setting out square

[druiaghtagh]

How do i set out a large square on a piece of land. I know about the 3-4-5 formula, but how do you get the first datum line set out so the rest will follow true and square please?

[gazzawazza]

I don't believe it... I've just spent 30 minutes writing an answer to this, clicked post and got a "you must log in to post an answer..." Which I had done.... Then my answer disappeared... GRRRR and it's 2am in the morning and I have to be up early tomorrow so it'll have to wait now...

[KARL]

According to Pythagoras' theorem, a triangle with the lengths of the three sides in the ratio 3:4:5, has a right angle opposite the side of the "5" dimension. Using only a tape and stakes, start at one corner of your intended square and set out a right (90 degrees) angle by going three metres in one direction, then return to the corner and measure four metres out from there at 90 degrees (approx at this stage), the two far ends should then be connected by exactly a five metre cord (move stake(s) as necessary). The simplest way to do this is with three people, one to fix the three metre point on your (say 15m long) tape at one intended corner of the square or rectangle, a second person holds the zero point along one intended side and also catches the 12m point on the tape, while the third person pulls the tape taut in a triangular shape while holding the 7m point on the tape. Put stakes at these three locations (0/12; 3; 7) and you have set out a right angle. If you do not have a 12m length of tape use cord which does not stretch or better still wire and mark the measurement locations - otherwise you need to repeatedly "zero in" on the correct position. You can use any dimensions in the above ratios, such as 1.5m, 2.0m, 2.5m, or indeed in feet, inches, rods, chains or whatever. The longer your dimensions the more accurate the angle. Hope this helps.

[gazzawazza]

I don't @#*&ing believe it, it's happened again... It seems I can't post a thorough answer to this question... sorry...

[ralph1953]

Next time gazz.. write your answer in Notepad - go online, copy, paste and send. Anyway, that's what I do. By the way, what are your tyre pressures?

[gazzawazza]

Thanks Ralph, I'll try that next time I feel a really long answer coming on! By the way, they're 33 front, 30 rear (unloaded), 34 front, 33 rear (loaded) thanks for asking!!!

[KARL]

Afterthought: Of course, if you want to check the accuracy of your angles when you have completed the square/rectangle, you measure the diagonals - but for that you will need a long tape, or else resort to a length of wire. The two diagonals should be exactly identical in length, otherwise you have set out something that is more like a parallellogram (assuming opposite sides are exactly the same lengths, all four equal in case of a square).

[Hamish]

You can also do this with a stick and a pice of rope... Try it with a compass first. Draw a line to which you want to make the right angle. put the compass point at the position you want the angle to start and make two marks on the first line, they will be either side of the compass point . Now put the point on one of the marks and mark where the compass point was las put. Then open the compass a little and mark an arc above and bellow the first line, put the compass on the other side (the firthest point maked on the first line) and mark the point where the two arcs above and bellow the line meet. Now join the arcs and you have a rightangle.

looking back at this it seems complicated but its easy .. the egyptians wre thouht to have used this to make the bases for their pyramids. If you a really interested post here and I will try to draw some diagramms and put them on the net fou you. Hamish

[druiaghtagh]

Hamish, i would br grateful if you could post diagrams for me, thankyou

[gazzawazza]

Hamish's is an excellent method to use and simple to carry out, especially if you have lots of flat, open space to play with and no obstacles to measure and mark around or swing your outsize compass over, (ie your line and pegs). If you do have obstacles I would recommend that you make youself a builder's square out of timber using the 3-4-5 method (the bigger the better) and use this to align the lines. And as has already been mentioned the absolute check is to measure the diagonals.

Hamish, when you post the drawings, can you also include notes on how to actually post them on the net please, as I've wanted to use drawings to explain answers (this one for example... my previous answer took 30 minutes to compose see above!) and don't know how to do it. Thanks.

[Hamish]

I Will try to put them on the net at www.phosne.freeserve.co.uk/rightangle.htm this evening (about 7pm british time)

all the best! Hamish