Everything of the information on this webpage is available from the U.S governments websites. And it is also available on the weapons industries homepages. And you have seen them on TV.
And you will learn the same from the army's specialist troops.

Shaped charges are also used in the oil industry and for civilian demolition jobs.
The oil industry are detonating millions of shaped charges every year.

"According to defence sources, basic armour-piercing weapons are easy to manufacture, drawing on principles discovered more than a century ago and in use since World War Two. "

Penetration :   Long rod EFP.
Use against armour steel, armoured vehicles.
Just make a  hole in as thick armour as possible.

Demolition :   Short rod EFP, flat projectile
Use against concrete, buildings, bridges.
Make a bigger hole or destroy the target , all kinetic energy absorbed in the target.

How big EFP do you need ?

Armoured vehicles can be split up in at least two classes of armour thickness.

• The tank which has very thick armour.        ( 1 - 5 % of all armoured vehicles. )

• All other vehicles 20 - 40 mm armour.        ( 95 - 99 % of all armoured vehicles. )

The EFPs should have the size of  penetrating more than 40 mm armour
That's enough to kill 95 - 99 % of all armoured vehicles when attacked from any direction.

An EFP of size 150 mm diameter is optimum
Use it for mass production.
It will penetrate 40 - 75 mm of armour steel dependent on how careful you were in the construction.

A heavy battle tank can only be penetrated by a 150 mm EFP at the top or bottom where the armour is thinner. A top or belly attack.
Abrams drivers 2.5 inch (64mm) top armour.

The side armour of an Abrams is 150 - 200 mm in thickness. (If you does not hit the additional thickness of the wheels and tracks.)
If you want a special big size EFP for the killing of a tank from a side attack, then you need a 400 mm calibre EFP or more. See flat efp design further down on this page.

Iron, copper or tantalum for the liner ?
The penetration for an EFP projectile made of iron in armour steel is almost the same as the projectiles length. And the projectile length is almost half the diameter of the EFP-dish which makes it easy to calculate.
But the penetration is also dependent on the specific weight of what the EFP projectile is made of.
In theory copper gives 14% better penetration than iron for the same diameter.   Some EFPs use a liner made of tantalum, which can penetrate twice the armour thickness when compared to a liner made of iron.
Tantalum : Specific weight 16654 kg /m³
Copper : Specific weight 8960 kg/m³
Iron : Specific weight 7874 kg/m³

The only reason for using a liner made of tantalum is that you have limitations in the available space. Some EFP weapons (SADARM) are delivered to the target by a howitzer which have a maximum 155 mm calibre.
There is no such limitation in size for your roadside bombs.

For your homemade EFPs, don't bother about tantalum, increase the calibre instead.

 

The EFP-charge's weight increases with a cubic factor (diameter³) which means that an EFP of 200 mm in size is 8 times heavier than an EFP of 100 mm size.

The penetration in aluminium armour is 2.7 times the penetration in armour steel.
Some military vehicles have armour made of aluminium.

The penetration in concrete is 3 - 5 times the penetration in armour steel.
An EFP of 150 mm diameter in size can punch a hole through 20 - 40 cm of concrete.

Attacking fortified concrete buildings
EFP is a standoff demolition tool. You don't have to be near the target.
All those concrete barricades which have been erected to stop suicide vehicle bombs becomes useless if the resistance use EFP. Just shoot over any obstacle.

If you intend to attack and destroy a building :
Sometimes a conventional attack with 100 men armed with heavy weapons is out of question because of the enemys superior firepower.

What you need is a surprise attack of 0.1 seconds that kills the enemy before they even have a chance to start using their superior weapons. And you need a weapon that can shoot over all those concrete obstacles that the enemy have put up to stop you. A car loaded with multiple EFPs is one of the best weapons for that job.

A single fighter in a car can do the job that 100 men with conventional heavy weapons can't do.

You can pack the firepower of an entire army into a single car filled with 100 EFPs.
And you can deliver all those EFP projectiles with a simple push on the button.
The fight is over in less than 0.1 seconds. No time for the enemy to fight or defend themselves.

Triple 15 cm diameter EFPs against 20 cm thick reinforced concrete wall.
Will open up a 75 cm diameter hole.

