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Discussion Starter · #1 ·
I've been asked to put arches on a 16 foot Garage door. Never had to do this. Starting 12" down from both sides. Any quick ways to do this. I have a sheet of 4x8 plywood I was going to use for a template then make 3 more that mirror it to start the framing and block the arches in between. I was looking at some videos But seems too much of an arc then I need, since I'm starting at 12" as per blueprints.
 

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A partial circle won't work for en elliptical arch. Map it out on Google sketchup, measure the vertical height every 3" horizontally. Transfer that to plywood and lay it out, then smooth the line out by hand if needed, and cut it out. That's about the only good, consistant way I have found to do arches with a fixed height.

The expensive way is to have a company make an arch frame for you.
 
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I used the sketchup layout method on these arches. One is 13', the other is 19'. The string method was too inconsistent.

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Discussion Starter · #7 ·
The plans changed by the minute. The builder just gave instructions for 12" drop from the 2x12 frames of the doors.
 

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I don't think a radius would look right. I tried that first on mine.
 

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I've been asked to put arches on a 16 foot Garage door. Never had to do this. Starting 12" down from both sides. Any quick ways to do this. I have a sheet of 4x8 plywood I was going to use for a template then make 3 more that mirror it to start the framing and block the arches in between. I was looking at some videos But seems too much of an arc then I need, since I'm starting at 12" as per blueprints.
It appears to me to be just a simple radius. That being said, my preferred method of plotting out such a radius uses this formula R= h/2 + width squared over 8h.
R being the radius, h is the height, width is.. well in your case the width of the door.
In the link below it shows its more clearly then my explanation, but SSDD :whistling
http://www.mathopenref.com/arcradius.html

So once you have your given radius, you mark the length of your arch on the bottom of the plywood. From each of those points, swing an arc = to the radius until they cross. Set a nail, and swing from that point (centre of your circle) And if you have done everything right, the radius will connect the starting points and pass through your 12" rise in the middle. :thumbup:
Don't let the math throw you off... its easy enough to figure out.. i figured it out when i was 15 :jester:
 

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I'm going with Sabagley on this one. We frequently do garage arches this way using a true radius. [(W/2)² + H²] / 2H.

Also, When you put in the radius, make it about 2 1/2 inches narrower than the jamb depth and leave the back (inside) frame square. The door installer puts his stop on the square frame and not on the arch, because the door will rub on the arch if you take it all the way in. This means you need to use something like good plywood or soffit board for your inside arch so it looks good painted when the door is up.
 

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I've done quite a few garage door aches and have found that using the overall opening width as the radius of the arch seems to be the most visually pleasing. It also tends to work well with garage doors with arched glass inserts.
 

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I watched the Latino fellas do it by standing there sheets end to end than pinning a string at each end, letting it sag the appropriate amount and then spray painting it so it left a line they could cut to.
 

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Discussion Starter · #13 ·
It appears to me to be just a simple radius. That being said, my preferred method of plotting out such a radius uses this formula R= h/2 + width squared over 8h.
R being the radius, h is the height, width is.. well in your case the width of the door.
In the link below it shows its more clearly then my explanation, but SSDD :whistling
http://www.mathopenref.com/arcradius.html

So once you have your given radius, you mark the length of your arch on the bottom of the plywood. From each of those points, swing an arc = to the radius until they cross. Set a nail, and swing from that point (centre of your circle) And if you have done everything right, the radius will connect the starting points and pass through your 12" rise in the middle. :thumbup:
Don't let the math throw you off... its easy enough to figure out.. i figured it out when i was 15 :jester:
I get 390 since its 12" high on the drawings and 192 wide opening. Not sure what 390 means is that 39 degrees. I may have to get 2-8 foot pieces of plywood end to end.
 

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I use the same formula as pro but I express it differently:
1/2width squared plus the height squared divided by 2x the height = the radius of the arc segment.
 

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Discussion Starter · #15 ·
So on a 16 foot width of a 12" height from Left and Right so it meets to zero in the center of that 16 feet. (8feet) is what I am after. Thanks
 

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I get 390 since its 12" high on the drawings and 192 wide opening. Not sure what 390 means is that 39 degrees. I may have to get 2-8 foot pieces of plywood end to end.
390" radius (32'6"), the arc angle is 28.50º, the arc length is 16'2".

Tom
 

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It appears to me to be just a simple radius. That being said, my preferred method of plotting out such a radius uses this formula R= h/2 + width squared over 8h.
R being the radius, h is the height, width is.. well in your case the width of the door.
In the link below it shows its more clearly then my explanation, but SSDD :whistling
http://www.mathopenref.com/arcradius.html

So once you have your given radius, you mark the length of your arch on the bottom of the plywood. From each of those points, swing an arc = to the radius until they cross. Set a nail, and swing from that point (centre of your circle) And if you have done everything right, the radius will connect the starting points and pass through your 12" rise in the middle. :thumbup:
Don't let the math throw you off... its easy enough to figure out.. i figured it out when i was 15 :jester:
Nick what kind of string do you use. We tried regular mason line but it stretched too much to get a good arch.
 

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If you want to plot the arc using 3" o.c. Start at the center and work your way out.

For some reason the photos ended up out of order. You need to go from length 8 to length 9. You'll figure it out.

Tom
 

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