Backyard Aquaponics
A place to discuss aquaponics

Once again:

Wow!

Did you ever decide on how you will cap the ends?

Great Job Synapto your our Hero

Yes I have. luckily I waited until after they were cut before making any decision as the pipe walls contracted quite a lot after cutting lengthwise and are now average about 470mm (originally 500mm). I have designed the supports around 470mm so even when they are full of gravel and water they should stay this diameter.

Now I am getting some thick PVC sheet and making a unique half-moon template for each and every end and the PVC glueing and then finally sealing with marine silicone

Is the PVC glue & silicone strong enough to hold that much pressure? A lot of the gravel weight will cancel itself out because it's irregular (same reason peanuts in a can don't all get crushed). The water though will exert a great deal of pressure on the pipe and the end caps. If a half-cylinder is 1/3 full of water the pressure on the surfaces will be:

... does some math....

9.8*length / [ 6000*(r + length) ] N/m^2

hmm, might be fine actually. If r is 0.47, and length is 6, it comes out 0.00151 N/m^2

Ok, never mind

It might be smart to make two ends, glue them up, and then fill the trough with water -- before you go to the trouble of making all of them.

The other thing to consider is that if your growbed flexes at all -- every time the water fills it, it will flex outward and then the gravel will pack into the newly created voids. Each cycle it will "jack" outwards. I had a heavy duty PVC tub break in this way after about 5 month -- perhaps mine wasn't UV treated or was inferior materials....

Good point. Although the whole pipe is braced by the upright poles, maybe I should also brace the ends to stop any movement and then cap them.

Have you thought of "plastic welding" flat ends on? Could weld both the outer-side edge and inner.

Would if I knew how !!

It's a quite simple process , very similiar to metal welding but no sparks:)
I believe a few hours practice and most peoplebecome quite proficient.

Can pick up a quite good quality welder unit for less than US$150.

Here's a u-tube link toget the basics.

http://www.youtube.com/watch?v=dQi-Kbsr_6o

I do plastic welding on my stuff. If took me three tries to get the feel for it. Welding plastic saved me around $70 in PVC fittings on my current AP system. Hint: If you make smoke or plastic is changing colors you are over heating it move faster; tight fits weld very easy; filling in gaps is not such a great idea; use only same type of plastic welding rod as what you are welding; get the welding rod its much easier than using pieces of the pipe you are welding and continuous seems are strong and do not leak. I got my plastic welder from harbor freight for $39, but the first one burned out after a few uses. You also need to have a water separator in the air line to protect the elements if using an electric version.

Here's a couple of different plastic welders....

First one is pretty much like a standard soldering iron ...




This one joins pipe/tubing.....





And this is my favourite.... about $130-$150.......




Kind of opportune that we did plastic welding last friday

Could you cut some 1 inch ... 2-3 cm strips off the end of a spare pipe, so that you have a group of 1/2 moons/c's/u's that width? You could fasten those with screws to the inside of all your pipe/growbed ends, and then set your 1/2 moon ends that your cutting up (inside diameter of your growbed) on the inside of your pipes resting against the strips you cut. That would solve any problem of pressure going out toward the ends.

You would then have a good rest for your growbed ends and I assume (that bad word) lots of glue/silicone surface (2 planes versus 1) that would have the weight (water/gravel) working with you

Not sure if I spoke that correctly. A pic would be better, but you have all the stuff. Hard part would be that all those pieces would have to be cut straight. Might be hard to do with Denzel's saw.

Jmasak

That will definitely work. Thanks, I think I'll give it a try.

RupertofOZ

I'm going to get myself one of those Makita heat guns tomorrow.

The big day dawns. Yep, time to put on the greenhouse film at the commercial site. Having the plastic cover on now means that we can work in any weather but it also means that the temperature inside is at least 5 degrees higher. Rainy days are great but hot days are going to be stifling. The gables (end bits) have been concreted in and we’ll cover them last. Today however, we fitted the main tunnel with plastic.

The greenhouse film comes in 10m widths, so with 5m taken off over our 30m tunnel and with 25m to cover we used three lengths with very generous overlaps. What we did was to start from the one end and clipping it to the gable end and then pulling the plastic as taut as possible. Then repeated at the other side.

The plastic is held down on either side by a trench dug in the soil and then the plastic looped down and filled with soil as follows.

Some images below.