🌊 FreshWater Building Plans

Gather 2,000+ clean 2L PET bottles with caps. Inspect each: no cracks, no deep scratches, cap must thread on tightly with no stripped threads. Rinse and dry completely — moisture inside bottles promotes mould. Sort into bins of 120 bottles (one pontoon section each). You need 16 bins.

For each of the 16 sections: Lay bottles in hex-pack formation on a flat surface (first row of ~12 bottles touching side-by-side, second row nests into the valleys, repeat). Apply marine sealant at every bottle-to-bottle contact point. Once the section is complete (~120 bottles), wrap tightly in UV-resistant mesh netting. Secure netting with UV-rated cable ties every 200mm. Let sealant cure 24 hours.

For each pontoon: Line up 8 cured sections end-to-end on a long flat surface. Apply marine sealant generously at every section-to-section joint. Wrap the entire 7.6m pontoon in one continuous outer layer of mesh netting, pulling tight with cable ties every 300mm. The finished pontoon should be rigid — pick up one end and the whole pontoon lifts as a unit. If it sags, add more cable ties and netting wraps.

Lay both pontoons parallel, 2.4m apart (inside edge to inside edge). Position 4 aluminium cross-beams evenly spaced along the pontoon length. Each beam passes over both pontoons. Drill through the netting and into the bottle pack at each beam mount point. Bolt through using M8 bolts with fender washers on both sides — the washers distribute load across multiple bottles. Torque to snug but do not crush bottles.

Cut marine plywood panels to fit the cross-beam frame. Lay panels on the beams and mark bolt positions. Pre-drill all holes in the plywood, then through-bolt to the cross-beams with stainless M8 bolts and fender washers. Seal all cut edges and bolt holes with marine sealant — unsealed plywood delaminates in water. Sand the deck surface with 120-grit for non-slip texture. Apply 2 coats of marine varnish or paint.

Launch the completed hull (no subsystems) in calm water — a lake, harbour, or protected bay. Load with ballast (sandbags, water jugs) to 50% of rated capacity (~600 kg). Check: (1) Waterline should be at approximately 40% of pontoon height. (2) Deck should be level — measure with a level at multiple points. (3) No visible leaks or bubbling from pontoons. (4) Stable in light chop — should not roll beyond 10° in small waves. If issues found, haul out and repair before adding subsystems.

Cut marine plywood to make 4 open-bottom boxes (600×400×500mm each — 4 sides + 1 top, no bottom). Assemble with stainless screws and marine sealant at all joints. Line the interior of each box with 2 layers of fibreglass cloth saturated with polyester resin. Let cure 24 hours. The interior must be 100% waterproof — any leak reduces chamber pressure and kills output.

Cut a 100mm hole in the center of each chamber's top panel using a hole saw. Mount a 200mm length of 100mm PVC pipe vertically over each hole using marine sealant. The pipe extends upward — this is the turbine housing where air rushes in and out as waves move the water column inside the chamber.

For each turbine: cut 4 symmetrical airfoil blades from aluminium sheet (50mm wide × 40mm long). The key property of a Wells turbine is that blades are at 0° angle of attack — they are FLAT, not pitched. This makes them spin the same direction regardless of airflow direction. Mount blades to a 10mm shaft at 90° intervals using small clamp collars or brazing. Install the shaft in the PVC housing with a sealed bearing at each end.

Attach each DC generator to its turbine shaft via direct coupling (shaft adapter) or small belt drive. Wire each generator output through a bridge rectifier (converts AC-like output to clean DC). Connect all 4 rectifier outputs in parallel to a common power bus. Test by spinning each turbine by hand — the multimeter on the bus should show voltage rising with each turbine spin.

Bolt all 4 OWC chambers to the underside of the catamaran deck, evenly spaced between the pontoons. The open bottoms face the water. Seal all deck bolt penetrations with marine sealant. Route generator wiring through sealed deck conduit to the power system. Verify each chamber is level and square to the deck.

Launch the platform in water with waves (even small harbour chop works). Monitor each turbine: it should spin visibly. Measure voltage on the power bus — in moderate waves expect 12-14V unloaded. Connect a test load (12V LED bank or resistor) and verify sustained output. If any chamber shows no output, check: air leaks (listen for hissing), stuck bearings (spin by hand), and generator coupling (shaft turning but generator not?).

