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  #1  
Old 09-10-2018, 08:42 PM
Rallylancer122 Rallylancer122 is offline
 
Join Date: Aug 2013
Location: Oconto, WI
Posts: 85
Default Vertical Stab Offset

Hi All,

I just finished a significant rebuild of my Dad's RV-8 that included reskinning the rudder and remounting the vertical stab (new attach plate and holes). I mounted the fin centered per Vans instructions. When I test flew it last night, it needed a significant amount of right rudder in cruise. Is this normal?

I don't recall it being this out of trim when I flew it before the repairs. Unfortunately I didn't think to measure what it had when I took it apart. I recall Dad at various times installing trim wedges on the rudder, but there wasn't one when I took it apart.

The easy thing would be to just put on a trim tab, but I just reskinned the rudder and the thought of drilling new holes into it depresses me. Besides, I just don't like them (ugly). Has anybody tried offsetting the vertical stab? A forum search shows some of the -6 and -4 guys did it, but not sure if anyone has tried it on an -8.

Thanks!
DEM
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  #2  
Old 09-11-2018, 05:48 AM
ILikePike ILikePike is offline
 
Join Date: Jan 2011
Location: Eatonton, GA
Posts: 204
Default

Check landing gear and wheel fairing alignment before making any rudder changes.
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Jeff Green
2016 RV-8 #82985
1968 E33C Aerobatic Bonanza
Pleased to donate Dec 2017
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  #3  
Old 09-11-2018, 08:58 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 7,710
Default

Pretty much all RV's have some amount of right rudder trim added.
If they don't, it is not because the build did such a fine job, it is because there are other trimming influences built into the airplane that are causing a right yawing tendency that adds what is needed.

Offsetting the vertical stab can get the same result as a rudder trim tab or wedge (I offset the vertical stab. on my personal RV-6A so it has no rudder trim tab). Keep in mind that to get enough trimming influence, you need to move the stab enough that you will have to totally redo (I.E., make a custom one) the aft empenage fairing. Not really worth the effort.
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Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #4  
Old 09-11-2018, 03:00 PM
spatsch spatsch is offline
 
Join Date: Nov 2014
Location: Randolph, NJ
Posts: 183
Default

To answer your question. Yes that's normal.

Personally I prefer to use a bungee cord to pull the right passenger rudder pedal forward in cruise over a wedge. The problem with adjusting the fin or adding a wedge is that it will only work perfectly for one speed/power setting. For everything else you will still need right or left rudder to stay coordinated. My bungee cord is fully adjustable, safe (can overpower it easily with my feet) and I can/do remove it entirely when not on long distance cruise. I did see somebody building a rudder trim for an 8 but was a bit worried that if it broke during acro the thing would entangle my feet. Not a good thing ... .

Oliver
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Oliver Spatscheck
RV-8 & J-3
N-2EQ & NC-49762
http://www.spatscheck.com/oliver
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  #5  
Old 09-11-2018, 04:23 PM
Ron77 Ron77 is offline
 
Join Date: Jul 2017
Location: Kemah, Texas
Posts: 43
Default RV8 Rudder Trim

Scroll to the bottom of the page to see the RV8 trim hardware http://www.mlblueskunk.com/Rudder_Trim_System.php

Ron B.
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  #6  
Old 09-11-2018, 05:35 PM
Berchmans Berchmans is offline
 
Join Date: Nov 2009
Location: Anchorage, Alaska
Posts: 414
Default What is Normal

Actually I built my RV8 per the plans, mounted everything including wheel pants before fist flight, everything was mounted dead nuts straight. I can fly with my feet flat on the floor with no rudder trim required what so ever, even doing a Hoover roll, no rudder needed. Check everything being straight first. I once had a water rudder out of alignment on my float plane with played **** with rudder inputs.
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Burke Wick
Flying RV 8
Anchorage, Alaska
VAF Dues Paid for 2018
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  #7  
Old 09-11-2018, 07:31 PM
Rallylancer122 Rallylancer122 is offline
 
Join Date: Aug 2013
Location: Oconto, WI
Posts: 85
Default

Thanks Everyone! The gear is out of whack for sure as I just kind of threw that stuff on for testing. I'll tweak and tune that first.

I like the internal spring trim systems. We don't have the rear pedals installed so I'll have to invent something on my own, but shouldn't be too hard.

DEM
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