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Streamline Struts on a 701

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lrm(at)skyhawg.com
Guest

Posted: Wed Oct 31, 2007 5:33 am Post subject: Streamline Struts on a 701

A question for my learned fellow builders.  Should one replace the  round tube struts on a 701 with streamline struts can the jury struts be  eliminated?  If yes, why.  If no, why.  

 

  

Larry, www.SkyHawg.com,  N1345L   [quote][b]

zodierocket(at)hsfx.ca
Guest

Posted: Wed Oct 31, 2007 2:51 pm Post subject: Streamline Struts on a 701

Larry and others, I have designed a custom streamline extrusion for my float attachments and for the Struts of the STOL aircraft. I will be making Streamline Strut kits in the new year. The Jury struts will remain to remove any chance of wing harmonics( flexing). On average, this single step has improved cruise by 5 mph. The same can be achieved by simply wrapping the round struts with .016 and solid riveting the trailing edge. THE Magic # is 3-1 so for every inch in width add 3 inches in total length.  

     

Mark Townsend  

Can-Zac Aviation Ltd.  

president(at)can-zacaviation.com (president(at)can-zacaviation.com)  

www.can-zacaviation.com   

  

   

--

rjscep(at)yahoo.com
Guest

Posted: Wed Oct 31, 2007 3:53 pm Post subject: Streamline Struts on a 701

 	  Quote: 	
		   I was at Oshkosh and Michael said the same thing to

 me, wrap .016 and rivet the trailing edge...so thats

 what I will do......do not archive

--- ZodieRocket <zodierocket(at)hsfx.ca> wrote:
	




 	  Quote: 	
		   Larry and others, I have designed a custom

 streamline extrusion for my

 float attachments and for the Struts of the STOL

 aircraft. I will be

 making Streamline Strut kits in the new year. The

 Jury struts will

 remain to remove any chance of wing harmonics(

 flexing). On average,

 this single step has improved cruise by 5 mph. The

 same can be achieved

 by simply wrapping the round struts with .016 and

 solid riveting the

 trailing edge. THE Magic # is 3-1 so for every inch

 in width add 3

 inches in total length.

  

 Mark Townsend

 Can-Zac Aviation Ltd.

 HYPERLINK



"mailto:president(at)can-zacaviation.com"president(at)can-zacaviation.com
	


 	  Quote: 	
		   HYPERLINK



"http://www.can-zacaviation.com/"www.can-zacaviation.com
	


[quote] 

  

 --

lrm(at)skyhawg.com
Guest

Posted: Wed Oct 31, 2007 6:03 pm Post subject: Streamline Struts on a 701

I'm not so sure I agree that the jury struts are  needed if streamline struts are used.  My PegaStol wings only have  streamline struts as does the Savannah.  Most wings that have streamline  struts do not employ jury struts.  I know some highwings do use both  streamline and jury struts, but it is not the general  rule.  Perhaps jury struts are only needed to stabilize the harmonics  set up with round tubing whereas streamline struts do not cause any such  harmonics or vibration.   Having now built both the Zenith wing and  PegaStol wing I don't think the Zenith wings have a structure need for the jury  struts, they simply keep the tubes from humming and add unneeded weight and  drag.  Larry

 [quote]   ---

NYTerminat(at)aol.com
Guest

Posted: Wed Oct 31, 2007 6:20 pm Post subject: Streamline Struts on a 701

In a message dated 10/31/2007 10:04:50 P.M. Eastern Daylight Time,  lrm(at)skyhawg.com writes:

  	  Quote: 	
		  Having now built both the Zenith wing and PegaStol wing I    don't think the Zenith wings have a structure need for the jury struts, they    simply keep the tubes from humming and add unneeded weight and drag.     Larry 	


 

 Larry,

  

 I can't remember where I read it but I believe the jury  struts keep it from humming as you said and also in a negative G condition they  keep the struts from bending. I have seen many ultralights that have removed  their tube struts and jury struts and replaced with only aluminum streamline  struts. I put on the plastic streamline struts over the tube struts and saw an  8mph increase along with having to repitch the prop to keep from over revving.  Could not believe how much drag is caused by those tube struts.

