Matronics Email Lists :: View topic - Shock cords -- FWIW (triv)

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Shock cords -- FWIW (triv)
Goto page 1, 2 Next

Matronics Email Lists Forum Index -> Kitfox-List

View previous topic :: View next topic

Author Message

Fox5flyer
Guest

Posted: Mon Dec 31, 2007 12:11 pm Post subject: Shock cords -- FWIW (triv)

My model II/582 had bungee gear and I never  understood what all the fuss was about.  It landed straight and I changed  out two sets of shock cords over 4 years (3 counting orig), spending perhaps a  couple hours on each set (I made my own).  I put just under 400 hours on it  and I was always amazed at how resilient the system was.  Never had a  problem.  I now have a S5 and with nearly 400 hours on spring gear which is  also nice, but it came with the package so I was kinda stuck with it.  I do  remember that during building I weighed the entire spring gear assembly with  wheels and tires and it came to about 75 lbs.  I don't know how that  compares with the bungee gear, but it sure seemed heavy.  Then again, it  has held up quite well on my farm strip.  

 For all you bungee gear users, here's what Dan  Denny had to say about shock cords.

 Deke Morisse

Mikado Michigan

S5/Subaru/CAP  355+ TT

"Nothing will ever be attempted, if all possible objections must  first be overcome".- Samuel Johnson

  

  

 "SUBJECT: Shock  Cords



TO:       KitfoxT Model III & IV  Builders



FROM:       Denney Aerocraft  Company



Dear KitfoxT Builders,



Over the course of the past several  months, good quality shock cord has been

increasingly difficult to obtain.  The shock cords (LSC-19) included in your

landing gear kit may be fabricated  of one of three different types of bungee

material.



Some of this  material is of smaller diameter than the original stock. You

may have to take  more wraps than indicated by the instructions, Step (22)

and Figure  LGH-6.



The original material is .41" diameter and color coded with two  rows of

black threads and one of red. Install it according to the manual  (six

wraps).



The smaller cord is about .33" diameter and marked with 3  rows of green

threads. You will have to take about eight wraps. It seems to  be good

quality bungee material and should work just as well as the  original.



For a time we sent bungee material that has proven to be of  inferior

quality. It is about 7/16" (.41") diameter and marked by paired  bands of red

and green. These shock cords do not last at all. Return them to  the factory

and we will be happy to replace them with the better - quality  cords as soon

as possible.



Happy building



Dan  Denney



[url=]rexjan(at)bigpond.com[/url]



   [quote][b]

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Mon Dec 31, 2007 12:42 pm Post subject: Re: Shock cords -- FWIW (triv)

Deke, 



Attached is a pic of mine with well over 700 hours on them.

Look like RED RED Yellow ? 



Next pic will show mine  that are not tight to stops.

I agree--  whazzzzzzzzza all da fuss about ? 

Use what works and is proven.

dec31 016.jpg

Description:

Daves Kitfox Bungees well over 700 hours !!!!!!

Filesize:

634.64 KB

Viewed:

603 Time(s)

_________________
Realtime Kitfox movies to separate the internet chatter from the truth
http://www.youtube.com/user/kitfoxflyer
Hundreds of Kitfox Movies
Most viewed Kitfox on youtube
Most popular on youtube
Highest rated on youtube

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Mon Dec 31, 2007 12:43 pm Post subject: Re: Shock cords -- FWIW (triv)

Here is pic of Gear not touching stops .



Seems ok  so far ,,,,,,,,,,

dec31 014.jpg

Description:

Landing gear stops

Filesize:

457.76 KB

Viewed:

617 Time(s)

Fox5flyer
Guest

Posted: Mon Dec 31, 2007 1:51 pm Post subject: Shock cords -- FWIW (triv)

I think if you want perfection they should be right to the stops, but a 

little sag doesn't hurt anything, in my opinion.  I notice you use the 

safety cables.  Many years ago there was a long thread on this subject. 