But the resistance will rather put 20 EFPs in line on a truck and aim 1 meter above the ground ?
Because they want to kill the enemy instead of open up an entrance.
If the building has a second floor then add another line of EFPs.

20cm diameter EFP against 60cm thick reinforced concrete column.
This picture is from an U.S military test.

Concrete barricades can't protect a building against a vehicle filled up with the EFPs above.
Because you can attack from far away and shoot over any obstacles.

The most important question, why use EFPs ?

Only EFP can penetrate the armour.
Metal fragments from artillery shells can't penetrate the armour.
RPGs can't penetrate the armor because of easy countermeasures like slat armor (steel bars) and external boxes.
But these counter measures don't work against EFP.

Big fertilizer bombs made of ANFO Ammonium Nitrate Fuel Oil are heavy and take long time to plant. Which becomes a logistics problem for the resistance. But they are still useful.

Most other types of roadside bombs under the road or too close to the road are useless because of the enemy's metal detectors. And these bombs that the enemy can find and neutralize too easy are a big waste of your time and money.

It's a question about becoming more effective.
To kill more armour when carrying and using less explosives.
To plant more low weight armour killers in the same amount of time as the resistance use for carrying all heavy explosives for killing a single vehicle.
To save a lot of time by not digging too deep and wide holes in the road.

War cost money, and you must try use some mathematics and planning to become more effective.
And try maximize the number of killed enemies per spended dollar and worked hour.

The disadvantages of  the big bombs are obvious :
Artillery shells are heavy (50kg), you must use a car.
It's time consuming. And it's not effective.
It's easy to locate and disarm because digging a very big hole in a paved road is obvious to an eye. Any metal buried under the road can easily be detected with metal detectors.

An EFP of 3 kg is more effective than 500 kg of artilleryshells, if you look at how much damage you can give the enemy per kg of explosives and per worked hour. Which means that you can kill more armoured vehicles per worked hour if you start using EFP.
Become more effective !

EFPs are 6 times more effective at killing the enemy compared to all other types of bombs.

99 EFPs planted in July 2007 killed 23 and wounded 89

The U.S. battlefield statistics for July 2007 reveals that the EFPs have a killing efficiency of 23% while other types of bombs have an efficiency of less than 4%. But the killing efficiency of the EFP can be improved up to 40% in the future while the other types of bombs will have a decrease in their killing efficiency down to perhaps 1%, because the easy target Humvees are being replaced with the new types of MRAP vehicles.

The EFPs advantages :

• Penetrates all armour. No armoured vehicle is safe.
• EFP is a cannon which means there is no safe standoff distance for the enemy.
  Concrete barricades can't stop the use of EFPs
• The counter measure that works against jetting charges like RPG is useless angainst EFP.
  The boxes and steelbars (slat armour) on the vehicles that predetonates the RPGs at safe distance from the armour will not protect against EFP. Because EFP is a projectile, not a jet.
• Low weight. You can carry 5-10 EFPs in a bag, you don't need a car.
• You use less time to plant EFPs.
• You can hide yourself in the vegetation when you plant the EFPs instead
  of being visible near the road. (Snipers and unmanned drones watch the roads.)
• You can plant the EFP-cannon at longer standoff from the road making it harder to
  locate and disarm. The enemy must scan and clean a bigger area hundreds of meters wide. It's not enough to just use explosives to blow a narrow path through the minefield as they do against conventional mines. And mine sweeping vehicles have no use of the robot arm and becomes vulnerable.
• EFPs directs the destruction energy at the target. Less collateral damage
  if used in a city. Especially if attacking the target from the underside.
  

The main disadvantage of EFPs is that you must build them.
While artilleryshells are available from the shelf.
Another disadvantage is that the metal liner is visible on radar. But the god news is that the landscape is polluted with metal especially in urban areas. And it's possible to use a steelbar instead of a circular liner which is easier to hide. Or try build a pop up mechanism.

Helicoptermine using EFP

Bangalore blade
An explosives filled aluminum profile tube EFP used to cut concertina wire and destroy mines.
The newest evolution of the Bangalore is the Bangalore blade, an updated version made from lightweight aluminium and using explosively formed penetrator technology to breach obstacles which the original Bangalore would have been unable to defeat. In a test detonation conducted on the television show Future Weapons, the Bangalore Blade blasted a gap roughly 5 metres wide in concertina wire, and also created a trench deep enough to detonate most nearby anti-personnel mines. The Bangalore Blade was developed in the United Kingdom by Alford Technologies and is intended for use with both standard army and Special Forces units that require a lightweight, portable obstacle-clearing device.
http://en.wikipedia.org/wiki/Bangalore_torpedo

Another proof of the fact that EFP is easy to build at home and that
EFPs don't have to be circular or machined with precision in iran.

