From an article on kiting:
Leading edge inflatable kites, known also as inflatables, LEI kites or C-kites, are typically made from ripstop polyester with an inflatable plastic bladder that spans the front edge of the kite with separate smaller bladders that are perpendicular to the main bladder to form the chord or foil of the kite.
As I understand, "to form the chord or foil of the kite" is an infinitive phrase (or clause). But what is its subject? What actually forms the foil, according to the sentence? The front-edge bladder? Or the smaller bladders? Or both? Is the sentence grammatical?
The sentence is also used in Wikipedia's article on kitesurfing.