In another thread on Flutter Flutter there were posts 31 and 33 talking about adding a device to trim tabs to prevent flutter. Part 23 was even mentioned as requiring such, but no one cited chapter and verse. Yeah, Part 23 does not apply to us, but it is still usually a good idea. I have done a couple searches, but found nothing. I have also gone out looking for various dampers, and thinking about how to incorporate such a device in my bird. So:
Billski
- If you know where we can find this "requirement", please cite chapter and sub-chapter of Part 23.
- Besides the anecdote of a tab fluttering on a Rocket, do we have any other background on how often we actually see trim tab flutter due to the linkage coming apart? I prefer to distinguish flutter from other trim tab error states, which are also interesting;
- Anybody have any guidance on what level of friction is needed? How much friction on the Lancair derivative Cessna's is spec'd, and what is the control horn radius? Critically damped is needed to fully prevent flutter, but I would suspect that less than critical damping would keep the oscillation down enough to allow slowing the bird then getting to an airport and down. Guidance necessary here...
- Separate tab control horn and linkage running to a damper buried in the elevator;
- Dampers using silicone fluid of many types are available commercially. Hansbach has many devices that appear to easily fit inside an elevator :
- Many linear ones, usually intended to stop a moving mass. Many levels of resistance available. No threaded ends or clevis or other attachment methods are provided on most;
- Rotary ones weighing as little as 8 grams which have either gears or shaft, but they get to 2500 g-cm (about 2.2 in-lb) which might be enough for a half pound tab. 1" diameter and 1/2" thick, $10. Many levels of resistance available. If we need more than 2.2 in-lb, they have bigger, but might have to be mounted in the stabilizer. They also come in a smaller diameter, longer cylindrical form. They have mounting tabs and would require an arm clamped to the shaft. The rest of the system would probably be pushrods and clevis fittings from RC suppliers.
Billski
