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11-17-2011, 09:51 AM
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Join Date: Aug 2005
Location: Virginia Beach, VA
Posts: 474
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Also, any opinions on using carbon fiber instead of glass?
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Tim Ribble
Virginia Beach
RV-6A (only took 13 years to build  )
N621TR In unrestricted operation
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11-17-2011, 10:10 AM
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Join Date: Mar 2007
Location: Sonoma County
Posts: 3,821
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Quote:
Originally Posted by trib
After operating for almost 2 years, I've come up with a gear leg shimmy, which occurs on both main and nose gear legs.
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If you have gone 2 years without a shimmy, why do you think you need stiffeners?
My 6A had a nose shimmy. I adjusted the nut as instructed...... Gone. My right main had a shimmy Cleveland wheels with felt dust seals. I installed GoodYear flight special II's and ALL shimmy is gone. Tire pressure goes from 40# down to about 20# before I catch it. No shimmy at any pressure. I can tell when the tires need air because it's harder to pull out of the hangar. I also have one leg that was under bent at the factory and has less camber and that has not effected the quality of my landings.
If you had the shimmy from the start and used good tires and good control on your bearing and seal drag...... then I would say add the wood brace. But I don't think that you need it Yet.
Last edited by gasman : 11-17-2011 at 09:09 PM.
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11-17-2011, 01:24 PM
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Join Date: Oct 2007
Location: Sacramento, CA
Posts: 3,351
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Quote:
Originally Posted by trib
Also, any opinions on using carbon fiber instead of glass?
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I would think CF is not as desirable since it is much stiffer then fiberglass and might not help with the flexibility that it needs. Also, since it acts as a dissimilar metal, in case your powder coat rubs off, there is a greater chance for corrosion.
I was actually thinking of if it can be wrapped with a webbing so if it ever needs removal (either for inspection or other reasons) it can be done much easier?
__________________
Mehrdad
N825SM RV7A - IO360M1B - SOLD
N825MS RV14A - IO390 - Flying
Dues paid
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11-18-2011, 10:04 AM
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Join Date: Aug 2005
Location: Virginia Beach, VA
Posts: 474
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I understand the carbon fiber is much stiffer, I'm not sure about the acting as a dissimilar metal. My understanding is that carbon is about the most inert material there is. Galvanic corrosion between dissimilar metals doesn't seem to be applicable, in that plain carbon fiber is not a metal and would not corrode or induce corrosion. Am I missing something here? THe stiffness and durability were the issues I was hoping to find out about. Primarily is anyone has used carbon fiber in this application as I think it is so much stronger (and way cooler looking  ). If there isn't anyone who has any experience using it here, then I'll just stick with the glass wrap. I'm always interested in the learning experience, so if you have knowledge of the corrosion potential here I'm glad to hear it.
Gasman, as far as needing the stiffeners, I can get by without them, but I'm not happy with the near margin to the shimmy and want to install these to increase it. It's only a little of my time and pretty inexpensive, so I am choosing to do this. I can't think of any negative repercussions, other than I might miss a couple of hours of flight time during the installation. It may just be to satisfy my need to tinker.
As always- I appreciate the feedback here. DR, I'm a little late in sending in my funds this year, but will get to it as this is the best bang for the buck I know of!
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Tim Ribble
Virginia Beach
RV-6A (only took 13 years to build  )
N621TR In unrestricted operation
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11-18-2011, 01:34 PM
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Join Date: Apr 2005
Location: KSLC
Posts: 4,021
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I know two builders, that wrapped the nose leg with carbon fiber. One has been flying for 3 1/2 years with no problem. The other, is about a year.
L.Adamson
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11-18-2011, 02:00 PM
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Join Date: Nov 2007
Location: Keller, TX
Posts: 151
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Quote:
Originally Posted by trib
I understand the carbon fiber is much stiffer, I'm not sure about the acting as a dissimilar metal. My understanding is that carbon is about the most inert material there is. Galvanic corrosion between dissimilar metals doesn't seem to be applicable, in that plain carbon fiber is not a metal and would not corrode or induce corrosion.
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I don't know the chemistery, but the earlier Bombardier Challenger aircraft screwed carbon flooroards directly to the milled aluminum floor beams. A little moisture from rain, galley spills, or cleaning the carpets is all to took. Many of the repairs went well into the hundreds of thousands with weeks of downtime. The fix was to epoxy paint the new beams and install a rubber gasket so they didn't touch each other. If you think about it - What are carbon/zinc batteries full of?
Many newer corporate aircraft have carbon boards to save weight, but have some method to keep them from touching. I have even seen ones with a layer of fiberglass or other fabric such as kevlar bonded to the surface that contacts the aluminum.
One aircraft I am familiar with came out with carbon engine pylon boards held down with $8 each titanium screws to save weight. After drilling out all the corroded ones the change was made to steel. (CRES if memory serves). Solved the problem.
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11-18-2011, 02:19 PM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,147
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Chemically, carbon (and carbon fiber) behaves as a metal and when in direct contact with another metal (and moisture) will result in galvanic corrosion. If you wrap the gear leg with it and you ever break through the powder coat so they can be in direct contact, you will have corrosion.
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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11-18-2011, 02:31 PM
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Join Date: Apr 2005
Location: KSLC
Posts: 4,021
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Quote:
Originally Posted by airguy
Chemically, carbon (and carbon fiber) behaves as a metal and when in direct contact with another metal (and moisture) will result in galvanic corrosion. If you wrap the gear leg with it and you ever break through the powder coat so they can be in direct contact, you will have corrosion.
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And, it will depend on moisture, and possibly other factors. Dissimilar metals. corrode at different rates, according to the conditions. For instance,...... copper, aluminum, and galvanized sheet metal, don't usually do well, when in contact with each other. But when pressed together with force, such as in air conditioning coils; they can last for many years, with minimal corrosion.
L.Adamson
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11-18-2011, 02:55 PM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,147
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Quote:
Originally Posted by L.Adamson
But when pressed together with force, such as in air conditioning coils; they can last for many years, with minimal corrosion.
L.Adamson
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If you can have them in contact with each other with no air gap for liquids (electrolyte) to penetrate, then you can't form a cell. Without a galvanic cell you can't have corrosion. The cell requires electrical contact between two dissimilar metals, plus an electrolyte in contact with both metals. Break the electrical contact, or remove the electrolyte, and you've broken the cell.
[/THREAD DRIFT]
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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