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larry(at)macsmachine.com
Guest

Posted: Sat Dec 22, 2007 5:23 pm Post subject: Canopy Gas Struts (Springs)

Hi guys,

I received my gas struts only two days after ordering.  I bought the 40 

lb force type and replaced the old ones today.  I also took the old 

springs and tried pushing each down

on a scale to see what the extended 1/2-inch force was after 4 years.  I 

got 28 lbs on one and 30 lbs on the other.  The new springs are 40 lbs 

right on the money and they

hold the canopy up without any difficulty.  But for leakage over time, I 

still feel the 40 lb type is the way to go.



Larry McFarland  601HDS at www.macsmachine.com

robert stone wrote:

 	  Quote: 	
		        When you order the kit for the Zodiac601XL the 40# gas struts 

 will be included.  You might specifically request 60# struts when you 

 order the kit however I don't know if Zenith Aircraft even stocks the 

 stronger ones.  I would order direct from the McMaster-Carr Company, 

 Stock number for the 60# strut is 9416K123,  the company web site is: 

 http://www.mcmaster.com/



 Bob Stone

 Harker Heights, Tx

 ZodiacXL w/Jabiru 3300

 *



 *

s.c.richards(at)homecall.
Guest

Posted: Sun Dec 23, 2007 3:19 am Post subject: Canopy Gas Struts (Springs)

Larry

 I think you are correct in using the lower pressure struts If canopy was 

not latched correctly & opened in flight it may be impossible to reclose it 

if gas struts are too strong. I beleive someone in UK had this problem & had 

difficulity in maintaining level flight due to increased drag donot know 

what struts he used. We have used adjustable struts & let the pressure out 

(about 35lbs) so they just opened the canopy (of earlier design to XL) these 

have also leaked over time & need replacing or topping up, they still hold 

the canopy open after we lift it.

Merry Christmas

Clive

do not archive

---

dredmoody(at)cox.net
Guest

Posted: Sun Dec 23, 2007 7:03 am Post subject: Canopy Gas Struts (Springs)

I think something important has been left  out of the discussion regarding the strength of the gas charged struts or  their loss of strength over time. The geometry of the design for their  installation is such that the strut will only exert its rated force at the  point when the canopy is almost closed (the strut is fully compressed or nearly  so). Not coincidentally, that is also the point at which the canopy rail and  strut bracket have the best mechanical advantage in compressing the strut. In  other words, the only time the struts exert their full rated force, be that 40#  or 60# or whatever, is right when the full weight of the canopy is helping to  push down vertically with its greatest force and at it greatest leverage  advantage. The struts' force at that point is also linear (or nearly so) along  the long axis of the canopy rail so bending the rail to overcome that force is a  very remote possibility. 

  

 Conversely, the point at which the force of the  strut on the rail is lateral and at its greatest mechanical advantage against  the canopy rail is when the canopy is fully open and the first bit of closing  effort is made. If you test a new 40# stut versus a new 60# strut on a scale in  the first inch or so of compression you will find that the difference is not the  nominal 20# but only a fraction of that difference in force. The full 20#  difference won't be in play until you have almost closed the canopy and at that  point the mechanical advantage of the strut is so severely diminished that the  extra force required to finish closing the canopy will be almost unmeasurable.  

  

 I believe it is safe to use whichever strength of  strut you find necessary to prevent the canopy weight and/or a gust of wind from  slamming it down. Having the canopy go throught that event will very likely  cause injury to one of us or at the very least to the canopy itself. If it takes  a couple of extra pounds of force at the open position to accomplish that  margin of safety, I'm okay with that. I received the 40# struts with my kit and  I just bought a pair of 60# struts from McMaster-Carr. Not a very big investment  to secure the option to use them if and when I deem it necessary. My  installation was such that they can easily be changed at any point I need to.  The down side is that if I store them as backups, they will certainly lose  strength by the time I need them. That may actually work to my advantage in that  I may put them into service as 50# or maybe even 40# struts if and when I need  them.

