Yep that looks like an HF antenna. Also from the looks of the sponsorship stickers all over his airplane, he is doing some long range stuff and you need HF out over the open ocean for communications.
Manuel made one of his around-the-world stops in Abilene, Texas. EAA Chapter 471 fed him, put him up for the night and fueled his plane before departing.
He was a most interesting and daring gentleman and it was a joy to host him while he was here.
Here's a pic of some EAA members with Manuel Queiroz. (I'm the goose in the blue shirt standing next to Manuel)
