ClearSpan Pro “High Tunnel 1” Construction Summary: April 2014 – November 2014
By JT
Type: 30’ x 100’ ClearSpan Pro Solar Star High Tunnel www.clearspan.com
Full Photo series: www.flickr.com/northslopefarm/hightunnel1
In the 2014 season, NSF purchased two 30’x100’ high tunnels to expand production and season longevity. In this summary, I’m going to lay out our construction methods, talk in layman’s terms about the construction phases, and look into the true cost of the high tunnel including the equipment rentals, labor, and materials.
Looking back at the notes, it was evident that the construction was broken down into six phases. Throughout this summary, I’ll delve into each specific phase in more detail to both provide a record NSF can share with others and for my own learning reinforcement as I oversee the construction of HT1’s twin, HT2.
Phase 1: Map out HT1, confirm dimensions, excavate ground post holes, set ground post holes
The first phase of the HT1 involved what any build calls for: site and design. Siting HT1 was done by MR using his understanding of NSF land contours, solar access, and accessibility to irrigation. After the general location was decided upon, the crew set out to confirm the dimensions of the greenhouse using the 3:4:5 triangle method. This method is as such: any triangle whose sides are in the ratio of 3:4:5 is a right triangle. To properly use this method of measurement, we measured from our first corner post along one edge 3 feet. We marked that measurement. Again from the corner post, we measured along the adjacent edge 4 feet. Finally we measured diagonally across. If the measurement was 5 ft then the triangle is a 3:4:5 right triangle and the corner is ultimately square. We repeated this step for all four corners. Next, we strung the batter boards 3 feet from the construction to maintain permanent line attachments where we could continually confirm, square, and level our measurements. It was critical to have accurate measurements early on as the rest of construction was supported by these measurements.
Here at North Slope Farm, we deal with a subsurface sheet of shale that is impenetrable by hand. In order to excavate the 34 total ground post holes, we first rented a hand hydrologic auger as seen in the picture below.
First attempt at digging post holes
The auger pictured above simply lacked the power to dig out the holes efficiently, so we eventually rented a skid steer with an hydrologic auger attachment and aimed to dig the holes to 3’. Most holes were dug to three feet, but a few holes hit bedrock before the three foot mark. We lived with the results and moved on. After the holes were dug, we filled the base of the holes with concrete and set the ground posts. To make sure each post was plumb, level, and the correct height, we confirmed each of those variables with two East to West string lines and used a level to assure posts were plumb. Once all variables were in check, we added a bit more concrete then back filled the holes with soil.
TH and MR with the rented Skid Steer and auger
Phase 2: Rafter, Rafter Struts, and Purlin Assembly
After setting the 34 posts, the next step is to mount the rafters to the posts. Before we could mount the rafters, we had to first construct them on the ground. All rafter assemblies consisted of four rafter sections joined by a single chevron at the peak.
Rafters assembled & aligned with corresponding posts
Once we put together the rafters on the ground, we then moved on to attach them to the posts with the help of the John Deere bucket.
Mounting a rafter. Note MR adjusting tension of the chevron at ridge.
After lifting a rafter up to the corresponding posts, we aligned the mounting holes and attached the rafter to the post with a bolt into each mounting hole. This is being demonstrated by AM and RM in the photo below.
AM and RM placing bolt to fasten rafter to post.
After the second rafter was in place, we attached the ridge purlin and set the first ridge purlin in place by aligning the pre-drilled holes with the studs of the rafter chevron, and securing the purlin to the rafter using ¼” nuts and washer. The ridge purlins continued to be added as we added more rafters. (During this construction, we waited until all rafters and all ridge purlins were in place before we started to add the support purlins. Looking through the instructions after the fact, we saw that it is best to install all the purlins as the rafters are being installed. For constructing HT2, this point of reference will probably help troubleshoot the stubbornness we experience when attempting to attach the support purlins.)
Raising rafters, attaching ridge purlin, and loosely attaching rafter struts.
