A new Polytunnel - oh my!

Lurgies ? Really, that is just too scary !!  EEUW, no thanks.

Another nice thing about living under my rock -- no lurgies.

I hope you guys will be well soon.

Peace

Feeling much better thanks both!

Choe explains well why I'm getting a nice polytunnel....



(Thanks again for the link to her videos Deane!)

Isle of Skye!   How neat.  My GGGgrandfather was from there, near Portree.  Question, how high do you have your straight side posts?   In retrospect, if you were to build another hoop house would you make the sidewalls the same height, shorter, or higher?  We are in the process of site preparation for our 20' x 40' high tunnel hoop house.  We are all fairly tall, over 6', and don't want to build anything that will be too short for both our comfort and growing plants.  As we are near Galveston Bay, Texas, the summers get quite warm, a hoop house between 12' and 14' center height is preferred as it will make inside temperature control a lot easier.  We also have high wind issues associated with hurricanes, but this we can build for.  Heat build-up in the summers will be our biggest issue.  Looking forward to your input.  

Thanks,

Cliff. Johnston

Hi Clifford - we are on the opposite side of the island to Portree.

Still bulding my new tunnel! You can see that the sides are tall enough for you to walk right at the edge in this picture:


My husband (on the left) is about 5'10 so I guess the straight sides are about 5 foot. The previous user had paths right round the edges.

My old tunnel was a 14 foot wide one. so the straight lengths of the side hoops were probably 3 feet.
This video from before it lost it's cover gives you an idea of how much space you have - the doorway is more than 6 feet tall and the crop bars are a little above that. This was a 60mph wind, but the tunnel went through 90mph with no issues in previous years.



If you are growing something tall like corn you need extra height. I could only really grow dwarf varieties in my old tunnel - although my new one is much taller. I had a central path with keyhole paths to each side. Having the paths at the edges would have made it a bit more awkward perhaps in that tunnel - mostly because you don't want a fork you are carrying carelessly to go trough your plastic! I think that it is plenty tall enough to stand at the side and not have too much problem, but you wouldn't want to stand right at the edge to work.

So as always it depends! - you can mitigate having less headroom at the edges by the path layout. If you want to stand and work right at the edges then I would suggest at least 4 foot vertical posts for people of your stature, 5 feet probably better. Smaller people like me at just over 5 foot can get away with 3 feet. I hope this helps!

For summer heat, fans and/or roof vents are probably something to consider. I'm going to see how I get on and maybe look at retrofitting some roof vents at a later stage if end windows don't give enough ventilation.

Thanks for the comeback.  Much appreciated.  I was thinking of going with 5' sidewalls, and you have pretty much confirmed that I am on the right track.  We shall drive the posts 3' into the ground.  At one end I shall plant some dwarf citrus trees.  The rest, the majority, will be dwarf papayas and dragon fruit grown in containers as well as some other trellised plants.  Corn is not really a feasible crop for me - too much space for too little yield, in my opinion.  We grew corn 2 years ago - delicious, but we felt that we didn't get that much yield for the space taken.  

Clifford Johnston wrote:Corn is not really a feasible crop for me - too much space for too little yield, in my opinion.  We grew corn 2 years ago - delicious, but we felt that we didn't get that much yield for the space taken.  

Yes, and you can probably grow it outside without needing protection for most of the year

Finally a big step forwards! My husband has been working too hard and hardly had any time to spare for clearing my polytunnel site. Me trying not to nag....

This week I made a breakthrough. I realised that I could (gasp!) pay someone else to clear the site if hubby couldn't manage it. I mentioned this to him, then I gifted him Saturday afternoon (which he normally does in the shop giving me the afternoon off) doing his shift in the shop for him. It was a lovely day - dry and breezy, and he got the majority of the site finally levelled. Today he did the last bit, making a little platform near the door, which will be parking space for my Jiffy vehicle.

So the project is on again! This time I'm hoping to get the frame up and cover on for this winter. There is still a lot of work to do, but with a bit of help with the frame and cover, I think I can manage most of it myself. I've had several neighbours offer help as well, so I may pull in a few favours when the time comes.

In the meantime, I am back to sketching layouts and planning planting lists

Thanks for the pics.  So nice.  

I find it difficult to believe that this project has been 18 months in the making and still not finished! However we are still making progress at the moment, albeit slow.

