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barrie2m_

thinner diameter side stakes

Recently I purchased framework from a collapsed Tension Fabric building that would allow me to construct (from good arches) a 30x78 quonset structure (2 3/8" dia. galvanized). The original structure must have just stuck the sides into flat laying 2x6" treated boards with no appreciable sidewall. I want a higher sidewall for clearance. I also have sections from another source that are 2" dia. galvanized pipe that I can cut; some sections will need to have curves straightened if I want to not purchase any pipe. The 2" pipe fits within the 2 3/8" pipe so my plan was to slip 12" of narrower pipe into larger pipe arch limited by tech screws, pound 24" into ground, leaving 36" of 6' side steak exposed.

To date I have less than $300 into the framework but I am concerned that the sidewalls may be where most of the weight is concentrated since most advertised structures list a heavier guage sidewall. Anyone have suggestions of how to tackle this without breaking the bank?

Comments (12)

  • cole_robbie
    11 years ago

    What collapsed it the first time? Snow?

    I know I'm critical, but all I see are problems. What is the original height of the structure? I'm not an engineer, but from what I read about wind load, the calculation becomes significant at a height of 8 feet, and then the force exerted on the building goes up by an exponential factor for every foot higher. So you have to build it a lot stronger to make it a little higher.

    I don't think the gauge of the ground stakes would be as much of an issue as their height. Hoops usually have a spring tension to them; you have to squeeze them together a little to fit them into the stakes. But if yours are six feet off the ground instead of one, that is a long lever to push on. The hoops are going to push the ground stakes outward from the top.

    I think your concept would work, but it would require a lot of internal cross-bracing. You would lose some of the head room you're trying to create. And of course, it would get expensive quickly.

    If you were going to go forward with the idea anyway, I think a cheap way to make it work would be to set all the posts in concrete. I know that's a lot of holes, but with a tractor-mounted drill you could do it in a day. Then the hoops won't push the posts out. You can also put a 4" piece of re-bar sideways through the bottom of the post as you set it in the concrete. I do that for corner posts. They're never going to be pulled out by wind.

    Also, you didn't mention the gauge of the ground post pipe. That is just as important as the diameter. For a 6' post supporting a building like that, you don't want thin pipe. It should be at least a little stronger than your hoops.

    Good luck with everything.

  • barrie2m_(6a, central PA)
    Original Author
    11 years ago

    Thanks for the response information Robbie. I don't know the guage of the pipe in either case but they are both heavier than the galvanived pipe that a local Lowes store has in stock as 2" dia. gate posts. I don't know what caused these to colapse from original owners either since both were auction purchases. The tension fabric building only had 1 kinked arch but the other structure of 2" dia. tubing was kinked at various places- I suspect snow caused the colapse.

    I measured the tentative ht. of the connected arches alone and got 13'. By adding 3' the total ht. would be 16' which is 2.5' higher than anything I have constructed todate. That ht is definitely a concern.

    A few things I am concidering to add support are:
    1. inserting high tensile wire with tensioner on each arch at about 8' ht to pull inward.

    2. insert both solid pipe and tensioned wire windbraces on the end 3 arches.

    3. insert 6 perlins (1" pipe) using cross-connectors.

    4. installing a 2x4" clamped hipboard 4' off the ground on both sides.

    5. installing 2x6' clamped baseboard.

    6. framing ends with 4x6" posts (4 per end)sunk 3' into ground.

    I've never used concrete for a structure but that is something I could do. It just that I've seen many collapsed structures but never heard of one being pulled from the ground. I have a 30x96' gothic structure since 2004 that was a preowned complete structure and I don't think a 100mph wind would budge it but I do insert 2 props at every other arch for the winter snow support. It has more overall integrity than this planned structure.

  • cole_robbie
    11 years ago

    Concrete is most useful for corner posts and end walls. If you had tension wires on the side posts, that might be an easier way to keep the posts from bowing out.

    Clearspan is the company that made the first kit I bought. You can go to farmtek.com and look at their greenhouse designs to get ideas for your own. For big buildings, Clearspan seems to prefer trussed arches. I wish I could make my own, but I don't want to weld galvanized pipe.

    Here is one of their designs of a big structure that isn't trussed arches, but notice the ground posts.

    Here is a link that might be useful: {{gwi:310476}}

  • fruitnut Z7 4500ft SW TX
    11 years ago

    The recommendation for my 32 wide by 54 long by 16 high greenhouse was to set each ground post in concrete 18 inch by 60 inch deep. Since I couldn't dig holes that big I set the posts in a concrete footing about 18 inches wide by 24 inches deep with lots of rebar. When the wind hits 60 mph I'm glad to have 10,000 lbs concrete holding down each side. Over built, yes, but better than under built.