There were reports of some members who made hard landings, hard enough so 

that the safety cables maxed out and bent the lateral bulkhead that the 

cables are wrapped around.  There may still be pics on Sportflight.com 

somewhere.  If I recall correctly, Skystar published a bulletin recommending 

that safety cables not be used for this reason.  It's rare for a bungee to 

break anyway.

Deke Morisse

Mikado Michigan

S5/Subaru/CAP 355+ TT

"Nothing will ever be attempted, if all possible objections must first be 

overcome".- Samuel Johnson

 	  Quote: 	
		  

 Here is pic of Gear not touching stops .



 Seems ok  so far ,,,,,,,,,,

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Wed Jan 02, 2008 3:30 am Post subject: Re: Shock cords -- FWIW (triv)

 	  Quote: 	
		  I think if you want perfection they should be right to the stops, but a 

little sag doesn't hurt anything, in my opinion. I notice you use the 

safety cables. Many years ago there was a long thread on this subject. 

There were reports of some members who made hard landings, hard enough so 

that the safety cables maxed out and bent the lateral bulkhead that the 

cables are wrapped around. 	


Deke, thanks.   Yes I agree tighter might be optimum but like i said i have the last 2 seasons flying with one less wrap and not tight against the stops.   Perhaps this has helped the bungees last longer as well?  I do have on with the outer jacket frayed but strands seem intact  so far. 



Bending the tubes would not be nice but would be the lesser of evils then smacking prop and bending a gearbox or crank and/or more damage to wingtips,gear etc.   



Man you would have to hit hard to bust a cable like that .

Fox5flyer
Guest

Posted: Wed Jan 02, 2008 5:03 am Post subject: Shock cords -- FWIW (triv)

That's exactly the problem.  The cables don't break so something has to 

give.

Deke



 	  Quote: 	
		  

> I think if you want perfection they should be right to the stops, but a

> little sag doesn't hurt anything, in my opinion. I notice you use the

> safety cables. Many years ago there was a long thread on this subject.

> There were reports of some members who made hard landings, hard enough so

> that the safety cables maxed out and bent the lateral bulkhead that the

> cables are wrapped around.



 Deke, thanks.   Yes I agree tighter might be optimum but like i said i 

 have the last 2 seasons flying with one less wrap and not tight against 

 the stops.   Perhaps this has helped the bungees last longer as well?  I 

 do have on with the outer jacket frayed but strands seem intact  so far.



 Bending the tubes would not be nice but would be the lesser of evils then 

 smacking prop and bending a gearbox or crank and/or more damage to 

 wingtips,gear etc.



 Man you would have to hit hard to bust a cable like that .



 --------

 Rotax Dealer, Ontario Canada

 Flying Videos and Kitfox Info

 http://www.cfisher.com/





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=155502#155502

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Wed Jan 02, 2008 6:09 am Post subject: Re: Shock cords -- FWIW (triv) More cable talk

 	  Quote: 	
		  That's exactly the problem. The cables don't break so something has to 

give. 

Deke 

	




So are you saying the cables should break? I would that in the event of bungee failure the cable would arrest the gear from total collapse and potentially saving a prop strike and possibly more. 

I will add that I have 1/8" cable attached to engine in 2 places ,routed through the firewall, and looped around the fuselage aft of the firewall in the event of a prop failure where you could lose the engine and would lose control.  In this case again the cable would save you again from more damage but at the cost of possibly denting,collapsing or destroying fuselage tubing.

lcfitt(at)sbcglobal.net
Guest

Posted: Wed Jan 02, 2008 9:36 am Post subject: Shock cords -- FWIW (triv)

Dave,



I don't think you got Deke's point.  There have in fact been guys that had 

to trailer their Model IVs to the Skystar factory for replacement of the 

bulkhead the bungees wrap around because of a hard landing caught by the 

limit cables which essentially destroyed the bulkhead.  Securing the 

engine - smart move, but securing the landing gear - very questionable move, 

in my opinion and Skyster corrected their design error.



