I quilted a tee-shirt quilt this week for a client. I have done a few of these since I began longarming, and the quality of the shirt preparations seems to vary a bit from quilter to quilter. I thought I'd show this one and talk about how best to prepare your quilt so as not to stress out your longarmer (and to get the best quilting possible!).
Let me start by saying that this particular quilt was perfectly prepared. I had no issues whatsoever. Typically, the mere mention of "tee-shirt quilt" sends me halfway to the hills though. This quilt has 15 different shirts. The person that brought the quilt to me adopted the project from a friend of her's. She's not to blame for these shirts not really being cut squarely on each imprinting design. She went so far as to tell me that the initial person (who the quilt is eventually going back to) had purchased silk/poly gingham for the sashing. Oh, dear...
She clearly told her how inappropriate that was, and selected another 100% cotton fabric instead.
Next, you will need a lightweight fusible interfacing. It doesn't need to be fantastic, and shouldn't be overly thick. The shirts are already considerably thicker than the woven quilting fabrics, and the goal for any quilt should be to have all fabrics of uniform thickness. This enables the quilting tension to be maintained uniformly across the entire quilt. Apply the interfacing over the shirt (on the backside), and then cut out the piece to the desired size. It is fine for the interfacing to go into the seam allowance.