Rafts for DWC

[Michelle Silva]

As suggested, I'm adding blog post below to "forum"..still need to learn how best to use this site.Thks.

 

Can anyone advise what the difference is between using Dow blue boards and the white 2" styrofoam at Home Depot. Do the dow blue boards need to be painted? I don't know if I would ever try to be "Certified Organic" but I would want to do what is safest.. Does it make a difference? Thanks.

[TCLynx]

Michelle,
I did notice a smell on the vinyl when I unfolded the billboard liner. I'm not entirely happy about that but I've never really been one to get too uptight about the materials unless they have been known to kill fish (I advise people to be very careful with cheap intex pools and such as they have been known to kill fish unless they are very very very well seasoned.)

Anyway, I'm still trying it out. The pin holes or minor damage only seem to be weeping a little with fresh well water so I've gone ahead and plumbed it into the system.

The bed "framework" is made out of sections of cattle panel. Here is a link to the blog with pictures about it.
Blog with pictures
After it seemed to work ok one section high with gravel and EPDM liner for the duck system, I decided to go ahead and cut up a couple other cattle panels we had on hand. We went two sections high plus spikes to push into the ground. So each section is 49 inches long and once the spikes are in the ground the top edge is about knee high. I wired the sections together and the end ones are bent in so the bed is narrower (about 36-40 inches, not too perfect.) Once the liner was in and filled with water, the sides did bow out so I've cut heavy duty tension wire stays to hold the top together. Will see how it all works. I've got it filled to the appropriate water level and the tension wires are on the top edge and I'll see what it all looks like in the morning.

I don't want to run air lines out there so I'm thinking I'll probably try for some raft method that keeps an air space under the plant support so the water won't need much aeration beyond the spray bar where water enters the bed. The water being sent to the bed is being pumped out of a gravel bed so it is already filtered so solids won't be an issue other than keeping leaves and debris out.

I'm planning to use that same tension wire to make hoops over the bed where I can use old fasion wood cloths pins to secure frost blanket or netting over the plants to keep the leaves and debris out. I had been planning to use thin wall 1/2" pvc but when I saw the tension wire I realized that would probably cost a lot less and be far easier to secure a cover to. The tension wire is under $18 for 170 feet and I can cut what I need while the PVC would be in 10-20 foot lengths so the excess from the hoops would be essentially wasted since it takes 7-8 feet to make an arch of the appropriate size. Will have to see how it all works out.

[David Hart]

Really, how safe is styrofoam for rafts...?

Friday, my buddy introduced me to a guy that use to mix the chemicals for the expanded foam. He worked at a plant in central FL, which closed.

We told him what we wanted to do...When we asked how safe it would be....first, his eyes got real big...and it went down hill from there. One of the chemicals used in the expanded...he said, two drops on your skin, would kill a man. Sorry, I can't remember the chemical's name (?)

He said it 'will leach' into the water. He wasn't impressed with the idea of painting it either. He also said blue dow was just as bad..... :(

When I mentioned some people are getting an organic rating with it in their water, he give me a dirty look, shook his head 'no'...and didn't say a word.

Someone else here, at AP gardening, posted a response from Dow....."I think" they said something like.... they (Dow) hadn't tested it for our purpose. ( sorry, the site is getting so big, it's hard to keep track)

When we asked at Lowes, seeing if they could order 2 inch ( and how costly)... the guy that orders it, was curious what we were going to be doing with it.
He called Dow....the lady he talked to 'mentioned' that they put a fire retardent into the foam. She didn't want to lose a sale, but she wasn't sure if it would be safe, for long term use.

[Two Jay]

In white EPS, expanded polystyrene, the expanding process uses Pentane, check it out on wikipedia, along with steam. Depending on the manufacturer, the purpose of the foam products etc, would depend on if it is going to be toxic to humans, fish, bugs, fungus etc... if at all. Many EPS products made are pretty close to inert.. but I wouldn't eat them. Typically termites and ants love the stuff to live in but do not eat it.

I worked for an EPS manufacturer, recently, for 4 years. Hope this helps.

[Two Jay]

I forgot to add, you can get EPS without modified bead, the modification that helps with fire. It is possible that you could buy directly from some of these plants, most are pretty slow right now. Tell them you want, 2lb virgin EPS without any additives, this will give you a density close to Dow board but without all of the other nasties. Essentially it would be just expanded plastic.

Side note about EPS, it is 100 % recyclable, so take your scraps to a recycling center or check with your local manufacturer.

[Raychel A Watkins]

Aloha from Paradise
Let me add a little story to the termites like to live in it but not eat it. I said that I get these 2in foam coolers from work, well I stack them in a shed in my fish area. Recently my freezer wasn't working right (need to be cleaned). I brought in the coolers to put the food into until I could get the freezer cleaned. There was this one cooler that had a piece of cardboard attached to the top. It looked like it had been eaten up pretty good. You will not believe this but when I opened the cooler somehow a lot of cardboard was inside. All of that cardboard had been riddled by termites. Upon close inspection I noticed these many small holes made through the styrofoam cooler to the inside. There were no other marks on the cooler just holes in the top where they went in to get the cardboard and went back out. None of the 6 other coolers had cardboard in them and they were not touched. Those termites have somekind of homing devise on what they want to eat. Just thought it was pretty funny at the time and very amazing.

[Michelle Silva]

Hi TC,

What did you end up using for your rafts?

