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Rudder stops

Maxrate

Well Known Member
It's going to be a while before the wings arrive from Vans so I am trying to finish up as much on the tail as possible. After looking over several builder sites it looks like there are two different types of rudder stops. One uses a Delrin material http://www.jeffsrv-7a.com/FUSELAGE/04-07-22.htm as this builder has, and the other looks like the standard external stops that Vans has you fabricate. http://websites.expercraft.com/morristull/index.php?q=log_entry&log_id=17910 as this builder used. Both look like they work ok but the trim necessary on the bottom rudder canoe is drastically different. Im building the tail dragger version so I know clearance between the tail wheel spring and rudder fairing is going to be an tight already. Anyone that can weigh in especially with pics would be great!
 
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It has been a great deal of discussion about the rudder stop on this site so a quick search will yield plenty of info.. The internal rudder stop which one of the member here makes them and sell them very reasonably priced, look very attractive. But a few (I believe including Vans) recommend against it as they think it will put too much force (in an angle that it was not designed for) on the hinge and the rivets that hold the hinge.

The one that Vans has you fabricate works really well but it is not nearly as attractive looking. If you end up fabricating them? don't go too crazy with the angles that is given till you have mounted the rudder can test a good fit. Even then after you rivet them in place, the fit will come out of adjustment and you may have to shave a bit more for best fit.

Mehrdad
RV7A - IO360M1B
 
Be Careful with Vertical Positioning Too

It has been a great deal of discussion about the rudder stop on this site so a quick search will yield plenty of info.. The internal rudder stop which one of the member here makes them and sell them very reasonably priced, look very attractive. But a few (I believe including Vans) recommend against it as they think it will put too much force (in an angle that it was not designed for) on the hinge and the rivets that hold the hinge.

The one that Vans has you fabricate works really well but it is not nearly as attractive looking. If you end up fabricating them? don't go too crazy with the angles that is given till you have mounted the rudder can test a good fit. Even then after you rivet them in place, the fit will come out of adjustment and you may have to shave a bit more for best fit.

Mehrdad
RV7A - IO360M1B

Aligning the stop with the flange of the rudder horn will make the cable rub on the opposite side. I had to move mine :)

Jim Sharkey
RV6 - Phase 1
 
After looking over several builder sites it looks like there are two different types of rudder stops. One uses a Delrin material http://www.jeffsrv-7a.com/FUSELAGE/04-07-22.htm as this builder has.

Jeff hasn't made these for several years now. Myself and another member of our EAA chapter have picked up the "project". We've made over 200 of them now and never had a builder unhappy with them, to the best of our knowledge anyway. We're not the designer of this part, but we liked the piece for ourselves, and decided to share our ability to make them with the rest of the builder community.

Here's the latest thread for them: http://www.vansairforce.com/community/showthread.php?t=54682. There are a couple of pictures and a cad drawing of one of the original stops in case you want to make your own, although we've made ours much thicker and stronger than the originals, for whatever that's worth.
 
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Craig has a great deal. Rene' and I got together on this years ago, I did make my own. This design works better than Jeff's design and was a modified version of Jeff's design. BTW I have had both designs... You will be happy... order one from Craig.
 
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Craig,

I like your idea of positioning the stop above the hinge instead of below. It looks like your picture shows the rudder fairing cut approx like VANs says to. Have you heard of anything negative on the stops having hinge stress issues like Mehrdad mentioned. Also, do you have anymore to sell. I would love to purchase one.

Thank's
 
Have you heard of anything negative on the stops having hinge stress issues like Mehrdad mentioned.

There have been a couple builders (engineers, I suppose) who have determined that there would be stress issues, but I've never heard of any actual problems or data to support their findings. Also, we've almost doubled the thickness on our version compared to the original rudder stops designed by Jeff and Rene'. To the best of my knowledge, none of those thinner rudder stops ever failed either, and that was several years ago.

Also, do you have anymore to sell. I would love to purchase one.