I guess it is up to the individual what he would prefer replacing - the prop 

and possibly the gear box (crank) on his engine or the bulkhead weldment 

with all the fabric repair, paint, etc.  Believe it or not, the damage 

incidents are factual rather than the typical argued opinions so very common 

on aviation forums.



I don't know if these reports still appear in the available archives, (When 

I last checked, I couldn't find anything prior to the turn of the century) 

but these reports were the real reason I went to the Hammerhead gear. 

Consider Hammerhead and Grove, the same way we consider Kitfox and Avid, 

however in this case it was Hammerhead that went south first.



Lowell



---

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Wed Jan 02, 2008 6:31 pm Post subject: Re: Shock cords -- FWIW (triv)

Lowell, 



I am still wondering why you are suggesting no safety cable on the bungee gear?  There are there for a reason to arrest the gear in the event  of a bungee failure. Without it alot of damage could occur.  If there was a safety bulletin that I missed please post it. 



If the reason to not use them is to not bend a cross member in the event of a hard landing then i would suggest some one better learn to land better.  You are talking some serious G's here to do that kind of damage. Possibly close to what you experienced in your accident. 



I would highly recommend that you talk to your Kitfox supplier to see if it is advisable to not use safety cables   -- they are there for a reason.  



Next point -- is it possible that the cable in the cases you mention where never properly installed and possibly too long or short of a loop  that caused this damage? 



The bungee suspension could be made stronger and eliminate the Bungees by using a compression spring type suspension , but you would end up like the Grove or Hammerhead  gear with extra weight that was not necessary.   Goes back to the Keep it simple theory.  How does formula go?    For every pound of weight you add to your plane you will lose  3 to 4 FPM of climb rate. 

Speaking of bent tubing -- I would rather see Bent 4130 tubing then cracked or broken tubing that was too brittle.

MichaelGibbs(at)cox.net
Guest

Posted: Wed Jan 02, 2008 8:00 pm Post subject: Shock cords -- FWIW (triv)

Dave sez:



 	  Quote: 	
		  If the reason to not use [safety cables on the gear] is to not bend 

a cross member in the event of a hard landing then i would suggest 

some one better learn to land better.  You are talking some serious 

G's here to do that kind of damage. Possibly close to what you 

experienced in your accident.


	


Actually, it doesn't take all that many gs.  There have been several 

cases of moderately hard landings stretching the bungees far enough 

for the safety cables to put an excessive load on the truss and 

collapsed it.



Rather than remove the cables I decided to use the Grove gear to 

avoid the problem.



Mike G.

N728KF

Phoenix, AZ

lcfitt(at)sbcglobal.net
Guest

Posted: Wed Jan 02, 2008 8:38 pm Post subject: Shock cords -- FWIW (triv)

Dave,



Good question.  What I am suggesting is that people consider the possible 

outcomes of the various scenerios.  As you recall, I chose the heavy spring 

gear rather than a more cost effestive pair or dikes in my right hand. 

When I build again I will likely use tube gear for weight issues, and due to 

the destroyed bulkhead will not install the limit cables - my choice.  But 

then none of my friends flying with bungee gear have limit cables.  And then 

again, that is a personal preference.  But their choice was based on the 

possible structural damage with a hard landing.



Now a question for you.  With properly maintained bungees, what is the 

greater likelyhood, a broken bungee, or a messed up landing.  Realizing that 

there are different levels of proficiency, one has to consider all sides of 

the issue, which is only what I propose.   But consider the poor goofballs 

like Mark or Wray who might ding their airplanes at any moment with a hard 

landing.  Mark has nearly 2000 hours in three models of Kitfoxes and Wray 

has 3000 hours in DC-3s and 1000 in his Fox, not to mention the Storches and 

Learjets - just kidding.  Neither have limit cables for the mentioned reason 

and we have talked about it many times.  They just change out the bungees in 

a timely manner.  Did I mention off airport landings - tons and lots of 

first timers too.



