Looking for the subject of an infinitive phrase

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.

Answer

The subject of the infinitive phrase is the entire phrase "with an inflatable.....with separate smaller ... to the main bladder".

I'd change "to form" to "forming" and set that "with...with..." clause off with commas, and stick in an "and".

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 and with separate smaller bladders that are perpendicular to the main bladder, to form forming the chord or foil of the kite.

But if given free reign (or even free rein), I'd put a full stop or semicolon after polyester and start a new sentence|independent clause.

P.S. With respect to the question is it grammatical -- No, it isn't. "to form" requires an antecedent clause with a transitive verb. These are grammatical:

We put a thingamajig here, and a whatchamacallit there, to form the gizmo.

It has a thingamajig here, and a whatchamacallit there, forming the gizmo.

It's got a gadget, with a thingamajig and a whatchamacallit, forming the gizmo.