Conference vmszoo::rc

    DAVEY SYSTEMS sell one.   BTW, Ted Davey is June Davey's husband;
    she's a rep out of the Blue Bell, PA Digital office!

I can't argue with family (RE:-1), but Hobby Lobby in TN has the very best
UV treated tubing anywhere.  You can buy it in 50 or 100 ft sections (can't)
remember.  No one I fly with bothers with standard/Craft Air/Airtronics
stuff anymore...

Ever since I purchased my second hi-start and the sales man warned me
to be careful that the steel stake doesn't come flying out of the ground
and kill me - I've been a little worried about it.

Soooooooooo

I found what I believe is the ideal answer.  At a local discount
department store they were selling dog run anchors.  They are aluminum
(I think) handles with a spiral stake about a 1 and a half long. 
You just screw them into the ground and they have chain link wrapped
around them.  Price $1.89 each.  Used it yesterday and today in Acton
(before the corn ends our glider flying).

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Put a second parachute on the STAKE end of the hi-start.  Then it
    doesn't matter if the stake gives; the chute will slow down/stop
    the projectile...
    	...hopefully
    
    	-Bill
    

    I am interested in a hi-start for my soon to be finished glider.
    It has a span of 3.24 m (127"). I don't have recent experiences,
    the hi-start I used to own (about 15 years back) had a rubber with
    a spun cover to protect it against the light and damage from stones.
    You could not expand it very much, the force was very high at the
    beginning and dropped very fast. Nothing for the ship I have now. 
    
    Could you glider guys give me some recommendations of hi-starts
    (with prices and sources)? Thank you very much for your support!
    
    BTW: Open area is no problem here.
    
    Regards,
             Hartmut

>    I am interested in a hi-start for my soon to be finished glider.
>    It has a span of 3.24 m (127"). I don't have recent experiences,

Hartmut for your rather large plane you want to get a heavy duty
hi-start.  Airtronics and Craft-Air (Dynaflite) both offer good ones.
Tower hobbies should carry both - be aware that with the large high
starts your talking 900 feet of open space to anchor and stretch it 
out.  Even tho you get a heavy duty (large diameter surgical tubing
and long length) that does not mean that you are going to put any more
stress on your plane than with a smaller one - just don't stretch it
so far and avoid windy days if you are concerned at first.

Most expert glider pilots own winches, the few that keep high starts
frequently find their own source for surgical tubing and get even
larger diameters - fully capable of folding wings.

I believe (you can ask tower) that the definition of heavy duty
today is 3/8" tubing 100 feet long with 400 feet of 40 pound
monofilament fish line.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

        Re:           <<< Note 207.6 by K::FISHER "Stop and Smell the Balsa!" >>>

        Hartmut,
        
                I have  the  Airtronics  "heavy"-duty  hi-start.  It will
        pull a light  glider  up quite well, but I definitely plan to buy
        new rubber to get more power, even for my Riser and Oly II, which
        are real floaters.  I already changed the monofilament to braided
        icefishing line.  My advice would  be  that if you are willing to
        pay $40 for a reel, then any  hi-start  will  do, because you are
        bound to replace the rubber and line.   If you can make a reel up
        yourself, I suggest you forget about commercial hi-starts.
        
                      _ 
                     / |
        |  _====____/==|
        |-/____________|
        |    |        o \
             O           \ 
                          O
         Hang in there! o_|_
                          |
             Anker      \_|_/

    Thanks for the advice so far. A reel is no problem, even the line
    and the chute is no problem, the thing I'm most unsure about is
    the rubber. There are a few sources here in Germany, and I don't
    trust them very much. If you can give me some more advice on the
    rubber (squared or round cross-section? tubing? what sizes?), it
    would be of great help. Anker, what do you mean to get 'more power'
    for your Riser and Oly II, is it a longer or a thicker rubber or
    different material?
    