Having got the site cleared I realised that the anchor posts for the upper side - that had to be cut off the old polytunnel site - were going to be too short for the new location. Since it has been a while, I had a little money saved up again and ordered 8 new anchors (I can cut one of the longer poles in half to make the other two posts. To make the most of the delivery, I also ordered 4 sets of crop bars and associated brackets, and a little more Aluminium box section and brackets. These will enable me to put a high level vent in above the doors at the end of the tunnel, to improve ventilation from the word go.
We borrowed a core drill to make the anchor holes, but again I'm relying on my overworked husband to drill these holes and even he is finding it tough going. Because the holes are vertical, all the dirt and debris stays in the hole and needs clearing out. He found his normal big drill wasn't powerful enough, so bought another cheap big hammer drill. Unfortunately, although a good machine, when it came it turned out that it explicitely said it wasn't for use with core drills.....However we now have the first few holes drilled ready for the first few hoops to go up.

construction site

The idea is that the holes are just a bit bigger than the anchor posts. We're intending to set them in with just a small amount of concrete to glue them to Skye. I think we'll need to shorten the downhill posts just a bit too - these were bolted to the outside of a retaining wall, so were set a lot lower than we will be able to on our site. The way that the hoops have been cut means that the down hill poles need to be shorter than the uphill ones. At the moment they look pretty level.

I've already started to order some plants to go into the tunnel - some more (seedless) grapes, an olive and a pomegranite to go with the one I already have in a pot. I looked for dwarf cherry, apricot and almond, but have decided to leave it till I can actually plant them in the tunnel!

Construction has officially begun!!! The final holes were drilled and I used a minimal amount of cement to glue the anchor posts for all the hoops to Skye.

That is wonderful, Nancy! Hopefully it will grow like a weed!

I've been sorting out all the posts and brackets before construction proper starts and may have found another missing part! I thought that the central support to the end lintels was the same diameter as the hoops, so I could reuse some of the old tunnel brackets there. Unfortunately it seems they are much larger diameter - 60 or 70mm, rather than 45 or 50mm. I don't want to reuse the previous bracket that fixed them to the wooden lintel on the old tunnel as they are long angle iron with a large surface area in contact with the lintel - good if you want to spread the loading into wood, not so good if you are slightly worried about galvanic corrosion and the fixing holes may not be in the right spot anyhow...

Another slight opportunity is one my husband spotted: Due to the depth of the step and the lengths of the anchor poles, the upper poles have turned out to be slightly lower than the lower poles (see image below). He suggested reversing the hoops so that the longer side becomes the uphill side and the shorter side becomes the downhill side. This will mean that we don't have to trim the length on the downhill poles as would otherwise be the case. It would mean that the tunnel could potentially be taller than previously thought - only by a foot or so, which may be a good thing. However, I will have to work out whether the affect on the lintel height will matter: the pole support for the centre of the door lintel might be too short, and I will need to find new poles - or maybe the extra structure with opening vents above the lintel that I am going to put in (which will involve beams connecting to the end hoop) may give enough strength to not need the central support as well....

After the anchor poles, the next step is fixing the base rails in position. This was fairly straightforwards. The bolts to fix the rails to the support brackets needed laying in the inside slots in the rails first. We greased them up with some coppergrease to protect the threads.

laying out support clips and hoop brackets

My husband seemed surprised that I wanted soil in my polytunnel, so the base rails are not along the rock on the lower side, but with a gap of about 18 inches to the ground!

levelling baserails lower side

Initially we fitted the baserail as a complete straight rail along the top side as well as the lower side, but soon realised that left too little pole above the rail for much engagement of the hoops at the Northern end, due to the slope of the rock. So I split the rail back up, and put a step in it as originally planned, using one of the lengths cut from the excess extrusion length from the baserails. Unfortunately the step length didn't match the right angle brackets perfectly (they should have two fixings on each side), so I bodged it by overlapping the brackets. Really the vertical is only to stop the plastic edge from flapping, so doesn't need to be very strong. I'll put a bit of anti-hotspot tape on the corner to stop the plastic tearing there.

step joint in base rail upper side

I'm now planning just to lay the guttering below the rail directly on the gound (supported as neccessary with rocks) rather than fitting it with brackets to some structure below the baserail. Although I do have a bit of UPVC cladding that might do to fix it to, it would need more support behind and it was all getting a bit complex and inelegant, so crude and simple it is! The guttering will feed the water in under the baserail near the joddle in the side rail. I'm hoping to store enough water inside the tunnel to use during dry spells of weather, but normally rely on overflow to automatically water the beds.

Then we had to work out how long to leave the upper hoops. I measured out all the base anchor poles compared to the baserails, the down hill hoops compared to the uphill hoops, the joddle in the upper baserail, and then worked out how much to cut off each tube. I then showed my working to my husband to double check, and he demonstrated again why I fell in love with him by spotting that the critical anchor height side to side was almost identical. So cutting the upper hoops to the same length as the already cutdown hoops for those on the higher step of the upper side, would actually be pretty much perfect. The longer hoops for the lower step just need to be about a foot longer.  

my over-complicated working out summary

I hope he will cut the hoops down tomorrow morning, then I'll lay them out in order, assembled with the correct brackets and with anti-hotspot tape in the afternoon, and then we can have a go at lifting them into position !!!

