Help Designing a Raft/DWC System

[Raymond D. Lewis]

Hi everybody,

 

My name is Raymond and I'm an electrical engineering student. I live in Puerto Rico, pardon my english.  I'm in my last semester and I'm planning to design a aquaponic farm for commercial purpose.  I have skills and experience in 3D CAD software like Solidworks. I'm new to aquaponics but I have read Silvia's book and a lot of many other resource like Murray's videos. I still consider myself a newbie and I would never try to go commercial before running a personal system for at least a year. In my reasearch I had come to the conclusion that for commercial purposes is best to use a raft or deep water culture system.  The main reason behind this is that it is easier to harvest, no need to deal with the tangled roots on growbed media, and it seems to have a better yield (depending the type of plant, of course).  I'm planning to start my system in the roof of  my house.  In Puerto Rico, houses are made mostly of concrete and they tend to get heated by sun.  Setting up and AP on the roof my help lowering the temperature of the house.  The available space that this roof provides is about 2300 sq. feet. I measure it by myself and draw a 3D Model of the roof.  I know that the basic components of a raft system are the fish tank, a bio filter / clarifier and the raceways or artificial channels were the raft or foam is placed with the plants.  A local company that produce food, specially canned food, give-away to me two 1000 liter / 275 gallon IBC that carried FDA Food Garde glue used to seal food cans.  I'm lacking a biofilter / clarifier and the channels.  There is plenty information on DIY bio-filters / clarifiers but I can't find how to make a proper raceway or artificial channel. The information I found tells me that a good starting point is to build them 4 feet wide and 18 inches deep depending the type of plant. Also I haven't found information about ideal plant spacing for specific plants. Is there book or any other resource that can tell me info about the plant and the necesary spacing?

 

I'm a little bit concern about using PVC plastic material and I will try to design this system using HDPE (High Density Poly-Ethylene). For the moment I dont want to argue or discuss about healthy factor of the PVC plastic because I may change my mind later and use PVC. For now I just want to focus on the design of the raceway / artificial channel. For the moment I found pond liners made of HDPE.  I can make the rectangular structure for the raceway and cover it with this liner. What materials should I use for the supporting structure, wood that can rot, metal that can rust? Also I can make the raceway with HDPE barrels cutted in U shape and connect them with HDPE piping. The benefits are that HDPD barrels will not rot or rust and the round shape of the bottom of the channel will provide better dynamic flow avoiding dead-zones, zones with low flow rate. The draw back with the barrel system is that the witdth of the raceway can not be 4 feet, in fact it will be about 2 feet because this is the length of the barrel's diameter.  I can overcome this by designing the system in a zig-zag format, puttting side by side two lines of 2 feet wide raceways / half barrels, both having different flow direction. Another drawback is that since the cutted half barrel is U shape and not rectangular, the plant planted on the sides will not be provided with a depth of 2 feets. Only the ones planted on the middle will get the full depth of two feets. I might start with tomato plants, Puerto Rico lacks high quality tomato. Most of the tomato we produced is exported. I want to start small and provide tomato to the local market. Should I concern about this depth issue? Which system you guys prefer, rectangular or half barrel?  Do you know a better way of making the raceway / artificial channels?

 

I'm planning to do this system semi-automated. I'm working as an IT Specialist in a busy hotel and don't have much time to monitor myself the starting system. I know this is a critical step to ensure that the system can cycle properly and is not the best way to start but this is how real life works :( . The plan is to  develop a control system that can monitor water temperature, dissolve oxygen, PH, ammonia, nitrite and nitrate.  Also the system will send me a SMS / text message if something goes wrong.  Then I'll be able to log in via my cellphone web browser and manually issue commands, based on the sensor reading, like adding small ammount of buffer to stabilize PH or removing water and refilling it with pure fresh water to lower ammoniun, etc. Also I'll be able to manually feed the fishes remotely watching them through a IP camera and controlling the feeder through my smartphone. The funny thing is that for me it is easier to design and develop this complex automated system than to design and develop the AP itself. LOL.

 

 I really appreciate any suggestion and I'm willing to help anyone with my engineering knowledge. Thank you so much!!!!

[Jon Nose]

make sure you use dry stuff some links

http://search.yahoo.com/search?p=building+with+bamboo&ei=UTF-8&...

Raymond D. Lewis said:

I haven't though about bamboo.  I might be able to get those trees for free.  They are everywhere in Puerto Rico.  Bamboo is still susceptible to get rot and termites. Does anybody here has worked with bamboo?