SADARM, an armour destroying EFP weapon delivered by a howitzer, (artillery cannon).
Seek And Destroy ARMor
The warhead is hanging and spinning in a parachute and an EFP is fired if a target is detected with IR or other sensors.

M-killing and K-killing tanks.
EFPs are also used in modern types of antitank mines. Killing the tank from the underside.
Older types of mines caused what they call M-kill (mobility kill), destroying the tracks.
New types of EFP_mines causes K-kill, killing the crew.
You will find out more if you do a search on TRMP-6, Russian antitank mine.
And U.S artillery delivered scatterable antitank mines.

The countermeasure against these new mines is to hang armour as close to the ground as possible.
It's a matter of distorting the formation of the EFP slug
Your countermeasure against that is to put the EFPs deeper down in a deeper hole to give them enough acceleration time and EFP-slug forming standoff distance.

These mines have 2 explosive charges, the first small charge blows off the soil which hides the mine, the second big charge launches the EFP.
Some of these antitank mines uses no more explosives than in a handgrenade.
That's effective resistance if compared to the older tank mines of 10 - 20 kg explosives.

The EFP can be placed at the bottom of a tube ( otherwise the alternative is to use a second charge to blow off the soil and camouflage ). The end plug should be of low weight.
The tube will give the EFP distance enough to shape and accelerate. And is a countermeasure against the countermeasure. (Against the hanging plate under the vehicle that stops the EFP projectile from forming and accelerating.)

Hezballahs roadsidebombs forced the occupation of lebanon to end.

The Hamas manufactured Shawaz (Flame) EFP has a penetration capability of 200 mm (8") of steel.
The liner looks like a very deep dish which indicates that this is perhaps very close to a jetting charge.
There is a grey zone between EFP and jetting charges that is worth some research if you want to improve the penetration. Very long stretched EFP projectiles.

How to build EFPs in the kitchen

The Liner
The most work will be on shaping the liner, the metal disc.
Use copper, brass, iron or steel
Copper  melts at 1083 degrees Celsius, and brass at 900,  iron melts at 1500.
Try casting or use a hammer or hydraulic press.
Because you have no lathe at home ?
What's best for massproduction.
But first look at the available EFP housing to see what liner diameter to use.

The easiest EFP is built from a simple steel bar.
Read more about further down on this webpage.

The more precise you do the work the more precise will the EFP hit the target.
Your own homemade EFPs will have perhaps have 10 - 30 % less penetration than the experts, but you can compensate for that by using a bigger calibre.

For homemade EFPs it is trial and error.
Try some different constructions and test against a concrete wall (for demolition) or against steel plates (for penetration), use the best construction for mass production.

Housing
The housing can be made of glass fibre filled polyurethane, concrete, or a steel pipe
The only reason for using polyurethane is to minimize the killing fragmentation in undesired directions. Why not just "borrow" one of those bombed and destroyed lamp-posts from the street if it has the right diameter. The housing contains and keeps the right shape of the explosives and the mass also helps concentrate the blasting energy in one direction.

Explosives
If you have plastic explosives then use that.

Else, take it from the artilleryshells.
The two most common explosives in artilleryshells are TNT and RDX.
Explosives are poisonous and will colour your skin, do the job outdoors or in a well ventilated room.
RDX in bombs and artilleryshells is used in a mixture with melting TNT or wax to make it castable. The RDX mixture then has many funny names like hexogen, hexotol, comp-A, comp-B and things like that dependent on in which nation and what it is mixed with.

Before trying to melt the explosives, remove any heat sensitive fusing explosives.
And first try a very small piece of explosives  instead of blowing up yourself and 10 kg of explosives.

TNT melts at 70 degrees C (some temperature variation dependent on which atoms in the toulene molecule were nitrated, don't be confused if you hear different sources tell different temperatures.)
The important thing to remember is to never overheat !
Keep far away from the approximately 200 degrees C where it sometimes detonates.

