(BTW, I realize I misspelled planar in the GIF. I'll correct it later)

Large EFP's are complicated to make because of the requirement of spinning the platters, which are made of thick metal and thus requiring a hydraulic press or lathe - things most people don't have handy.

:(

But I had the thought that, if you made the design of an EFP a two-dimensional problem, instead of a three-dimensional one, you'd greatly simplify the design problem, as all your charge dimensions can now be 2D linear instead of 3D circular.

:)

To wit, the attached animated GIF (to scale for an X-charge).

Gray=Steel, Green=Plastic, Yellow=Explosive, Orange=liner, Black=Bolts, Blue=Detonator

Two flat steel plates sandwich another plate, made of plastic, which serves as the confinement/waveformer for the explosive charge, with a curved strip of copper/steel/aluminum serving as the EFP platter.

The EFP strip is a flat strip of the appropriate metal bent to the appropriate curvature and held in place by the plastic former, and resting against two steel reinforcing bolts, which provide the necessary resistance to the strip to cause it to invert into the required shape under explosive loading.

Other reinforcing bolts support the plastic against explosive expansion, long enough to direct the majority of the explosives power against the EFP strip, rather than blowing out the side.

Since an EFP's effective range is a function of it's size (mass, actually), this design allows for greatly increased range since you can make it much larger than a home-spun EFP, as the simplicity of the design allows such.

Also, larger sizes mean less precision is required as regardstolerances, as EFP's small enough to be home spun are very sensitive to any design flaws, especially in the platter itself.

As an example:

Assuming a requirement of a platter thickness of 1-2% of charge diameter (width, in this case), a 1/8th thick strip would mean a charge width of (12.5"@1%, 6.25" @2%), so we'll use 8" as an average for simplicity.

At 1/8x1"x9", that strip will weigh (assuming steel) 5.1 ounces, or 5.8 ounces for copper.

That 9" strip, when bent to fit in an 8" slot, will have a curve to it that brings it almost about .7" in.

At 8", and typical EFP effective range of 100x CD, that makes for up to a 66' range. :)

(Though EFP's can have up to 1,000x CD, I'm being very conservative.)

An SC version (such as the GIF) would still punch a hole, but an EFP version would not, as the hole created by a round platter would, by the nature of this version, also have to be a 2D segment, thus a slot.

This design is by no means optimized for materials or anything else, so don't hold me to anything, but I think there's much to recommend this idea.

One thing would be the fact that it's flat. That makes it easy to fit in places that a round charge of similar size wouldn't. A small one could be disguised inside of a magazine or book cover. :)

Other places would be attached to walls, behind road signs, on roads, on top of/underneath vehicles (parked or otherwise), in the expansion gaps of bridges to attack vehicles from underneath, and many other places.

This is one of those ideas that makes me smack my forehead and say, "Why didn't I think of that?!" :)

I'm trying to think of a possible flaw or constructive criticism, but nothing obvious comes to mind. Granted, I'm still quite new to explosives.

Here's the closest thing to a potential problem I can think of -- my apologies in advance if it's baseless and/or ignorant:

Since we're dealing with a flat structure, the detonation wave that starts at the cap has to travel a much shorter distance sideways toward the two side plates than around the waveshaper and through the rest of the explosive. Could that possibly cause the plates to blow apart too soon to allow for proper function?

I'm aware that, say, a standard 3D conical design can have a shorter radial distance than longitudinal distance, but the difference wasn't as pronounced in any of the 3D cases I saw.

I had thought about that, but I believe that the shock impulse will be confined long enough by the plates to travel in the desired direction with sufficient force to perform the desired work.

Imagine a typical cylindrical shaped charge, and cut it into slices, and measure one of those slices. What's the ratio of confining mass to explosive?

Perform the same exercise with the planar charge I described. What's the ratios there? If it's the same or more, than there should be no problem.

Also, if confinement is a concern, the charge could made made from stacked and welded plates, rather than using a plastic center plate, which is used in the interest of ease-of-fabrication and weight reduction.

What you're saying makes sense. The thickness and strength of those plates is going to be a critical factor. Of course they'll fail at some point after the detonation is triggered, but it all comes down to the timing. The detonation wave will reach the side plates before it gets to the liner, but if the plates don't actually FAIL before the jet is formed, then everything should work fine.

I imagine that determining the necessary thickness of the plates theoretically would be a ridiculously complicated problem requiring sophisticated computer modeling (and I understand that much of the physics regarding SCs is still not fully understood). But experimentation can certainly yield some guidelines there.

The shockfront travels faster than the plates can fail, so it's a non-issue. :)

So... It's basically a sheet of steel, two plastic shapes, into the cavity between which is placed the explosive of choice, a strip of (copper) in a curve instead of a cone, (as in a normal SC), and then another sheet of steel on top? With some bolts to hold it all in place?

So... why plastic? And why the triangular section of plastic in the middle, creating two paths for the explosive?

I suppose this would cut a slot in the target, rather than make a roughly circular hole? If so, is there any special application for that? (Other than the obvious, it's a damn sight easier to make something like this than to shape a cone, with all the calculations and "how to make a perfect seam"...)

Or have I completely missed the point?