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Rudder Asymmetry

Rocky005

Member
We have finished our RV-14 rudder as per VAN's plans. Our trailing edge is bonded with 3M adhesive tape, riveted and it is nice and straight.
One side of the rudder now sits flat on the workbench but if we turn our rudder over it has a twist of about 20mm causing it to rock.

Please post how your RV-14 rudder sits with each side up (ie flat) when on a level workbench? Does anyone else see a twist on one side of their rudder?
DSC_0064.jpg


This may not affect our rudders performance. Thoughts?
 
Twist

I don't see how one side could be twisted and not the other side. Sounds to me like your bench is twisted also.
 
Its supposed to be! I believe the rudder spar is wider at the base then at the top, it tapers.

Yes you are right the rudder spar or front trailing edge is tapered. But shouldn't both sides rock by 10mm (ie symmetrical), rather then like ours were one side is flat and one side has a 20mm rock.

Its not the bench sorry.
Would love a response from someone with the rudder riveted, thanks.
 
You are correct.
Neither side of the rudder should be able to lay flat, on a flat surface.
It sounds like your rudder has a twist in it.
Did you have it weighted down flat on one side when you riveted the trailing edge?
 
Me too!!!

Interesting. I used a granite counter top (very flat) and lots of weight when bonding the trailing edge of my RV7 rudder and ended up with the same result. It is very straight on the trailing edge, lays down flush with the counter top on one side. Flip it over, and it hovers above the counter top. Seems it go flattened past the center point of the rudder during bonding.???

Is this useable or do it again?

Thanks,
 
Old School Alignment Tool

This might be something where a lesson from the past would be helpful. Here's the rudder assembly jig for my RV-3B, built per the plans and the manual.

The two Vee cuts were carefully aligned. Notice that I've got the base clamped down. It was shimmed so the centerline of the two Vee cuts were parallel and clamped securely. If you look closely, you can see a shim at the lower right corner of the photo.

Besides the leading edge, the skin to spar joint was drilled and riveted in this jig.

b4iwd5.jpg


Dave
 
Rudder

It has been awhile since I've had my -8 rudder on the table. It currently hangs high on the wall. Are the sides of these rudders not flat? Just because the surface tapers both top to bottom and front to back does not mean the surface isn't flat. If the surface is flat it seems like it should flat of the table.

Maybe I'm not remembering this correctly.
 
It has been awhile since I've had my -8 rudder on the table. It currently hangs high on the wall. Are the sides of these rudders not flat? Just because the surface tapers both top to bottom and front to back does not mean the surface isn't flat. If the surface is flat it seems like it should flat of the table.

Maybe I'm not remembering this correctly.

My sentiments exactly. I built my RV10 rudder on a flat bench, with the trailing edge clecoed into a steel angle to maintain straightness while the proseal cured. Then I double flush riveted per Vans instructions. Both sides of my rudder lie flat on my table.
 
I guess it warrants repeating regularly....

Even though all RV's have roots back to the RV-3, that doesn't mean the are all the same in all respects....

The thickness / cord ratios on the RV-10 and RV-9 rudder (and RV-7 as long as it was built with the riveted T.E. rudder), have flat sides and can be riveted with them weighted down flat to a work table.
All of the other tapered profile control surfaces (elevators included) are not entirely flat on the skin surfaces and can not be weighted flat while riveting.
That is why the "V" blocks previously mentioned have been supplied in the RV-6, 7 and 8 emp kits.
The rudder on the RV-14 also falls into this category, though V blocks are not used because the trailing edge needs to be back riveted on a back rivet plate.

The build instructions for the RV-14 rudder do not say to weight it down flat, but it looks like some additional information will need to be added. I will look into it.
 
I guess it warrants repeating regularly....

Even though all RV's have roots back to the RV-3, that doesn't mean the are all the same in all respects....

The thickness / cord ratios on the RV-10 and RV-9 rudder (and RV-7 as long as it was built with the riveted T.E. rudder), have flat sides and can be riveted with them weighted down flat to a work table.
All of the other tapered profile control surfaces (elevators included) are not entirely flat on the skin surfaces and can not be weighted flat while riveting.
That is why the "V" blocks previously mentioned have been supplied in the RV-6, 7 and 8 emp kits.
The rudder on the RV-14 also falls into this category, though V blocks are not used because the trailing edge needs to be back riveted on a back rivet plate.

