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03-18-2014, 08:27 PM
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Join Date: Mar 2010
Location: VanAire, Co
Posts: 25
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I also replaced the empenage on my RV4, with an 8 emp. due to the tornado at Sun&Fun. I used the 8 because I just didn't want to build another tail jig. I am very pleased with the 8 emp.
No loss in top speed. Seems more stable in cruise flight (195 to 200) and remains effective throughout the landing sequence.
I also went to an electric trim, cutting a pound from the mechanical system.
My tail wheel weight changed 2.3 pounds.
I also like the looks of the larger tail.
Great "WOW" factor.
Loyd Remus and I did the mod at about the same time. We are bith very pleased.
I will be at Sun&Fun, parked at the far West GA camping area.
Come on by and take a look at N85007.
Joel Sidell
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03-18-2014, 10:33 PM
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Join Date: Jun 2005
Location: SoCal
Posts: 2,452
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Quote:
Originally Posted by nkd4flyr
Axel, it is a mystery to me if the elevators you weighed were balanced how they can weigh the same. Both the 4 & 8 elevators that I have weighed, there is a noticeable difference in weight between the right & left elevators. I used a bathroom scale to weigh the elevators individually.
Loyd
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Those are my numbers from two uninstalled (and near balanced) tails. They were all individually put on the scale and rounded to the nearest .5 lbs.
Don't know what to tell you
I will pass. Had to put an 18 lb weight in front of my prop on my flying rv because weight and balance issues.
__________________
Axel
RV-4 fastback thread and Pics
VAF 2020 paid VAF 704
The information that I post is just that; information and my own personal experiences. You need to weight out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk.
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03-23-2014, 07:25 AM
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Join Date: Jul 2011
Location: Hampton, Ga (4A7)
Posts: 5
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Thanks A lot guys for all the great responses!! I was looking specifically for information on the total installed weight change, and had expected it to be in the 3-6# range. After reading a bit, I think I'm going to go with the 8 tail, in spite of the somewhat heavier tail. I know that building light is usually the best thing to do, But for me, I feel like if I can keep the total weight increase on the tw to less than 8lbs, I'll be fine. She is going to be swinging a big heavy engine and prop way out front after all. I'm going to weigh my existing tail surfaces, and compare them to the 8 tail. I will give everyone here a breakdown of my findings, as well as exactly how it impacts my tw weight when I get to weighing.
Thanks again everyone for the great input and info!!
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03-23-2014, 10:28 AM
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Join Date: Oct 2010
Location: Allentown PA
Posts: 254
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Quote:
Originally Posted by nkd4flyr
I did it and it worked great!
Seems every few years this topic comes up.
I converted to the RV-8 tail about 4 years ago. Net gain on the T/W 3#.
After seeing the post from Axel I decided to confirm what I remembered from the conversion. So I dug out of storage my old RV-4 tail (built in 1995) weighed in at 44#, .016 skins on control surfaces, zinc chromate primer - no paint.
The 8 tail weighed 50#, epoxy primer! elevators balanced! farings on.
I used one of the pads from the digital scales that we use to weigh airplanes. They round to the nearest #. I came up with a difference of 6#, 7# worst scenario.
My 4 is equipped with an O/360 & Hartzell CS.
A friend of mine converted the same time. His 4 has an IO 320 with wood prop. He likes the conversion.
The most significant difference is: much more stable flight. I don't need any more down trim with a backseat passenger. I do 3 point landings - the flare is more like the 8. No loss in top speed.
The advantage of the 8 tail is easy to build compared to the 4 & it's going to be straighter than the 4.
Axel, it is a mystery to me if the elevators you weighed were balanced how they can weigh the same. Both the 4 & 8 elevators that I have weighed, there is a noticeable difference in weight between the right & left elevators. I used a bathroom scale to weigh the elevators individually.
Would I do it again. Yes.
We have 2 RV-4's in the shop being built with RV-8 tails.