Try heat up the grenade in a water tank. The water temperature never exceeds 100 degrees as long as there is water. It's more safe if the grenade never comes in contact with the bottom of the tank.

RDX is more powerful than TNT.  RDX gives more penetration and demolition.
If you use TNT instead of RDX then you need a bigger EFP to do the same job.

Make sure there are no big air bubbles in the explosives when packing the explosives.
Airbubbles destroys the shape of the detonation wave.

Blastingcaps.
Use standard blastingcaps.
An EFP must be initiated symmetrical, in the center and aimed in the firing direction.
If you want an accurate cannon, then do a precision job.

For multiple EFPs, you must use explosives filled tubing of exactly the same length,  instead of separate blastingcaps.
Initiate simultaneously in one end. This will prevent the EFP that detonates first from destroying the others, or from directing them in another direction.

Use your fantasy when planting EFPs.
Minimize the weight of the camouflage, or remove it before detonation, or keep the standoff to the target short. Because the camouflage will change the direction of the projectile if it does not hit perpendicular.
Blastingcaps are available with different delay time which makes it easy.

If you need a popup weapon then try build something from a gas-spring that you can take from a cars backdoor or from an office chair..
This means that the weapon is invisible from the road until it is fired.

Shaped Charges

Shaped charges can be divided into two types, those producing relatively slow moving projectiles, the so- called"explosively formed penetrator or projectile" (EFP)  and those producing fast moving stretching jets,"jetting shaped charges". These two types can be distinguished by fundamental differences.

The liner of an EFP is a shallow dish with the depth of the dish typically being less than 0.25 of its diameter whereas the liner of a jetting shaped charge is typically a cone or hemisphere in which the depth of the liner cavity is greater than 0.4 of its diameter.

The shape most commonly used for the jetting liner is a cone, with an internal apex angle of 40 to 90 degrees. Other widely used shapes include hemispheres, tulips, trumpets, ellipses, and bi-conics; the various shapes yield jets with different velocity and mass distributions.

The chief advantage of the EFP over a conventional (e.g., conical) shaped charge is its effectiveness at very great standoffs

Explosively Formed Projectile (EFP)

Wide angle cones and other liner shapes such as plates or dishes do not jet, but give instead an explosively formed projectile or EFP. The projectile forms by dynamic plastic flow and has a velocity of 1-3 kms-l . Target penetration is much less than that of a jet, but the hole diameter is larger with more armour backspall.

An EFP must be aerodynamically stable so as to strike the target within a small miss distance and a small angle of obliquity. In the U.S., extensive work has focused on forming EFPs with canted fins, to induce spin-up. By forming canted fins on an EFP, improvements in aerodynamic stability can be realized.
There exist near a dozen patented methods of creating fins and canted fins.
For example by placing some pieces of metal where you want to slow down the accelerarion and cause a bent shape in the liner.

The need for an aerodynamic shape is not necessary for the medium or short-standoff.

An EFP is designed to produce a non-stretching projectile moving at a velocity in the range from about 1.5 to about 3 km/s whereas a jetting shaped charge produces a stretching jet with a tip velocity in the range from about 3 to 10 km/s and a rear end velocity less than the tip velocity such that there is a velocity gradient along the jet which causes the jet to stretch.

EFP liners are typically thicker than jetting shaped charge liners of a similar diameter.

The EFP projectile velocity depends on the liner to explosives layer thickness ratio.

Because EFPs are not intended to produce very fast moving jets, they require less explosive. Jetting shaped charges in the prior art are therefore typically longer than EFPs of a similar diameter.

The EFP is relatively unaffected by first-generation reactive armour. (Armour made of explosives.)

If the EFP perforates the armour, extensive behind armour effects BAE will occur. The BAE is mainly caused by the hot armour and slug fragments being injected into and bouncing inside the interior space and the overpressure (blast) caused by this debris.

Aluminium and composite armour limits the BAE caused from fragments.
Which limits the harm to those hit directly by the EFP projectile itself.
But the resistance can fire multiple EFPs at the same vehicle to make sure that noone survives.

What happends if you are hit from an EFP ?

The picture below is for comparison and shows what happens if you are hit from US fine calibre munition and splinter.

If you are hit by an EFP the same thing will happen as if you are hit from a cannon.

