Rudder trim tab

[Bdflies]

The thoughtful builder, who started the project that I finished, added two nutplate tabs to the trailing edge of the rudder. I don't believe these are mentioned in the plans, but I strongly recommend doing such. If your plane flies straight, with no yaw, great! Don't put a trim tab and accept the few grams on the tail. Mine needed a good bit of left rudder in cruise. Adding a rudder trim tab was as easy as cutting a piece of .032" aluminum and screwing it to the tabs! After a couple of adjusting bends, she's 'feet on the floor' straight!
I probably wouldn't have thought to add those tabs on the rudder, but I'm sure glad they were there!

once again, just sharing thoughts.

Bill

[Flygirl1]

Bill, Dennis and I agree. Tabs for nut plates would have been the thing to do, but that "plane flew" already. ;-( My other plane had sheet metal screws in the rudder frame and was never a problem and it's what I will do now, but in hindsight...

[Bdflies]

Yeah, I hear ya. I Covered them up and forgot about them. After a few flights, it was obvious that some rudder trim mechanism was needed. That's when I remembered those tabs! The picture helped me locate them.

This forum is such an amazing resource, for builders and fliers! I've been scratching my head, thinking of stuff that might help others. The rudder tab idea came to mind. I've got a couple more to come.


Bill

[Mark Goldberg]

On my 4 place I pop riveted a little rudder tab to the flange of a rudder rib. It has held up well over the years. On the part of the tab that is more or less the same place as the trailing edge tube - I drilled a series of vertical holes. This enables the rudder tab to be bent/adjusted more easily. Mark

[Ositodelsol]

Hi Mark, is it possible to get some Pictures
I need to install a rudder trim tab and any more detail would help in this small project
Thanks

[Zzz]

Anyone have photos of their actual rudder trim tab in place?

[rv8bldr]

Brilliant. Guess what I'm welding in tonight :-)

[Bdflies]

Zane; pics of mine attached.

Mark;

Bill

[Battson]

Mine is screwed straight into the tube, although this does let a lot of moisture into the tube and encourage corrosion.

I will be welding on tabs with nut plates in future.

[whee]

I know we've been though this before and I recognize that many airplanes have such trip tabs on their rudder and ailerons. I just want to share a different opinion. The mechanic that worked on my previous airplane was of the opinion, as was the Luscombe guru I ask for rigging guidance from, that those tabs are a last resort for when you can't resolve the issue through proper rigging. Maybe it's a mistake but I'm not adding provisions for such a tab. I was able to make rigging adjustments on my Luscombe and a previous BH so I didn't have to hold and rudder in normal cruise. I don't see why I won't be able to do the same on my BH.

[Ed.Meyer]

I recently added a tab like Battson has. When I met with Bob Barrows a few weeks ago and mentioned to him that it was yawing to the right he right away looked at tha angle of the top of the verticle stab compared to the rest of the fuselage and noted that it was angled for right turn. He said the bottom of it should have the right compensation built in but not the top. He suggested using a spring to apply a bit of left rudder which I tried but it was not enough and I did not like the idea of asymmetrical rudder pedal pressures so added the tab. It fixed it.

I know I initially had said there were no trim issues, and there was not a heavy wing, but I had not even realised I was holding left rudder at first.

[Bdflies]

Whee, I pretty much agree with you, but... How would one 'rig' to eliminate yaw? I'm not looking at the plans, right now, so I'm going on memory here. There is A LOT of left offset built into the Patrol"s vertical stabilizer. I recall 3/4" offset, left of center. I thought it looked like a bunch, when I laid eyes on the fuselage, but it was called out in the plans. My initial flights kinda confirmed my initial impression. I don't think the plane needs that much offset. This opinion is shared by other Patrol pilots that I've communicated with. The tab negates some of that vertical offset.

I thought about adding a booster spring under the left pedal. But, a spring that would center the ball, at cruise, would be too much at slower speeds and too little when faster. An adjustable booster spring mechanism could be constructed to provide variable boost, to center the ball at all speeds. That mechanism, would require the pilot's attention and add weight. The rudder tab provides more force as speed increases, thus it keeps the ball 'centered' at all speeds, when bent correctly. It works well.

Note: I'm not trying to be right, here. This is the thought process that brought me to install the tab. The nutplate tabs, in the rudder, made it very easy to install the trim tab. If anyone has another way to 'rig' something to eliminate the yaw, I'm completely open to suggestions.

Bill

[Flygirl1]

Dennis and I agree—the off-set appears to be a bit much. So who wants to be the first to change it, fly it and let us know how it works for you?? Right now I am using some pressure on the left rudder in flight and even less if flying economy cruise. Dennis has installed a trim servo and has posted photo’s in Jared’s post back in March—“thinking about a third auto pilot servo”. His only complaint is trying to remember to “undue” the servo from cruise to landing configuration. Other than that it works great. I did not install one. I would forget it at least once and that one time might be the straw that broke the camels back. Not willing to take that chance.

[Bcone1381]

100% of the rudder trim tabs on this thread are applying left rudder. Ed, Bill, Battson, Dennis and Denise.

Hmmmmmm.

[Chris In Milwaukee]

100% of the rudder trim tabs on this thread are applying left rudder. Ed, Bill, Battson, Dennis and Denise.

Hmmmmmm.

I'd say "true" that, but it looks like mainly for cruise flight. I wonder if anyone has set or flown zero-angle on the vertical stab and noticed a difference where it's probably most helpful, like high angles of attack on take off and such?

Dan Shilling up in Alaska has a left-turning engine on his plane. I wonder if he went the other direction (or zero).

[Bdflies]

Chris said;
"I'd say "true" that, but it looks like mainly for cruise flight. I wonder if anyone has set or flown zero-angle on the vertical stab and noticed a difference where it's probably most helpful, like high angles of attack on take off and such?"

I think I understand you to be asking about zero angle on the rudder trim? The vertical stab is welded in, thus not easily adjustable. At high power/ high AOA it needs right rudder, just as you'd expect. Half fuel, solo (phase 1 still...) I see 1800 fpm climb, so that phase of flight doesn't last very long. No better or worse than similar planes.

Before I go any further into this subject, I want to be really clear; None of my comments should be construed as criticism of the airplane. The more I fly it and make little adjustments, the better I like it! The Patrol performs as advertised, it's delightful in flight and it's VERY comfortable. The rudder trim tab is a miniscule little detail that just fine tunes the plane. I felt it needed something to trim the yaw. Earlier, I posted about my adjustment of the ailerons, to lighten roll forces. I added a 'cooling lip', because engine temps were uncomfortably high. I made a new flap handle, to ease deployment. Each little change tailored the plane to my preference. At this point, I'm going to say that it's more pleasant to fly than my old Husky. Yes Mark G., I said it. You were right! I'm not 100% sure it's quite as good a STOL performer, but it's so close, you can't tell the difference. It's so much more comfortable, it more than makes up the difference.

Some planes have engine offset, to counter the effects of P factor. Bob chose to offset the vertical stab and leave the engine thrust at zero offset. Is one better or worse? I have no idea. Just different approaches to the same goal. Every choice represents a compromise and we (as manufacturers) get to choose the compromise that we're most comfortable with.

Now, turn off your computer and go make a part!

Bill

[Bcone1381]

Post #12 did not reveal my heart and focus for continual improvement.
Post #13...Chris, my goal would be for the rudder to faired in cruise flight, which demands some right rudder in takeoff and climb.
Post #14, The wonderful environment and nature of Experimental Amateur Built aircraft is owners and builders who seek continual improvements. I see no negative criticism, and intended none in post #12.

Brooks Cone
Patrol Quick Build