Bungee Life

[Guest]

In the last year I have been going thru bungees like crazy in the last year.

I put cords on 1/07 and replaced them 4/07 and now I need to replace that set and will address that this week.

On average my cords had been lasting for 3 or 4 years.

I have consistently been using Superior/SBC cords.

Anyone else experiencing short cord life in the past year or so?

Actually I think I'll just add a third cord this week to see if that takes care of it and I got these new cords from Aircraft Spruce & Specialty and they appear to be a different brand.

Dave

[Jim Hartley]

Re: Bungee Life

Hi Dave,
What is happening with the cords? Stretching out or breaking?

Jim

[Dick Smith]

Re: Bungee Life

Dave, I recently posted the following...somewhat along the same line of thought:

I'm running 2 bungees on each side...each pair consisting of one 9010 and one 1010 .... Paid right at 80 bucks apiece for the 1010, in Anchorage. I see Univair has the 1010 listed per the following link:

http://univairparts.com/shopping_291765/product_info.php?cPath=107_132&products_id=27735

When I got the bill for 160 bucks for two 1010's, I called Reeves and asked if they double-billed me accidently...The response: "Nope...That's what they cost...and the lifetime of the bungees has gone down to boot". They had some older bungees priced at what I was used to, but they said the last order that they had received had given them sticker shock also. My understanding was that Superior is using a synthetic material, rather than natural rubber, hence a difference in longevity.
Anyhow, I really like the resulting stiffness of the gear...which when coupled with the "give" in the 8.50 X 6.00 tires, gives just the right "feel".
It appears that something may have changed in the makeup of the current output from Superior. Dick

[PT13Pilot]

Re: Bungee Life

Dave,
Funny you should post this, made me think working today. I'm working on the T-Craft I rebuilt the wings on last year. It's also the one I put cords on this February, using your tool. The thing has 22 hours since I changed them and I noticed after I flew it down to my hangar, that when I pushed it in, the brace struts were off the stops just sitting there. Gave it a rock and the gear moved pretty easily just sitting there. They look ok, but seem to be quite soft, and it's cold here. Kind of wondering how long they're gonna last at this rate. I put 9010's on from Spruce if memory serves.
Although after the L-2 bungee horror you helped me out with, I'm just glad to see cords with give!
Chris

[PT13Pilot]

Re: Bungee Life

Dave,
Just looked at my logbook entries and files. They were 9010HD's from Spruce. And they look good, and aren't covered with oil or anything to degrade them any quicker.

[Guest]

Re: Bungee Life

Hi Dave,
What is happening with the cords? Stretching out or breaking?

Jim

Hi Jim, stretching so that the center of the gear where the bungee attaches sags down about an inch.

Dave

[Guest]

Re: Bungee Life

Dave, I recently posted the following...somewhat along the same line of thought:

I'm running 2 bungees on each side...each pair consisting of one 9010 and one 1010 .... Paid right at 80 bucks apiece for the 1010, in Anchorage. I see Univair has the 1010 listed per the following link:

http://univairparts.com/shopping_291765/product_info.php?cPath=107_132&products_id=27735

When I got the bill for 160 bucks for two 1010's, I called Reeves and asked if they double-billed me accidently...The response: "Nope...That's what they cost...and the lifetime of the bungees has gone down to boot". They had some older bungees priced at what I was used to, but they said the last order that they had received had given them sticker shock also. My understanding was that Superior is using a synthetic material, rather than natural rubber, hence a difference in longevity.
Anyhow, I really like the resulting stiffness of the gear...which when coupled with the "give" in the 8.50 X 6.00 tires, gives just the right "feel".
It appears that something may have changed in the makeup of the current output from Superior. Dick

Hi Dick,

So here's a dumb question; what is the diff between 1010's and 9010's? same cord size? same loop size?

Sounds like longevity is going to about the same

Dave

[Dick Smith]

Re: Bungee Life

Dave, the 9010 is 9/16 inch diameter (cross section) and 10 inches inside diameter of the ring. The 1010 is 5/8 inch diameter (ie., 10/16 ") and 10 inches inside diameter. Just larger cross section and harder to stretch. Dick

[Forrest Barber]

Re: Bungee Life

I have calls in to Superior and will try to get answers, where they are stored prior to application can make go bad real quick, heat, ozone ( compressor nearby) , etc..