Mark a straight line down the length of each 200L drum, then mark the opposite side. Cut along both lines with an angle grinder or reciprocating saw to create 2 half-cylinders per drum (4 total). Deburr all cut edges with a file or flap disc — edges will be razor sharp. Clean inside and out. Apply rust-inhibiting primer to all surfaces, then topcoat with marine paint. Let dry 24 hours.

For each turbine: weld or bolt 2 circular endplates (300mm diameter, cut from 3mm steel plate) to the 20mm shaft at the top and bottom of the scoop zone. Mount 2 half-cylinder scoops between the endplates, offset by half the cylinder diameter — viewed from above, they form an S-shape. The scoops attach to the endplates with bolts or welds. Verify balance by spinning on a horizontal axle — add counterweights (bolts) if one side is heavier.

Install a sealed bearing at each end of the 3m galvanised pipe masts (top and bottom). The turbine shaft passes through these bearings and must spin freely. If bearings don't press-fit, use bearing housings bolted inside the pipe. Test by inserting the shaft and spinning — it should coast for 10+ seconds.

Mount each DC generator at the mast base. Couple to the turbine shaft using a flexible coupler (handles minor misalignment). Wire each generator through a bridge rectifier. Route wiring down the inside of the mast pipe to the deck. Connect both turbine outputs in parallel to the power bus.

Bolt flange mounts to the deck at fore and aft positions (reinforce deck underside with plywood doublers). Stand each mast in its flange. Attach 4 guy wires per mast — anchored to deck cleats at 90° intervals. Tension with turnbuckles until the mast is plumb in all directions. Tighten flange bolts fully.

Construct a rectangular frame from aluminium angle stock that spans the deck area designated for solar (typically the center 2/3 of the deck). Frame height: 2.2m at the low side. Tilt the south-facing edge up 15° (in northern hemisphere — reverse for southern hemisphere). Support with 4 vertical posts bolted to the deck with flange mounts. Add cross-braces for rigidity — the canopy must withstand wind loads without flexing.

Place each panel on the canopy frame rails. Insert rubber grommets between panel frames and rails (vibration isolation). Bolt through with M6 stainless bolts — snug but not overtorqued (the grommets must remain slightly compressed, not crushed). Space panels 20mm apart for airflow cooling. Leave access gaps for wiring and maintenance.

Connect 3 panels in series using MC4 connectors: Panel 1 positive to Panel 2 negative, Panel 2 positive to Panel 3 negative. This creates one string at ~60V open circuit. Build 2 identical strings. Run cables from each string down the frame posts to the charge controller location. Use cable clips to secure — no loose wires that could chafe in wind.

Mount the MPPT charge controller inside the weatherproof enclosure. Run cables through IP68 cable glands. Connect the 2 solar strings to the controller's PV input (observe polarity). Connect the controller's battery output to the main battery bank (see fw-power-system). Configure the controller for 48V battery, LiFePO4 chemistry (or appropriate chemistry for your battery bank).

On a sunny day, verify: (1) Each string reads ~60V open circuit. (2) Controller display shows PV input voltage and charging current. (3) Battery bank voltage is rising. (4) No hot connections (feel each MC4 joint and terminal — warm is OK, hot means a bad crimp or loose connection). Record peak wattage for baseline performance reference.

For each of 8 towers: cut 150mm PVC to 1.5m length. Mark 12 evenly spaced positions for plant holes (staggered spiral pattern — each hole 120mm apart, rotated 60° from the previous). Drill or cut 50mm holes at each position. Deburr holes. Glue PVC end cap on the bottom. Drill a 12mm hole in the end cap for the drain fitting.

Mount towers vertically on the canopy frame or deck railings using stainless pipe clamps (2 per tower). Run 12mm poly tubing from the pump outlet to a manifold, then branch to the top of each tower. Run drain lines from the bottom of each tower back to the reservoir. Use barb fittings and hose clamps for all connections. Verify no leaks by running the pump with plain water for 10 minutes.