To attach the rafter struts, we took a strut and loosely attached it to the ground post flange using the 5/16” fasteners provided. Once loosely attached, we pulled the rafter strut up into position to be aligned with the rafter hole and corresponding hole on the strut. We inserted the bolt through the rafter hole and through the mounting hole on the strut, added a locknut and tightened to secure the strut to the rafter. We would do the same on the opposite side of the high tunnel. It is important to attach the struts before you begin to attach all the purlins. They don’t have to be fully tightened, but having them attached is crucial. In the photo below, AM demonstrating how to loosely attach a rafter strut to the post flange.
AM placing attaching rafter strut to post flange
With the first three rafters assembled, we began to mount the first under purlin and secured it to the rafters using the ¼” x 1” bots and nuts. At some points, a purlin and a rafter are used to attach cable assemblies. To do that, we installed the rafter cable plate between the rafter and under purlin.
Phase 3: Cable Installation and Diagonal Struts
The first step to attaching the cable is to attach the eyebolts to the frame. Next we measured the distance between points A and B and cut one length of cable from the roll to the determined length. It is imperative to account for the turnbuckle and the extra cable needed to install the clamps. After doing that, we created the turnbuckle assembly. To create the turnbuckle assembly, we used the diagram on pg 22 of the instruction manual(see photo below).
Pg22 High Tunnel Construction Document
The assembly uses a combination of thimbled ends, cable clamps, turnbuckle and turnbuckle jaws to create a tensioning cable that ties each rafter to one another to create a seemingly hurricane-proof design. Below, you can see we used the back of a trailer attached to an ATV as our turnbuckle assembly workbench. This works great as the work bench is mobile and moves along with the crew as needed.
Building the Turnbuckle assembly on mobile workbench.
To attach the turnbuckle assembly, open the turnbuckle to its extended position and check to see how it fits from point to point on the frame. From the diagrams on page 22 (here’s a link to the PDF of the instructions) of the instruction booklet, we attached the first cable to the frame in the location the cable was measured and created for. In the first photo below, JT and TH demonstrate how we used the scissor lift to attach cables to the frame.
Using scissor lift to aid cable installation
We repeated this step on all the cables. Finally, when all the cables were attached, we tightened the turnbuckles. It’s important to not over tighten the turnbuckles as you can pull the posts out of plumb. In the photo below, AM is demonstrating how we used a long screwdriver to turn the turnbuckle to tighten it down.
AM tightening turnbuckles with long screwdriver for leverage to turn the buckle.
To attach the diagonal struts for additional support, we used a vise grip to bend each flattened end of the strut to have the ends of the struts flat against the frame when installed. We positioned the diagonal strut in between the end rafter and the interior rafter with the strut bent end nearer to the rafter on the end rafter and the other end near the bottom of the post on the interior rafter post. Think “diagonal” strut if that sounds confusing! We mounted the struts by drilling holes then inserting bolts with washers through the mounting holes.
Phase 4: Frame Check, Poly Latch U-Channel on End Ridge, Attach Ribbon Board & Double Poly Latch U-Channel to Sides
Before moving forward from here, we made sure all frame members were properly secured, that all bolts and screws were tight, and to cover up any sharp edges or fasteners, we cut 12” pieces of repair tape and taped the tops of all interior rafters to protect the plastic. We also cut 4” strips of tape and taped over each rafter splice. To install the Poly Latch U-Channel on the end ridge, from the peak, we attached u-channel to top of rafter every 12”. We made sure to cut the last section flush to the bottom end of the rafter.
Utilizing the scissor lift to attach channel lock to rafters
To attach the ribbon board to the base of the rafters, we used 5/16”x5” carriage bolts. We had to countersink the bolts because the ribbon board we used was thick (a bit wider than 2”). We installed all the carriage bolts then tightened them at the end. We used self-tapping screws and carriage bolts to attach the double poly latch u-channel.
Ribbon board.
