[Discuss] Near-space balloon: Foam ball located and purchased

Kevin King EMAIL HIDDEN
Tue Nov 1 12:01:48 PDT 2011


In my research, Mylar does have an RF shielding effect, especially at microwave 
frequencies.  The Shielding could also cause RF interference inside the payload, 
since some of the RF signals would be trapped inside.  The 2M transmitter could 
cause interference with the GPS, etc...

I would think that a single small diameter steel all-thread going through the 
center should be all that would be needed.  A 1/4" all-thread with two washers 
and four nuts would add about 3.5 oz to the payload.  If the payload has been 
reinforced with fiberglass and epoxy, this would make a pretty sturdy 
container.  We could fashion some sort of wing nut on one side that would make 
the payload pretty easy to get into.

I also believe the top two thirds of the payload should be safety orange instead 
of red.  Orange would stand out better and easier to spot than red.  I have also 
noticed that most balloon examples that I have seen have some sort of "Harmless 
Radio Experiment" printed on the side with an "If found please call" notice.  We 
should make sure there is room somewhere on the payload for this notice.

-Kevin




________________________________
From: Laura Harris <EMAIL HIDDEN>
To: Ben Hallert <EMAIL HIDDEN>
Cc: "EMAIL HIDDEN" 
<EMAIL HIDDEN>
Sent: Tue, November 1, 2011 9:53:57 AM
Subject: Re: [Discuss] Near-space balloon: Foam ball located and purchased


Excellent, Ben! I have enough fiberglass cloth for at least a couple layers.



________________________________
From: Ben Hallert <EMAIL HIDDEN>
To: Laura Harris <EMAIL HIDDEN>
Cc: Thomas A Ramsey <EMAIL HIDDEN>; 
"EMAIL HIDDEN" 
<EMAIL HIDDEN>
Sent: Tuesday, November 1, 2011 9:13 AM
Subject: Re: [Discuss] Near-space balloon: Foam ball located and purchased

I have epoxy we can use plus microballoons.  For anyone who is
unfamiliar with microballoons, they're a super fine fiberglass dust
that you can mix with epoxy resin that's ideal for 'filler' projects
like this.  The epoxy doesn't really add significant strength on its
own, so having a material (like microballoons) helps a lot.  Mixed
with the resin, you can then 'smear' it onto the polystyrene.

So:
Cuts weight
+
Increases strength.
=
#winning.