Poles were cut down, but sorting them out with brackets too a bit longer than expected, as I wanted to grease all the bolt threads again. I also couldn't manage to lift a pair of assembled hoops together to sort them and get the antihotspot tape on, but we had a good afternoon together today on it. First we lifted each pair of hoops onto a flat area supporting the middle a little higher so we could apply the tape without getting tangled in the grass too much. The end hoops have a wider tape as it needs to protect both the top and the end of the plastic. I marked the ends of the hoops as in our case each is matched to a position along the tunnel as each hoop and anchor are slightly different lengths.

hoops assembled with brackets and tape and laid out in order

Then using the digger to support the hoops in the centre, we lifted each pair onto the posts in turn. The first hoop was the trickiest as we (in retrospect) got it wrong. We engaged the lower side first, then found there was not enough flexibility left to push the hoop down onto the upper side anchor post fully, and the angle of the poles didn't match. We were sort of stuck in limbo - we couldn't pull it off and couldn't push it on! In the end we got a lorry tie down strap and that was just long enough to ratchet the hoop in slightly, so that it changed the angle of attack enough for us to pull the hoop down.

ratchetting the pole alignment

The other hoops we engaged the upper side first and were able to spring the lower side more easily as the poles were much longer. So now I have all the hoops in position! The alignment isn't excellent, I have to say. Because all the hoops are slightly different and all the posts slightly different there is a bit of waviness to the hoops along the length of the tunnel. One of the hoops actually wanted to spring off the upper anchorage and had to be fixed with a grub screw. There is also quite a bit of movement in some of the anchors at the lower side where the rock is rather softer. We may want add a bit more concrete there to be sure the tunnel is reasonably firm.

hoops erected viewed from SW corner

Now I'm suspecting that despite double checking the bracket fitment, I may have omitted the end brace brackets on the end hoops - doh! Rather than take the end hoops down again (which I don't think would be easy at the South end!) we'll see if we can redesign the brace so it fits against the lintel rather than the hoops.

The next step is to insert the ridge pole through the bracket at  the very top of the hoops. We may need to adjust the hoops on the anchors at the South end, which is where the misalignment looks most significant. The closer to smooth I can get the shape the better the cover will fit. The weather is not looking too good next week, so there may be a delay in progress....

Exciting! And complicated ..  And I see what you mean about the weather. Hoping you might get a couple of hours at least this coming week, to work on that ridgepole.  

My husband helped me on Sunday (the last nice weather for the foreseeable) to fit the ridgepole. Actually he did almost all the work, whilst I passed tools and moved ladders! It wasn't as bad as it could have been, considering the wonkiness of the hoops. We were able to adjust the hoop heights slightly as we went, so as to smooth out the alignment. This time we remembered to fit the extra brackets for the bracebars. Rather than work up a taller ladder we moved the digger backwards and forwards, and Hubby worked off the roof. The clamps are all now tightened, and extra hotspot tape applied. We needed to fit some grub screws where as one or two of the clamps had badly formed threads. The threads are tapped into the clamps and the thickness of the clamps isn't quite enough to get a good thread engagement.
The next step is starting to build up the end frames - more Aluminium beams. I need to double check the lengths and work out the most efficient way of cutting them so as to maximise the use of the lengths. Because we're not fitting the central brace for the middle of the door lintels, the design is slightly different to the one I calculated the lengths from. I think I will have enough - I just have to be careful.
I've started moving the space wood and door and window frames from the original tunnel to the site so that I can have them handy to repair them and for sizing the frame apertures.

Looks great! I loved putting together my quail aviary, it was like a giant puzzle. I'm now planning a small greenhouse too.

Your progress is so much more exciting as things take shape!

I'm starting to call it my crystal palace!


wikipedia

Apparently, my Mum's mother visited the Crystal Palace in it's final location, as a child, so maybe ten years before it burned down?

More missing parts, poor weather, staff holidays and slightly sick husband all conspiring to slow progress, but another milestone reached today!

The first step was to put the door lintels up - One beam across the full width of the tunnel at either end. It turned out that the braces didn't work from the second hoop to the lintel - the length and angles were all wrong. However I remembered these clips from the old tunnel:

Open tunnel clamps

These are designed to clip onto the hoop after erection - so they got us out of our sticky situation

Slowly making progress: The door posts are going to be buried at the bottom ends, still dangling in a hole at the moment.

End hoop braced and lintel in position

Had to work off a tall ladder to reach the ridge this time for the bracing.

