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oz93666

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  1. I beg to differ on this ...My understanding is this 15mm is to protect from damp and frost ... I cannot see what strong forces would be acting to push the wires out of alignment... If you think it would fail because of not enough cover in what way?? Consider bamboo , it's a similar arrangement , all the fibers are aligned along it's length , the way it can be split so easily shows there's nothing going around the circumference , there's nothing much keeping the long fibers in place , if it had a solid core it would be much stronger .... I have experimented with 40mm tube and 6 wires the result was very strong Those Triangles composing the dome are the ultimate structural element , I don't think they can go anywhere .... When talking concrete we do tend to imagine large weight , but remember the strut are only 55mm dia , that's cross sectional area of 24 sq cm ... density of reinforced concrete is 2.5 ... that makes less than 6Kg per meter ... a 2.5 meter strut would weigh 15Kg ... very light ( I will probably have a small cental hole running along the center for feeding lighting wires .This will reduce the weight to 12 kg I have experimented with pipe alone , but it sags and degrades in sunlight , then sags even more .. I have a supply of perfectly sized granite chips , Sharp but about the size of a pea .... Sand is a big problem here ... to make perfect concrete I understand sand should be carefully graded .... Yes ...how to make joints ??? I was thinking of making a shutter around the joint , concrete around the wires which would come out 10cm from the end of each strut .. Wood has many advantages , could staple on the mosquito net ... termites and rot and protection from sun an issue It may all be too labor intensive ... I'll experiment with making fence posts first and see how quickly I can make them Thanks for your input everyone ... Keep it coming
  2. No building regs where I am Stewpot ... I'm a Brit ex-pat living in Thailand ... For the dome the struts would be about 2.5 meters length ... this design , an outside hang out /growing area free from mosquitoes and veggie eating bugs This plan for the struts seemed best , I have lots of this wire , just getting rusty , concrete costs nothing , and the plastic pipe will make a nice surface to attach the mosquito net to.
  3. I am thinking of making some reinforced concrete posts for use as fencing , but also frame elements for a geodesic dome , the faces will be mosquito net . Since I have a lot of 4 mm high tensile steel already, I plan to use this. Although only 4 mm dia it is spring like , sold in a 1 meter diameter coil , when released it springs out strait , and is much stronger than normal re bar ... thin walled low quality rigid plastic water pipe is very cheap so I plan to use this ... "2 inch" (in reality it has a 55mm internal diameter ) ... I will have 16 lengths of the 4mm steel wire in each drainpipe tight to the circumference on the inside of the pipe and arranged symmetrically all around the circumference , the plastic pipe will not be removed after concrete sets and this will protect from frost /water damage , this allows me to keep the reinforcement tight to the surface for maximum strength in finished posts .. I will vibrate well , and apply vacuum to the top of pipe after concrete is poured , to get air bubbles out. I have two questions ... 1 ... I understand it is customary to have hoops of wire going around the 16 lengths of steel and tied to them , I think this maybe mainly to hold these in the correct alignment, but will also give a strength component preventing failure of the finished post ... Do I really need these for strength ? I can secure the steel wire by other means , if I do need them , how many , how frequently ... 2... It maybe possible to pre stress the 16 wires , what is the approximate % increase in strength of finished product from doing this ??? Thanks in advance ...oz
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