[high time cub]

Re: Bungee Life

In the last year I have been going thru bungees like crazy in the last year.
On average my cords had been lasting for 3 or 4 years.
Dave

Hi Dave,

As you know it's raining in the Hudson Valley today.... so enjoy the indoor "links"

Maybe a change in crosslink chemistry?

http://www.scienceblog.com/community...199800040.html (chemical engineering)

This may seem like a stretch, or a long shot, but it's possible that the bungee longevity problem might be tied to recent changes in golf ball manufacture (big market).

For a long time, most golf balls used rubber thread wound around a center core (three piece construction). A percentage of newer ones eliminate the rubber thread.

Stick with me.....

In the parallel universe, most FAI (Fédération Aéronautique Internationale) competition indoor free-flight models used FAI Tan 2 rubber (a synthetic / natural formula), until it went out of production in 2002.
Serious competitors hoarded their dwindling stock in the freezer. Rumor had it that Tan 2 production stopped because the major golf ball market disappeared.

The niche market of antique airplane bungees may no longer be supported by the rubber manufacturers.... we may be stuck in the sand trap.

H.T.


From Oct. 2001
Author : [email protected]

Dear FAI Customer,

We are currently out of good 1/8", 3/16", and 1/4" contest rubber. We
do have some 3/32" and 1/16" that are good.
Due to the collapse of the rubber thread business for golf balls, we
currently have two factories downsizing into one factory at a new location.
The net result is that the next production lot will not be available until
approximately November 30th. This order will be for 1/8" only, and if it meets
specs, the other sizes will be available at the end of the year, or
early in January 2002.
Good News: Our same Tan II Q/C and sales management team will be in
place at the new location.
Bad News: Due to the lower demand for a critical synthetic additive
( golf ball related ), we can expect a noticeable increase in cost of Tan II.
Our factory or we do not know the amount of this increase at this time.

John

http://www.aeromodel.com/TM/E27253T261

http://www.maxconrad.com/stufffour.htm (scroll down to rubber issues)

http://www.imprintgolf.com/golfballselectionpage.htm

.....and the future market.... nano/ green!

http://www.wilson.com/wilson/staff/product2.jsp?CONTENT%3C%3Ecnt_id=10134198673951444&FOLDER%3C%3Efolder_id=9852723697224056&bmUID=1197660195345

http://www.supercub.org/phpbb2/viewtopic.php?t=12452&highlight=bungee

[VictorBravo]

Re: Bungee Life

Unfortunately I think Tan 2 has gone out of production... although I don't fly much rubber these days ( I haven't been free-flighting for over a year because of screwing around with the T-craft) , I hear from some of the guys that there are new compounds out... Sig makes something called "sport" rubber because it no longer meets their old "Sig Contest Rubber" standards. Have you heard that FAI has an alternative rubber yet? Years ago Pirelli tire company made contest rubber for models, but I think that's long gone.

On another bungee note... I put brand new bungees on my airplane 6 months ago but they still sag in the middle. My tires are worn on the inside edges and the airplane looks like it has not seen new bungees in 20 years. I think I might have used the wrong bungee. I used 9010HD on a pre-war airplane... now I seem to remember something that the pre-war's used a 9090 instead of a 9010? If I made that mistake, I have bungees that are too long???

Can anyone in the know shed some light on this one for me?

Bill

[Guest]

Re: Bungee Life

Unfortunately I think Tan 2 has gone out of production... although I don't fly much rubber these days ( I haven't been free-flighting for over a year because of screwing around with the T-craft) , I hear from some of the guys that there are new compounds out... Sig makes something called "sport" rubber because it no longer meets their old "Sig Contest Rubber" standards. Have you heard that FAI has an alternative rubber yet? Years ago Pirelli tire company made contest rubber for models, but I think that's long gone.

On another bungee note... I put brand new bungees on my airplane 6 months ago but they still sag in the middle. My tires are worn on the inside edges and the airplane looks like it has not seen new bungees in 20 years. I think I might have used the wrong bungee. I used 9010HD on a pre-war airplane... now I seem to remember something that the pre-war's used a 9090 instead of a 9010? If I made that mistake, I have bungees that are too long???

Can anyone in the know shed some light on this one for me?

Bill

Hi Bill, read farther up the thread to see Dick Smith's explanation, sounds like yours are 1" too big.