    The concrete isn't so much to keep the posts in the ground but to keep them from twisting. When the frame begins to twist under load collapse is what happens next.

    My ground posts are 3 inch diameter galvanized. I'm not sure of the guage but I'd say about 1/8 to 3/16 inch thick sidewall. If going 2 inch I'd want it 1/4 inch thick.

    This post was edited by fruitnut on Sun, Dec 23, 12 at 23:29

  • cole_robbie
    11 years ago

    The concrete isn't so much to keep the posts in the ground but to keep them from twisting. When the frame begins to twist under load collapse is what happens next.

    That is a really good point. I didn't think of it that way, but you're right. Pictures I've seen of wind-collapsed quonsets show evidence of the end wall twisting like that before the wind pushes it in.

    I also agree that overbuilt is better than under-built. I just finished up an end wall today for a new high tunnel. It's only 18 1/2' wide and 8' high, but still built like a fortress, with five 4x4 posts set in concrete, 2x4 bracing, and a 20' synthetic decking board wrapped over it as the hoop. It's overbuilt, but I think that's ok, especially for end walls.

  • barrie2m_(6a, central PA)
    Original Author
    11 years ago

    If the sides have a 2x4" hipboard running the entire length and the end arches have windbracing wouldn't the chances of twisting be minimized? I just visualize upper mid-sections of the sidewalls bowing out from what Robbie first responded due to snow load even if pipes are cemented in. Then I might have to resort to pulling out all sidewall pipes (including concrete) to redo.

    Both notes are well noted but now I'm thinking that I might be better to fill 2" pipes with concrete after pounding in. My 2" sidewall pipe is likely only 14-16 guage. The problem with concrete filled pipe is that the tech screws may not drill well into concrete for securing clamps that hold the baseboard and hipboard in place. Instructions with my pipe bender (which I'm using to straighten used bows) indicate that prefilling pipe with sand will help to avoid kinking. Maybe I could fill pipes with a dry mortar mix after pounding in in hopes that internal condensation at a later date might strengthen pipe. I remember the supplier-suggested method years ago for installing high-tensile corner fence posts that they be backfilled and tamped with alternating 4" layers of dry concrete mix and gravel. I've never had to dig any up but the moisture to harden that cement could be drawn from the outside contact soil.

    I'm still taking your suggestions to heart and I'm obtaining more prices on 13 guage 2 3/8" pipe that would remedy this situation.

    Thanks to both of you for assistance.

    One added note, Robbie, although not a suggestion to change. I have 4x4" end posts on endwalls of my current 30x96' greenhouse and they are naturally warping enough that now I'm having difficulty with adjacent doors. If there wasn't such a huge difference in treated lumber costs I might even consider 6x6" posts.

  • fruitnut Z7 4500ft SW TX
    11 years ago

    bmoser:

    On a 16ft tall greenhouse you need trusses, under/across, each bow to stiffen the structure and keep the bows from spreading out. Even a cable would help. Mine have a W shaped truss under each bow attaching to a horizontal pipe at 8.5 ft that runs below each bow. This keeps the greenhouse from spreading out.

    You also need bracing to keep the house from twisting. I'm thinking of twisting as viewed from directly overhead. Again cables would help but solid pipes are better.

    I'd also add some center posts to help hold up snow weight. My thought would be a post from ground to center of each bow as pictured in an earlier link of Robbie. This isn't needed if the bows, trusses, and ground stakes are strong enough.

    If I were building mine again I'd go with no taller than 13-14ft, maybe even 12ft. That height is much much easier to work on than 16ft. Are you sure you need the extra height? Every ft of height weakens the structure and makes building and maintaining it much more difficult.

  • cole_robbie
    11 years ago

    I don't know if the 4x4s will still warp over time if I keep them painted. I am more than used to my doors sticking, though. I always make them too tight.

    I just visualize upper mid-sections of the sidewalls bowing out from what Robbie first responded due to snow load even if pipes are cemented in.

    I think the hoops would fail from the snow load before they were able to exert enough pressure on the posts to bow them out. That's what is so hard about designing a structure - it will always fail first at the weakest point, and then everything else you reinforced becomes irrelevant.

    A metal worker friend of mine had mentioned that sand technique. You can use damp sand that is pounded into the tube to compact it. That helps it not kink when you bend it, by spreading out the internal force. But I guess you wouldn't want to seal any moisture inside a pipe permanently, or it would rust from the inside.