    If you can, please give me sources and prices (~), too. If I can
    do better than with the stock Hi-starts, I'm very interested.
    
    Thanks and regards,
                        Hartmut

        Re:                    <<< Note 207.8 by KBOMFG::KLINGENBERG >>>

        Hartmut,
        
                What you  need  is sugical tubing, which I assume doctors
        use to tie  around  limbs as a turniquet.  It comes in a bunch of
        different sizes and I  am not sure what.  I plan to go to a place
        called Cambridge Rubber and pick  one  that  looks right compared
        with my old hi-start.  By power I  mean  more  oomf - harder pull
        and longer stretch.  I will probably go to  125'  from  the 100 I
        have now.
        
                Dave  Walter gave me some specifications.  I'll see if  I
        can  dig  them  out,  otherwise  you  may  want  to  mail him  at
        HPSTEK::
                      _ 
                     / |
        |  _====____/==|
        |-/____________|
        |    |        o \
             O           \ 
                          O
         Hang in there! o_|_
                          |
             Anker      \_|_/

    I noticed an advertisement for a Hochstartgeraet on page 58 of the 
    8/89 issue of Flug und Modelltecnnik.  It seems that they use
    rubber from the US.  The rubber dimensions are 30 m by 8x1.5, 10x2.3,
    and 12x3 mm; I assume those are the outside_diameter x wall_thickness
    dimensions.  The diameters one would use in the US would be (approx.)
    5/16, 3/8, and 1/2; the rubber prices (in Tower's full catalog for 
    black natural latex from Off-the-Ground) are $32, $39, and unknown,
    respectively.  The prices for Dynaflite rubber are higher, but the
    dimensions are not mentioned.  The Airtronics rubber is not listed
    separately.  Last year's Hobby Lobby catalog lists rubber at $39,
    unknown, and $43.  The 1989 Sheldon catalog lists the Dynaflite
    rubber at $27 and $30 and Airtronics tubing at $24.  All of these
    prices are without shipping and "handling" charges that are added
    separately.  Some of these products are listed as resistant to UV.
    
    If one were to go to a hospital supply store (not a pharmacy), what
    would be the prices?  The quality?  The UV resistance?

    Remember guys, its not so much the size of the glider but what does
    the thing weigh?  I have somewhere at home a add for a company that
    will make high starts up based on your glider.  Most of their stuff is
    not using surgical tubing but uses bungie type material, this has the
    lots of little rubber bands encased in a fabric shell.  Now keep in
    mind that these are not cheap either, for a high start for a big heavy
    glider it will cost around $80.00 if I remember right.
    
    I will try to dig up the add for them and post the results...

Let me clarify a point I was trying to make about the high start.
I am not advocating that someone with a new glider makes
20 hand launches and then starts with just a few feet of high start
stretch.  

I am advocating that someone who has never flown a glider before
(but has learned power planes (Ajai are you listening)) take 20
hand launches.  Don't try to fly it back to yourself until you have
attained the confidence to do so (you will in twenty launches).
Don't worry about landing down wind because you will only do this on a 
dead calm day.

Now for those wimpy high start launches.  The reason you only want
to stretch it out 10 feet, then 20 feet, then 30 feet, etc. is because
you will be scared to death of the high start.  If you think of it as
a hand launch except you just add a little boost then you will have
no fear of even your first launch.

For your second glider you will only need a few hand launches and will
want to use a full high start or winch to launch the first time.

I agree with Dave that if an expert is available to run the winch
for you there is no reason to avoid it.

Now a word of warning about higher performance gliders (metric's and up).
It may not be possible or practical to hand launch.  I can't throw my
Sagitta fast enough or hard enough to do safe hand launches.  Well I can
now but I couldn't when it really needed it's first trimming flight.
So what to do?  Find a hill and throw it down the hill.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    I'm probably asking a question that, if I went out and bought a
    high start I'd get the answer in the instructions but, how far
    do you streatch a high start?????? Is there a specific distance,
    or do you just keep walking until you "feel" the tension is high
    enough. I'm talking about a standard high start here. Not a big
    heavy duty one, and not an up start.
    
