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Question 758297: I hope I picked the correct category; FYI: I am not a math person, I am a fledgling gardener who needs to know the linear feet of PVC pipe to purchase to span a 4'5" framed bed to ensure an arched height of 4'. Basically, I will be using the PVC to make a simple 'frame' over which I can drape bird netting to keep the deer from eating my veggies. Thank you ever so much!
Found 2 solutions by Alan3354, KMST:
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! needs to know the linear feet of PVC pipe to purchase to span a 4'5" framed bed to ensure an arched height of 4'.
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Can you send a sketch to
moralloophole@aol.com
Answer by KMST(5328)  (Show Source):
You can put this solution on YOUR website! DISCLAIMER:
I am mostly a theoretical problem solver. I may make calculations for a design on paper, but I rarely build anything.
THE IDEA AS I UNDERSTAND IT:
I imagine you are trying to make something like a covered raised garden bed I saw on Coloradomoms.com that referred to Sunset.com for instructions. The instructions used two arches of 1/2" PVC pipe, with the ends stuck into firmly secured 12" lengths of 1" pipe to span the 4' width of the raised bed. The Sunset.com instructions stated to use 6' of pipe for each arch, but that will not give much height and their pictures showed that. The pictures on Coloradomoms.com showed a much nicer, taller raised garden bed that must have used much longer PVC pipe pieces.
MY CALCULATIONS:
A perfect semi-circle would have a length of  times the diameter it spans, just to give you a height of half the span, and you would need some extra length at the ends, if the ends are going to be tucked into the wider PVC pipe.
For their 4' span in the SUnset.com instructions, they should have needed 1.57 X 4' = 6.28' for an arch just 2' high, plus some extra length for the tucked in ends.
Spanning a 4'5" width as a perfect semi-circle (with a height of 2'2.5") would take
4'5" X 1.57 = 6'11" of PVC pipe.
For the height at the center to be 4', you would need an extra length of PVC pipe at each end.
Assuming perfectly vertical sides and a perfect semicircle at the top, an extra length of 4'5"-2'2.5"=1'9.5" on each end (3'7" total extra length) would add the needed height.
For that garden archway shape, adding up, 6'11"+3'7"=10'6" would go from the ground straight up to 2'2.5" high at the edge, then to 4' high in the middle, and back to the ground spanning the 4'5".
With semi-flexible pipe, you get more height at the middle and the sides are not perfectly vertical.
I would guess a 10' piece of 1/2" PVC pipe per arch would be an easy, economical option for what you want. Can you get longer pieces? Can you cut them as needed?
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