Aluminum and Vinyl Table Top

Thanks boffer for the thought on testing. The nylon seems to be wicking pretty good but a 1/4" cotton rope is doing a better job(left side of jar) I also put in some clothesline and bailing twine for grins. All are wet after 1hr, but the cotton one is dripping away altho I have mixed feelings about cotton from what I've read, so we'll see.

And thanx Marc for chiming in, this is definately an 'in planning/progress' project!



Anyways, while I was testing the ropes, I put together a little prototype *laugh* of what the bottom will look like. The only thing missing in the pics is the wicking material hanging/draped down into the water



I can continue with that way of building it or another thought would be to lower it just to cover the cable and have a couple of inches of water above the metal and a material mostly submerged that would wick the water out. Pea Gravel, etc.



For everyone to get a grasp of the dimensions, this pic shows two pieces snapped together of the metal cut to 1' and a redline placed farther back onto the second piece making 1 square. That gives me roughly 70 already drilled 3/8" diameter holes per sq. ft. I don't really think at this time more holes would do me any good.



I'm most likely going with a cable that I can adjust the temp on like you mentioned boffer and if you have a link, it would be more than appreciated. The cable that is in the pics and would still keep the water from freezing is just a gutter cable that is self regulated that draws juice only when the temp around it's coldest location is below 36 degrees. In other words, the water should never freeze but I can't raise the temp above 36, which would still get things going a little quicker in the spring and later in the fall, but it won't extend a season like controlling the temp would. Who knows, might have one in the water to keep it from freezing and one in the bottom of the soil for temp control. Our first frosty nights are about 6 weeks away and is why I appreciate the input from this forum to kick it around.

I do believe that if I was in a more moderate climate that the simple evaporation of the water upwards through all of those holes would aid in keeping the lower soil somewhat moist as it raises up and a warmed water can't hurt.

Thanks
Brad

The problem with cotton is that the worms eat it and it may be gone within the year, which would both eliminate the wicking and leave holes for soil to leak into. Regular decomposition can get to it too, but that may take more than a year. Kind of a pain with smaller containers, but your wicks regularly disappearing could be a real pain with a big bed like you have.

Re: the gravel idea.  We had a new member last year who wanted to make a wicking box by placing gravel in the tub, covering with weedcloth, and putting MM on top of that.  I read his sources for the idea, but it didn't make much sense to me that the water would wick up the stones.  I did a small experiment to try it out; you can read about it here:
https://squarefoot.forumotion.com/t17000p16-small-wicking-box-experiment

My nylon cord is wicking better than I expected.  To the point that it's dripping onto the desktop.  Funny thing though, the coloring petered out after about 4 inches.

Here's a recent thread about a wicking box using perforated 4" drain pipe that I think is interesting.
https://squarefoot.forumotion.com/t19786-self-watering-sip-sub-irrigated-raised-bed-construction-how-to-build#227674

I like the idea of two heating cables!  

Here's the cables I was referring to.  They don't come cheap, but prices vary a lot.

I was given two 20x48 inch seedling heat mats like this.  I have them buried in a box full of MM, and they did great this spring.  I like them better than cable, but I have no idea how long they'll last.

Marc Iverson wrote:The problem with cotton is that the worms eat it and it may be gone within the year, which would both eliminate the wicking and leave holes for soil to leak into.  Regular decomposition can get to it too, but that may take more than a year.  Kind of a pain with smaller containers, but your wicks regularly disappearing could be a real pain with a big bed like you have.

Yes, whether they disappear from being eaten or by quick decomp, I want at least five years of no maintenance on them. And I'm confident if I get five years out of a heating cable I can afford to change the wicks if needed.

Seems like a polyester wick is a preferred way to go from my last week of reading, but I didn't have any around to test it. Per square, how many many wicks would I need with 7" of soil. Let's say I brought 4 of them 3/8 diameter x 6" long up equally into each square, would that be enough? I can tape off the holes I don't bring wicks up thru and just use the metal for the bottom of the MM. Just another way of trying to make this work.

Brad

boffer wrote:
My nylon cord is wicking better than I expected.  To the point that it's dripping onto the desktop.  Funny thing though, the coloring petered out after about 4 inches.

Here's a recent thread about a wicking box using perforated 4" drain pipe that I think is interesting.
https://squarefoot.forumotion.com/t19786-self-watering-sip-sub-irrigated-raised-bed-construction-how-to-build#227674

I like the idea of two heating cables!  

Here's the cables I was referring to.  They don't come cheap, but prices vary a lot.

I was given two 20x48 inch seedling heat mats like this.  I have them buried in a box full of MM, and they did great this spring.  I like them better than cable, but I have no idea how long they'll last.

We'll nix the gravel idea, see your point.

The thread about the 4" piping is actually the one that really got me looking into coming up with a system, just liking the idea of the resevoir. And thanks for the links as I was pretty sure what you were talking about looking around the last week.

I really don't need heated water during the summer but I would like to extend my season in the box and to do so, well, I need unfrozen water, so I'm leaning towards the two cable to do it right I guess.

As I posed to Marc above another scenario I would also like yours(or anyones) thought on it.

Thanks boffer

If you go with the cables, learn from my mistakes.  Do what the manual says!  The instructions say to attach the cable to ½ inch hardware cloth in order to maintain the spacing, so the cable doesn't cross itself, touching, which creates a hot spot, which melts the insulation, which allows the cable to short out.  

I know this to be true because I duct taped the cable to the box bottom, and the duct tape adhesive failed in the damp environment, which allowed the cable to move...

Also, put the cable on the bottom of the hardware cloth; that will protect it from your trowel.  My taped down cable wasn't protected, so I used wooden spoons or spatulas for a trowel.  They worked OK, but the cheap utensils didn't last long.

