Clunnel cloche design using Heras panels

What are Heras panels ?

They are galvanised metal fence sections that are used as temporary security fences around construction sites. Sites generally buy them outright at the beginning of the works and then once completed are cut up and skipped. Surely Allotmenteer’s can come up with a “second use” for such a robustly made freely available material. By finding a use we are delaying for 5-10 years these panels from entering the waste stream. We can get four 30-31″ inch or three 40″ inch sections from a single heras panel.

Clunnel (cloche) design for 2020

What in gods name is a “Clunnel”? Its the combination of the word Cloche and Funnel giving us a “Clunnel”. The word reflects the dual purpose of the design, its no ordinary cloche or wind funnelling wet soil dryer.

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Its an re-imagined “Geoff Hamilton cloche” design.

Geoff Hamilton Cloche explained (external website link)

After evolving the design for 4 seasons I feel I have finally got to understand what its doing and how really useful it has become. The big design change is the opens ends along with pedestals (legs) at each corner making the cloche “pivotable”. We can open and close it depending on how its angled (pitch). Also a lower overall height works best for trapping heat. The frilled valance of the 15% oversized cover also helps to trap radiant heat rising from the sun warmed soil.

It uses less parts is lighter more mobile and a more robust design able to last more than a couple of seasons on your plot without being blown to pieces or out of shape by the wind.

Five+ function (across the growing season)
+ Soil dryer
+ Seed bed Cover
+ Catch crop mini-greenhouse (globe raddishes)
+ Squash Arch (hooked onto compost bin)
+ Overwintering crop – bird protection
+ Wind brake (when turned 90 degrees & staked)
* suited to 3×5 (paces) “Clump” growing approach
** directs rainfall into gulleys around clump

Design elements identified from yearly modification
+ lower profile, 12 inch arch at highest point
+ 30 inch width, narrower and more managable
+ 6 inch legs on each corner make design pivotable
+ Oversized cover (length) giving a 5 inch flap by design
+ Slightly shortened cover (width) creates rain runoff zones
+ Clunnels can be joined together like a roman “testudo”
+ Reduced parts and build time. Improved robustness.
+ Open-ends is counter intuitive but crucial part of design
+ Hermitically sealed your cloches may hinder transpirationand be a breeding ground for fungal spores

Materials; Construction notes and costs.

Dimensions
30″ inches x 5′ ft

Requirements

  • 30″ Section of Heras panel
  • x2 6′(ft) battens (30x19mm)
  •  x4 TurboScrews long (100mm)
  • x4 Pedestel (6″) square section wood

** Position the battens as close to the ends of the cut Heras panel tubes as possible to maximise the space available under the “Clunnel”

Costs (Jan ’20)

+ Heras Panel section = FREE, you could also use washing machine transport bolts to create a “second use” for them.

+ Battens (1.78×2) £3.56

+ TurboCoach M8 100mm (7.99/50 = 16p each x 4) £0.64

+ Legs (2.4m 47x47mm treated square timber = 5.28 / 4) £1.32

* Legs could be made from 3″ in diameter branches 

+ 34″ x 72″ 1000 gauge plastic £1.99

+ x4 Scaffold toggle ties (28p x 4) £1.12

Total = £8.63 (divided by 2-3 years use)

Construction notes

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So you’ve cut up your heras panels into either four or threes depending on width requirement for your clump preference.

Firstly we need to saw off 6″ inch sections for our clunnel legs (6″ is easier to spot on the tape measure and divides into most lengths of wood. Four legs equals 2 foot from the square timber. Then cut a wedge shaped groove and drill a deep hole (8cm) into centre of each leg. See first image above. 

We need to arch our section of heras panel. Easiest way to do this is dig a fork into the ground measure out 5′ foot and dig your second fork or spade into the ground we then squeeze the panel (6.5′ / 2m) between them forming the arch.  Using the rounded end of our 8oz Ball-pein hammer bash the support bar where we are going to drill to create a well. Puncture the metal with a sharp nail or the turbocoach screw and then cut a hole with the hole cutter. This has to be done with the panel arched or the angle of the drilled holes will be wrong.

Place the batten on top and the leg below the metal tubing and drive the turbocoach screw in until you see the metal tube flex to create a nice strong frame. Pre-drilled holes in batten avoids it splitting as you drive the turboCoach screw home. Repeat for all four legs.

For the cover I used the thicker polytunnel quality polythene sheeting as it heat seams better than cheaper “goods wrapping” polythene. The tube runs on the width edges were welded using a bespoke heat seaming tool. A 1/2″ hole punch was used for the scaffold toggle tie holes.

Lean-to Tomato house, construction notes.

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Heras panel poly tunnel Heras panel lean-to mount

Q: Why bother building a tent thingy to cover your plants ?

A: Basically when your sow direct (SD’s) seedling start emerging from the soil we need to protect them from; the birds, slugs & snails and hazardous weather (heavy rain / wind / frost). Also if you place the cloche on your seedling patch a few weeks prior to planting on that bed it will warm up the soil by drying it out from its winter dousing. Geoff Hamilton was a big fan of this type of cloche, I’m sure he would have loved “Heras panels” as much as I do. Also importantly we are trying to extend our British growing season by a few extra weeks using the cheapest and easiest method. Those mid April frost could damage young seedlings, this cloche should reduce that damage.

The images below illustrate how to build a 3.2m x 1.5m roof section for our tomato house and rain shelter lean-to.

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