Not a bad idea. I'll think about it. Thanks.
 
Jon Nose said:

consider using bamboo...?

[Pices]

TC, where do you get "snap clamps" to fit your chain-link top rail?

[TCLynx]

I get the snap clamps wholesale since I sell them.  You can also get them from Flex PVC online, The clamps to fit 1" pvc will fit on the 1 3/8" top rail.

Keep in mind that most people don't plant and harvest the rafts in the system but actually lift the rafts out to a work space for doing the planting and harvesting so having the troughs at waist level isn't really a benefit for working (since you probably want to do the harvesting and planting in the shade anyway but the plants need to be out in the sun for growing.)

constructing with bamboo strongly enough to support a trough of water may be a challenge.

[Raymond D. Lewis]

Well, it seems that bamboo is not a bad idea at all.

 

Bamboo resist termites. This website,http://www.ehow.com/facts_5998058_bamboo-floors-termites.html,states: "During manufacturing, bamboo wood is boiled to remove sugars and starches and  then kiln dried to remove the moisture. Termites do not harm bamboo floors  because these natural sugars and starches are gone".

Unbelievable, bamboo is stronger than steel and concrete. This website, http://www.thedailybeast.com/newsweek/2008/04/12/stronger-than-stee..., states: "Despite its lowly reputation, bamboo may be the strongest stuff on the planet. It has greater tensile strength (or resistance to being pulled apart) than steel, and it withstands compression better than concrete. Both qualities are essential to keeping the plant, which grows to nearly 60 meters but is only as wide at the base as the very top, from falling over. It needs the compression strength to hold up its own weight and tensile strength to bend in the wind without breaking."

 

I think I'll be doing this structure in treated/commercial bamboo.

 

Thanks a lot Jon Nose, for the bamboo idea!!!!!!!!!!!!!!!
 

TCLynx said:

...constructing with bamboo strongly enough to support a trough of water may be a challenge.

[TCLynx]

If you are buying the engineered bamboo products then that is probably fine.  If you are trying to use fresh bamboo to wire together your own framework from natural bamboo culumns that is another story.

I will caution that making a lumber/liner bed using bamboo lumber might not be so termite prone but there is a tendency for bugs and pests to make a nest between the lumber and liner.

[Jon Nose]

add an outside liner you should be fine ... keep you height limited or you will need to support it ..as  tclynx mentioned  you may want to line your outside bamboo to keep it last longer .. please share pics and keep us updated .. :)

[Raymond D. Lewis]

I haved decide to build the frame for the liner by welding steel rods use in contruction. They are very cheap, like $4 for a 1/2" 20ft long.  I can treat them by burning oil on them(sort of black oxide) thus creating an oxide that will protect them.  Then I can paint them to protect them ven more. I remember finding buried in the earth pieces of 1/2" steel rods of 10+ years old. They were rusted but they were still very thick and sturdy.  My climate is very humid like 60%+ and if the steel rods can handle this enviroment under the earth for long periods of times, I beleive that they will do well if properly treated.

I already graduate and start to work as an IT Specialist. This job will help  me gather enough money to start the project. In the meantime I will start to build a small IBC system just to get familiar with aquaponics before I do the commercial setup.  A local company gave me for free 4 IBC 275 Gallon Tanks, 2 for me as stated in the first post and 2 additional for a friend. My friend is going to sell his aparment and he gave them back to me.  So know I own 4 IBC Tanks. I already cut one of em into two pieces, one 26" for a small DWC and the other one close to 13" for Gravel based.  I will start a new thread for this system.  Thanks for the support!!!! :) .

 

[TCLynx]

How would you attach liner to the 1/2" steel rod frame?

[Raymond D. Lewis]

I will make walls and floor for the liner from water proof wood panels or even cheaper concrete fiber panels.

[TCLynx]

Water tends to push out against flat walls and if your liner is just sitting against the sides and not actually attached and held up by the top of the sides you are likely to see issues with sagging and more pushing out against the sides.  I've built beds using liner and wood and if the liner is allowed to push right down tight into the corners, the water pushes out all the more.  If the liner is secured well along the top of the sides, and there is a slight curve at the bottom instead of it being allowed to bulge out then the liner will cause the weight of the water to pull down rather than bulging the sides out.

I make beds where there is just the top edge securing the liner and I don't even bother with the boards.  But you have to figure out some means to secure the liner to the top edge of your frame in a manner that won't rip loose with the constant weight of water and time.