Originally Posted by aeajr
It seems unlikely that Selig would produce two airfoils with the same numerical designations, one S3021 and one SD3021.
If you read the paper at the link, authored by Selig, you see that he refers to it as S3021. Since he designed it, I think I will go with his designation.
Not all of his designs were done with Donovan. Again, if you look at the paper, authored by Selig it is co-authored, not by Donovan, but Ashok Gopalarathnam. Copyright 1997 by Michael S. Selig and Ashok Gopalarathnam
Thus you the
S3021 - Designed by Selig
SD7037 - co designed with Donovan
SA7035 - co designed with Ashok.
How did I know this? I didn't. I went to learn about this SD3021 airfoil cited in the specs for this glider and found out there is no such aifoil. It is a mistake, unless Horizon went back to Selig/Donovan and had them design a new aifroil for this glider.
I doubt HH got a re-designation.
It appears somewhere way back the 'D' got slipped in & has been used by other kits & designers since then.
It was covered in 2005 per: