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grs-pms(at)comcast.net
Guest

Posted: Sat May 12, 2007 1:01 pm Post subject: Wing sweep and recent crashes

Hello list:

  

 Before we unleash a hurricane of opinion on  the subject of sweep, let's agree on a definition of the term.  A  textbook definition of sweep angle is the difference between 90 degrees and  the angle the 25 percent chord line of the wing (seen in  planform) makes with the centerline of the fuselage.  If that  angle is 90 degrees,the wing has zero sweep.  This means that a  tapered wing with the leading edge at a right angle to the fuselage  centerline actually has forward sweep.  A tapered wing with the  trailing edge at a right angle to the fuselage centerline is swept  back. 

  

 For the range of speeds and airfoil thicknesses we  are concerned about a few degrees of sweep either way will probably not  have enough effect on the wing structure to explain the wing failures  we are trying to understand.

  

 George Swinford

   [quote][b]

ihab.awad(at)gmail.com
Guest

Posted: Sat May 12, 2007 2:41 pm Post subject: Wing sweep and recent crashes

On 5/12/07, George Swinford <grs-pms(at)comcast.net> wrote:

 	  Quote: 	
		   Before we unleash a hurricane of opinion on the subject of sweep, let's

 agree on a definition of the term.  ...


	


For the purposes of this problem, I suspect the relevant issue is this

(and please correct me if I'm wrong): Viewed from the top, the center

of lift of the wing traces a roughly spanwise line, and the structural

centroid of the wing also traces a roughly spanwise line. Where do

these lines lie in relation to one another?



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA

ihab.awad(at)gmail.com
Guest

Posted: Sat May 12, 2007 2:49 pm Post subject: Wing sweep and recent crashes

On 5/12/07, ihab.awad(at)gmail.com <ihab.awad(at)gmail.com> wrote:

 	  Quote: 	
		   For the purposes of this problem, I suspect the relevant issue is this

 (and please correct me if I'm wrong): ...


	


No sorry ... I typed too soon. Consider the case of a perfectly

rectangular wing with zero sweep, with the center of lift behind the

structural centroid, and thus stable. Now sweep that same wing

forwards. Now the action of lift, to increase dihedral along the axis

of the wing, also acts to increase angle of attack and can make the

wing unstable. Hence my analysis is too simplistic. Never mind.



Ihab



-- 

Ihab A.B. Awad, Palo Alto, CA

Jeyoung65(at)aol.com
Guest

Posted: Sat May 12, 2007 3:02 pm Post subject: Wing sweep and recent crashes

Could it be the angle of the spar is to set the angle of  incidence? Jerry GA

 http://en.wikipedia.org/wiki/Angle_of_incidence

  

 DO NOT ARCHIVE"



See what's free at AOL.com. 

  [quote][b]

gboothe(at)calply.com
Guest

Posted: Sat May 12, 2007 5:49 pm Post subject: Wing sweep and recent crashes

MAN! With all your theorizing, conjecturing and armchair quarterbacking, you guys can take a half story and twist it 9 ways from Sunday! Without knowing anything but a small portion of the facts you are willing to question the basics of the CH designs!   

   

What I think is really happening, is that some ‘educated’ people are using this list to expound their knowledge and education. If you don’t like the 601XL design…DON’T BUILD IT!!  

   

As for me, I put my $$$ on Mr. Heintz. I’m not building an XL, but I happen to think the airplane is designed as is for a reason…a reason I don’t understand, because, if I did, I would design and build my own! Here’s a thought:  If you don’t understand why the wing is swept forward, maybe Chris Heintz knows more than you.  

   

Don’t bother telling me that an ‘intelligent’ builder should question everything. Am I willing to just blindly follow? Uh, yeah (see above).   

   

My vote is that this is a useless thread that will do little or nothing to help anyone.  

   

Gary Boothe 

 Cool, CA 

 601 HDSTD, WW Conversion 90% done, 

 Tail done, wings done, working on c-section   

   

        [quote][b]

Kevin Bonds

Joined: 09 Jan 2006
Posts: 171
Location: Nashville, Tn

Posted: Sat May 12, 2007 7:35 pm Post subject: Wing sweep and recent crashes

Good question. With a tapered wing having a spar that is parallel to the leading edge . . . hmmm.

 -------------- Original message ----------------------

From: ihab.awad(at)gmail.com

 	  Quote: 	

 On 5/12/07, George Swinford <grs-pms(at)comcast.net> wrote:

 > Before we unleash a hurricane of opinion on the subject of sweep, let's

 > agree on a definition of the term.  ...

 For the purposes of this problem, I suspect the relevant issue is this

 (and please correct me if I'm wrong): Viewed from the top, the center

 of lift of the wing traces a roughly spanwise line, and the structural

 centroid of the wing also traces a roughly spanwise line. Where do

 these lines lie in relation to one another?

