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Zenith Rudder Design

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rbjjr

Joined: 18 Mar 2007
Posts: 36

Posted: Mon Mar 19, 2007 5:11 pm Post subject: Zenith Rudder Design

I am building the 701 and having fun and learning a lot.  It's a design that perfectly fits my mission.  



Although I know the "all flying" rudder is a Zenith trademark, it strikes me as really the only potential question in the overall design.  I am saying this as a layman, not being a designer or engineer, however.



The concentration of the hinges so low on the rudder seems to place much more stress on them than if the hinges were evenly spaced from top to bottom like many aircraft.  The forces acting on the rudder while turning are concentrated all at one end and only on two hinges a few inches apart on a relatively large surface.



Anyone ever heard of issues with this rudder design?  Anyone considered adding a third, middle hinge to provide some additional strength?  This is not meant as a criticism, just a question from someone new to homebuilding.



Thanks

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Mon Mar 19, 2007 5:26 pm Post subject: Zenith Rudder Design

There's nothing wrong with concentrating the load in a small area as  

long as the structure is strong enough to handle it. I've never heard  

any occurrences of rudders on Zodiacs falling off in flight and they  

are very easy to check out during pre-flight.

On Mar 19, 2007, at 9:11 PM, rbjjr wrote:



 	  Quote: 	
		   Although I know the "all flying" rudder is a Zenith trademark, it  

 strikes me as really the only potential question in the overall  

 design.  I am saying this as a layman, not being a designer or  

 engineer, however.



 The concentration of the hinges so low on the rudder seems to place  

 much more stress on them than if the hinges were evenly spaced from  

 top to bottom like many aircraft.  The forces acting on the rudder  

 while turning are concentrated all at one end and only on two  

 hinges a few inches apart on a relatively large surface.



 Anyone ever heard of issues with this rudder design?  Anyone  

 considered adding a third, middle hinge to provide some additional  

 strength?  This is not meant as a criticism, just a question from  

 someone new to homebuilding.




	


-- 

Bryan Martin

N61BM, CH 601 XL,

RAM Subaru, Stratus redrive.

do not archive.

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

dougsnash(at)yahoo.com
Guest

Posted: Tue Mar 20, 2007 3:00 am Post subject: Zenith Rudder Design

I am also building a CH-701.  I am by no means an

aeronautical engineer but I have the rudder built and

the fuselage sitting on the gear.



I think you might be overthinking the rudder situation

a little bit.  The attachment points are pretty stout

on this design.  The upper and lower hinge points feed

into the upper and lower longerons so a third hinge

point would add little addtional strength since it

wouldn't have anything of substance to attach to on

the fuselage.



Another thing that I've noticed is that with the nose

rib extending ahead of the hinge point, there will be

a certain amount of aerodynamic balance to the rudder

that should reduce any stresses significantly.



This is not a new design by any means.  The CH-701 has

been around for over twenty years.  I am far from an

expert on this but I have never heard of a failure of

the rudder hinge mechanism.  Although it does seem a

little odd at first, it is designed that way.

According to the designer (Chris Heintz), the whole

plane was designed with a good dose of safety margin

in mind.  Since the top speed is only just over 100

mph, the stresses on the tail are fairly low.



Good luck with your build.  I know I am looking

forward to getting mine into the sky.



Doug MacDonald

NW Ontario, Canada

CH-701 Scratch Builder

working on controls



do not archive



--- rbjjr <burkeandsusan(at)verizon.net> wrote:



 	  Quote: 	
		   Although I know the "all flying" rudder is a Zenith

 trademark, it strikes me as really the only

 potential question in the overall design.  I am

 saying this as a layman, not being a designer or

 engineer, however.

 

 The concentration of the hinges so low on the rudder

 seems to place much more stress on them than if the

 hinges were evenly spaced from top to bottom like

 many aircraft.  The forces acting on the rudder

 while turning are concentrated all at one end and

 only on two hinges a few inches apart on a

 relatively large surface.

 

 Anyone ever heard of issues with this rudder design?

  Anyone considered adding a third, middle hinge to

 provide some additional strength?  This is not meant

 as a criticism, just a question from someone new to

 homebuilding.

 

 Thanks


	


 

The fish are biting. 

Get more visitors on your site using Yahoo! Search Marketing.

http://searchmarketing.yahoo.com/arp/sponsoredsearch_v2.php

bill_dom(at)yahoo.com
Guest

Posted: Tue Mar 20, 2007 4:28 am Post subject: Zenith Rudder Design

This picture will give you an idea about the strenght of the rudder attachment:

  

  http://www.ch601.org/stories.htm

  

  This is a 601 but the rudder attachment is the same for both 601 and 701.

  

  William Dominguez

  Zodiac 601XL Plans

  Miami, Florida



rbjjr <burkeandsusan(at)verizon.net> wrote:[quote]  --> Zenith-List message posted by: "rbjjr" 



I am building the 701 and having fun and learning a lot.  It's a design that perfectly fits my mission.  



Although  I know the "all flying" rudder is a Zenith trademark, it strikes me as  really the only potential question in the overall design. I am saying  this as a layman, not being a designer or engineer, however.