Yes, I have a few left from this batch, and we just ordered some more material to start the next batch.
 
Craig,

I like your idea of positioning the stop above the hinge instead of below. It looks like your picture shows the rudder fairing cut approx like VANs says to. Have you heard of anything negative on the stops having hinge stress issues like Mehrdad mentioned. Also, do you have anymore to sell. I would love to purchase one.

Thank's

Installed the internal rudder stop on the top of the bottom hinge, as noted above. Found that, for some reason, the rudder spar was only contacting the stop on the inner corners. Some careful sanding down got full-face contact. But...by my measurements, I'm getting only the minimum 30 degrees of rudder travel (I may leave it thus until flying, rather than continue monkeying with the stop for now). Note that all rod ends are in line, at the spec'd distances, and clearances on the skins (VS-to-rudder) are close but good.

I'm not sure what happened here to cause this, and it's not a huge issue to fix, but I hate not knowing what caused the "issue"...any ideas? (and thought I'd post this for others using the stop to look for...).
 
Contacting at corners

Installed the internal rudder stop on the top of the bottom hinge, as noted above. Found that, for some reason, the rudder spar was only contacting the stop on the inner corners. Some careful sanding down got full-face contact. But...by my measurements, I'm getting only the minimum 30 degrees of rudder travel (I may leave it thus until flying, rather than continue monkeying with the stop for now). Note that all rod ends are in line, at the spec'd distances, and clearances on the skins (VS-to-rudder) are close but good.

I'm not sure what happened here to cause this, and it's not a huge issue to fix, but I hate not knowing what caused the "issue"...any ideas? (and thought I'd post this for others using the stop to look for...).

I also have installed the internal stop and find that it is hitting the corners against the forward spar of the rudder. I have double checked measurements and they are good. I think the problem is that these internal stops are dependent on the distance the rudder is away from the fin. My rudder is close to the fin. Maybe I should move the rudder aft a little.

I'm working on modifying it now. Any other suggestions or comments about the fit of the internal rudder stop and distance of rudder from fin are appreciated.

UPDATE: I trimmed back the two ends of the internal stop, little by little, checking fit and deflection as I went until I got the stop to contact the rudder spar just as the rudder got to within 1 1/8 inches from the trailing edge of the elevators. Seems like an excellent stop. I do see there is enough flex in the rudder that even with the stop hitting 1 1/8 inches from elevator that I can pull the rudder to hit the elevators.
 
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I also have installed the internal stop and find that it is hitting the corners against the forward spar of the rudder. I have double checked measurements and they are good. I think the problem is that these internal stops are dependent on the distance the rudder is away from the fin. My rudder is close to the fin. Maybe I should move the rudder aft a little.

I'm working on modifying it now. Any other suggestions or comments about the fit of the internal rudder stop and distance of rudder from fin are appreciated.

UPDATE: I trimmed back the two ends of the internal stop, little by little, checking fit and deflection as I went until I got the stop to contact the rudder spar just as the rudder got to within 1 1/8 inches from the trailing edge of the elevators. Seems like an excellent stop. I do see there is enough flex in the rudder that even with the stop hitting 1 1/8 inches from elevator that I can pull the rudder to hit the elevators.

I think you're right about the angle being dependent on the distance of the rudder spar from the hinge point, as I have mine "close" as well. I did just what you did, trimmed the ends bit by bit until I got full contact, and then I laid the stop on a piece of metal and scribed the extensions of the faces so that I could accurately measure the angle...just at 30 degrees. So I sloooooowly sanded off teeny bits of each face, ensuring full-face contact, until I got to 32-33 degrees (at which point the distance to the elevators is 1-1/2" both sides), which is in the middle of the spec. I'll leave it there until flying, and if I need a little more, I can adjust it then.

I could have moved the rudder further aft, I guess, but I didn't want a larger gap between VS and rudder.

One thing I really like about the internal stop is that if something changes in the future (if I *do* have to move the rudder aft, or want more swing, etc., I can just get another one, redo it and bolt it in place without having to drill out rivets on the side of the fuselage, etc.
 