 Ihab

 -- 

 Ihab A.B. Awad, Palo Alto, CA

_________________
KevinBonds
Nashville, TN
Plans-building Zenith CH601XL w/Corvair Power
http://home.comcast.net/~kevinbonds

purplemoon99(at)bellsouth
Guest

Posted: Sat May 12, 2007 7:39 pm Post subject: Wing sweep and recent crashes

DON'T HOLD BACK  Gary, tell us what you really  think...

 [quote]   ---

Kevin Bonds

Joined: 09 Jan 2006
Posts: 171
Location: Nashville, Tn

Posted: Sat May 12, 2007 8:01 pm Post subject: Wing sweep and recent crashes

_________________
KevinBonds
Nashville, TN
Plans-building Zenith CH601XL w/Corvair Power
http://home.comcast.net/~kevinbonds

Kevin Bonds

Joined: 09 Jan 2006
Posts: 171
Location: Nashville, Tn

Posted: Sat May 12, 2007 8:35 pm Post subject: Wing sweep and recent crashes

_________________
KevinBonds
Nashville, TN
Plans-building Zenith CH601XL w/Corvair Power
http://home.comcast.net/~kevinbonds

planecrazydld(at)yahoo.co
Guest

Posted: Sun May 13, 2007 3:24 am Post subject: Wing sweep and recent crashes

see below



Gary Boothe <gboothe(at)calply.com> wrote:[quote]              MAN! With all your theorizing, conjecturing and armchair quarterbacking, you guys can take a half story and twist it 9 ways from Sunday! Without knowing anything but a small portion of the facts you are willing to question the basics of the CH designs! 

   

  What I think is really happening, is that some ‘educated’ people are using this list to expound their knowledge and education. If you don’t like the 601XL design…DON’T BUILD IT!!  I have built planes before  and will continue to build my XL - with very few alterations in the basic design. I believe that perhaps I have been looking at the fact that the XL can and will accelerate very rapidly beyond the skill capability of a pilot with limited experience. Velocity is danger in a lightly built plane. If the designer were NOT CH, I would have changed my mind a long time ago.  

   

  As for me, I put my $$$ on Mr. Heintz. I’m not building an XL, but I happen to think the airplane is designed as is for a reason…a reason I don’t understand, because, if I did, I would design and build my own! Here’s a  thought:  If you don’t understand why the wing is swept forward, maybe Chris Heintz knows more than you.  I have asked the question but have not gotten an answer.  I assume that the wing is that way as a consequence of the angled spar - and I assume that CH  was fully aware of the  possibilities. Most likely it was a design compromise - all of them are.

   

  Don’t bother telling me that an ‘intelligent’ builder should question everything. Am I willing to just blindly follow? Uh, yeah (see above).

We should all be so willing to "blindly" follow the design when it comes from someone with the qualification of a CH. Two issues pop out: I am not convinced that CH did all the design as there are a number of components that do not look like classic CH. There is also the issue that modern day homebuilders do not tend to avail themselves of the body of classic knowledge readily at hand that present issues that no plan set can afford to try and educate on.

 

   

  My vote is that this is a useless thread that will do little or nothing to help anyone. ...and I  agree. This will be my last post on the issue.  I apologize for offending.

   

  Gary Boothe 

 Cool, CA 

 601 HDSTD, WW Conversion 90% done, 

 Tail done, wings done, working on c-section 

   

  

        [quote][b]  [quote][b]

purplemoon99(at)bellsouth
Guest

Posted: Sun May 13, 2007 5:07 am Post subject: Wing sweep and recent crashes

David, It's to bad,you're not going to post any  more on this sub. I found it very intresting, and educating,but knowledge and  information can always be replaced by blind fatith , and " I PUTT'S MY  MONEY UP"...Me,I like to hear from people like Klass,Kevin,and your self. I have  a 601Xl ,and the thing that keeps coming up in my mind is what happened over  the "Cooling Tower"and the rash of folding wings,to me it just doesn't  wash. I just don't want to wind up standing in front of St. Peter or the  devil,And they ask me how I got there? and I'll have to tell them "I drove a 601  XL with NO WINGS..  thanks again for your input.  fly Safe    Joe N101HD

  	  Quote: 	
		     ----- Original Message ,

   From:    David    Downey (planecrazydld(at)yahoo.com) 

   To: zenith-list(at)matronics.com (zenith-list(at)matronics.com) 

