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  #1  
Old 12-31-2021, 12:52 PM
Cloudboy Cloudboy is offline
 
Join Date: Dec 2021
Location: Deer Park, Washington on WT-21
Posts: 46
Default Twitchy handling on rollout

I built an RV-8 several years ago. It was hard to handle on rollout until I put an angle shim on the landing gear. I used advice from an article Budd Davidson wrote years ago where he explained that toe out is better than toe in and straight ahead is best. It worked for me and the 8 handles well now.
I recently decided I needed an RV-3. The wait time for a kit is 18 months and I'm too old to wait that long. I just bought a flying RV-3. Now I am back where I was initially with the 8. Too squirrelly on roll out. I checked the alignment and I have toe in. I would like to straighten the alignment and wonder if any one has found a way to change the alignment short of installing new gear legs?
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  #2  
Old 12-31-2021, 01:07 PM
jrs14855 jrs14855 is offline
 
Join Date: Apr 2008
Location: Lake Havasu City AZ
Posts: 2,943
Default Alignment

Steve Wittman, designer of the round spring gear, called for 1/16" toe in measured in the length of the axles. No information on weight or angle of fuselage to ground when doing this.
Do you have camber? Specified camber from Wittman plans is 3/8" in length of gear.
The reality with the round gear is that the proper alignment only occurs for one gross weight and one fuselage angle.
A tailwheel link with a spring cartridge may help you.
Changing the gear alignment on the round gear is a major job.
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  #3  
Old 12-31-2021, 01:32 PM
Cloudboy Cloudboy is offline
 
Join Date: Dec 2021
Location: Deer Park, Washington on WT-21
Posts: 46
Default

I agree it looks like a major effort. New gear legs are back ordered and maybe I'll have to live with a little toe in. With my other plane toe out worked better. I have a single tailwheel control arm with single spring cartridge link. I think I will change back to the original with some slack in the chains. Years ago I talked to Ken at Vans and he suggested slack in the tail wheel chains to help prevent overcontrolling. It worked for me. I wish they still had the taillynx available.
Thanks for confirming what I was afraid of regarding adjustment.
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  #4  
Old 12-31-2021, 03:39 PM
RWoodard's Avatar
RWoodard RWoodard is offline
 
Join Date: Jan 2005
Location: Brighton, Colorado
Posts: 504
Default

From those with actual, significant experience in multiple RV types, is it possible that the RV-3 is just a little more sensitive on the ground than the RV-8? I've flown everything but the 10 and the 14 and I can say with certainty that the -3 is much more sensitive in the air than the other models. I can't say, however, that I've got a bunch of experience going back and forth between the models with enough landings to give a qualified opinion of any differences in ground handling.

Anecdotally, I let a friend fly my RV-3 not long after I bought it. He finished his RV-8 back in the 90's and has been flying it ever since. He took one flight in my RV-3 and said he didn't want any more of it. Admittedly, he was 77 years old at the time and said he was too old to make friends with a new plane, but he's been flying tailwheel planes since he was 15 years old in 1956.

I owned my Midget Mustang for about 6 months after buying my RV-3 and can say that the RV-3 was a much more docile, honest ground handling aircraft than the Midget Mustang could ever hope to be! I've never had a reason to measure or even question the alignment of my RV-3 because ground handling always seemed great to me!
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Brighton, Colorado (CO12)
RV-3 IO-320
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  #5  
Old 12-31-2021, 03:55 PM
Larry DeCamp Larry DeCamp is offline
 
Join Date: Apr 2010
Location: Clinton, Indiana
Posts: 1,291
Default -3 ground handling

FWIW, I am just a PP with over 1100 hours TW. Champ, Luscombe, Rose Parrakeet (very light with tail skid ), RV 3B w/ 250 hr. The 3 even had the Flyboy accessories geometry tail wheel. I always found it sensitive to the extent I did not use much power for takeoff until the rudder had significant authority. IE, a lot of tap dancing . That said, I can’t imagine anything sweeter in the air ��
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RV3B sold
RV-4 fastback in process w/ Superior roller 360/AFP/G3X/CPI/Catto3b
Clinton, IN
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  #6  
Old 12-31-2021, 04:07 PM
calpilot calpilot is offline
 
Join Date: Aug 2018
Location: Independence
Posts: 231
Default

3's and 4's are more twitchy than 7's and 8's. Especially with a steering link instead of chains.
That being said, My second RV-7 had a very bad shimmy that I tried everything to fix. The right gear was toed out 1/4 degree, and the left was toed in 1/2 degree. There is some variation in the "Heat and bend" from Lance, the supplier. I spent $600 on a new set of gear, and there is only a very slight shimmy right at 23 mph in the left gear, vast improvement. However.... many of the 3's required the builder to align the gear before drilling, so there is some variance!
Best of luck!

DAR Gary
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  #7  
Old 12-31-2021, 04:32 PM
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Mel Mel is online now
 
Join Date: Mar 2005
Location: Dallas area
Posts: 11,643
Default Tailwheel aircraft.............

As has been said, "0" toe is best. Toe-out is better than toe-in. Think of it this way, if the airplane starts to veer to the left, more weight is transferred to the right wheel. If it is toed-in, that wheel will take you even more to the left. If it is toed-out, it will tend to pull the airplane back to the right. ref: "Landing Gear Design for Light Aircraft" by Ladislao Pazmany.

If you will notice Van recommends "0" toe with the airplane off the ground. With the Wittman style landing gear, by design, any weight on the gear causes a small amount of toe-out.