    I am intrigued, though, by the idea of internally re-informed tubing, more for building than for bending. What about re-bar on the inside of each hoop? It's cheap, easy to weld, and seems like it would not rust if it was inside a galvanized pipe.

  • barrie2m_(6a, central PA)
    Original Author
    11 years ago

    fruitnut, I really don't need the center height but since I want rollup sides I wanted to create more vertical height on the sides. After studying the arch design more I may reduce the exposed side pipe section to 30" even though I'd like to rollup sides to 48". I also have straightened enough of the 2" diameter pipe that I feel confident that I can cut 28 needed pipes to 6 1/2'(78"). That allows me to go 36" into the ground.

    Robbie, I like the rebar idea but I don't think it is cheap either. I used about a dozen 6' sections of 5/8"rebar when reinforcing corners and near openings of a concrete block wall for a shed I had built and when I went to buy replacements the price was so high that I decided I didn't need them.

    I'm hoping that the 6 perlins will stiffen the structure and minimize twisting. I will buy much of that pipe new at~.80 per ft. since sections I have acquired from damaged structures are severely bent. That pipe alone should cost me $360. I hate to seem so frugal but I wanted this to be less costly b/c I mostly am thinking about planting cherry trees in this thing. Fruitnut maybe you could shed some light on payback.

  • fruitnut Z7 4500ft SW TX
    11 years ago

    bmoser:

    I've spent 8 years trying to figure out how to grow cherries in my greenhouse. The fruit when I've gotten it has been big, beautiful, and 25-32 brix...that's very sweet. But it's the hardest fruit I've grown.

    I think the deal is that after chilling is finished cherries are very sensitive to excessive diurnal variation in temperature. If I run highs in 80s and lows in 30s Jan-March, the flowers mostly go sterile or deformed. So I'm going to run lows in 30s and highs in 60s, no more than 30F diurnal variation, until fruit has set. If it warms and lows get into 40s then I'll go 70s by day.

    I've had good crops when I got it right but apricot, pluot, nectarine, grapes, figs, and blueberry are easier.

    So you will need good ventillation and not get in a hurry to force an early crop if you want to focus on cherries.

    I figure my fruit in general costs about $4 per lb to grow but the cherries would be more than that. I'm only able to sell most fruit at about $2 per lb but have gotten more than that for cherries and blueberry. Thankfully this is just a hobby for me and my costs are high with a fancy greenhouse. But it is the best fruit I've grown by miles and I've been growing outdoors since 1971.

    My most popular fruit is probably the pluot but I think the nectarine, apricot, and figs are better. You might consider figs. Strawberry Verte is a great fig for me with a 5 month harvest and they don't need pollination like cherry, apricot, and pluot. Bumblebees alone are ~$150.

    You might get a 3-4 month harvest in your climate on figs as compared to 4-6 weeks on cherry. I think you could force the figs early at 90 to even 100F by day as long as you avoided freeze damage at night. Also they love the heat so ventillation won't be much of an issue like it would be on cherry.

    This post was edited by fruitnut on Mon, Dec 24, 12 at 23:37

  • cole_robbie
    11 years ago

    fruitnut, what do you think about peaches in a high tunnel? I have seen pictures of the Chinese doing it. It looks like they are growing a columnar peach, but all the columnar varieties I see are not especially early, and my plan would be for an early crop. It could just be the way they trim. I'm thinking I could just grow an early variety like Flaming Fury with a dwarf root stock and train it very carefully on a trellis or stake.

  • fruitnut Z7 4500ft SW TX
    11 years ago

    Robbie:

    I've tried about 20 varieties of peaches in my greenhouse. I've discarded all but two only one of which I really like. Nectarines are better eating IMO. I don't entirely understand what's going on with the peaches. Some of them seemed to breakdown from the inside out.

    I've read about the Chinese greenhouse peaches. They have something like 30,000 hectares of them. Also discussed them with a scientist who visited several times. Their eating quality isn't that good, mostly low to mid teens brix. I'm not happy unless mine are at least upper teens and prefer mid 20s brix. But I like my fruit ultra sweet as do most people IME.

    So peaches will work but there are better fruits as I mentioned above.

    Training is not difficult on any of these fruits I started out at 6ft by 8ft spacing and am now planting at 2-3ft by 8ft. It all works.

    Water is the key to high brix fruit. I only applied 18 inches in the last year. And that's with leaves on the tree from Febr to November. Over water and you'll be in the same brix range as the Chinese...which is probably what they are doing.

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