   Sent: Sunday, May 13, 2007 7:23 AM

   Subject: Re: Wing sweep and    recent crashes

   



see below



Gary Boothe <gboothe(at)calply.com (gboothe(at)calply.com)> wrote:    	  Quote: 	
		            (at)page Section1 {size: 8.5in 11.0in; margin: 1.0in 1.25in 1.0in 1.25in; } P.MsoNormal { 	FONT-SIZE: 12pt; MARGIN: 0in 0in 0pt; FONT-FAMILY: "Times New Roman" } LI.MsoNormal { 	FONT-SIZE: 12pt; MARGIN: 0in 0in 0pt; FONT-FAMILY: "Times New Roman" } DIV.MsoNormal { 	FONT-SIZE: 12pt; MARGIN: 0in 0in 0pt; FONT-FAMILY: "Times New Roman" } A:link { 	COLOR: blue; TEXT-DECORATION: underline } SPAN.MsoHyperlink { 	COLOR: blue; TEXT-DECORATION: underline } A:visited { 	COLOR: purple; TEXT-DECORATION: underline } SPAN.MsoHyperlinkFollowed { 	COLOR: purple; TEXT-DECORATION: underline } P { 	FONT-SIZE: 12pt; MARGIN-LEFT: 0in; MARGIN-RIGHT: 0in; FONT-FAMILY: "Times New Roman"; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto } SPAN.EmailStyle17 { 	COLOR: windowtext; FONT-FAMILY: Arial; mso-style-type: personal-compose } DIV.Section1 { 	page: Section1 }            MAN! With all your theorizing,      conjecturing and armchair quarterbacking, you guys can take a half story and      twist it 9 ways from Sunday! Without knowing anything but a small portion of      the facts you are willing to question the basics of the CH designs!      

     

     What I think is really happening, is that some      ‘educated’ people are using this list to expound their knowledge and      education. If you don’t like the 601XL design…DON’T BUILD IT!!  I have built planes before and will continue to      build my XL - with very few alterations in the basic design. I believe that      perhaps I have been looking at the fact that the XL can and will accelerate      very rapidly beyond the skill capability of a pilot with limited experience.      Velocity is danger in a      lightly built plane. If the designer were NOT CH, I would have changed my      mind a long time ago. 

     

     As for me, I put my $$$ on Mr.      Heintz. I’m not building an XL, but I happen to think the airplane is      designed as is for a reason…a reason I don’t understand, because, if I did,      I would design and build my own! Here’s a thought:  If you don’t understand why the wing is swept      forward, maybe Chris Heintz knows more than you.  I have asked the question but have not      gotten an answer.  I assume that the wing is that way as a consequence      of the angled spar - and I assume that CH  was fully aware of the       possibilities. Most likely it was a design compromise - all of them      are.

     

     Don’t bother telling me that an      ‘intelligent’ builder should question everything. Am I willing to just      blindly follow? Uh, yeah (see above).

     We should all be so willing      to "blindly" follow the design when it comes from someone with the      qualification of a CH. Two issues pop out: I am not convinced that CH did      all the design as there are a number of components that do not look like      classic CH. There is also the issue that modern day homebuilders do not tend      to avail themselves of the body of classic knowledge readily at hand that      present issues that no plan set can afford to try and educate      on.



     

     My vote is that this is a      useless thread that will do little or nothing to help anyone. ...and I agree. This will be my last post on      the issue.  I apologize for      offending.

     

     Gary Boothe      

Cool, CA 

601      HDSTD, WW Conversion 90% done, 

Tail done, wings      done, working on c-section 

     



 	  Quote: 	
		  



 	  Quote: 	
		  [b]



href="http://www.matronics.com/Navigator?Zenith-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com



	
[/b] 	
	
	
    [quote][b]

skyguynca

Joined: 05 Jun 2006
Posts: 128

Posted: Sun May 13, 2007 6:14 am Post subject: Wing sweep and recent crashes

Yeah Gary!!! That totally answered my questions.  Even though I have already build a HD your last comment totally straightened me  out, wow so simple.

  

 David Mikesell

23597 N. Hwy 99

Acampo, CA 95220

209-224-4485

skyguynca(at)skyguynca.com (skyguynca(at)skyguynca.com)

www.skyguynca.com

 [quote]   ---

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Mon May 14, 2007 8:43 am Post subject: Re: Wing sweep and recent crashes

Is this how you live your life, assuming that all 'professionals' are always correct all of the time? That's a pretty dangerous mindset, and probably costs you a lot over the years always relying on experts.



I'm not saying CH is a bad designer, but I wouldn't be so quick t assume that everyone here is a dummy. At least one actual aeronautical engineer has chimed in here and questioned the XL wing design.



