Better get started unless you want a later dinner...7-bone whole ribs I've smoked in the Smoke Vault 24 @ ~225* take about 8-10 hours to hit 145* (18-22lb range). If you have a partial rib (4-5 bone), and it's the large end, then it's a lower cross-sectional density compared to a whole rib, and won't take quite as long as the small end with a higher cross-sectional density (small end has shorter rib bones with a sharper curve, but is the bulkier, thicker end).
130* I/T with 250* chamber temp, figure about 1/2-hr/lb for the average thickness of the whole rib, but if yours is a smaller 7-bone, it could take a bit less. What makes for difficult time estimates is that the whole rib gets longer as well as thicker with increased weight of the cut, so cross-sectional density is what you really need to consider when estimating cooking time, as longer roasts don't take more time to cook...thicker roasts take longer.
Good luck, and great smokes to ya!
Eric