Dave

[Guest]

Re: Bungee Life

Hi Dave,

As you know it's raining in the Hudson Valley today.... so enjoy the indoor "links"

Maybe a change in crosslink chemistry?

http://www.scienceblog.com/community...199800040.html (chemical engineering)

This may seem like a stretch, or a long shot, but it's possible that the bungee longevity problem might be tied to recent changes in golf ball manufacture (big market).

For a long time, most golf balls used rubber thread wound around a center core (three piece construction). A percentage of newer ones eliminate the rubber thread.

Stick with me.....

In the parallel universe, most FAI (Fédération Aéronautique Internationale) competition indoor free-flight models used FAI Tan 2 rubber (a synthetic / natural formula), until it went out of production in 2002.
Serious competitors hoarded their dwindling stock in the freezer. Rumor had it that Tan 2 production stopped because the major golf ball market disappeared.

The niche market of antique airplane bungees may no longer be supported by the rubber manufacturers.... we may be stuck in the sand trap.

H.T.


From Oct. 2001
Author : [email protected]

Dear FAI Customer,

We are currently out of good 1/8", 3/16", and 1/4" contest rubber. We
do have some 3/32" and 1/16" that are good.
Due to the collapse of the rubber thread business for golf balls, we
currently have two factories downsizing into one factory at a new location.
The net result is that the next production lot will not be available until
approximately November 30th. This order will be for 1/8" only, and if it meets
specs, the other sizes will be available at the end of the year, or
early in January 2002.
Good News: Our same Tan II Q/C and sales management team will be in
place at the new location.
Bad News: Due to the lower demand for a critical synthetic additive
( golf ball related ), we can expect a noticeable increase in cost of Tan II.
Our factory or we do not know the amount of this increase at this time.

John

http://www.aeromodel.com/TM/E27253T261

http://www.maxconrad.com/stufffour.htm (scroll down to rubber issues)

http://www.imprintgolf.com/golfballselectionpage.htm

.....and the future market.... nano/ green!

http://www.wilson.com/wilson/staff/product2.jsp?CONTENT%3C%3Ecnt_id=10134198673951444&FOLDER%3C%3Efolder_id=9852723697224056&bmUID=1197660195345

http://www.supercub.org/phpbb2/viewt...ghlight=bungee

Hi Jim, thanks.

Interesting, oddly I have called SBC a few times but answer, will try again now.

Dave

[Forrest Barber]

Re: Bungee Life

Hmmmm seems Bill is one inch too long!! perhaps a genetic thing

sorry for that , could not resist; YES the pre-war used 9090 9/16 by 9 in around. they must have gone on real easy. I too have been trying SBC. Up in Alaska they used to use a 9090DS ; half price from the aircraft ones; used on a dog sled.

[Guest]

Re: Bungee Life

I did get to talk to Dave Valentine at SBC today.

He described the same change in rubber stock that Jim and Bill described even the golf balls and rubber band!

He was very interested in the longevity effects that it appears to cause.

I came away with this; I am going to use 3 cords per side from now on.

The set of cords on there now consist of 2 9010HD cords about 8 months old that have probably been overstressed already and a 3rd 9010HD that I just put on there. Since 2 of the 3 have been over stressed I expect the gear to sag again in less than 2 years from now.

So by over stressed what I mean is that the "new" rubber has been subject to normal design stresses but the "new" rubber has low longevity at that stress level. I call that overstressed or over loaded.

My goal will not be to stiffen the gear but rather to unload the individual rubber bands in the cords. So next time I expect to put in more cord cross section area by putting in either more cords or thicker cords. Not sure which to chose will figure that out later.

More cords or thicker cords will make the gear stiffer and I don't want that so I think I can compensate for it by not pre-stressing the cords as much. As I understand it this translates to using a bigger loop size so the cords are not pre-stretched as much. Dave V. thought this made sense and that they do not make 9011HD for example but they could. I gotta figure how big the loop should be.

Also the pre-stretch of the cord may be overstressing them (by my definition) so that may be a second reason to make the loop bigger.

Dave V. also suggested and preferred using two 1010's. I said but they are pretty expensive. However Dave V. also mentioned that 1010's are expensive because the are rare rather than special and that buying them direct from SBC might be cheaper.

So that's my story so far.

My plane is a BC12D.

Dave