Dr.Ben
Elite Veteran
Location: Richmond, VA, USA
| A lovely balancing act........................
We use horizontal fin size and placement to trim the model in FFF at 3/4 or a bit higher pitch/throttle such that the model flies in dead level trim with zero swash trim and no need for any pmixes. To some extent you can juggle the size of the fin versus how far back on the boom you position it, but if the fin size starts to get large, the downwash of the rotor will induce aft cyclic trim in the model in hover. A small horizontal fin mounted out in the vertical fin offers the potential advantages of good trim leverage by being so far back on the boom (and thus able to be small in size) while staying out of direct downwash of the main rotor.
Necessary fin size varies markedly with rotor design and blade type. The 0840 MA head needed a large fin out out back to correct the diving tendency in FFF. The 0848 head and various versions of it require little fin area out back. In fact, my models use 3D horizontal fins to achieve neutral FFF trim with the stock Fury Expert head w/ neg delta. We'll see what the Tempest head needs.
Ben Minor |
