You may call yourself a rationalist, but that doesn't make the positions you espouse reasonable. In fact, for all their talk about reason and all their railing against blind faith, rationalists are often among the most irrational people.
Christianity claims there are truths which are beyond the power of reason to demonstrate, but that doesn't mean it's irrational. There's a difference between what is irrational (against reason) and what is suprarational (above reason).
Consider this. Quantum physics is above the reasoning abilities of most four-year-olds. Does this make it, even for a four year old, irrational? No.
Or think about this. To know everything there is to know about modern science is beyond the capabilities of any one human being. This is why we have specialists. Yet, we don't say that, because the totality of scientific knowledge is beyond the powers of one person to know, science is irrational.
In other words, the fact that a person is limited in what he can know doesn't mean there isn't something beyond that. If we move from an individual to the human race as a whole, we can say that the fact that there may be limits upon what man, as a finite creature can know, doesn't mean there aren't thing beyond what he can know.
Christianity claims to have a message from beyond man's intellectual horizon. It claims God (whose existence, by the way, is knowable even with our finite reasoning abilities) has revealed things which are beyond reason, but which don't conflict with it. It also claims that reality as we know it gives evidence, though not proof, that transcendental truths exist. Whether this is so or not, it's not an irrational position.
From the Christian perspective, the rationalist is like a man with a road map who, having found the map reliable in what is pictured, somehow concludes from this that only what is pictured is real. The rationalist thinks roads which go off the map go nowhere, but it's really rationalism with its blind faith that's a dead end.