Craig,

Iv'e seen Pics of other guys that have placed the stop between the rudder hinge instead of on top of it. Is there any advantage to installing it this way.

Thx
 
Yep....we did it this way

Craig,

Iv'e seen Pics of other guys that have placed the stop between the rudder hinge instead of on top of it. Is there any advantage to installing it this way.

Thx

....on our -10. Above the hinge tends to bend the bolts, whereas between the hinge plates, it's rock solid with the bolts in shear,

Best,
 
There have been a couple builders (engineers, I suppose) who have determined that there would be stress issues, but I've never heard of any actual problems or data to support their findings.

On the other hand....have you ever seriously reviewed the stress issues?
 
Internal Rudder Stop on a 6

:confused: Some time ago I installed the internal rudder stop purchased from the supermoderater, after having read some of the discussions about stresses that Dan Horton suggests we consider.

Over time it became apparent to me that any supporting data in the negative, I did not want to be associated with personally.

So my solution was to set up my sweet delrin internal internal stop to the proper angles of rudder travel, and then to install the exterior aluminum stops to pick up the load slightly after the delrin did. This prevents the banging that I was concerned about, but cannot overly stress the hinge assemble. It also uses the delrin to its design advantage, so I have not wasted any coin.

I should hopefully see very infrequent full rudder deflection, as was demonstrated to me in my transition training in Vernonia, since brakes are used so often in ground steering, and full deflection on short final indicates the landing is likely beyond my capability this early on. Later, who knows.

I do not care what it looks like, I just can't be worrying what is going on back there where I can't see.

Thanks Dan for bringing it up. :)

Mike Bauer
RV6 N918MB Awaiting Inspection
 
Pierre,

What did you use to shim the block to get the perfect fit.

PS: I flew with a guy the other day who was a turbine Air Tractor driver. Looks like a real Cadillac.........:D

Thanks
 
On the other hand....have you ever seriously reviewed the stress issues?

Dan,

When do we expect these stops to come under stress? Only 2 conditions I can imagine are at full deflection either by pilot input or in the case of an unrestricted/unrestrained rudder being blown by the wind. Of these 2 which one are we most concerned with? I believe I have read of rudders being bent by the wind when a rudder gust lock was employed.

Dave
 
I'm still lost on the benefits. If the complete rudder control mechanism was hidden from view, then I see the advantage. But once you add exterior rudder cables and the rudder horn to the equation, then hows a piece of triangular aluminum for the stop going to make much difference in looks. It's that cable & linkage that isn't pretty!

L.Adamson --- RV6A
 
Mark, mine was too thick.....

Pierre,

What did you use to shim the block to get the perfect fit.

PS: I flew with a guy the other day who was a turbine Air Tractor driver. Looks like a real Cadillac.........:D

Thanks

....since the blank piece came from Spruce and after I cut it out on my bandsaw, I had to spend quite a bit of time on my belt sander to thin it down to fit.

Yep, the 'Tractor is pretty much the ag airplane of choice but the Thrush drivers won't change airplanes for anything.

Best,
 
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Pierre,

I see. You actually fabricated your own. The one I purchased from Craig is too thin and will need a shim. As a Tech guy is there any recomendations on what you would use. Are AN washers OK?

The most amazing thing to me about Ag ops is how far GPS technology has advanced operations. He was able to operate into the night with no flagmen.......Amazing.

Thanks for the input.
 
On the other hand....have you ever seriously reviewed the stress issues?
Dan,
When do we expect these stops to come under stress? Only 2 conditions I can imagine are at full deflection either by pilot input or in the case of an unrestricted/unrestrained rudder being blown by the wind. Of these 2 which one are we most concerned with? I believe I have read of rudders being bent by the wind when a rudder gust lock was employed.
Dave
I should hopefully see very infrequent full rudder deflection, as was demonstrated to me in my transition training in Vernonia, since brakes are used so often in ground steering, and full deflection on short final indicates the landing is likely beyond my capability this early on. Later, who knows.
I am one of those who query this "modification" for stress reasons.

