Saturday, March 27, 2010

The Solar Cone Project - How To

I'm going to start at the end of this process, and that's when the cone is in the garden doing its job. Gabe is just about as tall as the finished cone, which is not quite three feet tall. I was amazed at how quickly the cone fogged up once it was placed on the garden and loosely sealed around the bottom with dirt. This cone is currently over the lone Swiss chard plant that by some miracle made it through the winter. It seems to be happy in its new home.

Assembling the four solar cones took an afternoon, and it was an afternoon filled with flying fiberglass. I made it through the process without any splinters, but the fine powder produced by sanding down the edges made me very reluctant to grab the camera, so there aren't any pictures until all the basic cone shapes were cut out. Still, I learned a good deal, and hopefully I can pass on some advice if anyone else out there should try this at home.

Here are all the tools I used in the making of the cones.
  • 1 - .040" X 3' X 24' Sunlite HP
  • 20 - 1/4"-20 x 1/2" Stainless Steel Machine Screws
  • 20 - 1/4"-20 nuts
  • 2 - 20 Tooth Jigsaw Blades
  • 1 - Black Sharpie Marker
  • 1 - 36" Long Metal Ruler
  • 1 - 8" Long Flat Metal File (medium grit)
  • 1 - 4" Long x 1/4" wide triangular file
  • 1 - Tin Snips
  • 1 - Jigsaw
  • 1 - Drill
  • 1 - 1/4 " Drill bit
  • 1 - Pair Safety Goggles
  • 1 - Face Mask (air filter)
  • 1 - Pair of Leather Gloves
  • 1 - Package of Medium Sand Paper
  • 2 - Small Padded Quick Grips
  • 1 - Set of Work clothes that you don't mind getting really full of fiberglass grit
The cones are not cheap, coming in at around $60 each, assuming you already have the tools. Unless they fail to show some big advantages over the control plants, which I doubt will happen, I suspect that they're worth it, because they're said to last twenty-plus years. We shall see.

In the Solar Gardening book the instructions call for a 36" Radius Cone. In the instructions on the website above they call for a 35" cone. Since the material is 36" I saw no reason to cut off and waste an inch. The instructions in the book call for Nylon or Aluminum Machine Screws with nuts. They say use 3/8" machine screws. Great. That's really helpful. Is that length or width? I could only find enough aluminum screws/nuts for one cone so I used Stainless Steel, I'll let you know how it works out. I found using the 1/4"-20 x 1/2" machine screws worked just fine for assembly, and the first cone has already been out for a week with no signs of suffering around the screws from expansion/contraction. Since we've swung from 75 Degrees down to below freezing I think I'm probably safe.

Step 1 - Drawing out the pattern

Since I haven't seen or used a compass since High School I used a nice low tech approach to drawing out the pattern of the first cone on the fiber glass. I used my ruler to measure in 36" from the edge of the roll as my center point and made a mark with my sharpie. Then I measured out the 5" inner radius by placing the edge of my ruler at the mark, and the sharpie tip at 5" and proceeded to slowly spin it in a half circle about an inch at a time. Stopping every inch to make sure the edge of the ruler stayed at the center point. I then did the same thing for the 36" radius outer edge, which took a bit longer but worked out nicely.

I will point out that I was rather paranoid about getting my measurements as near to perfect here as possible, and it turned out that I really didn't need to. When I finished cutting out the first cone the inner half-circle varied between 5 1/2" to 4 3/4" and the outer edge varied by a half an inch, and the world didn't end. I sanded down the edges to a more uniform length, but it was still not perfect and the cones assembled just fine.

The screw hole markings do require a higher level of accuracy, however. I once again used my ruler to measure in about an inch from the edge of the cone and an inch from the base of the cone. Then I worked my way towards the center 7" at a time. At this point you should be ready to start cutting! We're going to use the first cone as a template for the rest.

Step 2 - Cutting out the Cone

At this stage you'll want to make sure that roll of fiberglass is on a non-abrasive surface. I cut it out on my lawn, which seemed to work fine. I used two 4"x4" lengths of wood to raise the part I was cutting off the ground. This stuff scratches easily so if you do this on concrete you'll have lots of marks on your cones.

