Andrew Roesner wrote:Hi All!
I am in the midst of building my own hoop house. it's 30' wide and 95' long. The many "build your own greenhouse" websites that sell hoop benders don't make a 30' bender so I'm making my own. The first version is a 4'x 8' sheet of plywood cut in half length wise and screwed together. I stretched some masonline out to a 15' radius and traced the arc on the plywood. I used the cut out from that to add a 3rd ply in the middle of the two sheets and set it back about a half inch so the there is a groove where the hoop can rest while bending.
I gave it a try on saturday and everything works fine, except the hoops do not form a 30' diameter. not even close. I'm using 2 24' lengths of 1 5/8" top rail to create the hoop. the obvious answer is that the hoops snap back a bit after bending and so I'm guessing the radius of the bender needs to be less than 15'. the question is, HOW MUCH LESS!?! the approximate diameter when the hoops are assembled on the ground was 41'. I know that the diameter when assembled should be a foot or two wider so that the hoops will have some tension when setting them, but this is too much.
does anyone have a suggestion of what radius to try to achieve my desired 30' diameter. is there maybe an equation? i've looked quite a bit but i've not found anything on the interwebs. does anyone have a link to point me in the right direction??
I found a website that mentions a 10% spring back which means i might want a 13.5' radius. I'd hate to cut a new radius and end up with it too narrow!
Thanks for the help!
Using those results, you are only getting a finished height of 10.6 feet. You need to keep your current jig but pull your bending a little past
so it springs back to the radius. Until you have a 15 foot height you'll be long on the width.
R Jay wrote:
Using those results, you are only getting a finished height of 10.6 feet. You need to keep your current jig but pull your bending a little past
so it springs back to the radius. Until you have a 15 foot height you'll be long on the width.
If the pipes have been bent so that the total width is 41 feet with a height of 10.6 feet, then the pipes were bent too far to start with.
R Jay wrote:
Hi Roger
I suspect that there was only one bend at the 12foot mark and it went too fargiving the
10.6ft height and 41 foot width
Gradual bends along the 24foot lengthand using your suggestion of going slightly
past so it springs backwill give a 15foot height and 30foot width
Using those results, you are only getting a finished height of 10.6 feet. You need to keep your current jig but pull your bending a little past
so it springs back to the radius. Until you have a 15 foot height you'll be long on the width.
Not if he wants a finished width of 30 feet...
John Daley Bendigo, Australia
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