    Steve

I pull it back until it breaks and then I move in a couple of steps...

Actually, the hi-start will tell you it was too far by breaking, the plane will 
tell you it was too much by folding the wings and more importantly, the plane 
will tell you it wasn't enough by stalling out in the climb. 

It's really a matter of "feel". Just make sure it's pulling enough to get the 
glider up and maintain the speed. There isn't really any fixed length because 
it greatly depends on the strength/condition of the rubber.

Most surgical rubber in a high start can be stretched to over 6 times its 
length, there is no gain in strength past 3 times.  So if you have a high 
start that contains say 100 feet of rubber and 450 feet of braided line the max
strength would be attained by stretching it back 300 feet so the total length 
from anchor point to the airplane when ready to launch would be:

100' rubber
450' line
300' additional rubber stretched out
------
850'  total

Get the idea, lay the high start out under no tension and then walk it back
3 times the length of the rubber.  This rull applies to all Surgical tubing
based hi-starts.

Use less stretch if you need to but there is no gain in stretching it out 
longer than 3 times the rubber length.

    Steve, 
    
    reading your question I assume you haven't done any histart so far ?  
    In this case I strongly recomment to go with an instructor or at least 
    with any other experienced RC glider pilot. My experience told me you
    could get into trouble real fast. 
    
    
                      \\
                       \ \                    __
                        \  \                  \ \
                         \  \                  \ \
                          \  \                / \_\
                           \  \              /LO |
		       .o^^^--------==========___/
		      <      \  \-''
		       '-___-'\  \            
			       \  \
                                \  \          Holm- und Rippenbruch,
                                 \ \
                                  \\                          Bernd

    I would like to compile a list of all of the manufacturers of
    Hi-Starts..  I know of
    
    	Airtronics
    	Dynaflite
    	Hobby Lobby
    
    Are there others??  I have the airtronics one..  If you have one of the
    other ones, could you mention that as well??
    
    I'm actually curious about whether they all use the same take up reels
    or not.
    
    thanks,
    jeff
    

    For the roll your own guys:
    
    Lone Star Models
    1623 57th St.
    Lubbock TX 79412
    Ph (806) 745-6394
    
    Lists in their 11/1/90 catalogue
    
    Hi Start tubing		50'		100'
     ID    wall    OD
    1/8  x 3/64 x 7/32		$17.95		$26.95
    1/8  x 1/16 x 1/4		$18.95		$29.95
    3/16 x 3/64 x 9/32		$18.95		$29.95
    3/16 x 1/16 x 5/16		$18.95		$29.95
    
    Usual disclaimers - I haven't purchased any (yet ;^)
    
    They also list 1/32" wall surgical tubing in 1/16, 1/8, 5/32, 3/16, 1/4
    inch inside diameters in 10 (1/4 = $5.35, others $4.95) and 50 (1/4 =
    $19.75, others $18.50) foot rolls. This tubing is listed separately
    from the Hi Start rubber.

    I've used the 1/8th inch stuff on HLS size planes and it works pretty
    well. Once you get into the 2 lb range it really wimps out half way up
    unless you have a reasonable breeze to keep it stretched. We've
    recently been using a heavy duty Dyna-flite upstart (which is light
    3/16" tubing) with an additional 25' of heavier 3/16" tubing I bought
    at a surgical supply house. This has flown my 36oz Gentle Lady
    (w/flaps) and Dan Miner's Oly II without any problems on a recent
    relatively calm day. The 1/8th inch stuff only seems to last a season.
    
    I've got a question about tubing care. Long time ago, free flight
    rubber was coated with dish soap to cut down on oxidation and increase
    the possible number of winds (don't ask how I know this ;^). Is there
    anything we can be coating the hi start tubing with that will extend
    it's life and keep it flexible?