  

 The incident reports regarding the 601XL canopy  popping open in flight are all in agreement that the canopy will only open a few  inches at most before the slipstream pressure prevents further opening. The  reports also agree that the aerodynamic lift (or some other unknown force)  effectively prevents closing it fully once it has lifted even that small amount.  That makes it clear that the "popping open" sort of incident will not be  affected one way or the other by the change of strut pressure.

  

 Bottom line: (A) make damn sure you have the canopy  securely closed as a part of your run-up checklist and use  it. And (B) use whatever strut strength is required  to make reasonably sure that your canopy won't slam down  unexpectedly.

  

 Sound reasonable? Merry Christmas all,

  

 Dred

   [quote][b]

purplemoon99(at)bellsouth
Guest

Posted: Sun Dec 23, 2007 9:10 am Post subject: Canopy Gas Struts (Springs)

Dred,I bought the70# and they work great,they make  the movement of the canopy more  solid and seems to remove alot of the left  and right slop at the rear of the canopy ,and my canopy is locking better than  it ever has,seems to open smoother with less effort there great.....  JoeN101HD601XL/RAM

 [quote]   ---

rstone4(at)hot.rr.com
Guest

Posted: Sun Dec 23, 2007 9:39 am Post subject: Canopy Gas Struts (Springs)

Ed,

      What you say  below makes much sense to me.  I completely eliminated the problem of the  canopy slamming shut by it's self by installing the 60# struts and the system  works fine now.

       I had the  canopy pop open in flight twice and so eliminated the Zenith design and  installed my own, the same one I used on a KR-2 that I built some years  ago.  Its a latch I can see and I have had no problems with my canopy since  making these two changes.  If any of you guys have had a canopy pop open in  flight you know it scares the hell out of you and if you would like to see my  new latching system, I will furnish pictures and an explanation upon  request.

 [quote]   ---

purplemoon99(at)bellsouth
Guest

Posted: Sun Dec 23, 2007 10:39 am Post subject: Canopy Gas Struts (Springs)

Bob, I've got a cross member across the rear  of  my canopy,I'am thinking about a light chain with a snap on it ,with  about 2" of slack to stop real radical pop open . Would like to see your set up  Thanks        Joe N101HD XL/RAM

 [quote]   ---

craig(at)craigandjean.com
Guest

Posted: Sun Dec 23, 2007 11:55 am Post subject: Canopy Gas Struts (Springs)

âž¢ The incident reports regarding the 601XL canopy popping open in flight are all in agreement that the canopy will only open a few inches at most before the slipstream pressure prevents further opening.



Actually I had a very different experience in a similar situation. I was flying left-seat with my instructor in an Evector SportStar. This plane is very similar to the 601XL: low-wing LSA with a forward hinged bubble canopy. One difference Is that the canopy is split behind the seats. There is a cross-bar behind the seats:



www.evektoramerica.com/SportStarPlus.htm



The canopy popped while we were in the pattern. I would estimate that the gap was well over a foot. While the instructor flew I tried to close the canopy. I wrapped my arm around the cross-bar and used all my weight and strength and could not close the canopy. At best I think I got the gap down to 6-8 inches. Evector redesigned the latch the next year.



I believe the upward force was generated by lift and not wind under the canopy as it did not decrease as I closed the gap.



-- Craig

dredmoody(at)cox.net
Guest

Posted: Sun Dec 23, 2007 12:03 pm Post subject: Canopy Gas Struts (Springs)

Thanks Bob, you already sent me the photos and I  pointed out that the hinge pin of that latch would be the weakest link to  watch. I am strongly considering something like what you did but as a redundant  measure..... sort of like that little cahin on a lady's bracelet, you  know?