When I designed the conventional gear for the Moni Motor-glider back in the 1980s, I discovered quickly that any amount of toe-in makes the airplane quite squirrelly on the ground. Once I added a minute amount of toe-out, the airplane became a pussy- cat.
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EAA Flight Advisor/Tech Counselor, Friend of the RV-1, Lifetime EAA.
Recipient of EAA Tony Bingelis Award and Wright Brothers Master Pilot Award
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<rvmel(at)icloud.com>

Last edited by Mel : 01-01-2022 at 12:54 PM.
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  #8  
Old 12-31-2021, 04:50 PM
sf3543 sf3543 is offline
 
Join Date: Jan 2005
Location: San Antonio, TX
Posts: 1,123
Default

Things I have noticed about my RV3 compared to other RVs, and I have flown all the tail dragger variations except the -14.
For me, my RV6 was the best landing plane followed closely by the RV7. The RV3 is a little harder to land well.
My RV3 is easy to land consistently, once you get the hang of it. Being a smaller airplane can make it a little twitchy, especially if you tend to over control.
Some things that might make your RV3 less twitchy would be:
-Install VANs regular springs or the Tail Lynx with the chains/cable not quite taut. I do not care for the single arm tailwheel springs. To me they are too touchy, and I have seen several of them break.
-VANs standard tailwheel assembly is a little more stable than the angled assemblies available. Even though it has less clearance at the front of the socket. I have never had any issues with VANs standard offering or the angled variety, but just saying.
-Less air in the mains (Don't know what you are running now but 28 to 32 psi is what I like to run on the 3.)
-You might work on your landings so you make slower touch down speeds. I see a lot of RV guys come blasting in faster than they need to.
-I don't do full on wheel landings in the RVs much but prefer tail low wheel landings, almost a 3 pointer. My RV3 does really good 3 pointers so I do a lot of them. Probably a little easier to control, in my opinion, if the plane is touchy.
-Let the plane roll out a ways before you use the brakes unless you are doing a short field landing. Saves on the brakes and is easier not to over control.

These are just my observations, YMMV.
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Last edited by sf3543 : 12-31-2021 at 05:59 PM.
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  #9  
Old 12-31-2021, 07:18 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 3,363
Default

I agree on all counts!

I am really happy with my Tail Lynx.


Quote:
Originally Posted by sf3543 View Post
Things I have noticed about my RV3 compared to other RVs, and I have flown all the tail dragger variations except the -14.
For me, my RV6 was the best landing plane followed closely by the RV7. The RV3 is a little harder to land well.
My RV3 is easy to land consistently, once you get the hang of it. Being a smaller airplane can make it a little twitchy, especially if you tend to over control.
Some things that might make your RV3 less twitchy would be:
-Install VANs regular springs or the Tail Lynx with the chains/cable not quite taut. I do not care for the single arm tailwheel springs. To me they are too touchy, and I have seen several of them break.
-VANs standard tailwheel assembly is a little more stable than the angled assemblies available. Even though it has less clearance at the front of the socket. I have never had any issues with VANs standard offering or the angled variety, but just saying.
-Less air in the mains (Don't know what you are running now but 28 to 32 psi is what I like to run on the 3.)
-You might work on your landings so you make slower touch down speeds. I see a lot of RV guys come blasting in faster than they need to.
-I don't do full on wheel landings in the RVs much but prefer tail low wheel landings, almost a 3 pointer. My RV3 does really good 3 pointers so I do a lot of them. Probably a little easier to control, in my opinion, if the plane is touchy.
-Let the plane roll out a ways before you use the brakes unless you are doing a short field landing. Saves on the brakes and is easier not to over control.

These are just my observations, YMMV.
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Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
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Hobbs 725
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  #10  
Old 01-01-2022, 10:49 AM
Cloudboy Cloudboy is offline
 
Join Date: Dec 2021
Location: Deer Park, Washington on WT-21
Posts: 46
Default

Mel, Steve and Steve. Thanks for the replies. It is good to have conformation on what I've been thinking. So many people advocate toe in that I've felt like a flat earth believer. My 3 acts just like you would expect with toe in. Once it starts to the left, the right wheel is weighted, pushing the plane harder left. Then I overcontrol and it's Mr. Toad's wild ride. Toe out tends to self correct. That being said, the toe in is only .9 degree and it is hard to blame that for all my problems. I measured the toe with the wheels on the ground but no weight in the plane. I had even drained the fuel to update the weight and balance. I should probably have checked it with some fuel and me in the plane.
I also agree with slack in the control chains. Years ago Ken at Van's explained that on roll out when you are still moving fast, air over the rudder gives you plenty of control so a tight tail wheel gives you too much. Some slack helps that. I'm in the process of going back to lose chains.
Ken also suggested lower tire pressure. I'm down to 26 psi. If I go much lower, it will be too hard to push around.
That leaves landing speed. I'm probably landing too fast and I'll work on slower. I usually wheel land because it works so well in the 8. I've been carrying a little power on short final to keep a really minimal decent rate and avoid bouncing. I also use two notches of flaps to keep the nose down and improve visibility. Maybe I can lower decent rate using one notch of flaps instead of power to keep decent rate low. I fly final about 80 mph. What do you guys suggest.
I always tend to blame myself for problems like this and just attribute it to inadequate skill. But, I've had Stearmans, a Pitts S2S and a Cessna 140 with misaligned gear on one side. The Cessna was twitchy and unpredictable in which direction it would dart on landing. The 3 is by far the worst so I don't think it is just me.
Mel, thanks for the help with amending my operating limitations. I discussed the change with my PMI and we are on the same page now. Unfortunately, there is now an online form to fill out to apply for an airworthiness certificate. You probably knew that. There are 271 pages of instructions for what used to be the one page paper form now that it is online. After a couple hours I realized that I can't apply until Okla City gets the plane transferred to my name. That will probably take a few months given the backlog. It's too cold with too much snow on the runway for aerobatics anyway.
Happy New Year, Blue Skies and Tail Winds of 2022.
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