Time and wind got the best of a neighbor's quonset hay shed and I got some of the curved steel pipe sections thinking of a high tunnel. I've pretty much got the design figured out. Need to yank or dig or burn out stumps, then do levelling and dig down around sides for drainage. (and build the high tunnel)
1) Make it movable
2) Common Sizes
Farmtek economy model 20', 26' & 30' wide x 24', 36', 48', 72', 96' long Farmtek premium model 14', 20', 26', 30' wide x 24', 36', 48', 60', 72', 84', 96' long Most of the above are 12' tall - premium also comes 10' 6" tall for their 14' wide model (from hightunnels.org) What are the typical dimensions of a high tunnel? High tunnel dimensions range from 10-30’ width x 9-12’ height x up to 96’ length
3) 24 pipes/sections
I have 24 sections of pipe that are 10 foot long 5 or 6 foot truss spacing (http://zimmermanshightunnels.com/index.php/pricing/) farmtek is 4 foot for premium - 6 foot for economy
4) Three pipes
Gives me 8 trusses Makes 26' width(unless I do a slight peak in the arch) 5' truss spacing, will make it 35' long 24' x 35' works 3 pipes is 75" tall(deflection), plus 5 foot sides would make it 11' - 3" tall 6 foot sides would make it 12' - 3" tall 5' sides gives 6' headroom at 1' in from sides Smallwood Fence & Pipe near me sells 6' fence posts Maybe 5 foot sides with slight peak in truss as below - will decrease width slightly but 20'-24' width works too Higher peak would help with overheating
5) Truss Style
There's two common truss styles, quonset or gothic(which is really a gable with two flat roof pitches) but I ran across a custom greenhouse builder who actually does some that are more like gothic with a peak and rounded roof pitches so that's what I'll be going with. Might help with snow load which quonsets aren't good for. I'm using three 10' sections of curved pipe so I'll have to notch, bend and weld the center section to form the slight peak. I may even fabricate something to act as a ridge board to give it even more strength and to keep the truss peaks all in a nice straight line. Something like below
6) Here we go
- 3 pipe sections with middle one notched, bent and welded to form a slight peak 24' x 35' = 840 sq ft (840 x 2 = 1680 sq ft since it's movable) Sides are 4' - 6" (that truss might no be built just like that. It was something I did quick. Will have to think on it) Rough Draft
Note to self. Measure how tall you are sitting on the tractor and insert crude likeness into the above drawing.
(less than 50 foot length incurs small panel charge) Sun Master® Pull and Cut Clear Greenhouse Film 6', 10', 20', 28', 36', 40', 48', 56', 64' wide & cut to length Example price - 36' wide is $5.35/ft x 50' long = $267.50 Will have to figure out ends plus top and sides to see what would be best size to order
9) Film Needs
I've been eyeballing this plastic size but have been doing so since the tunnel was a totally different size. However, I like the price and I figured out how to use it. I'll have to cheat on the ends at the corners. It will be several inches shy on the width, as seen in the image above(light blue = film pc), but the corners are already shadowed by a pipe and plastic attachment components. 42x60= $329.00 https://www.bootstrapfarmer.com/products/greenhouse-plastic?variant=8130392260698 Here's how the pieces fit on the 42x60. One side will have to be in two done pieces and maybe I'll just do them both that way. That would give more options for cross flow venting.
It says 32x60 just above but that's a typo, it's actually 42x60. So far I'm at less than $400 between the plastic film and the wheels. I'll still need pipe for the wheels to roll on, pipe for legs and misc steel for attaching the wheel track pipes to something. What? I don't know yet. Something cheap and non-toxic. Wiggle Wire + Channel = over $200.00
Solarize the soil during July/August for the first year, maybe more, to get control of weeds. Run chickens through it first if we have them. They'll till it and kill the grass/weeds. We'll also have kunekune and goats but I don't know which will happen first. I do know the fence is getting done first so we can get these big barking white dogs away from the house. They're keeping us up at night. One's a Great Pyrenees and the other looks to be an Old English Sheepdog mix. We'll see how long his fur gets. If after the fence, we get pigs and goats, I could run the goats through the tunnel spot, then the pigs, then chickens, along with as much compost, garbage and other organic material as I can get a hold of. The goats can eat it down to 4-5" and then the pigs would eat most all the rest of the vegetation and then the chickens can clean up all the crumbs in tiny bugs. All of them will be fertilizing it at the same time. If I can get a hold of restaurant/grocery scraps, I could feed them Karl Hammer style. https://www.youtube.com/watch?v=s8O2tRsfEHM One nice thing about getting animals is the manure. As it stands, I have all the leaves I could ever want and a little kitchen waste but not enough to maintain a pile. I can also get all the sawdust I want.