The build instructions for the RV-14 rudder do not say to weight it down flat, but it looks like some additional information will need to be added. I will look into it.

Sorry, I thought the 10 rudder was similar to the 14. While I saw the 14 in person at OSH, I was so busy oohing and ahhing that I couldn't honestly tell you how that particular rudder goes together. Didn't mean to steer anybody wrong.
 
Sorry, I thought the 10 rudder was similar to the 14. While I saw the 14 in person at OSH, I was so busy oohing and ahhing that I couldn't honestly tell you how that particular rudder goes together. Didn't mean to steer anybody wrong.

Same here.

That was a nice narrative by Scott. He should really consider designing airplanes for a living :rolleyes:
 
I am building this RV-14 with Rocky005 who started this thread.
Scott thanks so much for commenting here:D, I am looking forward to following this thread to see how it pans out.

I guess it warrants repeating regularly....
Even though all RV's have roots back to the RV-3, that doesn't mean the are all the same in all respects....
Agreed, they are not the same in all respects.

The thickness / cord ratios on the RV-10 and RV-9 rudder (and RV-7 as long as it was built with the riveted T.E. rudder), have flat sides and can be riveted with them weighted down flat to a work table.
I don't understand how any of the afore mentioned models rudders can have flat sides and be weighted down as the rudders are not constant cord and instead the rudders are tapered at the leading edge but not tapered at the trailing edge (if that makes sense).

All of the other tapered profile control surfaces (elevators included) are not entirely flat on the skin surfaces and can not be weighted flat while riveting.
That is why the "V" blocks previously mentioned have been supplied in the RV-6, 7 and 8 emp kits.
Sorry not sure what you mean here? The elevators are constant cord so they are flat (ie no twist). We are not planning on weighting them down flat but I believe we can assemble the elevators and ailerons on a flat surface?

The rudder on the RV-14 also falls into this category, though V blocks are not used because the trailing edge needs to be back riveted on a back rivet plate.
My point is that I believe a change may be required to the build process as a jig is needed. One RV-7 builder has posted in this thread and has indicated that he also has a asymmetric rudder issue. It may simply be a cosmetic issue, we are waiting for VANS's to reply to a support email before we consider ordering a new rudder
The build instructions for the RV-14 rudder do not say to weight it down flat, but it looks like some additional information will need to be added. I will look into it.
The trailing edge was not deliberately weighted down but we did attach a light weight aluminum right angled piece to ensure we obtained a straight trailing edge. This worked and our trailing edge is very straight.
In hind sight we needed to jig this right angled piece and lift one end by 10mm. That way the rudder would rock by 10mm on both sides (and be symmetrical).

VANs may want to consider moving to a constant cord on the Vertical Stabilizer and rudder on future models, it may not look as nice but it would be much easier to build.

Rocky005 will post some additional pictures to help clearly show our problem.
I was hoping other builders would check theirs rudders on a bench and post here as its not an obvious flaw and they may not have noticed.
Again your thoughts are appreciated.
 
Last edited:
It is possible for a rudder to have a flat side because it tappers in cord and in thickness. If the ratio of change of each is correct, it would allow the skin to be flat.
Try it with a couple pieces of cardboard cut to mimic miniature rudder skins... join them at the trailing edge and you will see that a spar of the proper taper ratios would make the skins each flat.


Constant cord elevators... I was talking about the other models... the RV-4,6, 7 and 8 all have tapered elevators. Only the 9,10 and 14 have constant cord ones.

BTW, I believe the construction manual does prescribe weighting down all the rest of the control surfaces to help assure they are built flat.

Proper alignment of the RV-14 rudder is almost automatic (as long as it isn't weighted down on a flat surface during riveting). All of the prototypes built so far were done so with no special effort for alignment other than to make sure teh T.E. remains straight.

It is possible to shim it a specific amount in a specific location to assure it is straight. That is what I will look into.

I don't think a change to constant cord is necessary. Almost 3000 RV-9's, RV-7's, and RV-10's (combined) have been successfully built with this style of rudder.

