Thanks for the great answers and ideas. I am not looking to have the wife take one for the team. I love sex but if all I wanted was sex with different partners and my wife was unwilling to play, then I would get a hooker or find someone(s) to cheat with. Since I don't do that I am really more interested in us, her and I, exploring life together.
Since she is saying "no" pretty clearly, I am looking for ways to stop thinking about this as being something that could be fun and find a way to accept her answer, even though right now I think she might want to say yes but is afraid. I'm thinking "get another hobby" is the way to go. More nudism plans, maybe convince her to take up tennis or golf (she hates tennis but is ok with golf). I realize she is not being clear about why she is saying no and I would love to understand that and maybe if I give her 100% guarantee thing she will tell me eventually.
Other ideas for dropping the idea or will this always be an issue for us?