Taking the approach of using a manufactured trike as a chassis and building a fairing around it, Orin Peters has created several velomobiles using coroplast - a readily available and inexpensive material.
He's calling his most recent creation Hidalgo, built around a narrow track (approx 30" wide) ICE QNT trike, he has done quite well with it, even in races against commercially available machines. A previous machine consisted of a coroplast fairing around an ICE Sprint.
Here is Orin's website.
Here is a series of pictures of Hidalgo.
Here is a long thread on Bentrideronline in which he reveals build details.
And here is a Bentrider online thread having to do with some of his racing experiences.