If the final decision is that the rudder is not acceptable, you could correct the one you have by just un-riveting the trailing edge and re-riveting with it correctly aligned. It requires just a very small amount of movement between the two skins to allow the amount of torsional twist you are measuring. This is well within the fit tolerance of the dimpled (thus slightly enlarged) holes. I am certain that re-riveting the T.E. would allow it to be properly aligned.
 
I lost some sleep over this last night :) . My rudder would rock a little while laying flat on one side but not the other. I couldn't wait to get to the shop to check it out.

I stood the rudder up on the bench, balancing on rudder horn, and put my digital level against trailing edge. Both sides were the same, vertical.

I am finding the empennage kit instructions not as well written or organized as the wing kit. In the rudder section the instructions refer you to section 5.7, folded trailing edges, we don' t have those. Section 5.8 says to use shims to keep rudder spar straight and to weight it down, but it is being suggested here to not weight the rudder while riveting.

I think my rudder turned out fine. Better lucky than good :)
 
I lost some sleep over this last night :) . My rudder would rock a little while laying flat on one side but not the other. I couldn't wait to get to the shop to check it out.

I stood the rudder up on the bench, balancing on rudder horn, and put my digital level against trailing edge. Both sides were the same, vertical.

I am finding the empennage kit instructions not as well written or organized as the wing kit. In the rudder section the instructions refer you to section 5.7, folded trailing edges, we don' t have those. Section 5.8 says to use shims to keep rudder spar straight and to weight it down, but it is being suggested here to not weight the rudder while riveting.

I think my rudder turned out fine. Better lucky than good :)


That would be a good way to check for twist if you measure at the bottom rib and the top rib on both sides. If the opposing sides measure the same (top L & R, and bottom L & R), then you know it is straight.


Plans.... It is difficult to issue new release plans with absolutely zero errors. The first builders end up helping to scrub them out. If you were one of the later wing kits, you benefited from the earlier builders (attempts were made to issue corrections ASAP).
There have been very few errors mentioned so far in the emp/tail cone. Is that because few builders have gotten all the way through it? Possible.

What do you say builders? Have you found a lot of errors / issues in the emp/tail cone kit that you have not reported?
 
As a first time builder of a RV, I guess I got lucky. I used the 3M tape and followed the plans as written. Rudder trailing edge is straight as an arrow and no twisting at all. I thought the tape was very easy to use.
 
That would be a good way to check for twist if you measure at the bottom rib and the top rib on both sides. If the opposing sides measure the same (top L & R, and bottom L & R), then you know it is straight.


Plans.... It is difficult to issue new release plans with absolutely zero errors. The first builders end up helping to scrub them out. If you were one of the later wing kits, you benefited from the earlier builders (attempts were made to issue corrections ASAP).
There have been very few errors mentioned so far in the emp/tail cone. Is that because few builders have gotten all the way through it? Possible.

What do you say builders? Have you found a lot of errors / issues in the emp/tail cone kit that you have not reported?



A lot of errors/issues absolutely not! Some yes, but I know I could have not written a better manual. I'm a first time builder and very pleased with the quality of the kit and instructions. I have called Van's technical help about three times and quickly decided I should just read a little better before calling. With that said this website has been EXTREMELY helpful. While building the wing kit reading ahead to understand the manual was very helpful. The Tail kit has proven much more sequential. Most of the errors I have found have been on the order of wrong rivet callouts; however, as time has gone by I have gotten better at looking and thinking before riveting:). Thank you to VAF and Vans, it is a fun way to spend the day.
 
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A lot of errors/issues absolutely not! Some yes, but I know I could have not written a better manual. I'm a first time builder and very pleased with the quality of the kit and instructions. I have called Van's technical help about three times and quickly decided I should just read a little better before calling. With that said this website has been EXTREMELY helpful. While building the wing kit reading ahead to understand the manual was very helpful. The Tail kit has proven much more sequential. Most of the errors I have found have been on the order of wrong rivet callouts; however, as time has gone by I have gotten better at looking and thinking before riveting:). Thank you to VAF and Vans, it is a fun way to spend the day.

Thanks for the positive comments Marvin.

