Claus, it's not so easy to answer that question.
It's been awhile since I read about the life of Jefferson, so I am sure that much of what I write below will be factually questionable. Nonetheless, it will make clear one thing - that the opinions of the founding fathers changed throughout the course of their lifetime, and thus it is not possible to make an unequiviable answer.
First, I think that at one point in the draft Jefferson penned "all men, black and white," and that this was excised during debates. Basically there was no hope in getting some necessary support with that phrase in the document. So he bowed to political reality.
In his earlier part of his life, Jefferson believed that slaves should be free, yet on their own land, separate from whites. Partly because he felt that society would not accept integration (and let's face it, we didn't get that together until the 1960's), and partly, I think, because of racism - presumed inferiority.
Jefferson, through his travels and through interactions with blacks at his farm, came to regard blacks as equals. This took a long time.
So how do we answer your question? Was the constitution written by the founders to allow slavery? Yes. Was that motivated by political considerations? Yes. Was there some inherent racism in the founders? Yes. Did that racism continue unabated? No. Did at least one founder (Jefferson) consider blacks equal to whites at some point of their lives? I'd say probably yes, within limits, at the end of his life, but not so much at the time of the authoring of the constitution.
I'm sure the better read posters among us can correct my historical blunders, but I feel my central point remains - this was a time of wildly shifting opinions about slavery, and the founders were not immune to it. Their opinions evolved, rendering yes/no answers an impossibly crude measuring stick of opinions composed of part intellectual argument, part deeply engrained cultural norms. I would be surprised if Jefferson ever wholly got rid of his racism at the gut level, whatever his intellectual position.