Safety Net: Window Net Install SFI Edict With Chassis Engineering


It has become a right of passage to be told by a track official “don’t come back without a helmet and a roll bar.” It means you’ve finally pushed your vehicles’ performance high enough to warrant some additional safety measures in order to race. While it might put a smile on your face, safety is an absolute necessity that has been woven into the fabric of drag racing. Working hand-in-hand with the SFI Foundation, the NHRA has over the years developed a set of safety standards when it comes to race car design, safety products, and apparel, and if they say you need it, chances are you probably really need it.


A window net is designed to keep the drivers’ head and arms inside the car in the event of an accident.

America got an excellent illustration recently of why window nets are a necessity in a race car, on national television, when comedian and talk show legend Jay Leno went for a wild ride with Bob Riggle in the Hemi Under Glass on the show Jay Leno’s Garage. Without this key safety feature in the passenger side of the car, one of the world’s most beloved comedians nearly lost an arm, when the iconic Barracuda came crashing down on the passenger side of the car during an exhibition wheelstand for his show. Of course, far worse crashes occur every weekend at the dragstrip, and the addition of a window net will drastically improve your overall security in the car.


The buckle that will keep the entire assembly tight was stripped of its chrome finish before being welded to the upper window net rod.

The difference between a standard cage net and a Funny Car cage is that a standard net needs to be 10-inches wide, while a Funny Car mesh is much smaller.” – Curt Perry

While Chassis Engineering has become a one-stop-shop for chassis and suspension components for drag racers, they also pride themselves on providing high quality NHRA-compliant safety products, as well. When outfitting our Project True SStreet, a street/strip fifth-gen Camaro, we turned to them to provide the essential window net kit that will ensure our fifth-gen Camaro will not encounter any hold-ups in the tech line. But, more importantly, providing an additional barrier between the driver and the unfortunate hazards that can arise during a pass down the 1/4-mile.

But, before you decide to upgrade any features you should always consult you governing bodies’ rulebook, to ensure that you don’t have to revisit a portion of the vehicle in order to conform to the required standards.

The 2015 NHRA’s regulations on window nets are as follows:

An SFI 27.1 ribbon-type or mesh-type window net is mandatory on any full-bodied car running 7.49 (*4.49) or quicker. For full-bodied cars running 7.50 (*4.50) to 9.99 (*6.39) or if vehicle runs 135 mph or faster, a ribbon-type or SFI 27.1 mesh-type window net is mandatory unless otherwise specified by Class Requirements. SFI 27.1 window net, when required, must be updated at two-year intervals from the date of manufacture. Window net must be securely mounted on the inside of the roll cage, with the permanent attachment at the bottom. All attachment points must be designed in an attempt to protect the driver and avoid contact with track surface or guardwall. Eyelet clips, dogleash hardware, hose clamps, etc. prohibited. Penetration of webbing, except as performed per manufacturer’s instructions, prohibited. Any other modification to net must be performed by manufacturer.
*= specifies a 1/8-mile e.t.


Notice how this Funny Car cage window net is drastically smaller than a standard piece. This is due to the decreased area of the window not already protecting the driver

After consulting the NHRA rulebook we reached out to Chassis Engineering to acquire an SFI approved window net kit. While we used their standard window kit (PN:C/E4033) during our install, Chassis Engineering also has a Funny Car cage window kit (PN:C/E4031). Both of these kits supply all the hardware you’ll need to perform an NHRA approved window net install, minus the window net mesh which can also be purchased on through their website.

“The difference between a standard cage net and a Funny Car cage is that a standard net needs to be 10-inches wide, while a Funny Car mesh is much smaller.” explains Curt Perry of Chassis Engineering.



The supplied rearmost lower tab, while acceptable for most applications, need to be replaced with a longer piece to ensure a tight window net fitment.

Installation was pretty straightforward on our Camaro, only requiring some minor modification in order to conform to our car. The first mounting tab was tacked into place, and was positioned to receive the upper window-net rod before the buckle tab and mounting tab were welded into the cage. Examining the lower mounting bar prior to welding the supplied tabs, the mesh window net is placed on the upper mount, which is then pulled tightly in order to securely gauge the necessary length of the lower mounting tabs. This ensures proper fitment. After fabricating another lower mounting bracket, the lower tabs are fastened securely to the down bar using a bead of filler rod.

The Required Testing


Definitions And Constraints For SFI Specifications 27.1

Window net: Window nets are used to contain the occupants within a vehicle during unusual attitude conditions. They are normally required in motorsport application when the driver side window or window area is open.

  • The useful life of the Window Net shall not exceed two years and must be replaced at or before that time.
  • Any window net pertaining to this specification shall remain as constructed by the original manufacturer and not modified.

Webbing: The webbing is the inner portion of the Window Net that is connected to the outer borders.

When it comes to window nets, there’s quite a bit of engineering that goes into making sure the mesh net is up to the task of keeping a driver safe, without obstructing his or her view. To gain their SFI 27.1 specification, an initial test and subsequent periodic testing are performed to ensure that the quality of these nets doesn’t waver.

During this testing, the window net mesh is subjected to both a penetration and rapid impact resistance. During the penetration test, a smooth steel ball with a diameter of 3.00 ±0.06 inches with a weight of 4.00 ±0.25 pounds is dropped from a height of 2.00 -0/+0.12 inches at the geometric center of the webbing opening. This test is performed a total of three times in the same location and requires the ball not to pass through the mesh in order to pass.


IMG_3813The rapid impact tests truly examine the resilience of the window net material during an impact. An impact bag constructed of leather that has a diameter of 10.00 ±0.25 inches at the bottom is filled with 175 pounds of “OO” or smaller lead shot pellets. This bag is then dropped from a height of 26.5 -0/+0.5 inches over the direct center of the net. This test is performed an additional two times and in order to pass this stringent test, the impact bag, first and foremost, cannot pass through the net. Other factors that result in a no-pass result are as follows: if more than 50 percent of any of the inner cross-section webbing joints pull apart, if more than 50 percent of the webbing ends seperate from the net border, or if more than 50 percent of the border meterial is ripped at the coader stitching.

Without organizations like SFI and companies like Chassis Engineering, the track would be a lot more dangerous. But if we all opt to take the knowledge and testing seriously, we can continue to make the race track a safe atmosphere for spectators and fans alike. Make sure to check out Chassis Engineering for all your upcoming chassis and suspension modifications and upgrades, and don’t forget to stay SFI compliant.

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About the author

Justen Spencer

Justen is a Ford modular motor fanatic with seven years of professional drag racing experience, and multiple championship seasons in NMCA West and PSCA. Originally from Las Vegas, he is the proud owner of four Mustangs, one that sees regular track time. When not racing, Justen can be found in the garage maintaining his championship-winning car.
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