It's quite possible CH got a little too comfortable with the CH601HD design and maybe was a little too cavalier presumptive designing the XL. Ever watch Engineering Disasters on Modern Marvels on the History Channel? Whole teams of engineers that designed something and didn't catch one little thing and problems showed up later. Doesn't mean any of them were bad people or stupid, or lazy etc... It just means that some end condition was not meant or inadvertently either overlooked or miscalculated. An 18.5 million dollar Mariner rocket had to be destroyed on launch because it turned out later, someone had a minus sign instead of a a plus sign in some software. How about 3 mile island? How about the engine installation prodcedure for a DC-10, that was followed, but then the people went to lunch halfway through and in the meantime the forklift lost some hydraulic pressure and cracked the engine mount and the engine fell off over Chicago 2 weeks later. Maybe the manual should have said, do not stop for lunch while installing the engine. There's a million potential gotchas that have nothing to do with inconsiderate, or careless, or stupid people. But to just blindly accept that it is in fact correct is dangerous. Before all of this, I would have accepted that in fact the design is correct simply because of no frame of reference other than CH is a top notch designer. Now that there's new input I think it's worth double and triple checking. CH is a human, not God. A qualified human, yes, but not God.



[quote="gboothe(at)calply.com"]MAN! With all your theorizing, conjecturing and armchair quarterbacking, you guys can take a half story and twist it 9 ways from Sunday! Without knowing anything but a small portion of the facts you are willing to question the basics of the CH designs!   

   

What I think is really happening, is that some â€˜educatedâ€™ people are using this list to expound their knowledge and education. If you donâ€™t like the 601XL designâ€¦DONâ€™T BUILD IT!!  

   

As for me, I put my $$$ on Mr. Heintz. Iâ€™m not building an XL, but I happen to think the airplane is designed as is for a reasonâ€¦a reason I donâ€™t understand, because, if I did, I would design and build my own! Hereâ€™s a thought:  If you donâ€™t understand why the wing is swept forward, maybe Chris Heintz knows more than you.  

   

Donâ€™t bother telling me that an â€˜intelligentâ€™ builder should question everything. Am I willing to just blindly follow? Uh, yeah (see above).   

   

My vote is that this is a useless thread that will do little or nothing to help anyone.  

   

Gary Boothe 

 Cool, CA 

 601 HDSTD, WW Conversion 90% done, 

 Tail done, wings done, working on c-section   

   

         	  Quote: 	
		  [b]

gboothe5(at)comcast.net
Guest

Posted: Mon May 14, 2007 12:08 pm Post subject: Wing sweep and recent crashes

Andy,



My point is that I have paid for a design from a proven aircraft designer, and choose to follow his advice over everyone else's; especially your referenced "aeronautical engineer." Who is this person? What has he designed? It's quite possible to get a degree in Aeronautical Engineering and spend the next 30 years designing air conditioning units for Boeing. The Air Force Academy graduates a plethora of Aeronautical Engineers who spend the rest of their productive lives flying commercially. 



Many jumped in to criticize the supposed "forward sweep," but it took Scott Laughlin to describe how that's really not the design of the wing. 



Furthermore, I just read a post that advises more ribs!! For Heavens sake!! Do you not see how dangerous it is to question the wing design? Do you see where all this is leading? Do you really want some half informed builder to take the advice of a non-descript lister?



Add to this the fact that NO ONE is more concerned about his design than the Designer. He has proven this in His last letter to builders. Anyone who feels truly qualified to question His design should contact Him and offer their services.



This List is no place to question the basic design of the manufacturer. I stand by my statement that if you don't like this design, then don't build it! If all you engineers and theorists want to discuss the pros and cons of a wing design you should all meet for coffee at an internet cafÃ© on Saturday mornings. 



Gary Boothe 

Cool, CA 

601 HDSTD, WW Conversion 90% done, 

Tail done, wings done, working on c-section



--

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Wed May 16, 2007 5:22 am Post subject: Re: Wing sweep and recent crashes

I respect Scott. He's a good guy and very intelligent. I also respect CH. They have a good business model and seem to be thorough in their engineering. Doesn't make Zenith immune from the stray gotcha, just less likely. But from what I gathered from what Scott said, it sounded like the he considered the wing to not have forward sweep because it in fact has no forward sweep when tilted back for wing fitting per the plans. Yes, at that angle it has not forward sweep, but return the plane to level and it does in fact have forward sweep. I don't think forward sweep is a problem provided there's enough rigidity in the wing to counter any twisting moment. Looking at those widely spaced ribs, particularly when other people have reported frustrations with some oilcanning that can't seem to be eliminated even with the most careful construction indicates to me that a few extra ribs there would not only eliminate the oil-canning, but also eliminate any play in the wing that may result from a slight bit of oil-canning. Even if you're lubky enough tp get it so that there's no oil-canning on the bottom skin, it's still an area that could be made stronger with a few added ribs. The top skin is not as susceptible to oil-canning because the skin has a more distinct curve to it, but even so, the area on the top as well is not as strong as it could be for as little as maybe 2.5 lbs in ribs added between the existing ribs outboard of the wingwalk.