I just thought of another question.  Has anyone ever heard of bungees 

breaking and the gear hanging on the limit cables or damaging a prop?  The 

Mil Spec for 3/8" bungees is a minimum breaking force of 300 lbs. Multiply 

that by 7 wraps and that's some serious Gs as well for gear legs that 

supports between 275 and 400 lbs each.



I searched the Service Bulletins and there is nothing, as you found.  There 

is, interestingly, nothing on the recommended frequency of bungee 

replacemtent either - whatever that means.



Again, I have to say.  I have no personal interest in what people do with 

their airplanes.  For some reason, I find it difficult to sit on my hands 

when I know of experiences that others have had that might shed a bit of 

light on an issue.



Question the Kitfox supplier - good idea.  Best to make a decision after all 

the info is in.



Improper installation.  Who knows, but the one that most easily comes to 

mind - a good friend, we used to room together at the Skystar Fly-ins and I 

remember all the details.  He was showing off at a local fly-in event at a 

private one way strip.  He was nicknamed Dr. Downhill after that. He was an 

engineer by profession.  Who was that man 



Lowell



---

l.morris(at)tx.rr.com
Guest

Posted: Thu Jan 03, 2008 8:21 am Post subject: Shock cords -- FWIW (triv)

Lowell, Are you trying to say that my bungee chords stored in a box in my attic since 1994 are no good?(LOL). Really, are there other bungee geared aiplanes out there that use limit cables?----- Leon Morris/Classic 4(94)/60%/like Jab/Flower Mound,TX

---- Lowell Fitt <lcfitt(at)sbcglobal.net> wrote: 

[quote] 

 

 Dave,

 

 Good question.  What I am suggesting is that people consider the possible 

 outcomes of the various scenerios.  As you recall, I chose the heavy spring 

 gear rather than a more cost effestive pair or dikes in my right hand. 

 When I build again I will likely use tube gear for weight issues, and due to 

 the destroyed bulkhead will not install the limit cables - my choice.  But 

 then none of my friends flying with bungee gear have limit cables.  And then 

 again, that is a personal preference.  But their choice was based on the 

 possible structural damage with a hard landing.

 

 Now a question for you.  With properly maintained bungees, what is the 

 greater likelyhood, a broken bungee, or a messed up landing.  Realizing that 

 there are different levels of proficiency, one has to consider all sides of 

 the issue, which is only what I propose.   But consider the poor goofballs 

 like Mark or Wray who might ding their airplanes at any moment with a hard 

 landing.  Mark has nearly 2000 hours in three models of Kitfoxes and Wray 

 has 3000 hours in DC-3s and 1000 in his Fox, not to mention the Storches and 

 Learjets - just kidding.  Neither have limit cables for the mentioned reason 

 and we have talked about it many times.  They just change out the bungees in 

 a timely manner.  Did I mention off airport landings - tons and lots of 

 first timers too.

 

 I just thought of another question.  Has anyone ever heard of bungees 

 breaking and the gear hanging on the limit cables or damaging a prop?  The 

 Mil Spec for 3/8" bungees is a minimum breaking force of 300 lbs. Multiply 

 that by 7 wraps and that's some serious Gs as well for gear legs that 

 supports between 275 and 400 lbs each.

 

 I searched the Service Bulletins and there is nothing, as you found.  There 

 is, interestingly, nothing on the recommended frequency of bungee 

 replacemtent either - whatever that means.

 

 Again, I have to say.  I have no personal interest in what people do with 

 their airplanes.  For some reason, I find it difficult to sit on my hands 

 when I know of experiences that others have had that might shed a bit of 

 light on an issue.

 

 Question the Kitfox supplier - good idea.  Best to make a decision after all 

 the info is in.

 

 Improper installation.  Who knows, but the one that most easily comes to 

 mind - a good friend, we used to room together at the Skystar Fly-ins and I 

 remember all the details.  He was showing off at a local fly-in event at a 

 private one way strip.  He was nicknamed Dr. Downhill after that. He was an 

 engineer by profession.  Who was that man 

 

 Lowell

 

 ---

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Thu Jan 03, 2008 10:38 am Post subject: Re: Shock cords -- FWIW (triv)

 	  Quote: 	
		  I searched the Service Bulletins and there is nothing, as you found. There 

is, interestingly, nothing on the recommended frequency of bungee 

replacemtent either - whatever that means. 	




