Many people recommend Bricklink as a source of LEGO parts.

According to the Mission Model element overview, the part number for the
string is 4297719, which the Bricklink catalog identifies as "String, Cord
Thin"

http://www.bricklink.com/catalogList.asp?q=4297719

I'm not familiar enough with types of string to speculate on how well they
would serve as replacements.  For best comparison to the zip line that your
team will encounter at a tournament, I would recommend using LEGO string.

Steve Scherr
VA/DC FLL Referee Advisor


On Sun, Sep 8, 2013 at 12:12 PM, Barry Moses <[log in to unmask]> wrote:

> As a follow on question, one of my kids cut the line because they thought
> it was too long.  It wasn't.  What line can we replace the zip line with?
> Right now one of our sponsors is comparing the line to his woven fishing
> line.  We found dental floss to be a poor substitute.
>
> Thanks,
>
> Barry
>
>   *From:* Stephen Scherr <[log in to unmask]>
> *To:* [log in to unmask]
> *Sent:* Friday, September 6, 2013 6:02 PM
> *Subject:* Re: [VADCFLL-L] Taking care of the zip line at FLL tournaments
> (and general Field Maintenance)
>
>  The Field Setup instructions specify the attachment and the tension for
> the zip line.
>
> It's on page 11 of the Challenge PDF, in the section about the Cargo
> Plane, under the 3 close-up pictures:
>
> Put the hook end of the string through the plane’s trolley from nose to
> tail, and hook onto the hitch bar, and latch the plane to the tower. If the
> string is not parallel to the runway, you can pull the tower’s Dual Lock
> apart, move the tower a little as needed, and then press it on again.
> Finally, use the thumb-gear at the arrival end to put tension on the string
> until the cantilever (tire/arm weight) sits mostly level.
>
> At tournaments, we will adjust the tension so that the cantilever sits
> mostly level.
>
> I have not had a chance yet to set up this model on an actual table (but I
> am looking forward to doing it this week), so I cannot comment from
> personal experience about how close the cantilever will be to level.
>  Having built several kits, I know that the total length of the string will
> vary slightly, due to where knots are tied, and stretching of the string
> over time.
>
> There are several items on an FLL field that vary slightly during the
> season.  During the practice season, teams may run robots a lot on the mats
> and with the mission models.  New mats and kits will behave slightly
> differently than "experienced" mats and kits--a little dirt gets worn in,
> string will stretch, dual-locked models may get knocked into, mat folds may
> relax and get lower, etc.  Some of the experienced coaches on this email
> list can provide tips along these lines.
>
> Tournament kits are new for the early season tournaments and get more
> "experienced" for the later tournaments.  We follow the directions in the
> Field Setup between tournament rounds or after a bunch of matches:
>
> "Mission Models - Keep the models in original condition by straightening
> and tightening solid connections often. Ensure that spinning axles spin
> freely by checking for end-to-end play and replacing any that are bent."
>
> Steve Scherr
> VA/DC FLL Referee Advisor
>
> On Fri, Sep 6, 2013 at 5:21 PM, Bdh612-ess <[log in to unmask]> wrote:
>
>  The setup instructions never specify what the tension is supposed to be
> (I never found how the string is even supposed to be attached). How will it
> be done at tournaments? I want the kids to be practicing with the right
> setup.
>
> Brian
> Waterford Robotics
>
> Sent from my iPhone
>
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