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  #21  
Old 08-04-2022, 07:20 AM
BillL's Avatar
BillL BillL is offline
 
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Location: Central IL
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Default Does this happen every year or just even years?

Steve Melton (now anonymous) offers a printed set of gust locks that holds the TE and anchors to the elevator locks with ropes employing a short shock cord.

Did anyone have one of these (or similar) at OSH?

The engineer in me wonders about the structure of the 7/9 rudder constrained in this manner to withstand a 90 ft-lb torque (basically 90 lb side force) to survive the event. But it is better than all the rest, structurally IMO.
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  #22  
Old 08-04-2022, 07:32 AM
thinkn9a thinkn9a is offline
 
Join Date: Nov 2007
Location: Mississippi
Posts: 327
Default belt, suspenders, block, bolts, pin,.. for gust lock

I wasn't there, but have worried about how I set the ultimate gust lock and what happens with extended period of gusts, so I ended up with the following.

- added a pin to hold slip down collar device in place at the "joint" (noticed it wanted to work loose)
- have a "belt" of nylon strap with velcro on both ends to hold rudder pedals in gust lock
- "block" of wood, (not optimized) that the gust lock shaft passes through, to minimize the aileron movement allowed
- bolts holding the block of wood in place, that attach through an aluminum plate, which is held by using existing screws for floor (there is a piece of plywood screwed/glued on to the bottom of the block of wood, that provides a foot for the bolts to go through)

made me feel better when leaving the plane for several days on a western trip,... but now wondering about what level of gusts the rudder will handle.

Maybe a "heavy weather" lock/block in addition at top of rudder would spread the loads out enough??? or does it require something on trailing edge
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  #23  
Old 08-04-2022, 08:08 AM
rocketman1988 rocketman1988 is offline
 
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Location: Sunman, IN
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Default

Quote:
Originally Posted by BillL View Post
Steve Melton (now anonymous) offers a printed set of gust locks that holds the TE and anchors to the elevator locks with ropes employing a short shock cord.

Did anyone have one of these (or similar) at OSH?

The engineer in me wonders about the structure of the 7/9 rudder constrained in this manner to withstand a 90 ft-lb torque (basically 90 lb side force) to survive the event. But it is better than all the rest, structurally IMO.
It would be interesting to see some actual data... In your example, a 90 lb side force spread over a relatively small area of the trailing edge of the rudder. Even if the TE was able to support that kind of load, what about the rest of the structure? It would seem that many of the damaged rudders have similar failures so an analysis of the loading required to do that damage would provide a good insight on a good way to prevent it...
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  #24  
Old 08-04-2022, 08:09 AM
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rv8ch rv8ch is offline
 
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Default gust lock

I've got the anti-splat, and it seems to hold well, but to be sure, the only way is to have multiple gust locks like this on each control surface:

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No matter how tight you install something holding the rudder pedals or stick, there will be some play, and a lot of force. I'd be curious to know if Van's has an opinion on the best way to keep the control surfaces from banging to their stops.
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  #25  
Old 08-04-2022, 08:20 AM
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Quote:
Originally Posted by rockwoodrv9 View Post
The question I have is if you stood there during the wind and physically held the bottom of the rudder in place, could the rudder be bent over anyway?
In my opinion, yes. And we saw twisted and or broken examples which were fixated at the top, at the balance mass arm, as well as at the bottom, at the stops or rudder pedals.

Quote:
Originally Posted by dpansier View Post
Many years have passed since I did cantilever beam calculations but by moving the support from one end of the rudder to the center point would decrease the deflection by 1/2 or more at the end points.

The photo showing the duct tape passing behind the half way point on the rudder out to the ends of the horizontal stabilizer may have been the best solution had it been on before the storm hit.
Agree, although I'd substitute a rope and trailing edge fitting for duct tape. External fixation at the vertical center of rudder area will work at wind levels way beyond the limits of fixation at the top or bottom. The yellow -14A rudder Steve posted is a perfect example....fixed at the bottom via the rudder pedals, but hit with a gust which exceeded the torsional capacity of the rudder.

The smaller -8 rudders held up better...less area, and I suspect torsionally stronger due to the folded trailing edge.
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  #26  
Old 08-04-2022, 08:47 AM
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Quote:
Originally Posted by Ironflight View Post
All our RV’s (two of which were at the show this year) are taildraggers, and we let the tailwheel locking pin hold the rudder. We generally use seat belts for the elevator/aileron. In twenty oshkosh’s and as many years flying them all over the country, those measures have always worked for us.

Of course YMMV!

Paul
Excuse my ignorance. Could you explain the tailwheel locking pin and how it holds the rudder?
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  #27  
Old 08-04-2022, 08:59 AM
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Ironflight Ironflight is offline
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Quote:
Originally Posted by mfleming View Post
Excuse my ignorance. Could you explain the tailwheel locking pin and how it holds the rudder?
So long as the rudder is within about 25 degrees of center, the tailwheel is locked to the rudder (for steering). So if you have you’re tailwheel straight on the ground, the rudder will be locked to it, and since the weight of the aircraft is on the tailwheel, in the grass it is a great rudder lock.

Structurally, this is similar to a locking pin or fixture at the bottom of the rudder on a nosewheel RV - so the real question is if you could still get the “twisting” failure that some of the nosewheel airplanes experienced - or if not, why not?

Did ANY taildragger RV’s suffer rudder damage in Saturday’s wind storm?

Paul
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  #28  
Old 08-04-2022, 09:04 AM
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mburch mburch is offline
 
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Quote:
Originally Posted by Ironflight View Post
All our RV’s (two of which were at the show this year) are taildraggers, and we let the tailwheel locking pin hold the rudder. We generally use seat belts for the elevator/aileron. In twenty oshkosh’s and as many years flying them all over the country, those measures have always worked for us.
Paul, I think I know the answer, but I'll ask in the interest of clarity and data: All the rudders in question have been the folded-trailing-edge variety, correct?
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  #29  
Old 08-04-2022, 09:17 AM
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Quote:
Originally Posted by mfleming View Post
Excuse my ignorance. Could you explain the tailwheel locking pin and how it holds the rudder?
Knee bone connected to the leg bone....

If the tailwheel is tied down and centered, the pin is extended into the notch in the steering arm, which is coupled to the rudder by a link or chains. Thus, the key is keeping the tailwheel firmly tied down in the dirt. That, BTW, means driving the tail tiedown very close to the wheel.

Tailwheel mechanics:

https://www.danhorton.net/Articles/1...lTuneUp.pd.pdf
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  #30  
Old 08-04-2022, 09:23 AM
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Quote:
Originally Posted by BillL View Post
Steve Melton (now anonymous) offers a printed set of gust locks that holds the TE and anchors to the elevator locks with ropes employing a short shock cord.

Did anyone have one of these (or similar) at OSH?

The engineer in me wonders about the structure of the 7/9 rudder constrained in this manner to withstand a 90 ft-lb torque (basically 90 lb side force) to survive the event. But it is better than all the rest, structurally IMO.
I use a home-made version similar to Steve's design. It held perfectly with no issues or damage. I don't have a picture of my set-up though.
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