    Two more hi-start sources:
    
    Magnum Hi-Start; C & D Enterprise
    5102 E. Andora Dr.
    Scottsdale, AZ.
    602-996-1021
    
    Three models, light, medium, heavy..$70 to $85.
    
    
    Pinnacle Hi-Start; NorthEast Sailplane Products
    16 Kirby Lane
    Williston. VT. 05495
    802-658-9482
    
    one model, $70.
    
    
    I've used the Hobby Lobby medium and heavy rubber. It's good but
    rather prone to abrasions if you don't fly from grass fields.
    The heavy tubing is for real gorilla launching, if your plane doesn't
    weigh 70+ oz. you don't need it.
    
    
    Speaking of launching devices, last weekend one of our club members
    brought his new Rahm winch and retriever to the field. He had it
    mounted on a Sears utility cart with fold out platforms for mounting
    the winch and retriever motors, and a box platform in the center
    for the operator to sit.
    We could zing planes up every thirty seconds, and the whole setup
    is pretty fool proof as long as you make sure the retriever line
    is not hung on something when you launch. If it gets hooked, then
    the tow line is yanked off the hook two seconds after launch, and
    the mother of all line snarls sometimes follows.
    $ 300 for winch, $250 for retriever.
    
    Terry

>    Typo police, typo police

Anybody know what Jim is talking about?

>    the possible number of winds (don't ask how I know this ;^). Is there
>    anything we can be coating the hi start tubing with that will extend
>    it's life and keep it flexible?

The documentation for either my Airtronics Hi-Start or my Dynaflite Upstart
said to use "Baby Powder".  I did a couple of times when I knew I was putting
it away for the winter.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    The white stuff on the rubber is wax that gets worked out of the rubber
    from stretching. Is there as method of replacing this wax?

    I don't know of any practical way to replace the wax, but I've had
    good luck with Armor-All as a rubber preservative. Just make sure
    to wipe the hi-start down well after application to avoid picking
    up dirt. I fly in an intense U.V., hot sunlight environment and
    never have trouble with rubber cracking or rot. 
    Nicks, cuts, and abrasions are another matter though.
    
    Terry

    Just a point for those central Mass hi start owners. I was in Spag's on
    friday and happened to notice that they had the 150' extension cord
    reels on sale. These are the 12" diameter reels with the center
    handhold and crank. Dave Walter has one. $3.88 at the main store in the
    tool section out front (main isle before you cross into the back) or
    $4.44 in the olde school house (same reel, different building)

	Just as a point of interest, I saw the large highstart that Northeast
	Sailplane Products is selling for about $70. Peter Monroe had it at
	the CRRC field this weekend. It uses 100' of mongo rubber, at least
	1/2" diameter, and 300' of orange high visibility line which appeared
	to be pretty heavy, more like winch line. It comes on one of those
	hose reels like the one Jim described in the previous reply.

	Peter told me this highstart is advertised for 2M planes on up, but
	I think it's too strong for 2M, especially if there's a good wind. 
	You just can't pull it out far enough to get a good launch with a 
	light plane.

	Now that I think of it, it looked a lot like Kay's new highstart he
	got for his Lovesong. Did you get that at NSP, Kay?

	Dave

>	Now that I think of it, it looked a lot like Kay's new highstart he
>	got for his Lovesong. Did you get that at NSP, Kay?

Yes.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    I happened to measure the pull of my hi-start at my typical launch
    point for the Chuperosa.  It measured ten pounds on an old fishing type
    spring scale.  Not as much as I had thought.

    A quick calculation yields 1000 foot pounds for the stored energy
    (forgive me, Ajai).  That is consistent with a launch height of a
    couple hundred feet of a 1.25 pound plane --- 25% efficiency.  The 
    8:1 thrust to weight ratio explains the acceleration.  It moves!