I'm willing to trust CH on his design skills, I'm also willing to question the XL too being that it's a new newer design and they haven't fully described their static as well as dynamic testing. I also have a 601XL sitting on my bench and I can see just through comparison that the XL wing, to me, seems to be a little anemic compared to some other wings I've seen. It may infact pass with flying colors under static loads and MOST normal conditions, but when someone reports wing flutter while flying over a power station, that makes me take notice. I can see a bumpy ride, possibly even a really bumpy ride, but just a normal cruise speed over a power station should not induce wing flutter. I've been in Cessna 150s in some pretty turbulent air they would be akin to 3Gs for a one to 2 seconds at a crack, it was a rough ride, but didn't induce anything like wing flutter. I don't think it's too much to ask to double check that this wing is in fact strong and rigid enough to cope with certain 5 sigma fat tail conditions.



 	  gboothe5(at)comcast.net wrote: 	
		  Andy,



My point is that I have paid for a design from a proven aircraft designer, and choose to follow his advice over everyone else's; especially your referenced "aeronautical engineer." Who is this person? What has he designed? It's quite possible to get a degree in Aeronautical Engineering and spend the next 30 years designing air conditioning units for Boeing. The Air Force Academy graduates a plethora of Aeronautical Engineers who spend the rest of their productive lives flying commercially. 



Many jumped in to criticize the supposed "forward sweep," but it took Scott Laughlin to describe how that's really not the design of the wing. 



Furthermore, I just read a post that advises more ribs!! For Heavens sake!! Do you not see how dangerous it is to question the wing design? Do you see where all this is leading? Do you really want some half informed builder to take the advice of a non-descript lister?



Add to this the fact that NO ONE is more concerned about his design than the Designer. He has proven this in His last letter to builders. Anyone who feels truly qualified to question His design should contact Him and offer their services.



This List is no place to question the basic design of the manufacturer. I stand by my statement that if you don't like this design, then don't build it! If all you engineers and theorists want to discuss the pros and cons of a wing design you should all meet for coffee at an internet cafÃ© on Saturday mornings. 



Gary Boothe 

Cool, CA 

601 HDSTD, WW Conversion 90% done, 

Tail done, wings done, working on c-section



--

steveadams

Joined: 10 Jan 2006
Posts: 191

Posted: Wed May 16, 2007 10:16 am Post subject: Re: Wing sweep and recent crashes

Ashontz, I'm sorry but I am having trouble following your reasoning. For starters you ignore the fact that the latest 2 failures have pretty clear explanations for the failures. Next you say a major problem is the forward swept wing, then when someone explains that the wing is not forward swept in flight, you maintain that it is when sitting on the ground. Huh? I think most stresses on an aircraft are generally imposed while in flight. Then you cite the RV wing having a bunch more ribs and only 1 failure, so you conclude that the xl needs more ribs. When it's pointed out that RV wings fail with some regularity, you start making up reasons why the RV wings probably fail. The you use a report of turbulence over a cooling tower that lasted quite a while, and did not become worse with increasing speed, as a starting point to postulate that the XL wing was experiencing flutter, and go off on that tangent and why the xl wing needs to be stiffer. You want to beef up the spar cap and beef up the wing attach points and add more ribs. Why not double the skin thickness too. More is always better. right? Where is the calculated weakest point of the xl wing? How will the loads on the spar, wing attach points, and skin change with the addition of ribs? What would happen to say, the 747 wing if you stiffenned it so as not to allow all the flex and twisting experienced during flight? 



I don't think CH is a god, however he does know something about aircraft design. All I have seen in your posts is speculation without any factual basis, a disregard for any facts offered by other posters, a rush to fix problems you don't know exist and don't understand how to fix, and despite whatever degrees or credentials you may have, no significant knowledge of aircraft design.

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Wed May 16, 2007 11:06 am Post subject: Re: Wing sweep and recent crashes

Do you you always fly at 9 degrees angle of attack? If so then you'll never have forward sweep.



Are they clear, maybe. I also know that 20+ years of 601HDs have resulted in no structural failures, whereas 6 years of 601XLs have resulted in 4 or 5. Statistically that's backwards if they're both rated the same in load limit. I doubt there's 5 times as many 601XLs as HD and HDSs over the past 20 years. Even if there were twice as many XLs as all the others combined, that's still statistically backwards indicating something special about the XL.



Again, back to the Lies, Damn Lies, and statistics. How many RVs are there over 20 years? How amyn people tend to fly them as personal aerobatic jets. The RV wing is in fact a thin wing.



I'm not coming down on CH here, I'm just distinctly interested in what's going on with this wing if anything. Pardon me for trying to be as safe as possible. Personally, I like to know. I like to know to the point of zero doubt. That's just the way I am. This is how I conduct my life. You don't have to like it. If I'm suspicious of something I will investigate it til I'm comfortable with the knowledge gleaned, BY ME. Not by someone that says everything will be ok.



