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pilot4pay
Joined: 01 Jan 2007 Posts: 171 Location: Louisville, KY
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Posted: Fri Aug 22, 2008 7:39 am Post subject: Rudder trim |
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I'm planning on adding rudder trim to my 640. Does anyone know of a formula or a link to a website that might provide insight as to how to calculate area required to be effective but not oversize to be overly sensitive?
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_________________ Craig Smith
CH640 builder
SN: 0078
"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin |
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Christian Tremblay
Joined: 22 Aug 2008 Posts: 25 Location: Montreal
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Posted: Fri Aug 22, 2008 9:54 am Post subject: Re: Rudder trim |
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Hi Greg,
Try your question on zenith forum, more chance to have a answer on that question that could be considered general.
note : your trim will be electric for sure and will need to recalculate also the the counterbalance weight of the rudder.
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_________________ Christian Tremblay - Montreal, Qc
A guy who build a CH640 from plan - SN0059
www.zodiac640.com |
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Christian Tremblay
Joined: 22 Aug 2008 Posts: 25 Location: Montreal
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pilot4pay
Joined: 01 Jan 2007 Posts: 171 Location: Louisville, KY
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Posted: Tue Aug 26, 2008 8:50 am Post subject: Re: Rudder trim |
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I found a lot of information by searching the web, decided that I would wait until I'm flying to decide if the trim is necessary. The SAMA CH-2000 does not have rudder trim, and they have surveillance and aerial photography variants. If they can make a photo platform without a rudder trim, then the control force must be pretty light to keep the ball centered.
Found an interesting paper by Sebastian Heinze on aero-elastic structures. Looks like he's a pretty smart fellow.
Lots of other documents to read through now.
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_________________ Craig Smith
CH640 builder
SN: 0078
"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin
Last edited by pilot4pay on Thu Sep 11, 2008 7:25 am; edited 1 time in total |
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steveadams
Joined: 10 Jan 2006 Posts: 191
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Posted: Wed Sep 10, 2008 5:05 am Post subject: Re: Rudder trim |
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Depending on how you fly, you may or may not want or need rudder trim. The 640 has the self centering notch on the nose gear which works pretty well in keeping the front wheel centered in flight. You can adjust the rigging of the rudder to give some offset, i.e.- the rudder will offset slightly to the right when the front wheel is straight. Since the front wheel is held in a centered position in flight, this slight offset in the rudder essentially provides a fair amount of fixed trim to the rudder. The key is fine tuning the rigging during test flight to give feet on the floor coordinated flight in your normal cruise configuration. That way you won't spend 3 hours mashing the right pedal while cruising. If you don't do a lot of cross country flying, you may want to consider some type of variable trim system because you can only rig the rudder perfectly for one specific flight configuration. Unless your airplane is bent or otherwise out of rig, there should be no need for a fixed rudder trim as long as you don't modify the self centering design of the nose gear.
Steve
N621J
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pilot4pay
Joined: 01 Jan 2007 Posts: 171 Location: Louisville, KY
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Posted: Thu Sep 11, 2008 10:11 am Post subject: Re: Rudder trim |
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Thanks for the input Steve. I hadn't thought about the centering notch, or that I like the idea at all. All of my time has been in Cessna's. Our typical mission was long cross country, so the AP took care of keeping a heading, I would trim to the rudder to the ball.
The Cessna system is quite different from the Zenith. Yaw trim put tension on the rudder through the bungee.
At this point, If I were to make a choice, I would opt to leave out the notch. Not having experienced this set-up first hand, I am speculating, but it sounds like it would annoy me.
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_________________ Craig Smith
CH640 builder
SN: 0078
"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin |
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steveadams
Joined: 10 Jan 2006 Posts: 191
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Posted: Thu Sep 11, 2008 4:01 pm Post subject: Re: Rudder trim |
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The force to "override" the notch is not much and I doubt you could detect it in flight. It does however have enough force to be able to trim out the rudder in cruise flight. With the all flying rudder, I would think that the plane would be pretty squirrelly in yaw without the centering notch. I would think hard about it before taking it out.
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pilot4pay
Joined: 01 Jan 2007 Posts: 171 Location: Louisville, KY
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Posted: Fri Sep 12, 2008 3:33 am Post subject: Re: Rudder trim |
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I'm probably going to find a flight school that has an ALURUS on the line and book some time before I build the gear.
It's just that, in my flying experience, the yaw trim needs adjustment every new heading or change in wind direction. If the ball is not in the center, then the aircraft is producing more drag than necessary, the ride feels "weird", and you are burning more fuel. A detent in the yaw control will make an electric trim system difficult to implement. I don't care for ground adjustable tabs, so it would be either no trim or electric trim/no detent. I understand the part about rigging the rudder for the detent. Maybe that is where I should look to making an in flight adjustable yaw trim, rather than a tab/servo arrangement. Hmmmm. That approach would take some serious thought.
Again, I'll have to book some time and see for my self, I have lots of time before I have to cross that bridge anyway. right now cash flow has more to do with progress than time.
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_________________ Craig Smith
CH640 builder
SN: 0078
"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin |
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