RM's flexing muscles and the mounted, double H-channel on ribbon board
Phase 5: Cover Frame with Plastic and Secure
We woke early in the middle of the season with all hands on deck to get the plastic over the frame. We started out by tying ropes to one end of the plastic and throwing the ropes over the HT until we stood on the other side with the rope over the ridge of the HT and attached to the plastic on the ground. All we had to do was pull together, right? Wrong. Heave, ho! We gave it our all, but it proved too heavy and difficult! We stood confounded, MR running up and down the HT trying to push the plastic up into the air with a broom or piece of wood. In the end, we started to flap the plastic up and down – creating the “billowing” effect – which allowed the air to get under the plastic and there it came over the ridge and down to the other side. Success!
Pulling plastic over frame
Crew securing plastic on humid morning
We secured the plastic on the ridge first. We used the JD bucket to access the peak of the HT. From the peak of West end, we wiggle wired to lock the plastic into the channel.
Wiggle wire through H-Channel
Next we secured the opposite end. One person wiggled while the other tried to hold the plastic taut to create tension.
Securing Plastic
Thirdly, we locked in one long side with wiggle wire to create tension for the opposite long side. On the opposite side, JT, TH, AM, and RM worked together: two persons held the plastic taut while one applied the wiggle wire and the other one drove our mobile scaffold (the ATV and trailer). We then cut the excess plastic.
All hands on deck.
Casey & Colleen enjoying morning of securing plastic to HT1
Phase 6: Baseboards & Roll-up Sides
To attach the baseboards, we established the layout, trimmed the boards to length, drilled holes, and then used u-bolts to attach the boards to the posts. To date, we have yet to set up the roll-up sides.
CH with a big smile! Setting baseboards is fun!
Crew measuring out length for next baseboard
Phase 7: Endwalls
To build the endwalls, we started by measuring out the holes for upright posts. Once measured out, we dug the holes, added concrete then set the posts to plumb and level. We backfilled the holes with more concrete and soil we dug up from the holes. Then we set the horizontal cross bracing. After the cross bracing, we started to attach the polycarbonate paneling.
Master carpenter, and friend of the farm, Ric Stang oversaw JT, RM, and TH as we cut and pieced the paneling together. We had to open the H-channel with the hammer on some of the pieces as the paneling had to enter the h-channel from both the top and the side. We also tried a soap mixture to create some lubrication. Paneling was set by self tapping screws and washers. We had to cut the excess paneling around the end walls to fit it flush to the frame. We used a box cutter to lightly score the polycarbonate, then repeated the light scoring until the poly could be bent. After it folded back, we would be able to bend it back and forth until the piece we wanted cut came off. This was very effective.
MR conducting the orchestra.
Setting endwall panels
NSF High Tunnel #1 True Cost:
In hopes of determining the true cost of purchasing and constructing HT #1, we’ve gone back to the receipts and notes to add up the numbers. At first glance, the high tunnel materials (frame & endwalls) were 75% of the total cost. Equipment rentals tallied 8% of the total cost, worker wages was in at 8%, and additional materials cost 8%. Overall, the numbers below tell us that the true cost, albeit high, is justified with the majority of the capital spent on physical infrastructure, equipment necessary to complete tasks (efficiently and safely) and worker hours. To see it through as a profitable investment, we will have to continue to record data regarding the harvests recorded in HT1.
| Equipment Rentals | |
| Skidsteer & Auger (fuscorentalworld.com) | 971.00 |
| Scissor Lift (fuscorentalworld.com) | 565.65 |
| Supplies | |
| Endwall concrete (wamsnj.com) | 138.39 |
| Concrete for Post Holes (wamsnj.com) | 240.00 |
| 70 U-Bolts (http://www.finkles.com) | 354.96 |
| Ribbon Boards (Sweet Sourland Farm) | 466.50 |
| Baseboards (Sweet Sourland Farm) | 345.00 |
| Finkles misc. (finkles.com) | 84.59 |
| Drill bits (finkles.com) | 102.56 |
| Endwalls (Growersupply.com) | 6,944.81 |
| 30’x100’ High Tunnel | 8,220.00 |
| Worker wages (approximate) | 1,700.00 |
| Total: | $20,123 |
Beau Young
2nd Year Focus Summary – 2013
Intent: As my second year focus I chose the Greenhouse Element because it seems to me that it is the foundation of everything that springs forth during the farm season and therefore the management thereof is essential to an efficient and productive year. While there is an obvious standard operating procedure for greenhouse duties, my initial observation is that none of it has been converted into the form of a manual, or written record. My intent is to document the procedures and processes of greenhouse management on North Slope Farm that have been implemented for years and have stood the test of time in order to facilitate the educational process for trainees to be able to reference and at the same time help me to acquire and increase my own personal knowledge of the element which prior to this year was lacking.
