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Non-engineer rudder idea for OSH gust events

DeltaRomeo

doug reeves: unfluencer
Staff member
Entrepreneurship / Marketing major chiming in…..be gentle.

Please don’t call me an idiot too fast, but if you could connect two pieces of angled aluminum with a full length hinge, pad the inside surfaces, place that along the entire trailing edge length of the rudder, then hold that in place with bungee type cords running to the outboard ends of the HS.

Three or four small C-clamps gingerly holding the hinged contraption in place.

In a wind event, wouldn’t this apply the same tension along the entire length of the rudder?

Silly drawing below, note the bungee that runs in FRONT of the VS for stability.

A sort of ‘last resort’ OSH thing, not a use-all-the-time type thing.

Apologies in advance if this type thing has been discussed before ….. I haven’t seen anything that applies pressure along the entire trailing edge length of the rudder. That’s what I’m trying to address here

Shields up…crawling under the porch.

V/r,dr

IMG_4524-XL.jpg
 
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I think that’s probably what it would take to prevent the kind of damage we saw (basically even with gust lock, the rudders were “twisted” if the lock held, and just bashed to pieces if it failed).

But, I am wondering if instead of all that effort, how hard would it be to, at events like this where you know you aren’t gonna fly again for a few days, AND we knew a storm was coming several hours in advance, to just remove the rudder altogether and stow it in the cabin, put it back on in the morning. If you made your tail light with a plug, it’s only like 3 bolts right?

Just another idea…
 
We use a simple rig called a whiffletree or Whippeltree to even distribute loads across a structure in the structural test lab. I believe that such a rig could be made from aluminum tubing or angle and some small diameter cable or low stretch line and i stalled on either side of the rudder trailing edge and anchored to the horizontal stabilizer tips or hinge points as others have done.

https://en.m.wikipedia.org/wiki/Whippletree_(mechanism)

An alternative would be a rig made from line similar to the line groups used in rigging square parachutes and paraglider canopies. Lightweight, compact, and inexpensive.

https://en.m.wikipedia.org/wiki/Paragliding#Wing

- larosta
 
I think the trick is to have something that would simulate what you would do with your hands if you were holding the control surface during the storm.

You would probably let it move a little, and as it got closer to the stops, you would push harder.

If you were working the rudder pedals to hold it in place, you would do the same - allow it to move a bit, but push harder as you get close to the stops to avoid a slam.

Something like the anti-splat ultimate gust lock, but with hydraulic dampeners and springs to allow some movement, but not allow the control surface to hit the stops hard.
 
Maybe stupid

This may sound stupid but how hard would it be to just take off the rudder for the week? P.S. I'm not a builder
 
Digging a little deeper.

I think the trick is to have something that would simulate what you would do with your hands if you were holding the control surface during the storm.

You would probably let it move a little, and as it got closer to the stops, you would push harder.

If you were working the rudder pedals to hold it in place, you would do the same - allow it to move a bit, but push harder as you get close to the stops to avoid a slam.

Something like the anti-splat ultimate gust lock, but with hydraulic dampeners and springs to allow some movement, but not allow the control surface to hit the stops hard.

What would be the tension on a rudder cable with a 90 ft-lb torque? 360#? The Gustbuster guy calculated 90lb for the tall 7/9 rudder is that in the ball park?

What torque on the rudder horn is acceptable? Is it the same for an 8 (.020 skin), 7/9, 14? That is three are different designs.

To the OP . . . Gotta say, the idea of something covering maybe 18" of the TE might me enough to carry the loads with a single cord. A bungee with rope stop backup on both sides. Structure to transfer the loads to the elevator safely also are a potential factor. We need something easy to install, carry the loads, and be easily stowed. If the 7/9 rudder was restrained just above the HS then we have about 20" from the pivot making about 50 lbs to restrain. 18" of TE contact gives 3 lb/in if that means anything.

My mind keeps slipping into Vans design world for the answers.

I'll bet some Vans engineers are talking about this already. 80% chance (opinion) they will develop a recommendation as a result of all this.
 
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I ordered a couple of Steve Melton's gust locks for the rudder as backup for my Anti-splat gust lock. As in the OP, it seems reasonable to support the rudder at at least one other point along the trailing edge in more extreme conditions rather than just relying on pinning the horn or blocking the pedals.
 