Loyd
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Good report sir, thanks for the info. Does the RV-8 tail section increase your RV-4 VNE from the normal RV-4, 182 KIAS to over 200 since the RV-8 has VNE over 200 KIAS?
Has your crosswind capability improved?
Are most guys buying a quick build RV-8 tail section for the job and are the RV-8 skins .020 like the newer 4's?
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03-23-2014, 10:29 AM
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Join Date: Oct 2010
Location: Allentown PA
Posts: 254
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Also, I've noticed the tail wag phenomenon mentioned earlier in my RV-4 and wonder if you ever experienced that in turbulent air and if that improved as well.
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03-29-2014, 04:52 PM
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Join Date: Aug 2008
Location: Tehachapi,CA
Posts: 131
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I am repairing a damaged -4. I bought a -8 tail that was already built and primed.
Here are the weights of the un-installed parts.
rudder - 8.2 lbs
V-stab 8.8
R-elev 7.6
L-elev 7.3 (no trim tab)
H-stab 18.0 (different scaled rounded to .5)
I studied the differences of the two before I bought the -8 tail.
The -8 V-stab is about 5.5 inches taller than the -4.
The main difference in weight comes from the counter-weights
-8 rudder has one, -4 does not
-8 elevator tips do not extend as far forward as the -4 from the hinge line so the -8 elevator weights are a little bigger.
Another interesting note. if you look at the whole series of RVs.
The 3,4 and 6 do not have a rudder counter weight, the rest do. I did some research and never found a good explanation why Van went to a counter-weighted rudder after the -6. I have not heard of any flutter problems with the 4 or the 6, so I have considered removing the counter weight on -8 rudder when I install it, then it would be like a -4 and 6 tail.
PS: I seem to remember a post where Smokey said he had a friend that had an -8 tail installed on a -4. Maybe he can chime in about how it flew. compared to all the stock -4s he has flown.
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03-29-2014, 07:39 PM
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Join Date: Jan 2005
Location: TX32
Posts: 1,891
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Counter Weight Culture...
Quote:
Originally Posted by tikicarver
PS: I seem to remember a post where Smokey said he had a friend that had an -8 tail installed on a -4. Maybe he can chime in about how it flew. compared to all the stock -4s he has flown.
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Tiki,
I helped a friend install an 8 tail on a 4 and it worked fine. However comma, as an RV4 builder/enthusiast it wasn't aesthetically pleasing IMHO, simply too big. I feel the same way about all the post RV6 RV's. My HR2 has a stock RV4 tail installed and I believe very pleasing lines and the rudder isn't counter-weighted. Even at the highest indicated airspeed I ever encountered (250 KIAS at Sea Level) It was never an issue. My current RVX is a stock RV6 fuselage with an RV4 tail modified to fit the aft fuselage. It is the best control balance of any RV I have flown yet.
My own opinions don't matter but I believe Van counter-weighted the later model RV's rudders as a liability issue. Since their VNE is posted higher than previous RV's it only makes sense that all tail surfaces being counter balanced gives them greater margins on paper. With the original RV8 prototype shedding a wing inflight with 2 fatalities, I'm sure flutter of any type is a concern, whether realistic or not.
My good friend Hollywood built a counter-balanced rudder for his RV4 retaining the same size vertical fin. It required a bit of cutting and engineering but looks great and works well.
Personally, I like the stock tail...
V/R
Smokey
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03-30-2014, 08:49 AM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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Quote:
Originally Posted by smokyray
...Personally, I like the stock tail...
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I'm with you on that.
I have an -8 tail on my Rocket and am considering going back to a -4 vertical or cutting down the existing unit. I will retain the counterbalance however.
Some people have claimed no speed loss with the -8 tail, but I suspect that's at RV speeds, not Rocket speeds. I know of a Rocket that lost a good chunk of speed with the move to a -8 tail.
...and yes, the short tail looks much better.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
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Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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03-30-2014, 01:21 PM
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Join Date: Aug 2008
Location: Tehachapi,CA
Posts: 131
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I guess what you guys are saying,
When it comes to tails....bigger is not better :-)
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