Someone hit from a 25mm calibre automatic cannon   (. . .accurate up to 2.5 km . . .)

Anyone hit by an EFP and surviving will never go back to work again. The limb is off, and can't be repaired.
Everyone surviving will cost a million dollar in medical aid, while a dead soldier cost 50 dollar for a coffin. The resistance win more on mutilating the enemy instead of killing.

A clue :
When you read about wounded enemy troops after an EFP attack then it's not as harmless as it used to be.

Designing Explosively Formed Projectiles

Explosively formed projectiles (EFP) have been used to defeat armored vehicles for more than 30 years. The EFP warhead was derived from the Misznay-Schardin device, which consists of a right circular cylinder of explosive, with a shallow cavity in one end that is fitted with a thin metallic liner. Upon detonation, the liner dynamically transforms into an aerodynamic projectile traveling at high velocity (typically 1500-2000 m/s). Figure 1 shows the formation process for a tactical EFP warhead from its initial predetonation state to the fully formed profile.

1  The shape of the liner.

The geometry of the liner's bottom surface primarily affects the velocity of the liner as a function of radius early in the EFP formation process. Making this surface too concave will cause the liner material to be driven inward more than desired. Making this surface too flat will result in a broad, flat projectile.

         
Two different types of EFP projectiles.

2  The thickness of the liner as a function of radius.

Altering the geometry of the top surface of the liner (defined by a second-degree polynomial) relative to the bottom surface changes the thickness of the liner as a function of radius. This changes the mass distribution and strength of the liner across its radius. These effects determine the shape of the liner late in the EFP formation process. While the explosive charge accelerates the liner, the center begins to move with a greater velocity than the outer edge. During EFP formation, the material near the outside edge of the liner slows the material near the center of the liner. This process produces a tremendous amount of strain in the liner. If the liner is made too thick towards its outer edge, localized strain will cause the metal to fail, resulting in metal chunks instead of an EFP. Making the liner too thin will cause the same problem. A correctly designed liner balances the competing effects.

3  The explosives / liner thickness ratio.

The thickness ratio between the explosives layer and the liner determines the projectiles velocity.
And also affects the strain during the EFP formation process.
It also depends on type of explosives used.

4  Shaping the detonation wave propagation

The arrows in the picture below show the delay time between when the detonation wave reaches the center and when it reaches the outer edge of the liner, for three different flat liner locations.
The delay time (arrow lengths) and arrow directions also represents strain that can break the liner apart.

Some types of shaped charges have elongated explosives layer or use explosive lenses combining two layers of different types of explosives. Or other smart solutions for shaping the detonation wave.
But since most EFP designs works well without that I think you can save your time.

Also remember that big air bubbles in the explosives can destroy the shape of the detonation wave.

(The blue thing in this picture is the blasting cap.)

5  Creating fins

At longer distance do you need fins to stabilize the projectile.
But this is not necessary for roadside bombs at distances of perhaps 20 meters.
At distances of more than 100 meters the projectiles drift off in "banana" bent paths becomes visible, which you can cancel by adding "canted" fins that makes the projectile spin like a rifle bullet. (Turn the fins a degree.)  (Not necessary if the target is big like a house.)
You can create the fins by shaping the detonation wave with obstacles or slow down the acceleration at specific points of the liner by adding mass (weight, pieces of metal chunks) . See the picture below.

(Also see patent : 5365852 at the bottom of this page, about creating fins.)

Note the metal fragments on the picture to the left side. Textron EFP
Also note that the liner looks like being cone shaped instead of dish shaped.

Accuracy as function of spin rate.

Aerodynamic stability

EFP liners can be made of circular plates or made of steel bars. And the main difference is that the circular liners creates conetailed aerostable projectiles while steel bars creates unstable projectiles.
An aerostable projectile will always hit the target perpendicular with its nose first. And a perpendicular hit always gives maximum penetration in the target.

The projectiles penetration cabability is proportional to the projectiles lenght in the direction of the movement.

The penetration depth depends on the impact angle. And the maximum penetration is at a perpendicular impact.
An aerodynamically stable projectile will adjust itself. While simpler EFPs made of a bent steelbar perhaps will rotate like a boomerang.

Some extremely long stretched circular EFP designs have no cone tail and is also broken up into multiple fragments, and have no aerostability, and can only be used at short to medium distance.