Construct 4 shallow beds (600×400×100mm) from marine plywood scraps. Line each with pond liner — fold corners neatly and staple to the outside. Fill with a 50/50 mix of perlite and coco coir. Install cotton or felt wicking cord running from the bottom of each bed down into a small elevated reservoir (a 5L bucket mounted above the beds). The wick draws nutrient water up by capillary action.

Fill 96 net cups with clay pebbles. Transplant seedlings into the cups (roots dangling into the tower). Mix seaweed nutrient solution (see fw-seaweed-nutrient plan) into the 60L reservoir at recommended dilution. Start the pump. Verify water flows from the top of each tower and returns to the reservoir. Check pH (target 5.8-6.5). Sow seeds directly into the rooftop beds for herbs and microgreens.

Collect 5kg of fresh seaweed from the ocean — pick from rocks at low tide or gather from the tideline (only fresh, not decomposing). Rinse 3 times in fresh water: fill a bucket, agitate the seaweed, drain, repeat. The third rinse water should be relatively clear. Pick out any visible shells, stones, or debris.

Spread rinsed seaweed in a single layer on drying racks in direct sunlight. If no racks available, spread on clean concrete, plywood, or hung on lines. Turn the seaweed once daily. Dry for 2-3 sunny days until completely crispy and crumbly. If weather is humid, this may take 4-5 days. Seaweed must snap when bent, not flex.

Crumble dried seaweed by hand into a bucket. For finer particles, use a mortar and pestle or place in a bag and crush with a rolling pin. Add 10L of fresh water to the bucket (1:20 ratio by weight). Stir thoroughly. Cover the bucket loosely (allows gas exchange but keeps debris out). Let steep for 48 hours, stirring once each day. The liquid will turn dark brown-green and develop a mild ocean smell.

Pour the steeped liquid through muslin cloth or fine mesh into storage bottles. Squeeze the cloth to extract maximum nutrient liquid. Compost the solid residue (or add to rooftop beds as mulch). Test pH of the concentrate — typically 6.0-7.0. To use: dilute 1:10 with fresh water and add to the hydroponics reservoir. Adjust pH to 5.8-6.5 with vinegar (lower) or baking soda (higher). Store concentrate in opaque bottles out of direct sunlight. Use within 2 weeks.

Build 2 floats using the same hex-pack technique as the hull sections — 120 sealed PET bottles per float wrapped in UV mesh netting with marine sealant at all contact points. Before sealing each float, insert 2 sand ballast bags (5kg each, double-bagged) into the center of the hex-pack. The ballast lowers the float's center of gravity for stability. Let sealant cure 24 hours.

Cut 2 aluminium tubes to 2.5m length. At the hull end: bolt on a heavy-duty marine hinge. At the outboard end: weld or bolt a flat mounting plate (200×200mm) for the float attachment. Drill through-bolt holes in the float mount plate. Test the hinge action — arms must fold flat against the hull for transport and deploy at 90° for operation.

For each generator: Wind copper coils around the outside of a 300mm PVC tube (4 coil sections, 200 turns each). Epoxy 4 neodymium disc magnets to a 10mm steel rod at 50mm spacing (alternating polarity). Insert the magnet rod inside the PVC tube — it should slide freely. Cap both ends with loose-fitting PVC caps (the rod must move but not fall out). Wire coils in series through a bridge rectifier.

Mount linear generators on the outrigger arms using pipe clamps (oriented so the piston axis is vertical when the arm is deployed). Attach floats to the arm end plates with through-bolts. Mount the complete arm assemblies to the hull sides via the hinges. Attach guy lines to limit arm travel range in storms. Wire generator outputs through the arm (cable-tied along the tube) to the deck power bus.

Launch the platform with outriggers deployed. Compare roll behavior to the bare hull test (should be dramatically more stable). In moderate waves, measure voltage output from each linear generator — expect 2-5V per generator with each wave cycle. Combined output through rectifiers should contribute measurable charging current to the battery bank. Record baseline for maintenance reference.

