Random prototypes #1

These are some prototypes I’ve built with left-over materials, and discarded and unloved scraps. In this blog, I’ll discuss why and how I built them, and offer suggestions for others seeking to engineer similar things.

Before coming to Butte, the only things I ever really created were costumes and garden beds, so these projects are all suitable for beginners.
I provide summaries of what I did, but I improvised much of it. I think the lesson to take away is to look at what you need, look at what you have, and see if you can make something of that.

In this post I will talk about two projects:
1. Insulated winter worm bin/disguised worm habitat
2. Heated seed bed

In my next blog, I will describe a few simpler projects.

1. Insulated winter worm bin
I used a design listed in Appelhoff’s Worms Eat My Garbage, which was based on a design from Seattle Tilth (http://seattletilth.org/learn/resources-1/compost/WormBinPlans.pdf). The main difference between the two is the way the lids are built.
The design is for a pretty worm bin that can be disguised as a patio bench. I like the idea of showing how something like a worm bin can be attractive and discreet, but I also wanted to create a worm bin that can better protect the critters from our harsh winters. The essential difference between my vermicomposting bin and the one in Appelhoff’s book is that the bottom of it is insulated.
My worm bin is 27”x32½”and that is mainly because the materials I had access to fit those dimensions. I suggest looking at the directions from Seattle Tilth if you don’t have a copy of Appelhoff’s book, but honestly I have no idea how to read a cutting diagram, and what’s going on in the expanded view is lost on me. I just looked at the picture and figured it out from there.
According to Appelhoff, a shallow worm bin is ideal for two reasons: worms feed on the food below the surface so it’s ideal to optimize surface area, and a too-deep bin runs the risk of the bin becoming anaerobic (that is, not enough oxygen and stinky).

Here is an overview of what I did. Anyone with more carpentry experience would do a much more graceful job, but it’s a learning process!

1. Create a box out of 2x4s (that was just the scrap wood that I had—2x6s or even 2x8s would have been easier to use). I made this box by squaring the cut 2x4s (untreated!) and hammering them to corner posts.

2. Next, drill some holes into the sides for oxygen. Appelhoff recommends a row of 1” holes along the top of one side, and the bottom of another. Since I couldn’t find a 1” drill, I did rows of ½” holes along the top and bottom of each side.

3. Once I had a box that was three 2x4s tall, somewhat square, with some worm breathing holes, I built the insulated bottom. To do this, I sandwiched some scrap Styrofoam board between some left over untreated plywood and bolted it all together. Then I made sure it would fit snuggly into the base of the box by setting the box on top of the bottom boards and tracing along the inside. Then I took a jigsaw and cut off the excess plywood and Styrofoam. After that I was able to jam the bottom into the box and secure it all with some nails.

4. I decided to paint the outside of the box with some paint I found in the shop and treat the inside with linseed oil. I wouldn’t use anything else in the inside, though, because I would worry about chemical off-gassing.

5. Next, I cut some ½” hardware cloth and secured it to the center of the bin. This is a technique to make vermicompost easier to harvest—build the compost up in one side of the bin. When it’s all worked through, build new compost on the other side and the worms will follow the food, leaving you their fertile poop.
6. After that I built the lid, which turned out to be the most difficult part of this project. I cut some 2x4s to make a lid frame that would hang over the edge of the bin by about 2”. Then I measured 3 ½” from each end of the 2x4s, set my skill saw to about ¾” (half the width of a 2x4) and made a bunch of incisions from the end to the 3 ½ mark. Using a wood chisel, I knocked the remaining wood out. This is apparently called a lap joint (I had to look up lots of diagrams). Then I attached the 2x4s, centered a piece of plywood that I had measured out to the same size of my bin, and attached it with a series of screws.

7. After that, the lid was sanded and received a nice coat of paint.
8. Next, I attached the lid to the bin with some old door hinges (that I knew would support the weight).

9. Lastly, I screwed in some hook screws and used nylon rope to make sure that the lid wouldn’t flop off.

Voila—it’s a pretty worm bin!

–its final resting place next to my trashcan composter (next post). Can’t you just see it as a little patio table or something? Next time I’ll make a skinnier one and disguise it as a seat. My guests will never know!

Like I said, this could have been less clumsy, but I’m a big advocate of learning from doing, and next time I’ll be better. This is a great option for a homeowner or an organization that is interested in waste reduction and soil building but worried about aesthetics or what people might think if they know there’s a worm habitat in close proximity. It’s also great for this climate because it’s warmer than a plastic bin. Once I find somewhere to live with a patio, I plan on building something like this to set outside.
This bin, had I purchase new materials, would have cost me less than $20. From what I saw online, purchasing worm bins of comparable size (or even smaller!) can cost $50-$100. My wooden bin is about 5 cubic feet, meaning it’ll hold about 37.5 gallons. A plastic 35-gallon bin from Wal-Mart is nearly $50. However, it seems more likely that people will have old plastic bins lying around the house than all the materials needed to make a wooden bin, and putting together a plastic worm bin takes about 10 minutes.
With all the right materials I could have built this in a day or afternoon. Our radial arm saw was having some issues though, and as I’m pretty fond of my fingers, I waited until I could borrow someone’s miter saw, so it took me about a week of intermittent work to finish this. Safety first.

2. Heated seed bed

Rather than purchase a seed mat, I made a raised bed with rope light buried in sand. All materials were either left over from other projects or donated from Ace Hardware (thank you!). I combined these two designs:
Essentially, I built a raised bed with a plywood bottom and lined that with left-over pieces of Styrofoam. Then I caulked everything, sanded, and painted it in a dark green paint that we had left over. With the lights on, the sand is heated up after a day or so.
A 12”X5’ heated seed mat can cost $90, and will fit almost three seed flats. The bed I built is 23”X46”, which will fit four seed flats, and had I paid for the materials, it would have cost me roughly $50. Also, if something breaks I can easily fix it, whereas a heat mat is kaput when it’s kaput.

It took six bags to fill up a raised bed that is 23”x46”x6”. I read somewhere online that a 50-lb bag will fill .5 cubic feet, so that’s about right.
I think that this is practical for a small-scale commercial operation. It’s easy to build, easy to fix, and relatively cheap. I also like that because it’s a contained raised bed I can just put it anywhere–even though this is larger and heavier, I think it’s a more effective use of space.
Now that I’ve talked about how and why I built these things, I’ll keep you updated on how well they actually work.

Posted on: February 9th, 2012