The  concentration of the [quote][b]

zodierocket(at)hsfx.ca
Guest

Posted: Tue Mar 20, 2007 4:54 am Post subject: Zenith Rudder Design

Dam, I took that picture. You think I would have thought  of it ! Thanks William. That plane sat inverted for 6 months, through thunderstorms and wind, bashing the rudder every day almost. No One would touch it due to fear of law suit. But after 6 months the airline had it removed stating that it caused undue distress to it’s customers boarding their plane! I was told some of the comments by the pilots, non aviation people are pretty imaginative. By that way that picture is still posted as a reminder that polypropylene rope is not an acceptable tie down material. Best I have found by far is hemp rope for tie down.  ( No, I’m not a hemp hippie, it was proven to me at a show once and I did testing on my own and for strength and UV exposure, the hemp material outlasted everything else)  

     

Mark Townsend  Alma, Ontario  

Zodiac 601XL C-GOXL, CH701 just started  

www.ch601.org / www.ch701.com/ www.Osprey2.com  

   

do not archive  

  

--

dredmoody(at)cox.net
Guest

Posted: Tue Mar 20, 2007 5:07 am Post subject: Zenith Rudder Design

The rudder surface that is ahead of the hinge axis reduces the cable and rudder pedal pressure needed for a given amount of rudder deflection but does nothing to reduce the lateral load on the rudder during that deflection. That being said I agree that the hinge attachments are sufficiently strong as proven by no reports of incidents. It ain't broke so no need to fix it IMHO.



Dred



---- MacDonald Doug <dougsnash(at)yahoo.com> wrote: 

 	  Quote: 	
		   

 

 I am also building a CH-701.  I am by no means an

 aeronautical engineer but I have the rudder built and

 the fuselage sitting on the gear.

 

 I think you might be overthinking the rudder situation

 a little bit.  The attachment points are pretty stout

 on this design.  The upper and lower hinge points feed

 into the upper and lower longerons so a third hinge

 point would add little addtional strength since it

 wouldn't have anything of substance to attach to on

 the fuselage.

 

 Another thing that I've noticed is that with the nose

 rib extending ahead of the hinge point, there will be

 a certain amount of aerodynamic balance to the rudder

 that should reduce any stresses significantly.

 

 This is not a new design by any means.  The CH-701 has

 been around for over twenty years.  I am far from an

 expert on this but I have never heard of a failure of

 the rudder hinge mechanism.  Although it does seem a

 little odd at first, it is designed that way.

 According to the designer (Chris Heintz), the whole

 plane was designed with a good dose of safety margin

 in mind.  Since the top speed is only just over 100

 mph, the stresses on the tail are fairly low.

amyvega2005(at)earthlink.
Guest

Posted: Tue Mar 20, 2007 5:35 am Post subject: Zenith Rudder Design

if you go back a few years, to the 1970s, this rudder design for the ecception of size, has been on every zenith aircraft, back to the Cricket.   refer to the zenith journals to 1984.  that is well over 3000 aircraft.  If it ain't broke..........



Juan



--

pchapman(at)ionsys.com
Guest

Posted: Tue Mar 20, 2007 8:48 am Post subject: Zenith Rudder Design

Although nice things are being said about the integrity of the Zenith 

rudder design, with its two closely spaced hinges, I recall Chris 

Heintz writing in the Zenith newsletter some years ago about the 601 

(pre-XL series) and mild aerobatics. It was something about how 

although the aircraft spins fine, it hasn't officially been approved 

for spins, and besides, one wouldn't want to be doing them all the 

time given the closely spaced rudder hinges.



Unfortunately I don't have a source for the quote to confirm this. So 

the hinges may be fine for the job, but not exactly overbuilt for 

things the aircraft wasn't designed for.

Peter Chapman

Toronto, ON           601 HDS  /  912  /  C-GZDC

rbjjr

Joined: 18 Mar 2007
Posts: 36

Posted: Tue Mar 20, 2007 2:57 pm Post subject: Re: Zenith Rudder Design

Thanks all for the thoughtful responses and the picture is worth a thousand (more) words.



Rgds

cgbrt(at)mondenet.com
Guest

Posted: Fri Mar 23, 2007 8:27 pm Post subject: Zenith Rudder Design

I do not have a problem with the rudder design and the comments made. I do

however pay special attention to the attachments since the loss of the

rudder would most likely render the 701 uncontrolable.

Of all the bolts on the controls, the only one I have changed  in 450 hrs is

the top hinge on the rudder. It was noticeably worn after 300 hrs.

Happy STOLing,

Carl

701, 912, amphibs

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Tue Mar 27, 2007 5:54 am Post subject: Re: Zenith Rudder Design

I was just talking about this with Geoff Heap on Sunday (I was over his place and he had his plane out and the tail feathers on, looks good!). We both figured it wouldn't hurt to put a doubler plate in the lower and of the rudder spar that spans the distance between the hinge points. As it is those hinge brackets just rivet directly to the spar web. Considering the picture of the flipped over airplane, it's strong as it is. Add a double/stiffener plate (say .032) and you should be golden.

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