1. Combine yeast, 1 cup of the warm water and the sugar in a large bowl; stir until the yeast is dissolved. Let stand until mixture is foamy, about 10 minutes.
2. Stir remaining warm water, the oil and salt into yeast mixture.
3. Whisk together 7 cups of the all-purpose flour and the whole-wheat flour in a large bowl until combined.
4. Make a well in the center of the flour mixture. Add half of the yeast liquid to the well; stir into the flour mixture to blend. Stir in the remaining yeast liquid until a rough mass is formed.
5. Turn dough out on floured surface; this is a very soft dough. Knead until smooth and elastic, about 5 minutes, adding as much of the remaining 1/4 cup all-purpose flour as needed to prevent sticking.
6. Place dough in lightly oiled bowl; turn dough in bowl so all sides are coated. Cover bowl with towel or lightly greased waxed paper. Let rise in a warm place, away from drafts, for 45 to 50 minutes or until dough doubles in volume.
7. Grease three 9 x 5 x 3-inch loaf pans.
8. Punch dough down. Turn out the dough onto a lightly floured surface. Knead lightly. Divide into thirds. Place one portion in each of the prepared pans. Cover with a damp towel or lightly greased waxed paper. Let rise in warm place, away from drafts, until doubled in volume, for 30 to 45 minutes.
9. To bake, heat oven to 400 degrees F. Bake bread for 25 minutes or until hollow sounding when lightly tapped. Turn loaves out onto wire racks and let cool completely.