TCLynx said:

Ok, here I go on a new experiment!

I now have a big raft bed to experiment with. Well it's not plumbed in yet and I notice the used billboard liner leaks a little where small abrasions or pin holes have damaged it but are for the most part too small to really see. Not sure if it will work long term but I'll try testing it out for a bit, I can always turn it into a bed wicking bed for dirt gardening if I decide the raft method doesn't work for me.

So does anyone know exactly what kind of paint is food safe for the rafts?

I'm going to experiment with a few different possibilities for rafts. The bed is about 36 inches wide so I figure a 32 inch wide raft would be appropriate which is conveniently an 8' long board cut in thirds. (the bed is long enough for six 4' long rafts at that width.)

I'm still a big fan of using rayon mop string wicks in net pots to allow for starting seeds directly in net pots and I've also found that a peat pellet dropped onto the wick in a net pot will stay moist enough to keep a seedling going till it's roots reach down to the water. I've found that the peat pellets stay nicely moist using capillary fabric with an end hanging into a trough of water so this is a great way to start lots of seeds in a small shelf space. I'll be testing other seed starting methods on the capillary fabric as I can.

I do like the idea (in my system since I've got plenty of bio filter and solids filter in my grow beds) of suspending the rafts above the water so that I don't need to add lots of extra aeration to the beds. However, my bed construction won't support too much weight on it's edges or allow for easy sliding of anything resting on those edges so I still need to figure some way to FLOAT the plat supports. I might try a square of sealed up PVC pipes to support a board with holes. I also want to sort out some way to float the rectangle seed trays for growing baby salad mix ans such (this sort of use might be the most useful to me.)

Looking for other creative ideas too.

[TCLynx]

I have three rafts that are 3/4" blue board simply covered with capillary matting where I can set trays to start shoots or peat pellets to start seedlings.  I kinda doubt I'll ever do more of the foam with holes kind of rafts at this rate.

Michelle Silva said:

Hi TC,

What did you end up using for your rafts?

[charles petterson]

Hi there,

I am having the same problem , I have half my system up and running with the regular 2" white foam sheets that I cut into 32" sections to make them easier to carry and painted the top side with water base paint. they look great but after two weeks are begining to get waterlogged and roots are attaching to the undersides . the blue dow sheets sound better as they are a higher density foam and will not waterlog , but I have seen a comment saying that blue board can be toxic ?

I have since found in the FARMTEK catolog a product called HDPE foam advertized as an alternative to polystyrene.

it comes in rolls 5ft wide and 120ft long. for 374.95   item # 109243r  ( sounds to good to be true ) but I will pursue it asap.

charlie( hawaii ) 

[charles petterson]

charles petterson said:

Hi there,

I am having the same problem , I have half my system up and running with the regular 2" white foam sheets that I cut into 32" sections to make them easier to carry and painted the top side with water base paint. they look great but after two weeks are begining to get waterlogged and roots are attaching to the undersides . the blue dow sheets sound better as they are a higher density foam and will not waterlog , but I have seen a comment saying that blue board can be toxic ?

I have since found in the FARMTEK catolog a product called HDPE foam advertized as an alternative to polystyrene.

it comes in rolls 5ft wide and 120ft long. for 374.95   item # 109243r  ( sounds to good to be true ) but I will pursue it asap.

charlie( hawaii ) 

[Greener]

My problem with styrofoam is that it has styrene in it.  Although there are plenty of FDA-approved food-grade styrene products available, look at what studies of styrene have shown (from the plastics guide I think I posted earlier in this discussion):

 

http://www.scribd.com/doc/2513445/plastics-guide :

 

"Styrene can leach from polystyrene plastic.  Styrene is toxic to the brain and nervous system, among workers with longer-term exposures,15,16 but also has been found to adversely affect red blood cells, liver, kidneys and stomach in animal studies.17 "

 

This might not be anything to worry about in AP, but when I see those styrofoam boards breaking down in the water (or hear of roots growing into them), I can't help but think of the studies.

 

I have looked for a while for decent long term alternatives and have seen the HDPE foam you are talking about here: 

http://www.esapco.com/1070/f/p074-075.swf 

 

In the end I thought this material might not support plants bigger than lettuce very well, and maybe even for big lettuce I worried that with just a little sinking, some water could flow over the top leading to nasty algae buildups on the surface of the rafts.  So then I thought if I have to provide support for the rafts, I am better off getting solid HDPE board (the Polymax board from FarmTek) and using the sides of the tank as support for the rafts, keeping the overflow level in the tank a constant ~0.5-1" below the board.  I am not worried about losing the raft bottom bio-area.

 

Let me know if you come to a different conclusion.  I am always interested in hearing of alternatives.

 

[Joseph Orlando]

I dip or paint beeswax onto anything like styrofoam for several reasons.  One, it prevents any flaking of the materials into the system.  Two, it is natural and organic. Three it is tough, holds up well in production systems and adds long life to your floats.  By the way, it is easy to clean.

 

JoeJ

[TCLynx]

Cool idea Joseph.  Was it you or some one else recommended using wax to seal concrete as well.

 

As to using the hdpe to support plants in boards above the raft tanks that actually has an added benefit too, it provides more air contact with the water so the amount of air you will need to bubble into the raft tanks may be reduced.  And I've found using wicks in the net pots can free you from the need to have the water touch the bottoms of the pots as well.