The Dyke Delta was designed and built by John Dyke and first flew in 1966.
They do show up often at Airventure and SNF to help breakup the conformity of RV’s.
An excellent write up on the history of the aircraft can be found on the EAA web site, written by Alan White
The structure is mostly 4130 welded steel tube
EAA Chapter 27 in Meriden Connecticut has a good collection of construction photos (including the photo above)
For the RC community, legendary RC aircraft deisgner Laddie Mikulasko created a set of plans that can be found on Outerzone.