Aquaponic Gardening

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Raft Bed Saga Part 3

Grrrr, Here is what I found this morning when I cam out to see how the raft bed did filled over night. The Stays didn't, stay that is, they sprung off. I must admit I didn't secured them very well.

The bed was bowing out even wider than before. So I set the pump to draining it to the sump tank. I set the main grow beds to hold water so hopefully I wouldn't loose too much to the sump tank overflowing and I headed to the store for 12 3 foot fence stakes (the green metal ones with the little flanges on the bottom to help keep them from twisting.) and a big heavy post installer thing (Not sure what you call them but I love it, I wish I had gotten one long ago. I'll be pounding in posts all over the place just for the heck of it now!)

So how bout more pictures.

This was the image this morning.


So off to the store I went!
While I was out I found a few more handy tools I wanted. Some Fence pliers, definitely better for bending this heavy wire than the channel lock were.

And when I got back the bed was drained enough to hook up the ratchet straps.


See I knew this whole bowing thing was likely to be a problem. I did want to see how much of a problem before I went and got the stakes, just in case they wouldn't be needed. But showing this process off will hopefully prepare others for the likely hood of such bowing of most any minimally reinforced gravel or water bed.

It also gives me the opportunity to show off favorite tools. Long time favorite are the ratchet straps, I've managed to do all sorts of amazing things with the help of these and here is just one more opportunity. Now see in the background there. That gray pipe with the handles, now that is a new favorite! Pounded in those little 3 foot stakes like cutting through warm butter, well I did have to pull the pounder off and flip it over for the last several inches since I wanted the post below the top edge of the bed. Anyway, far easier to pound in a stake or post with this thing than trying to do it with a sledge (where one is almost as likely to hit themselves as the stake.)



And the stakes are all in



Here we are filled back up. The sides are now angling in a bit even. I've re-installed the stays in a different fashion now so they help hold the top together between the stakes and they also help secure where the fence sections meet. I don't think they can spring off now.


The wire arch bits are standing by to be installed over the stays to hold screen or frost blanket to keep the leaves and crepe myrtle seeds out of the bed.

Now my only worry is that with all the extra work I've now done, I rather want it to work out as a raft bed.
However, this old billboard liner is definitely a bit brittle. Any little abrasion seems to rip the material. I noticed this working along the top edge. I don't really hold much hope for bio-slime being able to stop the seeping and weeping as I noticed one leak that was more like a spray. Will see what I find in the morning.

This experience with handling the PVC liner material does not make me a fan. I know this bit is old (It was free too) but I would hope that liner material would have more than a few year life span. I know the EPDM can last.
If buying liner, I don't think I will pay for any PVC liner material. Free might be one thing but if I'm gonna pay for it, I'll pay for the stuff I know is durable over time and is tough enough to be installed without getting leaks.

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Comment by TCLynx on November 9, 2010 at 8:47pm
Chris, do you have any links for where to get the liner you are using? I like to learn more.
Comment by Chris Smith on November 9, 2010 at 8:40pm
I use a LDPE liner that is food grade. I think that it is 30 mil. It has a fiber core that helps prevent stretch and makes it much stronger.
Comment by TCLynx on November 9, 2010 at 8:10pm
Chris, what kind of liner do you use? Only thing I'm thinking of that might suite such a construction would probably be HDPE. If I do more such beds in the future I may well try your suggestion. (I think the current one is sorted once I get the EPDM liner for it.)

The billboard liner is definitely not strong enough (I could probably rip it with a fingernail) for such a thing and the EPDM would stretch too much.
Comment by Chris Smith on November 9, 2010 at 7:57pm
You are getting lateral water pressure because the liner is tight in the corners of the trough. If you were to leave a belly(or ark) in the liner at the corner points, the water pressure becomes vertical as the water weight pushes down on the belly and transfers the pressure up to the top of the sides. This will only work with a liner that cannot stretch like PVC will. The liner needs to be firmly attached at the top of the side walls to take the vertical pressure. This is the method that I use.
Comment by TCLynx on November 8, 2010 at 8:05pm
Part 4 of the saga and the leak is probably not reasonably repairable. There are many leaks and the material is old enough to be rather fragile.
Comment by Paul Letby on November 7, 2010 at 9:39pm
Very industrious! You certainly don't mess around, the sides look very sturdy now. Hope that leak is repairable.
Comment by TCLynx on November 7, 2010 at 7:30pm
I'm sorry but the links in the Blog post don't seem to be working so I'll re post them here
First of the series
second in the series

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