A simpler EFP made of a steel bar is easier to build, and the aerodynamic instability will not affect the impact angle at short roadside bomb distance.

MEFP
Multiple_EFP is an EFP with a special liner with many small dishes.
It launches many small projectiles from the same blast.
Useful against light armoured targets.

Platter charge

Is an easy homebuilt EFP built from a flat steel plate with plastic explosives attached to one side.
The disadvantage is that this weapon will give a broad short projetile that is more optimized for demolition of buildings instead of armour penetration.

If the projectile isn't aerodynamically stable then this is a short to medium distance weapon.

The countermeasures against RPG does not work against EFP.

RPG  Rocket Propelled Grenade is no big threat says the U.S. military even if it can punch a hole through 30 cm armour steel, because the countermeasure is too easy.
But they worry about the EFPs because it makes their road transports vulnerable and is a big threat to the entire occupation.

The U.S. and British military are hanging empty metal boxes and "slat_armour" (metal bars) and chicken wire on their vehicles, to predetonate the RPG-7 grenades.
RPG-7 is a jetting weapon and is neutralized by predetonating at a relatively short distance from the real armour.
It's not possible to neutralize EFPs that easy because EFP is a projectile, not a jet.

Slat armour on a stryker, protecting against RPGs.( a jet weapon)
But it does not protect against EFPs

EFP from the news
Advanced roadside bombs

IED Blows Up British Army's Main Battle Tank;
23 April 2007 BBC NEWS

A British Challenger 2 tank has been penetrated by a roadside bomb in Iraq, leaving the driver seriously injured, the Ministry of Defence has confirmed.

NBC News  Dec. 8, 2006

BAGHDAD, Iraq - Of the many dangers lying in wait for American soldiers in Iraq, the U.S. military increasingly fears one thing: the new, advanced roadside bombs planted by insurgents.

"There are very few things we fear," says Col. Douglass Heckman. "When a simple roadside bomb goes off, it's not going to kill us most of the time. A sniper can't penetrate  -- we keep the gunners down --  small arms can't penetrate. ... In fact, a vehicle-borne suicide bomber typically isn't going to hurt us. The thing that scares us is the advanced roadside bombs."

Heckman's teams of military trainers embedded with the 9^th Iraqi Army Division have reason to be wary.

In their sector of Baghdad east of the Tigris River, at least five U.S. military advisors have been killed by roadside bombs in the last two weeks -- among them the first full colonel killed in combat in the war and two lieutenant colonels who died in the same vehicle.

Unlike regular roadside bombs, EFP's -- explosive-formed penetrators -- remain intact as they explode. The steel tubes with curved metal seals form a kind of super bullet that can go directly through a tank's armor.

Little defense

The new, more lethal shaped charges are behind most of the attacks that often kill several servicemembers with one blast. Eleven U.S. troops were killed on Wednesday, making it the deadliest day this year. Five of those servicemembers died in a single roadside bomb attack  near Tikrit, the military said.

 
Homemade EFP liners and an EFP found in Iraq.

It's obvious that these are not factory made in Iran, but simple sewage pipes or lamp-posts cut in a garage in Iraq.

Only a small fraction of the roadside bombs used in Iraq are explosively formed penetrators. But the device produces more casualties per attack than other types of roadside bombs, the paper noted.

NYTimes August 8, 2007

The devices, known as explosively formed penetrators, were used to carry out 99 attacks last month according to American military officials.

Of the 69 members of the American-led forces killed in action in July, the lowest toll in months, 23 died as a result of attacks with the devices, according to data supplied by General Odierno?128;™s command. Of the 614 allied troops who were wounded that month, 89 were hit in penetrator attacks.

Though explosively formed penetrators account for a small fraction of roadside bomb attacks in Iraq, they cause a disproportionately large number of casualties.

Many of the penetrators faced by American forces are difficult to counter. Because they fire from the side of the road, the militants do not need to dig a hole to plant them, making them well suited for urban use. Because they are set off by a passive infrared sensor, they cannot be thwarted by electronic jamming.

1200 roadsidebombs each month but only 99 of them are EFP's

The EFP's Killing efficiency :
99 attacks with EFP in July 2007 kills 23 and wounds 89.
Means 23 % killing efficiency.