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Steve made a nice silent video and he installed the elevator lock in 30 seconds. One side was rope only, the other contained a bungee with a short rope loop, just enough for installation.
 
Torque

As I read through the threads, it seems that twisting torque along the trailing edge from a fixed end and a free end caused the damage. And when a midpoint was used, the lever arm was greatly reduced and there was less potential for damage.

Which leads me to believe that if the rudder horn was secured and a gust lock at the opposite end of the trailing edge (rudder top), the rudder would have a much better chance of survival due to reducing twisting torque.

Which says to me that a high & low gust locks are the way to go.
 
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I wonder how a couple wedges of fairly dense foam between the rudder and inboard ends of the elevators would work?? Big enough to fill the entire area between rudder and elevators.

Dense as in pool noodles or such.

Would need some way to keep the wedges in place.

Would absorb gust loads and return to neutral all on its own.
 
After seeing some of the damage to rudders at HBC, Just yesterday I was experimenting with new ideas to secure the rudder. I do believe it MUST be supported at the trailing edge for best results/hopes of no damage. My idea was elastic cords placed in two or three places at the back. Even considered dr's idea of a full trailing edge device.

I did fabricate my idea and tried it out. I feel the elastic theory is a good idea for one main reason. If the rudder is subjected to loads and can actually move some, then it will essentially dump "a part" of the load as the rudder tries to weathervane. The idea is the elastic cords would stop the rudder before it can make contact with the stop on the downwind side. He's the weird thing. As I stood there with this in place it feels as if the rudder is almost loose despite tension in place on both sides from the elastic cords. It's because of the tension being exerted on the pulling side. In other words it took very little pressure from my fingers to move it left or right because the elastic cords were assisting by pulling. The further it was displaced from center, the more tension the opposite side applied trying to center it back up. In theory as the wind blows the rudder to one side the tension on that side lessons so that at the stop it's nearly limp on that side while the opposite side is under great tension attempting to pull it back closer to center. I just could not image as loose as it felt, (although it really wasn't loose), with everything in place, leaving it like this to weather a storm. Still thinking about this stuff and interested in others ideas as well.
 
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Secure the rudder hard over to the rudder stop instead.

That's what I always do, using bungees to the tie down, but I have a TW, so between not being up in the wind, the TW springs, and the bungees, I have never had trouble (knock on aluminum).

I would think even on the A models, with the tail up in the wind, securing it hard over would be more reliable, since you basically need to keep everything teetering on a knife edge with many of the gust lock ideas, and as soon as it moves away from center, the "oscillation" so to speak becomes bigger and bigger.

I saw the picture of the guy who secured their rudder with duct tape, which also seems like a good idea considering the alternative. 3 wraps of duct tape, high, middle and center, would seem to do the same thing.

Humans are really bad at judging risk, and I was probably like many, watching the radar, listening to the forecast, and thinking "It probably won't be _that_ bad...".

But, every year, it's _that_ bad, and things get broken. We should just setup on the beautiful day that we arrive assuming that a derecho is headed here by this evening and take the necessary precautions assuming the worst. If it never comes, or isn't as bad as predicted, bonus.

This may sound stupid but how hard would it be to just take off the rudder for the week? P.S. I'm not a builder

That's my suggestion posted above: For most, they are there at least 3 days, and many for the week. We almost always have advanced warning of _some_ kind of high winds coming, by at least a few hours. Go out there, remove the 3 attach bolts and the control cables, stash the hardware and the rudder in the cockpit, put it back on after the storm is past. Only wrinkle is that many probably have hard wired tail lights, but I would rather splice a wire back or convert it to a plug than fix a rudder.
 
After seeing some of the damage to rudders at HBC, Just yesterday I was experimenting with new ideas to secure the rudder. I do believe it MUST be supported at the trailing edge for best results/hopes of no damage. My idea was elastic cords placed in two or three places at the back. Even considered dr's idea of a full trailing edge device.