Build a small charcoal-fired furnace: line a steel bucket with 50mm of refractory cement. Let cure 48 hours. Place the crucible inside. Fill around and below with lump charcoal. Light with a blowtorch and add forced air (hair dryer or shop vac on blow) to reach 660°C+. Feed clean aluminium cans into the crucible — they melt in seconds. Skim slag with a steel rod. Pour clean aluminium into ingot molds (muffin tins or steel channels). Cast at least 2kg of ingots for gears.

Create a pattern for each gear (wood or 3D-printed disc with teeth profile). Pack casting sand around the pattern in a 2-part flask (cope and drag). Remove pattern, cut a pour sprue and risers. Melt aluminium ingots and pour into the sand mold. Let cool completely (1 hour minimum). Break out the casting. Clean off sand and flash. Drill center holes and cut keyways for shaft mounting.

Weld or bolt a steel plate box (housing) large enough for all 3 gear pairs. Mount shafts on bearings inside the housing. Install the 3 gear pairs (3 ratios). Build a selector mechanism — a sliding key or dog clutch that engages one gear pair at a time. The gearbox should have: input shaft (from turbine), intermediate shaft, and output shaft (to propeller). Seal the housing with gaskets and fill with grease.

Drill a through-hull hole at the stern between the pontoons for the propeller shaft. Install the stuffing box (watertight seal) in the hole. Insert the propeller shaft through the stuffing box. Mount the propeller on the outboard end with a cotter pin. Connect the inboard end to the gearbox output via the flexible coupling. Tighten the stuffing box packing until it drips 1 drop per second at rest (correct tightness).

Connect the gearbox input shaft to one OWC turbine output via a slip clutch. The slip clutch is a friction disc assembly that slips under overload — protecting gears from wave shock. Test each gear ratio in calm water: engage ratio, rock the platform to simulate waves, verify propeller turns. Then test in actual waves — the platform should move at 1-2.5 knots depending on conditions and gear selection.

Arrange 16 LiFePO4 cells in series (positive of cell 1 to negative of cell 2, etc.). Use nickel strip or bolted bus bars for connections. Install the 16S BMS — connect the balance leads to each cell junction point. Build the battery box from marine plywood: ventilated top (drill holes + mesh), water-resistant bottom (marine sealant). Place cells in the box with foam spacers between them. Verify total voltage: ~51.2V (fully charged: ~54.4V).

Mount the marine fuse panel in a weatherproof location (inside the equipment bay or under the solar canopy). Run the main positive and negative bus bars from the battery bank to the panel. Install individual fused circuits: desalination pump (15A), hydroponics pump (5A), LED lighting (3A), monitoring (1A), Fuze pump (5A), spare circuits for future loads. Label every circuit. Size wire gauge for current and run length.

Connect all generation sources to the battery bus: Solar MPPT controller output (already installed per fw-solar-array). Wave engine rectifier bus. Wind turbine rectifier bus. AirGen engine outputs. Outrigger linear generator outputs. Each source should have a blocking diode or dedicated charge input on the controller. Verify polarity of EVERY connection before powering on.

Wire ACS712 current sensors on the main positive bus (one for total charge, one for total discharge). Build voltage dividers (100kΩ + 10kΩ) to scale battery voltage to 3.3V for the ESP32 ADC input. Connect a temperature sensor (DS18B20) to the battery bank. Program the ESP32 to read and log: battery voltage, charge current, discharge current, temperature. Display on an OLED screen or serve via WiFi.

With all sources connected and all loads wired: (1) Verify battery charges from each source independently. (2) Turn on each load circuit and verify operation. (3) Run all loads simultaneously and verify battery voltage remains stable. (4) Test BMS protection: simulate over-discharge by running heavy loads with no generation — BMS should disconnect at ~2.5V per cell. (5) Record baseline metrics for grant reporting.

Drill a through-hull hole below the waterline at the stern. Install the bronze through-hull fitting with a screened intake (keeps out seaweed and debris). Run tubing from the intake up to the 2-stage pre-filter assembly (5μm first stage, 1μm second stage). Mount filters in an accessible location for cartridge changes. Seal the through-hull fitting with marine sealant — this is a hull penetration below waterline.