- Ben



On Tue, Nov 1, 2011 at 9:01 AM, Laura Harris <EMAIL HIDDEN> wrote:
> Thanks for all the input, everyone. Ben and I will go over the various
> approaches and make some design decisions.
>
> We'll need a pair of simple  cradles to hold the halves on the workbench
> during construction and assembly- these can be as simple as a pair of sturdy
> cardboard boxes with 8" dia holes cut in one side, and edging the openings
> of the holes with something cushy like thin craft foam. If someone wants to
> fab those up and have them at the shop no later than next Sunday, that would
> be great. Otherwise, we'll throw something together on Sunday. I expect the
> ball to arrive in the next couple days so construction will be able to start
> this next weekend.
>
> I'll build a little enclosure to test the impact that gold mylar has on GPS
> performance- will have it at the shop next Sunday.
> Does anyone have any epoxy resin- not the glue, but the stuff used for
> fiberglassing? West Systems 105 is the material of choice but it's spendy-
> $45 for a quart of resin and the fast hardener + whatever shipping  costs.
>
>
> L
>
> ________________________________
> From: Thomas A Ramsey <EMAIL HIDDEN>
> To: EMAIL HIDDEN
> Sent: Monday, October 31, 2011 7:11 PM
> Subject: Re: [Discuss] Near-space balloon: Foam ball located and purchased
>
> I'm liking the nylon all-thread idea but I am a little concerned with it's
> strength. If we only have the one all-thread and it breaks our strips we
> lose the bottom half on the rig. I also don't trust velcro AT ALL. If it
> becomes wet or consistently stressed it will disconnect. Zip ties are great
> but difficult to reuse (they can in fact be reused). If we decide  against
> zip ties I propose using multiple all-threads. Perhaps three or four; one
> down the center then the others at 45 degrees from the top center straight
> (nearly so to avoid each other) through. Nylon to keep weight down. I know
> it may make for more supports to work around but we should be able to handle
> it.
>
> I really like the strobe ideas as well. If we do have a separate strobe rig
> I think it may need to be insulated as well. I've read temperatures as low
> as -60 to -70 Celsius at the altitude we expect to go and most consumer
> grade electronics like leds are only rated about -20.
>
> -Tom
>
> On Mon, 31 Oct 2011 14:35:59 -0700 (PDT), Laura Harris wrote:
>> We can use nylon all-thread for the central support rod, if we go that
>> route. Long velcro-enabled straps would be reusable and strong though
>> a bit heavier that  zipties (but not by much). If we used a net, we'd
>> still want to secure the halves together (unless you were thinking of
>> drawing the net up into a tight neck at the top . . .). I'm leaning
>> towards the nylon all thread center support rod approach, personally.
>>
>> As for the interior construction, the interior walls, floors, and
>> ribbing are 5mm foam-core. I was thinking of using gold mylar film for
>> the reflective insulation, but we can go without it and fill dead
>> areas with extra foam.
>>
>> Reasoning behind a partial hard-shell was assuming the ball will land
>> bottom down so a full shell could be avoided to save weight. Still, it
>> would definitely make it a tougher rig- more likely to survive for
>> reuse. I was thinking of using fiberglass with epoxy resin for the
>> hard shell.
>>
>> Idea  for paint scheme: paint the bottom 3rd black and the rest red.
>> Black so it is easier to see on the way up (against the sky) and red
>> so it stands out on the ground. Also, a fluorescent colored parachute.
>>
>>
>> We can use 1-watt LEDs for strobes. With the short duty cycle a strobe
>> requires, we won't need heat-sinks for the LEDs and they are bright
>> enough to be easily seen in daylight. A simple 555 timer driving a FET
>> switch is all we'd need for a driver. Another thing we can do is hang
>> a strobe from the tether. That way its weight is not considered part
>> of the 6lb payload limit (if I understand the FAA regs correctly). One
>> of those little waterproof xenon strobes doesn't weigh much, either.
>>
>> -------------------------
>> FROM: Rick Osgood
>> TO: Laura Harris
>> CC: Ben Hallert ; "EMAIL HIDDEN"
>> SENT: Monday, October 31, 2011 1:58 PM
>> SUBJECT: Re: [Discuss] Near-space balloon: Foam ball located and
>> purchased
>>
>> I just had another thought about the design of the chassis that we
>> didn't bring up at our meeting yesterday. We need to be careful about
>> the material the payload is made of as well as the GPS placement. The
>> eTrex doesn't have an external antenna so we need to make sure it can
>> get an accurate GPS lock from inside the payload. So any metal above
>> it would be a bad idea. So the chassis needs to be insulated but with
>> material that the GPS radio signals can get through.
>>
>> On Mon, Oct 31, 2011 at 1:51 PM, Rick  Osgood  wrote:
>>
>>> Ben, so your idea would be to have the cord come through the sphere
>>> via a hole in the top and then attach to the inside of the bottom
>>> half? I want to make sure I understand your idea correctly. That
>>> sounds like it could definitely work and I like that it would remove
>>> the requirement for extra reinforcement on the top half. Only
>>> downside would be having the rope going through the payload where it
>>> could get in the way of the electronics.
>>>
>>> Laura, I think the zip ties idea could be cheap, simple, and
>>> effective. It would be nice to have something that didn't require
>>> cutting and replacing the zip ties every time we open and close it
>>> though.
>>>
>>> The last balloon I did, we just had a threaded rod going all the  way
>>> through the center of the payload vertically. There was a washer and
>>> a nut on each side to hold the two pieces tightly together. Then a
>>> small horizontal hole was drilled through the threaded rod at the
>>> top so we could stick a sort of hook through it where the line was
>>> attached. The threaded rod was nice and strong but it will add more
>>> weight and then you have a metal rod going all the way through the
>>> center of the payload which can make the inside electronics layout
>>> more difficult. You can see it in some of the photos from this site:
>>> http://www.toddfun.com/2011/02/20/high-altitude-balloon-launch-2/
>>> [17] . Here is one example photo:
>>>
>>> On Mon, Oct 31, 2011 at 1:29 PM,  Laura Harris wrote:
>>>
>>>> Ohh- that looks good, Ben.
>>>>
>>>> One idea for holding the halves together is to use a pair of
>>>> extra-long nylon zip ties running longitudinally at 90 degrees to
>>>> each other- grooves formed in the surface would keep them from
>>>> sliding off. They're strong and light and they avoid the need for
>>>> any hardware.
>>>>
>>>> -------------------------
>>>> FROM: Ben Hallert
>>>> TO: Laura Harris
>>>> CC: Rick Osgood ;
>>>> "EMAIL HIDDEN [4]"
>>>> SENT: Monday, October 31, 2011 1:12 PM
>>>>
>>>>  SUBJECT: Re: [Discuss] Near-space balloon: Foam ball located and
>>>> purchased
>>>>
>>>> May I suggest that instead of attaching the cord to the top, we
>>>> run it
>>>> down and attach it to where the battery bay is? This way the whole
>>>> thing is 'sitting' on the cord and we can cut any weight created
>>>> by
>>>> reinforcements that would reach to the top of the sphere. Namely,
>>>> the
>>>> only 'strength' needed would be at the bottom where it's already
>>>> planned to exist. This also reduces risk of retrieving just the
>>>> top
>>>> of the sphere. :) I've attached a modified version of the
>>>> drawing.
>>>>
>>>> - Ben
>>>>
>>>> On Mon, Oct 31, 2011 at 12:51 P.M, Laura Harris  wrote:
>>>> > The ball comes split in half so it's just a matter of holding
>>>> it together in
>>>>> flight. I've attached a pic of a sketch showing a preliminary
>>>> idea for
>>>>> construction.
>>>>>
>>>>> ________________________________
>>>> > From: Rick Osgood
>>>>> To: Laura Harris
>>>>> Cc: "EMAIL HIDDEN [9]"
>>>> >
>>>>> Sent: Monday, October 31, 2011 10:54 AM
>>>>> Subject: Re: [Discuss] Near-space balloon: Foam ball located and
>>>> purchased
>>>> >
>>>>> Sweet! Do you plan to mold something  around the sphere? I'm
>>>> curious to see
>>>>> your final design and how we will be able to open it up and
>>>> mount
>>>>> everything.
>>>>>
>>>>> On Mon, Oct 31, 2011 at 9:53 AM, Laura Harris wrote:
>>>>>
>>>>> I found a 12" dia hollow polystyrene foam ball and purchased
>>>> one. Should be
>>>> > here in a few days. This is it:
>>>>> http://www.plasteelcorp.com/mm5/merchant.mvc [12]?
>>>>> This dramatically accelerates the build progress. :)
>>>> > L
>>>>>
>>>>>
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