Low Tunnel Growing

[Worth1]

Originally Posted by 4season

I think I will try using a 28 inch bicycle rim sandwiched between plywood sheets and well reinforced as a tubing bender. It would make a narrow tall hoop.

I had to use the fork of a tree before to make a long radius in a ridged copper pipe.

In the trade it is called field bending and done correctly there will be no links.


Worth

[bower]

I had my eye on some 1/2 inch metal conduit going for $5 for a 10 foot length. I figured this would make a decent height of hoop for determinate tomatoes and squash - for a single row. I've been warned that the cover has to come off in winter, or the snow load will just mash up this weight of metal here. I'd like to design some modular units that can be joined in a longer row and then taken apart and stacked in a shed for winter.
Thought about doing part plastic and part row cover - maybe find an optimal cover for the climate here.

Re: squash bug, Scott you should check out the thread on parthenocarpic squash. It would be fantastic to ID the varieties that will reliably make fruit without pollination, for places where you want to keep that cover in place for pest control. And or when it's just too cool for pollinators. (well, I can dream! )

[Worth1]

Originally Posted by bower

I had my eye on some 1/2 inch metal conduit going for $5 for a 10 foot length. I figured this would make a decent height of hoop for determinate tomatoes and squash - for a single row. I've been warned that the cover has to come off in winter, or the snow load will just mash up this weight of metal here. I'd like to design some modular units that can be joined in a longer row and then taken apart and stacked in a shed for winter.
Thought about doing part plastic and part row cover - maybe find an optimal cover for the climate here.

Re: squash bug, Scott you should check out the thread on parthenocarpic squash. It would be fantastic to ID the varieties that will reliably make fruit without pollination, for places where you want to keep that cover in place for pest control. And or when it's just too cool for pollinators. (well, I can dream! )

Bower I have no idea what conduit costs up there but $5.00 for 10 feet is way too much.
The make three different kinds EMT IMT and Rigid oh and Plasti Bond.
EMT is all you need.
Here it sells for around $1.99 each and you should be able to get it in the 100 foot bundles for less.

Worth

[Cole_Robbie]

I'm thinking if I run a piece of conduit lengthwise on top as a purlin bar, I can save money by wiring the two conduit pieces together, instead of buying the clamps.

[bower]

Originally Posted by Cole_Robbie

I'm thinking if I run a piece of conduit lengthwise on top as a purlin bar, I can save money by wiring the two conduit pieces together, instead of buying the clamps.

I was thinking of drilling and bolting myself - those join pieces are stupidly expensive. But although I use wire a lot (way too much no doubt) as a quick fix for tomato supports etc, I wouldn't trust it to stand up to wind and hold a relatively heavy structure together. Drilling and bolting is a lot of work, however, and the bolts aren't cheap either. But if the structure is long lasting or fairly easy to maintain, worth the effort.

Worth, everything is more expensive here due to the cost of shipping. And don't forget, our dollar has lost a lot of value too. The only tough material that's really affordable is the spruce rails you cut yourself or the rocks you dug out of the ground. A strong person who has lots to eat can do it and make something from nothing.

[Worth1]

Carriage bolts is the way to go.
# 10-24 or 1/4 should do the job nicely.
Drill the hole the right size and the square part will force it's way into the conduit and make a square hole.
Nothing sticking out to hurt the plastic sheet.

[Cole_Robbie]

That was my second choice. I would go with the 3/4" if I drilled and bolted it. I was a little worried about the bolt heads on the plastic. I can cover them with white duct tape, but the sun eats it up after a few months.


ah, wait, if I just use the right bolts the head is round, I see.

[Worth1]

Originally Posted by Cole_Robbie

That was my second choice. I would go with the 3/4" if I drilled and bolted it. I was a little worried about the bolt heads on the plastic. I can cover them with white duct tape, but the sun eats it up after a few months.


ah, wait, if I just use the right bolts the head is round, I see.

Cole when you build a frame for a truck to haul cows and livestock you use these on the inside so the bolt doesn't hurt the animal.
The nut and washer go on the outside.

Worth

[bower]

Originally Posted by Worth1

...
Drill the hole the right size and the square part will force it's way into the conduit and make a square hole.
Nothing sticking out to hurt the plastic sheet.

Yeah, this is why a bit of smooth metal has it all over a spruce rail for greenhousing structure... you can spend a very long time trying to make a rail smooth enough for plastic.

[Worth1]

Originally Posted by bower

Yeah, this is why a bit of smooth metal has it all over a spruce rail for greenhousing structure... you can spend a very long time trying to make a rail smooth enough for plastic.

No kidding ask the people that make spars and masts for sail boats out of spruce.

Worth

[Salsacharley]

I've used 1 1/4" hose clamps but the carriage bolts look to be a cheaper and better way.

[bower]

Originally Posted by Worth1

No kidding ask the people that make spars and masts for sail boats out of spruce.

Worth

The old shed I built out of scrap lumber and rails about 20 years ago - the plywood roof is rotten and gone; the dressed lumber is half gone some is still okay. But the spruce rails.. they look good for another 20 years. Var (fir) is a different story. Gone in no time. The spruce is dense and the resins preserve it.

Still I doubt I could clean up rails good enough to not destroy greenhouse pastic - or row cover, for that matter. Too bad!

[clkeiper]

Honestly... go with real greenhouse products. they are designed for that and will hold up way better and be cheaper in the long run... they are more convenient to get your structure together and will not bend and flex or deteriorate like other products will. Everything is uv stable, galvanized so there isn't rust and designed so there aren't pieces sticking up that you are needing to cover so you aren't ruining the plastic. When you need to dismantle it it comes apart and you can put it back together easier than the "jigsaw puzzle" you rigged trying to do it cheaper. The greenhouse plastic lasts at least 4 years unless you ruin it with a knife or some other sharp object. What is your time worth? sometimes spending a little more costs less in the long run.

[loulac]

Here’s another suggestion, cheap and versatile :
I bought strong galvanized wire, cut lengths and bent them into half circles to make tunnels 10’’ high and 15’’wide plus 7’’ on each end to be buried into the ground. They are big enough for one row of lettuce. For several rows or bigger plants the size is different : 2 feet high and 3 feet wide. I tie their tops together with a string to keep them vertical. I buy plastic wide enough to cover the wires plus 8’’ on each side that I load with bamboos, sticks etc. kept in place with stones. I never care about overheating under a strong sun, I’ve never had any bad surprises !

[bower]

For lettuce and other crops up to 2 ft tall my friends at the farm don't use any supports. Row cover is laid over the bed and all the edges are buried in the soil as well as anchored with rocks. Burying the edges is the way to use it for pest control - caterpillars and also flea beetles, rust fly on carrot and parsnip etc. The plants just push up the row cover as they grow.
You have to take the cover off for weeding or thinning, and then put it back in place with buried edges. But this works really well for pest control and gives a great head start on the season. I think there is improved germination too for direct seeded crops, because of the moisture retention under cover.

For squash they use some short lengths of black plastic pipe as low hoops, with the ends dug into the soil. The hoops are not even joined to one another so they do flop down a bit. But they are enough to give the squash the head space that they need to push their way up without breakage. Again the edges are buried under. When it's time to pollinate the squash they remove the cover but leave the hoops for easy cover in case of a frost.

This wouldn't work for tomatoes, I reckon, because even Cole's determinates will need some support. And I think tomatoes would also benefit from extra head space and less contact between the cover and the leaves.