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.

[Greener]

Here's a good overview of plastics and their food 'safety' level:

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

Ernie - do you know if the FarmTek HDPE foam is UV-resistant? I wonder how it would hold up outside in full sun. Do you know how it is to actually work with (e.g. is it solid enough)?

I really like this alternative to painted polystyrene boards..

[Earl ward]

The blue boards are extruded polystyrene a much denser product used for exterior purposes. The most common use is for basement applications in the ground and above grade as a thermal barrier. I’m not saying it will never break down but it will take a long time. The white is for interior useGreener said:

I saw that video too. I suppose untreated wood could work, though it would probably develop algae and could break down quickly.

What about floating a hard, food-grade, UV-resistant HDPE board (with holes cut) floated on capped PVC tubes??

Earl -- how long does DBB last before it starts breaking down (flaking, cracking)? I find it hard to believe that it wouldn't break down quickly, especially unpainted and in the sun. But I have never seen the stuff in person.

[Greener]

Good to know, thanks Earl.

After reading that plastics guide, I think I will stay away from polystyrene (and paint) for the rafts.

Michelle, you might like this: I just came across some UV-resistant, FDA-approved 100% HDPE boards (bright white): http://www.teksupply.com/farm/supplies/ProductDisplay?catalogId=100...

What do you think? Best option so far IMO.

[Earl ward]

it does not float getting it to float with plants on it may be a chore with the added weight. I used it with my indoor system had problems with it getting stuck and water going over top of the board. changed it out to blue board.

Greener said:

Good to know, thanks Earl.

After reading that plastics guide, I think I will stay away from polystyrene (and paint) for the rafts.

Michelle, you might like this: I just came across some UV-resistant, FDA-approved 100% HDPE boards (bright white): http://www.teksupply.com/farm/supplies/ProductDisplay?catalogId=100...

What do you think? Best option so far IMO.

[Greener]

I assume you are talking about the solid HDPE board, not the HDPE foam?

I agree that getting it to float well could be a problem. Seems like there should be a way to get around that though (like using capped PVC tubes as skis?). I will probably end up experimenting with this eventually, unless someone can suggest a better non-styrene option.

Thanks for the info Earl, I appreciate it!

[Earl ward]

yes the solid board

Greener said:

I assume you are talking about the solid HDPE board, not the HDPE foam?

I agree that getting it to float well could be a problem. Seems like there should be a way to get around that though (like using capped PVC tubes as skis?). I will probably end up experimenting with this eventually, unless someone can suggest a better non-styrene option.

Thanks for the info Earl, I appreciate it!

[Michelle Silva]

Those HDPE boards look prohibitively expensive for my system. Is HDPE less toxic? What are the pros to using that besides that they don't crumble.

Earl ward said:

yes the solid board

Greener said:

I assume you are talking about the solid HDPE board, not the HDPE foam?

I agree that getting it to float well could be a problem. Seems like there should be a way to get around that though (like using capped PVC tubes as skis?). I will probably end up experimenting with this eventually, unless someone can suggest a better non-styrene option.

Thanks for the info Earl, I appreciate it!

[ericjf7]

Sorry Earl, The blue board is not meant for exposure to sun, as it soon yellows and turns to a fine dust, accompanied by a powerful vapor, all of which is deadly. Yes it is used underground, where it seems to last indefinitely, also in exterior applications where it will be covered with other materials such as stucco, siding etc., in which case, again, it seems to last forever, likewise in flotation systems for wharfs etc., as long as it is protected from abrasion. For these reasons I would be hesitant to go along with using the blue board, however as a last resort, believe that painting all surfaces, not just the tops, would be one way of protecting it from deteriorating and entering the system - in which case the paint opens up another can of worms. I too was intrigued with the Farmtek HDPE rafting material, although have seen closed cell materials designed for exposure to sun, and will keep chasing down some more info on those - some of the You Tube videos showed this material used extensively in preformed mats

[ericjf7]

Here's three videos, but they appear to use premoulded plastic units, so the search continues.

http://www.youtube.com/watch?v=c2z-IdnIGLE&feature=related

http://www.youtube.com/watch?v=aAx8WES1tnY&feature=related

http://www.youtube.com/watch?v=P7bZMDYinaA&NR=1

[Greener]

you're right Michelle they are expensive.. but I think in the long run they may still be a good deal. They won't degrade (or very slowly if they do) and you will have piece of mind about the plastic. From what I can tell HDPE is the generally the 'safest' plastic to use in a system. See that plastics guide I posted above, it's pretty informative.

like eric said the paint is a whole other can of worms. I would rather spend a little more now and have the chemical piece of mind than have a crumbling mess a year or two down the line.

Michelle Silva said:

Those HDPE boards look prohibitively expensive for my system. Is HDPE less toxic? What are the pros to using that besides that they don't crumble.

[Earl ward]

Curious what are you using in your system

ericjf7 said:

Sorry Earl, The blue board is not meant for exposure to sun, as it soon yellows and turns to a fine dust, accompanied by a powerful vapor, all of which is deadly. Yes it is used underground, where it seems to last indefinitely, also in exterior applications where it will be covered with other materials such as stucco, siding etc., in which case, again, it seems to last forever, likewise in flotation systems for wharfs etc., as long as it is protected from abrasion. For these reasons I would be hesitant to go along with using the blue board, however as a last resort, believe that painting all surfaces, not just the tops, would be one way of protecting it from deteriorating and entering the system - in which case the paint opens up another can of worms. I too was intrigued with the Farmtek HDPE rafting material, although have seen closed cell materials designed for exposure to sun, and will keep chasing down some more info on those - some of the You Tube videos showed this material used extensively in preformed mats

[ericjf7]

Lo Earl, I realize that I may have opened up a sore point, and that we are all interested in doing it the best possible way we can. The only answer I can give as to what I'm using is that I'm in the (intensely studying part) of the planning process, much the same as many others who have written in, thrilled with the prospect of doing this, also having a considerable background working with construction materials, and the hazards that various plastics are bringing into our lives .

I also know that I have had scrap pieces of uni-cellular material that was used to cover some large commercial swimming pools at a ski resort, some of which have had direct outside exposure to all kinds of weather for about a ten year period, this includes summer and winter. This is a closed cell material, bright blue in colour, fairly sealed on both surfaces (smooth), and does not appear to be breaking down in any way, very tough material - this is what I am looking for, and thought (know) it was in some of the videos, used as raft material. In waiting for the Auquatic Eco-Systems catalogue, was hoping it would be in there, but don't see it in the electronic version.

While I have the address of the (Minnesota) supplier for billboard tarps, I would be very interested in your feedback on this material, as the most likely scenario with my (planned) system will be (80' long) media beds in trenches with prefab concrete slabs ( 16"x48"x2") making the sides, and a liner, or all concrete, yet to be decided, as I won't get to the site to actually build till later in the year - so far it is only what can be gleaned from the computer. So far I own a tremendous debt of gratitude to all who have contributed to the incredible body of information that is out there, and to the contributors on this site, and am only trying to add my little bit. To this end I can't help but feel that any discussions around the materials used are ultimately very important, particularly as we are striving to produce good food.