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Author Topic: Building a 16' x 9' EMT frame...How to cut the pipe?  (Read 9773 times)
ccfore
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« on: May 25, 2011, 06:20:08 pm »

I'm building a frame of 3/4" EMT for my Carls 16' x 9' finished screen.  I've purchased 6- 10' lengths of pipe, two to be cut for the top and bottom and one each for the 9' sides.  My question is for the longer 16' top and bottom.  Do I cut both pipes so the joint is in the middle or leave one 10' pipe uncut and add the remaining 6' so the cut will be slightly off center.  I want to make sure that it doesn't sag in the middle.  I'm thinking the middle cut would make it a little stiffer but I'm no engineer.  I also bought 2 - 10' lengths of 1/2' EMT that I'm thinking of sliding into the top and bottom 3/4" pipes to make it more stiff as well.  Is this overkill?  I figure its easier to do it now than later.  Any thoughts?  Thanks.
« Last Edit: May 25, 2011, 06:48:47 pm by ccfore » Logged
Adult Beverage
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« Reply #1 on: May 26, 2011, 08:31:24 am »

I think most people generally cut both pieces to the same length.  I have heard of some people adding a wooden dowel rod inside to add stiffness as well.  If any dirt/grit/debris gets inside a 10' piece 1/2" of tubing insert can easily get stuck, essentially making your 16' pieces permanently fused.  Fine if you plan to leave it up or have room to store it.  Not so much for frequent tear-downs.  If you're using bungees to mount your screen to the frame, I don't think you have to worry about sagging.  You may notice the frame dipping in daylight, but since the screen top is below the frame and pulled taut by the bungees it will still be straight.  At night during the show you won't notice the frame at all.
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IceGecko
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« Reply #2 on: May 26, 2011, 02:56:43 pm »

with a hacksaw DUH! *P

i like the 10' and the 6', its less cuts and i suspect will sag less.

i also liked that guys dowel idea and it created the adjustable screen width too!

might be an idea to stagger the joins so they are not vertically inline, but might not make any difference, cant think right now.

mine turned out needing NO cuts (yay), checkout my plan in screen threads.

gl mate
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Litchmo
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« Reply #3 on: June 01, 2011, 09:27:11 am »

Cut it at eight and add a tee with another pipe in the center for added support
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bigRoN
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« Reply #4 on: June 03, 2011, 08:56:28 pm »

I plan on purchasing the parts to do the exact same project this weekend. In my design, I'm planning on burying at least two vertical PVC pipes behind a retaining wall, approximately 3 feet down. Besides a frame around the screen, there will be two 3+ foot sections of EMT will extend down that will fit down inside the PVC pipe to anchor the bottom. As I was thinking about it, I realized that there was an engineering flaw in my design; I'm creating a 16x9 foot sail and expecting two thin pieces of tubing to keep it in place. I'm hoping that my remedy for the engineering flaw will work. I plan on putting a forward and rear guy wire to the top corners of the screens; putting equal tension pulling the screen forward and backwards at the same time.

I like the idea of a wooden dowel to go between joining pieces on the long horizontal spans. I was thinking that EMT is designed to bend when force is applied so added rigidity may help in strength.

When it comes to cutting the pipe, I too was wondering... I have a Sawzall tool, but it may not make the cleanest of cuts. I was also thinking of using a pipe cutter for cleaner cuts.
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DandyDon
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« Reply #5 on: June 03, 2011, 11:30:43 pm »

If your screen is 16x9, you will want your frame to be 17x10 allowing about 6" extra all around.  A little sagging is not a big deal as long as you compensate for it and your screen it taut (spelling?)  I have a 16x10 white tarp as a screen with EMT and this is how I did it.  I cut my horizontals to 7' + the 10'.  I used the extra 3' sections as part of the leg bases.  I thought I would share what worked for me.  If you have your screen design determined and your pipe lengths figured out, Home Depot will cut them to size for you.  Good luck with your build.


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* 37670095.jpg (676.7 KB, 1365x1024 - viewed 979 times.)
« Last Edit: June 08, 2011, 02:20:55 pm by DandyDon » Logged
phrend
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« Reply #6 on: June 17, 2011, 03:39:34 am »

You can buy a pipe cutter at any decent hardware store.  Here is an example from the king of cheap-o tools (Harbor Freight):
http://www.harborfreight.com/no-2-pipe-cutter-5982.html

The size and type of pipe you use really boils down to how much wind your screen is gonna see... the more wind, the stronger your pipe should be.  Feeding a dowel down in to your pipe will make it stronger, but so would buying a larger diameter pipe - or a thicker walled pipe.

I also second Litchmo about cutting the horizontal pipes at 8' and using a T connector in the center - along with a 3rd vertical support.  16' is a long pipe run to have no center support.

Good luck, and please post some pictures when your done!
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Adult Beverage
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« Reply #7 on: June 17, 2011, 07:51:36 am »

The drawback to having a center support when using ball ties and grommets to hang your screen is that the center support will be visible.  Sinc the screen is suspeneded, it is located at the midpoint of the EMT tubing and hangs within the profile of the rectangular-shaped frame.  A support in the middle would come in contact with the screen and push it out in the middle.  It may not be that obvious at night during a show but it would bug me.  My preferred designs are grommets/bungees when using a center support or wrapping the frame and securing with fabric clips when using a center support.
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Sparge
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« Reply #8 on: June 17, 2011, 10:47:08 am »

The drawback to having a center support when using ball ties and grommets to hang your screen is that the center support will be visible.  Sinc the screen is suspeneded, it is located at the midpoint of the EMT tubing and hangs within the profile of the rectangular-shaped frame.  A support in the middle would come in contact with the screen and push it out in the middle.  It may not be that obvious at night during a show but it would bug me.  My preferred designs are grommets/bungees when using a center support or wrapping the frame and securing with fabric clips when using a center support.

Agreed... and the center support is still visible even when wrapping with fabric clips, just not as pronounced.  If you use PVC it reflects enough to create a light horizontal band down the middle.  Center supports also negate the possibility of rear projection.  The best designs don't have a center support, but that means a lot more bracing/robustness elsewhere.

-Sparge-
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phrend
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« Reply #9 on: June 29, 2011, 06:59:45 pm »

Agreed!  I suggested a way to off-set the center brace in another post that might be useful: http://backyardtheater.com/forums/index.php?topic=6801.msg59304#msg59304
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