Compare to the other types of roadsidebombs which have less than 4% killing efficiency.

Patents on EFP

Drawing from patent : 5033387    Typical EFP shape

 
Patent : 5365852    How to create an EFP with fins.
A thin cross shaped foil between the liner and explosives.
The patent does not tell what the foil is made of, but it says about 25% of the liners thickness.

You can also create fins by placing pieces of metal in front of the liner to slow down the acceleration. Textron EFP with a cone shaped liner instead of a dish shaped.

 
Patent : 4649828    The liner is cut to create Multiple EFPs.
Clothes-pin shaped projectiles.

Not usable by the resistance because it's too complicated, but it gives a clue about an easier way to build EFPs.

Patent : 6606951   EFP antiarmour mine

http://www.freepatentsonline.com   download the pdf-files

A possible easier way to build EFPs

The resistance consist of amateurs which most of them are unskilled in using tools or shaping EFP liners. Which means that if a a weapon need to much work then noone will build it.
And they will rather waste 1000 kg of explosives on a big bomb for the ears and eyes that won't kill anything.
What you need is a simplified EFP construction and it's the liner that must be simplified.

You can't find circular dish shaped liners ready to use anywhere, you can't buy them.
But you can find steel bars everywhere.

The clothes-pin shaped EFP from patent 4649828 tells us that there might be an easier way to build EFPs.

Clothes-pin EFP from patent 4649828

Simplified Improvised Multiple EFP  SIM-EFP

At shorter roadside bomb distance there is no need for any aerostable cone tailed projectiles, which means that the liner can be simplified.

A SIM-EFP is built of simple cut and bent steel bars.

A SIM-EFP is a construction that fits in between the linear cutting charge and the platter charge.
And the main difference is how much the rectangular liner plate is bent. See picture below.

A simplified EFP has a thicker liner and thicker explosives layer.
If there is any trouble with breaking up in fragments then try a thicker liner plate or a rounded back.

Thumbrule :
The penetration in armor steel is the same as the projectile length.
Which is half the length of the steel bar.

No trouble with timing differences anymore
If using multiple ordinary EFPs in parallel, then it's necessary to use a single blasting cap and equal length explosives filled tubing to cancel the timing differences that can destroy or aim some EFPs in the wrong direction. But SIM-EFP doesn't need any explosives filled tubing, because the entire construction is collected together in the same unit. This is timesaving when planting the EFPs.

The SIM-EFP is by it's construction optimized for killing armored vehicles.
Because it launches a swarm of projectiles that are perfectly spread out for killing vehicles, and also projectiles that are optimized for armor penetration. See picture below.

A perfect spread out swarm of armor penetrating projectiles.
Everyone inside are hit, and noone will survive.
Longer timing error allowed.
Easier to kill fast moving vehicles.

Conclusions :
The SIM-EFP is a weapon that are easier to build, which means improved production. Easier to plant and more effective and timesaving at killing armored vehicles.

When the production of EFPs becomes too easy, then it will become the standard weapon instead of a rarely used special weapon. And that will improve the resistance's striking power and killing efficiency and force the enemy to abandon the roads.

EFPs are 6 times more effective than the big bombs at killing the enemy.

Trouble ?
You have to do some experiments about the optimal shape of the liner and explosives layer.
Make sure that the liner doesn't fold forward or get any other bad projectile shapes.
Try different constructions against a concrete wall and use the construction with the best penetration capability.

Try evaluate the design below, because it is so powerful that it will change the battlefield if it works.

Heavy tank killer ?

A simple bent steelbar with explosives attached.
Maybe a rounded backside profile to prevent the breaking up in fragments ?
Or a round profile ?

With this it's too easy to build a weapon launching a projectile half a meter in length. The penetration in armour is almost the same as the projectile length, which means that it can penetrate a heavy battle tank like Abrams or Merkava from a side attack.

It's flat design also makes it easier to hide in the terrain.

See the picture below that shows a circular and a flat EFP side by side.
Which one do you think is the easiest to hide in the terrain ?
If you have to dig it down ?

It's easier to create a long rod projectile from a flat EFP design compared to a circular EFP design.
Because it's easier to cut and bend a steel bar than it is to build a one meter diameter dish liner.
And perhaps the steel bar doesn't have to be bent at all (compare to a platter charge) which makes it a lot easier.

