Dereeler for hobby use

[Mika Köching]

Hi everyone!

On 9th of March I'll start in Goslar, Germany at the AATiS Kongress (Many workshops for school teachers). The building seems to only have a rather small garden so I'd like to use a dereeler.

I already tried hanging a Vaisala dereeler under the parachute but it seems to dereel way to fast and also twist up the parachute.

Does anybody have experience with dereelers?

Thanks in advance

Mika, DL8MIK

[Steve]

The de-reelers I've made have been cardboard and similar to the old  Vaisala ones.  I made them out of 1.2mm thick cardboard - scale the template below to the dimensions shown and print out - sick on the cardboard and cut out.

I suspect if you want to make these de-reel slower make the paddle bigger.  You can attach them in such a way that the cardboard falls off when fully unwound (saving a bit of weight if that is your bag).

Here is one of my dereeler flights for those who haven't seen it before: https://www.youtube.com/watch?v=_y6QHyoPFaE

I've used a couple of other types when launching commercial radio sondes - see attached pics.  I've tried to make copies of the type with the white reel without much success. Note the spool is slightly offset from the center of the disk.  I think the size is tuned to the weight of the sonde.

I find placing the dereeler under the chute makes the chute close to the balloon - too close for me (too much potential for tangling with the balloon remnants). 

    Steve G8KHW

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[Oliver de Peyer]

Pardon my ignorance but what does the de-reeler actually do?

Thanks

Ol
M0LVR

[Mika Köching]

The dereeler just holds most of the string at launch. After launch, the string will unwind. This allows for starting in limited spaces because one can just release the balloon and let go of everything at once.

My current plan is:

Balloon

    |   5m string

    |

Parachute

Unwinder

    |

    |  10m string

    |

Payload

I'd like to use the dereeler under the chute as a "hybrid" solution.

I will be launching a few small balloons (36" latex with RS41) before so I can see how the wind at ground level is.

I might try replicating the graw dereeler.

By the way: My payload is really light, only about 130g.

[Steve]

It de-reels (unwinds) letting out line as the balloon goes up - this
allows you to launch in smaller spaces and gives more control of the
balloon in windy conditions.  Without the dereeler there is quite a lot
of line between the balloon and the payload - if there is any
significant wind the balloon will be dragged down-wind - meaning you
have to run (at the speed of the wind) with the payload before releasing
- if not the payload can swing down and hit the ground.

    Steve G8KHW

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[Mika Köching]

Wondering if I could adjust the unwind-speed by blowing up the balloon from a graw style dereeler...

[Oliver de Peyer]

Thanks Steve and Mika for the explanation

On a tangent to this, I had wondered if one could overinflate the balloon for a very rapid ascent (to get it out of harm's way quickly *) and then vent it under active control until it achieves your intended ascent rate.

Oliver
M0LVR

* For astrobiological purposes, this would also help minimise contamination by getting out of the troposphere as quickly as possiblf

[Mika Köching]

Well, no. The Payload will still swing into the ground.

Also, such a device would be too heavy for my purposes though they have been built before to control the altitude of a HAB and let it float.

[Steve]

I've built and flown vents before - in order to float - letting out the exact amount of gas to get into float its tricky - but achieving a specific ascent rate might be more doable - but in my experience the ascent rate calculated from GPS can be quite noisy so you would have to average it over a fair period.

    Steve

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[f6...@free.fr]

Hi all,
the Herstmonceux weather center has not launched radiosondes since November 27, 2024.
Do you know if there is a permanent or temporary closure?
Thank you Alain F6AGV - BHAF -

[jacqueline day]

They have not had their lease renewed so assume it is that - they are looking for new premises.

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[daa...@gmail.com]

The Observarory Science center is not at the location where the Weather balloons are released. Please see map. The BBC article refers to the charity  The Observatory Science Centre https://www.bbc.co.uk/news/articles/cv2gyldl252o not the Meteorligical site

[f6...@free.fr]

Dear jacqueline day,
Thank you for your reply, know that since all these years of monitoring all the radiosondes and the recoveries without fault when possible, we highly esteem the operators of the Herstmonceux station and we wish them a lot of courage to find another site and new premises with an operational automatic cabin. It happens that the RS41s are reprogrammed by us and they are still used for meteorological measurements to learn physics with radio amateurs and school students.
Best regards from Alan F6AGV - BHAF - ( french HAB )


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De: 'jacqueline day' via UKHAS <uk...@googlegroups.com>
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Envoyé: Fri, 24 Jan 2025 19:39:19 +0100 (CET)
Objet: Re: [UKHAS] Herstmonceux meteo center no launches

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