Regarding rivet length call outs... Keep in mind that the .5D / 1.5D rule, isn't a rule at all. It is a general guide line.
Often times a rivet length will be spec.ed that at first glance appears too short. The reason is that often the next longer size is actually a bit too long. Too long has a much higher risk for a novice builder to clinch over the rivet and then be tempted to remove it and try again (often with bad results). If the shorter rivet will still provide a shop head that meets the MIL spec for rivet head dimensions as shown in THIS DOCUMENT (and also detailed in chapter 5.4 of Section 5 of the construction manual), it is usually specified. If a builder chooses to use one slightly longer, and can properly install it, that is of course totally fine.

This is not to say that there wont still be occasional errors on rivet call outs, so builders should always be cross checking. If an error is found, where a specified rivet can't produce a proper sized rivet head that meets the "MIL Spec", then please let Van's know.
 
We have finished our RV-14 rudder as per VAN's plans. Our trailing edge is bonded with 3M adhesive tape, riveted and it is nice and straight.
One side of the rudder now sits flat on the workbench but if we turn our rudder over it has a twist of about 20mm causing it to rock.

Please post how your RV-14 rudder sits with each side up (ie flat) when on a level workbench? Does anyone else see a twist on one side of their rudder?
DSC_0064.jpg


This may not affect our rudders performance. Thoughts?
I just finished my rudder today and have the exact same result as rocky005. I used two 3/4" aluminum angles to sandwich the TE together. Used 3M-5200 in lieu of tape. The TE hung over the edge of my bench so the clecos would clear and the angle was flat on the table. Shims were used under the rudder to keep the TE flat on the bench. Waited 2 days and riveted in the same manner. There was no load or bind on the rudder at any time that would have changed the shape of the structure. TE turned out straight.

The way the left and right stiffeners are riveted to each other and then to the spar, how can the geometry turn out any other way? Please be sure to post Van's reply.
 
Finally got around to checking mine. I used the 3M tape and aluminum angle to keep the edge straight. Here are the results.

ocM6HkZl.jpg

vpG6j3xl.jpg

rQytT5El.jpg
 
From Sterling Langrell at Van's regarding my pictures.

"The RV-14 rudder design (similar to 6,8 and early 7 rudders) if built perfectly strait will not lay
flat on a table. The fact that one side of yours does lay flat and is lifted the 7/16 when you flip
it over tells me you have a twist in the rudder. Your actual twist will only be half of that
measurement at 7/32. This is not enough of a twist that any action needs to be taken to
correct it."
 
Based on the reply that HeliCooper got from Van's, I feel much better about my rudder. It does not lay perfectly flat on either side. At the bottom of the trailing edge, one side is lifted by 12/32, and when I flip it over, it is lifted by 9/32.

So the difference is 3/32.

If I understand correctly, only half of that (3/64) would represent a slight twist in my rudder.

Did I read Van's reply correctly?


bschweinberg
R-14A
www.mykitlog.com/bschweinberg
 
Based on the reply that HeliCooper got from Van's, I feel much better about my rudder. It does not lay perfectly flat on either side. At the bottom of the trailing edge, one side is lifted by 12/32, and when I flip it over, it is lifted by 9/32.

So the difference is 3/32.

If I understand correctly, only half of that (3/64) would represent a slight twist in my rudder.

Did I read Van's reply correctly?


bschweinberg
R-14A
www.mykitlog.com/bschweinberg

Yes.
Your rudder has about 3/64" of twist.
I think it will still fly just fine ;)
 
Yes.
Your rudder has about 3/64" of twist.
I think it will still fly just fine ;)

Hi Scott

Thanks for the reassuring words.

I also received a response from Ken to my email to VANs support, I hope its OK to post it here:-
Subject: Re: Fwd: RV-14 Rudder symmetry?
It's doubtful that you'll notice any difference. Almost every RV requires some sort of yaw trim correction when it flies. The amount is a sum of many forces -- this very small asymmetry is just part of a much larger pie and not all worth concern

Forwarded to: kenS


So looking forward to finishing our empennage, its a great kit by the way.
 
Salto

Well my son and I finished the rudder today ( still trying to work out how to get a couple of rivets in inside the bottom brace) and it lays absolutely flat on the table both sides. Scott said in a previous post that it wouldn't so I'm blessed if I know what to think now. Trailing edge is straight.... found by taking the white plastic off the back rivetting tool and low pressure as instructed the double countersinks set perfectly. Each job seems to be an adventure at the moment...great kit and instructions.
 
