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An inexpensive DIY tensioned screen/frame assembly was discussed in this thread . (NOTE: Although that thread used Parkland Plastics for the screen (as I will), the method described should work for any screen material as long as it's strong enough to hold the grommets used for tensioning.) I wanted and intended to build this screen, but I struggled with an acceptable method for keeping the frame segments from bowing inward (especially the top and bottom since they are the longest) when I tensioned the screen material.


Essentially, I saw two approaches for addressing this problem...
  1. Use more rigid materials (that better resist bowing) for the frame segments. This is tough to do, especially if you're trying to keep the weight down. Someone suggested using copper pipe instead of PVC, and while copper is considerably more rigid than PVC, it is not rigid enough until you get up to 1" pipe which is expensive AND heavy. For my room/decor, I really wanted to use bamboo, but it's not rigid enough either, so I had pretty much decided on aluminum channel. The problem with this (aside from it's distinctly non-tropical appearance ;)) is that it's expensive, and to get segments long enough, you have to get it from a metal supply store, which (in my area) are only open during the hours that I'm at work.
  2. Provide internal bracing to prevent the bowing. The problems here are that

    (A) the bracing itself has to be significantly rigid (and therefore thick) to support the inward pressure exerted by the tensioning of the screen, and

    (B)since the screen, when tensioned, lies in the plane that would perfectly dissect (any given cross-section of) the frame segments...


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    any bracing thus applied in this plane (e.g. the dowel mentioned early in the thread) will displace the screen, pushing it forward and creating visible ribs where the support members are:


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    You could alleviate this by applying the (vertical) cross-member bracing to the back side:


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    but this adds thickness - not good for me since this whole thing will be hinged and latched such that it rests flush with the ceiling when not in use.


    You could tension the screen along the front surface:


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    But this does not allow you to tension it as much (and thus you could end up with some screen ripples.)


Well, over the weekend, I was discussing this with my Dad and he suggested running tensioner wires between opposite corners. (i.e. a wire between the upper left and lower right corners, and another between the upper right and lower left corners.) This is similar to construction methods used in very old airplanes (i.e. bi-planes with a cloth skin over a wood skeleton.) As you tighten the two tensioning wires, all four sides will tend to bow outward. This allows you to tension the screen without any of the segments bowing inward - if they begin to bow inward, you simply compensate by tightening the tensioner wires a bit more. The tensioner wires can be quite thin - high test fishing line, for example, and thus will not displace the screen outward or create visible ribs.


As long as you don't overdo it (which would break the tensioners), you should be able to get excellent screen tension via this method, AND it should resist bowing/warping/twisting, too!


I can FINALLY build my bamboo-framed Parkland Plastics tensioned screen!!! I have everything I need except the grommet kit and fishing line. I can even build it using authentic, rustic polynesian construction methods (lashing segments together with sisal twine instead of using glue, screws, etc.) I'll post pics as soon as I complete stage 1!
 

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Interesting idea. Unfortunately it won;t work for me, as my frame has to be able to be set-up and broken down in relatively quick fashion.

The workaround I have chosen is to stiffen the most flexible areas (center of the top and bottom beams) by inserting a 2nd peice of PVC inside the first. I am going to use 1" PVC as the outer peice and use 3/4" PVC as the inner stiffening peice.

In order to make this work, I have to cut a slot lengthwise in the 3/4" PVC, as the OD of 3/4" PVC is slightly larger than the ID of the 1" PVC.


I should be completing my frame sometime early next month. I will post pics when I get it finished.


RG
 
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