  

 Merry Christmas,

  

 Ed

 [quote]   ---

larry(at)macsmachine.com
Guest

Posted: Sun Dec 23, 2007 12:05 pm Post subject: Canopy Gas Struts (Springs)

Joe,

I use a 1/16th x .75 nylon strap with plastic buckles to aluminum loops 

center of the rear bow to one between the seat backs.  It works fine, 

and it doesn't have

the hard shock value of a chain if it gets caught in a breeze. It's 

adjustable and doesn't get in the way up or down and doesn't weigh anything.

see links,

http://www.macsmachine.com/images/canopy/full/viewupperbracket.jpg

http://www.macsmachine.com/images/canopy/full/viewcanopyopen.jpg

http://www.macsmachine.com/images/canopy/full/viewupperbracket.jpg

I have had the canopy act as a sail with me setting on the wing and 

carry me slowly across the apron a

couple of times until it was lowered, so it's durable

rstone4(at)hot.rr.com
Guest

Posted: Sun Dec 23, 2007 1:07 pm Post subject: Canopy Gas Struts (Springs)

I have just  addressed this topic in an e-mail to the net.  More information to  follow.

  

 Bob Stone

 [quote]   ---

purplemoon99(at)bellsouth
Guest

Posted: Sun Dec 23, 2007 2:12 pm Post subject: Canopy Gas Struts (Springs)

Great idea Larry,Abetter mouse trap....Merry Xmas.     Joe N101HDXL/RAM

---

s.c.richards(at)homecall.
Guest

Posted: Mon Dec 24, 2007 9:42 am Post subject: Canopy Gas Struts (Springs)

Hi All

                  I am afraid the statement below is no longer correct, I

will attempt to attach a PDF scan my bit map scan is to large of an article 

from the UK PFA magazine for

November to which my previous reply referred. I had trouble in locating

origin of report when replying.    I will not test if this true unless by

accident.

Wishing you a Merry Christmas & trouble free flying

Clive



---

canopyopening.pdf

Description:

Download

Filename:

canopyopening.pdf

Filesize:

99.01 KB

Downloaded:

428 Time(s)

craig(at)craigandjean.com
Guest

Posted: Mon Dec 24, 2007 9:59 am Post subject: Canopy Gas Struts (Springs)

Thanks very much for the report. It sounds similar to what I experienced in the Evector.



A year or so ago someone mentioned having pictures or a video of a popped canopy on a 601. But they didn't want to post them so as to save embarrassing the pilot.



Guess I'll be using a block and tackle for my test. But I was planning to do it on the ground. If the test was done in the air I would suggest having someone in the right seat.



-- Craig



--

Tommy Walker

Joined: 12 Jan 2006
Posts: 442
Location: Anniston, AL 36207

Posted: Tue Dec 25, 2007 6:26 am Post subject: Re: Canopy Gas Struts (Springs)

Craig,



That compares with a situation the guy in the next hangar told me about. 



a guy with a 601 at my field told me this; he forgot to securely latch the canopy on the right side.  After takeoff, he noticed it due to the noise.  He attempted to pull the right side down and latch it securely.  This guy is about 6â€™ 4â€ and is a bear of a man.  He said he couldnâ€™t get it down, so he decided to loosen the left side so that he could level the canopy and then pull both sides down and close the latches.



Big Mistake.



He said the canopy immediately went to about 45 degrees and he entered a steep dive.  He was able to reduce power, level off and gain control over the airplane.  At full power, he was not able to climb, as the canopy acted like a speed brake.â€  At full power, he headed back to the airport at his present level and was able to land.  He said everything that was unsecured (insecured?) err, not secure, in the airplane departed, including extra headsets, gps, log books, etc.



Regards,



Tommy Walker in Alabama

N8701  18.5 hrs



P.S.  Please don't take this as criticism of the 601 design.  The PIC is responsible for making sure the canopy is secure before takeoff.



[quote="

www.evektoramerica.com/SportStarPlus.htm



The canopy popped while we were in the pattern. I would estimate that the gap was well over a foot. While the instructor flew I tried to close the canopy. I wrapped my arm around the cross-bar and used all my weight and strength and could not close the canopy. At best I think I got the gap down to 6-8 inches. Evector redesigned the latch the next year.



