My definition of “sustainable” for this project is not having to add extra heat or lighting for the plants to grow, The other electricity for the pumps and automation is an integrated part of the greenhouse Aquaponics system and I classify that as part of the normal functions. ;-)
I still have peppers, tomatoes, and lettuce growing which should survive for the winter. Of course the cost to keep these plants alive will now skyrocket in electricity costs, but it’s still a nice treat to get a few fresh veggies during the winter.
Already looking forward for spring!
Hello everyone.
One of the top requests I get is how to build a strawberry tower. This video will display all the necessary steps to build your own.
The first step is to place a mark on each end of the pipe, then rotate it 180 degrees and mark the other end. Then snap a line down the entire length of the pipe. You could also use a straight edge to mark a line, but I find the chalk line to be more accurate and easier. Turn the pipe over and snap a second line down the opposite side.
Along each chalk line you will place a series of marks. Starting at 2 inches, draw a mark every 8 inches. This will be the spacing between each pocket in the tower. If you are going to grow plants that need more root area, set the spaces further apart. I typically replace the strawberry plants every season. If they grow for more than one season, they can become root-bound.
Starting at the first set of marks, draw a line from one mark and connect it to the mark on the opposite side. Then turn the pipe 180 degrees and connect the next series of marks. Continue rotating the pipe while connecting each series of marks. These lines will be used for cutting the slots in the tower.
Along each cut mark, carefully cut through the pipe until you reach the measured mark you placed at the chalk line. Do not cut through more than half the pipe! Rotate the pipe 180 degrees and cut the next slot. When you are done, each slot should be on the opposite side of the previous slot.
Time for some good gloves. The pipe doesn’t become flexible until it is well above the boiling temperature of water. Please be careful!
The general area that will be heated will be an arch shape starting at one end of the slit, up about 8 inches to the back side of the neighboring slit and then back down to the other end of the slit.
Heating PVC should be done in a well vented area. If you overheat it, it can release some nasty gases. Please be careful! Continuously move the heat around the arched area. Try to avoid heating the area below the slit to keep the pipe from bending too much.
After a few minutes, the PVC will become soft. It helps to apply a little extra heat at the each edge of the slit since this is where the sharpest bend will be.
Push in the PVC so it makes a concave shape in the arched area. You will want to push it in enough so that it will touch against the back wall, but not create a seal since the water will need to trickle through that area, but don’t leave too big of a gap so your growing media will fall through it. When you let go of the pipe, it will usually spring back a little, leaving a gap around ¼”.
I found it to be very helpful to use a few spring-clamps to hold the tight bends in place while the plastic is cooling. You will want to hold the shape in place for a couple of minutes while it is cooling.
It takes me about 3 1/2 minutes to completly create each pocket.
When you are done, you will have some nice pockets alternating on each side of your new tower.
As the water flows through the tower, the surface tension in the water can cause it to flip out of the edge of the slit. To correct this, I added a collar around each pocket.
With some extra pipe, cut some rings about 1 ½” wide. Then remove enough of the ring so when it’s placed over the slit area, it extends just beyond the slit. Add some silicone adhesive and clamp the ring in place. Half of the ring should be placed above the slit line. Use clamps to hold it in place until it cures.
If you’re not going to be draining directly into a sump tank, you’ll need a way to catch the water from your towers. Take a 4” cap and add a fitting to it. Drill a 7/8” hole and thread it with a ¾” tap. There are several ways of adding fittings, but I found this to be very cost effective method.
Take a ¾” NPT to barbed fitting and screw it into the tap. If it is screwed in far enough, it will be higher than the base of the cap. This work well to help any media that as fallen through from going down the drain and clogging it.
This cross-section shows how the fitting is placed into the cap.
Place the cap on the bottom of the tower. The bottom pocket should not be filled with anything so you can clean the base cap if necessary.
To hang your tower, drill a couple of holes on both sides near the top and insert some S hooks. Use a wire or chain to hang it from a strong support.
To connect the tower drains together, you can attach them with tubing and barbed fittings. I made some stands from scrap 3” pipe to support the bottom of the tower. Then I used a 1-1/2” pipe with holes drilled in the side to catch the water from each tower. Each pipe then drained into the main sump tank.
Filling each pocket can be a challenge so I made a tray-type funnel to speed up the process. Take a section of pipe and do a cut down its length. Heat the entire piece so it can be flattened, then bend up the edges so it forms a V shape.
I created a cross-cut section so you could see the inside of the tower. Please note that this sample is done with black ABS so you could see the various surfaces easier. Each pocket will hold about 5 cups, or 1 liter of growing medium. This is enough space for most shallow root plants like strawberries or lettuce. For my strawberry plants, they will usually get water for 10 minutes every hour and a half.
Thank you for watching. Here’s a quick slideshow of my strawberry towers in action!
The bearing chamber is about 3.5” long and is mostly dead space. The shaft of the auger bit is long and I didn’t feel like turning it down shorter. At the end where the shaft comes out, there is a thrust bearing placed on it to minimize the friction.
The hopper has half of the black pipe cut away to expose the auger. This is 4.5” long and has a metal hopper which holds around 1 cup of pellets. As the auger turns, some pellets get forced into the heating chamber while some just sort of move to the front of the hopper. Between the hopper and heating chamber is ¼” of plywood…to act as a heat insulator to minimize the heat loss through the metal.
The heating chamber has a flange on the end which allows different die plates to be bolted on to the end. Depending on the size of the “hole” in the die, the plastic will extrude at different speeds. For the 1/4” slot, the auger turns at about 18rpm and can produce a ribbon of material at roughly 200 feet/hour.
