YOU CAN GET BETTER (BIGGER BUT MORE EXPENSIVE BALOONS) FROM
BANNER BALOON IN THE SEATTLE AREA FONE: 206-322-6448
ASK FOR SHEREE......THEY ARE BIGGER AND MADE OF A NON
CONDUM MATL....THEY DON'T LEAK!! AND ARE EASIER TO FILL
CONSIDER USING HYDROGEN FOR BETTER LIFT AND MUCH
CHEAPER THAN HELIUM......THIS FROM MY EXPERIENCES
IN THE 95 SEASON.....DON'T USE THEM ANYMORE CUZ THEY
NOT MUCH GOOD WHEN THE WIND BLOWS.......
QUERY RON, WA7UQV AT 206-752-7817....HE HAS YEARS OF
EXPERIENCE FLYING BALOONS FOR ANT SUPPORTS AND SELLS
BALOON KITS.......
73 DE BOB W7GG EX AI7B
----------
> From: Scott Cowling <dfi@cyberhighway.net>
> To: topband@contesting.com
> Cc: ko7v@juno.com; jwortham@goodnet.com; dana@phx.mcd.mot.com;
kb7ky@ussmot.phx.mcd.mot.com; stuart@crl.com
> Subject: TopBand: Re: Edmund balloons; questions
To: <topband@contesting.com>
> Date: Monday, December 23, 1996 10:43 PM
>
> Mark,
>
> I used an Edmund 8' balloon supported vertical in the ARRL 160M
test a few
> weeks ago. I inflated it to about 4', where I found it had plenty
of lift
> to hoist up my 129' piece of braided copper wire. I put it up on
Friday
> just before the contest and took it down on Tuesday night. By
then, it had
> deflated to approximately 2.5 ft diameter, but still had enough
lift to keep
> the wire in the air. I put it in the garage to see how long it
would stay
> inflated, and by the following Saturday it was laying on the
ground.
>
> I noticed a number of small "thin spots" on the top of the balloon
when I
> took it down. I'm not sure if they were there when it went up,
because I
> didn't inspect it immediately after it was filled. W7GNP has
suggested that
> these may be due to static discharge off the antenna. I did not
use any DC
> grounding, so I am inclined to agree with him. I'm not sure that a
DC
> ground path would even prevent static buildup at the top anyway, if
a good
> wind was blowing.
>
> I would say that a spherical shape approximates the real shape for
wind load
> calculations. The 8' balloon inflated to 4' is only very slightly
egg-shaped.
>
> As far as the bursting altitude and maximum size, I don't know.
Maybe we
> could sacrifice one and blow it up with the shop-vac until it
bursts :-) I
> won't volunteer to hold it :-)) I would say the safe inflating
size is the
> size that the balloon is sold as (i.e. 8' for the 8' model, 3' for
the 3'
> model). According to the data sheet they are made of neoprene and
are 5 mil
> thick when uninflated and stretch to 2 mils when at full volume.
At 2 mils,
> it doesn't take much to tear them! That's why I used the bigger
one and
> only inflated it to 4'.
>
> I calculated the exact lift at one point, but I use this rule of
thumb: 1 oz
> of lift per cu ft of helium. This is close enough to get you
there.
>
> I welcome any info on other sources for balloons, as I think these
are kind
> of flimsy. Any sources for mylar balloons? The mylar film is
pretty light,
> and it holds the gas in for much longer periods than rubber-types.
>
> Other details of the 1/4 wave vertical:
> The feed point was held at ~27 feet using a 3-section telescoping
mast
> bracketed to the garage. Two 129' radials were used, one to the NE
and one
> to the SW, sloping away and anchored at 6' to a block fence. The
radials
> were attached to the shield of the coax at the feedpoint, but not
to the
> mast. One of the radials was bent back along the fence (about 30')
for lack
> of space. The vertical radiator was connected directly to the
center
> conductor of the coax with no matching network. I fed it with
9913, and
> coiled about 8 turns, 10" diameter at the feed point as a RF choke.
I used
> a pulley mounted at the top of the mast and a 1/4" nylon rope to
haul the
> feedline/balun/radials up and down.
>
> It resonated at about 1830 kHz, and the SWR bandwidth was wide
enough to cover
> 1800 - 1860 kHz easily.
>
> After reading the comments on this list, I will add an RF choke to
ground to
> prevent static buildup (TNX K5AM for details).
>
> It worked REALLY well on TX; I got through on the first call with
few
> exceptions with 100W. It out-heard both my horizontal loop and
inverted L
> at 25'. But it still was NOISY on RX! (What did you expect,
right?) I was
> definitely and alligator (big mouth, no ears).
>
> Hope I didn't get to verbose, just my $.02 worth (well, maybe $.03
:-)
>
> Merry Christmas to Mark and all on the list!
>
> Scotty, WA2DFI
>
>
> At 13:56 12/23/96 -0700, you wrote:
>
> >I've been using the 3 ft Edmund balloons, with
> >moderate success - when the wind lets up. These
> >are called weather balloons, and are said to be
> >designed to burst when they reach a certain altitude.
> >I filled one to 4 ft, and it behaved much better in the
> >wind. (The lift increases by a factor of 2.37, while
> >the wind load area increases by a factor of only
> >1.78.)
> >
> >1. What is the designed bursting altitude?
> >
> >2. What is the designed bursting size?
> >
> >3. What is the safe inflating size?
> >
> >4. I also have an Edmund 8 ft balloon which I haven't
> >tried yet. I'll try inflating it to only 5 or 6 ft at first.
> >(Compared to 3 ft, at 6 ft the lift increases by a factor
> >of 8, while the wind load area increases by a factor
> >of only 4.)
> > Has anyone used these 8 ft balloons?
> >
> >5. The simple wind load area calculations ignore the
> >balloon shape. Can someone calculate the wind load
> >correctly?
> >
> >6. After 2 days aloft, a 3 ft balloon shrunk down to 2
> >ft. This is a loss of 70 % of the helium in 2 days. Is
> >that normal?
> >
> >7. Are there better balloons available?
> >
> >73,
> >
> >Mark, K5AM, DM62ni, k5am@lascruces.com
> >
> >Mark Mandelkern
> >Las Cruces, New Mexico, USA
>
> -----
>
> Scott Cowling Zephyr Engineering, Inc
> dfi@cyberhighway.net Box 27681
> (602) 784-4649 Tempe, AZ 85285-7681
>
>
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