I believe the upward force was generated by lift and not wind under the canopy as it did not decrease as I closed the gap.



-- Craig[/quote]

_________________
Tommy Walker
N25A - Anniston, AL

Iberplanes

Joined: 10 Dec 2007
Posts: 174
Location: Igualada - Barcelona - Spain

Posted: Tue Dec 25, 2007 7:14 am Post subject: Canopy Gas Struts (Springs)

To all of you,



BSCL : BEFORE START CHECK LIST. That´s mandatory and have to include tha 

canopy latch check,



Happy new Year !!



---

_________________
Alberto Martin
601 XL - Jabiru 3300
http://www.iberplanes.es
Igualada - Barcelona - Spain

rstone4(at)hot.rr.com
Guest

Posted: Wed Dec 26, 2007 7:00 am Post subject: Canopy Gas Struts (Springs)

Tommy.

     You are right about one thing, the PIC is responsible for insuring that 

the canopy is latched prior to take off.  However the designer/producer of 

the aircraft in question is responsible for insuring that his design is safe 

and airworthy and with as many reports as I have seen on this forum about 

canopies opening in flight including my own, I think the design is flawed. 

Even though the aircraft is well built I had to glue strips of foam rubber 

on the bottom side of the rear seal to keep cold air out.  Also, this canopy 

is too heavy for the supplied 40# gas struts because before I installed the 

60# struts my canopy slammed down several times.  One time was at our last 

Young Eagles Flight Rally and a 10 year old boy got bonked on the head. 

That's when I decided to do something about the weak struts.



Bob Stone

Harker Heights, Tx

ZodiacXL w/Jabiru 3300



---

rsteele(at)rjsit.com
Guest

Posted: Wed Dec 26, 2007 9:38 am Post subject: Canopy Gas Struts (Springs)

I think it's worth pointing out that, in fact, even if the design is  

flawed, the designer of an experimental aircraft isn't responsible  

for the airplane, the builder is.  That's why it's an experimental.    

It's a responsibility that's all to easy to ignore for us kit  

builders, but it's the reality and something we shouldn't forget.    

Sounds like there needs to be a checklist item for these latches -  

another builder responsibility.



That said, I'm sure CH and everyone at Zenith is very serious about  

safety and if they felt there were issues they would be corrected.   

I'm guessing the issue with the struts is one of stress on the canopy  

when the struts are new (you don't want to stress the canopy while  

closing it) verses struts that weaken over time or are not up to  

snuff when new.

Perhaps we should all test the strut strength before installation.



This is the type of discussion that makes this list so valuable.  It  

must have been really lonely being a builder before the days of the  

internet.



Ron



On Dec 26, 2007, at 10:00 AM, robert stone wrote:



[quote] 



 Tommy.

     You are right about one thing, the PIC is responsible for  

 insuring that the canopy is latched prior to take off.  However the  

 designer/producer of the aircraft in question is responsible for  

 insuring that his design is safe and airworthy and with as many  

 reports as I have seen on this forum about canopies opening in  

 flight including my own, I think the design is flawed. Even though  

 the aircraft is well built I had to glue strips of foam rubber on  

 the bottom side of the rear seal to keep cold air out.  Also, this  

 canopy is too heavy for the supplied 40# gas struts because before  

 I installed the 60# struts my canopy slammed down several times.   

 One time was at our last Young Eagles Flight Rally and a 10 year  

 old boy got bonked on the head. That's when I decided to do  

 something about the weak struts.



 Bob Stone

 Harker Heights, Tx

 ZodiacXL w/Jabiru 3300



 ---

Tommy Walker

Joined: 12 Jan 2006
Posts: 442
Location: Anniston, AL 36207

Posted: Wed Dec 26, 2007 1:52 pm Post subject: Re: Canopy Gas Struts (Springs)

Thanks,



The point I was trying to make (and doing a poor job) was that based upon my neighbor's experience, you can't close the cowl if it pops open after takeoff.  



