818R Side Impact Solutions

[Santiago]

Hey All! I thought it would be good to collect the side-impact solutions from different folks. So far this is what I've seen:

Plavan: 1/8" thick 7075 aluminum sheet (T7 temper)
Mulry: steel plate (didn't see the thickness)

Other options:
Impaxx foam (https://www.rollbarpadding.com/product/id-69) - thanks Bob for the site and suggestion ("For a door I would look at 24" x 40" x 4"thick $200")

I think the best solutions will involve an anti-intrusion panel + impact foam. So...

Me: 1/8" thick 7075 aluminum sheet (T6 temper, very similar to T7, slightly lower elongation %, less expensive than T7), coupled with this (2006-2007 Impreza FRONT pad):

50449

I figure if the OEM's use this to mitigate front end impact, then it should be a suitable foam for me. In hunting around for this I found a wide variety of thicknesses, so I went with the thickest one I could find (4.25") that didn't have too much bow in the backside. The idea is that mounting it will be tons easier if the backside is relatively flat. I'm going to sandwich it in a composite sleeve and bolt that to the aluminum panel at the height of the main upper door bar - something like this:

50450

I'll trim the quarter panel to move the pad further back so that the thickest part is in line with the driver. [Also note that the aluminum shown here is not the 7075 sheet I'm using.]

As an added bonus, this puts the foam at the same height as most bumpers (i.e. same plane as the upper half of the wheel/tire). You can pick these up from your donor car if you've got a 2006 donor or you can get them on the cheap from scraped cars. Cost: $50 ea. (shipped). I got two since I'm a firm believer that the passenger should be as well protected as the driver (years of instructing has sensitized me to the shoddy consideration often given to the poor bum riding shotgun). You could also double up on one side if you wanted more vertical protection.

FWIW, these are some notes I have on a range of OEM options for others to consider:

Subaru Impreza (2006-2007) FRONT pad - very flat along backside, quite thick
Subaru Impreza (2004-2005) FRONT pad - very flat along backside, modestly thick
Subaru Impreza (2002-2003) FRONT pad - pretty flat along backside, bit curved, decently thick w/recesses

Ford Focus (2000-2004) REAR pad - fairly flat along backside but ends taper in, decently thick
Scion Xb (2008-2013) REAR pad - curved backside but flattens out easily - bit thin though
Infiniti G35 sedan (2007-2008) FRONT pad - curved backside, looks to flatten easily once ends are cut off - tick thicker than Scion pad

Hope this spurs some folks to share their side impact solutions. I think those of us with wheel-to-wheel interests would benefit from sharing the pool of knowledge.

Best,
-j

[Mitch Wright]

Really interesting approach that I think has legs.

[FFRSpec72]

Impact is different than intrustion, I wanted intrustion protection so I used 12 gauge steel, the reason I did not use aluminum (as it would have been much lighter) is that elasticity of the steel is much better. I have been t-boned on the track in my challenge car @ 70 mph and I know the 12 gauge works, as it distributes the impact load to the frame. I had no frame damage, just fiberglass and the car that hit me need a entire front clip

50458

[Santiago]

Agreed, impact and intrusion are distinct concerns. That's why I prefer two complimentary devices.

I think the aluminum will also do a good job of spreading load over the entire door-bar area if it is properly tied into it. What it definitely won't do as well as steel is withstand a sharp penetrating object. Hard to match good old fashioned mild-steel for that. I'm not a mechanical engineer though, so take my thoughts with a grain of salt.

Best,
-j

[RetroRacing]

We bought the Nascar stuff, will post pics when installed.

[Mulry]

I'm using .063 sheet steel as the anti-intrusion layer on our 818R. We will weld it directly to the side of the cage/chassis and then will likely fill the space between it and the outer door skin with Impaxx foam. Look forward to seeing how it fit for RetroRacing though. Here's what it looks like cleco'd to the chassis:

52968

[RetroRacing]

55734

Nascar impact foam. expensive but lighter than any other option we could find.

[Mulry]

Is that the Impaxc stuff? Did you get it from the rollbarpadding link above, and if so, how much did you need to buy to fit that door skin?

[RetroRacing]

BSCI, Inc.
170 Barley Park Lane
Mooresville, NC 28115 USA
Impaxx 700, we used one full 4" X 24" X 30" sheet per door, but could have used closer to a sheet and one quarter, but at $150 per sheet, we only fully covered the back 3/4 of the door.

[Zach34]

Are these anti-intrusion panels prevalent in fiberglass-body race cars? Is anybody aware of rule-book requirements for them in NASA/SCCA?

I had flat 7075 plates just like Chad Plavan installed, but my significant roll cage modifications on the driver's side have ruled out the use of a flat plate. The 7075 aluminum will not bend, but it's nearly as strong as steel so I'm inclined to use it. I can make several small plates to cover the contours of the new cage structure, but that will be a lot of work.

I'm mainly just curious if this is something you guys have seen on a lot of racecars, granted it's probably not needed on a steel-body car.

76829

76830

[Sgt.Gator]

Are these anti-intrusion panels prevalent in fiberglass-body race cars? Is anybody aware of rule-book requirements for them in NASA/SCCA?

I had flat 7075 plates just like Chad Plavan installed, but my significant roll cage modifications on the driver's side have ruled out the use of a flat plate. The 7075 aluminum will not bend, but it's nearly as strong as steel so I'm inclined to use it. I can make several small plates to cover the contours of the new cage structure, but that will be a lot of work.

