I shall offer a quick digression on the ring-equivalent sim method I am using.
- calculate the circumference of the ring
- create a fin set with the following characteristics:
- rectangular shape
- root edge same as ring width
- position same as ring
- Total area of fin set equal to area of ring
Originally, this was done while also making the height of the fins equal to the distance from the inner BT to the ring, so that it looks the same in side view. In this case, for the front ring, that would have required more than 8 fins in the set (disallowed by OR) so I made the fins taller and used... I think 7 of them, or thereabouts. A 3" ring generates quite a bit of "fin area" when wrapped around a BT60.
If anyone wants to weigh in on whether this has any likely connection to reality, I'm all ears. To me it passes the basic sanity test because the fin set is roughly equivalent to chopping up the ring into small pieces and attaching them to the body. In cases where the diameter of the ring is closer to the diameter of the inner BT (how close exactly? dunno), and the airflow might not be as free, this whole thing almost certainly doesn't work. Given how short the rings are, and the substantial distance between them and the inner BT, I thought it would work in this case.