Task and Responsibilities:
Heated Greenhouse
This structure held all our seedling successions for the farm and for sale. There was very bad aphid infestation, noticed in late March, and became full-blown a month later. An OMRI-approved insecticidal soap, M-Pede, was bought and used according to the directions (except we found the hard way that certain flowers should not be sprayed).
Hoop-house
It’s the structure that transitions the seedlings from the heated greenhouse to the outdoor hardening-off tables. Plans to take down and re-purpose this structure began last season.
The Farmhouse Gothic
Beds were prepped for the first succession of market flowers in late March 2012. Sunflowers, zinnias were among the flowers grown in this greenhouse in the spring. In August, the flowers were removed to make way for a late planting of tomatoes. They also received a minimal amount of tending and blight soon got them. Then Hurricane Sandy blew off the plastic covers. It will be replaced in March 2013.
Ralph’s House
This greenhouse was home to kale and chard during the winter of 2011. Late April 2012, some of those plants were taken out due to an aphid infestation. Peas were then transplanted a little while later and were followed by a direct seeding of radishes. By mid May the chard that had remained had bolted and then removed. Rows and pathways in this greenhouse got a weeding and mulching in mid May as well. A week into June, most beds were emptied and were prepped for tomatoes. They did well for the next few weeks despite aphids and minimal tending in July and August. Early September, blight was discovered on a few tomato plants. The farm manager cut down 1/3 of that bed and covered them well. The tomatoes received a little more tending before Hurricane Sandy. This structure survived the super-storm, however, a week later, another storm with strong winds tore the plastic off. New plastic will also be added this March.
My major focus
Some personal interest goals I set for myself at the beginning of the year included soil testing and experiments with soil fertility. I didn’t get around to the soil tests, but I did the latter by way of making compost tea. Two different types were made by steeping stinging nettle and comfrey in water, and waiting two weeks. My memory recalls the results after application being favorable, but better data is required.
Seedling sales
I attempted to increase seedling sales this year. After going over last year’s notes (2011), I reduced the varieties of seedlings offered for sale and upped production on those varieties that seemed popular. What resulted was a more streamlined set of seedlings being offered. Varieties mostly consisted of tomatoes, beets, chard, kale, peppers and eggplants. Unfortunately, weather and aphids had it out for the plants and a lack of personal, practical labor and marketing experience decreased the sales. The dates of the sales to the account ranged from April 14 to May 9, 2012, for a total of 5 weeks. During this time period the number plants sold did go up as there were more to offer, but again, since weather aphids, and my own bad judgment decreased the quality of the plants, sales didn’t last. The amount made from sales alone, not counting equipment or labor expenses, was $1456.00. Compared to 2011, when sales totaled $2368.00 (3/21/13 Edit: Wholesale accounts totaled $2573.00 in 2011 according to RC’s post below. I must have overlooked at least one week of sales, or am missing a different account) over the course of 10 weeks, only $272.00 more was made in half the time (in 2012) as a result of having more plants available (3/21/13 Edit: Nope). So, technically the attempt was a success (3/21/13 Edit: False), but expenses, equipment, stress and the time it takes away from other areas, makes this project I personally wouldn’t try again.
CONCLUSION
Tend the plants everyday!