Hmmm...wicking material and hardware cloth could be wanting the same space.  I guess the wicking material would fit through the hardware cloth?

I don't have a clue about the number of wicks to have.

Still working on the particulars boffer and will be for a couple of days. Those are pretty much the same things to worry about with gutter cables and such, don't cross them, don't nick them. What ever is decided it'll be with safety in mind and of course wasting any hard earned cash.

My thing with heating the water can be expressed another way. Between my first fall frost on Sept. 23, 2014 to my last one on the 29th of May, 2015 is a total of 245 days. Of those 245, we had 183 nights of freezing or below. I'm sure there's other folks with similar numbers on this forum(or not) so adding two to three weeks on either shoulder of the growing season is pretty big(even if it's only 30 sq. ft) and being able to combine it with some sort of a wicking setup would be great. Prollly just dreaming.... :>)

In the morning I'm going to build a little test box with some wicks coming up and watch it for a couple of days.

Thanks for the feedback

Long story short, I was planning on building a little test square Sunday morning, but got called away to one of the stores I maintain to replace a water heater.

When I got home I threw together a little 1' x 1' wicking box using the nylon as a wick. Inside dimensions are 1' x 1' by 9" high. I took two 2" floor joices if you will and glued them to the sides of the box for the metal to rest on.





Now with the inspector satisfied with the loops of nylon through the floor, I placed them and my fill tube into the base of the box. I filled the box with water before putting the floor in.





Then I set off to make up some MM, using medium vermiculite(all I had), peat moss and home made compost in equal 1/3 parts. By the time I made it back to the box, water was wicking up on all of the ropes. I then filled the box with the mix working it around the ropes as I went. I purposely left the MM dry except for any moisture the compost might have provided. The ropes come up into the mix about 3".



and then topped it off, giving me a square around 7" deep.

I left it sitting on this front step where it gets about 7hrs of sun per day. Monday when I got home from work in the afternoon an inch of the water had risen into the square so I refilled it. Tuesday pm it was down again about an inch but I didn't refill it just to see. Last night when I got home, there was about 1/2 water left in the bottom but didn't refill it. When I get home this afternoon, I'm going to have a little 'dig' into the square to have a feel and look.

Then I'm going to fill it and plant something!

MackerelSky wrote:
Seems like a polyester wick is a preferred way to go from my last week of reading, but I didn't have any around to test it. Per square, how many many wicks would I need with 7" of soil. Let's say I brought 4 of them 3/8 diameter x 6" long up equally into each square, would that be enough? I can tape off the holes I don't bring wicks up thru and just use the metal for the bottom of the MM. Just another way of trying to make this work.

Brad

I have only anecdote rather than science to reply with. I wouldn't worry too much about the height of the soil, as water's attraction to itself can draw it up huge trees molecule by molecule. I'd worry about perfusing the soil with enough wicking area in the first place to get any reasonable amount of water into the soil in the first place. Trees do it with large and extensive root systems; I'd suggest you try the same.

What works in my single self-watering container is a wick several inches in diameter, made of bundled wicks stuffed into a central hole, and four extra wicks halfway between the central one and the edge of the container, arranged as if on the points of a compass. The previous year I had used wicks as recommended, in only the central hole, and it didn't bring enough water up fast enough, I guess, as the soil stayed quite dry and the plant didn't do all that well. This year another tomato I put in the same container is doing much better even though the soil is going on the third year of use in a container, which is hardly first-rate anymore.

In your situation, you have lots of tiny holes. I would fill every one with a wick -- after all, wicks don't need to be long, so the cost wouldn't be enormous -- as a second choice, but my first choice would be to make some of those holes larger at regular intervals of no greater than about a foot. That would be a whole lot more trouble, but would get a greater amount of water into the soil more quickly as it's needed, and to suffuse a box with water as fast as it is losing it in a hot and/or windy summer day seems to be hard to do unless you have a good amount of wicking material in there.

Some people also recommend bringing your wick quite a ways into your soil, as in, all the way to the middle or near the top of your box. It's worth getting the wicks in there a way, but how far you want to drag them up there before they will start to interfere with your planting and cultivating is up to you. My container is deep enough that I could bring the wick up more than four inches.

Others are more experienced than I, so these were just my thoughts via the experiment I conducted over the past couple of years. The gist of it for public consumption is that my results improved when using more and thicker wicks, so that's what I'd recommend.

Looks good! Lots of vermiculite, I noticed, which is always a good thing.

Thanks Marc, your input has been great.

What I found last night digging with my fingers is that I had a solid moisture base at about 4" from the floor, soil that was actually saturated with water and another inch that was damp, so 2" from the top was dry. I also realized that I made a little mistake thru this test without a cap on the fill tube as I believe moisture would just rise naturally out the tube, giving less 'pressure' to the wicks.

In a 7" soil and after germination of the plants, say getting them all to an inch tall or so, I believe there would be enough water in the squares to promote a decent root system, whether it be carrots or lettuce. Probably two good veggies to test it with.

Now my main concern shifts to the 'extra' weight on the frame. Two inches of water in a Sq. Ft. equals around 1.25 gallons, or 10 or so pounds. Times that by 30, well...I weighed this box last night on a bathroom scale and it was about 27 lbs.

We'll just have to see over the next week what the course of action is...

Thanks and All the Best
Brad

Good luck Brad!

I'm not sure what you're referring to when saying that you made some sort of error regarding a cap on the watering tube. What came to mind right away is that you wouldn't want to create any sort of vacuum that would impede water uptake, so that not having a cap on might be the best thing. A bit of screen held on by a rubber-band, say, could keep most critters out.