I'm mainly just curious if this is something you guys have seen on a lot of racecars, granted it's probably not needed on a steel-body car.

76829

76830

Anti-Intrusion panels are not required by SCCA or NASA.

[C.Plavan]

As Gator said- No rules. More piece of mind and just plain safety. When you are racing with huge monster Corvettes and other cars, you will feel funny even with the side protection in place. I could not imagine it without.

[Zach34]

I started to model the anti-intrusion plates. I still have 2 more to go, but this is a good representation of the challenge ahead. I would be able to cut them out on a cnc plasma. I modeled the top/forward one with 3 separate bends of 12 degrees to make the curve with the tubes. I doubt the 7075 would even bend that much. I could make that one out of 6061, I suppose. Here's what I will have to do:

-transfer the 3D model to 2D vector files for the plasma machine
-cut the panels out
-make bends in the 2 panels that will need them
-somehow clamp each panel in place, one by one, so I can position mounting tabs to be welded on the tubes (not modeling those...)
-finish-weld the tabs
-position, mark and drill mounting holes in the panels for the tabs

That's a lot of work. I guess the fear that's motivating me is of the fiberglass shattering/splintering and sticking through the frame tubes in a side impact. I don't know how likely that is, though. Plus, due to all the various angles and bends in the tubes, I will end up with a 1/16 to 1/8 gap between all the anti-intrusion panels and the tubes. Hard to say how much that will compromise their effectiveness.

76837

[Sgt.Gator]

Zach, I re-read your build thread in light of my 6 month journey down SCCA/ICSCC tech inspection path. Probably in NASA you'll be ok with your changes to the driver's side frame/cage. If you were looking to race in SCCA I would be concerned about them allowing the mods you've made. Right now SCCA/ICSCC considers the 818R a Sports Racer, not a Production car with an additional cage structure. They don't like to see changes to the basic structure of the frame. Additional tubes for more safety are generally ok, changing the frame is not, but even then they get worked up. For example I'm adding a front hoop/halo to my 818R, the ICSCC is requiring that I get an engineers drawing with a stamp before making the change. On my Palatov D4 the SCCA is requiring the same thing to increase the height of my main hoop, and that will end up being homologated by Palatov for all their future tall customers. I'll probably apply to the SCCA for homologation of my front hoop/halo change too.

You could contact NASA Tech or the regional ST director and submit your change drawings to them for approval before you get too much farther down the road. You sure as heck don't want to do all this work and show up for tech and have them deny you. I know the feeling too well, I added a roll hoop to my D4, went to a race, and both the ICSCC and SCCA tech inspectors said no, go get approval from SCCA HQ Tech. OTOH if you get your car thru NASA tech and they don't say anything about the frame change and give you a cage stamp, you're good to go.

[Hobby Racer]

That's a lot of work. I guess the fear that's motivating me is of the fiberglass shattering/splintering and sticking through the frame tubes in a side impact.
76837

If you are only concerned with fiberglass shards etc. have you considered a kevlar ballistic blanket? Its flexible, light and will stop any projectile from entering the cabin. It could be wrapped around the the side tubes and be easily removable.

Just a thought.

[Zach34]

Hobby, good idea. I'll look into that.

Gator, great points. I've been following your build. I have zero race experience, so I'm going to go through a autox -> track day -> race-school-of-some-sort progression over at least a year or two before I go through tech at a NASA event (thinking ST-2). I figured I was taking a risk on tech approval by making the changes, but to me it will be worth whatever additional hassle comes from it. I'm just shy of 6'3" and 180 lbs - not extremely tall and pretty normal-shaped - and I simply did not fit in the car. I had to re-structure the floor to pass the broomstick test (it's still a little close), and I simply could not freely steer the car with my left elbow jammed into the roll cage.

I threw the seat back in for a test fit with the new side-structure. It's even nicer than I thought it would be and totally worth the effort. There is SO much more room and it feels safer having at least a little bit of distance between my arm and leg from the roll cage.

Luckily, from what you've posted, I now know I should tentatively plan on seeking official engineering approval before trying to get into an ST-2 event. If I have to change more stuff, so be it. My main concern is a safe, driveable car.

[Sgt.Gator]

You won't have any problems at autox -> track day -> race-school as long as you pass the broomstick test. It's when you try to get a cage stamp for TT or wheel to wheel that they get out the rule book and read it to you, with their interpretation of the rules which may not be the same as yours!

[Blu]

BSCI, Inc.
170 Barley Park Lane
Mooresville, NC 28115 USA
Impaxx 700, we used one full 4" X 24" X 30" sheet per door, but could have used closer to a sheet and one quarter, but at $150 per sheet, we only fully covered the back 3/4 of the door.

Retro, why did you choose the 700 and not the 300 or 500? I want to order this for my build and could not decide which was the right one. Tech support would not help as they did not want any liability as to which one I selected. I know Nascar mandates this on both sides.

[RetroRacing]

I don't know the difference, we just randomly chose the 700

[Sgt.Gator]

This is interesting but doesn't answer the question of which IMPAXX foam: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.459.723&rep=rep1&type=pdf

Although this graph may help:

100738

The 700 seems to be the "best". I don't know the weight differences.