The plastic is fiberglass. A lot of recumbents have fairings.
http://www.whatisafairing.com
In this case, Mellisa suggested the fairing be based on her Kenworth truck's spoiler.
And although the bike is of the type known as semi-recumbent, it's not because it looks like a semi.
The frame (the thing that looks like a 4x6 piece of lumber) and the fairing are permanently bonded. The 4x6 frame goes forward past the head-tube by about ten inches, which gives the handlebars room to turn.
The fairing is frame-mounted, not connected to the handlebars. The fairing has a bulkhead (Bulkhead is a term used in ship and aircraft construction, it means "wall") four inches high and set two inches in from the rear edge of the fairing. The fairing's bulkhead has a two inch lip on the top edge, so it is flush with the rear edge of the fairing. The 4"x6" frame has tapered to 4"x4" at the head tube, so it is butt-jointed to the bulkhead. Woven fiberglass tape and polyester resin were then applied, so the fairing is bonded to the frame.
The design of the fairing, as I said, was my Daughter Mellisa's idea.
I could call this a "quarter scale Kenworth", but building it was more of a sculptural exercise. Much of the work was done while I was in the Navy. I used an aircraft hangar at my Naval Air Station because the lighting is designed so aircraft mechanics can see what they're doing. I was able to sand the fiberglass to perfection because the overhead lights are staggered, top row sodium vapor and bottom row mercury vapor, so there were no shadows under the sanding block.
Whether you call it crank-forward or semi-recumbent , I am posting it here because the technique lends itself to building a recumbent. I posted some info about this bike in the "framebuilders forum".
I'll give you a hint, the first plug-mold was made of paper-mache' and plaster. I laid fiberglass over the plug-mold. When that hardened, I broke away the plaster with a hammer.
If I do this again, I will use polystyrene foam (styrofoam, building insulation board) and epoxy resin. Epoxy resin is four times as expensive as polyester resin, but it will not melt the foam.
BTW, I added aluminum powder to the resin, so in the second photo the unpainted areas (rear of fairing) look grey.