Stabilizer Streamline Strut Vibrations

[Steve W]

Nev, I think you are referring to the 4 place. The Patrol strut is formed and drilled at each end so no threads.

Mark, Mike Silvernagle mentioned making 6 strips so that's what I used pr side. He may have only added three a side. Unclear on that whether he attached the six to the one strut that was vibrating or three to each.

Mike wrote:
" I ended up cutting 6 pieces of 1/4" wide strips of velcro 1" long and sticking them to the underside of the 4130 streamlined tubing"

If the weather was warmer and I had the opportunity to play with the strips, I'd see what the minimum would be to eliminate the vibration.

Thanks for the feed back guys.

[Mark Goldberg]

While I have no knowledge about this and no expertise - I kind of suspect just one strip in the middle might break up the harmonic vibration. But someone would need to try. Mark

[svyolo]

This thread might be important enough safety-wise to put somewhere that all builders see it at some point. Maybe a Beartracks article? Sticky in one of the forum categories, like the current one?

[jaredyates]

I would love for someone to put together a Beartracks article about it.

[Wyo Johnson]

Correct me if I'm wrong, but I remember some time ago Jared caught an issue during an inspection/preflight on this tail strut? I did a search but didn't find the thread, just wondering out loud if this is related?

Higher time and/or bush fliers seeing any issues?

Andy

[jaredyates]

I think mine broke because of corrosion rather than resonance

[Battson]

Mine also broke in flight, there is a different post about that plus and engineering change which fixed the issue.

The beauty of the design is the tail system has redundancy, so wires or struts failing is not a problem.

[Craig Van Sickle]

Nev, I think you are referring to the 4 place. The Patrol strut is formed and drilled at each end so no threads.

Mark, Mike Silvernagle mentioned making 6 strips so that's what I used pr side. He may have only added three a side. Unclear on that whether he attached the six to the one strut that was vibrating or three to each.

Mike wrote:
" I ended up cutting 6 pieces of 1/4" wide strips of velcro 1" long and sticking them to the underside of the 4130 streamlined tubing"

If the weather was warmer and I had the opportunity to play with the strips, I'd see what the minimum would be to eliminate the vibration.

Thanks for the feed back guys.

Thanks for sharing your experience here Steve. I'm setting up to attach my horizontal stab, choosing wires, and fabricating the struts. Another thing that might be impacting resonance in addition to strut angle of incidence is if it is in tension, neutral, or compression while rigging that specific aircraft. I just finished a CNC table build and this plays a big role in lead screw whip. Fixed or floating ends also impacts resonance. A clevis through a thin plate doesn't impart much rigidity to the strut. Some strut end attachment methods "fix" it and completely change how it would resonate and it's compression strength. Wittman Tailwind wing struts are built this way on the fuselage side. They also insert a core into the streamline tube to give it more compression strength. I can see where a tail strut with two floating ends would be inherently prone to vibration. I believe Maule has the bottom attach point fixed, probably for this reason.

Another option that be would locally available and hold up well is 3M safety-walk tape. If I remember correctly Rans installed some mid wing strut to solve a resonance issue that came up in testing with the Lycoming/S-21. https://www.amazon.com/3M-Safety-Wal...1&sr=1-12&th=1

[Battson]

I have also had issues with the streamlined flying wires hitting resonance, they vibrate a lot and you will never know unless you look back when the elevator is unloaded (hands free). You can change the resonant frequency by changing the tension in the wires (I suggest lower, not higher).

[Craig Van Sickle]

I've searched and can't find the thread that covers your strut break and engineering change. Do you have a link?

[Craig Van Sickle]

I have also had issues with the streamlined flying wires hitting resonance, they vibrate a lot and you will never know unless you look back when the elevator is unloaded (hands free). You can change the resonant frequency by changing the tension in the wires (I suggest lower, not higher).

Good to know. When I do get to flight testing it will be interesting to mount a rear facing gopro and record how everything behaves through the full range of speeds, CG, etc. I'd like to flush any issues out during the 40hr testing phase.

[Craig Van Sickle]

I wonder if big tires throw more turbulence back to the tail?

[Battson]

We first encountered the issues with smaller tires fitted, Goodyear "26s" (which are really 23 inches tall)