With this design you are not limited to attacking the heaviest tanks from the top or bottom anymore. You can kill them from a side attack.

An Abrams tank have a side armour at the lower part of 2 - 3 layers of 2.5 inch armour plates, which means about 7.5 inch (20 cm) armour steel, if you do not hit the tracks and wheels. The EFP projectile should be 20 - 25 cm in length to penetrate which means a steel bar of 40 - 60 cm in length.

Circular EFPs of that size are difficult to build. Which means that if you want a homebuilt heavy tank penetrator then you must abandon circular EFPs and try a flat EFP design.
Ask any expert in the workshop and they will agree.

If you got nothing else then take a railroad track. Send it like a projectile through the enemy's tanks.

Flat EFPs are only useful at short and medium roadside bomb distance because they are not aerostable.

Improvements :
Try weld the steelbar together with an aerodynamic shaped tail. Do your own experiments.

The flat EFP design is also an argument for redesigning nuclear powerplants because it's easy to build at home a weapon launching a projectile straight through a nuclear powerplant.
If you haven't learnt anything from Tjernobyl or the WTC already then there is no hope for you.
The reactor itself should be placed underground 10 to 20 meters below the surface in a safe nuclear powerplant design. That will also protect against airplane attacks. Another lesson from Tjernobyl is that they had to dig the reactor down after the disaster, so why not save some time and have it dug down before any disaster.

Very big homebuilt efp

Some home built EFPs found in Iraq.
The EFPs made the US lose the war on the ground, and they were forced to abandon the roads and begin bombing an invisible enemy from above. Which explain the increase in aerial bombings of what they call suspected insurgents, which means innocent peasants, women and children. And later they had to recruit puppet troops to do the dirt work on the ground in order to survive and improve the US statistics of killed troops.

The EFPs were abandoned by the Mahdi resistance because their leader the chicken Mr Al-Sadr stabbed the resistance in the back and told them to lay down their weapons and not to fight the enemy. And he prolonged the US occupation with many years. What a hero.

Demining machines and weapons.

What they all got in common is that they are all useless against EFP because the EFP strikes from a side attack.

Most of the resistance's big bombs are too easily neutralized with the tools below.
So much work and money lost.
And they must start using EFPs if they want to kill the enemy.

This machine below whips the ground with chains with heavy force and detonates the mines.
But it's useless against EFP.

The mine roller blows up the bombs, and only the roller is damaged instead of the entire vehicle.
Easy repaired.
But it's useless against EFP.

The mine plow digs up the mines and creates a safe passage for tanks and troops.
And it's useless against EFP.

Ground penetrating radar and a computer memory is used to save a record of what the road looks like for many miles. If anything has changed since last then there is a bomb.
And it's useless against EFP.

The robot arm and the remote controlled tiny machine in the picture below is used to undig bombs at safe distance away from
And it's useless against EFP.

The MCLC and other similar antimine weapons.
A 100 meter long hose filled with explosives is laid out with the help of a rocket.
It will blow a 100 meter long and a few meters wide passage through a mine field.
And it's useless against EFP.

http://thebrigade.com/2011/01/04/theres-nothing-like-a-high-res-explosion-from-a-mclc-18-hq-photos/

The main disadvantage of EFPs is that they must be remote controlled.
Or else you must try build a dual microphone electronic device that listens to the sound of the vehicles in the air or in the ground, and then detonates the EFP. Or try build an extremely low power IR tripwire.

The difference between a point weapon and line weapon

The big bombs are a point weapon, which means that the enemy is safe as long as he keeps himself away from the killing point. And the enemy can stop their vehicles at a safe distance and send in the remote controlled robots to check for bombs. And try to disarm the bomb.

EFPs on the other hand is a line weapon, a cannon. And there is no safe distance from a cannon.

More advantages of line weapons :
If you intend to block the enemy's traffic on a hundreds of meters wide battlefield. The the EFP is more economic and also harder to neutralize.
A single EFP can cover a width of hundreds of meters.
If you instead use ordinary antitank mines, then must you plant hundreds of mines side by side to do the same job, which becomes more expensive.
It's easy to create a safe passage through an ordinary minefield. Typically with an explosives filled tube that predetonates the mines, or with a mineplow. You can't neutralize an EFP with the same simple methods because the EFP is not located where you intend to drive.