Plus I added the Caveat lector, "let the reader beware" about design and checklist...



I've never been in a 601 and I guess I should keep my mouth shut.







Tommy Walker in Alabama

N8701



Do Not Archive

[quote="rsteele(at)rjsit.com"]I think it's worth pointing out that, in fact, even if the design is  flawed, the designer of an experimental aircraft isn't responsible  for the airplane, the builder is.  That's why it's an experimental. It's a responsibility that's all to easy to ignore for us kit  

builders, but it's the reality and something we shouldn't forget.    

Sounds like there needs to be a checklist item for these latches -  

another builder responsibility.

Perhaps we should all test the strut strength before installation.



This is the type of discussion that makes this list so valuable.  It  

must have been really lonely being a builder before the days of the  

internet.



Ron



On Dec 26, 2007, at 10:00 AM, robert stone wrote:



 	  Quote: 	
		   



 Tommy.

     You are right about one thing, the PIC is responsible for  

 insuring that the canopy is latched prior to take off.  However the  

 designer/producer of the aircraft in question is responsible for  

 insuring that his design is safe and airworthy and with as many  

 reports as I have seen on this forum about canopies opening in  

 Bob Stone

 Harker Heights, Tx

 ZodiacXL w/Jabiru 3300



 ---

_________________
Tommy Walker
N25A - Anniston, AL

ggower_99(at)yahoo.com
Guest

Posted: Wed Jan 02, 2008 4:10 pm Post subject: Canopy Gas Struts (Springs)

I am now building a 601 XL,   Not yet in the canopy area...  But one thing is important in any airplane:    Doesnt matter how overbuilt or extra safety is any canopy or  door lock of any airplane,  will fail if the pilot will not follow the checklists in every one of the points.   

   

  Also lets remember that only the wiser men can design simple and light.   

  Any one can desing a complicate and heavy what ever, just need to keep "thinking"  and adding ideas  

   

  Now back...  We all have to go through every check list routine the same every time,  from beguining to end,  never forget or skip any point....  All are so important that our life might depend on them.  

   

  Saludos 

  Gary Gower

  Flying from Chapala,  Mexico.

  



Tommy Walker <twalker(at)cableone.net> wrote:

   	  Quote: 	
		  --> Zenith-List message posted by: "Tommy Walker" 



Thanks,



The point I was trying to make (and doing a poor job) was that based upon my neighbor's experience, you can't close the cowl if it pops open after takeoff. 



Plus I added the Caveat lector, "let the reader beware" about design and checklist...



I've never been in a 601 and I guess I should keep my mouth shut.







Tommy Walker in Alabama

N8701



Do Not Archive

[quote="rsteele(at)rjsit.com"]I think it's worth pointing out that, in fact, even if the design is flawed, the designer of an experimental aircraft isn't responsible for the airplane, the builder is. That's why it's an experimental. It's a responsibility that's all to easy to ignore  for us kit 

builders, but it's the reality and something we shouldn't forget. 

Sounds like there needs to be a checklist item for these latches - 

another builder responsibility.

Perhaps we should all test the strut strength before installation.



This is the type of discussion that makes this list so valuable. It 

must have been really lonely being a builder before the days of the 

internet.



Ron



On Dec 26, 2007, at 10:00 AM, robert stone wrote:

 	  Quote: 	
		   

 

 Tommy.

 You are right about one thing, the PIC is responsible for 

 insuring that the canopy is latched prior to take off. However the 

 designer/producer of the aircraft in question is responsible for 

 insuring that his design is safe and airworthy and with as many 

 reports as I have seen on this forum about canopies opening in 

 Bob Stone

 Harker Heights, Tx

 ZodiacXL w/Jabiru 3300

  

 ---


	




--------

Tommy Walker





	


        Be a better friend, newshound, and  [quote][b]

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