As far as the 747 wing, I did say every wing will flutter at some point/speed. To so trying to totally stop flutter is pointless. Trying to eliminate it below Vne is not pointless though. Also, the flutter is the stress that the wing is experiencing. Eliminate the flutter and eliminate the stress.



Why not double the skin thickness too



Why, because apparently the tension force of the skin is sufficient IN TENSION. It's also probably sufficient in compression provided the skin can be keep aligned (ribs do that for both).



As far as the spar cap, I didn't suggest beefing that up, I suggested using a angled extrusion, same thinkness as the cap, that's 20mm wide to hold the skin on the spar. Why use .032 on top of a 1/4" cap when you could have just used an angled extrusion for the top cap that's 90 degrees? It's gotta be stronger than the .032 cap angle. Maybe not a big deal, but now that I think about it, why not go for a one piece deal that's even stronger.



I don't think CH is a god, however he does know something about aircraft design. All I have seen in your posts is speculation without any factual basis, a disregard for any facts offered by other posters, a rush to fix problems you don't know exist and don't understand how to fix, and despite whatever degrees or credentials you may have, no significant knowledge of aircraft design.



Are you suggesting I can't think for myself. I haven't once sent you a form that says you must accept my theories and change your aircraft accordingly. I'm just thinking out load as are other people on the topic, and some of them are of the same mindset as me about this. Are you trying to stifle my inquisitiveness of the subject for some reason? I take getting in an airplane and relying on it seriously. I consider this a pre-pre-flight walk around. When I hear of wing flutter and structural failures of a plane I'm building I take note. Sorry for making you uncomfortable. Have I struck a nerve as far as things you haven't thought of about this wing that now has you thinking. In some ways I hope so because it's for the better. Maybe there's absolutely nothing wrong with this wing and it was just yahoos acting like a-holes. But I'd have to think over the 20+ years of HDs and HDSs there were plenty of yahoos that flew them that apparently never ripped the wings off. Personally, I have no intention of flying ine like it's a fighter yet, I'd also like to never experience wing flutter (for even 1/10th of a second) like the guy did over the power plant.



As for your disjointed comments, hopefully I've put them to rest.



 	  steveadams wrote: 	
		  Ashontz, I'm sorry but I am having trouble following your reasoning. For starters you ignore the fact that the latest 2 failures have pretty clear explanations for the failures. Next you say a major problem is the forward swept wing, then when someone explains that the wing is not forward swept in flight, you maintain that it is when sitting on the ground. Huh? I think most stresses on an aircraft are generally imposed while in flight. Then you cite the RV wing having a bunch more ribs and only 1 failure, so you conclude that the xl needs more ribs. When it's pointed out that RV wings fail with some regularity, you start making up reasons why the RV wings probably fail. The you use a report of turbulence over a cooling tower that lasted quite a while, and did not become worse with increasing speed, as a starting point to postulate that the XL wing was experiencing flutter, and go off on that tangent and why the xl wing needs to be stiffer. You want to beef up the spar cap and beef up the wing attach points and add more ribs. Why not double the skin thickness too. More is always better. right? Where is the calculated weakest point of the xl wing? How will the loads on the spar, wing attach points, and skin change with the addition of ribs? What would happen to say, the 747 wing if you stiffenned it so as not to allow all the flex and twisting experienced during flight? 



I don't think CH is a god, however he does know something about aircraft design. All I have seen in your posts is speculation without any factual basis, a disregard for any facts offered by other posters, a rush to fix problems you don't know exist and don't understand how to fix, and despite whatever degrees or credentials you may have, no significant knowledge of aircraft design.

steveadams

Joined: 10 Jan 2006
Posts: 191

Posted: Wed May 16, 2007 12:26 pm Post subject: Re: Wing sweep and recent crashes

 	  ashontz wrote: 	
		  



I'm not coming down on CH here, I'm just distinctly interested in what's going on with this wing if anything. Pardon me for trying to be as safe as possible. Personally, I like to know. I like to know to the point of zero doubt. That's just the way I am. This is how I conduct my life. You don't have to like it. If I'm suspicious of something I will investigate it til I'm comfortable with the knowledge gleaned, BY ME. Not by someone that says everything will be ok. 	




Everyone wants to know the answer, but what "knowledge" have you gleaned? Do you know the weak point of the wing, or are you taking a wild a__ guess and throwing added aluminum at it. Do you know the results of the stress analysis, or is that factual knowledge unnecissary detail. Do you know how much addition stress will be transfered to the skins and wing attach points if you stiffin up the wing? What are the results of flutter testing on the XL, by both the factory and numerous builders? How does a designer determine how many ribs are required, how thick the skins need to be, how beefy the spar needs to be, and how strong the attach points need to be? How does a designer determine whether mass balancing is required or aerodynamic balancing of control surfaces is sufficient?



