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  #21  
Old 11-18-2017, 02:45 PM
13brv3's Avatar
13brv3 13brv3 is offline
 
Join Date: Nov 2005
Location: Tellico Plains, TN
Posts: 566
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Marc,

As I mentioned earlier in the thread, the gear legs have some sort of wood stiffeners, but until I take the fairings off, I won't be able to see how they were constructed. Clearly they're not working, so I'll probably be reworking them, since the stiffeners fixed the problem with my previous RV-3B.

Cheers,
Rusty
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RV-8, SN-80587, built, flown, sold.
RV-3B, SN-10751, rotary engine, built, flown, sold
RV-8, SN-82470, built, flown, sold.
RV-3B, SN-11351, purchased, , flown, sold
A&P - 2018
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  #22  
Old 11-19-2017, 04:08 PM
heinz heinz is offline
 
Join Date: Sep 2010
Location: comox bc
Posts: 52
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Anyone with an RV3,4,6,7,9 tail dragger who has experienced wheel shimmy more than a couple of times need to carefully check the lower engine mount to airframe attach area. I guarantee you that these 3/8 bolts will be loose. I have seen them up to two full turns loose. The working back and forth at this attach area caused by the shimmy puts tremendous strain on these corner fittings and the bolt. Good luck.
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  #23  
Old 11-26-2017, 12:51 PM
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13brv3 13brv3 is offline
 
Join Date: Nov 2005
Location: Tellico Plains, TN
Posts: 566
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Greetings,

For further entertainment, I decided that I'll try to keep this thread updated as my testing progresses. It may take a while since the hanger is a looooooong way away, and it's winter.

The last time I was at the airport, I removed the fairings to see what sort of stiffeners exist. They're not exactly as specified, but at least they were in the ballpark. The most obvious problem is that one of them had come loose from the gear leg, and since the leg is tapered, it slides down, and becomes even more loose. I'll give you one guess which one that was

I cut the loose stiffener off, and besides coming loose, it was also coming apart, and the ends were somewhat water rotted. The other one appears to be pretty solid, though there is some hollow sound as I tap on the upper end. Since I could never stand to have the two not match, and since I figure that one has some water rot as well, I'm going to remove it on my next trip, and plan to replace them both.

I also brought the fairly well worn Condor tires home, and have a motorcycle wheel balancer on order. If the tires appear round, I will balance them as best I can, and then reinstall them. If they are not round, I'll order new tires. The Desser monster retreads seem to be well recommended.

The first step in my experiment will be to install known round and balanced wheels, but no stiffeners, fairings, or wheel pants for the next flight. I'll try to determine if there is shimmy, and if it's at a higher or lower speed. Sadly, I didn't note the GPS ground speed when it happened before, but I have a pretty good feel for it.

Following that test, I'll install the wheel pants for another test, then stiffeners, and finally fairings. I really don't think the gear leg fairings will have much effect, so I'll probably try to get it shimmy free before installing those.

Cheers,
Rusty
__________________
RV-8, SN-80587, built, flown, sold.
RV-3B, SN-10751, rotary engine, built, flown, sold
RV-8, SN-82470, built, flown, sold.
RV-3B, SN-11351, purchased, , flown, sold
A&P - 2018
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  #24  
Old 11-29-2017, 08:52 AM
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F1Boss F1Boss is offline
 
Join Date: Aug 2006
Location: Taylor Texas
Posts: 847
Default "The wood is no longer needed"

The Glasair folks ran into the same problem, but their thinking is not along the same lines as ours. They actually came up with a fix - using composites of course.

I have flown versions of the F1 and HR2 before and after this setup. HUGE difference.

If someone would show me how, I can add the PDF into this thread - or send it along for another smart guy to add it? Either way you all get the benefit.
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Mark

"Not everyone needs a Rocket. Some folks, however, shouldn't live life without one.
You know who you are."
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  #25  
Old 11-29-2017, 09:49 AM
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grubbat grubbat is offline
 
Join Date: May 2012
Location: Ga
Posts: 718
Default Thanks Mark

Mark,
Would really appreciate seeing the .pdf.
I've thought about other options besides pine / oak trim molding. One is milling alum blocks the shape of the airfoil and bolting on the gear somehow. Another idea is milling some polyurethane or some other dense non-biodegradeable material that would offer some form of damping properties.
Craig


Quote:
Originally Posted by F1Boss View Post
The Glasair folks ran into the same problem, but their thinking is not along the same lines as ours. They actually came up with a fix - using composites of course.

