Do not get discouraged, I think i wasted 10-15kg when i first started with the bullet! Even if i was roasting for 5 years on another drum before.
My advice is to get more energy at the beginning of your roast (in the curves you showed, your roast is too slow; also for me it is always better when i start the fan with f3 whatever the roast). Your RoR is nice but that is kind a necessary condition not a sufficent one. Meanng that a constantdeclining RoR will not guarantee a nice cup. As Rao is stating in his last book, do not focus too much on the 20-25% DT (at last when you begin to roast with a bullet).
I guess my first advice would be to practice with cheap(er) beans. Your first goal is to identify at which temperature the beans will crack. The IBTS is perfect for that because it is more constant than the probe (for me anyway). I also clean or make sure the IBTS is clean before each roast session. The front plate is so easy to remove with the tools provided. It takes 5 min and it guarantees a more constant reading (remive the heavy handle before unscrewing the plate).
I also noticed that 400g and above are easier to manage (and replicate). I try to roast with same ambient temp and humidity too. I have an apparel that measure the grain moisture also before roasting but that is usefull to know only when you are more advanced (and try to achieve a pefect cup as i guess we all trying to do eventually). My first big succes was when i dared to roast 800g. (by the way whatever the size of the roast, same beans should crack at the same temp).
Once you have learned how the beans behave, it is easier after that to adjust your roast. With the IBTS you can simulate a gas dip as described in RAO if you want. I have done that and it works well, but not necessary on every kind of beans.
Work on one thing at a time meaning do not try to fix everything at once. I got many roasts with perfect declining RoR that was not as good as some without the perfect RoR ( but avoid imperatively big RoR crashes and flicks). Moreover these non perfect RoR were good to drink right out of the roaster without any degassing (but of course improved after 4-5 days). The smell of the roast right after cooling is a very good indicator of your success. When you will smell it, you will understand what i mean afterthat.
Finally and i find this very important, Follow a warm-up procedure (and between batches protocol) as suggested in RAO’s book. Use IBTS. Pre-heat at a higher temp than your charge temp for at least 40 min (for you first roast). So if you plan to charge at 220c, preheat at 240c for 40min, then turn it back to 220 (should take 4-8 min). then charge. Note the bean temp probe (not IBTS, for next time you want to charge around the same Probe temp; if probe temp is too low compare to last time, open the charge hole for 20-30 sec until the probe temp is similar to last time and charge).
Good luck! I am sure if you persevere, you will succeeded eventually.
ps you can be inspired by other’s recipe but you should not just try to copy a recipe unless you have the exact same beans with same moisture and similar environmental factors. You mightt get lucky just copying recipe but you will likely miss and learn nothing about the beans you are trying to roast.