    It's probably just as well that the amount of stretch available
    within the confines of a dormitory room doesn't allow them to exploit
    the full potential of surgical tubing.
    It would be interesting to see a slow-motion tape of the balloon
    distortion during launch.
    I'd hate to get hit up 'long side the haid by one.
    
    Speaking of hi-starts, last weekend several us Legend fliers
    were at the sod farm without a winch.
    I brought my gonzo red rubber hi-start, the heaviest that Hobby
    Lobby sells. It's still nearly brand new after several years
    because it's such a task to use it and most of my planes don't
    need that kind of launch power, or I use a winch.
    
    Into the wind, it was giving quite adequate launches to the Legends
    but none of the other planes (2 meterS and Southwinds) dared to
    use it. Down wind it still isn't as good as a winch.
    
    During the last 25% of the stretch you pray that you don't stumble
    and get dragged screaming down field. Then someone has to hold it
    for you and launch, or if you do it yourself you've got ~10
    seconds to release before your arm gives out.
    And of course everyone is constantly complaining, "what the @#&*%!,
    have you got on the other end of this line ?"
    
    Terry

Just another trivia........

When stretching the highstart, take the amount of rubber and times it by
3 and that is how far you can stretch it for maximum efficiency, you can stretch
it as much as 600% or 6 times but you dont gain any extra force.

So if you highstart has 50' of rubber, walk back until it start's to stretch and
then walkback 150'

The theory I always use is to keep walking back until you believe that on the
next step either the stack is going to pull out of the ground or your tow
hook is going to straighten out, then thats about right!

I'd like to see one of them bungie style highstarts, "Here Joe hold onto this
highstart for a second for me"....HEE HEE   Yowwwwwwwwwwwwwww

re Note 423.35 by NEURON::ANTRY  -< 300 x's best max 600 x's >-
    
>>  When stretching the highstart, take the amount of rubber and times it by
>>  3 and that is how far you can stretch it for maximum efficiency, you can 
>>  stretch it as much as 600% or 6 times but you don't gain any extra force.
    
    It seems to me that from 3X to 6X it has exactly the behavior you want. 
    You would gain extra energy without extra stress on the airframe.  Did
    you really mean to say "maximum efficiency"?

To semi-quote the liturature (I think it came with my Up-start that I cant 
find anymore, I wish it would come home)  Surgical tubing can be stretched up
to 600% it's original lenght although maximum force is at 300%, so stretch it 
back 3 times and thats as good as it gets, you could stretch it up to 6 times 
but it doesnt get you anything except two pieces of highstart out of one if 
you go too far.  So a rule of thumb, take the amount of rubber you have in your
highstart, lay it out, when walking back, the momement the rubber starts to
stretch, walk back 3x's the lenght of the rubber (50' x 3 = 150') and thats
where you'll get maximum launches.....

Hope that cleared things up and sorry about mixing the x's and the % when using
the wrong numbers (ie should be 3x's and not 300x's)

    I've read this before also, but I don't understand it either. 
    
              |          , ............
              |      '                .
       Force  |  ,'                   .
              |,'                     .
              +----------------------------------
               0  1x  2x  3x  4x  5x  6x
                      Stretch
    
    If you stretch a highstart out 3x and let it go, the force starts 
    dropping immediately.
    
    If the force is linear from 3x to 6x, then you could stretch it out
    to 6x and have a steady force applied for the first 3x contraction 
    before it the force diminishes.
    
    Isn't the maximum launch not only a function of peak force but also the
    amount of time the force is applied?

Boy I dont know, but I'm sure some of the buldging brains in here will
psycoanalyze your new question....


Boy I dont know you bring up a good point....

    The assumption is that the force is linear from 3x to 6x. Is this
    really the case ?
    
    Also, I've never had a hi-start that could be stretched to 6x, not
    that I've tried it; but at ~3x my medium size rubber feels plenty
    tight. I might get 4x out of it, but 6x I can't believe.
    
