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Rudder Trim

T

ten4teg

Well Known Member
I am in the test phase on my RV8. I notice that with speeds above 70 knots I have to hold right rudder to keep the ball centered. I flew my friends RV8 and his does not do this.

Has anybody else had this issue and if so, how did you rectify it. Look forward to your suggestions.

Thanks, Tom
 
Check your wheel pant/leg fairing alignment

It is amazing what a difference a small misalignment will make in keeping the ball centered.
 
Last edited:
Tom,
While trim tabs can be made to fix any ball out situation, it should be the path of last resort. Everything that is hitting wind is suseptable to putting the trim out. Most notably are the wheel and gear fairings.
Please check these first or you will be throwing good money after bad. There are many many discussions on this. Please search these archives on procedures for aligning the fairings. Very small movements in the fairings can produce great results. Your airspeed and your fuel budget will thank you later for taking the time to get em perfect.
Best
 
Suppose the ball was out with the fairings off. Do you think you could use the fairings AS a trim tab? Or do you think, because of their location, that you would generate too much drag?
 
The failings WILL BE A TRIM TAB.:eek:
Never put a rudder trim tab on till you have the fairings on and have gotten em as close as you can. Then and only then consider a trim tab. You may also consider thrust shim on engine mount, VS alignment change, and others. Most folks just throw a trim tab on and call it done.
 
I am currently doing my test flights without the gear and wheel fairings, so maybe that is my problem. I will wait until they are on before I do anything. Thanks for the feedback.

I did a search on aligning the wheel pants and leg fairings, but did not find anything for an RV8. Most of the ones I saw is where the gear attached to the motor mount. Is there a good method for the RV8?

Tom
 
Never put a rudder trim tab on till you have the fairings on and have gotten em as close as you can. Then and only then consider a trim tab. You may also consider thrust shim on engine mount, VS alignment change, and others. Most folks just throw a trim tab on and call it done.
Click to expand...

My point was, would you manipulate the fairings instead of putting on a trim tab? My layman's thought was, if you really needed trim, putting something on the rudder would cause less drag, but look ugly, while manipulating the fairings migh cause more drag, but look better. Is this desirable from an aerodynamic perspective?
 
Here's my dilemma: I just placed one of Craig Catto's fine props (BIG gain, BTW- more on that later) and I find that while cruising Ithe ball is about 1/4 out requiring right rudder input to correct it.
The only change to the acft (RV-4) was going from 2-blade Sensenich to Catto's very neat 3-blade (more on that later).

So- I am going up again this morning to fly to Lake Placid to see the fall colors and before flying I am going over ALL fairings to check their alignments/conditions, etc.
PS: I have also ordered one of Avery's tabs just in case...

Jim
 
After putting on my wheel fairings and making a minor adjustment for a heavy right wing, my ball is now centered. Great machine!! Tom
 
Skyhook said:
Here's my dilemma: I just placed one of Craig Catto's fine props (BIG gain, BTW- more on that later) and I find that while cruising Ithe ball is about 1/4 out requiring right rudder input to correct it.
The only change to the acft (RV-4) was going from 2-blade Sensenich to Catto's very neat 3-blade (more on that later).

So- I am going up again this morning to fly to Lake Placid to see the fall colors and before flying I am going over ALL fairings to check their alignments/conditions, etc.
PS: I have also ordered one of Avery's tabs just in case...

Jim
Click to expand...

The Avery tab did the job perfectly-- ball is centered in cruise, now.
I still have a heavy R-H wing, though.
 
Skyhook said:
The Avery tab did the job perfectly-- ball is centered in cruise, now.
I still have a heavy R-H wing, though.
Click to expand...

I don't know if you've seen any of my 6A flight reports...

The right wing was heavy enough, that the external servo controlled trim tab on the end of the right aileron, wasn't quite enough to keep level. Yet the stick forces were very light. I also noticed that the ailerons were in near perfect trail when the stick was held to keep the plane level. And the right would move up/left down (of course), when not holding the stick or using trim.

Before doing anything, I installed the wheel pants after the engine got some breakin hours on it. The wing was still just as heavy. At first, I figured I'd tape a small wedge on the bottom of the left aileron, just as I had done on my rudder. The old six rudders had no offset.

When taping the wedge, I noticed that the radius of the left aileron was slightly thicker than the right, by about 1/16 of an inch. One of the methods of correcting a heavy wing, is to slightly flatten the trailing edge of the opposite aileron. I'm not sure about "8" ailerons, but unlike the "9", mine has bent trailing edges.

I spent about a minute with some sheet metal hand seamers covered with duct tape, and slightly squeezed about half the length of the aileron. This trial squeeze worked perfectly, and the plane flies level with the aileron tab centered.

L.Adamson
 
L.Adamson said:
I don't know if you've seen any of my 6A flight reports...

The right wing was heavy enough, that the external servo controlled trim tab on the end of the right aileron, wasn't quite enough to keep level. Yet the stick forces were very light. I also noticed that the ailerons were in near perfect trail when the stick was held to keep the plane level. And the right would move up/left down (of course), when not holding the stick or using trim.

Before doing anything, I installed the wheel pants after the engine got some breakin hours on it. The wing was still just as heavy. At first, I figured I'd tape a small wedge on the bottom of the left aileron, just as I had done on my rudder. The old six rudders had no offset.

When taping the wedge, I noticed that the radius of the left aileron was slightly thicker than the right, by about 1/16 of an inch. One of the methods of correcting a heavy wing, is to slightly flatten the trailing edge of the opposite aileron. I'm not sure about "8" ailerons, but unlike the "9", mine has bent trailing edges.

I spent about a minute with some sheet metal hand seamers covered with duct tape, and slightly squeezed about half the length of the aileron. This trial squeeze worked perfectly, and the plane flies level with the aileron tab centered.

L.Adamson
Click to expand...

I am going into the hangar today to mic the radii of those aileron bends.
Thanks.

(Recall, though, with the SenSen 2-blade, all was centered & hands-off.)
 
Rudder Trim & rudder pedal extensions

I have the rudder trim & rudder extensions from www.mlskunkworks.com and they are really fine products, very well engineered and machined. I still can't believe the guy can make and sell these for the price he asks. I am going to buy a second set of the rudder pedal extensions before he figures it out and suggest anybody wanting a set do the same. Very nice products.
 
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