I did fabricate my idea and tried it out. I feel the elastic theory is a good idea for one main reason. If the rudder is subjected to loads and can actually move some, then it will essentially dump "a part" of the load as the rudder tries to weathervane. The idea is the elastic cords would stop the rudder before it can make contact with the stop on the downwind side. He's the weird thing. As I stood there with this in place it feels as if the rudder is almost loose despite tension in place on both sides from the elastic cords. It's because of the tension being exerted on the pulling side. In other words it took very little pressure from my fingers to move it left or right because the elastic cords were assisting by pulling. The further it was displaced from center, the more tension the opposite side applied trying to center it back up. In theory as the wind blows the rudder to one side the tension on that side lessons so that at the stop it's nearly limp on that side while the opposite side is under great tension attempting to pull it back closer to center. I just could not image as loose as it felt, (although it really wasn't loose), with everything in place, leaving it like this to weather a storm. Still thinking about this stuff and interested in others ideas as well.

Elastic is a bad idea...look into resonance. A perfect example is a homemade harmonica...
 
As I read through the threads, it seems that twisting torque along the trailing edge from a fixed end and a free end caused the damage. And when a midpoint was used, the lever arm was greatly reduced and there was less potential for damage.

Which leads me to believe that if the rudder horn was secured and a gust lock at the opposite end of the trailing edge (rudder top), the rudder would have a much better chance of survival due to reducing twisting torque.

Which says to me that a high & low gust locks are the way to go.

I agree with securing the rudder at the top, but difficult for us “A” models. Perhaps, a lightweight folding step?
 
I'll chime in on this one as well. Doug has a good concept for holding the tail. It would be absolutely the best if you could support the entire trailing edge, but that requires flying around with 2 pieces of metal approximately 4 ft long. Not really practical.

For the guys asking about rudder horn moments, back of the napkin math here with assumptions on actual size since I don't have a plane available to measure right now.... Rudder is 20" wide at the bottom, 12" wide at the top, and 40" tall (all these are guesses). That gives you 640 sq inches of surface. Vans recommends 25 degrees of rudder deflection in the rigging section which present 240 sq inches into the wind at max deflection. Using some basic formulas, this generates ~120 lbs of force on an approximate 8 inch moment arm to the center of pressure. These numbers give you 90 ft-lbs hinge moment during allowable flight maneuvers. The arm between the hinge and rudder cable attach isn't 12", so in flight the loads in the rudder cables can be higher than 90 lbs.

As for the elastic idea, the rudder only weather vanes in a headwind. In a tailwind you're in an unstable equilibrium with a direct tailwind, and the load on the rudder will increase as deflection increases. Unfortunately you would need an active feedback loop to keep the rudder centered in a tailwind, so I think the best option would be to lock it solid with no movement and deal with the forces that are generated.

If you want to grab the trailing edge to secure the rudder in a single spot, it would be safest to grab it just below mid-height. If you want more secure, grab it from the counterweight and ~1/3 up the trailing edge. If you want belt and suspenders, grab it in 3 spots. I think my idea would be a printed piece that went over the top of the counter weight and was run downward to the elevator with paracord, and then 2 pieces of printed plastic that grabbed the trailing edge ~1/3 and 3/4 down the trailing edge and ran paracord forward to the elevator.
 
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I wonder how a couple wedges of fairly dense foam between the rudder and inboard ends of the elevators would work?? Big enough to fill the entire area between rudder and elevators.
I think this would be great if used in conjunction with a counterweight lock. That would give you support ~1/3 from the bottom, and at the top, which might be just enough to hold the loads.

The foam fillers on their own would leave the top of the rudder free, and it looks from some of the photos like the top was able to flex independent of the bottom in one or two cases, although it's possible that this happened when the bottom of the rudder hit the elevator and the top's inertia kept it going... The lead in the counterbalance wouldn't do you any favours in that case.
 
I'll chime in on this one as well. Doug has a good concept for holding the tail. It would be absolutely the best if you could support the entire trailing edge, but that requires flying around with 2 pieces of metal approximately 4 ft long. Not really practical.