Lintel braced to ridge

Having checked the proposed openers against the South end frame. I realised that the windows would not fit below the lintel to the rock/corner bracket position. I decided that I needed to make another dogleg in the frame and dig out the rock (it was pretty soft there) a bit more. Unfortunately I just couldn't make the brackets I had quite work; I needed one more angle joiner. Plus, for some reason I hopelessly underestimated the number of M8 fixings I needed to fix the brackets to the aluminium sections. One reason is that I was inserting lots of spare fixings in between the  brackets, just in case I fancy bolting stuff to them in future, but I think I did just get the quantity wrong too. I have lots of really long M8 fixings (which were just to fix the base rails to the hoops) but nowhere near enough shorter ones. Actually, even though I ordered more at the same time as the extra bracket I still had to beg some from my husband's stores.

This last picture isn't quite as far as I have actually got since it was dark when I finally finished the last bit beside the South end door today.

Crystal palace framing

I put copper grease between the steel brackets and the aluminium frames, as I am slightly nervous about galvanic corrosion going on there, and more on the threads of the bolts, in case I decide to modify the frame, or it needs to come off for some reason. Might as well make life easier, rather than harder in future if I can!

In the end I have one complete 6m length of Aluminium box left, so I had very little actual waste, which I'm quite proud of (alhough could have saved £). The spare length I'm sure will come in handy for some construction in future, it's nicely engineered lightweight box section.

So, the next step is the cropbars. I think these just need fastening together, adding the appropriate support brakcet in the middle, supporting from the brackets on the hoops and the braces to the ridge adding. I think I have rather an odd collection of support brackets left, but I don't think that matters.

Then make the frames for the high level ventilators, tidy up the site, and I can start getting irrigation, soil, beds and paths in place.

Nancy. I'm so very happy for you.  The tunnel looks great and you are almost finished !!!

Peace

Thanks Deane!
Still a long way to go yet I fear (lots of earthmoving in my future over winter!) But I won't put the cover on now until spring. There is no point risking the winter wind season when I won't be growing stuff in there. I do want a good start for next year though.

This is a picture of the South corner showing the altered window layout taken this morning. You can see I had to overlap the braces slightly, but not as bad as the side base rail.

I thought I'd updated this earlier to confirm that the framework is all complete now, sorry about that! The only thing left to go is the doors and openers, which don't go on until after the cover, so I have a little time to get those ready as yet. I did check the apertures for the fit of the proposed frame reuse and had to adjust things slightly - the North end window, which is a reused door off the old tunnel, is slightly shorter than the new doors, so the base rail was a bit higher than the other side of the door opening. This wouldn't be a problem, I could just backfill to a different level, but the door guide needs to fit to hold the door open a bit lower down. Also the frame seemed just a bit wobbly, so it was decided that the best thing to do was to double up the bottom rail to stiffen it up. We could have made the intermediate post longer and secured that to the ground instead as I did have plenty of frame left (not so much now) but it does look neat.

Fitting the crop bars was the next thing to do. I had treated myself to 4 bars, which will stiffen the structure and give me something to hang stuff from! The horizontal bars are a 2 piece tube which my husband kindly secured together with screws. Then I got up the ladder and bolted them in them. I must admit that it looks like I didn't get the Northernmost one very level, but I didn't notice until I came to take the photo to show the completed frame and you reference to the lintel. It was a bit tricky as each bar has two supports to the central ridge pole to brace it, so lots of going up and down tall ladders. Once the cover is on it won't be so obvious and makes no significant difference to the structural eptness of the construction.

Finished polytunnel frameswork!

You can also see the start of my construction of the wicking bed against the Southwest corner. I'm writing about that in another thread here.

There will be no more construction (just earth moving) until spring now..... I might post some progress as I go.

Observation
Weather and priorities have meant I haven't progressed on this recently (I'm trying to get last year's wood away before I cut this year's ) Anyhow - lots of rain at the weekend following frost and snow thaw meant the ground is pretty saturated round here. It gives me the opportunity to see where the natural water flow is around the tunnel without the cover.



You can hopefully see the three areas where the water is standing - outlined in red.

1) Alongside the downhill side of the tunnel - this will obviously get much wetter after the tunnel plastic goes on. I'm hoping to harvest some of this by digging out a ditch there and perpendicularly under the side of the tunnel and infill with 'stick drains'. Hopefully this will irrigate the East side of the tunnel pretty well.

2) At the front of the tunnel by the vehicle access. This could be a problem - I foresee this filling with mud, so I'm going to use some of the loose rock from digging the ditches to back fill a bit here.

3) On the uphill North corner - This is maybe an opportunity. This is a bit of seepage from the land above the tunnel. I'm not planning on much irrigation on the West side - there will be overflow from my wicking beds which will be fed from gutters off the west side of the cover. But mostly that will be further to the South end. I may however be able to put a stick drain in to guide some of this water into the tunnel at this end.