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offset vertical fin

Posted: Wed Dec 12, 2018 4:02 pm
by CuBob
Has anyone offset the vertical fin to compensate for p factor. My cub is offset as is most aircraft.

Thanks Bob

Re: offset vertical fin

Posted: Wed Dec 12, 2018 4:59 pm
by taildrags
Bob; the VS on my Air Camper, Cont. A75 engine, is offset 1/2" from the vertical. I've seen some setups that have stacks of washers on each side of the VS to permit varying the offset by shimming.
offset.JPG

Re: offset vertical fin

Posted: Wed Dec 12, 2018 5:33 pm
by CuBob
The washer idea is great, maybe I will go with that. Are you able to fly without any rudder input during cruise?

Re: offset vertical fin

Posted: Wed Dec 12, 2018 9:57 pm
by taildrags
Bob; although I won't say that my Air Camper now flies "feet off" in level cruise, it's a lot closer than it was before I adjusted the engine thrust offset and put a bit of offset in the vertical stabilizer. I would have put in a bit more offset to the VS to get things perfect, but the aft spar of the VS is fixed in place and I didn't like the feel of twisting the leading edge over while the trailing edge remained fixed. I had hoped that my tweaks would allow me to remove the bent-metal trim tab on the trailing edge of the rudder, but that was not to be after test flights showed that it still yawed a bit without it. As it is now, I've managed to get it where it won't yaw noticeably in cruise for maybe 15-20 seconds when I take my feet off. Before I made the adjustments, the nose would start to swing the second I took my feet off the rudder bar.

You can see my metal trim tab on the rudder, here-
trim.JPG
trim.JPG (22.49 KiB) Viewed 1569 times

Re: offset vertical fin

Posted: Tue Dec 25, 2018 10:57 am
by RonTurner
I have the same issue with N2094? Cruise is hands off at 75 MPH and 2100 RPM but I have to apply slight right rudder pressure. Usually just the weight of my foot is enough to correct a left turn & bank. I added a small rudder trim tab ( 6 inch X 2 ) but didn't notice a difference ? I was hoping it was the nature of the beast and not a problem.

Re: offset vertical fin

Posted: Thu Mar 14, 2019 6:15 pm
by E.Woodson
Has anybody explored the idea of using the stacked washer idea for the front attachment point to allow lateral adjustment and... here we go... for the rear attach point instead of the two brackets on the outside of the vert stab as shown in the plans, as far back as possible, drive a single vertical bolt through the bottom main beam (base piece of vert stab) into a hefty nut plate under the longerons at the aft fuselage to create an attachment point that could pivot the rear of the vert stab and allow for offset adjustment? Add a small inspection panel on the side of the vert stab and you could move the leading edge left or right by adding or subtracting washers while pivoting around that rear through bolt attachment and tighten it down through the inspection panel. Ideas? Just spit ballin and not married to it...also not really a fan of deviating from the plans, but...

Re: offset vertical fin

Posted: Fri Mar 15, 2019 8:24 am
by EAB4
E
as Oscar said, the stacked washer method has been used on a number of planes.
My VS is offset about 5/8"- I ran a rod through all the rudder hinges and rotated the VS around the hinges, then made my fittings to fit.
that way there is no added stress on the main beam of the VS from twisting it to get the offset.

Re: offset vertical fin

Posted: Sat Mar 16, 2019 9:40 am
by E.Woodson
So that's the leading edge displaced 5/8 to the left correct? Have you ever felt that was not quite the right setting or that you wish you could adjust it (not in flight)? How is it in flight? Kinda spoilt about having a nice trimmed out aircraft.

Re: offset vertical fin

Posted: Sat Mar 16, 2019 11:28 am
by taildrags
Mine is offset 1/2" to port but the offset would be in the opposite direction if you have a Corvair or other engine that turns in a direction opposite to Continentals and Lycomings. I honestly don't know which way a Ford (or a Jeep) turns. I have no need or desire for in-flight adjustment of rudder trim but I could use a little more vertical stabilizer offset for my plane to fly straight in level cruise without a touch of foot on the rudder.

My, but we've gotten lazy and spoiled compared to the old days when flying machines required constant attention!

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power

Re: offset vertical fin

Posted: Sat Mar 16, 2019 11:28 am
by taildrags
Mine is offset 1/2" to port but the offset would be in the opposite direction if you have a Corvair or other engine that turns in a direction opposite to Continentals and Lycomings. I honestly don't know which way a Ford (or a Jeep) turns. I have no need or desire for in-flight adjustment of rudder trim but I could use a little more vertical stabilizer offset for my plane to fly straight in level cruise without a touch of foot on the rudder.

My, but we've gotten lazy and spoiled compared to the old days when flying machines required constant attention!

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power

Re: offset vertical fin

Posted: Sat Mar 16, 2019 5:50 pm
by EAB4
Mine is offset to the right (Corvair engine)
It's not flying yet, but that distance was recommended to me by people who have many hours flying Corvair powered Pietenpols
If I find it's not right on my plane, I'll either add a trim tab or adjust the fittings.