[/quote]As far as the 747 wing, I did say every wing will flutter at some point/speed. To so trying to totally stop flutter is pointless. Trying to eliminate it below Vne is not pointless though. Also, the flutter is the stress that the wing is experiencing. Eliminate the flutter and eliminate the stress.

[/quote]



I didn't say anything about flutter, I said stiffen the wing so it doesn't flex. If you did that the wing would fail.



[/quote]

As far as the spar cap, I didn't suggest beefing that up, I suggested using a angled extrusion, same thinkness as the cap, that's 20mm wide to hold the skin on the spar. Why use .032 on top of a 1/4" cap when you could have just used an angled extrusion for the top cap that's 90 degrees? It's gotta be stronger than the .032 cap angle. Maybe not a big deal, but now that I think about it, why not go for a one piece deal that's even stronger.

[/quote]



So if you strengthen the cap, how is that going to change the distribution of forces in the wing? If it makes the wing stiffer, how much are you going to need to beef up the wing attach points to account for to redistribution of forces?



[/quote]

Are you suggesting I can't think for myself. I haven't once sent you a form that says you must accept my theories and change your aircraft accordingly. I'm just thinking out load as are other people on the topic, and some of them are of the same mindset as me about this. Are you trying to stifle my inquisitiveness of the subject for some reason? I take getting in an airplane and relying on it seriously. I consider this a pre-pre-flight walk around. When I hear of wing flutter and structural failures of a plane I'm building I take note. Sorry for making you uncomfortable. Have I struck a nerve as far as things you haven't thought of about this wing that now has you thinking. In some ways I hope so because it's for the better. Maybe there's absolutely nothing wrong with this wing and it was just yahoos acting like a-holes. But I'd have to think over the 20+ years of HDs and HDSs there were plenty of yahoos that flew them that apparently never ripped the wings off. Personally, I have no intention of flying ine like it's a fighter yet, I'd also like to never experience wing flutter (for even 1/10th of a second) like the guy did over the power plant.

[/quote]



No one is trying to stiffle your inquisitiveness. Be inquisitive and seek knowledge. However, to find an answer requires that you take the time and effort to understand the question. You've gone on and on with answers, but don't have any idea what question you are trying to answer. Somebody might read what you say, think it sounds intellegent, and modify their plane. That's everybody's choice to make, but I am trying to point out that the things you are saying have little basis in fact and are not well thought out. I'm not saying you're wrong, just that before you or anyone else starts making changes to their wings you had better make darn sure you know what you are doing.

ashontz

Joined: 27 Dec 2006
Posts: 723

Posted: Wed May 16, 2007 12:37 pm Post subject: Re: Wing sweep and recent crashes

I didn't say anything about flutter, I said stiffen the wing so it doesn't flex. If you did that the wing would fail



Why would the wing fail? Lets see, you torsionally stiffen it so that flutter and over-stress doesn't occur in the first place so the wing doesn't fold. So why would it fail? This isn't a 747 with a 170 foot wing span or whatever they have where the wing needs to flex a whole bunch less the attach points give. In the accounts where the wings folded on the 601xl, the attach points were fine, the wing itself folded. Besides, were ALREADY talking about a failing wing which the HD and HDS has never experienced.



You've gone on and on with answers, but don't have any idea what question you are trying to answer.



"Uh, Alex, what is wing flutter and wing failure not observed in 601HD and HDS."



 	  steveadams wrote: 	
		   	  ashontz wrote: 	
		  



I'm not coming down on CH here, I'm just distinctly interested in what's going on with this wing if anything. Pardon me for trying to be as safe as possible. Personally, I like to know. I like to know to the point of zero doubt. That's just the way I am. This is how I conduct my life. You don't have to like it. If I'm suspicious of something I will investigate it til I'm comfortable with the knowledge gleaned, BY ME. Not by someone that says everything will be ok. 	




Everyone wants to know the answer, but what "knowledge" have you gleaned? Do you know the weak point of the wing, or are you taking a wild a__ guess and throwing added aluminum at it. Do you know the results of the stress analysis, or is that factual knowledge unnecissary detail. Do you know how much addition stress will be transfered to the skins and wing attach points if you stiffin up the wing? What are the results of flutter testing on the XL, by both the factory and numerous builders? How does a designer determine how many ribs are required, how thick the skins need to be, how beefy the spar needs to be, and how strong the attach points need to be? How does a designer determine whether mass balancing is required or aerodynamic balancing of control surfaces is sufficient?



	
As far as the 747 wing, I did say every wing will flutter at some point/speed. To so trying to totally stop flutter is pointless. Trying to eliminate it below Vne is not pointless though. Also, the flutter is the stress that the wing is experiencing. Eliminate the flutter and eliminate the stress.

[/quote]



I didn't say anything about flutter, I said stiffen the wing so it doesn't flex. If you did that the wing would fail.



