with 2 cross pieces underwater (120-(2*12)/5= ~19 inches for 5 pieces

Video

At the start of the video there will be a full glass of water on the model. During the video the motion and splashing of water, as well as how much is left at the end of the video, will give help give some idea of how stable it would feel to someone standing on the structure.

I will also have a washer on a string that can swing back and forth. The maximum height of swing will also be a measure of stability.

Will have pipe that is tied to weight on the bottom so it does not move up and down in the background for comparison and measuring wave heights (will have marks on it).

The camera will be oriented so that the big waves are coming from one side, so water in glass motion is more visible. Might use colored water.

I will shoot video from the side with a horizon/beach/island in the background for a stable reference point.

I will also shoot video with the camera mounted on the structure. Slowed down the view of the glass of water, waves, and horizon should be interesting.

Plan to make a poor mans steady-cam to help stabilize the camera.

Still shots

Will take still shots of each model out of the water, in the water, and view from under water.

Force for Scale model speed testing

The force on a scale model should scale with the mass, which is with the cube of the scaling factor. So for a 1/25th scale model, the force should be 1/15625. So we have:

  8 ton kite -->  1 lb
  16 ton kite --> 2 lbs
  32 ton kite --> 4 lbs

Weights from a weight set or a gallon jug filled with the right amount of water could be a good weight. With a known weight being pulled down by gravity you can provide the same force to the model by connecting a rope between the model and the weight over a pulley. Just have to keep pulling the pulley forward at the right speed so that the weight stays between the pulley and the ground or water. With my Hobie pedal powered kayak I think this will be easy enough.

However, a similar weight and pulley walking alongside a pool is probably easier. So I may just do that. But the deepest pool I have access to is just over 6 feet deep.

With speed results from this we can see how fast such a kite could pull a full sized seastead. This will tell us if the migration idea is plausible.

Problems

• normal sched-40 fittings are heavy (elbows, Ts, etc) - try to find lighter ones
• not clear 10 feet of pipe can make some of the designs clear 1 foot waves (or even 6 inches)
• what to use for ballast - washers, cement, water, lead, weights from weight set
• some have ballast, some have strings, some have platforms
• joints and bending in models are not modeling full scale materials or design
• catamaran really needs stronger pipe than other designs - could use sched-40 for it and thinner for others - but then they should have more or bigger diameter pipe

Previous models

• Tension Circle House
• Tension Circle Marina

Modeling in general

• Scale models

Sponsors

My two summer students and I will build, test, and document the results for a number of these models. If you would like to support this effort we are accepting sponsorships at $100 for each model. You can just put your name here and after we are done you can pay via paypal. Thanks.

• multi-spar - Joep (already paid)