Fan radius - Simple mathematics?

[Denead]

I am edging my pond with indian stone flags and have taken the trouble to carefully make one end of it a nice semi-circle, I was therefore thinking of cutting the slabs as a fan radius which the website says is just a case of simple mathematics to determine the cutting angles so can anyone tell me what this simple equation is? the edging will only be the width of one slab 600mm, and was thinking of using 300x600 for the best effect. Alternatively if you're in the blackpool area contact me I might easily be persuaded to let someone who knows what they are doing finish the job for me as due to the crap summer I am fast running out of holiday time to complete the edging

Thanks
Dene

[Tony McC]

You need to know the radius of the arc, and then use the length (or width) of the flags being used as a chord length.

[lutonlagerlout]

radius of a circle is 2 pi R, area is pi r squared. would it not be easier to buy some segments of a circle kit?
LLL

[Rich H]

The slabs are too big to get a really good effect. I laid a 3.6m circle with a retaining wall around then had to cut sandstone coping atop the wall to match the radius. Gave up trying to calculate and went with trial and error. Wasn't bad but the long lengths (600mm) don't really lend themselves to being laid in an arc, whatever angles you cut.

I'd consider matching sandstone setts instead.

[Denead]

To use part of a circle I would have to find a circle with the same radius as the pond edge, which is about 4' (I'm not going out to measure it exactly at the moment as it's raining yet again). Setts aren't an option, maybe I didn't make it clear, the slabs will be the edging of the pond i.e. will lip over the edge of the pond a couple of inches to hide the liner and will extend away from the pond the length of the slab 600mm so I will be cutting along the length of the slab and each one will be 300 wide which I would hope will make for a better arc

Thanks

Dene

[Tony McC]

So: you have the radius, and you have the chord length, so all you need to do is determine the angle.

I do this for a living: I'm buggered if I'm giving away the answer for free!

[DNgroundworks]

[lutonlagerlout]

theres loads of different radius circles out there dene,we had to find one recently for the "sphere " base
either that or time to get your fingers talking to the gaffer
cheers
LLL

[rab1]

try to do this as triangulation, its not that hard. all you have to do if find a centre point, divide the arc by 12 and work from there. divide 2no equal lengths from end of wall and that will give you the centre point. I`m sheet metal worker to trade and drunk at the moment. its not hard.

[Suggers]

I bet I'm more drunk than that Rab fella - (toured Ecosse once - hated that Tennents shite - (fizzy tasteless laaarger) - give me a pnt of heavy with a tequila chaser - (my grandfather said never trust a whisky drinker) - as for radiii - a pair of waders, a pin placed at zerro, a piece of chalk, a builders line, and draw ir round - easy peasy - get oot you cut saw & bob's your nephew (hic) ...** :laugh:

[rab1]

bet you loved the sausage with tattie scone roll with brown sauce though Suggers?.

[lutonlagerlout]

clabby doos are my scottish favourite

the kreel of the clyde as they say in greenock

i made the fatal mistake of calling the clyde the sea to a local, he said "ffs mon its a river"

anything that wide looks like the sea to a townie like me

ow and the famous white pudding

LLL