[/quote]

As far as the spar cap, I didn't suggest beefing that up, I suggested using a angled extrusion, same thinkness as the cap, that's 20mm wide to hold the skin on the spar. Why use .032 on top of a 1/4" cap when you could have just used an angled extrusion for the top cap that's 90 degrees? It's gotta be stronger than the .032 cap angle. Maybe not a big deal, but now that I think about it, why not go for a one piece deal that's even stronger.

[/quote]



So if you strengthen the cap, how is that going to change the distribution of forces in the wing? If it makes the wing stiffer, how much are you going to need to beef up the wing attach points to account for to redistribution of forces?



[/quote]

Are you suggesting I can't think for myself. I haven't once sent you a form that says you must accept my theories and change your aircraft accordingly. I'm just thinking out load as are other people on the topic, and some of them are of the same mindset as me about this. Are you trying to stifle my inquisitiveness of the subject for some reason? I take getting in an airplane and relying on it seriously. I consider this a pre-pre-flight walk around. When I hear of wing flutter and structural failures of a plane I'm building I take note. Sorry for making you uncomfortable. Have I struck a nerve as far as things you haven't thought of about this wing that now has you thinking. In some ways I hope so because it's for the better. Maybe there's absolutely nothing wrong with this wing and it was just yahoos acting like a-holes. But I'd have to think over the 20+ years of HDs and HDSs there were plenty of yahoos that flew them that apparently never ripped the wings off. Personally, I have no intention of flying ine like it's a fighter yet, I'd also like to never experience wing flutter (for even 1/10th of a second) like the guy did over the power plant.

[/quote]



No one is trying to stiffle your inquisitiveness. Be inquisitive and seek knowledge. However, to find an answer requires that you take the time and effort to understand the question. You've gone on and on with answers, but don't have any idea what question you are trying to answer. Somebody might read what you say, think it sounds intellegent, and modify their plane. That's everybody's choice to make, but I am trying to point out that the things you are saying have little basis in fact and are not well thought out. I'm not saying you're wrong, just that before you or anyone else starts making changes to their wings you had better make darn sure you know what you are doing.[/quote]

bill_dom(at)yahoo.com
Guest

Posted: Wed May 16, 2007 1:04 pm Post subject: Wing sweep and recent crashes

ashontz <ashontz(at)nbme.org> wrote:[quote]  --> Zenith-List message posted by: "ashontz" 



Do you you always fly at 9 degrees angle of attack? If so then you'll never have forward sweep.



Are  they clear, maybe. I also know that 20+ years of 601HDs have resulted  in no structural failures, whereas 6 years of 601XLs have resulted in 4  or 5. 

    

    I Have counted 3 cases of structural  failures in XLs, including the latest one that can be explained by  flying into IMC conditions by an unrated pilot. That leave us with 2  unexplained cases that are different in nature, one the wing folded up  the other, the aircraft came apart in mid flight.

    

  20 years of HD vs. 6 years for XL is not what should be used to  establish proportion, number of flight hours by  fleet is what should be  used. Unfortunatelly we don't have such information. I would tend to  believe that there are more hours flown in HDs that XLs because of the  HD being older, but one should not jump to such conclusion on time  alone.

    

  Statistically that's backwards if they're both rated the same in load  limit. I doubt there's 5 times as many 601XLs as HD and HDSs over the  past 20 years. Even if there were twice as many XLs as all the others  combined, that's still statistically backwards indicating something  special about the XL.



Again, back to the Lies, Damn Lies, and  statistics. How many RVs are there over 20 years? How amyn people tend  to fly them as personal aerobatic jets. The RV wing is in fact a thin  wing.

    

    I have counted 9 cases of structural  failures in RVs. One of these cases is very similar to the most recent  601XL crash. The RV flew into IMC conditions and came apart in  pieces.



I'm  not coming down on CH here, I'm just distinctly interested in what's  going on with this wing if anything. Pardon me for trying to be as safe  as possible. Personally, I like to know. I like to know to the point of  zero doubt. That's just the way I am. This is how I conduct my life.  You don't have to like it. If I'm suspicious of something I will  investigate it til I'm comfortable with the knowledge gleaned, BY ME.  Not by someone that says everything will be ok.

    

    I agree with you here however, are  you an aeronautical engineer with experience in light planes? One thing  is to question and that is part of our role as builders, another is to  come up with

  answers based on speculations because after all, we really don't know what causes these failures.

    

  Allow me to give you a friendly advice, resist the temptation to modify  or "beef up" your wing. If you can't, make sure you get  the blessing  from Zenith before doing any mod. Otherwise you might end up not  solving any problem and wasting your time, or worse yet, making things  worst.

    

    William Dominguez

  Zodiac 601XL Plans

  Miami, Florida

    [b]

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