Author Topic: Varieze Rudder trim  (Read 11127 times)

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Offline av-mech

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Varieze Rudder trim
« on: July 06, 2011, 07:33:30 AM »
Man o man, do I seem to chase that left rudder trim around.  I have the old sawtooth rudder trim and it seems that one tooth is to much either way.  My vari requires a lot of left rudder trim on climb out, a different setting in cruise and different again on decent.  Not unusal on the surface but it seems like I'm using a lot of trim on the rudder.  Any thoughts from you high time fliers???

Also, when braking at slower speeds I sometimes get some shimmy in the main gear legs.  If I let go of the brakes it stops.  Seems to happen at slow speeds, anybody else have this phenomonon?
Arnold Holmes
N80SH
IA 2712249
EAA 519850
TC#4476
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Offline Rick Hall

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Re: Varieze Rudder trim
« Reply #1 on: July 09, 2011, 09:45:23 PM »
Man o man, do I seem to chase that left rudder trim around.  I have the old sawtooth rudder trim and it seems that one tooth is to much either way.  My vari requires a lot of left rudder trim on climb out, a different setting in cruise and different again on decent.  Not unusal on the surface but it seems like I'm using a lot of trim on the rudder.  Any thoughts from you high time fliers???
Not a hi time flyer, or flyer for that matter, but what say the engine isn't pushing along the centerline. Say it was canted a degree to the left or right. Your trim setting would depend on speed and thrust.
Quote
Also, when braking at slower speeds I sometimes get some shimmy in the main gear legs.  If I let go of the brakes it stops.  Seems to happen at slow speeds, anybody else have this phenomonon?

Easy, I think, a rotor is warped or glazed in one spot. Is the 'shimmy' proportional to ground speed?

My $.02

Rick
Cozy MK-IV, plans #1477. 90% done, 70% to go!
Currently working on the canopy, side windows just installed.
My hobby at: http://zggtr.org My plane at: http://cozy.zggtr.org/

Offline av-mech

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Re: Varieze Rudder trim
« Reply #2 on: July 10, 2011, 12:22:52 PM »
I think you may be right concerning a glazed disk or warped.
Arnold Holmes
N80SH
IA 2712249
EAA 519850
TC#4476
Av-Mech.com

Offline Joe Dubner

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Re: Varieze Rudder trim
« Reply #3 on: July 11, 2011, 07:56:10 AM »
Also, when braking at slower speeds I sometimes get some shimmy in the main gear legs.  If I let go of the brakes it stops.  Seems to happen at slow speeds, anybody else have this phenomonon?

I did until I replaced the brake discs with new Rapco discs (about $80 each from Aircraft Spruce; see http://www.aircraftspruce.com/catalog/lgpages/rapcodisks.php). 

Gary Hertzler had advised me that would fix my shimmy problem and he was right.  Seems a warped disc will excite the main gear enough to cause shimmy at a certain speed range.  My old discs had about 1000 hours on them (although that's hardly a measure of their use) and didn't seem terribly warped or grooved but they were too thin to true up (too little material left).

--
Joe
Long-EZ 821RP
Independence, OR
Joe Dubner
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Offline av-mech

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Re: Varieze Rudder trim
« Reply #4 on: July 11, 2011, 12:56:26 PM »
Joe,

Thanks for your reply.  I think that may be the problem.  I'll have to measure the thickness and see if there is enough meat left to grind flat.  If not, then new one's will be the answer.
Arnold Holmes
N80SH
IA 2712249
EAA 519850
TC#4476
Av-Mech.com

Offline LongEZDaveA

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Re: Varieze Rudder trim
« Reply #5 on: July 11, 2011, 04:27:39 PM »
Make sure the calipers can slide easily on the pins.  I don't know the proper terminology for the two pins, but you probably get my meaning.  If the caliper can't slide easily and the rotor is warped, it generates uneven braking as the wheel/rotor rotates.

FWIW, my brakes shimy the gear legs at around 25-30 MPH.  I just avoid braking in that range, but sometimes it's unavoidable.
Dave Adams, Long EZ N83DT (Race 83) Villa Ridge, MO

Offline av-mech

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Re: Varieze Rudder trim
« Reply #6 on: July 12, 2011, 03:23:10 PM »
Dave,

I would say that my brakes/legs seem to shimmy around 10 mph but it's hard to tell exactly.  I notice that the pins on the caliper and the holes in the torque plate of which they fit into have actually a little too much play.  If you kick the tire you can get them to rattle just a little.  I plan on buying new pins and torque plate after OSH.  The brakes work really good, I think the whole system is just a little worn.  Thinking of buying a set of wheel pants from James Aircraft, anybody have experience with his pants on an eze?
Arnold Holmes
N80SH
IA 2712249
EAA 519850
TC#4476
Av-Mech.com

Offline easyrider

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Re: Varieze Rudder trim
« Reply #7 on: July 13, 2011, 11:56:44 AM »
I have a set of James wheel pants.
They take some work but fit OK
Easyrider

Offline av-mech

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Re: Varieze Rudder trim
« Reply #8 on: July 13, 2011, 12:48:39 PM »
easyrider,

any chance you could find some time to send me three or photos of how they look installed??

if you can (and I know we are all  busy) send them to

Arnold@av-mech.com
Arnold Holmes
N80SH
IA 2712249
EAA 519850
TC#4476
Av-Mech.com

Offline av-mech

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Re: Varieze Rudder trim
« Reply #9 on: July 22, 2011, 12:04:05 PM »
I have now installed and 1/8 shim under the left rudder and that has all but eliminated my rudder trim problems.  Attached is a picture of my rudder with the shim installed.  It now climbs and cruises with no rudder trim needed.  A bit of a relief as I was getting tired of chasing it all over the place.
Arnold Holmes
N80SH
IA 2712249
EAA 519850
TC#4476
Av-Mech.com

Offline rorsolits

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Re: Varieze Rudder trim
« Reply #10 on: July 25, 2011, 02:57:19 PM »
Good Luck with Osh Arnold, your vari looked good cruising over at 1700
Rob
Eracer in Waiting

Offline Joe Person

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Re: Varieze Rudder trim
« Reply #11 on: July 25, 2011, 05:20:12 PM »
See CP 24, Page 4, for the whole narrative about eliminating the VEZ adjustable rudder trim.  Further to this, a good read of all of the CPs for any new owner of a RAF design is prudent.
Joe Person
VariEze N79JN
Cozy #879 Under Construction
EAA Tech Counselor 4418
Bothell, WA (KPAE)

Offline av-mech

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Re: Varieze Rudder trim
« Reply #12 on: July 25, 2011, 06:33:28 PM »
Rob,

Thanks it was fun flying over to Orlando North, good to get practice on a shorter narrower strip.

Joe,

i have been working through the CP's but it takes time to shift through them all.  It's really good reading.

"Wheel" up at 0700 tomorrow morning.
Arnold Holmes
N80SH
IA 2712249
EAA 519850
TC#4476
Av-Mech.com