Lowell same link i found on google say replace annually. 

http://kitfox.lazair.com/Service_Letters/sl48.htm



. The condition of the bungee should also be checked, and it should be replaced annually. 



I would really doubt that many Kitfoxes are not using safety cables .



How about a poll......... ?

Fox5flyer
Guest

Posted: Thu Jan 03, 2008 11:03 am Post subject: Shock cords -- FWIW (triv)

Dave, I suspect the bulletins and service letters at KitfoxAircraft are not 

complete which is not surprising considering all the commotion with the 

bankruptcy and picking up the pieces.  Somewhere are several photos of 

Kitfoxes with the center bulkhead destroyed by these cables when all that 

happened was a hard landing.  Nobody is trying to sway you into taking yours 

off.

Take a poll if you want, but it won't prove a thing and will just eat up 

unnecessary space and time.  If you like them there, then by all means keep 

them.  I was just pointing out that Skystar, after the damage, recommended 

they be removed.  However, those old manuals were probably never changed to 

reflect that.  I've been involved with Kitfoxes since about 1990 and I 

recall zero incidents of bungies actually breaking.  When I saw the photos I 

couldn't get those cables cut off there quick enough.  As for annually 

replacing the bungies, nothing new there either.  It's always been that way.

Deke Morisse

Mikado Michigan

S5/Subaru/CAP 355+ TT

"Nothing will ever be attempted, if all possible objections must first be 

overcome".- Samuel Johnson





 	  Quote: 	
		  

> I searched the Service Bulletins and there is nothing, as you found. 

> There

> is, interestingly, nothing on the recommended frequency of bungee

> replacemtent either - whatever that means.

 Lowell same link i found on google say replace annually.

 http://kitfox.lazair.com/Service_Letters/sl48.htm



 . The condition of the bungee should also be checked, and it should be 

 replaced annually.



 I would really doubt that many Kitfoxes are not using safety cables .



 How about a poll......... ?



 --------

 Rotax Dealer, Ontario Canada

 Flying Videos and Kitfox Info

 http://www.cfisher.com/





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=155761#155761

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Thu Jan 03, 2008 11:14 am Post subject: Re: Shock cords -- FWIW (triv)

To destroy the center bulkhead  you would need on hell of a hard landing. 



To tear the cables through the bulkhead you have ot ask your self what "could have " happened had the cables not been there ? 

I would not be in a hurry to remove mine or anyones. 



I have been around flying not just kitfox but GA to ultralight and homebuilts since 1980.



I would like to see these pictures and referance to remove them. 



How does one land thathard anyhow ?  Stall and drop straight in from 50 feet ?

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Thu Jan 03, 2008 11:42 am Post subject: Shock cords -- FWIW (triv)

On Jan 3, 2008, at 8:01 PM, fox5flyer wrote:

 	  Quote: 	
		    As for annually replacing the bungies, nothing new there either.  

 It's always been that way.


	


Er ... maybe, Deke. And, BTW, thanks Dave for the link to the service 

bulletin that I had never seen before.

I replaced my bungees last year after ... 13 years and about 950 

landings. I thought it was time although the one I removed were still 

in a splendid condition. Of course, I do inspect about everything on my 

plane, as a pre-flight and at any other occasion I am in the hangar and 

e.g. lift the cowling or just admire my bird. Inspection is never 

overdone but ... do we really have to change the bungees annually?



Cheers,

Michel Verheughe

Norway

Kitfox 3 - Jabiru 2200

_________________
Kitfox 3 - Jabiru 2200

Fox5flyer
Guest

Posted: Thu Jan 03, 2008 12:23 pm Post subject: Shock cords -- FWIW (triv)

Er...Michel, no you don't have to change them annually.  You change them 

whenever you want to.  I never recommended them be changed annually and I 

don't personally believe they need to be changed annually.  I was just 

making the point that "annually" was -- and unless it has been changed --  

the factory recommendation and it's been that way from when Denney had it. 

