Hi,
here´s another pic, showing one of my very first sheet stators.
As You may see the clear tape was attached before glueing the spacers.
You can also see the softly serrated rim of the sheet.
Tensioning jigs have been shown before in other threads.
In basic You need only Tension in the long vertical direction, but You can´t simply use a flat tensioning jig.
There are two constructional ways.
The first is to use two fixed guides, mounted to a frame, one each positioned to the top and low end of the panel with a distance a bit larger than the panel itself.
The guides should have the same curvature as the panel and soft shaped edges so that the membrane can´t be ripped and is able to ´glide´ over the edge of the guides.
The membrane is pulled from the roll and laid over the guides with considerable overhead.
The ends of the membrane may then be fixed/clamped in a single point, of which one may be positioned fixed, while the other shall be moveable.
A weight, or a lever or a screwing mechanism may be attached to the moveable clamp that allows to exert sufficient pulling force on the membrane.
The long vertical parts of the frame may be used to put tape on the membrane and the frame to exert just a tiny amount of horizontal tension to only straighten small wrinkles on the membrane.
The second method is to make the guides thicker and use a material where double sided tape adheres to very well.
One or both guides may be attached to a stiff frame, but moveable by means of screws or weights.
Pull the membrane from the roll and glue it to the guides.
The advantage is that you need much less membrane overhead, but the disadvantage is that it is more difficut to get the membrane glued to the guides without wrinkles and perfectly parallel on both guides.
So I´d rather try method no.1
A last word to the curvature.
Though the curving looks very well and evenly executed the degree of curvature is probabely double the practical value.
Only slight curvature (+-15° max) is practical, as it becomes nearly impossible to shape the membrane wo. the hourglass effect becoming too much (see pic of my panel or from ML).
The curvature is mainly for stability reasons anyway and if You mount the finished panel into a frame a slighter bow is more than sufficient.
The widening of the distribution character as claimed by ML only applies to the highest highs and the effect is much less than the claimed 30°.
1/16" is the upper end of the thickness range I´d recommend.
1.0mm to 1.1mm (~1/24") are values I use and which are ok for hybrid panels working from 200Hz up.
Remember that the most important point in designing a good esl panel is efficiency.
A 50% increase in d/s lowers efficiency considerably and doesn´t gain You anything but almost all parameters will worsen.
To preserve dynamic stability You will have to add horizontal spacers, positioned every 80-90mm distance.
The spacers also help in reducing the hourglass effect and they centre the membrane between the stator sheets.
3M foam and VHB tape (6mm wide) has proven excellent here, as they stick well to the stator and membrane -thereby taking some of the vertical acting tension force from the top and bottom glue joints- and they perform some damping due to heir softness.
When the stators are finally mated such a panel will hardly rattle at all - while the only at the top and bottom glued ML panels rattle like hell, even after beeing mounted to the mounting frame.
When using the 3M foam tapes You should look at one that is designed to stick well to Polyester and the kind of insulation laquer You used.
If You are painting the stators Yourself a ´standard´ PU laquer for boats or staircases is a good choice for the finishing top layers with regard to electrical characteristics and bond strength with 3M tapes.
jauu
Calvin
