This is the start of the thrust duct.  Using 1 sheet of 2" foam, I've cut 2 arches and glued them together forming one long one.

    Here's the hotwire I made to cut a bevel in the foam.  When wrapped around the form, it'll create an airfoil shape

    More sanding.  You can see the airfoil taking shape.

    To aid in bending the foam around my duct form, I cut slits about every 1" or so using a regular hand saw.  To control the depth of each cut, I've drawn a line on the saw 1 1/2" up from the teeth.

    Using ratchet straps, I epoxied the foam to the inner plywood ring which is nailed to 2 plywood disks which hold the ducts shape until attached to the craft.

    No, I didn't cut the foam too short.  I left a gap there to help attach the duct to the hull.  If I hadn't left a gap, I'd have to cut a flat spot on the bottom.  After doing this to 3 other ducts, I decided a gap would be easier!

    My brother holds the duct in place to give me an idea of what the craft will look like!