Somewhere there will be a reference to this or perhaps it's right in the 

older builder manuals.  I dunno.  I'm still looking for something that makes 

any reference at all to the bungies.  If I find it I'll pass it on. 

Otherwise, I'm moving on.

Deke Morisse

Mikado Michigan

S5/Subaru/CAP 355+ TT

"Nothing will ever be attempted, if all possible objections must first be 

overcome".- Samuel Johnson



---

msm_9949(at)yahoo.com
Guest

Posted: Thu Jan 03, 2008 1:00 pm Post subject: Shock cords -- FWIW (triv)

Michel,

   

  The original bungees in my plane came with the kit, delivered in 1989. Prior owner had only 4 wraps on them and I eventually squeezed 7 out of that set of rubberbands. But before the airplane ever flew (2005) I noticed slack had developed in the left bungee. Don't know if it was age (certainly wasn't wear) that caused stretching. Anyway I replaced with a set I made. A year later I replaced again tho old ones still looked fine. 

   

  Because the job is such a chore (at least for me) I've asked myself the same question, i.e., is replacement every year really necessary? Personally, I think not. So I'm going with every 2 years, tho I do check their condition routinely.

   

  P.S.: Back to old songs . . . Reading your description of North African adventure, I think I heard "Marakesh Express" playing in the background.



Michel Verheughe  <michel(at)online.no> wrote:

  [quote]--> Kitfox-List message posted by: Michel Verheughe 



On Jan 3, 2008, at 8:01 PM, fox5flyer wrote:

 	  Quote: 	
		   As for annually replacing the bungies, nothing new there either. 

 It's always been that way.


	


Er ... maybe, Deke. And, BTW, thanks Dave for the link to the service 

bulletin that I had never seen before.

I replaced my bungees last year after ... 13 years and about 950 

landings. I thought it was time although the one I removed were still 

in a splendid condition. Of course, I do inspect about everything on my 

plane, as a pre-flight and at any other occasion I am in the hangar and 

e.g. lift the cowling or just admire my bird. Inspection is never 

overdone but ... do we really have to change the bungees annually?



Cheers,

Michel  Menezes

Model 2 582 N99KX

  [quote][b]

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Thu Jan 03, 2008 1:11 pm Post subject: Shock cords -- FWIW (triv)

On Jan 3, 2008, at 9:22 PM, fox5flyer wrote:

 	  Quote: 	
		   I never recommended them be changed annually and I don't personally 

 believe they need to be changed annually.


	


Oh, I know Deke! I never implied that. I just wanted the group to know 

that, at least in my case, the bungees were still in good shape after 

13 years. You know, I have an art education; I know really nothing 

about mechanics. In my mind, anything that is made out of rubber or any 

other 'soft' stuff, has a limited life time. That's why I changed mine. 

But I think those little 'rubber bands' are good stuff and I am 

impressed. It makes me think that, after all, it is not a wonder that 

no bungee failure has been registered yet and that ... maybe removing 

the safety wire is a good idea. I still have mines but I'll be thinking 

about removing them.



Cheers,

Michel Verheughe

Norway

Kitfox 3 - Jabiru 2200

_________________
Kitfox 3 - Jabiru 2200

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Thu Jan 03, 2008 1:26 pm Post subject: Re: Shock cords -- FWIW (triv)

Michel read up a  a few posts ........of mine

 	  Quote: 	
		  Attached is a pic of mine with well over 700 hours on them. 

Look like RED RED Yellow ? 



Next pic will show mine that are not tight to stops. 

I agree-- whazzzzzzzzza all da fuss about ? 

Use what works and is proven.

Display posts from previous:

	Matronics Email Lists Forum Index -> Kitfox-List	All times are GMT - 8 Hours Goto page 1, 2 Next
Page 1 of 2

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum