Elevator & Rudder gap seals

[seastar]

Bob
That "Vibration" below 75 mph sounds strange----?
I fly base and final at 60 mph and slow to 35/40 over the fence.
I have never felt any vibration.

Bill

[Pete D]

RE the stick vibration, you might want to check elevator cable tension and tail brace wire tension to make sure they are up to the proper tension. Sometimes just a small adjustment in cable tension can change things like that pretty noticeably, and the cables can sometimes stretch a little over time.

Pete D.

[Pilawt]

Bob
That "Vibration" below 75 mph sounds strange----?
I fly base and final at 60 mph and slow to 35/40 over the fence.
I have never felt any vibration.

I can feel a slight, low-amplitude oscillation in the pitch axis of the stick when in a full-flap sideslip in my Sport Cub -- similar to the "pitch pumping" of a C-172 in a full-flap slip. It's probably the same aerodynamic phenomenon. Cessna aerodynamicist and test pilot Bill Thompson described it as "resulting from flap outboard-end vortex impingement on the horizontal tail at some combinations of side-slip angle, power, and airspeed."

(Note: This is not the elusive and sudden "pitch down" in earlier models that prompted Cessna to put warnings in the POH to avoid slips with flaps).

[turbopilot]

RE the stick vibration, you might want to check elevator cable tension and tail brace wire tension to make sure they are up to the proper tension. Sometimes just a small adjustment in cable tension can change things like that pretty noticeably, and the cables can sometimes stretch a little over time.

Pete D.

Thanks Pete for the tip. Been that way since new. Thought it was part of the package. I did loosen and retighten the tail wire brace to do the horizontal stab replacement/repair SB just before installing the gap seals.

[turbopilot]

RE the stick vibration, you might want to check elevator cable tension and tail brace wire tension to make sure they are up to the proper tension. Sometimes just a small adjustment in cable tension can change things like that pretty noticeably, and the cables can sometimes stretch a little over time.

Pete D.

Pete, an update. I did check the elevator cable tension and tail brace wire tension. Both on spec. Before the gap seals I would get a "thumping" in the stick below 70 mph with full flaps. It would not happen at other flap settings.

After the gap seals it is gone. Can't argue with success, even if you don't understand it.

[Pete D]

Sounds good to me. What I would be curious about is if you can adjust the cable tension, still saying in spec (usually there is a 2-5 lb window) and change the "thumping" feel.

Pete D

[Dan L]

I thought I'd revive this thread with a new picture. My original comments about the effectiveness of these seals was based on wheel landings with 31" tires. When I'm on skis I three point land and I don't notice them quite so much then. But maybe I'm just getting used to them to the point I don't remember what it was like without them? My opinion is that they are very much worth installing for low speed authority.

[chipallen]

I have gap seals on my Carbon Cub demo airplane - installed at Oshkosh last July. Not sure I remember what it was like without them, but the airplane flies beautifully in pitch - so agreed; can't argue with success!

[Rich]

okay, I am conviced and will order them for SN123. How easy (hard?) are they to install?

[Pete D]

okay, I am conviced and will order them for SN123. How easy (hard?) are they to install?

They are very easy to install. Usually just push them in by hand and make sure they are all the way through by pulling the lips of the seal out on the back side. If you use something to push them in besides your hand make sure it is pretty blunt as they are easy to puncture.

Most of the time I just use my hands but I have used a plastic putty knife with the corners and sharp edges sanded off.