    With thin wall tubing it might be possible, for a short time.
    
    Think back to your last hi-start stretch, and assuming each stride
    is ~ 3 ft. and you have 100 ft. of rubber, do you routinely take
    200 steps after you first feel tension ? If so then my hat's off
    to you. I call it quits at 100-120 paces with my medium rubber and
    75 paces with the heavy stuff.
    
    Terry
    

>               <<< Note 423.42 by CIM::LOREN "I <heart> OOPS" >>>
>
>    I've read this before also, but I don't understand it either. 
>    
>              |          , ............
>              |      '                .
>       Force  |  ,'                   .
>              |,'                     .
>              +----------------------------------
>               0  1x  2x  3x  4x  5x  6x
>                      Stretch
...    
>    Isn't the maximum launch not only a function of peak force but also the
>    amount of time the force is applied?

Of course it is.  It's the same theory behind a compound bow - but
I disagree on the assumption that the force levels out.  In my experience
it pulls pretty steady for the first 2/3's of your stretch then it starts
to ramp up to where either the tube breaks or you obviously reach the
end of the stretch.  At that point I usually back off a few paces for
one of two reasons.  On my smaller hi-starts I worry that the darn tubing
is about to break, on my larger (Lovesong size) hi-start I can't hold
it very long at the hi tension.

Anyway my picture based on empirical feel but no fish scales looks more like
this.

>              |                    ,
>              |                    ,
>              |                  ,'    
>       Force  |  ,--------------'       
>              |,'                    
>              +----------------------------------
>               0  1x  2x  3x  4x  5x  6x
>                      Stretch

My Airtronics hi-start directions said to stretch it 4 to 5 times it's length.
I found it bottomed out at 4.  My up-start probably made it to 5.  My
big hi-start probably only gets to 3 or 3.5.  It seems like the max stretch
decreases with the diameter (and thickness) of the tubing.

Like most things in life here is how you figure out the right way.  Stretch
it till it breaks then back off one pace :-)

Anyway the energy you put into your plane during launch (not counting the
wind and kite effect) is proportional to the area under the curve and that
is proportional to the work you expend pulling it back.

P.S.  I retired two hi-starts this year because they were old and brittle
      and kept breaking on me.  You could argue that I shortened their life
      by overstretching - but they lasted about 3 years.  And I even washed
      them and packed them in Baby Power - as per directions.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Well, there's only one solution I can see...
    
    Send Al out in the back forty again.
    
    Since you love the technical nits and started this with your fish
    scale... could you take it out in the back again and give us a series
    of datapoints (like one every two paces or so) and settle this for us.
    Just let us know the length of your rubber in paces and measure the
    pull out to where you're comfortable and then walk it back in and
    double check the relaxation pull as you go. Given a fish scale, I'd be
    willing to check mine also.

    OK, back to the field for some data after:
    
    1	the Chup is repaired (broken by an expert [not me!] last Tuesday)
    
    2	I have a calm morning to minimize the variables
    
    3	I put sandpaper on the sides.  (The combination of my skin against 
    	the Oracover plus the delicate structure of the Chup makes a ten pound 
    	pull about all that I trust.)
    
    4	I get back from Rhinebeck and recover from our contest 9/14
    
    I'll put the watch into the Chup and try to be consistent in technique.
    	
    Alton and his [old dairy cow milk production] scale 

    Al, 
    
    Although I'd love to send you out to go flying for science 8^) My
    suggestion is simpler. I just want you to hook up the scale to the
    hi-start and plot the pull of the rubber over the distance pulled so we
    have datapoints to match the plateau'd curve drawn in the previous
    notes. I'm not personally convinced that it plateaus off. Then the
    energy in the system is the area under the curve (which is increasing
    unless the rubber suddenly starts pushing you so it goes negative)
    
    So my proposed experiment is to take the fish scale and hi-start out
    and plot the pull every few paces. While the altitude under various
    pulls would be interesting, I'm pretty sure there's too many variables
    (release point is a biggy) to be worthwhile.