Rudder Twist

Add me to the list of the rudder twist club.
I used the double side tape called for in the plans on the trailing edge. I then clecoed the t/e to a piece of flat steel with holes drilled to accept the clecos. No other weights were used.
The t\e came out perfectly straight, but when laid on a flat surface there appears to be a twist. One side sits completely flat, but when flipped over, the lower portion of the rudder is approx. 1/2" off the surface.
After reviewing the other posts in this thread, I think I'm "ok", but just putting this out there for reference.
Not sure what I would do different if I did it again. Maybe make sure I wasn't "pulling" portions of the rudder flat to the steel with the clecos prior to riveting.

The flat side:
ry%3D480


The non-flat side
ry%3D480


The difference:
ry%3D480
 
Rudder Twist

The process zi used to end up with it dead flat on the table both sides was double sided tape
cleco'd
made sure it was straight
let the tape go off for a couple of days
started from middle and rivetted 4 at a time with the process described
didn't clamp anything to it, let the tape and clecoe's do the work.
I have since rolled the leading which I must say after the careful, gentle and conscientious approach to the rudder assembly became a brutal affair.
Didn't enjoy that process one bit!!
Havent yet checked to see if i have induced a twist.
 
Rudder twist test?

Add me to the list of the rudder twist club.
I used the double side tape called for in the plans on the trailing edge. I then clecoed the t/e to a piece of flat steel with holes drilled to accept the clecos. No other weights were used.
The t\e came out perfectly straight, but when laid on a flat surface there appears to be a twist. One side sits completely flat, but when flipped over, the lower portion of the rudder is approx. 1/2" off the surface.
After reviewing the other posts in this thread, I think I'm "ok", but just putting this out there for reference.
Not sure what I would do different if I did it again. Maybe make sure I wasn't "pulling" portions of the rudder flat to the steel with the clecos prior to riveting.

The flat side:
ry%3D480


The non-flat side
ry%3D480


The difference:
ry%3D480


Update to my post above:
Not to dwell dwell on my possibly twisted rudder, but I had an idea yesterday as I was hanging my rudder from the ceiling for storage. I remembered that I had purchased one of those rotary laser levels for use while building my shop. I thought it be useful to test my rudder for "straightness".
Here's what I did.
For light lifting and storage of components, I mounted a piece of unistrut to the ceiling. You can also see the rotary level I used.
ry%3D480


Here's the rotary level beam aligned with the piece of unistrut on the ceiling.
ry%3D480


I used a piece steel rod to run through the rod end bearings and rubber bungee cords with one of the hooks removed to hang the rudder.
ry%3D480

ry%3D480


The rudder hanging from ceiling.
ry%3D480


Laser aligned with top part of rudder.
ry%3D480


Here's the lower part of the rudder with piece of paper attached to show laser line. The laser line is difficult to see, but it is approximately 1/8" to left of the rudder centerline.
ry%3D480

I'm not overly concerned with my slight rudder twist, I just thought this would be an interesting idea.
Would this method be an accurate check, or am I missing something?
 
As long as you know that the laser was aligned with the hinge line of the rudder in its hanging state (the placement of the eye bolts and your use of "S" hooks could be moving it off center of your reference of the Uni-strut center line), it should be a very accurate method.
 
As long as you know that the laser was aligned with the hinge line of the rudder in its hanging state (the placement of the eye bolts and your use of "S" hooks could be moving it off center of your reference of the Uni-strut center line), it should be a very accurate method.

Thanks. I will check the S hooks and eye bolts that are attached to the uni-strut to make sure everything is centered.
 
Add me to the list of the rudder twist club.
I


I'm on the same boat. Followed the instruction to the letter. I've used the 2 sided tape. A little shim on the bottom of the opposite bottom side before back-riveting. The TE is perfectly strait but the side that was facing down while back-riveting is flat on the table. The opposing side shows a difference of 12mm. If I understand correctly, this makes for a 6mm twist which seems to be well within build parameters, right?


It looks that final results varies from one build to the other. Could it be caused by a combination of parts manufacturing tolerance with builders own contribution?
 
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