Mount the DC diaphragm pump on vibration-dampening rubber mounts in the equipment bay. Connect the pre-filter output to the pump inlet. Connect the pump outlet to the pressure gauge tee, then to the RO membrane inlets. Wire the pump to the power distribution panel (dedicated fused circuit). Install an on/off switch accessible from the deck.

Mount 2 RO membrane housings horizontally in the equipment bay. Insert membrane elements per manufacturer instructions (check O-ring seals). Connect the pump output to both membrane inlets (parallel feed). Route permeate (fresh water) outputs through a check valve to the 200L storage tank. Route concentrate (brine) outputs overboard through a brine discharge fitting above the waterline.

Turn on the pump. Watch the pressure gauge — it should rise to 600-1000 PSI. Permeate should begin flowing within 30 seconds. Let the system flush for 10 minutes (discard initial permeate — it may have preservative from new membranes). Test permeate with the TDS meter: target under 500 ppm (good membranes produce under 100 ppm). Measure flow rate in litres per hour. Adjust pump pressure to optimize output. Fill the 200L storage tank. Taste the water — it should be fresh and clean.

Systematically inspect every bolt hole, joint, cross-beam connection, and through-hull penetration on the deck. Apply marine sealant to every one. Pay special attention to: deck-to-cross-beam joints, solar canopy post mounts, equipment bay bolt holes, and any cracked or split plywood. Apply 2 coats of marine varnish to all exposed plywood — top, bottom, and cut edges.

Cut polycarbonate panels to cover equipment bays (battery bank, fuse panel, charge controllers, monitoring electronics). Mount on hinges for access. Install aluminium drip edges above each cover — angled to route water sideways and away. Install drain channels below each cover to catch any water that gets past. Seal all mounting screws with sealant.

Identify every low point on the deck where water pools (pour a bucket of water on the deck and watch where it collects). Cut a scupper (drainage slot, 50×100mm) at each low point through the deck edge. Install one-way rubber flaps over each scupper — they open outward when water pushes from the deck side, but close when waves push from the outside. This prevents deck flooding while allowing drainage.

Install stainless eye bolts at 12 strategic locations: near each equipment bay, near hydroponics towers, near each AirGen engine, and at deck corners. Use backing plates on the underside to distribute load. Then apply anti-corrosion spray to ALL exposed metal on the platform: bolts, hinges, mast hardware, cross-beam connections. Wrap stainless cable ends (guy wires) with anti-corrosion tape.

Walk the entire platform with the integration checklist. For every subsystem, verify: (1) Individual test passed. (2) All bolts tight. (3) All electrical connections secure and labeled. (4) All sealant joints intact. (5) No loose tools or materials left on deck. Sign off each item. Do NOT proceed to launch with any unchecked items.

With the platform still on land (stable, accessible): Connect all energy sources to the power bus. Turn on every load simultaneously: desalination pump, hydroponics pump, LED lighting, monitoring. Run for 30 minutes. Monitor: battery voltage (should remain stable), pump operation (no cavitation noises), monitoring display (correct readings). If anything fails, fix it NOW — not on the water.

Move the platform to the water's edge using rollers (100mm PVC pipes under the pontoons). This requires 6+ people pushing and guiding. Choose a gentle slope into the water — a boat ramp is ideal. Verify the launch path is clear of obstacles. Position the platform pontoons on the rollers, perpendicular to the water's edge. Attach ropes to all 4 corners for control during the slide.

EVERYONE puts on life jackets. Slide the platform into the water using ropes for control. Once floating, deploy outriggers immediately (stability). Start the monitoring system. Start the desalination pump. Verify all wave turbines spin (if there are waves). Check for leaks — look under the deck for dripping. Moor the platform at its deployment location. Monitor for 1 full hour before declaring operational.

With the platform floating and all systems running: (1) Fill the 200L fresh water tank — measure TDS (should be under 500 ppm). (2) Record power output from each source. (3) Record battery voltage and state of charge. (4) Check hydroponics pump is circulating. (5) Take photos and video from multiple angles. (6) Write the one-page metrics sheet (litres/day, watts, kg food, bottles recycled, volunteer hours, total cost). (7) Hand the first glass of desalinated water to a community leader. (8) Celebrate — this platform was built from trash by a community, and it works.