You can use either the Tin Snips or a Jigsaw to cut out the pattern. They each have their advantages and disadvantages. The Tin Snips are way easier to use, but will fracture the fiberglass along the cut. Since the edge of the Solar cone is going to be underground this probably doesn't matter. The Jigsaw will allow you to cut a fairly smooth edge that will require minimal sanding, but at the same time will vibrate the fiberglass if you don't brace it properly. If I had to do it again I'd probably just use the Tin Snips.

This is a pretty straight forward step. Make sure you have your gloves and safety googles on for either approach and a mask if you're going to use the jigsaw. Then go to town cutting out the pattern.

Step 3 - Drilling the Holes

I used a 1/4" wood drill bit. There may be better drill bits to use, but this worked fine for me. The best advice I can give here is do not push down on the drill at all. Set the bit in place and use the weight of the drill to press down on the fiberglass. I ran the drill at medium to high speed and it would take around 30 seconds to drill through a fairly smooth hole. The first hole I pressed down and made it through in a second, and had crazy jagged edges and spidering around the hole. Just keep going through all ten holes until your done.

Step 4 - Sanding

Ugh. I hated this part. I would definitely suggest a mask for this one. Since I had some pretty wide variance after cutting out the first pattern with the jigsaw (oh how I wish I had tried tin snips first) I used a metal file to grind down to my sharpie line on places where I was far off. After that I moved to the sand paper to smooth out all the edges. I tried using a block of wood to start, but in the end I just folded over the sand paper and ran it along the edges. This smoothed out both side at once and made quick work of the task. You're not looking for baby bottom smooth here, you're looking to get rid of any snags that might cause splinters. Ouch.

After the edges are done you'll need to smooth out the holes. I used a pencil thin triangular metal file for this part. If I had a narrow round one I imagine it would work better. By placing the file in the hole and spinning the edges would smooth out fairly quickly. In a few cases I needed to use the sharp edge to gets some nasty snags filed down.

Step 5 - Test Assembly

At this point you will be covered in fiberglass dust and if you're anything like me, ready to just cut out the rest and be done with it. I highly suggest you try assembling your first cone before you use it as a template. This will help you ensure your screw holes line up.

The first screw is fairly easy, just roll up the far edges and put the screw through. I positioned the screw head outward, but you could orient it either way. It is also slightly easier if you push the screw through the first layer before trying to get through the second. Then place the nut on the other side and tighten it just enough that the two parts being connected by the screw can rotate freely.

When you go to lineup the second screw hole you'll be facing the hardest part of the assembly. I ended up placing the cone upright and bringing the two holes together. Then I punched the screw through and with my left hand I kept pressure on it. Then I reached through the top opening and screwed the nut on loosely. The first time I tried this I did not use this approach and wrestled with the cone for ten minutes before I got the nut on.

With the second screw in you should be able to insert screws into the rest of the holes fairly easily. That is, if the screw holes line up correctly. In my case some of them were a bit off. In these cases I used the narrow file to expand the holes slightly until the matched. I had to do this for the top hole on all of my cones. Nanometer precise I am not.

If this were your final assembly I'd suggest using a wrench to tighten the nuts up. This may cause minor spidering if the holes aren't well aligned. I did not put any pressure on the screw as I tightened the nuts, and once they started spinning I let them be.

Step 6 - Template Time!

At this point you get to disassemble the first cone and use it as a template to mark out your other cones. I used the two quick grips to hold the template in place as I drew out the sharpie outline. Make sure you mark all of your holes. I managed to miss one on two of the cones. Since you've cut out a cone shape you'll spin your template around 180 as you work your way down the piece of fiberglass.

Once you have all your templates drawn you get to go back to step 2 and repeat the process for all the others. I did each step for all the remaining cones before moving to the following step and things went smoothly. By the end I was coated in a fine dusting of fiberglass, but it came out of my clothes in the wash.

Now that I've finished assembling the four solar cones they out in the garden warming various patches that will be used for the first experiments. Peas, Beans, and Salad Greens will be my test subjects. I can't wait!


Ben said...

Keep us posted on the Solar Cones. I have had Solar Gardening sitting on my bookshelf for years never having the capital to try it out.

Anonymous said...

Thanks for the details on your construction I would still have to wonder if the advantages of this are not all that more than one would have using an upsidedown 5 gallon bucket..

I have read the book and may construct a solar pod some day.. Please update.