  

 Bob Spudis

 N701ZX/ CH701/

 140hrs



  [quote][b]

zodierocket(at)hsfx.ca
Guest

Posted: Wed Oct 31, 2007 6:21 pm Post subject: Streamline Struts on a 701

In my unprofessional opinion I believe you are right and maybe for my type of flying they are not needed. However, they are little weight gain and provide far more strength then you give them credit for, and with that extra strength It may cover that fellow out there who fly’s a lot differently then either you or I do. I will leave the Jury Strut decision to Chris Heintz. After all he knows a lot more then either of us concerning the 701.   

   

Plus all the Savanna’s I have seen did add the jury strut after that one had an in-flight failure. It is one of there improvements.  

   

     

Mark Townsend  

Can-Zac Aviation Ltd.  

president(at)can-zacaviation.com (president(at)can-zacaviation.com)  

www.can-zacaviation.com   

  

   

--

planecrazydld(at)yahoo.co
Guest

Posted: Wed Oct 31, 2007 6:52 pm Post subject: Streamline Struts on a 701

Doesn't anyone out there understand that the purpose of the jury strut is to stabilize the wing strut in buckling? During any intentional or unintentional negative G excursions, the strut wants to bend/buckle. The jury strut (while usually pretty flimsy) effectively holds that instability off to a MUCH greater load.



 Even if the design does not require them, they are desirable for that reason alone.

  

  Dave Downey

 Harleysville (SE) PA

 100 HP Corvair



 



 ---

grs-pms(at)comcast.net
Guest

Posted: Wed Oct 31, 2007 9:11 pm Post subject: Streamline Struts on a 701

Dave:

  

 Speaking as a (retired) aeronautical engineer, I  second your comments, though I take some exception to your last sentence.   Given that Chris Heintz is a professional designer, I'm sure the 701  does require the jury struts.  Otherwise he wouldn't have accepted the  complexity, weight, drag and cost.  The alternative would have been a  larger diameter or heavier-walled strut to get the same resistance to buckling  under a compression load.  It is not a question of vibration nor some  property of streamline tubing as such.   The fact that some other  design doesn't employ jury struts means that the other designer has chosen a  different solution to providing the necessary compression strength.

  

 If the increase in cruise speed seems worth the  effort a streamline fairing for the strut seems a good solution.

  

 George Swinford.

 [quote]   ---

planecrazydld(at)yahoo.co
Guest

Posted: Thu Nov 01, 2007 2:51 am Post subject: Streamline Struts on a 701

Hi George;

  

 The basis for the last comment was the (almost) loss of a Waco UPF-7 that I rebuilt from 3 hangars full of parts about 25 years ago. On the first flight, the driving strut between the ailerons on the right hand side (had a very minor arch - less than 1/4" in almost 6 feet of length) went unstable and started fluttering. As it turned out, it neded to be perfectly straight to work without risk. A very small stabilizing force at mid length would have precluded that phenomenon.



 My apologies to all who read offense into the comment posted. It was not meant the way that even I read it when it showed up!

  

 Dave Downey

  Harleysville (SE) PA

 100 HP Corvair



 



 ---

lrm(at)skyhawg.com
Guest

Posted: Thu Nov 01, 2007 5:53 am Post subject: Streamline Struts on a 701

I pretty much agree with leaving the struts on,  mainly because I am not sure enough to risk removing them.  However, I will  make one comment.  The 701 strut design is a matter of ease and less  expensive than real streamline struts.  That is the sole reason tubing is  used.  One must also remember that the 701 is developed to be what it is,  low and slow.  It was never intended to have a fast cruise, that's our  wish.  It's design functions were accomplished and that is where Chris  quit.  Larry

 [quote]   ---

grs-pms(at)comcast.net
Guest

Posted: Thu Nov 01, 2007 8:42 am Post subject: Streamline Struts on a 701

Dave: 

  

 Certainly no offense taken on my  part.  I was waiting for someone to point out the purpose of the  jury strut.  As you note, it only takes a little eccentricity to make a  structural column unstable.  In the case of the Waco. the fact that the  strut was part of the aileron system rather than being a fixed member  made it more susceptible to vibration.

  

 George

  

 Do not archive

  

 [quote]   ---

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