While I'm adding bodywork, I'm also adding some side impact protection.
The “pontoons” (back in the day, that's what they called the side thingies that go between the front and rear wheels so the air doesn't have to go around wheels twice) could be completely hollow, and if I were making a race car they probably would be, but out on the road, where people go all kinds of funny directions and some of them have big clumsy cars to hit you with, I decided to sacrifice some lightness and add some structure between the cockpit and the outside world.
I researched a number of materials. Urethane foam was one thought (it's what R.Q. Riley uses on his XR3, (see MAX Update No. 5) and a number of production cars use expanded styrene under their bumpers and door panels (an industrial strength version of the stuff that cheapo picnic coolers are made of). I even considered rubber bubber beegle beebers ... reeble beeble buggle bungers ... but it turned out to be so hard to pronounce that I gave up on it.
Instead I decided on yet more steel tubing, like the rest of the frame is made from. There were lots of reasons, mostly boiling down to it's what the car is made of already. Why does that matter? Well, for somebody building a MAX replica, it saves them from finding new materials and changing skill sets in mid-build, and it integrates well with what is already there, and it will collapse and bend in concert with the rest of the chassis in the event of an accident.
Another nice thing about working with welded steel tube is, I can tell how much weight it will add without even having to touch it, all I have to do is look it up. Let's see, 1” by 0.065” wall square steel tubing weighs 0.83 pounds per foot, the 7/8” diagonal braces weighs 0.68 pounds per foot, the 1” round 0.049” triangulation tubing weighs half a pound per foot ... this sidebumper structure will add 9 pounds per side when I'm done. Whoa, how am I going to make that up?
Actually, I have a plan to compensate for the extra weight, and I'll share it with you soon.