Does partially intentionally wrong kavanah make a bracha a bracha levatalah?
If I put on my tzitzit and notice that a string is missing (or something else which would invalidate it as proper tzitzit) and wear it any, and then later, when I put my tallit gadol on, have in mind that the bracha should cover my tallit katan as well (as per the M"B's statement "And this is the custom nowadays, to make the blessing on the טלית גדול and have in mind to exempt with it the טלית קטן.") does the fact that I know that my bracha is intended to apply to something which cannot be covered by that bracha undermine the value of the entire bracha or is it still a valid bracha because I also have in mind the tallit gadol which is kosher?
Clearly, I'm not asking for a psak with the intention of doing anything like this but I want to understand the power of kavanah in determining the efficacy of a bracha.