For the guys asking about rudder horn moments, back of the napkin math here with assumptions on actual size since I don't have a plane available to measure right now.... Rudder is 20" wide at the bottom, 12" wide at the top, and 40" tall (all these are guesses). That gives you 640 sq inches of surface. Vans recommends 25 degrees of rudder deflection in the rigging section which present 240 sq inches into the wind at max deflection. Using some basic formulas, this generates ~120 lbs of force on an approximate 8 inch moment arm to the center of pressure. These numbers give you 90 ft-lbs hinge moment during allowable flight maneuvers. The arm between the hinge and rudder cable attach isn't 12", so in flight the loads in the rudder cables can be higher than 90 lbs.

As for the elastic idea, the rudder only weather vanes in a headwind. In a tailwind you're in an unstable equilibrium with a direct tailwind, and the load on the rudder will increase as deflection increases. Unfortunately you would need an active feedback loop to keep the rudder centered in a tailwind, so I think the best option would be to lock it solid with no movement and deal with the forces that are generated.

If you want to grab the trailing edge to secure the rudder in a single spot, it would be safest to grab it just below mid-height. If you want more secure, grab it from the counterweight and ~1/3 up the trailing edge. If you want belt and suspenders, grab it in 3 spots. I think my idea would be a printed piece that went over the top of the counter weight and was run downward to the elevator with paracord, and then 2 pieces of printed plastic that grabbed the trailing edge ~1/3 and 3/4 down the trailing edge and ran paracord forward to the elevator.

The 7 tall/9 rudder is 936 in^2 without the glass ends. The center of the area is 12" from the pivot line. .016" skin.

The 7-short aka 8 rudder is 718 in^2 w/o glass ends. .020" skin
 
I'll chime in on this one as well. Doug has a good concept for holding the tail. It would be absolutely the best if you could support the entire trailing edge, but that requires flying around with 2 pieces of metal approximately 4 ft long. Not really practical..

what if the trailing edge of the rudder was built strong enough so as to just attach that tie downs.... basically build the 4ft long brackets into the rudder?

did this sort of damage happen primarily to the Vans planes...or equally to the Cessna's and other stuff?... is there something about the Vans designs that is making the gust lock question difficult?
 
The 7 tall/9 rudder is 936 in^2 without the glass ends. The center of the area is 12" from the pivot line. .016" skin.

The 7-short aka 8 rudder is 718 in^2 w/o glass ends. .020" skin

As soon as I find the time, I'm going to install the original 8 rudder I built (supplied with the early 7 kits),
seeing all this damage definitely has increased my incentive.
 
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This may sound stupid but how hard would it be to just take off the rudder for the week? P.S. I'm not a builder

That's my suggestion posted above: For most, they are there at least 3 days, and many for the week. We almost always have advanced warning of _some_ kind of high winds coming, by at least a few hours. Go out there, remove the 3 attach bolts and the control cables, stash the hardware and the rudder in the cockpit, put it back on after the storm is past. Only wrinkle is that many probably have hard wired tail lights, but I would rather splice a wire back or convert it to a plug than fix a rudder.
The talk about removing the rudder has pretty much been only discussing the act of taking the rudder off the plane. Thinking it is only 3 bolts and the rudder cable bolts, oh yes, the light wiring too, is all that needs to be done is looking at it in its simplest form. Although it may seem straightforward in theory, the reality is there is some difficulty in doing so in real life and to do it in an environment such as an air show vs in the hangar may also prove a little more troublesome than first thought.

However easy or difficult the removal of the rudder is in the field, it will pale to the difficulty of putting the rudder back on in the field. Those freaking washers and nuts can be a real pain to get installed on those three bolts in a shop. I cannot imagine how much cussing I would be doing trying to put those bolts, nuts, and washers on out there in that environment. Ok, I can imagine it. I have had to do so before, and at OSH no less, just a few short years ago. I am going to be on my third rudder now having had it destroyed twice now at OSH.
 
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As soon as I find the time, I'm going to install the original 8 rudder I built (supplied with the early 7 kits),
seeing all this damage definitely has increased my incentive.