Greenhouse Element Introduction
Written by: Rita
Date: 4/12/12
Intent: To continue the management practices of greenhouse productions at North Slope Farm.
Parameters: As a certified organic farm, we operate under organic standards and procedures from NOFA New Jersey as well as the USDA. To uphold these organization’s requirements for organic certification, our greenhouse management practices do fit within their standards. In addition those standards, there are more greenhouse management responsibilities implemented by the farm. Both requirements will be outlined below, starting with certification standards, followed by farm greenhouse management responsibilities.
Certification Standards include:
Greenhouse Structures
Materials, Potting Mixes and Applied Substances
Farm GH Management Responsibilities include:
THIRD YEAR FOCUS- Greenhouse Manager
Prepared 12/6/11 by RC
This year was my second year serving as greenhouse manager at North Slope Farm. It gave me an opportunity to try to maximize efficiency within our greenhouses. I was able to practice my management skills to perfect, to the best of my abilities, the routines of the greenhouse production. Dealing with two hoop houses, the Farmhouse Gothic and Ralph’s House as well as one heated greenhouse, used primarily for seedlings, gives an opportunity to manage over many different projects in a season. This year was no different; we had a wide variety of activities occurring throughout the year.
The Farmhouse Gothic had been designated to tomato growing. Our crop care manager was set on furthering his and North Slope’s experience with grafted tomatoes so he took the reins of the hoop house and grew towering tomato plants of heirloom and red slicing varieties. After the tomatoes completion, the Farmhouse Gothic held radishes and attempts at late summer squash which were cleared out to house layer chickens over the winter. This gives the girls a nice protected spot to roam over the winter months. As snow accumulates outside the chickens will be able to walk on the ground and scratch up bugs and dirt.
Ralph’s House, the other hoop house, had an early start to the spring with plants of kale, swiss chard, scallions and fennel that had been transplanted the previous fall. During the summer Ralph’s House primarily held pole beans, including a very cool variety called yard-long beans. These beans were not quite a ‘yard’ long but more like a foot and a half and quite tasty. Now as fall sets in Ralph’s House has been converted to a winter green haven, full of kale, swiss chard, radishes and peas for tasty treats for farmers and the local Hopewell market that goes year round every Wednesday afternoon (2-6) at the Hopewell train station.
My major focus as greenhouse manager was on the heated seedling greenhouse. Planning out a constant healthy flow of seedlings is always a challenge. One can always plan out a detailed step by step run down of what happens when and in what amounts but weather, animals and poor germination can always throw any well thought out plan off. Of course, as in any year we faced all these problems. To start the general plan for the farm was to start early and hopefully get plants growing out in the field in early April. This ambitious goal faced many challenges. The seedlings in the greenhouse faced the dangers of rodent attacks. Despite seedlings being positioned high up on germinating tables, these savory fresh green sprouts attracted constant attention from rodents and other pests in the cold month of March. When most other food sources were gone during this cold month, the heated greenhouse seemed to become a haven for pests who liked to chomp away at our tender young plants. Even after setting traps, covering trays with remay and setting in place mouse guards (slick sheets of metal that the rodents can not climb) around table legs we still had a lot of seedling loss from rodents, especially of our squash plants which had to be reseeded many times.
Additionally, at the beginning of the year we found the weather outdoors to be challenging. The spring was wet (as most springs are) but our fields did not start to drain until well into April, far past our goals for planting. The wet spring caused similar issues on other farms in the area, impeding many farmer’s starting dates but with our clay soil and slow draining fields it became quite a nuisance. As a result of the rainy weather, much of the first succession of seedlings planted for the field never made it beyond the germination tables. Instead, the second succession of seedlings became the first set to touch ground. Yet even the second set had to be transplanted in our big garden beds which are better draining beds then our traditional field beds and do not need tractors to cultivate them. These garden beds are usually reserved for direct transplanting of salad, arugula, tat soi, carrots, radishes and turnips. However, they were very useful for transplanting our second succession while we waited for the traditional field beds to dry enough for tractors to prepare for planting.