In answer to
When do we expect these stops to come under stress? Only 2 conditions I can imagine are at full deflection either by pilot input or in the case of an unrestricted/unrestrained rudder being blown by the wind
I am not really concerned with either. They will not kill you, and most likely, if any damage were to result, visible on a walkround check, and just cost ??? (or $$$!) / time.

My concern is a 3rd condition - a (presumably) inadvertant tailslide. This, to me, is the ultimate "stress" for a Rudder Stop (and Elevator). It takes a scr*wed up aerobatic manouevure, and a mishandled recovery... however, I have seen both together, both by me :( and more frequently, students... If you have not done a tailslide, please let me assure you the control forces as they reverse are harsh, and if you fail to hold them, a real hard/fast application of full rudder / elevator :confused:

The problem in the RV case is that if the "modified" rudder stop fails (in fact, I doubt it will be the stop that fails, it will be the rudder) what now stops it? Well, the elevator, and rudder jammed into elevator only equals one outcome :mad:

So to me it is a risk benefit analysis. The "benefit" is a slightly more sexy looking rudder stop. The risk? Death to both occupants probably.

So to
but I've never heard of any actual problems or data to support their findings
I am glad you have heard of no problems... just when/if we do, they are likely to be major. As for data - surely it is not us that have to provide the data? Van's provides the design, presumably to an accepted protocol / design standard. It is surely up to those who choose to override this should provide the data to "prove" their alternative is equally, or more, safe than the Van's design?

Please do not get me wrong. Anybody who chooses to modify their design at their risk I am fine with - we all take risk/benefit decisions every day. My concern is with those who encourage others, without expressing all the facts, to modify the Van's design, and even make $$ out of it. Go back to the original RV-3 design issues and fatalities, and the RV-8 prototype accident... In my interpretation, Van's design in both cases was proved correct, but not far off optimal :eek:

Andy
RV-8 G-HILZ
 
My concern is a 3rd condition - a (presumably) inadvertant tailslide. This, to me, is the ultimate "stress" for a Rudder Stop (and Elevator). It takes a scr*wed up aerobatic manouevure, and a mishandled recovery... however, I have seen both together, both by me :( and more frequently, students... If you have not done a tailslide, please let me assure you the control forces as they reverse are harsh, and if you fail to hold them, a real hard/fast application of full rudder / elevator :confused:

The problem in the RV case is that if the "modified" rudder stop fails (in fact, I doubt it will be the stop that fails, it will be the rudder) what now stops it? Well, the elevator, and rudder jammed into elevator only equals one outcome :mad:

Is this event within the designed flight envelope in the first place?
 
I have a similar setup on my RV6 build. It’s made out of aluminum bar stock. The original rudder stop from the kit builder I bought it from made two of these (top pic below), so I decided to use both of them, one on the top of the rudder bottom clevis mount and one on the top. I needed a spacer between the clevis mounts to not put too much squeeze on the bottom rudder rod bearing so I couldn’t insert it.

74D02BC1-6B2A-4878-8637-4DB45F7C02E5.jpg

A64754B7-9C45-4B80-AF6F-9DB9FA32C0D8.jpg

When I did this I had to file the two pieces to make them match exactly, and that resulted in a max rudder deflection of 35* (the upper limit), and too close to the limit for my comfort, so I made a new one out of 1/8” stock. I still bolted it to the bottom rudder rod end clevis using a spacer to prevent squeezing the clevis too much, but it works very well. My max deflection is now 32.5*, which is right where I want it.
To me, I prefer the internal rudder stops, and they are easier to install and adjust.
 
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Anyone have the cad file for the internal stop? The only link I could find is dead.
I don't see a copyright notice on it so here's a PDF of the design Rene Bubbeman did 17 years ago.

If you email me ([email protected]) your email address I will send you a DXF and/or a DWG file of it.

--
Joe
 

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