VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.


Go Back   VAF Forums > Main > Safety
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #11  
Old 08-05-2022, 09:49 AM
Mike S's Avatar
Mike S Mike S is offline
Senior Curmudgeon
 
Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 16,497
Default

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.
__________________
Mike Starkey
VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
Reply With Quote
  #12  
Old 08-05-2022, 10:05 AM
Paul 5r4 Paul 5r4 is offline
 
Join Date: Oct 2006
Location: Foley, Al
Posts: 692
Default

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.
__________________
Paul Gray
Foley, Alabama
N729PG..... 500+ hrs
RV 7A, Lycoming 0 320 D1A, Sensenich FP propeller
pilotforfun2001@yahoo.com
VAF supporter $$$

Last edited by Paul 5r4 : 08-05-2022 at 10:18 AM.
Reply With Quote
  #13  
Old 08-05-2022, 10:21 AM
Untainted123's Avatar
Untainted123 Untainted123 is offline
 
Join Date: Jan 2021
Location: Azle, TX
Posts: 174
Default

Quote:
Originally Posted by swjohnsey View Post
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.

Quote:
Originally Posted by Tooch View Post
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.
Reply With Quote
  #14  
Old 08-05-2022, 10:30 AM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 3,118
Default

Quote:
Originally Posted by Paul 5r4 View Post
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...
__________________
Bob
EAA Tech Counselor
Aerospace Engineer '88

RV-10-ER
N464RL
Going to Paint at Evoke!
Garmin G3X-T, Barrett EFII S32, CAI, MTV-9B

Dues+ Paid 2021,...Thanks DR+
Reply With Quote
  #15  
Old 08-05-2022, 10:37 AM
MED MED is offline
 
Join Date: Jul 2015
Location: Aiken, SC
Posts: 945
Default

Quote:
Originally Posted by Webb View Post
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?
__________________
MED
140236
N435MD
Miss March 2020
Reply With Quote
  #16  
Old 08-05-2022, 11:39 AM
agent4573 agent4573 is offline
 
Join Date: Aug 2019
Location: Mountain view
Posts: 560
Default

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.
__________________
www.rv7build.com - out of date, will be updated soon
N69ER - built and flying - 2022 Bronze Lindy

Last edited by agent4573 : 08-05-2022 at 11:44 AM.
Reply With Quote
  #17  
Old 08-06-2022, 09:18 AM
Snowflake's Avatar
Snowflake Snowflake is offline
 
Join Date: Oct 2009
Location: Sidney, BC, Canada
Posts: 4,332
Default

Quote:
Originally Posted by Mike S View Post
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.
__________________
Rob Prior
1996 RV-6 "Tweety" C-FRBP (formerly N196RV)
Reply With Quote
  #18  
Old 08-06-2022, 09:58 AM
BillL's Avatar
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 6,733
Default

Quote:
Originally Posted by agent4573 View Post
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
__________________
Bill
RV-7
Reply With Quote
  #19  
Old 08-06-2022, 12:34 PM
Blw2 Blw2 is offline
 
Join Date: Apr 2022
Location: Saint Johns, FL
Posts: 39
Default

Quote:
Originally Posted by agent4573 View Post
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?
Reply With Quote
  #20  
Old 08-06-2022, 12:56 PM
Walt's Avatar
Walt Walt is online now
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,794
Default

Quote:
Originally Posted by BillL View Post
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.
__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags, MTV-9 prop
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 08-06-2022 at 01:20 PM.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 10:12 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.