In a sort of mirror image of the spring, the fall also brought some devastating rains. The floods of hurricane Irene and later storms brought similar wet conditions to our fall fields as we experienced in early spring. Once again our field production was halted, with mud pits were field beds once laid, transplanting a final succession was again thrown off course. Instead a later set of seedlings needed to be seeded, after our initial crop plan would have ended. These seedlings were transplanted again into the well draining big garden beds. These experiences come to show that again and again plans have to be revised to suit environmental issues and dilemmas; one always has to prepare for the worse. Also, these experiences point to the validity of having different growing conditions to be utilized when necessary. In our case the two different types of field beds allowed us to make use of seedlings that else wise would have gone to waste. It seems a good idea of any farm to have a wetter and dryer field option to help combat bad weather throughout the year.
Seedling sales are the other major aspect of greenhouse management. In the germination greenhouse we grow seedlings for special orders and for selling at markets. This year I planned out numerous successions of seedlings for sale to hopefully keep them young and vibrant. If they live in a pot too long they can get diseased and worn down and their roots can get bound and not transplanted easily. Though we use cow pots, which allow the roots to grow threw the manure based pot walls, which help reduce damage to the plants, they still do need to be planted in the grown to be fully healthy plant. Therefore we seeded a number of successions of plants, which seemed to help keep our seedlings in good shape. With special wholesale orders to places like Whole Earth in Princeton and The Kitchen Garden we were able to make extra money at the start of the year before our crop plants took off. Also, when we look at the work the greenhouse did strictly for North Slope Farm, providing seedlings for the season, we can consider the flats grown for NSF as a distinct “seedling order”. In this way we can evaluate the value of the functioning greenhouse in money earned and saved by growing seedlings.
This 2011 season faired reasonably for the seedling market.
Seedling Summary
Wholesale Accounts: yielded $2,573 gross
Farmer Markets: yielded $2000 gross
NSF total #s : cowpots- 1961 pots (approx $3922 worth)
: trays- 539 trays (approx $5,390 worth)
When looking at the overall products produced in the heated greenhouse and their worth to the farm (in cash and in seedlings for the field) it seems that the heated greenhouse alone stands to bring at least a $14,000 value to the farm.
SUMMARY
The biggest challenge in preparing seedlings for sale is to be able to constantly have healthy seedlings people want. At times one may expect certain varieties to be more popular than others and be surprised by the customer’s lack of interest. However, it seems that one can never have too many sun gold cherry tomatoes, nasturtiums and basil (the three most popular items for wholesale and resale markets). It is key to always keep a constant supply ready for sale each week. Space to store all seedlings for sale and field has to be well managed and all table space, including tables outdoors must be utilized. The greenhouse becomes quite a juggling act in the beginning of the season and many hours are spent watering and caring for these baby plants but if taken care of properly it is quite rewarding to see them grow.
CONCLUSION
The greenhouse has been a great way to plug into the heart of a farm. Being able to adequately plan and organize seedlings has been quite a venture and a wonderful learning experience. It is always a challenge to be able to produce a healthy seedling at its peak, ready to go the moment the weather and field conditions will corporate. Of course, it does not always go as planned and is always a little sad to have to throw unhealthy and old seedlings in the compost pile but when you plant and see a healthy seedling grow into a nutritious bountiful plant, it is quite rewarding. Planning the greenhouse seeding schedule helps to coordinate an entire farm and is a great experience to be taken to future work at another farm or my own one day. Organizing the greenhouse also teaches one patience; you can not rush nature but if you work hard you can hopefully find the best balance to produce the healthiest plants possible.
Greenhouses are here to stay, and in our urban state, it seems likely that the future will include a greater and greater percentage of production in controlled climates. Detail oriented managers will find great success in the greenhouse. It is definately less forgiving than the outside environment. Our greenhouses provide us with the opportunity to produce our seedlings, provide winter shelter for livestock, increasingly we are looking to increase winter production and generally a nice place to be on a sunny December day!