>   <<< Note 423.48 by ZENDIA::REITH "Jim Reith DTN 226-6102 - LTN2-1/F02" >>>
>              -< Just one pull of the rubber is needed/measured >-

I agree with Jim.  But I must admit I would like to hear
the results of the watch measurements.

P.S.  Started a new Chup wing last night - I'm really excited about this.
      Nothing wrong with the old one but...
      I cut up a piece of foam last night to be a jig for an elliptical
      wing and started warping spars on it - awsome.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

                Interesting discussion!
        
                I bought one of the new Northeast Sailplane hight starts,
        the second largest,  for  my  Legend  and  stretched  it  out  my
        standard 100+ paces.   At that point it would pull so har I could
        hardly hold on to the  plane,  but on the launch it would run out
        of oomph about 2/3 of the  way  up.    It  turned  out  I  wasn't
        stretching it enough, it needs to be  stretched  about  130 paces
        for a complete launch.  I'm going to  test  stretch a piece of it
        and check the % it will stretch and then  try  it  on  a  launch,
        being careful not to launch myself.
        
        Anker

    The heavy hi-start (3/16" wall thickness) that I never used until
    I started flying the Legend, is gradually getting broken in.
    
    Initially, 60 paces felt awfully tight now I can routinely go
    75 paces and 85 is not too bad. BUT now the fishing leader/swivels
    are not up to the task so will have to put heavier ones on. 
    
    Also, the 50# line feels a little marginal now although I haven't
    broken it yet.
    
    After heavier swivels and line I think I can approach 100 paces.
    Can't imagine getting 130. But the launches at 75-85 paces are very
    acceptable as long as I've got a little head wind.
    
    Terry

    Those who have read Frank Deis's second article on catapulting (in the
    9/91 issue of RCSD, page 24) will understand that I have found a
    kindred spirit in the rockies.

    In support of his calculations he measured the stretch characteristics
    of a hi-start rubber he happened to have handy.  Using a fish scale he
    measured a one-foot piece of a "medium strength Magnum High Start"
    rubber.  It took 8 pounds per foot of stretch for the first three feet. 
    e.g.
              length          force

                  L             zero
                2 L             8 lbs
                3 L            16 lbs
                4 L            24 lbs

    "Stretching it more than this gives non-linear results and eventually
    breaks the rubber!"  (But he doesn't say how hard to pull to break it.)

    So for this particular hi-start, if you have one hundred feet of
    rubber, stretch the hi-start up to one hundred yards beyond the relaxed
    length.  This is the same advice Mark Antry gave a year ago (423.16)
    and repeated early this month (423.35).  In note 423.50 Anker said that
    he stretched his hi-start 130 paces.  He probably has one hundred feet
    of rubber, and at 2.5 feet per step this stretch would be 4.25 L.

    Anyway, back to the article by Deis.  He was doing this calculation to
    figure what it would take to get a speed of
    

    415 miles per hour off the launch!

    More than two years and several replies of this note back, we were
    discussing what hi-start to get for my Fiesta. I settled with the
    Magnum 100 and was very happy with it.
    
    Recently, a friend talked me into selling the rubber to him. Since I
    could easily replace it here, I (fool) did it.
    
    I just called Magnum to find out they went out of business. Who's doing
    hi-starts today that are comparable (quality-wise)? I only need the
    rubber. It should be able to get 100"/5lbs planes up.
    
    Best regards,
                  Hartmut

Northeast Sailplane Products has a nice line of hi-starts. Kay has one of 
their heavy duty ones that you might want to try before you buy. Green Rubber 
company in Cambridge MA is where we bought the last batch of rubber. You can 
get any diameter and wall thickness you want.

