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2705Re: [GPSL] FAR 101 Line Strength

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  • Brek Brixius
    Oct 2, 2006
    • 0 Attachment
      Zack:  Could you please explain what it means to fly exempt?
       
      Pardon me if this sounds like a dumb question.  I have a lot of dumb questions.  I would rather ask them and learn than remain ignorant.  I want to construct a balloon that meets all the regs and will be safe and successful and not harm anyone or anything.  If it takes more time or money, fine. 
       
      I am wanting to be ready to fly my balloon at GPSL 2007.  I have a long ways to go to meet that goal.  I really appreciate everyone's help and input.
       
      Even though I am a long way from completion, the balloon project has been great fun.  I've learned a lot about electronics, acquired an new hobby (Kite Aerial Photography) and taken tons of photos of everything from dirt to the sun. I have earned an amateur radio license and so has my wife.  I have used a temperature logger I bought for the balloon to graph the overnight low temperature in my pumpkin patch and I learned more about how plants react to cold.  Even if I stop now, I think it has been well worth my time.
       
      But I don't want to stop.  I want that photo of from the top shelf.  So look for me at GPSL 2007. :)
       
      One more thought I have about line strength is, these products list a test weight - say 50#.  To me that says, the product (or a sample of it) was tested at 50# and did not break.  I used to work for a factory that produced a product that was 100% tested and the certified test rating was approx. 1/3 of what nearly all of the product would actually endure before failure.  I don't know exactly why they set the test ratings where they did.  It would make sense to do so as insurance against failure.  You can't sell product that failed the test.  So you can't afford to have product fail the test.  A failed test might endanger your workers or damage your equipment.  The amount that the product will take over test is insurance against law suits.  If your product routinely performs to the limits of its spec. you get a reputation for delivering a quality product and you can charge more for it.  For whatever reasons, I suspect line/cord manufacturers may also state a test rating that is low.
       
      Brek.
       
       

      Zack Clobes <zclobes@...> wrote:
      We've always flown "exempt", which we read to mean that your load-line must break with 50 pounds of force.  Unfortunately they don't really specify what that force is.

      I don't think that a balloon would stand a chance if it got snagged up on a jet - it'd rip it to shreds.

      However, on a single-engine light plane, I'm not so sure that the balloon would rip apart.  I've seen some of those envelopes take quite a beating on the ground and during lift-off.  In a worst-case scenario, I think I small Cessna or the like could probably take a flight string for a ride, and I'm not sure that the landing would be very graceful.  Catching a balloon on the wing would add a lot of additional drag and severe yaw to the flight, that may not be controllable throughout landing.

      We've flowing 50lbs test line on ALL flights.  And we have actually had a failure.

      During a winter morning launch in about 20mph wind, I had tied up a 50lbs "weak link" in the load line.  It was the same mono-filament string that we had used on nearly a half-dozen other flights with no problems, but for some reason in the 25F, brisk morning wind, the line became extremely brittle - it was literally crumbling in our hands.  We tried re-tyeing it and launching, but the balloon snapped away and left the payload on the ground.

      At that point, we switched to Kevlar "Spider Wire" for our link, and have not had a failure since.

      We actually flew mono-filament, paralleled by Kevlar for several flights after the failure until we became comfortable with the new line.  None of the mono-filament ever failed again.  The only thing I can attribute the one-time brittleness to was that it must have come in contact with some chemical while it was being prepped for flight.  The same reel has/had been used for 7+ flights, had been used as guy-wires on my HF mobile antenna for 3+ years, etc. 



      My opinion, don't try to bend the rules to save a few bucks or a few minutes. 

      Zack Clobes, W0ZC
      Project: Traveler

      PAUL VERHAGE wrote:
      As I recall, it's the breaking strength between the balloon and line
      that must be 50 pounds. I don't know over what area it must be applied,
      but I would think the balloon nozzle will shear off with 50 pounds of
      force.

      Paul

      >>> "Holmes, Will" <wlholmes@taylor. edu> 9/29/2006 8:53 pm >>>
      You mentioned 110 pound kite string, and that made me think of
      something I have been wondering about for a while. FAR 101 states has
      something about the test strength of string connecting packages. I
      believe the strength it states is 50 pound test.

      How do the different groups interpret this and what do you use?

      Will Holmes
      Taylor University


      ____________ _________ _________ __

      From: GPSL@yahoogroups. com on behalf of Brek Brixius
      Sent: Fri 9/29/2006 9:33 PM
      To: GPSL@yahoogroups. com
      Subject: [GPSL] I'm a HAM!

      Last Sunday I took the technician exam. I am now Brek KC0YOE. My wife
      had been listening to me as I studied. I read out loud to improve
      retention. She decided she had listened well enough that she wanted to
      take the test as well. She is now Angela KC0YOF. :)

      When I'm read then I can start working on the balloon tracking system.
      Recently I have been flying one of my cameras from a kite. I have 7
      foot delta conyne. Some of the KAP sites recommend a bigger kite. In
      winds like we had today, the 7 footer is big enough.

      My line was humming like something from a sci-fi movie. Towards dusk a
      couple of bats came out and flew around the line for several minutes.
      That was fun to see.

      By the way, I have a bunch of 110 pound dacron kite string. Is it any
      good fo r the balloon or what sort of line do I need?

      Brek.


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