RV-4 Counterbalanced Rudder - again

[tunaf15]

Hello All,

Time to re-skin my rudder for rivet cracks. In the category of "doing way more than required for an otherwise simple repair" I have researched the option of converting to a counterbalanced rudder for an RV-4. Previous threads pointed to Dave Anders RV-4 as having one. It sounds like he built it but I can find no details on how other than one quick reference to a riveted trailing edge. Smoky posted something a long time ago about his buddy Hollywood having one on an RV-4, but no construction details there either. And other references herein for this topic are for RV-8 tails on an RV-4.

I'm aware of the need to keep tail weight to a minimum for CG considerations. So I'd prefer not to put an RV-8 tail on. I'd much rather keep to the overall dimensions of the RV-4 vertical empennage.

Also, doing anything that would reduce the probability of flutter and potentially increase Vne (to an RV-8 value or even better a Dave Anders CAFE value) seems like a great benefit! Along these lines, going from .016 skins to .020 skins to (possibly) assist in flutter reduction seems prudent.

Would anyone with first hand knowledge of building, modifying, or having details of a counterbalanced RV-4 rudder please chime in.

Thanks,
Tuna--

 

[TXRV-4]

Rudder counter balance

Order 0.20 skin for the rudder, that will help with the cracking, and build it to plans, but add RTV in the trailing edge at the stiffner junctions, the RV-4 rudder never had a counter balance, and I have never experienced rudder flutter to date at 720 hrs. I fly at cruise with my feet stretched to the firewall under the pedals for comfort, no tension on the cables, with no flutter problems. Make it easy, builds to plans, the 4 is enough work without being prepunched. My 2cents.
Shawn Scott
RV-4 Bounty Hunter III
A&P

 

[tunaf15]

Thanks Shawn. It's a continual back and forth over original or "improved" (?) rebuilding. I feel strongly both ways. Mike--

 

[007]

Mike;
Several of us in CO have placed the entire RV8 emp on our RV4's. One is a 360 constant speed, and mine is an IO 320 fixed. We are both very pleased with the operation of the ship.
I changed mine because of damage at S&F 2011. The other was changed because "I wanted to". The weight is minimal. The "WOW factor" is great.

 

[Michael White]

Tuna,
Talk to Jay Pratt at RV Central. He modified a 4 vertical fin and rudder to incorporate an RV-8 counterbalance (NOT the entire RV-8 fin and rudder, just the counterbalance). This sounds more like what you were looking for in your original post.

Regards,

 

[SportAvServ]

8 Tail

Mike;
Several of us in CO have placed the entire RV8 emp on our RV4's. One is a 360 constant speed, and mine is an IO 320 fixed. We are both very pleased with the operation of the ship.
I changed mine because of damage at S&F 2011. The other was changed because "I wanted to". The weight is minimal. The "WOW factor" is great.

What WOW? how did it benefit the performance handling or looks? What was wrong with the 4 original tail? Just need input.

RT

 

[sailvi767]

I will attach a photo of the rudder on my RV6. The aircraft was built by Robbie Attaway and has a balanced rudder. It is a small tailed six. I believe it is similar to Dave Anders. You can visit his website for contact info at Attawayair.com. He may be able to help you with the design.

George

 

[F1R]

I am with post#2. Check with John Harmon or at least look at his website and data for the HR III emp. I have not seen or heard of a problem.

 

[tunaf15]

Joel, Thanks for the input. I'm keeping the RV8 option on the back burner for now.

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Moose, Thanks. Wilco. Tuna--

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George, Thanks. That does indeed look like Dave Anders tail. I appreciate the info. Mike--

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F1R, Good point. I need to see if the overall dimensions of the HRII tail are the same as the 4. Tuna---

 

[PropMan]

I have purchased plans from John Harmon for the HR2 and HR3. Started on the 3 and was worried about the rudder, so I call and spoke with John. He told me he had engineers from NASA analize it and it's good to 400mph. The only difference in the HR3 emp is .020 skins. The HR3 has a Vne of 310mph, and I believe has been tested above that.

My .02- It's worth what you paid

 

[Michael White]

F1R, Good point. I need to see if the overall dimensions of the HRII tail are the same as the 4. Tuna---

Tuna,
Comparing John Harmon's HR2 plans and the RV-4 preview plans (I have both), the HR2 and RV4 horizontal and vertical tails are dimensionally the same.

Regards,

 

[007]

What WOW? how did it benefit the performance handling or looks? What was wrong with the 4 original tail? Just need input.

RT

WOW! As in Gee Wiz! The comments made by people looking at the ship.
I think it looks great. I call it an RV4.8 ER. (AUX FUEL)
Performance,ie speed, is un-changed.
I used the '8 emp because it is pre punched and WILL be straight.
Plus I did not want to build a new jig.
The '4 emp looked like a golf ball, from S&F hail.
The elevator seems to have greater authority at low speed. ie flair.

I would not have changed the emp, had it not been damaged.

Joel