Everyone has made one of these at some point! The tough part with tape measure yagis is getting the hairpin match connected to the tape. Soldering copper to steel is not easy. Just follow the instructions and get the dimensions right, it'll be close enough. A couple of issues ago QST had a story about a Boy Scout troop making them, so relax and don't worry.
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"They say the test of literary power is whether a man can write an inscription. I say, 'Can he name a kitten?'" -- Samuel Butler