    Of course, I've seen these in the catalog (you know, the one under my
    pillow since Saturday...).
    
    Do you know whether NSP will sell rubber only? Yeah, I know, I should
    call Sal myself.
    
    Cambridge rubber sounds good. I only have no idea what dimensions I'm
    looking for. After all, I don't care about dimensions, all I need is
    umphhhhh.
    
    Will try to get the dimensions from the buddy I sold my hi-start rubber 
    to.
    
    Best regards,
                  Hartmut

The last rubber we bought from Green Rubber company was 3/16" inside diameter 
with 3/32" wall thickness. I'd probably go with 1/8" wall if I were to buy 
more in the future. I don't know where the place is since I had a friend pick 
it up for me. I think Sal would sell just the rubber. They put the hi-starts 
together themselves from different pieces/vendors.

    I don't recall the exact address of the Green Rubber Company, but it's
    just a couple blocks away from the Court House in Cambridge. And it
    does mostly wholesale business, so don't expect a glitzy showroom with
    pristine rubber hanging in display cases. Expect a fat guy with a cigar
    to drag you over shipping materials and wooden skids to let you pick
    through his inventory.
    
    They are probably the best source of rubber around. The stuff I bought
    from them 3 years ago finally gave up the ghost, but it gave me 3
    seasons of good performance.
    
    Dave

    You used the same rubber for THREE YEARS??????????
    
    WOW!!!!!!!!
    
    Steve

    Hey, it was the only one I could find that was long enough...

But it took you 3 years to wear it out?

>    Do you know whether NSP will sell rubber only? Yeah, I know, I should
>    call Sal myself.
    
Do yourself a favor and get the whole hi-start from Sal.  The orange line
and the super nice parachute and good swivels and solid rings make the package
worth the trip.

>    Cambridge rubber sounds good. I only have no idea what dimensions I'm

I'm surprised to hear Dave got 3 years out of his.  I purchased a chunk of Dave's
supply and I only got 6 months out of it before it rotted - it's all probably 
in how much you over stretch it and how much you let it lay in the hot sun and...

NSP hi-starts are a bargain in the long run.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    Kay,
    
    it probably depends on the price. I bought a very nice Magnum hi-start
    2 years ago and only really used it once or twice. Now a friend talked
    me into selling him the rubber only and I gave in, assuming I'd be able
    to replace it here. The line, the reel, the chute, rings etc is all
    still at home and in very good shape. Unless the chute is A LOT better
    than the Magnum (I'm not impressed with that one), I'm not really
    interested in buying a complete new hi-start. Now if the rubber is only
    10 $ than all the rest, it's a different story...

    Could I maybe check yours out before calling and ordering? I'll probably
    be pretty much tied up the next 2 or 3 weeks, but I only need it before
    I leave, and that's still some time to go.
    
    I'll give Sal a call and remind him of the great flight I timed for him
    :-). I'll wait until I figure out what else I might want to get from
    him.
    
    Thanks for all the inputs.
    
    Best regards,
                  Hartmut
    
    P.S.: Now one more question: If I want to get some hand-launch glider
    fun at home before developing a gorilla arm - what kind of up- or
    hi-start would you recommend here? NSPs up-start again? How long a
    rubber and line is on there?

    > I'm surprised to hear Dave got 3 years out of his.  I purchased a chunk
    > of Dave's supply and I only got 6 months out of it before it rotted -
    > it's all probably  in how much you over stretch it and how much you let
    > it lay in the hot sun and...
    
    Are you sure about that Kay? I seem to remember selling you a length of
    rubber which you used to REPLACE the stuff that rotted. I have a piece
    of that same rubber on my small high start, I've used it since before I
    sold you the length, and it's still in fine shape. Do you store this
    stuff in a vat of acid or something???

    
    
    Does anybody know of a supplier of top quality surgical tube here in
    the U.K. at sensible prices?
    
    Richard