Curved mouldings to match an existing curve - How to work out the curve

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mikeadams1985

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Before i start, a little disclaimer.
This is the method i use, there are various other methods out there, i like this method.
The moulding used for the illustration in this guide, is not a finished product! i did all this in about 30 minutes so i could get it typed up to show Ryan (arris plastering)


Ive set this up to show a straight wall that then goes into a curve then back into a straight wall.
Step 1

Find the curved wall you wish to copy.For this example ive just randomly bent a pice of plasterboard and screwed it to some mdf to hold its shape

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Step 2
Get a straight stick, i use a piece of batten. The length of the batten varies, depending on the curve.
For this curve i found 24" was perfect.

Step 3
Mark the dead centre of your batten with a nice line, at 90 to the length of the batten

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Step 4
Using your batter, hold the batten against the flat straight part of wall on the left hand size of the curve, Level horizontally, and slide(sliding to the right) it along the wall towards the curve untill a gap starts to appear between the batten and the wall. This is where the curve in your wall starts. put a mark on the wall at the end of the battern (the far right). Repeat this step but going from the straight section on the right hand side towards the curve going left now, then mark it.
You will end up with 2 marks ont he wall, these both indicate where the wall starts to curve and is no longer a straight section of wall.
https://www.dropbox.com/s/k6j3p6ulxg...2014.34.42.mp4 - Video

Step 5
Place your batten, on the curved section of wall(inside the marked lines)m holding the batter horizontally level, using a tape measure measure the distance in the dead centre of the batten (previously marked) to the wall, my first measure was 17mm.
Repeat this step as many times as possible, were are seeking an average measurment for the gap along the wall.
I did 3 measurements(as it was a short curve), measuring 17mm, 19mm, and 18mm. So i went with 18mm as an average. You will get some that may go for example, 20mm, 28mm, 20 mm, etc, no wall is a perfect curve, but what you will make to fit against the wall WILL BE A PERFECT CURVE.

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Step 6

AUTOCAD - Ok so now we head over to the computer, and what we need to draw on auto cad is a straight line measuring 24" and then in the dead centre of this line, a line coming off it at 90Degrees measuring 18mm.


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Step 7

Autocad - Ok, so we no have the lines draw, what we want to do next, is draw a circle, but using a 3 point method, You simple select the tool, then select the Start of the batten line, the tip of the 18mm line and then the end of the batten line. Autocad will now draw a big Ass circle.

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Step 8

Get the radius of the circle, so now the simple part, click the circle and hit properties and it tells you the circles radius.
This is the magic number we have been after, All this work just for that hey! OUR RADIUS IS 98.8 INCHES or 2509MM if your me and prefer mm :)


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Step 9

Using the magic number form above 2509MM, you want to set up a gig stick attached to your moulding.
Measure from the section of the moulding that will touch the wall, and measure out along a gig stick the magic number, put a mark on the gig stick.
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Step 10
Drill a hole using a 10mm drill bit thru the gig stick at the magic mark :) (technically the hole centre of the hole should be perfectly inline with the face of the zinc profile) But i was rushing here!

Now, Drill a 10mm hole in your bench, and using the 10mm drill bit stick it in the hole but leave it hanging out a coupel of inches.

Step 11
Your hole previously drilled in your gig stick should slide over the drill bit stuck in the bench, allowing you to run your panel mould in a curve that matches the wall perfectly :)



Step 12
SPIN YOUR MOULD!
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and it should look like this....


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AGAIN THIS WAS A RUSHED JOB, DONT IN-BETWEEN MY ACTUAL WORKING DAY SO I COULD SHOW RYAN HOW ITS DONE.
The actual finish of the run mould, etc etc is not that of a finished product, just to show the process.
 
Well explained mike. This is what Ryan needs, tradesmen to show him how it is done. Thanks for taking him under your wing. I could not give him the time he needed as I have to have major surgery on the 13th.
 
It can also be applied to walls that curve the opposite way, you just alter the stick so its a U shape, by adding packing on either end.
 
Two measurements i had to work it out from
Batten length - 609.6mm
Average distance from centre of batten to wall - 18mm

What i worked out from those two measurments.
Radius of circle worked out at 2509mm
 
all my measuremtns are in mm.

hmm just tried this

(600 x 600) / (8 x 18) + (18/2) = 2509

comes out perfect


So maybe autocads converted the 24inch to 600 instead of 609.6
 
Nice post! Always good to see how to successfully do things that we don't always get a chance to work on.
A few years back I got a call to go to the San Juan Islands and look at another plaster's work that had turned out real bad. They wanted to know if I could take over the job and 'fix' this other guys work. They had a crown mould run in place on irregular curved walls and on a large oval. The guy that did it was in way over his skill level. The builder got pretty upset when I told him that it all had to be ripped out and done correctly. I told him I'd only give him a price to fix it if they'd tear out all the previous work so I could start from scratch. They hemmed and hawed for a couple of weeks then decided they didn't have a choice. I sure don't like taking over jobs that somebody else has made a mess of. They were happy with my work but they kept looking at the job as though it had cost them double what it should have, no fault of mine, but I could tell there was a cloud of animosity in the air through out the job. Took them a little too long to pay too.
 
Hate it when builders look over your shoulders while you work like a headmaster
That's an easy one Ryan just tell them to f*ck off !! Simply hand them the tools your using and say "crack on then" and walk off:RpS_thumbup:
 
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