There are many reasons why you might feel the nicotine. If you smoke very slowly, for instance, you might be getting it in such small doses and spread over such a long period of time that you don't feel it. Another reason, of course, might just be that you're not very sensitive to nicotine. Also, the absorbing nicotine is supposedly highly dependent on the PH of both the smoke and your mouth. It might be that, say, drinking some orange juice with you pipe might up the amount you absorb.
I don't feel that Royal Yacht is all that powerful, but I'm surprised you didn't at least feel a tingle from Irish Flake. Of course, I don't consider either of them to be real heavy hitters. The blends that have made me (a nicotine addict of the first order) a bit queasy are the two Dark Flake iterations from GH, Coniston Cut Plug, 1782, and Billy Budd (some people don't find Billy Budd too strong, but it knocks me on my butt). You could also try Old Joe Krantz, which is my favorite "all day" smoke. Some guys feel it's overwhelmingly strong, but I think it's perfect.