11) Bed Layout
I have no idea. I do have a small tractor but it's got 24" of clearance between the tires and it's not an ag tractor; more like landscaping/turf so it doesn't have much ground/crop clearance. I could use it to shape 24" wide beds, lay plastic mulch and run drip tube all in one shot. I've thought about making some 2" wheel spacers for the tractor which would give me 28" beds. Those long straight beds are more efficient to put row covers on too.
Great for growing all the same crop
But this is to feed us, not to become market gardeners, although both would be nice. Beds going the other way are interesting but would be more manual labor and harder to design and install a drip system into.
Something about this pic reminds me of M.A.S.H. Looks like they may be using a hose for something and I guess those are boards for walking paths? Here's Eliot Coleman style. Probably a bit much to start with. Pretty intensive and we'd probably get overwhelmed and exasperated. Now that's a water hose.
This one's not bad. I could do without the green grid to trip on and the commercial mulch. Not sure about the lateral walkways. Now that's where a short board or something would come in handy. Good variety and still in long rows basically so some things can be done by machine. Hey look, another water hose. Everything I've read says one benefit of a high tunnel is that by using drip irrigation, there's no more wet foliage which reduces foliar diseases. begs the question, Why does everyone have a water hose? Spot watering?
One thing that bothers me about plastic mulch and drip tape is that they're both too fragile to be reused. That means throwing it away and buying new every year. Might as well shop for shoes at WM and buy tools from HF while I'm at it. Oh wait, I'm building a movable tunnel, make that twice a year. I've read everything about high tunnels I could get my hands on but haven't seen irrigation for movable tunnels addressed. Something else to ponder. We don't have a well yet so I go down the hill to a spring fed creek and fill a small tank that I tow behind the little tractor. Definitely going to have to harvest rainwater off of the tunnel. That would have to be run through a sand filter to use it for drip irrigation. Soaker hoses? PVC with tiny holes drilled in it and cover the PVC with mulch asap so the UV rays don't disintegrate it? Whatever I use, it will be running off an RV water pump at 3gpm and 45psi. Just did some quick window shopping and it comes to $221.00 for a small drip system with programmable timer. That's using the drip tape that's hard to reuse. A 1000' roll has to be purchased and I figure 9 rows 32' long x2 for the tunnel being movable and that comes to 576'. I'll have to see if I can whittle that down to an even 500' or half a roll. 8 rows @ 31' works out to 496'. If I could make that $70 - 1000' roll last 7 years, that would be $10/yr which is cheap enough. The rest of the components are more permanent although some of it is white PVC which will need to be kept shaded. Then in Spring and Fall, there's always the occasional 22 degree night to worry about. That means a tank heater, the main supply line buried and all other components being inside the tunnel with some of it wrapped with pipe insulation(there's my pvc shade) and the rest under floating row covers. Speaking of which.
13) Row Covers
The covering has to be purchased but not necessarily the rest. There's three weights of cover, light, medium and heavy with no thorough explanation as to what the different weights are for. Heavy comes in 500' rolls, light in 50, 500, 1000' and medium in 250' or 500'. My 8 rows at 31' mentioned above to utilize 500' of drip tube was doubled due to the movable tunnel but I don't need to double it for row covers. I'm not messing around with lightweight fabric outdoors in gusty hill country. 8 rows x 31' = 248'. That makes the 250' roll of medium weight the best choice. Even that is $120.00 so I better be gentle with it and make it last for years and years. I'm starting to understand why most growers say they don't increase profits with a tunnel, even though tunnels give nearly double the production of the same area of open field growing.
14) Total Cost
Well we were at $400 for the tunnel film and wheels. I think I'll pass on the $200 wiggle wire and track this time around and figure out a different way to attach it. Here's the drip irrigation components and row cover material.
$400+$341=might as well call it $800 and I still need pipe for legs and something for the legs to attach to and for the tunnel to roll on so we can call it $1000.00 if not a bit more. Not something I'm ready to do this Spring. I'd rather have the perimeter fence first and that's going to cost around $1500.00, plus I can easily spend a year getting a place prepped for the high tunnel. A little earthwork to do, stumps to deal with, trees to cut down for more morning sunlight, soil testing and amendment and some sort of base or foundation for the tunnel to roll on and as a weed and vole block. When/if I run some animals over it, I'll make it a stale bed for a while to get rid of more weeds before the tunnel goes over it.