Rudder trim

[Maverick]

I liked your piece of wood you used as the rudder trim tab. Your latest pic shows it. Are you as happy with it in execution as you thought you would be in theory? About how along a piece did you wind up putting there? I want to know cause I want to use that idea. It's perfect.
Geek

I'd like to know more about this too.
Fred

[jrevens]

OK John. Another subject. Way back when I was looking at things I wanted to be sure I did with my build, I liked your piece of wood you used as the rudder trim tab. Your latest pic shows it.


Are you as happy with it in execution as you thought you would be in theory? About how along a piece did you wind up putting there? I want to know cause I want to use that idea. It's perfect.

Geek

It works great... I lucked out and it's just about perfect for my airplane. As I recall it's about 5" long. I'll try to remember to measure it when I'm at the hangar tomorrow. It's mounted with screws and nut-plates, so it can be easily removed and adjusted in size if necessary. My buddy Stan has one like it on his Mod. IV, and I decided to use the idea based on his experience.

[PapuaPilot]

I copied the idea of the wood wedge too, but I didn't have anything to screw it to inside my rudder. I cut a wedge of wood and did some test flights to adjust the length. I attached it temporarily with 2" masking tape. Once I found the right length I matched the paint with a sample of Latex house paint and glued it on the rudder. Works great!

[PapuaPilot]

Maverick,
I couldn't find a way to put a photo in a PM. My tab is about 10" tall, 1" wide and about 1/4" wide at the trailing edge. After painting it I glued it on with clear silicon glue.

Trim tab.jpg

[Geek]

So this would be to both John and Phil....... Look's like John's approach is about 5 inches long (looking at the space between the ribs on the vertical) and is pretty much in line with the horizontal stab/elevator. Phil's is twice that long but is located above the horizontal stab assembly. Think there is a difference in effectiveness dictated by the location? I think John used Rivnuts to install his that he put in before covering which is how I think I will be doing it. Now I just have to figure out where. Thanks again for the replies and inputs. A huge help.

Geek

[jiott]

I used a bent piece of thin aluminum and mounted it with nothing more than 3M double stick automotive trim tape right to the fabric. Been on now for almost 8 years with no sign of loosening. I am sure it would do just as well on your wood wedges.

[Dave S]

I used the same idea that Jim did - 3M double stick trim tape. I did not build a backing plate into the rudder before covering so this seemed the best way to go. The other thing is I stole an idea from the Citabria folks - i.e. stuck it on the right side of the rudder with the convex curve going to the left behind the tube. Aerodynamics 101 says something like it's all about lift on the convex side. After flying it, the curvature was reduced to less than what you see in the photo so the tab barely sticks out past the left side of the tube. The tab is 6" high and has been stuck there for years with no signs of delaminating.

Highwing who has been a big contributor to this list, made a device within the rudder which changed the shape of the right side of the fabric a very small amount (more or less of a crown) to accomplish rudder trim by creating lift on the right side of the rudder.

Another pal of mine who has an antique aircraft found a similar device inside the rudder of that aircraft when recovering - there was a very small hole to stick a screwdriver through for adjusting the crown of the right side of the rudder.

[Maverick]

So, John and/or Phil, once the length, width, and thickness of the wooden piece is worked out, what do you think of using polytak to glue it to the rudder?
Fred

[jrevens]

We should put these posts in a "rudder trim" or similar category... can one of you moderators do that?

Maverick - I think you should probably attach it temporarily with tape to test before final installation, then glue or double-sided mounting tape is good. I'm not sure about Polytak specifically.

[jiott]

I really recommend the double stick trim tape because if ever desired, it can fairly easily be removed by pulling a thin wire thru the foam portion of the tape and then peeling the residue off the painted fabric. To remove a glued-on piece would most likely take the paint off with it.