Same situation, hanging in the basement. If you do I will. :D
 
Same situation, hanging in the basement. If you do I will. :D

Need to order some parts to complete, counterweight, fairings, rod ends. Took it down from its shelf today and cleaned it up.
Gonna involve some paint fiberglass work as well so not really a small task, but I’m gonna do it!
I think the smaller rudder also looks better so that another plus.
I even brought home the RV8 plans to look up the P’N’s
 
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Need to order some parts to complete, counterweight, fairings, rod ends. Took it down from its shelf today and cleaned it up.
Gonna involve some paint fiberglass work as well so not really a small task, but I’m gonna do it!
I think the smaller rudder also looks better so that another plus.
I even brought home the RV8 plans to look up the P’N’s

We can not forget the rudder stops too. They revert to the original design. Ugh - more paint.
 
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Rudder sock

How about a big sock? Basically a bag that fits the VS and Rudder. Some bungies to hold it down. VS and Rudder become one unit. Less flopping back and forth.
 
Batons

How about a big sock? Basically a bag that fits the VS and Rudder. Some bungies to hold it down. VS and Rudder become one unit. Less flopping back and forth.

Unless you have batons on both sides, I think the sock will tend to push the ruder over hard left or right
 
However easy or difficult the removal of the rudder is in the field, it will pale to the difficulty of putting the rudder back on in the field.

I’m sure if we got all the Steve Ingra[ha]m’s together, it wouldn’t take too long :D
And yes, I _can_ imagine the stream of cuss words coming from you while putting it back on :p

I’m sure getting all those washers and what not in there is a pain, especially up in the air on the A model.

Didn’t you have moving blankets or cardboard and Saran Wrap around your wings also? Could you just do the same around the rudder/VS? Might be the best idea yet.
 
Saran wrap

I’m sure if we got all the Steve Ingra[ha]m’s together, it wouldn’t take too long :D
And yes, I _can_ imagine the stream of cuss words coming from you while putting it back on :p

I’m sure getting all those washers and what not in there is a pain, especially up in the air on the A model.

Didn’t you have moving blankets or cardboard and Saran Wrap around your wings also? Could you just do the same around the rudder/VS? Might be the best idea yet.

I like that idea. Keep precut sections of Coroplast in the plane. Buy a roll of saran wrap and go to town. When it's time, just snip it with scissors.
 
I’m sure if we got all the Steve Ingra[ha]m’s together, it wouldn’t take too long :D
And yes, I _can_ imagine the stream of cuss words coming from you while putting it back on :p

I’m sure getting all those washers and what not in there is a pain, especially up in the air on the A model.

Didn’t you have moving blankets or cardboard and Saran Wrap around your wings also? Could you just do the same around the rudder/VS? Might be the best idea yet.
Yes, perhaps that could be a good idea, but no, I did not have the moving blankets and saran wrap on my plane. The yellow 14A that I took pictures of did. However, he did not wrap the vertical surfaces. I am sure he wishes he had done so.
 
Unless you have batons on both sides, I think the sock will tend to push the ruder over hard left or right

A sock over the entire rudder/elevator with several pockets on each side to slide in battens should work. The sail on my windsurfer had flat fibre glass stiffeners that worked this way. The whole thing would pack away and be relatively easy to install.
 
A sock over the entire rudder/elevator with several pockets on each side to slide in battens should work. The sail on my windsurfer had flat fibre glass stiffeners that worked this way. The whole thing would pack away and be relatively easy to install.
:cool:
This is a great idea, in my humble opinion. Perhaps, the folks who make the prop sock could be convinced to make something like this.
 
Sock

How about a big sock? Basically a bag that fits the VS and Rudder. Some bungies to hold it down. VS and Rudder become one unit. Less flopping back and forth.

I was thinking three socks. One over VS/rudder. One each over HS/elevator. Each side zippers to the vertical sock. The HS bottoms are bungeed or zippered. Straps sewn into the fabric end in rings. Rings at the tail are clipped with a carabiner to hold it all together. Could be tied down as well.
My wife is a seamstress. I may have her throw something together. Made from something strong and light like the material for tents. Sheds water and breathes.
Something like this "rip stop" kite material.
Tong Gu 39 inch Kite Flag Tent Material Nylon Fabric Waterproof Ripstop Outdoor Camp Cover (Red, 59 x 78 inch) https://a.co/d/b30Gy32
 
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This might be difficult to implement so that it works in the very severe conditions where it's most needed. Wirejock's suggestions would help somewhat. I would not rely on this.

Dave
 
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