I have flown versions of the F1 and HR2 before and after this setup. HUGE difference.

If someone would show me how, I can add the PDF into this thread - or send it along for another smart guy to add it? Either way you all get the benefit.
__________________
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RV-3 Sold
RV-4 Sold
1968 Twin Comanche - Sold
RV-6a Sold
1965 Comanche 260 - Sold
RV-9 Built and Flying
600A Aerostar - Sold and regretted
2000 Maule MXT-7 Project
1965 Maule M4 Bushwacker projectů till RV-15 shows up
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  #26  
Old 11-29-2017, 09:49 AM
Boyd Birchler Boyd Birchler is offline
 
Join Date: Sep 2014
Location: IN
Posts: 254
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My plane (RV7) had no gear leg stiffeners. The gear would only occasionally shimmy.
The main reason for installing "Woodman's" stiffeners was to eliminate the little skipping and bouncing on landing;perfect landings were elusive. It is an entirely better landing plane with the stiffeners! PS : it never shimmy's now.
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  #27  
Old 11-29-2017, 10:41 AM
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13brv3 13brv3 is offline
 
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Location: Tellico Plains, TN
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Quote:
Originally Posted by F1Boss View Post
The Glasair folks ran into the same problem, but their thinking is not along the same lines as ours. They actually came up with a fix - using composites of course.

I have flown versions of the F1 and HR2 before and after this setup. HUGE difference.

If someone would show me how, I can add the PDF into this thread - or send it along for another smart guy to add it? Either way you all get the benefit.
I'm not sure I can upload it, but I'll try. Either way, I'd love to have a copy if you don't mind emailing it to me.

BTW, one of my tires was out of round, and about 2.5 oz out of balance. It wasn't the one that was doing the worst shimmy though. The other was better, but Desser Monster retreads inbound.

Thanks,
Rusty
13brv3@gmail.com
__________________
RV-8, SN-80587, built, flown, sold.
RV-3B, SN-10751, rotary engine, built, flown, sold
RV-8, SN-82470, built, flown, sold.
RV-3B, SN-11351, purchased, , flown, sold
A&P - 2018
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  #28  
Old 11-29-2017, 02:14 PM
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Special Delivery Special Delivery is offline
 
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Default Provided by F1Boss

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Students build the airplane." -Glen Salmon

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Last edited by Special Delivery : 11-29-2017 at 07:42 PM.
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  #29  
Old 11-29-2017, 03:54 PM
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13brv3 13brv3 is offline
 
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Location: Tellico Plains, TN
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Thanks for posting that. I wonder how many people have used that method? The shimmy seems somewhat different for everyone, and you can find people who say the wood dampers worked perfectly, and others who think they didn't do much good. I guess I'd want to see a fairly high rate of success before I wrap that much fiberglass on anything.

Rusty (I hate fiberglass)
__________________
RV-8, SN-80587, built, flown, sold.
RV-3B, SN-10751, rotary engine, built, flown, sold
RV-8, SN-82470, built, flown, sold.
RV-3B, SN-11351, purchased, , flown, sold
A&P - 2018
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  #30  
Old 11-29-2017, 04:33 PM
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Bob Martin Bob Martin is offline
 
Join Date: Jan 2005
Location: Charlottesville, Virginia
Posts: 1,277
Default Too Much

I like the fiberglass solution and not sure why I had never considered it.
But, the 6 layers on a round rod is 12 layers of cloth. Pretty sure 12 layers will not fit between the spring steel rod and the VANS gear leg.
Now, from what I understand from the internet, the Rocket leg fairings are larger inside so it may accomidate 12 layers.

FYI......I reinforced a set of Vans leg fairings with 2 layers of glass tape internally on each side (4 total) and installed the pine wood stiffeners per the instructions. The fairing would not fit over the legs. I had to remove the stifferners, because removing the 4 plys inside the fairings was impossible. That is why I am so interested in this thread and really liked the idea of glassing the leg.
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RV-6, 0-360 Hartzell C/S, Tip up, 1200+TT
James extended cowl/plenum, induction, -8VS and Rudder. TSFlightline hoses. Oregon Aero leather seats.
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